QM 2022

4 Apr 2022, 08:00 → 10 Apr 2022, 14:30 Europe/Warsaw

Auditorium Maximum UJ

Wojciech Florkowski (Institute of nuclear Physics, Krakow), Krzysztof Redlich (University of Wroclaw), Barbara Krystyna Wosiek (Institute of Nuclear Physics Polish Academy of Sciences (PL))

APRIL 4-10, 2022, KRAKÓW, POLAND 

Quark Matter 2022 is the XXIXth International Conference on Ultra-relativistic Nucleus-Nucleus Collisions. This conference brings together theoretical and experimental physicists from around the world to discuss new developments in high energy heavy ion physics. The focus of the discussions is on the fundamental understanding of strongly-interacting matter at extreme conditions, as formed in ultra-relativistic nucleus-nucleus collisions, as well as on emergent QCD phenomena in high-multiplicity proton-proton and proton-nucleus collisions.

Honorary patronage: Jacek Majchrowski, Mayor of the City of Kraków

 

first_bulletin.pdf

second_bulletin.pdf

third_bulletin.pdf

Monday, 4 April

08:00 → 09:00 Registration for students

09:00 → 17:30 Lectures for students

Conveners: Maciej Rybczynski (Jan Kochanowski University (PL)), Tetyana Galatyuk, Wojciech Florkowski (Jagiellonian University)

09:00 A brief historical introduction

Speaker: Federico Antinori (Universita e INFN, Padova (IT))

FA-QM22.pdf

10:00 Break

10:15 High-energy heavy-ion collisions and underlying QCD phenomena

Speaker: Francois Gelis

11:15 Coffee break

12:00 Experimental opportunities in heavy-ion collisions

Speaker: Peter Braun-Munzinger (GSI - Helmholtzzentrum fur Schwerionenforschung GmbH (DE))

2022_QMstudent_pbm.pdf

13:00 Lunch break

14:30 Diagnosing the Quark-Gluon Plasma

Speaker: Berndt Mueller

BerndtMuller_QM2022.pdf

15:30 Break

15:45 AI in particle and nuclear physics

I review the basics and current status of machine learning in particle/nuclear physics, with emphasis on understanding how it works.

Speaker: Wojciech Broniowski (IFJ PAN & UJK)

AI_phys.pdf

16:45 Coffee break

17:30 → 18:30 Special lecture by Artur Konrad Ekert

Convener: Wojciech Florkowski (Jagiellonian University)

17:30 Quantum technologies

The Age of Computation is yet to Come

The theory of classical universal computation was laid down in 1936, was implemented within a decade, became commercial within another decade, and dominated the world’s economy half a century later. This success story relied on the progress in technology. As computers become faster they must become smaller. The history of computer technology has involved a sequence of changes from one type of physical realisation to another, with smaller and smaller components. The unavoidable step to the quantum level will be one in this sequence; but it promises something more exciting as well. It can support entirely new modes of computation that do not have classical analogues. At present it is not clear when, how and even whether fully-fledged quantum computers will eventually be built; but notwithstanding this, the quantum theory of computation already plays a much more fundamental role in the scheme of things than its classical predecessor did. I believe that anyone who seeks a fundamental understanding of either physics, computation or logic must incorporate its new insights into their world view. There is so much potential in this fundamentally new way of harnessing nature that it appears as though the age of computation has not yet even begun!

Speaker: Artur Konrad Ekert (National University of Singapore and Oxford University)

18:30 → 19:30 General registration for all participants

Tuesday, 5 April

08:00 → 08:45 Registration

08:45 → 09:15 Welcome and conference opening:

Convener: Wojciech Florkowski (Jagiellonian University)

08:45 Jerzy Muzyk - Deputy Mayor of the City of Krakow

08:51 Ewa Gudowska-Nowak - Dean of the Faculty of Physics, Astronomy and Applied Computer Sciences, Jagiellonian University

08:57 Bogdan Fornal - Scientific Director of the Institute of Nuclear Physics, Polish Academy of Sciences

09:03 Bartłomiej Szafran - Dean of the Faculty of Physics and Applied Computer Sciences, AGH University of Science and Technology

09:09 Andrzej Białas - Jagiellonian University and Polish Academy of Arts and Sciences

09:15 → 10:15 Plenary Session I

Convener: Marek Jezabek (Institute of Nuclear Physics Polish Academy of Sciences (PL))

09:15 The fascinating evolution of the questions of interest in relativistic heavy ion physics

Speaker: Wit Busza (Massachusetts Inst. of Technology (US))

Busza talk QM22.ver 5.pdf

09:45 Deciphering deconfinement and hadronization: achievements and opportunities

Speaker: Johanna Stachel (Ruprecht Karls Universitaet Heidelberg (DE))

qm2022_stachel.pdf

10:15 → 10:45 Coffee break

10:45 → 12:45 Plenary Session II: Experimental highlights

Convener: Barbara Jacak (University of California Berkeley (US))

10:45 Highlights from the ALICE experiment

Speaker: Maximiliano Puccio (CERN)

220405-mpuccio-qm.pdf

11:15 Highlights from the ATLAS experiment

Speaker: Dominik Karol Derendarz (Polish Academy of Sciences (PL))

QM22_atlas.pdf

11:40 Highlights from the CMS experiment

Speaker: Yongsun Kim (Sejong University (KR))

cms.overview_qm22_yongsun.kim.pdf

12:05 Highlights from the LHCb experiment

Speaker: Emilie Maurice (Centre National de la Recherche Scientifique (FR))

Emaurice_QMLHCboverview.pdf

12:25 Highlights from the HADES experiment

Speaker: Szymon Harabasz

SzymonHarabasz_HADES_QM2022_ver4.pdf

12:45 → 14:05 Lunch

14:05 → 15:00 Plenary Session III: Experimental highlights

Convener: Barbara Krystyna Wosiek (Institute of Nuclear Physics Polish Academy of Sciences (PL))

14:05 Highlights from the STAR experiment

Speaker: Prithwish Tribedy (Brookhaven National Lab)

qm2022_star_highlight_ptribedy.pdf

14:30 Highlights from the PHENIX experiment

Speaker: Sanghoon Lim (Pusan National University (KR))

QM22_shlim_PHENIX_overview.pdf

14:45 Highlights from the NA61/SHINE experiment

Speaker: Antoni Marcinek (Polish Academy of Sciences (PL))

marcinek_QM_2022_04_05.pdf

15:00 → 16:00 Keynote presentation by Frank Wilczek

Convener: Krzysztof Redlich (University of Wroclaw)

15:00 Axions: QCD's Blooming Child

Axions arose in theoretical attempts to understand the observed symmetry of QCD. Remarkably, they have the right properties to provide the "dark matter" that astronomers need. There are promising new ideas to test that hypothesis, especially including the ALPHA plasma haloscope that I will describe. I will also discuss how better understanding and data in QCD can help us refine our ideas about axions, and add a few words about emergent axions.

Speaker: Frank Wilczek (MIT)

16:00 → 16:30 Coffee break

16:30 → 18:50 Parallel Session T01: Initial state physics and approach to thermal equilibrium: I

Convener: Michael Strickland (Kent State University)

16:30 Probing the initial state with isolated-photon production and dijet invariant mass distributions in small collision systems with ALICE

Isolated photons and dijets measurements in small collision systems probe the initial state of the collision, providing the opportunity to constrain PDFs, test pQCD predictions, and probe cold nuclear matter effects. In addition, dijet measurements are sensitive to interactions of partons with the medium produced in Pb-Pb collisions that induce modifications in jet properties. Measurements in small collision systems therefore also offer a baseline for Pb-Pb collision measurements.

We present the measurement of isolated photons and dijets in small collisions systems, pp and p-Pb by ALICE. Isolated photons are measured in pp collisions at $\sqrt s = 5.02$, 8, and 13 TeV and in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02$ and 8.16 TeV, down to $p_{\mathrm{T}} = 10$ GeV/$c$, extending previous measurements at these centre-of-mass energies down to small $x\sim10^{-3}$. Dijets are measured in pp and p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV with $R=0.4$ and the anti-$k_\mathrm{T}$ algorithm, and with azimuthal angle of at least $\pi/2$ between the two jets. The dijet invariant mass is measured in the range from $80$ to $150$ GeV$/c^2$, probing a region where medium effects are expected to be strong.

Speaker: Sinjini Chandra (Department of Atomic Energy (IN))

QM22_sinjini_V6.pdf

16:50 Photo-nuclear jet production in Pb+Pb collisions with the ATLAS detector

Beams of relativistic heavy ions are accompanied by a large flux of equivalent photons, and thus photon-induced reactions are the dominant interaction mechanism in heavy-ion collisions when the colliding nuclei have transverse separation larger than the nuclear diameter. In these ultra-peripheral collisions (UPCs) the photon can provide a clean probe of the partonic structure of the nucleus analogous with deep inelastic scattering. This talk presents a new measurement of dijet production in ultra-peripheral Pb+Pb collisions performed with the ATLAS detector using high-statistics 2018 Pb+Pb data. Events are selected using requirements on rapidity gaps and forward neutron production to identify the photo-nuclear processes. The relatively clean environment of these events allows for precision measurements in a phase-space regions where significant nuclear PDF modifications are expected to be present, and which are not strongly constrained by previous measurements.

Speaker: Benjamin Jacob Gilbert (Columbia University (US))

Gilbert_QM_Photonuclear_Dijet.pdf

17:10 Jet quenching in anisotropic media

Over the last decades, many of the available theoretical jet quenching formalisms have been extended to account for the medium’s finite longitudinal extension and expansion. However, only recently a first-principle approach has been developed that allows to study jet evolution in anisotropic media in the dilute limit. In this talk, we show how to extend some of the previous results to the dense regime, where the resummation of multiple in-medium scatterings is necessary. We consider, in particular, a non-flowing background with finite matter gradients and compute the single particle momentum broadening distribution and the single gluon production rate, two crucial observables for jet quenching phenomenology. The resumation is performed by either computing the opacity series or starting from the all order BDMPS-Z formalism. The (novel) resulting modifications to jets’ substructure are discussed.

Speaker: Andrey Sadofyev (Los Alamos National Laboratory, T-2)

QM2022_05:04:2022.pdf

QM2022_05:04:2022.pptx

17:30 Observation of azimuthal angular decorrelation in dijet photoproduction in ultraperipheral lead-lead collisions at $\sqrt{s_{_{\mathrm{NN}}}} =$ 5.02 TeV with the CMS experiment

Angular correlations present in dijet photoproduction are studied, for the first time, using ultraperipheral lead-lead collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The second moment of the angular distribution, $\langle \cos(2\Phi) \rangle$, where $\Phi$ is the angle between the vector sum $\vec{Q}_\mathrm{T}$ and the vector difference $\vec{P}_\mathrm{T}$ of the transverse momentum vectors of the jets, is measured as a function of $\vec{Q}_\mathrm{T}$. This analysis amounts to the first, yet essential, step towards the extraction of the Wigner or Husimi gluon distributions, which are believed to be the most fundamental gluon distributions. It also introduces new techniques for the analysis of jet angular correlations in exclusive dijet events at colliders.

Speaker: Aleksandr Bylinkin (The University of Kansas (US))

Bylinkin_QM_2022_final.pdf

17:50 Far-from-equilibrium attractors in a 3+1D transport approach at fixed $\eta/s$

Within the framework of a 3+1D Boltzmann transport approach at fixed $\eta/s$ with the full collision integral, we investigate the existence of far-from equilibrium attractors in momentum moments of the one particle distribution function. We first compare our results for a conformal and non conformal gas for different values of $\eta/s$ and $m$, in order to investigate the role of the equation of state in approaching the universal attractor. We then extend our study by employing a quasi-particle model of quarks and gluons with thermal masses tuned to reproduce lattice QCD thermodynamics. We finally examine the possible existence of attractors in the anisotropic flow coefficients, under the influence of initial momentum anisotropy.

Speaker: Salvatore Plumari

QM2022_Plumari.pdf

18:10 Non-equilibrium attractor in high-temperature QCD plasmas

We establish the existence of a far-from-equilibrium attractor in weakly-coupled gauge theory undergoing one-dimensional Bjorken expansion. We demonstrate that the resulting far-from-equilibrium evolution is insensitive to certain features of the initial condition, including both the initial momentum-space anisotropy and initial occupancy. We find that this insensitivity extends beyond the energy-momentum tensor to the detailed form of the one-particle distribution function. Based on our results, we assess different procedures for reconstructing the full one-particle distribution function from the energy-momentum tensor along the attractor and discuss implications for the freeze-out procedure used in the phenomenological analysis of ultra-relativistic nuclear collisions.

Speaker: Dekrayat Almaalol (University of Illinois Urbana-Champaign)

DekrayatAlmaalol-QM2022.pdf

18:30 Novel relaxation time approximation: a consistent calculation of transport coefficients with QCD-inspired relaxation times

The relativistic generalization of the relaxation time approximation proposed by Anderson and Witting [1] is widely used in several fields of physics and, in particular, in the study of the hydrodynamization of the matter produced in ultrarelativistic heavy ion collisions. We demonstrate that the approximation proposed by Anderson and Witting contains basic flaws, not being consistent with fundamental properties of the Boltzmann collision operator [2]. This makes it impossible to consistently model relativistic gases using energy dependent relaxation times or more general choices of the local equilibrium state. We propose a new relaxation time approximation which fixes these fundamental flaws [2]. In this contribution, this new formulation is used to consistently calculate the bulk and shear viscosity coefficients using QCD-inspired energy-dependent relaxation times [3] and phenomenological thermal masses obtained from fits to lattice QCD thermodynamics [4].

[1] J. L. Anderson and H. Witting, Physica 74, 466 (1974).

[2] G. S. Rocha, G. S. Denicol and J. Noronha, Phys. Rev. Lett. 127, no. 4, 042301 (2021).

[3] K. Dusling, G. D. Moore and D. Teaney, Phys. Rev. C 81, 034907 (2010).

[4] M. Alqahtani, M. Nopoush and M. Strickland, Phys. Rev. C 92, no.5, 054910 (2015).

Speaker: Gabriel Soares Rocha

QM22-Quasi-part-Gabriel-Soares.pdf

16:30 → 18:50 Parallel Session T02: Chirality, vorticity and spin polarization: I

Convener: Michael Lisa

16:30 Probing the spin dynamics of QCD medium and initial strong magnetic field in heavy-ion collisions via global spin alignment of vector mesons at RHIC

In non-central heavy-ion collisions (HIC), the large initial angular momentum can induce a non-vanishing polarization for hadrons with non-zero spin. The global spin alignment of vector mesons, quantified by the $00^{th}$ element of spin density matrix ($\rho_{00}$), can offer information on the spin-orbital interactions of the QCD medium. Surprisingly large signal of vector meson $\rho_{00}$ compared to hyperon spin polarization poses challenges to the conventional theoretical understanding of polarization in HIC. Preliminary observations from Beam Energy Scan (BES-I) of large deviations of $\rho_{00}$ from 1/3 for $\phi$ mesons can only be explained by introducing the vector meson strong force fields.

In this talk, we will present transverse momentum and collision centrality dependence of $\phi$, $K^{*0}$, $\overline{K^{*0}}$, $K^{*+}$, and $K^{*-}$ vector mesons using recent high statistics Beam Energy Scan (BES-II) data of Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 7.7 - 27 GeV, and isobar collisions (Zr+Zr and Ru+Ru) at $\sqrt{s_{\rm NN}}$ = 200 GeV. The BES-II data will provide unprecedented precision in $\rho_{00}$ at these energies. Comparison of $\rho_{00}$ between Au+Au and isobar species can provide information on the system size dependence of $\rho_{00}$. Moreover, since the magnetic moment of charged and neutral $K^{*}$ differ by a factor of seven, the comparison of their $\rho_{00}$ may serve as a new probe for the initial strong magnetic field in HIC.

Speaker: Subhash Singha (Institute of Modern Physics Chinese Academy of Sciences)

SpinAlign_QM2022_SINGHA_ver_submit.pdf

16:50 Quarkonium polarization in Pb-Pb and pp collisions with ALICE

Polarization and spin-alignment measurements represent an important tool for the understanding of the particle production mechanisms occurring in proton–proton collisions. When considering heavy-ion collisions, quarkonium polarization could also be used to investigate the characteristics of the hot and dense medium (quark-gluon plasma) created at LHC energies. In ALICE, this observable was extracted for the first time in Pb-Pb collisions and a significant difference with respect to a corresponding pp measurement of LHCb was found. This discrepancy could be related to the modification of the J/$\psi$ feed down fractions, due to the suppression of the excited states in the QGP, but also to the contribution of the regenerated J/$\psi$ in the low $p_{\rm{T}}$ region. Moreover, it has been hypothesized that quarkonium states could be polarized by the strong magnetic field, generated in the early phase of the evolution of the system, and by the large angular momentum of the medium in non-central heavy-ion collisions. This kind of information can be assessed by defining an ad hoc reference frame where the quantization axis is orthogonal to the event plane of the collision.
In this contribution, the new result of J/$\psi$ polarization with respect to the event-plane in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV will be presented. The $p_{\rm T}$-differential measurement is performed at forward rapidity (2.5 $<$ y $<$ 4) and the results will be shown for different centrality classes. The preliminary measurement of the $\Upsilon$ polarization in pp collisions at $\sqrt{s} = 13$ TeV as a function of the transverse momentum will also be discussed.

Speaker: Luca Micheletti (Universita e INFN Torino (IT))

quarkonium_polarization_Luca_Micheletti_QM22.pdf

17:10 Interpretation of Λ hyperons spin polarization measurements

The physics interpretation of the recent measurements of the spin polarization of Λ hyperons produced in relativistic heavy-ion collisions is discussed. It is suggested that the polarization measured in the Λ rest frame should be projected along the direction of the total angular momentum that is first transformed to the same frame, and only then averaged over Λ’s with different momenta in the center-of-mass frame. While the improved procedure is not expected to significantly change the present results regarding the global spin polarization, it may affect the estimates of the magnitude of the polarization and its energy dependence. Such a treatment is also generally more appropriate whenever directions in the Λ rest frame and in the center-of-mass frame are compared.

Speaker: Dr Radoslaw Ryblewski (Institute of Nuclear Physics PAN)

QM_2022_Ryblewski_v2.pdf

17:30 Anomalous spin polarization from turbulent color fields

Recent observations for the spin polarization and alignments in RHIC and LHC have triggered intensive studies for vorticity-induced polarization and spin dynamics in relativistic fluids. We study the important, yet widely overlooked, role of gluons for spin transport with a connection to local parity violation in quark gluon plasmas. We extend the newly developed quantum kinetic theory for relativistic fermions coupled with background electromagnetic fields to the case coupled with non-Abelian chromo-electromagnetic fields and employ this formalism to derive the source terms in the axial-vector Wigner function and kinetic equation for spin polarization of quarks. These source terms, which may dominate over collisional effects at weak coupling, involve parity-odd correlators of dynamically generated color fields in near-equilibrium quark gluon plasmas and give rise to locally fluctuating axial charge currents. Our results provide a possible explanation for the spin alignment of vector mesons measured in high-energy nuclear collisions and allude to its connection with local parity violation.
References :
[1] Berndt Müller, Di-Lun Yang, Anomalous spin polarization from turbulent color fields, arXiv:2110.15630.
[2] Di-Lun Yang, Koichi Hattori, Yoshimasa Hidaka, Effective quantum kinetic theory for spin transport of fermions with collisional effects, JHEP 07 (2020) 070.
[3] Axial Kinetic Theory and Spin Transport for Fermions with Arbitrary Mass, Koichi Hattori, Yoshimasa Hidaka, Di-Lun Yang, Phys. Rev. D 100 (2019) 9, 096011.

Speaker: Di-Lun Yang (Academia Sinica)

QM2022.pdf

17:50 Effect of thermal shear on longitudinal spin polarization in a thermal model

By including the recently introduced thermal shear term of the spin polarization vector at local equilibrium we determine longitudinal polarization of Λ hyperons emitted from a hot and rotating hadronic medium using the thermal model with single freeze-out. In our analysis we consider top RHIC energy and use the model parameters which were determined in the previous analyses of particle spectra and elliptic flow. We confirm that unlike the previous calculations done by using only the thermal vorticity, the thermal shear term alone leads to the correct sign of the quadrupole structure of the longitudinal component of the polarization three vector as measured in experiments. However, we find almost complete cancellation between thermal and shear vorticity terms, which leads to the disagreement with the data. To clarify the role played by velocity and temperature gradient terms, we present a systematic analysis of different contributions to the longitudinal polarization.

Speaker: Dr Avdhesh Kumar (Indian Institute of Technology Gandhinagar)

Avdhesh_QM2022.pdf

18:10 Spin-thermal shear coupling in relativistic nuclear collisions

The measurements of spin polarization of particles emitted in heavy-ion collisions has opened the possibility for new phenomenological investigations of spin physics in relativistic fluids. The theoretical predictions of global polarization are in agreement with the data, but consistent discrepancies stand out for the local polarization. In this talk, I will show that the covariant theory of quantum relativistic fluids at local equilibrium implies an additional, non-dissipative, contribution to the spin polarization vector which is proportional to the thermal shear which has been previously overlooked. This additional contribution together with an improved approximation in the expansion of the density operator at local equilibrium is able to restore the quantitative agreement between the theoretical predictions and the experimental data.
[F. Becattini, M. Buzzegoli and A. Palermo, Phys.Lett.B 820 (2021) 136519]
[F. Becattini, M. Buzzegoli, A. Palermo, G. Inghirami and I. Karpenko, arXiv:2103.14621]

Speaker: Matteo Buzzegoli

QM22-Spin-thermal_shear.pdf

18:30 Shear-induced polarization at RHIC and LHC

The local Lambda polarization puzzle associated with the model calculations by thermal vorticity has attracted lots of attention in heavy ion community [1].

In addition to the widely studied thermal vorticity effect, we identify an undiscovered contribution from the fluid shear [2]. We obtain the explicit expression for shear-induced polarization (SIP) from quantum kinetic equation and linear response theory. Using hydrodynamic simulations, we find SIP effect competes with the thermal vorticity effect and shows right sign (trend) to the azimuthal dependent local spin polarization $P_y(\phi)$ and $P_z(\phi)$. Especially, in the scenario that Lambda inherits and memorizes the spin polarization of strange quark, SIP wins the competition and the obtained local $P_y(\phi)$ and $P_z(\phi)$ qualitatively agree with the data measured at top RHIC energy [2].

Furthermore, we extend the calculation to event-by-event simulations for various collision systems at RHIC and LHC. We calculate the 2nd order Fourier coefficient of $P_z$, which qualitatively agrees with the ALICE measurements in 5.02 A TeV Pb+Pb collisions [3, 4]. We also predict the 3rd order Fourier coefficients, which provide more details for spin polarization and can be measured in the RHIC isobar run with high statics [4].

Refs.

[1] B. Fu, K.Xu, X. G. Huang and H. Song, Phys. Rev. C103, no.2, 024903 (2021) ; and many related papers from other groups before.
[2] B. Fu, S.Y.F. Liu, L. -G. Pang, H. Song, Y. Yin, Phys.Rev.Lett. 127 14, 142301 (2021)
[3] ALICE Collaboration, arXiv:2107.11183 [nucl-ex]
[4] B. Fu, L. -G. Pang, H. Song, Y. Yin in preparation

Speaker: Baochi Fu

QM22-BaochiFu-SIP+SHE.pdf

16:30 → 18:50 Parallel Session T03: QCD matter at finite temperature and density: I

16:30 Higher-Order Cumulants and Correlation Functions of Proton Multiplicity Distributions in Au+Au Collisions at $\sqrt{s_{_{\mathrm{NN}}}}$ = 3.0 GeV

The higher-order fluctuations of conserved quantities such as net baryon number are predicted to be sensitive to the non-equilibrium correlation length, $\xi$, and thus serve as indicators of critical behavior. Experimentally, fluctuations of proton and anti-proton numbers have been shown to be reliable proxies for baryons and anti-baryons. In the first Beam Energy Scan (BES-I) at the Relativistic Heavy Ion Collider (RHIC), which was run from 2010-2014, the higher-order cumulant ratio, $C_4/C_2$, of the net-proton multiplicity distributions shows a non-monotonic energy dependence between the energies of 7.7 to 62.4 GeV with a significance of 3.1$\sigma$. Motivated by the findings of BES I, the Solenoidal Tracker at RHIC (STAR) collaboration improved the detector performance of the STAR detector and began two additional physics programs: the BES-II and the fixed-target (FXT) program. While BES-II revisits the energies of BES-I with higher statistics and improved detector performance, the FXT program extends the lowest energy from $\sqrt{s_{_{\mathrm{NN}}}}$ = 7.7 GeV to $\sqrt{s_{_{\mathrm{NN}}}}$ = 3.0 GeV.

In this talk, we present the higher-order cumulants of proton multiplicity distributions of the FXT run in Au+Au collisions at $\sqrt{s_{_{\mathrm{NN}}}}$ = 3.0 GeV. The data, 140 million minimum bias events, were recorded with the STAR detector at the RHIC facility with a 250 $\mu$m thick target (1\% interaction probability). The ratios of both cumulants and correlation functions are presented as a function of centrality, acceptance, and collision energy. We discuss the physics implications of these results with comparisons to results from the HADES experiment and a hadronic transport model.

Speaker: Yu Zhang (Central China Normal University)

3GeV_QM2022.pdf

16:50 Soft pions near the QCD chiral critical point: transport and dynamics

During the evolution of a heavy ion collision, the system passes close to the O(4) critical point. The order parameter that controls the chiral symmetry is the quark condensate $\langle \bar q q \rangle \sim \phi_a $. Due to the non-zero quark mass, there is a crossover (not a second order phase transition) between the high and low temperature phases. In this talk we will introduce the hydrodynamic theory with the order parameter as an additional hydrodynamical variable and show the results of the real time simulation of this model that shares the same universality class of QCD, the so-called Model G.

Due to the presence of the superfluid pion degrees of freedom, we compute the modification of the ordinary hydrodynamic transport coefficients and estimate the expected critical enhancement of soft pion yields, which provides a plausible explanation for the excess seen in experiment relative to ordinary hydrodynamic computations. We extract the dynamical critical exponent of $\zeta=1.47 \pm 0.01 ({\rm stat})$, which is compatible with the theoretical expectation of $\zeta = d/2$ (with $d=3$).
Based on 2005.02885, 2101.10847 and 2111.03640

Speaker: Dr Eduardo Grossi (IPhT Saclay)

QM2022.pdf

17:10 Embedding a Critical Point in a Hadron to Quark-Gluon Crossover Equation of State

Lattice QCD simulations have shown unequivocally that the transition from hadrons to quarks and gluons is a crossover when the baryon chemical potential is zero or small. Many model calculations predict the existence of a critical point at a value of the chemical potential where current lattice simulations are unreliable. We show how to embed a critical point in a smooth background equation of state so as to yield the critical exponents and critical amplitude ratios expected of a transition in the same universality class as the liquid-gas phase transition and the 3D Ising model. The resulting equation of state has parameters which may be inferred by hydrodynamic modeling of heavy ion collisions in the upcoming Beam Energy Scan II at the Relativistic Heavy Ion Collider.

Speaker: Joseph Kapusta

QM2022_Kapusta.pdf

17:30 EVOLUTION OF NON-GAUSSIAN HYDRODYNAMIC FLUCTUATIONS

In the context of the search for the QCD critical point using
non-Gaussian fluctuations, we obtain the evolution equations for
non-Gaussian cumulants within hydrodynamics to leading order of the
systematic expansion in the magnitude of thermal fluctuations. We
develop diagrammatic technique in which the leading order
contributions are given by tree diagrams. We introduce the concept of
Wigner transform for multipoint correlators and derive the evolution
equations for the novel three- and four-point Wigner functions. We
demonstrate in a simple model simulation how this formalism accounts
for the effects of memory and baryon number conservation on critical
point signatures in non-Gaussian fluctuations.

References: Phys.Rev.Lett. 127 (2021) 7, 072301 and work in progress.

Speaker: Xin An (University of North Carolina)

XA_QM22.pdf

17:50 Measuring the speed of sound using cumulants of baryon number

We show that the values of the first three cumulants of the baryon number distribution can be used to calculate the isothermal speed of sound and its logarithmic derivative with respect to the baryon number density. We discuss application of this result to heavy-ion collision experiments and address possible challenges, including effects due to baryon number conservation, differences between proton and baryon cumulants, and the influence of finite number statistics on fluctuation observables in both experiment and hadronic transport simulations. In particular, we investigate the relation between quantities calculated in infinite, continuous matter and observables obtained in simulations using a finite number of particles.

Speaker: Agnieszka Sorensen (INT)

ASorensen_2022.04.05_QM22_talk_indico.pdf

18:10 Baryon Stopping and Associated Production of Mesons in Au+Au Collisions at $\sqrt{s_{NN}}=3.0$ GeV at STAR

Charged particles in heavy-ion collisions have various production mechanisms, such as thermal and associated production, and the importance of each changes with the collision energy. Studying the yields of charged particles provides a way to investigate the properties of the produced QCD matter in heavy-ion collisions and the various production mechanisms. The RHIC Beam Energy Scan (BES) programs cover a wide range of energies, including the transition from a hadronic dominated medium to a partonic dominated medium. The recently completed BES-II program was designed to improve and extend upon the results from the BES-I program. Of particular interest is the high baryon density region which is accessible through the STAR fixed-target program, extending the energy reach from $\sqrt{s_{NN}}=7.7$ GeV down to $\sqrt{s_{NN}}=3.0$ GeV. This presentation reports on measurements of charged particle production in Au+Au collisions at $\sqrt{s_{NN}}=3.0$ GeV. Measurements of the proton stopping will be presented in addition to measurements of the production of $K^{+}$ in association with the $\Lambda$ baryon. Invariant yields and rapidity density distributions of $\pi^{\pm}$, $K^{\pm}$, and $p$ will also be presented, which will help to unravel the relative importance of the different particle production mechanisms. These measurements provide an in-depth study of the various production mechanisms for light hadrons and probe unique properties of the high baryon density medium produced in these low energy collisions.

Speaker: Benjamin Kimelman

Kimelman_QM2022_Final.pdf

18:30 Comprehensive study of multi-scale jet-medium interaction

We explore jet-medium interactions at various scales in high-energy heavy-ion collisions using JETSCAPE 3, a publicly available software framework for Monte Carlo event generators. In jet shower evolution, the virtuality and energy of each jet parton vary considerably. Thus, in high-energy heavy-ion collisions, jets can be used as dynamical probes to investigate the jet-medium interaction at various scales. JETSCAPE is a framework that enables simulations describing physics at varying scales involved in in-medium jet evolution. The JETSCAPE framework incorporates multiple models, each effective at an individual scale range, and switches between them at appropriate scales while mediating their communication.

As a new feature, the jet quenching strength q-hat with an explicit virtuality dependence depending on the resolution scale evolution of jets is now supported by JETSCAPE. In this talk, we demonstrate that this further extension is crucial for a simultaneous description of the nuclear modification factor for inclusive jets and leading hadrons. For more detailed discussion of the virtuality dependence in the jet-medium interaction, observables for jet substructures, heavy-flavor jets, and photon-triggered jets are also explored. Furthermore, we investigate the jet-medium interaction involved in the hadronization process.

Speaker: Yasuki Tachibana (Akita International University)

tachibana_QM22.pdf

16:30 → 18:50 Parallel Session T04: Jets, high-pT hadrons, and medium response: I

Convener: Peter Levai (Wigner Research Centre for Physics (Wigner RCP) (HU))

16:30 Isolated-photon production and photon-jet correlations in pp and Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV in ALICE

Jets correlated with isolated photons are a promising channel to study jet quenching in heavy-ion collisions, as photons do not interact strongly and therefore constrain the $Q^2$ of the initial hard scattering. The measurement of isolated single photon production constrains NLO pQCD predictions and PDFs, and isolated photon production in Pb-Pb collisions is sensitive to initial geometrical scaling and modifications of the nucleon structure function in nuclei. We present the isolated photon distributions measured in pp and Pb-Pb collisions and isolated photon-jet correlations measured in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV by the ALICE collaboration. The isolated-photon production is measured in the $12 < p_\mathrm{T} < 60$ GeV/$c$ range in pp collisions and in the $10 < p_\mathrm{T} < 100$ GeV/$c$ for the Pb-Pb collisions. We study correlations of isolated photons above 20 GeV/$c$ with charged-particle jets above 20 GeV/$c$, reconstructed with the anti-$k_{\rm T}$ algorithm. The correlations probe the lowest $p_\mathrm{T}$ range measured so far at LHC energies, and larger modifications due to the QGP are expected in the lower $p_\mathrm{T}$ regime.

Speaker: Alwina Liu (University of California Berkeley (US))

qm2022-gammajet-alice.pdf

16:50 Measurements of Z- and jet-tagged fragmentation and medium response in Pb+Pb and p+Pb collisions by ATLAS

Measurements of high $p_\mathrm{T}$ hadrons produced in hard scattering events offer insight to the modification of jet fragmentation and medium response of the quark-gluon plasma (QGP)
created in ultrarelativistic nucleus-nucleus collisions.
The hard scatter, tagged by an electroweak boson or a jet, fixes initial properties of the showering partons prior to interactions with the QGP. In large systems, modification to the parton fragmentation is an expected consequence of the strong medium interactions, while in small systems, indications of QGP
droplet formation are juxtaposed with previous observations of minimal jet quenching.
With the large luminosity from Run 2 data taking, ATLAS has performed new measurements of hadrons correlated with Z bosons in Pb+Pb collisions, notably without any formal reconstructed jet requirement which reduces any potential bias toward
particular fragmentation patterns. Theoretical models of parton evolution in the QGP, particularly those with medium response, are compared to this data. Additionally, a new measurement of jet-hadron correlations in centrality-selected $p$+Pb collisions is presented and compared with theoretical expectations. The measurement provides stringent limits on both cold nuclear matter and possible jet quenching effects.

Speaker: Christopher Mc Ginn (University of Colorado Boulder (US))

qm2022Krakow_CFMATLAS_PbPbZ_pPbJet_v4_20220405.pdf

17:10 Using Z-boson tags to study parton-medium interactions in PbPb collisions at 5.02 TeV with the CMS detector

Z bosons can be used to constrain the initial energy, direction, and the flavor of the recoiling parton before its interaction with the quark-gluon plasma. By measuring charged particle yields in Z boson events one can study the in-medium modifications of the recoiling parton showers and as well as the soft particles from medium response. The talk will present measurements of the azimuthal angular distributions, fragmentation functions and $p_\mathrm{T}$ spectra of charged particles tagged with Z bosons in pp and PbPb collisions at $\sqrt{s_{_{\mathrm{NN}}}} = 5.02\,\mathrm{TeV}$ using data collected with the CMS detector.

Speaker: Kaya Tatar (CERN)

220405_QM22_KayaTatar.pdf

17:30 Measurement of medium-induced modification of jet yield and acoplanarity using semi-inclusive $\gamma_{\text{dir}}$+jet and $\pi^{0}$+jet distributions in $p$+$p$ and central Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV by STAR

We report high-statistics measurements of semi-inclusive distributions of charged jets recoiling from high-$E_{\text{T}}$ direct photon ($\gamma_{\text{dir}}$) and $\pi^{0}$ triggers in $p$+$p$ and central Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV. In a semi-inclusive approach, event bias is induced solely by the choice of trigger; separately utilizing $\gamma_{\text{dir}}$ and $\pi^{0}$ triggers in this analysis therefore provides direct comparison of jet quenching effects for jet populations with different q/g fractions and different in-medium path length distributions. Jets are reconstructed from charged particles using the anti-$\text{k}_{\text{T}}$ algorithm with jet resolution parameters $R_{\text{jet}} = 0.2$ and 0.5. The large uncorrelated background in central Au+Au collisions is corrected using a mixed event technique. This enables a jet measurement extending to low $p_{\text{T}}$ and large $R_{\text{jet}}$ with well-controlled systematic uncertainties, which are of particular importance in searching for jet scattering effects. We report recoil jet yield and trigger-jet acoplanarity distributions for jets with $p_{\text{T}} > 5$ GeV/$c$. The comparison of recoil yields in Au+Au and $p$+$p$ collisions at fixed $R_{\text{jet}}$ probes energy loss in heavy-ion collisions. Moreover, the comparison of recoil yields for different $R_{\text{jet}}$ in Au+Au and $p$+$p$ collisions probes intra-jet broadening. The modification of trigger-jet acoplanarity distributions in central Au+Au collisions relative to $p$+$p$ collisions highlights the sensitivity of such a measurement to QGP transport parameters. We also search for evidence of large-angle scattering of jets off of quasi-particles in the QGP. The measured recoil yields and acoplanarity distributions are compared to theoretical calculations.

Speakers: Derek Anderson (Texas A&M University), Derek Anderson (Texas A & M University)

AndersonTalk_QM2022.v11_manualAnimations.pdf

17:50 The role of initial state radiation in jet substructure observables

Experimentalists and theorists are pushing towards studying large radius jets in heavy ion collisions in an endeavour to decode signs of induced radiation and medium response with increasing precision. However, even at mid-rapidity, jets are not entirely composed of final state emissions, but contain a varying amount of initial state radiation. This contribution is small for small radius jets, but increases with jet radius and can become sizeable for large radius jets. I study in detail the contributions from initial state radiation to different jet substructure observables in p+p and A+A collisions, and show how they can compromise the interpretation of these observables in heavy ion collisions in terms of medium effects. This is done with an extended version of JEWEL, in which partons emitted from the initial state parton shower interact in the background medium in the same way as final state partons.

Speaker: Korinna Zapp

qm22.pdf

18:10 Multipartonic cascades in expanding media

In this work, we introduce both gluon and quark degrees of freedom for describing the partonic cascades inside the medium. We present numerical solutions for the set of coupled evolution equations with splitting kernels calculated for the static, exponential and Bjorken expanding media to arrive at medium-modified parton spectra for quark and gluon initiated jets respectively. We discuss novel scaling features of the partonic spectra between different types of media. Next, we study the inclusive jet $R_{AA}$ by including phenomenologically driven combinations of quark and gluon fractions inside a jet. In addition, we have also studied the effect of the nPDF as well as vacuum like emissions on the jet $R_{AA}$. Differences among the estimated values of quenching parameter for different types of medium expansions are noted. Next, the impact of the expansion of the medium on the rapidity dependence of the jet $R_{AA}$ as well as jet $v_2$ are studied in detail. Finally, we present qualitative results comparing the sensitivity of the time for the onset of the quenching for the Bjorken profile on these observables. All the quantities calculated are compared with the recent ATLAS data.

Speaker: Mr Souvik Priyam Adhya (Institute of Nuclear Physics, Polish Academy of Sciences)

jet_qm22_souvik.pdf

18:30 Sensitivity of jet observables to the presence of quasi-particles in the QGP

Even though QGP, when looked at on length scales of order the inverse of its temperature, is best described as a strongly coupled liquid, when it is observed at sufficiently short length scales or probed at sufficiently high exchanged-momentum, asymptotic freedom predicts the presence of quark-like and gluon-like quasi-particles. High energy partons (e.g. those in jet showers) traversing the QGP, capable of triggering these high-momentum exchanges with the medium constituents, have the potential to reveal the presence of such quasi-particles.

In this work we present an implementation of this physics within the hybrid strong/weak coupling model in which, prior to this work, only the non-perturbative aspects of parton energy loss had been accounted for. Interaction with the quasi-particles results in elastic Moliere scatterings, leading to deflection of the direction of the jet parton that induced the process as well as the excitation of partons from the thermal medium that recoil after being kicked. Throughout the in-medium evolution, the system of jet partons and recoils, which might further re-scatter, inject energy and momentum into the QGP, producing wakes. We analyze a variety of setups, such as boson-jet systems, c-cbar systems, as well as dijet systems, at different jet transverse momenta and reconstruction radius, R. We will discuss the effect of Moliere scatterings on acoplanarity distributions, as well as on some of the most widely used groomed and ungroomed jet substructure observables.

Given the large impact of the wakes generated by the hydrodynamic response of the medium on jet observables, as well as the presence of selection biases, finding unique signatures of the presence of the elastic scatterings is a challenging task. We will present some strategies that may be followed with a view toward enhancing and isolating the effect under consideration. These include the application of momentum cuts, differential studies of the angular distribution of particles around the jet, and, most revealing, the properties of the subjets (jets within jets) distributions. A comparison against the effect of a purely Gaussian, Brownian-like transverse momentum broadening will also be presented.

Speaker: Zach Hulcher (Stanford University)

QMKrakow_ZH_final.pdf

18:50 → 20:20 Welcome drink

Wednesday, 6 April

08:40 → 10:40 Parallel Session T01: Initial state physics and approach to thermal equilibrium: II

Convener: Steffen A. Bass (Duke University)

08:40 Anisotropic flow fluctuations relative to participant and spectator planes in heavy-ion collisions with ALICE

Measurements of anisotropic flow in heavy-ion collisions are key to extract properties of the quark-gluon plasma (QGP). The combination of different flow harmonics relative to the participant and spectator planes provides a unique insight into the initial conditions and the space-time evolution of such collisions. In particular, the spectator plane provides novel information about the three-dimensional orientation of the colliding system. We report on the centrality and transverse momentum dependence of anisotropic flow coefficients $v_n$ measured at the central pseudorapidity region relative to the participant, using the cumulant method, and newly also the spectator planes in Pb-Pb and Xe-Xe collisions. In ALICE, the spectator plane is reconstructed from the deflection of neutron spectators using the Zero Degree Calorimeters. The scaling of ratios of $v_2$ to eccentricities of the initial state $\varepsilon_2$ with entropy density in Xe-Xe and Pb-Pb collisions are shown, which quantify non-linear effects of the QGP hydrodynamic evolution. The ratio of $v_2$ relative to the spectator plane and $v_2$ relative to the participant plane is compared to ratios of the corresponding eccentricities predicted by models of the initial state. The transverse momentum dependence of the shape of flow fluctuations, specifically the skewness and kurtosis, is presented, which allows to probe its modification inside the QGP through the comparison to hydrodynamic models.

Speaker: Lukas Kreis (GSI - Helmholtzzentrum für Schwerionenforschung GmbH (DE))

QM2022.pdf

09:00 Constraints on neutron skin thickness and nuclear deformations using relativistic heavy-ion collisions from STAR

RHIC's capability to perform relativistic collisions of various ion species provides a unique opportunity to explore and constrain neutron skin thickness and deformation parameters of nuclei.

The study of neutron skin thickness $\Delta r_{np}$ of nuclei can help us directly infer nuclear symmetry energy. Such information is of critical importance to the equation of state of dense nuclear matter in neutron stars and the medium formed in heavy-ion collisions. The $\Delta r_{np}$ has traditionally been measured in low-energy hadronic and nuclear scattering experiments over decades. An alternate recent measurement using parity-violating electroweak interactions by the PREX-II experiment has yielded a large neutron skin thickness of Pb nucleus [1] that is in tension with the world-wide data established in hadronic collisions. In isobar collisions at relativistic energies, the effect of neutron skin was predicted [2] to yield different multiplicities and elliptic flows. They, in turn, provide an unconventional but more precise method to probe the neutron skin [3]. The idea is to compare the produced hadron multiplicities ($N_{\rm ch}$) [3], the mean transverse momenta ($\langle p_\mathrm{T}\rangle$) [4], and the net charge multiplicities ($\Delta Q$) [5] to trace back to the neutron skin differences between the isobar nuclei.

Nuclear deformation, a ubiquitous phenomenon for most atomic nuclei, reflects collective motion induced by the interaction between valence nucleons and shell structure. In most cases, the deformation has a quadrupole shape that is characterized by overall strength $\beta_2$ and triaxiality $\gamma$, and/or an octuple shape $\beta_3$. In relativistic collisions of two nuclei such deformations enhance the fluctuations of bulk observables that are sensitive to initial state geometry [6]. The deformation parameters can be constrained from the precision measurements of the ratios of harmonic anisotropy coefficients $v_2$, $v_3$, mean transverse momentum $[p_\mathrm{T}]$ fluctuations (mean, variance and skewness), and their Pearson correlation coefficient $\rho(v_n^2,[p_\mathrm{T}])$ between two isobar systems [7]. In Au+Au and U+U collisions the same can be done by performing measurement of $v_2$, cumulants of $[p_\mathrm{T}]$ distributions, and $\rho(v_n^2,[p_\mathrm{T}])$ [8].

In this talk we will discuss the aforementioned measurements in Au+Au, U+U and isobar $^{96}$Ru+$^{96}$Ru and $^{96}$Zr+$^{96}$Zr collisions at $\sqrt{s_{NN}}=200$ GeV using the STAR detector. We will discuss how we extract the neutron skin thickness and the symmetry energy slope parameter from these data. We will contrast our results in the context of the global data on symmetry energy and tension with the PREX-II data. We will discuss how the significant deviations of the ratios of $v_2$ and $v_3$ from unity in isobar collisions are indicative of large quadrupole and octuple deformations in Ru and Zr nuclei, respectively [9]. We will also discuss how the relative enhancement of $[p_\mathrm{T}]$-skewness, sign-change of $[p_\mathrm{T}]$-kurtosis and the suppression of $\rho(v_n^2,[p_\mathrm{T}])$ in U+U relative to Au+Au collisions are consistent with a large prolate deformation of the uranium nuclei.

~\

[1]~D. Adhikari et al. (PREX Collaboration), Phys. Rev. Lett. 126, 172502 (2021), arXiv:2102.10767 [nucl-th].

[2]~H. j. Xu, X. Wang, H. Li et al., Phys. Rev. Lett. 121, 022301 (2018), arXiv:1710.03086 [nucl-th].

[3]~H. Li, H. j. Xu, Y. Zhou et al., Phys. Rev. Lett. 125, 222301 (2020) arXiv:1910.06170 [nucl-th].

[4]~H. j. Xu, W. Zhao, H. Li et al., arXiv:2111.14812 [nucl-th].

[5]~H. j. Xu, H. Li, Y. Zhou et al., Phys. Rev. C 105, L011901 (2022), arXiv:2105.04052 [nucl-th].

[6]~C. Zhang and J. Jia, Phys. Rev. Lett. 128, 022301 (2022), arXiv:2109.01631 [nucl-th].

[7]~J. Jia and C. J. Zhang, arXiv:2111.15559 [nucl-th].

[8]~J. Jia, S. Huang and C. Zhang, Phys. Rev. C 105, 014906 (2022), arXiv:2105.05713 [nucl-th].

[9]~M. Abdallah et al. (STAR Collaboration), Phys. Rev. C 105, 014901 (2022), arXiv:2109.00131 [nucl-ex].

Speaker: Haojie Xu (Huzhou University)

QM2022_HaojieXu_STAR.pdf

09:20 Thermalization of non-abelian plasmas at next-to-leading order

The far-from-equilibrium non-abelian plasma is created in the early stage of heavy-ion collision. The “bottom-up” mechanism is the well-studied phenomenological description of its approaching to thermal equilibrium, but has been restricted to leading order coupling within kinetic theory calculation. In our recent work, we provide a next-to-leading-order (NLO) weak-coupling description of the thermalization process of far-from-equilibrium non-abelian plasmas. Starting from either over- or under-occupied initial conditions, we follow their time evolution towards thermal equilibrium by numerically solving the QCD effective kinetic equation at NLO accuracy for isotropic non-abelian plasmas . It turns out that the NLO corrections remain well under control for a wide range of couplings and that the overall effect of NLO corrections is to reduce the time needed to reach thermal equilibrium in the systems considered.
Reference:arXiv:2110.01540 [hep-ph]

Speaker: Yu Fu (Central China Normal University )

YuFu_QM2022.pdf

09:40 Development of transverse flow for small and large systems in conformal kinetic theory

We employ an effective kinetic description to study the space-time dynamics and development of transverse flow of small and large collision systems. By combining analytical insights in the few interactions limit with numerical simulations at higher opacity, we are able to describe the development of transverse flow from very small to very large opacities, realised in small and large collision systems. Surpisingly, we find that deviations between kinetic theory and hydrodynamics persist even in the limit of very large interaction rates, which can be attributed to the presence of the early pre-equilibrium phase. We discuss implications for the phenomenological description of heavy-ion collisions and the applicability of viscous hydrodynamics to describe small and large collision systems.
[1] V.Ambrus, S.Schlichting, C.Werthmann arXiv:2109.03290

Speaker: Clemens Werthmann

QM_talk_Werthmann.pdf

10:00 Bayesian inference of the fluctuating proton shape

Determining the multi dimensional structure of protons and nuclei at high energy is one central goal of the future Electron-Ion Collider. This fundamental information is a crucial input for models describing the initial state of heavy ion collisions. In particular the event-by-event fluctuating proton geometry should have a strong effect on the flow and multiplicity distribution in high multiplicity proton-proton and proton-nucleus collisions [1], assuming that a strongly interacting medium is formed in these events. Understanding the subnucleon structure to a high degree of precision is thus a prerequisite of determining whether quark gluon plasma is created in small system collisions.

In order to extract the proton shape fluctuations (see [2]) from HERA exclusive vector meson production data in a statistically rigorous manner, we apply Bayesian inference[3]. This approach enables us to extract likelihood distributions for the non-perturbative parameters describing the proton fluctuating profile, including their correlations. The resulting posterior distributions allow for a systematic propagation of uncertainties when simulating for example high-multiplicity proton-proton and proton-nucleus collisions.

We determine how accurately the HERA data can constrain the proton fluctuating shape, and illustrate how high multiplicity proton-proton collisions can provide complementary input to exclusive scattering data.

[1] H. Mäntysaari, B. Schenke, C. Shen, Phys. Lett. B 772 (2017) 681-686, arXiv:1705.03177 [nucl-th]
[2] H. Mäntysaari, B. Schenke, Phys. Rev. Lett. 117 (2016) 052301, arXiv:1603.04349 [hep-ph], H. Mäntysaari, Rep. Prog. Phys. 83 (2020), 082201, arXiv:2001.10705 [hep-ph]
[3] H. Mäntysaari, B. Schenke, C. Shen, W. Zhao, arXiv:2201.xxxxx, in preparation

Speaker: Dr Heikki Mäntysaari (University of Jyväskylä)

QM2022_talk-6.pdf

10:20 Bayesian constraints on the initial stage using Trajectum

In Bayesian analyses of heavy ion collisions up to now one usually uses the TRENTo prescription for the initial state, followed by a free streaming initial stage. In this work, we extend this picture in two ways. Firstly, we generalize the TRENTo formula so that it is able to describe binary scaling. This introduces a parameter which we subsequently use to determine whether binary scaling is compatible with experimental data. Secondly, we replace the weakly coupled free streaming initial stage by a description that interpolates between weak and strong coupling, where a parameter controls the interpolation. As with the first extension, we confront the model with data, to determine whether data favors a weakly or strongly coupled initial stage.

Speaker: Govert Nijs (Massachusetts Institute of Technology)

trajectumtalk.pdf

08:40 → 10:40 Parallel Session T03: QCD matter at finite temperature and density: II

Convener: Piotr Bozek (AGH University of Science and Technology)

08:40 Detecting critical points from Lee-Yang edge singularities in lattice QCD

A new approach is presented to explore the singularity structure of lattice QCD in the complex chemical potential and fugacity plane [1, 2, 3]. Our method can be seen as a combination of the Taylor expansion and analytic continuation approaches. Its novelty lies in using rational (Padé) approximants for studying Lee Yang edge singularities, which provide valuable insights to the occur- rence of critical phenomena in the thermodynamic limit. Several numerical experiments have been performed to test and demonstrate its accuracy and stability.
We present a calculations of the densities of conserved charges as well as chiral condensates as a function of imaginary baryon number chemical potential, obtained with highly improved staggered quarks (HISQ) at temporal lattice extent of $N_\tau=4,6,8$. We construct various rational function approximations of the lattice data and discuss how the closest singularities in the complex plane can be determined from them. We confirm stability of our results under conformal mappings. We discuss the universal scaling behavior of the Lee-Yang edge singularity and its role as a brunch-cut singularity in the order parameter. We apply the scaling in the vicinity of the Roberge-Weiss and chiral phase transitions. We find a temperature scaling that is in accordance with the expected power law behavior and determine some previously unknown non-universal constants. Finally we discuss the possibility to detect also the QCD critical end-point, if it exists, by this new method.

References

1. P. Dimopoulos, L. Dini, F. Di Renzo, J. Goswami, G. Nicotra, C. Schmidt, S. Singh, K. Zambello and F. Ziesché, “A contribution to understanding the phase structure of strong interaction matter: Lee-Yang edge singularities from lattice QCD,” [arXiv:2110.15933 [hep-lat]].
2. S. Singh et al. [Bielefeld-Parma], “Lee-Yang edge singularities in lattice QCD : A systematic study of singularities in the complex μB plane using rational approximations,” [arXiv:2111.06241 [hep-lat]].
3. G. Nicotra, P. Dimopoulos, L. Dini, F. Di Renzo, J. Goswami, C. Schmidt, S. Singh, K. Zambello and F. Ziesche, “Lee-Yang edge singularities in 2+1 flavor QCD with imaginary chemical potential,” [arXiv:2111.05630 [hep-lat]].

Speaker: Christian Schmidt (Bielefeld University)

Schmidt_qm2022.pdf

09:00 Electric charge fluctuations from the lattice

Fluctuations of conserved charges in a grand canonical ensemble
can be computed on the lattice and, thus, provide theoretical
input for freeze-out phenomenology. Electric charge fluctuations
and the corresponding higher order correlators are extremely
difficult, suffering form the most severe lattice artefacts.
We present new simulation data with a novel discretization where
these effects are strongly suppressed and provide continuum
extrapolated results in the temperature region of the chemical
freeze-out.

Speaker: Szabolcs Borsanyi

qm22_charge.pdf

09:20 (Non-)perturbative jet dispersion in hot QCD

Jet-medium interactions in the Quark-Gluon Plasma can receive large non-perturbative infrared contributions. These contributions affect transverse jet momentum broadening and jet quenching. Both are influenced by the modified in-medium dispersion of jets encoded in their asymptotic mass.
An IR-safe computation of the latter requires subtracting the unphysical UV limit of electrostatic QCD (EQCD), a long distance EFT of thermal QCD, and supplying the correct UV limit obtained from Minkowski-time QCD. We perform the first step of this procedure in calculating the necessary operators in EQCD both analytically and on the lattice. We find compelling agreement of the two methods in the ultraviolet regime.

Speaker: Philipp Schicho (Helsinki Institute of Physics)

schicho_qm22.pdf

09:40 Moat Regimes and their Signatures in Heavy-Ion Collisions

Dense QCD matter can exhibit spatially modulated regimes. They can be characterized by particles with a moat spectrum, where the minimum of the energy is over a sphere at nonzero momentum. Such a moat regime can either be a precursor for the formation inhomogeneous condensates, or signal a quantum pion liquid. We discuss the underlying physics of the moat regime based on studies in low-energy models and preliminary results in QCD. Heavy-ion collisions at small beam energies have the potential to reveal the rich phase structure of QCD at low temperature and nonzero density. We show how moat regimes can be discovered through such collisions. Particle production is enhanced at the bottom of the moat, resulting in a peak at nonzero momentum, instead of zero, in the particle spectrum. Particle number correlations can even increase by several orders of magnitude at nonzero momentum in the moat regime.

Speaker: Dr Fabian Rennecke (Giessen University)

QM2022_Rennecke.pdf

10:00 The Gluon Exchange Model for Baryon Stopping

We propose a new model for a homogeneous description of hadron-hadron, hadron-nucleus and nucleus-nucleus collisions, the Gluon Exchange Model (GEM). While technically our model can be regarded as a generalization of the Dual Parton Model by Capella and Tran Thanh Van, it is fundamentally based on the number of exchanged color octets (gluons) and significantly extends the Fock space of states available for the participating protons and nucleons.

In proton-proton collisions we provide an exact description of the final state proton and neutron spectrum. What is remarkable is that unlike the original DPM, GEM successfully describes the proton "diffractive peak" at high rapidity.

In proton-nucleus reactions we propose a statistical scheme for the process of soft color octet (gluon) exchange, based on the assumption that probabilities to form an effective diquark are equal for all allowed pairs of quarks. The latter effective diquark can form either from two valence, one valence and one sea, or from two sea quarks. Consequently we calculate the probabilities for different color configurations involving diquarks of valence-valence, valence-sea and sea-sea type. These probabilities appear to depend on the number of exchanged gluons, which results in increasing baryon stopping as a function of the number $N$ of proton-nucleon collisions in the nucleus. As such, the baryon nuclear stopping power appears to be governed by the emergence of new color configurations as a function of $N$ rather than by the energy loss of the original valence diquark.

The advantage of our approach lies in its high predictive power which makes it verifiable by the new, precise data on proton and neutron production from the CERN SPS. The latter verification, a set of predictions for the $N$-dependence of the baryon stopping process, and a discussion of implications for proton-oxygen collisions planned at the LHC, will be included in the talk.

References:

[1] M. Jeżabek and A. Rybicki, Phys. Lett. B816, 136200 (2021).

[2] M. Jeżabek and A. Rybicki, 2111.03401 [nucl-th].

Speaker: Andrzej Rybicki (Polish Academy of Sciences (PL))

Jeżabek_Rybicki_qm22_format4x3.pdf

Jeżabek_Rybicki_qm22.pdf

10:20 Search for the elusive jet-induced diffusion wake in Z/$\gamma$-jets with 2D jet tomography in high-energy heavy-ion collisions

Jet-induced medium response carries the information for the properties of quark gluon plasma produced in high-energy heavy-ion collision. Diffusion wake as an unambiguous part of the medium response will lead to a depletion of soft hadrons in the opposite direction of the jet propagation. New experimental data on Z-hadron correlation in Pb+Pb collisions at the Large Hadron Collider show, however, an enhancement of soft hadrons in the direction of both the Z and the jet. Using a coupled linear Boltzmann transport and hydro model, we demonstrate that medium modification of partons from the initial multiple parton interaction (MPI) gives rise to a soft hadron enhancement that is uniform in azimuthal angle that can overwhelm the signal of the diffusion wake. To make the effect of diffusion wake visible in the near-side Z-hadron correlation, we use a mixed-event procedure to subtract the contribution from MPI. We further employ the longitudinal and transverse gradient jet tomography for the first time to localize the initial jet production positions in Z/$\gamma$-jet events in which the effect of the diffusion wake is apparent in Z/$\gamma$-hadron correlation even without the subtraction of MPI.

Speaker: WEI CHEN (CCNU)

QM2022v1-Chen.pdf

QM2022v1-Chen.pdf

QM2022v1-Chen.pptx

08:40 → 10:40 Parallel Session T04: Jets, high-pT hadrons, and medium response: II

Convener: Krzysztof Kutak (Instytut Fizyki Jadrowej Polskiej Akademii Nauk)

08:40 Study of path-length dependent energy loss of jets in p-Pb and Pb-Pb collisions with ALICE

It is well established that hard partons lose energy as they traverse the quark-gluon plasma (QGP). However, while there has been significant work to describe the mechanism by which this occurs, the relative contributions of the microscopic processes have yet to be constrained experimentally. One way to address this question is to exploit the theoretically derived relationship between the parton energy loss mechanism and its associated path-length dependence. The ALICE experiment has taken a multipronged approach to studying this path-length dependence in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV by exploring the link between soft and hard observables. These efforts include the incorporation of flow-like observables into traditional jet measurements, as well as jet-like correlations.

This talk will present the $v_{2}$ measurement for charged particles at midrapidity in p-Pb and Pb-Pb collisions, which show significant non-zero values from high to low $\it{p}_{\rm T}$ for the first time that may be due to path-length dependent jet quenching. Jet yields measured with Event-Shape Engineering selections, which use the $q_{2}$ vector to classify events with varying anisotropies but similar bulk properties, will be shown to further explore this possibility. Additionally, results for correlations between hard trigger $\pi^{0}$s and recoil hadrons will be compared with respect to the event-plane angle. Jet constituent yields calculated from jet-hadron correlations with low momentum jets will also be considered.

Speaker: Caitlin Beattie (Yale University (US))

Beattie_QuarkMatter2022Slides.pdf

09:00 Measurements of the azimuthal anisotropy and substructure of jets in Pb+Pb collisions with the ATLAS detector

It has been shown that high-energy partons lose energy when traversing the hot, dense medium produced in heavy-ion collisions. However, the mechanism of the energy loss, including its dependence on the path-length of the shower in the medium and sensitivity to the jet substructure, is not fully understood. This talk presents a new measurement of single jet yields as a function of the azimuthal angle with respect to the event plane in Pb+Pb collisions at $\sqrt{s_{NN}} = 5.02$ TeV. Because partons produced at different angles with respect to the event plane traverse, on average, different path lengths of the medium, this measurement gives insight into the path-length dependence of parton energy loss. The azimuthal angle dependence of the yields is characterized by the parameter $v_n^{jet}$, which quantifies the magnitude of the modulation of the azimuthal angle distribution with respect to the $n^{th}$ order event plane. While ATLAS has previously reported the $v_2^{jet}$ in Pb+Pb at $\sqrt{s_{NN}} = 2.76$ TeV, this is the first ATLAS measurement of higher-order $v_n^{jet}$. The $v_2$, $v_3$, and $v_4$ are measured for jets with $p_T = 71-398$ GeV as a function of $p_T$ and collision centrality. A nonzero value of $v_2$ is observed in all but the most central collisions. A smaller nonzero value of $v_3$ is measured, suggesting that fluctuations in the initial state play a small but distinct role in jet energy loss.
This talk also presents measurements of jet substructure performed using various jet (de)clustering and grooming techniques. Measurements of inclusive jet suppression ($R_{AA}$) in heavy-ion collisions are presented for the first time as a function of the jet substructure using both nominal ($R=0.4$) and large-radius ($R=1.0$) jets in Pb+Pb and $pp$ collisions at $\sqrt{s_{NN}} = 5.02$ TeV. The jet substructure is characterized using the Soft-Drop grooming procedure in order to identify subjects corresponding to the hardest parton splitting in the jet. The dynamics of jet quenching is measured and presented as a function of the transverse momentum scale ($\sqrt{d_{12}}$) and the angle of the hardest splitting in the jet. These measurements provide new information about the path-length dependence of jet quenching and the sensitivity of jet suppression to its substructure.

Speaker: Anne Marie Sickles (Univ. Illinois at Urbana Champaign (US))

sickles_040622.pdf

09:20 Study of in-medium modification of dijets in PbPb collisions at 5.02 TeV with the CMS detector

Jet quenching is a well-established signature of quark-gluon plasma formation in heavy ion collisions. Studies of the transverse momentum balance of back-to-back jets, as well as medium-induced modifications to jet shapes and fragmentation functions, provide important experimental constraints on quark-gluon plasma properties. Using a large sample of dijet events from 5.02 TeV PbPb and pp collisions recorded by CMS, we study quenching effects differentially with respect to the dijet transverse momentum balance. We use short range correlations between jets and charged particles to assess medium-induced modifications to jet substructures on each side of the dijet. The path-length dependent energy loss and energy density fluctuations are also probed using long range correlations between jets and charged particles.

Speaker: Jussi Viinikainen (Vanderbilt University (US))

jussi_dijets_quarkMatter2022_final.pdf

09:40 Jet and hadron spectra modifications in oxygen-oxygen collisions at the LHC

The upcoming run of oxygen-oxygen (OO) collisions at the LHC offers unique experimental and theoretical opportunities to address the long standing question of high-momentum rescattering (jet quenching) in small collision systems. We have demonstrated previously that even small energy loss effect can be observed in nuclear modification factor thanks to high precision pQCD baseline calculations in inclusive oxygen-oxygen collisions. However currently there is no pp reference measurement planned at OO collision energy (6.37TeV). Therefore in our recent work we analyzed the reliability of several techniques for computing jet and hadron spectra at different collision energies. We computed the ratio of spectra between different pp collision energies in perturbative QCD, which can be used to construct a reference spectrum. Alternatively, it can be interpolated from measured spectra at nearby energies. We estimate the precision of both strategies for the spectra ratio relevant to the oxygen run. Finally we propose taking the ratio of OO and pp spectra at different collision energies, which cleanly separates the experimental measurement and theoretical computation.

Refs:
1. J. Brewer, A. Huss, A. Mazeliauskas, W. van der Schee, 2108.13434
2. A. Huss, A. Kurkela, A. Mazeliauskas, R. Paatelainen, W. van der Schee, U. Wiedemann, Phys.Rev.Lett. 126 (2021) 19, 192301, 2007.13754
3. A. Huss, A. Kurkela, A. Mazeliauskas, R. Paatelainen, W. van der Schee, U. Wiedemann, Phys.Rev.C 103 (2021) 5, 054903, 2007.13758

Speaker: Dr Aleksas Mazeliauskas (CERN)

mazeliauskas_QM22_v2.pdf

10:00 Jet angularity and fragmentation measurements in heavy-ion collisions with ALICE

While a variety of jet substructure measurements have been performed in heavy-ion collisions, a unified understanding of how the QGP affects the angular and momentum structure of jets remains an open question. One of the prominent puzzles is that measurements indicate no significant modification of the jet mass in heavy-ion collisions relative to proton-proton collisions, but significant narrowing of the jet girth. In order to shed light on this puzzle, we present new systematic measurements of a flexible and perturbatively calculable class of jet substructure observables known as the jet angularities. We report angularities spanning a wide range of angular regimes, mapping the transition from girth to mass and beyond. In order to further study the momentum structure of jets, we present the first measurements of the momentum fraction carried by sub-jets reclustered from primary jet constituents. These measurements extend to higher $z$ than hadron fragmentation measurements, enabling access to a quark-dominated sample of jets and exposing new insights about soft medium-induced radiation. We compare both the jet angularity and sub-jet fragmentation distributions to a variety of theoretical implementations of jet quenching, providing critical information on the medium modifications of jets as a function of their angular and momentum structure.

Speaker: James Mulligan (University of California, Berkeley (US))

Mulligan_QM.pdf

10:20 Novel measurements of dijet quenching with ATLAS

High energy partons are well established to lose energy when traversing the hot and dense medium produced in heavy-ion collisions. This results in a modification to the transverse momentum distributions of jets, producing a phenomenon known as jet quenching. It has been previously established in Pb+Pb collisions at $\sqrt{s_\textrm{NN}}~=~2.76$~TeV that jet quenching results in significant modifications to the
transverse momentum balance of dijet pairs. More differential measurements are needed to better understand the asymmetric jet quenching observed and explore the role of energy loss fluctuations and path-length dependent energy loss.

In this talk, we report new, fully unfolded measurements of the dijet momentum balance in Pb+Pb and $pp$ collisions at $\sqrt{s_\textrm{NN}}~=~5.02$~TeV with extended kinematic reach over previous publications, as well as in Xe+Xe collisions at $\sqrt{s_\textrm{NN}}~=~5.44$~TeV.
This talk will additionally present a new observable, the nuclear modification factor of subleading and leading jets, which provides a
precise quantification of asymmetric energy loss experienced by dijets.

Speaker: Timothy Thomas Rinn (Brookhaven National Laboratory)

trinn_qm2022.pdf

08:40 → 10:40 Parallel Session T10: Baryon rich matter, neutron stars, and gravitational waves

Convener: David Blaschke

08:40 Gravitational Waves Probing Quark Matter Crossover

Crossover Scenario
If there were a first-order phase transition, some signatures could be expected, but the most challenging is an experimental confirmation of realistic crossover scenario. It is already known from the NS observations / pQCD calculations that a crossover transition to quark matter is likely to occur around 3-5 times normal nuclear density, where a slope parameter on the energy-pressure plane exhibits a significant change. The difficulty lies in the fact that the relevant density is too high even in cores of heavy NSs.

Gravitational Waves Signal
We will discuss prospects of gravitational waves to distinguish the EoSs with/without not a first-order but a crossover transition to quark matter. To this end, we will emphasize the importance of multiple observations as follows.

[Inspiral Stage]
So far, we still have to wait for the post-merger signals, and it is crucial to make analysis to clarify what we can infer from the inspiral stage (before binary NSs merge). We show the gravitational waves obtained from the numerical relativity to constrain the tidal deformation parameter from which we can make extrapolation of EOS to high density in a scenario with/without crossover.

[Post-merger Stage]
We then demonstrate the effect of crossover in the post-merger stage (after binary NSs start merging). We will report a prominent difference between two scenarios with/without crossover. The life time from the merger till the collapse into a blackhole significantly depends on the softened EOS in the dense region of 4-5 times normal nuclear density. We also quantify theoretical uncertainties from the finite-temperature extension that is parameterized by the thermal index. We point out that it is of tremendous importance to take account of the density dependence of the thermal index.

Conclusion
We can make use of already available gravitational wave signal in the inspiral stage to constrain the EOS of cold and dense matter before crossover. Since the uncertainty in this density region is sufficiently reduced (and the finite-temperature uncertainty is absent!), we can apply it to the post-merger analysis up to an hypothetical (but very likely) crossover density, which enables us to probe the crossover from the life time after the merger, which has been quantified by our simulations of the numerical relativity with the most realistic EOS.

Speaker: Prof. Kenji Fukushima (The University of Tokyo)

fukushima.pdf

09:00 QCD in the cores of neutron stars

I discuss the recent progress in state-of-the art perturbative QCD calculations of the equation of state at large chemical potential. I describe why these calculations that are reliable at asymptotically high densities constrain the equation of state at neutron star densities, and describe how the theoretical calculations can be confronted with multimessenger observations to empirically determine the equation of state. I argue that the properties of the EOS reflect the underlying phase structure and may be used to determine the phase of matter in the cores of neutron stars.

Speaker: Mr Oleg Komoltsev (University of Stavanger)

qm2022_komoltsev.pdf

09:20 Reconciling multi-messenger constraints with chiral symmetry restoration

In this talk, we analyze the recent astrophysical constraints in the context of a hadronic equation of state (EoS), in which the baryonic matter is subject to chiral symmetry restoration. We show that it is possible to reconcile the modern constraints on the neutron star (NS) radius and tidal deformability (TD). We find that the softening of the EoS (required by the TD constraint) followed by a subsequent stiffening (required by the $2~M_\odot$ constraint) is driven by the appearance of $\Delta$ matter due to partial restoration of chiral symmetry. Sufficiently early onset of $\Delta$ matter lifts the tension with TD from GW170817. We argue that a purely hadronic EoS that accounts for the fundamental properties of quantum chromodynamics (QCD) linked to the dynamical emergence of parity doubling with degenerate masses can be fully consistent with the nuclear and astrophysical constraints. Therefore, the conclusion about the existence of quark matter in the stellar core may be premature.

Speaker: Michał Marczenko

talk_marczenko.pdf

09:40 Mirror neutron stars: how QCD can be used to study dark matter through gravitational waves

Given the lack of empirical evidence of weakly interacting dark matter, it is reasonable to look to other candidates such as a confining dark sector with a similar number of particles as the standard model. Twin Higgs mirror matter is one such model that is a twin of the standard model with particles masses 3-6 times heavier than the standard model that solves the hierarchy problem. This generically predicts mirror neutron stars, degenerate objects made entirely of mirror nuclear matter. We find their structure using a realistic equation of state from crust (nuclei) to core (relativistic mean-field model) and scale the particle masses using lattice QCD results. We find that mirror neutron stars have unique signatures that are detectable via gravitational waves and binary pulsars, suggesting an impressive discovery potential and ability to probe the dark sector.

Speaker: Mauricio Hippert Teixeira (University of Illinois at Urbana-Champaign)

TalkHippertQM22_v3.pdf

10:00 Precision studies of the strong interaction in $\Lambda$-hadron systems up to $S = -3$ with ALICE

The strong interaction among stable and unstable hadrons is a fundamental question in nuclear physics and a key ingredient for the description of the equation of state and the understanding of the structure of dense stellar objects such as neutron stars. Traditional measurements, including scattering and hypernuclei experiments, are insufficient to provide stringent constraints to the theoretical modeling of the interaction between hadrons containing strangeness. Two-particle correlation measurements are a prominent tool to probe the strong interaction with high precision even in the multi-strangeness sector. The ALICE Collaboration has demonstrated that high-multiplicity pp collisions are particularly well suited due to the enhanced production of strangeness in such collisions. Combined with the excellent tracking and particle identification capabilities of the ALICE detector, precision studies of the strong interaction among strange hadrons are feasible. The present contribution will discuss the latest ALICE results on the study of p-$\Lambda$ ($S = -1$), $\Lambda$-K$^-$ ($S = -2$) and $\Lambda$-$\Xi^-$ ($S = -3$) interaction, which provide the most rigorous constraints in this field, and their interpretation in the context of the available theoretical predictions. The impact of these results on the equation of state of neutron stars is discussed.

Speaker: Valentina Mantovani Sarti (Technische Universitaet Muenchen (DE))

QM22_VMS.pdf

10:20 Early quark deconfinement in compact star astrophysics and heavy-ion collisions at NICA/FAIR*)

We outline the role that an early deconfinement phase transition from normal nuclear matter to a color superconducting quark-gluon plasma phase plays for the phenomenology of supernova explosions and binary neutron star mergers. To this end we extend the compact star equation of state (EoS) from vanishing to moderately high temperatures that become accessible in the BM(a)N and MPD experiments at NICA as well as for CBM at FAIR. We study the connection of such hybrid EoS with the mass-radius relation of cold compact stars, including the intriguing possibility of additional families, as a consequence of the presence of an early and strong phase transition. Special emphasis is devoted to the simultaneous fulfillment of the new NICER mass and radius constraint from PSR J0740+6620 and the tidal deformability constraint from GW170817 which require the EoS to be soft at about twice saturation density and then to stiffen. Such a pattern is provided by anBlaschke early and strong deconfinement transition. Dynamical scenarios are being considered, such as binary compact star mergers including the subsequent emission of gravitational waves and supernova explosions of massive supergiant stars where neutrinos play the role of messengers.

*) This work is supported by NCN under grant number 2019/33/B/ST9/03059.

Speaker: Oleksii Ivanytskyi (University of Wroclaw)

Ivanytskyi.pdf

10:40 → 11:10 Coffee break

11:10 → 12:10 Parallel Session T02: Chirality, vorticity and spin polarization: II

Convener: Dirk Rischke (University Frankfurt)

11:10 Relativistic spin hydrodynamics with torsion and linear response theory for spin relaxation

Using the second law of local thermodynamics and the first-order Palatini formalism, we formulate relativistic spin hydrodynamics for quantum field theories with Dirac fermions, such as QED and QCD, in a torsionful curved background. We work in a regime where spin density, which is assumed to relax much slower than other non-hydrodynamic modes, is treated as an independent degree of freedom in an extended hydrodynamic description. Spin hydrodynamics in our approach contains only three non-hydrodynamic modes corresponding to a spin vector, whose relaxation time is controlled by a new transport coefficient: the rotational viscosity. We study linear response theory and observe an interesting mode mixing phenomenon between the transverse shear and the spin density modes. We propose several field-theoretical ways to compute the spin relaxation time and the rotational viscosity, via the Green-Kubo formula based on retarded correlation functions.

Speaker: Masaru Hongo (RIKEN)

Hongo_QM22.pdf

11:30 QGP smoke rings in relativistic p+A collisions

Observations of strong azimuthal anisotropies ($v_n$)-- and their agreement with some hydrodynamic calculations-- in p+A collisions at RHIC and LHC have led to the suggestion that such collisions produce the smallest droplets of QGP. This hypothesis may be tested from a different angle through hyperon polarization measurements. In particular, central p+A collisions may naturally produce an initial state in which the longitudinal flow pattern depends on the transverse radial coordinate. The generic response of any fluid to such an initial condition is the generation of expanding vortical toroids--smoke rings. We use 3D viscous hydrodynamics (implemented in the MUSIC framework) to explore these unique structures in p+A collisions. We present an experimental observable which probes for their existence and provide quantitative predictions as a function of collision energy and system size. The effects of "lumpy" initial states, various definitions of vorticity, and newly-discovered symmetric shear terms will be discussed. Finally, experimental challenges for observing this unique structure will be discussed.

Speaker: Michael Lisa

LisaQMapril2022.pdf

LisaQMapril2022.pdf

LisaQMapril2022.pptx

11:50 Investigating cold nuclear matter effects in charmonia and Drell-Yan processes at the fixed-target COMPASS experiment

Suppression of charmonia is one of the most distinctive signatures of Quark-Gluon Plasma (QGP) in heavy-ion collisions. Suppression can also take place in hadron-nucleus collisions due to cold nuclear matter (CNM) effects where the presence of QGP is not expected. The hadron-nucleus collisions are therefore important as they help to disentangle the effects of the QGP from those due to CNM. Charmonium production in hA collisions at fixed-target energies is sensitive to the effects of nPDF and the partonic energy loss in nuclear matter. It is conveniently complemented by the well-known Drell-Yan process.

The double differential ($x_{\rm F}$, $p_{\rm T}$) cross-sections of J/$\psi$ production and Drell-Yan process have been measured by the COMPASS collaboration in hA collisions at $\sqrt{s} = 18.9$ GeV. A negative pion beam with a momentum of 190 GeV/c was impinging on ammonia, aluminum, and tungsten targets. The preliminary results for the ratios of heavy to light targets for both charmonia production and Drell-Yan show suppression towards high $x_{\rm F}$. A dependence with $p_{\rm T}$ is also investigated, which might indicate the presence of energy loss effects. COMPASS findings on the nuclear effects of the J/$\psi$ production and Drell-Yan process will be presented. The results will be compared to the available fixed-target and collider measurements in order to explore scaling behavior and energy dependence and will be followed by the comparison with theoretical model predictions.

Speaker: Dr Anisa Khatun (CEA, Paris-Saclay University)

11:10 → 13:10 Parallel Session T05: QGP in small and medium systems: I

Convener: Tuomas Lappi

11:10 News on strangeness production from NA61/SHINE

NA61/SHINE is a fixed target experiment at the CERN Super Proton Synchrotron. The main goals of the experiment are to discover the critical point of strongly interacting matter and to study the properties of the onset of deconfinement. In order to reach these goals, a study of hadron production properties is performed in nucleus-nucleus, proton-proton and proton-nucleus interactions as a function of collision energy and size of the colliding nuclei. The experiment has recently completed data acquisition for its original programme on strong interactions. The Collaboration has gathered rich data in a two-dimensional scan: varying the beam energy and the sizes of colliding nuclei.
In this talk, the new results on identified charged kaon production in the intermediate size system (40Ar+45Sc and 7Be+9Be) collisions at SPS beam momentum range (13𝐴-150𝐴 GeV/𝑐) will be shown. Additionally, the new measurements of strange resonances (K0∗(892), Ξ0(1530) and Ξ(1530)) and strange baryons (Ξ-(1321), Ξ+(1321)) produced in p+p interactions will be presented. The kinematic distributions and measured multiplicities of identified hadrons will be compared with available world data and relevant models in the context of collision energy and system size dependence.

Speaker: Maciej Piotr Lewicki (Polish Academy of Sciences (PL))

qm22_ml.pdf

11:30 Two-particle azimuthal correlations in photo-nuclear Pb+Pb collisions with ATLAS

The ultra-peripheral collisions (UPC) of relativistic heavy ion beams lead to a diverse set of photon-nucleus interactions.
The measurements of particles and their interaction produced in photo-nuclear reactions can shed light on the QCD dynamics of novel, extremely asymmetric colliding systems, with energies between those available at RHIC and the LHC.
Understanding the hadronic fluctuation spectrum of the photon in this fashion is also critical for maximizing the precision of measurements at the future Electron-Ion Collider.
This talk presents the final measurement of two-particle long-range azimuthal correlations in photo-nuclear collisions using 5.02~TeV~Pb+Pb data collected in 2018 by ATLAS, with a dedicated photo-nuclear event trigger.
Candidate photo-nuclear events are selected using a combination of the single-sided zero-degree calorimeter activity and reconstructed pseudorapidity gaps constructed from calorimeter clusters and charged-particle tracks.
Correlation functions are constructed using charged-particle tracks, separated in pseudorapidity. A template fitting procedure is utilized to subtract the non-flow contribution.
Elliptic and triangular flow coefficients are presented as a function of charged-particle multiplicity and transverse momentum, and significant non-zero values of the flow coefficients are observed.
The results are compared to flow coefficients obtained in $pp$ and $p$+Pb collisions in similar multiplicity ranges, and to quantitative theoretical expectations.

Speaker: Dennis Perepelitsa (University of Colorado Boulder)

dvp-QM22-4-6-22.pdf

11:50 Observation of partonic flow in small collision systems with ALICE at the LHC

Over the last years, evidence of collective behavior has been observed in high-multiplicity collisions of small systems, however, its origin is not yet understood. In this talk, we will present the first measurement of ultra-long-range azimuthal angle correlations of identified particles in small collision systems by using forward detectors of ALICE, which allows the largest pseudorapidity separation of the particle correlations, $\Delta\eta\sim 5$, and significantly suppresses the non-flow contamination. We will show the $p_{\rm T}$-differential flow, $v_n$, of identified hadrons with many different species, over a large $p_{\rm T}$ 0.2–8 GeV/c in both p–Pb and pp collisions. Strong evidence of splitting between the $v_n$ of baryons and mesons is observed in the intermediate and high-$p_{\rm T}$ regions. Such behavior can be explained by the quark coalescence mechanism, pointing to the presence of the partonic collectivity in small systems. Furthermore, we extend measurements of the $v_n$ of non-identified particles with the requirement of presence of hard probes such as jets or leading high-$p_{\rm T}$ particles in an event (“event-scale” dependence of $v_n$), as well as with the dependence of $v_n$ over a wide rapidity range with the Forward Multiplicity Detector (up to $\Delta\eta\sim 8$) and compare results with models. To further constrain the properties of the partonic matter created in small systems, the measurement of nonlinear flow modes and the symmetric cumulants in pp, p–Pb, Xe–Xe and Pb–Pb collisions will be presented. The results are compared to a comprehensive collection of model calculations, including hydrodynamic and transport models. Finally, to investigate the origins of flow in small systems and pin down any potential contribution from initial momentum anisotropy that appears in the color glass condensate effective theory, the newly measured correlation between the mean transverse momentum and flow coefficients, $\rho(v_n^2,[p_{\rm T}])$, will be discussed. All the above measurements are based on the entire data taken from the LHC Run 2 by ALICE.

Speaker: Zuzana Moravcova (University of Copenhagen (DK))

QM_ZM.pdf

12:10 Correlation between multiparticle cumulants and mean transverse momentum in small collision systems with the CMS detector

The azimuthal anisotropies observed in small systems can originate from the final state response to the initial geometry as well as from initial momentum anisotropies. Recently it has been proposed that the correlation between the flow coefficient $v_{2}^2$ and the mean $p_\mathrm{T}$ carries information on the origin of flow in small collision systems by showing a characteristic sign change at very low multiplicity. However, this sign change exists in PYTHIA8 events as a result of nonflow effects. To reduce the nonflow dependence , a new correlator that correlates multiparticle cumulants and mean $p_\mathrm{T}$ is suggested. In this talk, we present results for this correlator using two and four particle correlations in pp, pPb and peripheral PbPb collisions. We also report our high precision measurements of $v_{2}$ using four-, six-, and eight-particle correlations, together with $v_{3}$ from four particle correlations, in both pPb and peripheral PbPb collisions. The ratios between $v_{n}$ harmonics involving different numbers of particles are compared to model calculations to study the fluctuation-driven initial state anisotropies. The results provide insights to the origin of flow in small collision systems.

Speaker: Shengquan Tuo (Vanderbilt University (US))

QM22_Tuo.pdf

12:30 Non-equilibrium dynamics and collectivity in ultra-relativistic proton-nucleus collisions

The experimental observations of anisotropic flows in proton-proton and
proton-nucleus collisions at RHIC and LHC energies has stimulated a big
interest in these small systems as a new study area for the formation and
evolution of the quark-gluon plasma. We investigate the effects of
non-equilibrium dynamics in such systems by comparing a microscopic
nonequilibrium transport approach, the Parton-Hadron-String-Dynamics
(PHSD), with a macroscopic 2D+1 viscous hydrodynamical model, VISHNew,
that describes a locally approximately equilibrated medium. The initial
conditions for the hydro evolution are taken from PHSD at different
starting times in order to study its impact on the subsequent evolution of
the short-lived QGP created in proton-nucleus collisions, investigated in
terms of energy density, viscous corrections, spatial and momentum
eccentricities. The latters have been linked to the development of
collective flows, whose origin is high-multiplicity proton-nucleus
collisions is still under debate. We address this issue also by means of a
new and more differential observable, the transverse spherocity, which
classifies final-state event topologies and allows to isolate hard and
soft effects. The investigation of such quantity in both transport and
hydro frameworks permits to gain further insights into the mechanisms
responsible for the QGP-like effects in small systems.

Speaker: Lucia Oliva (Institute for Theoretical Physics (ITP), Frankfurt am Main)

Oliva_QM2022.pdf

12:50 Search for jet quenching in high-multiplicity pp collisions using inclusive and semi-inclusive jet production in ALICE

Small collision systems exhibit features that are characteristic of collective flow, a hallmark of QGP formation. However, jet quenching in small systems has not yet been observed, and quantifying or setting limits on the magnitude of jet quenching in small systems is a key element in understanding the limits of QGP formation. In this talk we present a search for jet quenching effects in pp collisions at $\sqrt{s} = 13\ \mathrm{TeV}$ based on two jet observables: inclusive jet production, and the semi-inclusive yield of jets recoiling from a high-$p_{\rm T}$ hadron. Both measurements are carried out differentially in event multiplicity, which varies the size of the collision system. Jets are reconstructed from charged particles using the anti-$k_\mathrm{T}$ algorithm, with $R$ between 0.3 and 0.7. The $R$-dependent inclusive jet cross section is compared to pQCD calculations. To search for jet quenching effects, the shape of the inclusive jet yield in different multiplicity intervals is compared to the one obtained in minimum-bias (MB) events. The jet yield increases as a function of charged-particle multiplicity, which is similar to the one observed from soft sectors. In the semi-inclusive analysis, recoil jet acoplanarity is measured for events selected on high multiplicity (HM) and compared to the MB population. A striking modification of the acoplanarity distribution, which is nominally characteristic of jet quenching, is observed in the measured HM population. Its origin is elucidated by comparison to model calculations, with implications for the larger LHC small-systems program.

Speaker: Filip Krizek (Czech Academy of Sciences (CZ))

KrizekQM2022_v5.pdf

11:10 → 13:10 Parallel Session T06: Lattice QCD and heavy-ion collisions

Convener: Rene Bellwied (University of Houston (US))

11:10 The equation of state form Lattice QCD with finite $\mu_B$ and $\mu_S$

In this talk we extend the novel expansion scheme introduced in [1] to explore the impact of a strange and electric charge chemical potential. We focus on the equation of state along the strangness neutral line, which allows us to match conditions in heavy ion collision experiments. We are also able to extrapolate different thermodynamic quantities to values of the strangeness and electric charge densities beyond those corresponding to the strangeness neutrality conditions.

[1] S. Borsányi et al., Phys.Rev.Lett. 126 (2021) 23, 232001

Speaker: Jana N. Guenther (University of Wuppertal)

guenther_QM22.pdf

11:30 The equation of state of (2+1)-flavor QCD: An update based on high precision Taylor expansion results

Compared to the earlier calculation of the equation of state of QCD with physical light and strange quark masses, performed in 2017, the HotQCD collaboration has accumulated an order of magnitude larger statistics for up to 8th order cumulants on lattices with temporal extent Nt=8 and 12 and added results for Nt=16 that were not available previously. We use these high statistics results on Taylor expansion coefficients for an updated calculation of the equation of state in (2+1)-flavor QCD at non-zero net baryon-number density. We show that previously observed ''wiggles'' in the Taylor series for e.g. the net baryon-number, smoothen out with increasing statistics, confirming that there is no hint of a breakdown of the Taylor expansion up to baryon chemical potential $\mu_B/T=2.5$.

We compare calculations for pressure, energy and entropy densities as well as net baryon-number densities with HRG model calculations based on the recently constructed QMHRG2020 hadron list, which in addition to the hadronic resonances listed by the Particle Data Group, also includes resonances calculated in relativistic quark models. We discuss the sensitivity of the QCD equation of state to the choice of the hadron spectrum. We also provide an update for the speed-of-sound and use lattice QCD results for (2+1)-flavor QCD to discuss the sensitivity of the dip in the speed-of-sound to the occurrence of a chiral phase transition in the universality class of O(N) spin models.

Speaker: Dennis Bollweg (Columbia University)

slides.pdf

11:50 Searching for the QCD critical point along the pseudo-critical/freeze-out line using Pade-resummed Taylor expansions of cumulants of conserved charge fluctuations

One of the central goals in QCD with non-vanishing conserved charge densities is to find evidence
for the existence of the so-called critical end point (CEP) in the QCD phase diagram. Lattice QCD
calculations at smaller than physical quark masses, combined with our model based understanding of
the QCD phase diagram, suggest that this critical point, if it exists, needs to be searched for at
temperatures below $T\sim 140~$MeV. Following the rather small decrease of the QCD pseudo-critical
temperature with increasing baryon chemical potentials ($\mu_B$), it is expected that such low
temperatures will only be reached for $\mu_B\ge 400~$MeV. These large values of $\mu_B$ and low
temperatures are reached at freeze-out in heavy ion collisions only for beam energies less than 10 GeV.

In this low temperature, high density regime studies of QCD thermodynamics with straightforward
Taylor expansions are likely to fail. We extend our Taylor series expansion down to temperatures of
125~MeV and use the high statistics results for conserved charge cumulants up to 8th order, obtained
by the HotQCD collaboration, to resum Taylor expansions of the logarithm of the QCD partition function.
We will construct resumed results for cumulants of conserved charge fluctuations at low temperature and
high density and show that the diagonal Pade-approximants for 8th order Taylor series in all three conserved
charge chemical potentials can have real poles, signaling the occurrence of a phase transition, only at
temperatures below 140 MeV. This gives further support for a CEP at low temperatures.

We will use these Taylor expansions and their Pade resummations for a determination of freeze-out conditions
through QCD calculations of the mean, variance as well as the ratio of mean and variance of conserved charge
fluctuations. We compare these calculations with experimental determinations of freeze-out parameters obtained
by STAR in the BES at RHIC. In particular, we find good agreement between QCD results and the STAR measurement
of the ratio of strangeness and baryon chemical potentials. We point out that this ratio of chemical potentials
combined with the statement that freeze-out occurs close to the pseudo-critical temperature $T_{pc}(\mu_B)$
determined by ALICE and STAR is consistent with HRG model calculations only when additional strange baryon resonances
are included in the spectrum used for HRG model calculations.

Speaker: Jishnu Goswami (Bielefeld University)

qmtalk.pdf

12:10 Lattice QCD results for the heavy quark diffusion coefficient

We present a novel approach to nonperturbatively estimate the heavy quark momentum diffusion coefficient, which is a key input for the theoretical description of heavy quarkonium production in heavy ion collisions, and is important for the understanding of the elliptic flow and nuclear suppression factor of heavy flavor hadrons. In the heavy quark limit, this coefficient is encoded in the spectral functions of color-electric and color-magnetic correlators that we calculate on the lattice to high precision by applying gradient flow. In our study we consider quenched QCD at $1.5\,T_c$, where we perform a detailed study of the lattice spacing and flow time dependence of color-electric and color-magnetic correlators, and, using theoretically well-established model fits for the spectral reconstruction,
we estimate the heavy quark diffusion coefficient. Equipped with the experience obtained in quenched QCD, we estimate the heavy quark diffusion coefficient from 2+1 flavor QCD ensembles at small but finite lattice spacing.

Speaker: Luis Altenkort (Universität Bielefeld)

Luis_Altenkort_QM-2022_Lattice-QCD-results-for-the-heavy_quark_diffusion_coefficient.pdf

12:30 Computing jet transport coefficient $\hat{q}$ in lattice QCD

The jet transport coefficient $\hat{q}$ is the leading coefficient that characterizes the transverse broadening of the hard parton traversing QGP. The transverse kicks received from the medium changes the off-shellness of the hard parton, which leads to enhancement in the gluon emissions. Since the transverse broadening is the dominant mechanism responsible for the suppression of the high-transverse momentum charged-hadrons and jets, understanding the temperature and parton’s momenta dependence of $\hat{q}$ are crucial.
In this talk, we present for the first time a lattice QCD calculation of $\hat{q}$ in pure gluonic plasma and $n_{f}=3$ QCD plasma. In this formalism[1,2,3], we considered a light-like hard quark undergoing a single scattering with the plasma. $\hat{q}$ is factorized and expressed in terms of matrix elements for transverse broadening and field-strength field-strength correlator. The presence of the hard scale allows one to carry out Taylor expansion of the correlator after the analytic continuation to deep-Euclidean region. The leading twist operator in the operator-product expansion is computed on both quenched and unquenched lattices for a wide range of temperatures, ranging from 200MeV < T < 1GeV. The lattice extracted $\hat{q}$ from our formalism is compared with the existing (non) perturbative calculations and phenomenology-based extractions of $\hat{q}$. The computed $\hat{q}$ shows a temperature dependence similar to the entropy density and shows considerable agreement with phenomenology-based extractions carried out by the JET and JETSCAPE collaboration.

[1] A. Kumar, A. Majumder, J. H. Weber, arXiv:2010.14463 [hep-lat] (2020).
[2] A. Kumar, A. Majumder, C. Nonaka, PoS LATTICE2018 169 (2018).
[3] A. Majumder, Phys. Rev. C87 034905 (2013).

Speaker: Amit Kumar

AmitKumar_QM22.pdf

12:50 Scattering Theory and Hadrons Gas

In this talk I shall review how the S-matrix formalism can be applied to study the thermal properties of interacting hadrons.

The central idea of this approach is to compute an effective density of state from the scattering phase shifts. As the phase shifts encode a wealth of information about the hadronic interactions, the method can robustly handle many dynamical structures, e.g. overlapping resonances, poles and roots, and assess their influences on thermal observables.

As an application I will present an analysis on proton and Lambda yields from the heavy ion collision experiments at the LHC. I will discuss how inconsistencies between theory and experiment, e.g. the proton puzzle and the proton to Lambda ratio, may be resolved by considering some essential features of the empirical baryon spectrum. These dynamical features are also crucial for understanding the Lattice results on thermal QCD, such as the baryon electric charge correlation.

Lastly I will report on some recent progress in analyzing in-medium effects within the S-matrix formalism.

Speaker: Dr Pok Man Lo (University of Wroclaw)

qm2022_pml.pdf

11:10 → 13:10 Parallel Session T15: Future facilities and new instrumentation: I

Convener: Federico Antinori (Universita e INFN, Padova (IT))

11:10 STAR Forward Detector System Upgrade Status

The STAR Collaboration has successfully completed the upgrade of the forward detector system located between 2.5 $< \eta <$ 4.0. This upgrade comprises a Forward Calorimeter System, which contains an Electromagnetic Calorimeter and Hadronic Calorimeter; and a Forward Tracking System which consists of a Forward Silicon Tracker and Forward small-strip Thin Gap Chambers. The forward detector upgrade will have excellent detection capability for neutral pions, photons, electrons, jets, and hadrons. A combination of soft and hard probes collected during 2023-25 will be used to probe the QGP’s microstructure and will enable a unique forward physics program via the collection of high statistics Au+Au, p+Au, and pp data at $\sqrt{s_{_{\mathrm{NN}}}}$ = 200 GeV. With the extended acceptance and the enhanced statistics, STAR will be positioned to perform correlation studies in heavy-ion collisions, e.g., the pseudorapidity dependence of azimuthal correlations and the pseudorapidity dependence of global hyperon polarization. The STAR forward detector upgrade will also enable an extensive suite of measurements probing the quark-gluon structure of heavy nuclei.

In this talk, we will present the current status of the forward detector system and discuss its performance during data taking with cosmic ray and pp collisions at $\sqrt{s_{_{\mathrm{NN}}}}$ = 510 GeV.

Speaker: Xu Sun (University of Illinois at Chicago)

ForwardUpgradeStatus_QM2022.pdf

11:30 Expected performance results from upgraded LHCb and SMOG II

The LHCb experiment has recently undergone a series of major upgrades: the entire tracking system has been replaced with higher-granularity sensors, the readout electronics have been upgraded, and all hardware triggers have been removed in favor of a new state-of-the-art streaming readout system. In addition, the gaseous target SMOG system has been upgraded with a dedicated storage cell to greatly increase the rate of fixed target collisions at LHCb. This talk will include the first performance results from the new LHCb tracking system, the streaming readout system, and SMOG II, with a focus on how these upgrades directly impact the LHCb heavy ion physics program. Further upgrades planned for LHC Run 4 and 5 will also be discussed.

Speaker: Saverio Mariani (Universita e INFN, Firenze (IT))

Mariani_QM_2022_03.pdf

11:50 The ATLAS Upgrade Program

After 9 years of successful data-taking in proton-proton and heavy ion collisions at a variety of energies, the ATLAS detector started in 2018 the preparations for an ambitious physics project, aiming the exploration of very rare processes and extreme phase spaces, an endeavor that will require a substantial increase in the amount of data to be taken. To accomplish this purpose, a comprehensive upgrade of the detector and associated systems was devised and planned to be carried out in two phases. The Phase-I upgrade program foresees new features for the muon detector, for the electromagnetic calorimeter trigger system and for all trigger and data acquisition chain. These upgrades are expected to be fully functional in 2021 and will enable ATLAS to carry on its physics program at a two fold increased luminosity. For the heavy-ions program, a new Zero Degree Calorimeter (ZDC) with improved radiation hardness will be installed. Upon reaching an integrated luminosity of 350 fb-1, the LHC will undergo a new upgrade, becoming the High-Luminosity LHC (Hl_LHC). The HL-LHC will reach an instantaneous ultimate luminosity of 7.5x1034 cm-2s-1, which will enable the experiments to accumulate 4 ab-1 of integrated luminosity in about 10 years of operation. The challenges the ATLAS experiment will face during the HL-LHC stage are paramount, as it will have to cope with more than 200 simultaneous collisions per bunch crossing with many subsystems exposed to very high radiation levels. To preserve its performance, the ATLAS detector will require a major upgrade program, known as Phase-II upgrade program. During the Phase-II upgrade, a completely new all-silicon tracker with extended rapidity coverage will replace the current inner tracker detector; the calorimeters and muon systems will have their trigger and data acquisition systems fully redesigned, allowing the implementation of a free-running readout system. Finally, a new subsystem called High Granularity Timing Detector will aid the track-vertex association in the forward region by incorporating timing information to the reconstructed tracks. This presentation will summarize the expected performance of the aforementioned projects, as well as the new insights gained during the construction phase.

Speaker: Zvi Citron (Ben-Gurion University of the Negev (IL))

QM_ATLASupgrade_zcitron_final.pdf

12:10 The sPHENIX experiment at RHIC

The sPHENIX detector at the BNL Relativistic Heavy Ion Collider (RHIC) is currently under construction and on schedule for first data in early 2023. Built around the excellent BaBar superconducting solenoid, the central detector consists of a silicon pixel vertexer adapted from the ALICE ITS design, a silicon strip detector with single event timing resolution, a compact TPC, novel EM calorimetry, and two layers of hadronic calorimetry. The plan is to use the combination of electromagnetic calorimetry, hermetic hadronic calorimetry, precision tracking, and the ability to record data at high rates without trigger bias to make precision measurements of Heavy Flavor, Upsilon and jets to probe of the Quark Gluon Plasma (QGP) formed in heavy-ion collisions. These measurements will have a kinematic reach that not only overlaps those performed at the LHC, but extends them into a new, low-pT regime. sPHENIX will significantly expand the observables and kinematic reaches of these measurements at RHIC and provide a comparison with the LHC measurements in the overlapping kinematic region. The physics program, its potential impact, and recent detector development will be discussed in this talk.

Speaker: Yeonju Go (University of Colorado Boulder (US))

QM22_sPHENIX_yeonju_final.pdf

12:30 Status of the Compressed Baryonic Matter (CBM) Experiment at FAIR

The Compressed Baryonic Matter (CBM) experiment is one of the major scientific pillars of the Facility for Antiproton and Ion Research (FAIR), which is expected to become operational in 2025-26. The goal of CBM is to explore the QCD phase diagram in the region of high baryon densities using nucleus-nucleus collisions in the energy range \sqrt{s_{NN}} = 2.9 - 4.9 GeV. CBM will be utilizing peak interaction rates of up to 10 MHz and an advanced triggerless data acquisition scheme, giving access to rare physics probes not studied before.

This contribution will give an overview of the CBM physics goals among which the equation-of-state of dense nuclear matter, the possible phase transition from hadronic to partonic phase, and chiral symmetry restoration play a major role. The CBM physics performance in terms of (multi-) strange particle production, dilepton spectroscopy, collective flow and femtoscopic observables will be discussed. In addition, the status of the comprising detector sub-systems will be presented. This includes their performance in FAIR Phase-0 experiments, especially in the currently operated demonstrator mCBM at SIS18.

Speaker: Kshitij Agarwal (Eberhard Karls Universität Tübingen (DE))

20220406_Agarwal_QM2022_v02.pdf

20220406_Agarwal_QM2022_v02.pptx

12:50 Approaching first physics in NICA-MPD at JINR

The Multi-Purpose Detector (MPD) is the first experiment at the
NICA Collider, which is in construction at the Joint Institute for
Nuclear Research in Dubna. During initial stage of operation the
complex
will study collisions of heavy ions in for sqrt(s_NN) of 4-11 GeV,
with Bi+Bi collisions at 9.2 GeV, in particular planned for first run.
It is expected that an excited QCD matter with high baryonic density
will be created in these collisions. In this talk I will present the
general MPD capabilities to study this exotic state of matter.

MPD is an international collaboration consisting of 44 institutions
from 13 countries. The construction and commissioning of the detector
is planned for 2022 and 2023, with the first data expected in
2023. The status of all subsystem preparations as well as their design
performance will be presented. MPD aims to study the phase diagram of
QCD matter at maximum baryonic density, determine the nature of the
phase transition between the deconfined and hadronic matter and search
for the critical end point. The physics programme, with emphasis on
potential first physics measurements with initial beams will be
discussed and it will be shown how MPD results can be used to
characterize the QCD matter created in heavy-ion collisions, including
the relevance of these investigations to other physics areas such
as astrophysics, particle physics and neutron star composition.

The already existing Baryonic Matter at Nuclotron (BM@N) experiment is
being upgraded for measurements of Au+Au collisions up to a kinetic
beam energy of 3.8A GeV in order to investigate the equation-of-state
and the microscopic degrees-of-freedom of QCD matter at neutron star
core densities.

Speaker: Alejandro Ayala (Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico)

QM-2022-Ayala.pdf

12:10 → 13:10 Parallel Session T11: Heavy flavors, quarkonia, and strangeness production: I

Convener: Marek Kowalski (Polish Academy of Sciences (PL))

12:10 Beauty production in heavy-ion collisions with ALICE at the LHC

In this contribution, the final measurements of the centrality dependence of $R_{\rm AA}$ of non-prompt $\mathrm{D}^0$ and electrons from beauty hadron decays in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV will be presented. These measurements provide important constraints to the in-medium mass-dependent energy loss and hadronization of the beauty quark. The integrated non-prompt $\mathrm{D}^0$ $R_{\rm AA}$ will be presented for the first time and will be compared with the prompt $\mathrm{D}^0$ one. This comparison will shed light on possible different shadowing effects between charm and beauty quarks. In addition, the first measurements of non-prompt $\mathrm{D}_{s}$ production in central and semi-central Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV will be discussed. The non-prompt $\mathrm{D}_{s}$ measurements provide additional information on the production and hadronization of $\mathrm{B}_{s}$ mesons. Finally, the first measurement of non-prompt D-mesons elliptic flow in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV will also be discussed. It will help to further investigate the degree of thermalization of beauty quark in the hot and dense QCD medium.

Speaker: Xinye Peng (China University of Geosciences)

QM22_xinye_v7.pdf

12:30 Evidence for top quark production in nucleus-nucleus collisions with the CMS experiment

Evidence for the production of top quarks in heavy ion collisions is reported in a data sample of lead-lead collisions recorded in 2018 by the CMS experiment at a nucleon-nucleon center-of-mass energy of $\sqrt{s_{_{\mathrm{NN}}}} =$ 5.02 TeV, corresponding to an integrated luminosity of $1.7\pm0.1\,\mathrm{nb}^{-1}$. Top quark pair ($\mathrm{t\bar{t}}$) production is measured in events with two opposite-sign high-$p_\mathrm{T}$ isolated leptons ($\ell^\pm\ell^\mp =\,\mathrm{e}^{+} \mathrm{e}^{-},\,\mu^{+} \mu^{-},\,\mathrm{and}\,\mathrm{e}^{\pm} \mu^{\mp}$). We test the sensitivity to the $\mathrm{t\bar{t}}$ signal process by requiring or not the additional presence of b-tagged jets, and hence demonstrate the feasibility to identify top quark decay products irrespective of interacting with the medium (bottom quarks) or not (leptonically decaying W bosons). To that end, the inclusive cross section ($\sigma_\mathrm{t\bar{t}}$) is derived from likelihood fits to a multivariate discriminator, which includes different leptonic kinematic variables with and without the b-tagged jet multiplicity information. The observed (expected) significance of the $\mathrm{t\bar{t}}$ signal against the background-only hypothesis is 4.0 (5.8) and 3.8 (4.8) standard deviations, respectively, for the fits with and without the b-jet multiplicity input. After event reconstruction and background subtraction, the extracted cross sections are $\sigma_\mathrm{t\bar{t}} = 2.03 ^{+0.71}_{-0.64}$ and $2.54 ^{+0.84}_{-0.74}\,\mu\mathrm{b}$, respectively, which are lower than, but still compatible with, the expectations from scaled proton-proton data as well as from perturbative quantum chromodynamics predictions. This measurement constitutes the first crucial step towards using the top quark as a novel tool for probing strongly interacting matter.

Speaker: Luis Alcerro Alcerro (The University of Kansas (US))

QM2022.pdf

12:50 The statistical hadronization model and beauty hadrons: a case for partial equilibration of b-quarks?

We make predictions for rapidity densities of beauty hadrons produced in Pb-Pb collisions at LHC energy. The approach follows that outlined for charm in JHEP 07 (2021) 035, with the canonical suppression as an important ingredient. The hadronic mass spectrum is taken from PDG 2020, with 48 b mesons and 46 b baryons in total. As further input we use the measured cross section for $\mathrm{b\bar{b}}$ production in pp collisions at 5.02 TeV $\mathrm{d} \sigma_\mathrm{b\bar{b}}/\mathrm{d} y =34.5\pm 2.4^{+4.7}_{-2.9}\, \mu\mathrm{b}$, taken from ALICE coll. (arxiv:2102.13601) and shadowing based on reweighted nPDFs (Kusina et al, PRD, 104 (2021) 014010).

Assuming full thermalization of b-quarks at the chemical freeze-out temperature $T_{ch}$ = 156.5 MeV we overpredict the measured rapidity densities of $\Upsilon(1S)$ for central Pb-Pb collisions by a factor of 2-3. This result could indicate that a sizeable fraction of b-quarks is not thermalized.
We will discuss these results in the context of the current understanding of Debye screening scenarios for the $\Upsilon$ family and also provide new results for the production of $B_c$ hadrons.

Speaker: Anton Andronic (Westfaelische Wilhelms-Universitaet Muenster (DE))

SHMb.pdf

13:10 → 14:40 Lunch

14:40 → 17:00 Parallel Session T04: Jets, high-pT hadrons, and medium response: III

Convener: Dennis Perepelitsa (University of Colorado Boulder)

14:40 Heavy-flavour jet properties and correlations from small to large systems measured with ALICE

The early production of heavy-flavour partons makes them an excellent probe of the dynamical evolution of QCD systems. Jets tagged by the presence of a heavy-flavour hadron give access to the kinematics of the heavy partons, and along with correlation measurements involving heavy-flavour hadrons allow for comparisons of their production, propagation, and fragmentation across different systems. The properties of heavy-flavour parton showers are driven by the large dead cone of heavy quarks, the presence of which is directly measured for the first time, using jets tagged with a fully reconstructed D$^{0}$ meson amongst their constituents, in pp collisions. Whilst traversing the QGP, these partons are expected to lose energy through interactions with the medium, at a different rate to their inclusive counterparts. To constrain the energy loss in the QGP, measurements of the nuclear modification factor of D$^{0}$ meson-tagged jets are presented in the 0-10$\%$ most central Pb-Pb collisions. Properties of heavy-flavour jets are also investigated in small systems through measurements of the production and substructure of jets tagged with D$^{0}$ mesons or electrons originating from heavy-flavour decays. Measurements of the fragmentation function and radial shape of jets containing a $\Lambda^{+}_{c}$, probing different dimensions of the hadronisation dynamics of charmed baryons, are also presented in pp collisions. Additionally, measurements of D$^{0}$-hadron correlations and the correlation of electrons from heavy-flavour decays with hadrons are presented, in both pp and p-Pb collisions, probing the impact of cold nuclear effects and providing a baseline for future Pb-Pb measurements.

Speaker: Marianna Mazzilli (CERN)

QM_HFjetsCorr_MM_0604.pdf

15:00 Gradient Jet Tomography in heavy-ion collisions

Transverse momentum broadening and energy loss of a propagating parton are dictated by the space-time profile of the jet transport coefficient $\hat{q}$ in a dense QCD medium. The spatial gradient of $\hat{q}$ perpendicular to the propagation direction can lead to a drift and asymmetry in parton transverse momentum distribution. Such an asymmetry depends on both the spatial position along the transverse gradient of the dense matter and path length of a propagating parton as shown by numerical solutions of the Boltzmann transport in the simplified form of a drift-diffusion equation. In high-energy heavy-ion collisions, this asymmetry with respect to a plane defined by the beam and trigger particle (photon, hadron, or jet) with a given orientation relative to the event plane is shown to be closely related to the transverse position of the initial jet production in full event-by-event simulations within the linear Boltzmann transport model. Such a gradient tomography can be used to localize the initial jet production position for a more detailed study of jet quenching and properties of the quark-gluon plasma along a given propagation path in heavy-ion collisions.

Speaker: Yayun He (South China Normal University)

QM2022_YayunHe.pdf

15:20 Dead-cone effect in b-jet shapes and the flavor dependence of in-medium shower modifications with the CMS detector

The jet quenching phenomenon, one of the signatures of the quark-gluon plasma, is well established through experimental measurements at RHIC and LHC. However, the details of the expected dependence of jet-medium interactions on the flavor of the parton initiating the shower are not yet settled. This talk presents the first b jet shapes measurements from 5 TeV PbPb and pp collisions collected by the CMS. Comparisons made with jet shapes of inclusive jets, produced predominantly by light quarks and gluons, allow experimental observations of a “dead cone” effect in suppressing in-jet transverse momenta of constituents at small radial distance R from the jet axis. A similar comparison for large distances provides insights on the role of parton mass in the energy loss and possible mass-dependence of medium response.

Speaker: Xiao Wang (University of Illinois at Chicago (US))

QuarkMatter2022_Xiao.pdf

15:40 Particle production as a function of underlying-event activity in pp, p–Pb, and Pb–Pb collisions and search for jet-like modifications with ALICE

In this contribution, the similarity between small and large collision systems will be further explored using the underlying event (UE) charged-particle density, $N_{\rm T}$ and the self-normalized version, $R_{\rm T}$. By selecting on $N_{\rm T}/R_{\rm T}$ and topological region, different microscopic processes contributing to the inclusive production can be isolated.

Final measurements of charged particle production as a function of $N_{\rm T}$ in pp, p-Pb and Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV will be presented in the toward, away and transverse regions. The UE contributions measured in the transverse region are subtracted from the toward and the away regions to search for jet-like modifications in small systems. The jet-like signals are studied both as a function of $N_{\rm T}$ and leading particle $p_{\rm T}$.

Final results of $\pi$, K and p production as a function of $R_{\rm T}$ in pp collisions at $\sqrt{s}$ = 13 TeV are presented to explore the particle species dependence. In particular, the focus will be on very low (high) $R_{\rm T}$ to isolate the ``jet'' (UE) contributions.

All the above results are compared with predictions from QCD-inspired Monte Carlo event generators such as PYTHIA and EPOS LHC.

Speaker: Antonio Ortiz Velasquez (Universidad Nacional Autonoma (MX))

QM2022_ortiz.pdf

16:00 Studies of quark-like and gluon-like contributions to jets using jet charge in pp and PbPb collisions with the CMS detector

Jets have become a prominent tool for studying properties of the quark-gluon plasma through observations of in-medium modifications of parton showers and energy loss patterns in heavy-ion collisions. These effects, termed jet quenching, were expected to depend on the color-charge and/or flavor of the parton initiating the shower. The jet charge observable, defined as the momentum-weighted sum of in-jet particle charges, is sensitive to the electric charge of the original parton and can be used to discriminate between gluon-initiated and quark-initiated jets in proton-proton collisions. In this talk, the first measurements of jet charge distributions from 5 TeV PbPb collisions compared with matching energy pp data and predictions from leading and next-to-leading-order generators. The measurements performed with the CMS experiment show no significant modification to the components of the jet charge distribution between pp and PbPb collisions.

Speaker: Olga Evdokimov (University of Illinois at Chicago (US))

QM2022_Evdokimov_final.pdf

16:20 Bayesian analysis of QGP jet transport using multi-scale modeling applied to inclusive hadron and reconstructed jet data

The JETSCAPE Collaboration reports a new determination of jet transport coefficients in the
Quark-Gluon Plasma, using both reconstructed jet and hadron data measured at RHIC and the
LHC. The JETSCAPE framework incorporates detailed modeling of the dynamical evolution of
the QGP; a multi-stage theoretical approach to in-medium jet evolution and medium response;
and Bayesian inference for quantitative comparison of model calculations and data. The multi-
stage framework incorporates multiple models to cover a broad range in scale of the in-medium
parton shower evolution, with dynamical choice of model that depends on the current virtuality
or energy of the parton.

We will discuss the physics of the multi-stage modeling, and then present a new Bayesian
analysis incorporating it. This analysis extends the recently published JETSCAPE determination
of the jet transport parameter $\hat{q}$ that was based solely on inclusive hadron suppression
data [1], by incorporating reconstructed jet measurements of quenching. We explore the
functional dependence of jet transport coefficients on QGP temperature and jet energy and
virtuality, and report the consistency and tensions found for current jet quenching modeling with
hadron and reconstructed jet data over a wide range in kinematics and $\sqrt{s}$. This analysis
represents the next step in the program of comprehensive analysis of jet quenching
phenomenology and its constraint of properties of the QGP.

[1] JETSCAPE Collaboration (S. Cao et al.), Phys. Rev. C104 (2021) 1, 024905

Speakers: Raymond Ehlers (University of California Berkeley (US)), Raymond Ehlers (LBNL and Berkeley)

2022-04-06.rehlers.jetscape_bayesian_hadron_jet.v6.pdf

16:40 Fully resummed medium-induced emissions in dynamic media

In the last few years, several frameworks have achieved the evaluation of the medium-induced gluon radiation spectrum (or rate) with all-order resummation of multiple scatterings for static media. However, conceptual and computational issues arise when embedding approaches including multiple scatterings into dynamic plasmas. In this talk, we will show several paths to overcome these difficulties and present results on the fully-resumed spectrum for longitudinally evolving media. Furthermore, we will quantify the accuracy of the different methods and analyze their performance in realistic set-ups as those employed in phenomenological analyses.

Speaker: Carlota Andres (LIP, Lisbon)

QM20222_andresc.pdf

14:40 → 17:00 Parallel Session T05: QGP in small and medium systems: II

Convener: Anton Andronic (Westfaelische Wilhelms-Universitaet Muenster (DE))

14:40 Two-Particle Correlations in Hadronic e+e- Collisions at Belle and Their Implication

We present the measurement of two-particle correlations in hadronic $e^+e^-$ collisions data collected by the Belle detector at KEKB. The clean $e^+e^-$ collision system is conducive for the unambiguous investigation of the azimuthal anisotropy of final-state charged particles found in various heavy ion and proton-proton collisions. Following up on the first examination in $e^+e^-$ annihilation events using the small archived ALEPH dataset, high-statistics Belle datasets at center-of-mass energies of $\sqrt{s} = 10.52$ GeV ($89.5 {\rm fb}^{-1}$) and 10.58 GeV on the $\Upsilon(4S)$ resonance ($333.2 {\rm fb}^{-1}$) are analyzed. The larger statistics also enables the study of very rare events of the multiplicity distribution tail. Measurements are reported as a function of the charged particle multiplicity over the full relative azimuthal angle $(\Delta \phi)$ and three units of pseudorapidity $(\Delta \eta)$. Correlation functions calculated in two coordinate systems with respect to different reference axes –– the conventional beam axis and the event thrust axis –– are measured. The thrust-reference-axis coordinate is the more natural representation for $e^+e^-$ annihilating into a quark-antiquark pair for providing sensitivity to the color activity emitted transverse to the diquark fragmentation. In this talk, we also present a qualitative understanding for the measured correlation structure based on Monte Carlo simulations. We will discuss the correlations for jet fragmentation in this low energy regime and for the special scenario of $b\bar{b}$ bound state decays.

Speaker: Yu-Chen (Janice) Chen (Massachusetts Institute of Technology)

QM2022BelleTPC.pdf

15:00 Two-particle correlation in e+e- collisions at 91-209 GeV with archived ALEPH data

The first measurement of $anti-k_{T}$ jets and two-particle angular correlations of charged particles emitted in high energy $e^+e^−$ annihilation is presented. The archived data at a center-of-mass energy of 91-209 GeV were collected with the ALEPH detector at LEP between 1992 and 2000.

At 91 GeV, no significant long-range correlation was observed in either the lab coordinate analysis or the thrust coordinate analysis, where the latter is sensitive to a medium expanding transverse to the color string between the outgoing $q\bar{q}$ pair from Z boson decays. We also present the first measurement of anti-$k_{T}$ jet energy spectra and substructures compared to various event generators, NLO, and NLL'+R resummation calculations.

The correlation functions are measured over a broad range of pseudorapidity and full azimuth as a function of charged particle multiplicity for the first time with LEP2 data. This data set provides higher event multiplicity reach up to around 50 and a chance to sample different underlying hard-scattering processes. Studies of the high energy annihilation data will expand our search for collective phenomena in $e^+e^−$ collisions to a new phase space for a potential discovery.

Speaker: Yi Chen (Massachusetts Inst. of Technology (US))

20220406_EEResult_QM2022_YiChen_v31.pdf

15:20 Study of collectivity in small systems via two-particle azimuthal correlations using high-$p_\mathrm{T}$ jets and quarkonia in pp and pPb collisions with the CMS detector

The creation of fluid-like quark-gluon plasma in small collision systems has been investigated via elliptical azimuthal anisotropy of emitted particles in these interactions. A novel search for QCD collective effects in hard probes is presented using high-$p_\mathrm{T}$ jets in 13 TeV pp collisions at CMS. Studies of short- and long-range azimuthal correlations inside a jet produced with very high-multiplicity charged daughters are presented, where the system is rotated to a new "jet frame" with the high-$p_\mathrm{T}$ jet direction being the beam z axis. We also report the first measurement of the azimuthal anisotropy for the $\Upsilon$(1S) meson in pPb collisions at 8.16 TeV. The dimuons used to reconstruct the $\Upsilon$(1S) meson are coupled with charged hadrons using the long-range two-particle correlation method. The results are discussed in terms of collectivity and modification of bottom quarks.

Speaker: Kisoo Lee (Korea University (KR))

QM_2022_KisooLee_v11.pdf

15:40 J/$\psi$ and $\psi(2S)$ production in small systems with PHENIX

The suppression of the $J/\psi$ nuclear modification factor has been seen as a trademark signature of final state effects in large collision systems for decades. In small systems, deviations of the nuclear modification from unity had been attributed to cold nuclear matter effects until the observation of strong differential suppression of the $\psi(2S)$ state in $p/d$+A collisions, which suggests the presence of final state effects. In this talk, we present results of $J/\psi$ and $\psi(2S)$ measurements in the dimuon decay channel for $p$+$p$, $p$+Al, and $p$+Au collision systems at $\sqrt{s_{NN}}$ = 200 GeV. Key results include the nuclear modification factors $R_{pA}$ as function of $p_T$ and rapidity. The measurements are compared with shadowing and transport model predictions, as well as to complementary measurements at LHC energies.

Speaker: Krista Smith (Florida State University)

QM_2022_klsmith.pdf

16:00 Open and hidden heavy-flavor production in small systems with ALICE

Measurements of quarkonia and open-heavy flavor in hadronic collisions provide a unique testing ground for understanding quantum chromodynamics (QCD). Although recently there was significant progress, our understanding of hadronic collisions has been challenged by the observation in high-multiplicity proton-proton (pp) collisions of intriguing effects, such as collective phenomena.
The excellent particle identification, track and decay-vertex reconstruction capabilities of the ALICE experiment are exploited to measure quarkonia both at midrapidity and forward rapidity, as well as open-beauty hadron production at midrapidity, the latter accessed through different analyses strategies, some of them employing machine-learning techniques.
In this contribution, the first measurements of the elliptic flow ($v_2$) of J/$\psi$ at high multiplicity as well as J/$\psi$ pair production in pp collisions at $\sqrt{s} = 13$ TeV, will be shown. A comprehensive set of new measurements of quarkonium and open-beauty hadron production in pp and p-Pb collisions will also be discussed. Among the results, we will highlight the first measurement of non-prompt D$^*$ polarization in pp collisions at 13 TeV, as well as the first measurement of non-prompt $\Lambda_c$ in pp collisions and the latest measurements of b-tagged jets, non-prompt D mesons and non-prompt J/$\psi$ in pp and p-Pb collisions, at different collision energies. Recently published inclusive quarkonium production cross sections at midrapidity and forward rapidity in pp collisions at 5 and 13 TeV will be presented as well. An overview of multiplicity dependent results in pp and p-Pb collisions, including the first analysis of non-prompt D meson fractions at midrapidity, ground and excited quarkonium states at forward rapidity, will be shown. The comparison of results with available models will also be discussed.

Speaker: Sebastien Perrin (Université Paris-Saclay (FR))

QM_SPerrin.pdf

16:20 New insights on heavy flavor dynamics and hadronization in the small-system collisions with CMS

The observation of collectivity in small hadronic collisions raises the question whether the tiny droplet of quark gluon plasma can form in systems with size significantly smaller than nucleus-nucleus collisions. Dynamics and hadronization of heavy flavor quarks in small-system collisions provide a powerful tool to address the origin of observed collective phenomena because of their early production time and sensitivity to the finite system size effect. A comprehensive study of charm (prompt $D^0$, J/$\psi$ mesons) and bottom (via non-prompt $D^0$ mesons) hadron elliptic flow in proton-proton and proton-lead collisions with the full LHC Run-2 data collected by the CMS experiment is presented, where a mass hierarchy is observed. New measurements of the charm baryon $\Lambda_c^{+}$ yields and ratios to prompt $D^0$ yields are also presented as functions of $p_\mathrm{T}$ and event multiplicity, and are directly compared with light flavor strange baryon-to-meson ratios to provide constraints on the charm hadronization in small systems. These results are compared to theoretical models, which provide crucial new insights to charm hadronization mechanisms and possible QGP medium effects in high-multiplicity small-system collisions.

Speaker: Yousen Zhang (Rice University (US))

QM22_YousenZhang_v6_final.pdf

16:40 System size dependence of particle production and collectivity from the STAR experiment at RHIC

The medium modification to particle spectra and the origin of collectivity in small collision systems are widely debated topics in our community.
To address these open questions we propose the study of particle production and collectivity for varying system sizes, presented in decreasing order (Au+Au $>$ Ru+Ru/Zr+Zr $>$ $^{3}$He+Au $>$ d+Au $>$ p+Au $>$ p+p $>$ $\gamma$+Au), available at RHIC using the STAR detector.

We present the first measurements of charged hadron yields in isobar (Ru+Ru and Zr+Zr) collisions. We perform measurements of identified particle spectra at low transverse momenta ($p_\mathrm{T}$) as a function of rapidity and event centrality. We also perform the centrality dependent measurements of nuclear modification factors ($R_\mathrm{AA}$) at high $p_\mathrm{T}$. Combined with the existing results in smaller systems (p/d+Au), these results provide an additional handle in studying system size and collision geometry dependences of the medium modification to particle production.

We also revisit the measurements of elliptic ($v_2$) and triangular ($v_3$) anisotropies in p+Au, d+Au and $^{3}$He+Au collisions at 200 GeV including a comprehensive evaluation of the non-flow effects using different subtraction methods.
In addition to the results obtained from the mid-rapidity ($|\eta|<$1), we also use the Event Plane Detectors that span over 2.1$<|\eta|<$5.1 to investigate the potential influence of longitudinal flow de-correlations in $v_n$ measurements using peripheral Ru+Ru and Zr+Zr collisions.

Our study of photonuclear ($\gamma$+Au) processes using ultra-peripheral Au+Au data can push the boundaries of small system scan at RHIC. We lastly present measurements on particle production and long-range di-hadron correlations in inclusive $\gamma$+Au-rich events that are not dominated by hadronic interactions.

Speaker: Tong Liu (Yale University)

TongLiu_QM22_final.pdf

14:40 → 17:00 Parallel Session T07: Correlations and fluctuations: I

Convener: Tomasz Bold (AGH Univ. of Science and Technology, Krakow (PL))

14:40 Tracing the emergence of collective phenomena in small systems

Event geometry and initial state correlations have been invoked as possible explanations of long-range rapidity correlations observed in high multiplicity pp and pPb collisions. We study initial state momentum correlations and event-by-event geometry in p+Pb collisions at \sqrt{s}=5.02 TeV by following the approach of extending the impact parameter dependent Glasma model (IP-Glasma) to 3D using JIMWLK rapidity evolution of the incoming nuclear gluon distribution [1].
Investigating the non-trivial rapidity dependence of the observables, we find that geometry is correlated across large rapidity intervals whereas initial state momentum correlations are relatively short range in rapidity. Based on our results, we discuss implications for the relevance of both effects in explaining the origin of collective phenomena in small systems.
[1]. B. Schenke and S. Schlichting, Phys. Rev. C, vol. 94, no. 4, p. 044 907, 2016
[2]. B. Schenke, S. Schlichting and P. Singh, Rapidity dependence of initial state geometry and momentum correlations in p+Pb collisions [to appear]

Speaker: Pragya Singh

PSingh_QM.pdf

15:00 Deuteron number fluctuations and proton-deuteron correlations in high energy heavy-ion collisions in STAR experiment at RHIC

The production mechanism of deuterons, which have a binding energy of 2.2 MeV, is a topic of current interest in high energy heavy-ion collisions, where the system undergoes kinetic freeze-out at temperatures around 100 MeV. Two possible scenarios include (a) statistical thermal process and (b) coalescence of nucleons. Cumulants of deuteron number distributions and proton-deuteron correlations are sensitive to these physics scenarios. In addition, they are also sensitive to the choice of canonical versus grand canonical ensemble in statistical thermal models.

We report the first systematic measurements of collision energy and centrality dependence of cumulants (up to fourth order) of deuteron number distributions in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 11.5, 14.5, 19.6, 27, 39, 54.4, 62.4, and 200 GeV. We will also discuss new measurements on proton-deuteron correlations. The measurements are performed in the STAR experiment at mid-rapidity ($|y|<$ 0.5) and within transverse momentum range 0.8 $< p_{T} ({\rm GeV}/c) <$ 4.0, using Time Projection Chamber and Time-of-Flight detectors. The experimental results are compared to the statistical thermal model calculations with a grand canonical, canonical ensemble, and the UrQMD model that incorporates the coalescence of nucleons close by in space and momentum to form deuterons. These theoretical comparisons with the experimental measurements provide key insights into the mechanism of deuteron production in high-energy heavy-ion collisions.

Speaker: Debasish Mallick (National Institute of Science Education and Research, India)

DtrnFluctQM22_Debasish.pdf

15:20 Net baryon cumulants in viscous hydrodynamics

A valuable tool used in the search for QCD's critical point is the computation of cumulants of conserved charge. Near this point, it is expected a sharp increase of this quantity due to divergence of correlation lengths. This calculation requires high statistics, which poses a challenge to hydrodynamics simulations, which tends to be computationally expensive. The issue can be ameliorated by means of a procedure called oversampling, i.e. one repeats the Monte Carlo step of the particlization many times for a single hydro event. However, this has the drawback of removing effects of fluctuations caused during the particlization. We use a toy model to demonstrate a method to compute cumulants (developed originally by Grassi, Hirayama and Ollitrault) in a scenario where the oversampling procedure is employed and proceed to compute it in several collision energies.

Speaker: Willian Matioli Serenone (Universidade de São Paulo)

WillianMSerenone-Cumulants-QM22.pdf

15:40 Baryon/charge cumulant ratio at second order

Fluctuations of conserved charges are important probes to explore hot and dense medium in relativistic heavy-ion collisions. In this talk we focus on the experimentally-observed second-order cumulants of baryon number and electric charge at the top RHIC energy. We compare the ratio of these cumulants with the corresponding susceptibility ratio observed in lattice QCD numerical simulations. We show that, if one assumes that the experimental results on the cumulants are thermal, the "temperature" predicted from this comparison is significantly lower than that of the chemical freezeout. We argue that this discrepancy comes from the diffusion and resonance decays. The importance of the acceptance correction of the transverse-momentum cut is also emphasized.

Speaker: Masakiyo Kitazawa

220406QM_flucBQ.pdf

16:00 Proton number cumulants and correlation functions from hydrodynamics and the QCD phase diagram

We present a dynamical description of (anti)proton number cumulants and correlation functions in heavy-ion collisions by utilizing hydrodynamics simulations [1]. The cumulants are calculated via an appropriately extended Cooper-Frye procedure describing particlization of an interacting hadron resonance gas [2] while the effects of global baryon number conservation are taken into account using a generalized subensemble acceptance method [3]. The experimental data of the STAR and ALICE Collaborations are consistent at $\sqrt{s_{\rm NN}} \geq 20$ GeV with simultaneous effects of global baryon number conservation and repulsive interactions in baryon sector, the magnitude of the latter being in line with the behavior of baryon number susceptibilities observed in lattice QCD. The STAR and HADES data at lower collision energies show indications for notable multi-particle correlations, which can indicate sizable attractive interactions among baryons due to the QCD critical point in baryon-rich region as well as the influence of volume fluctuations. We also clarify differences between cumulants and correlation functions (factorial cumulants) of (anti)proton number distribution, proton versus baryon number fluctuations, as well the effects of hadronic afterburner and multiple conserved charges.

[1] V. Vovchenko, V. Koch, C. Shen, arXiv:2107.00163
[2] V. Vovchenko, V. Koch, Phys. Rev. C 103, 044903 (2021)
[3] V. Vovchenko, arXiv:2106.13775, to appear in Phys. Rev. C

Speaker: Dr Volodymyr Vovchenko (Lawrence Berkeley National Laboratory)

VovchenkoQM2022.pdf

16:20 Probing hydrodynamics in PbPb collisions at $\sqrt{s_{_{\mathrm{NN}}}} =$ 5.02 TeV using higher-order cumulants, $v_{2}\{2k\}$ ($k=1,...,5$)

The elliptic flow harmonic $v_{2}\{2k\}$ is determined using Q-cumulants of different orders, with $k=1,...,5$, for 5.02 TeV PbPb collisions. The results were obtained using data from the CMS experiment at the LHC. The $v_{2}\{2k\}$ values show an ordering, with $v_{2}\{2\} > v_{2}\{4\} > \approx v_{2}\{6\} > \approx v_{2}\{8\} > \approx v_{2}\{10\}$. The hydrodynamics behavior of the medium can be probed with high precision using the higher order moments of the cumulant expansion. It is found that both hydrodynamics probes $\frac{v_{2}\{6\}-v_{2}\{8\}}{v_{2}\{4\}-v_{2}\{6\}}$ and $\frac{v_{2}\{8\}-v_{2}\{10\}}{v_{2}\{6\}-v_{2}\{8\}}$ are centrality dependent. This dependence is explained by introducing previously ignored higher order moments in the Taylor expansion of the corresponding generating function of the cumulants. The higher order moments, skewness, kurtosis and the new $5^{th}$ moment are expressed through the $v_{2}\{2k\}$ ($k=1,...,5$) harmonics and measured as a function of centrality. The results bring new precision to probes sensitive to initial-state fluctuations.

Speaker: Laslo Nadderd (University of Belgrade (RS))

LNadderd_QM22_v6.pdf

16:40 The imprint of conservation laws on correlated particle production

We present a novel approach to quantify correlations between baryon-antibaryon, baryon-baryon, and antibaryon-antibaryon pairs. For special case of Gaussian correlations, we used the Cholesky factorization [1] of the covariance matrix, while arbitrary correlations were introduced using the well-known Metropolis and Simulated Annealing [2] methods. Our approach is general enough to be used for correlations between strange and/or charm hadrons, it can also be applied to multi-particle final states. The results obtained are systematically compared to the corresponding publications from the ALICE and STAR collaborations. One focus of our analysis is to quantify the width of correlations in rapidity space. Such investigations are key to our understanding of the mechanism of baryon production at energy scales from several GeV to several TeV.

1. G. H. Golub and C. F. Van Loan, Matrix Computations, Johns Hopkins University Press, 1989.

2. N. Metropolis, A. W. Rosenbluth, M. N. Rosenbluth A. H. Teller and E. Teller, Equation of state calculations by fast computing machines, J.Chem.Phys. 21 (1953) 1087-1092

Speaker: Dr Anar Rustamov (GSI/NNRC)

Rustamov_QM22.pdf

14:40 → 17:00 Parallel Session T08: Strongly coupled systems

Convener: Peter Braun-Munzinger (GSI - Helmholtzzentrum fur Schwerionenforschung GmbH (DE))

14:40 Detection of medium induced parton momentum broadening using photon-tagged jets with the CMS detector

Azimuthal angle ($\Delta\phi$) and transverse momentum ($p_\mathrm{T}$) correlations of isolated photons and associated jets, which are sensitive to medium induced parton momentum broadening, are reported for the first time with the latest high statistics pp and PbPb data recorded with the CMS detector at $\sqrt{s_{_{\mathrm{NN}}}} =$ 5.02 TeV. The fully corrected photon+jet azimuthal correlation and $p_\mathrm{T}$ imbalance in PbPb collisions are studied as a function of collision centrality and photon $p_\mathrm{T}$. In addition, a novel measurement of the decorrelation of jet axes calculated with the energy weight and the winner-take-all schemes ($\delta_{jj}$) is reported for the first time. This new observable is insensitive to the initial state radiation which significantly smears the photon+jet azimuthal correlation. A significant modification of $\delta_{jj}$ is reported, which signals a direct detection of in-medium momentum broadening of the leading parton inside the jet. Furthermore, the transverse energy spectra and nuclear modification factors ($R_\mathrm{AA}$) of isolated photons will be discussed.

Speaker: Molly Taylor (Massachusetts Inst. of Technology (US))

Taylor_Molly_QM2022.pdf

15:00 New experimental frontiers in the study of many-body nuclear interactions with ALICE

Exploring the strong interaction among hadrons, the ALICE Collaboration has for the first time extended the experimental measurements from two- to three-body interactions. These measurements provide unique information on many aspects of strongly-coupled systems, like the genuine three-body interaction, the formation of light nuclei and the search for exotic bound states. Among those, many-body interactions, also including hyperons, are an important ingredient in the calculation of the equation of state of neutron stars.

The results presented in this talk are obtained using high-multiplicity pp collisions at $\sqrt{s}$ = 13 TeV measured by ALICE at the LHC. The first measured three-body correlations include p-p-p and p-p-$\Lambda$. Their genuine three-body interactions are obtained by subtracting the known two-body effects from the measured correlation functions for the triplets. In both systems, a non-zero three-particle cumulant is observed, providing a hint to the existence of a genuine three-body effect. Another class of many-body interaction studies is identified in the correlations of hadrons with light nuclei. ALICE has measured proton-deuteron (p-d) interactions, a system containing three hadrons building up a pair of a hadron and a nucleus. The experimental correlation function is compared with theoretical predictions obtained employing the scattering parameters extracted from traditional scattering experiments for the p-d system. A clear deviation is observed, which may be interpreted as a demonstration of the late formation time of (anti)deuterons in hadron-hadron collisions.

Speaker: Raffaele Del Grande (Technische Universitaet Muenchen (DE))

Talk_QM2022_DelGrande_v4.pdf

15:20 Heavy-Light Susceptibilities in a Strongly Coupled Quark-Gluon Plasma

Quark number susceptibilities as computed in lattice QCD are commonly believed to provide insights into the microscopic structure of QCD matter, in particular its degrees of freedom. We generalize a previously constructed partonic $T$-matrix approach to finite chemical potential to calculate various susceptibilities, in particular for configurations containing a heavy charm quark. At vanishing chemical potential and moderate temperatures, this approach predicts large collisional widths of partons generated by dynamically formed hadronic resonance states which lead to transport parameters characteristic for a strongly coupled system. The quark chemical potential dependence is implemented into the propagators and the in-medium color potential, where two newly introduced parameters for the thermal and screening masses are fixed through a fit to the baryon number susceptibility, $\chi^B_2$. With this setup, we calculate heavy-light susceptibilities without further tuning; the results qualitatively agree with the lattice-QCD (lQCD) data for both $\chi^{uc}_{11}$ and $\chi^{uc}_{22}$. This implies that the lQCD results are compatible with a significant content of broad $D$-meson and charm-light diquark bound states in a moderately hot QGP.

Reference:
Shuai Y.F. Liu, Ralf Rapp, arXiv:2111.13620

Speaker: Shuai Liu (Hunan University)

hlsus_QM22.pdf

15:40 ALICE determines the scattering parameters of D mesons with light-flavor hadrons

The strong interaction among D mesons and light-flavor hadrons was completely out of experimental reach until recently. The scattering parameters governing elastic and inelastic D-pion/kaon/proton collisions are completely unknown. This poses strong limitations not only to the search of molecular states composed of charm and non-charm hadrons, but also to the study of the rescattering of charm mesons following their formation in ultrarelativistic heavy-ion collisions. In such collisions a colour-deconfined medium, called quark-gluon plasma (QGP), is formed. The system experiences a hydrodynamic expansion cooling down up to the chemical freeze-out, which is followed by a hadronic phase. The knowledge of the scattering parameters of charm hadrons with non-charm hadrons would be a crucial ingredient for models based on charm-quark transport in a hydrodynamically expanding QGP to describe the typical observables of heavy-ion collisions.

In this talk we will report on the first estimation of the scattering parameters governing the strong interaction of the D-proton channel measured by the ALICE Collaboration in high-multiplicity pp collision at $\sqrt{s}$= 13 TeV at the LHC. The strong interaction is studied by means of correlation in momentum space and the analysis is extended to D-kaon and D-pion combinations. It is demonstrated that all the relevant scattering parameters for the interaction of D mesons with light-flavor hadrons will be experimentally determined thanks to the upgrades of the ALICE experimental apparatus planned for the LHC Run 4 and 5 data taking periods.

Speaker: Fabrizio Grosa (CERN)

QM22_charmfemto_fgrosa.pdf

16:00 Charm and Bottom quark energy loss and flow measurements in Au+Au collisions by the PHENIX experiment

The energy loss of quarks when travelling a QGP medium is expected to depend on their mass. Heavy quarks causes a dead cone region along the direction of the quark where no energy is lost by gluon bremsstrahlung. This effect can be measured by comparing the nuclear modification factors of hadrons made of light and heavy quarks. The heavy quark coupling with the thermalized QGP is also an important aspect in probing the thermodynamics of QGP. The coupling is studied by the measurement of the flow harmonics ($v_2$) and its dependency on the transverse momentum $p_{\rm T}$ of the probe and on the collision centrality.
The PHENIX experiment contains a set of vertex detectors which enable the measurement of the distance of the closest approach (DCA) of identified electrons and muons. By utilizing their DCAs, identification of charm and bottom semi-leptonic decays was realized in Au+Au collisions at $\sqrt{s_{NN}}$=200 GeV. The $p_{\rm T}$ and collision centrality dependence of the nuclear modification and $v_2$ for charm and bottom hadrons were thus measured at mid-rapidity region ($|\eta|<$0.35) using the large dataset from the RHIC Year-2014 run. The $p+p$ yield used as a reference was obtained via semi-leptonic decay of heavy quarks and non-prompt J/$\psi$ yield ($B\rightarrow J/\psi+X$). The final results from this work will be presented and discussed in the view of the heavy quark energy loss, its coupling to and diffusion in QGP.

Speaker: Takashi Hachiya (RIKEN)

QM2022_hf_hachiya_v4.pdf

16:20 The splitting of directed flow for identified light hadrons (\pi, K, and p) and strange baryons (\Xi and \Omega) in Au+Au and isobar collisions at STAR

In relativistic heavy-ion collisions, the directed flow ($v_1$) of hadrons can provide insights into the ultra-strong electromagnetic (EM) field~[1-2], the constituent quark content of hadrons~[3], and the role of transported quarks~[4]. Here, the first measurement is reported for rapidity-odd directed flow of $\Xi$ and $\Omega$ in Au+Au collisions at $\sqrt{s_{NN}}=$ 19.6, 27, and 200 GeV, as well as $v_1$ for identified charged hadrons with unprecedented precision in Au+Au and isobar collisions at $\sqrt{s_{NN}}=$ 200 GeV.
The coalescence sum rule is examined with various combinations of hadrons where all constituent quarks are produced. For such combinations a systematic violation of the sum rule is observed with increasing difference in the electric charge and the strangeness content of the associated constituent quarks. By comparing with the Parton-Hadron-String Dynamics model that includes an EM field, the results suggest that the constituent quark sum rule could be violated in the presence of a strong EM field that drives the $v_1$ of produced quarks and anti-quarks to opposite directions. The splitting of $v_1$ slope with rapidity ($\Delta (dv_1/dy)$) between positively and negatively charged hadrons ($\pi$, $K$, $p$) is also studied with large statistics. A clear transition of $\Delta(dv_1/dy)$ from positive in central collisions to negative in peripheral collisions is observed for protons and kaons. With the effects of both transported quarks and the EM field considered, it is found that the significant negative values in peripheral events can only be explained by the presence of an EM field with the Faraday or Coulomb effect being dominant.

[1]~U. Gursoy, et al., Phy. Rev. C {\bf{98}}, 055201 (2018).

[2]~U. Gursoy, et al., Phy. Rev. C {\bf{89}}, 054905 (2014).

[3]~A. I. Sheikh, et al., Phy. Rev. C {\bf{105}}, 014912 (2022).

[4]~Y. Guo, et al. Phys. Rev. C {\bf{86}}, 044901 (2012).

Speaker: Ashik Ikbal

qm22_slides_T08.pdf

16:40 Understanding the nature of f$_0$(980) via K$^+$K$^-$ correlation and production yield with ALICE

The f$_0$(980) resonance was observed several years ago in $\pi\pi$ scattering experiments. Despite a long history of experimental and theoretical studies, the nature of this short-lived resonance is far from being understood and there is no agreement about its quark structure. According to different models, it has been associated with a meson, considered as a tetraquark, or as a KK molecule. In this talk we address two complementary avenues to study the nature of the f$_0$(980) resonance.

The first method exploits the excellent tracking and particle identification of the ALICE experiment to measure the differential spectra and integrated yield of the f$_0$(980) meson produced in pp and p-Pb collisions at an energy of $\sqrt{s}$ = 5 TeV. The results are discussed in the comparison with models and the properties of other hadrons. The nuclear modification factor shows hints of final-state effects in p-Pb collisions and will be presented and discussed in this perspective. The second method involves femtoscopic correlations of non-identical charged kaons (K$^+$K$^-$), studied in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV. For the analysis of the K$^+$K$^-$ correlation, a comparison of the measured data to the Lednick$\acute{\rm y}$-Luboshitz interaction model allows to extract for the first time the f$_0$(980) mass and coupling parameters. The measured width and mass of the f$_0$(980) resonance are consistent with the existing PDG data.

Speaker: Neelima Agrawal (Universita e INFN, Bologna (IT))

[20220406]f0_Agrawal_QM22.pdf

17:30 → 18:30 Poster Session 1 T01

17:30 New opportunities for nuclear structure imaging in high-energy heavy-ion collisions

The hydrodynamic modeling of the quark-gluon plasma (QGP) permits us today not only to perform quantitative extractions of the transport properties of the QGP, but also to strongly constrain its initial condition. A growing body of experimental evidence shows that the QGP initial condition is strongly impacted by the shape and radial structure of the colliding nuclei. We discuss the exciting prospect of using precision flow measurements as a tool to image the structure of atomic nuclei, and show how such measurements probe the quadrupole, octupole, and triaxial deformations of the colliding ions, as well as their neutron skin. Motivated by recent groundbreaking measurements from RHIC and LHC, we discuss in particular the case of collisions of isobaric nuclei, which provide the cleanest access route to the collective structure of the colliding ions. We discuss the implications of obtaining an information about the structure of nuclei from high-energy collisions that is fully complementary to that obtained in low-energy experiments, and argue that a scan of stable isobars at high-energy colliders may open a new exciting direction of research in nuclear physics.

Speakers: Giuliano Giacalone (Universität Heidelberg), Jiangyong Jia (Stony Brook University (US))

JiangyongJia_qm2022poster.mp4

JiangyongJia_qm2022poster.pdf

17:34 Constraining early time dynamics in ultrarelativistic Heavy Ion Collisions

It is frequently supposed that quark-gluon plasma created in heavy-ion collisions undergoes free streaming at early times. We examine this issue based on the assumption that a universal attractor dominates the dynamics already at the earliest stages, which offers a way to connect the initial state with the start of the hydrodynamic expansion in an approximate but conceptually transparent fashion. We demonstrate that the centrality dependence of the measured particle multiplicities can be used to quantitatively constrain the pressure anisotropy and find that it strongly depends on the model of the initial energy deposition. As an illustration, we compare three initial state models and show that they predict rather different early-time values of the pressure anisotropy. This strongly suggests that assuming free streaming prior to hydrodynamization is not necessarily compatible with a generic initial state model and that features of the pre-hydrodynamic flow need to be matched with the model of the initial state.

Speaker: Jakub Jankowski (University of Wroclaw)

a youtube talk on the topic

QM22JJ.pdf

the reference the poster is based on

17:38 Exclusive heavy vector meson production at next-to-leading order in deep inelastic scattering

Exclusive vector meson production is a powerful process to probe the small Bjorken-$x$ structure of protons and nuclei, as such processes are especially sensitive to gluonic structure and also provide access to the spatial distribution of small-$x$ gluons in nuclei. A powerful theoretical framework to study vector meson production at high energy, and to describe the initial condition of heavy-ion collisions, is the Color Glass Condensate (CGC) effective field theory. So far, most calculations in the CGC framework have been done at the leading order. Recent theoretical developments on the NLO heavy vector meson wave function [1] and the NLO virtual photon light-front wave function with massive quarks [2,3] have made it possible to go beyond the leading order, allowing us to include the next-to-leading corrections in $\alpha_s$ and calculate exclusive heavy vector meson production at NLO in the dipole picture for the first time.

In this talk, we will present results from our recent work on longitudinal [4] and transverse [5] NLO vector meson production in the nonrelativistic limit. We demonstrate the cancellation of UV and IR divergences in the NLO calculation, which includes taking into account both the Balitsky-Kovchegov equation describing the rapidity evolution of the dipole amplitude and the renormalization of the leading-order vector meson wave function. The next-to-leading order corrections are found to be sizable; however, their numerical effect on vector meson production is compensated by the dipole amplitude, fitted to HERA inclusive cross section data at NLO [6]. Finally, exclusive $J/\psi$ production is calculated numerically and compared to the existing data. We find that both the NLO corrections and the first relativistic corrections, calculated in Ref. [7], are numerically important and result in a good agreement with the data. We demonstrate that it is possible to simultaneously compute consistently both inclusive and exclusive cross sections at NLO accuracy in the CGC framework.

[1] M. Escobedo and T. Lappi, Phys.Rev.D 101 (2020) 3, 034030, arXiv:1911.01136 [hep-ph]
[2] G. Beuf, T. Lappi and R. Paatelainen, Phys. Rev.D 104 (2021) 5, 056032, arXiv:2103.14549 [hep-ph]
[3] G. Beuf, T. Lappi and R. Paatelainen, in preparation
[4] H. Mäntysaari and J. Penttala, Phys. Lett.B 823 (2021), 136723, arXiv:2104.02349 [hep-ph]
[5] H. Mäntysaari and J. Penttala, in preparation
[6] G. Beuf, H. Hänninen, T. Lappi and H. Mäntysaari, Phys. Rev.D 102 (2020), 074028, arXiv:2007.01645 [hep-ph]
[7] T. Lappi, H. Mäntysaari and J. Penttala, Phys.Rev.D 102 (2020) 5, 054020, arXiv:2006.02830 [hep-ph]

Speaker: Jani Penttala (University of Jyväskylä (FI))

2022_QM_Penttala_Jani.pdf

17:42 Far from equilibrium hydrodynamic attractor for an azimuthally symmetric system

Hydrodynamics is an effective theory for the description of long-wavelength phenomena of fluids, that can be expressed as a small gradient expansion of fluid velocities relative to a thermal background. Thus, hydrodynamics is expected to fail for systems which are far-from-equilibrium. The medium produced in pp collisions at LHC and RHIC energies is an example of such a system. However, recent experimental results of high energy pp collision have shown evidence of collectivity similar to those observed in heavy-ion collisions. The unprecedented success of hydrodynamics to describe collectivity in heavy-ion collisions, as well as small systems, can be attributed to the fact that there exists a stable universal attractor which makes the dynamical equations to quickly converge and enter a hydrodynamic regime, at a time scale much smaller than the typical isotropization time scales. In the present work, we go beyond the previous
works which considered 1+1d longitudinal boost invariant systems, by considering a system undergoing Gubser flow which has a simultaneous transverse and longitudinal expansion.

To investigate the dynamics of such a system, the Boltzmann equation is solved in the relaxation time approximation using a hierarchy of angular moments of the distribution function. The dynamics of transition is described by the presence of fixed points which describes the evolution of the system in various stages. We found that unlike 1+1d Bjorken flow which has late-time thermalization (hydrodynamization), Gubser flow is intrinsically a 3+1d expanding system with dynamics such that the system goes from early time free-streaming regime to intermediate thermalization (hydrodynamization) and back to free-streaming in the late time regime. The attractor solution is found for various orders of moments as an interpolation between these fixed points.

Speaker: Ashutosh Dash (Frankfurt University)

QM2022_krakow_dash.pdf

17:46 Longitudinal Fluctuations in Heavy-Ion Collisions with the ALICE Detector

Event-by-event pseudorapidity distributions in heavy-ion collisions are sensitive to longitudinal fluctuations. Their shapes can be decomposed using Legendre polynomials, analogous to the Fourier decomposition for anisotropic flow. A longitudinal decomposition for Xe—Xe collisions at $\sqrt{s_{\mathrm{NN}}}=5.44$ TeV and Pb—Pb collisions $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV measured with the ALICE detector is presented for event-by-event pseudorapidity distributions and compared to models. A significant forward-backward asymmetry in the particle production is observed, which is quantified via the first-order coefficient, $a_{1}$, from the longitudinal decomposition. Such an asymmetry shows a breaking of boost invariance, which is assumed in various models that describe the initial state of a heavy-ion collision.

Speaker: Raquel Quishpe (University of Houston (US))

Quishpe_LongFluctHIC_QM22_poster.pdf

17:50 Dependence of hydrodynamic attractors on the definition of the equilibrium state

Fluid-dynamical theories are always constructed in terms of an expansion around a given, yet arbitrary, local equilibrium state. This is implemented by the choice of the so-called matching conditions which define the temperature, chemical potential, and velocity of a viscous fluid. Matching conditions are an essential feature of nonequilibrium systems and their consequences to the emergence of hydrodynamic behavior have not been explored. In particular, the interplay between matching conditions and fluid-dynamical attractors [1] are far from understood.

We investigate for the first time how fluid-dynamical attractors in Bjorken flow are affected by choices of matching conditions, considering several formulations of fluid dynamics and kinetic theory. We show that the effect considerably worsens the agreement between solutions of first-order [2] and second-order fluid dynamics [3] and kinetic theory. These results directly affect the modeling of ultrarelativistic heavy-ion collisions where a fluid dynamical approximation is thought to be valid even at early times when the system is far from equilibrium.

[1] M. Heller and M. Spalinski, Phys. Rev. Lett. 115 (2015) 7, 072501.

[2] F. S. Bemfica, M. M. Disconzi and J. Noronha, Phys.Rev.D 98, no.10, 104064 (2018).

[3] W. Israel, J. M. Stewart, Ann. of Phys., 118 (2), 341-372 (1979); G.S.Denicol, H. Niemi, E. Molnar and D. H. Rischke, Phys. Rev. D 85, 114047 (2012).

Speaker: Gabriel Denicol (Universidade Federal Fluminense)

Poster_Denicol_QM22

17:54 Coalescence Sum rule for Elliptic Flow from the RHIC Beam Energy Scan

Transverse-momentum ($p_T$) dependence of elliptic flow ($v_2$) for identified particles at the top RHIC energy has well established a number-of-constituent-quark (NCQ) scaling [1], supportive of the coalescence sum rule that determines $v_2$ of mesons and baryons as the sum of contributions from their constituent quarks. The NCQ scaling implicitly assumes that the produced drops of partonic matter are thermally equilibrated, and constituent quarks at hadronization do not remember their past history. This assumption is found to be violated with the RHIC Beam Energy Scan (BES) data [2]. In this talk, we will focus on the $p_T$-integrated $v_2$ data instead of $v_2(p_T)$, and quantitatively explain the results on $\pi^\pm$, $K^\pm$, $p$, $\bar{p}$, $\Lambda$ and $\bar{\Lambda}$ in Au+Au collisions at $\sqrt{s_{\rm NN}} = 7.7$ GeV to 62.4 GeV by differentiating quarks produced in the collision and those transported from the initial-state nuclei. After verification of the coalescence sum rule, we extract $v_2$ for both produced ($u/d/{\bar u}/{\bar d}$, $s$, and ${\bar s}$, separately) and for transported ($u/d$) quarks. The latter is found to be larger than the former, and accounts for the observed $v_2$ difference between particles and antiparticles. We also relate the $v_2$ measurements of multi-strange hadrons to the different formation times of $\phi$, $\Omega^\pm$ and $\Xi^+$. At the RHIC BES regime, although the coalescence sum rule seems to be valid and the partonic degrees of freedom are important, the produced nuclear matter may not reach a full thermal equilibrium. We will discuss the beam energy dependence of the baryon transport and its impact on thermal equilibration.

[1] J. Adams et al. (STAR Collaboration), Nucl. Phys. A 757 (2005) 102.
[2] L. Adamczyk et al. (STAR Collaboration), Phys. Rev. C 93, 014907 (2016).

Speaker: HuanZhong Huang (UCLA)

17:58 System-size dependence of particle production at mid and forward rapidity with ALICE

The rapidity dependence of particle production contains information on the partonic structure of the projectile and target and is, in particular at LHC energies, sensitive to non-linear QCD evolution in the initial state. At LHC, collision final states have been mainly studied in the central kinematic region, however, there is a rich opportunity for measurements in the forward direction, which probe the nucleon structure at small Bjorken-x values. Moreover, investigating the system-size dependence of the particle production at the same collision energy is particularly important for directly studying nuclear effects.
In the first part of the talk, the final Run 1 and 2 particle-production results at forward rapidities will be presented for pp, p-Pb, and Pb-Pb collision systems, where ALICE has unique coverage. When combined, the Forward Multiplicity and the Silicon Pixel Detectors can measure charged particles over a wide range of $-3.4<\eta<5.0$. The Photon Multiplicity Detector has complementary coverage for neutral-particle production over the kinematic range $2.3<\eta<3.9$.
In the second part of the presentation, we will introduce the upgraded Run 3 ALICE configuration. The new Monolithic Active Pixel Sensors-based Inner Tracking System allows full tracking and vertexing for $|\eta|<2.5$. When combined with the new Muon Forward Tracker, the tracking can be extended to cover $-3.6<\eta<2.5$. The performance of the new detectors and the tracking/matching algorithms will be presented for the $\sqrt{s}=900$ GeV pp pilot-beam data taking in autumn 2021.

Speaker: Anton Alkin (CERN)

QM22-Alkin-MM-system-size-poster-v2.pdf

18:02 Stability of Classical Chromodynamic Fields

A system of gluon fields generated at the earliest phase of relativistic heavy-ion
collisions can be described in terms of classical fields. Numerical simulations show that the system is unstable but a character of the instability is not well understood. With the intention to systematically study the problem, we analyze a stability of classical chromomagnetic and chromoelectric fields which are constant and uniform. We consider the Abelian configurations discussed in the past where the fields are due to the single-color potentials linearly depending on coordinates. However, we mostly focus on the nonAbelian configurations where the fields are generated by the multi-color non-commuting constant uniform potentials. We derive a complete spectrum of small fluctuations around the background fields which obey the linearized Yang-Mills equations. The spectra of Abelian and nonAbelian configurations are similar but different and they both include unstable modes. We briefly discuss the relevance of our results for fields which are uniform only in a limited spatial domain.

Speaker: Sylwia Bazak (Jan Kochanowski University)

Stability of classical.pdf

18:06 Equilibration of QCD plasmas at finite net-baryon density

We employ an effective kinetic theory of Quantum Chromo Dynamics (QCD) to study the pre-equilibrium dynamics of the Quark-Gluon Plasma (QGP) at zero and finite net-baryon density. By investigating the dynamics of the energy-momentum tensor and the conserved charges, we determine the relevant time and temperature scales for the onset of viscous hydrodynamics, and quantify the evolution of the chemical composition of the QGP at early times [1,2]. We address phenomenological consequences regarding the role of the pre-equilibrium phase at different collision energies [1], and discuss how the improved understanding of the pre-equilibrium phase can be used to constrain hot and cold nuclear matter properties from heavy-ion collisions [3].
[1] X. Du, S. Schlichting, PRL 127 (2021) 122301
[2] X. Du, S. Schlichting, PRD 104 (2021) 054011
[3] X. Du, S. Schlichting, work in progress

Speaker: Xiaojian Du (Bielefeld University)

QM2022-XiaojianDu.pdf

18:10 Probing the Weizsäcker-Williams gluon distribution with electron-dijet correlations at EIC

We propose a novel way to study the Weizsäcker-Williams gluon distribution
using the Electron Ion Collider. We examine the interplay between the effect
of the soft gluon emissions, or Sudakov effects, and gluon saturation effects
with the help of the azimuthal correlations between the total transverse
momentum of the dijet system and the scattered electron. Kinematic cuts are
imposed such that the dijet system is produced in the forward direction of the
laboratory frame, which sets an upper bound on the probed longitudinal
fractions of the hadron momentum carried by scattered gluons. Further cuts are
chosen such that they allow us to use the factorization formalism that directly
involves the unpolarized Weizsäcker-Williams gluon distribution. We find that
this observable is very sensitive to the soft gluon emission and moderately
sensitive to the gluon saturation. The former sensitivity is, however, greatly
reduced in the nuclear modification ratio when comparing proton and heavy ions
as targets, opening the possibility to disentangle Sudakov effects and
saturation effects.

Speaker: Andreas van Hameren

poster-with-white.pdf

18:14 Space-time structure of 3+1D color fields in heavy-ion collisions

We perform an analytic calculation of the 3+1D structure of the initial state in heavy-ion collisions by considering the collision of longitudinally extended nuclei in the dilute limit of the Color Glass Condensate effective field theory of high-energy QCD. Based on general analytic expressions for the color fields in the future light cone, we compute the non-trivial rapidity profiles of the transverse pressure at early times. We validate our (semi-) analytic results against non-perturbative 3+1D classical Yang-Mills simulations [2,3] and discuss prospects for the development of 3+1D initial state models based on our calculation.
[1] A. Ipp, D. Müller, S. Schlichting and P. Singh, arxiv:2109.05028
[2] S. Schlichting, P. Singh, 3-D structure of the Glasma initial state – Breaking boost-invariance by
collisions of extended shock waves in classical Yang-Mills theory, Phys. Rev. D 103 (1) (2021) 014003.
[3] A. Ipp, D. Müller, Broken boost invariance in the Glasma via finite nuclei thickness, Phys. Lett. B 771 (2017) 74–79.

Speaker: David Mueller (TU Wien)

qm22_dm.pdf

18:18 Pursuing the Precision Study for Color Glass Condensate in Forward Hadron Productions

With the tremendous accomplishments of RHIC and the LHC experiments and the advent of the future Electron-Ion Collider on the horizon, the quest for compelling evidence of the color glass condensate (CGC) has become one of the most aspiring goals in the high energy quantum chromodynamics research. Pursuing this question requires developing the precision test of the CGC formalism. By systematically implementing the threshold resummation, we significantly improve the stability of the next-to-leading-order calculation in CGC for forward rapidity hadron productions in pp and pA collisions, especially in the high pT region, and obtain reliable descriptions of all existing data measured at RHIC and the LHC across all pT regions. Consequently, this technique can pave the way for the precision studies of the CGC next-to-leading-order predictions by confronting them with a large amount of precise data.

Speaker: Dr Yu Shi (Shandong University)

QM_22_hadron.mp4

QM_22_hadron.pdf

18:22 Significant charge splitting of rapidity-odd directed flow slope and its implication on electromagnetic effect in Au+Au, $^{96}_{44}$Ru, and $^{96}_{40}$Zr+$^{96}_{40}$Zr collisions from STAR

Heavy-ion collisions can produce an ultra-strong magnetic field, the evolution of which was predicted to decrease (increase) the directed flow slope, $dv_1/dy$, for positively (negatively) charged particles [1, 2]. In this work, we study this effect with large statistics datasets accumulated for Au+Au, $^{96}_{44}$Ru+$^{96}_{44}$Ru, and $^{96}_{40}$Zr+$^{96}_{40}$Zr isobar collisions at $\sqrt{s_{NN}}=$ 200 GeV, and Au+Au collisions at $\sqrt{s_{NN}}=$ 27 GeV. The charge dependent $dv_1/dy$ splitting, $\Delta(dv_1/dy)$, will be presented for $\pi^{\pm}$, $K^{\pm}$, and (anti)proton. A finite $\Delta(dv_1/dy)$ between protons and anti-protons has been observed and it changes from positive to negative as a function of centrality from central to peripheral collisions. This is the first observation of a significant negative $\Delta(dv_1/dy)$ between proton and anti-protons. A similar decreasing trend of slope difference between $K^+$ and $K^-$ has also been observed in Au+Au collisions at $\sqrt{s_{NN}}=$ 200 GeV and 27 GeV, and in isobar collisions with less significance. The slope difference between $\pi^+$ and $\pi^-$ is negative and decreases as a function of centrality in Au+Au collisions at $\sqrt{s_{NN}}=$ 27 GeV, while no significant slope difference is observed in Au+Au and isobar collisions at $\sqrt{s_{NN}}=$ 200 GeV. Our measurements of significant negative $\Delta(dv_1/dy)$ cannot be explained by conventional mechanisms (e.g. transported quarks), but qualitatively agree with the theoretical prediction with an ultra-strong electromagnetic field in peripheral collisions.

[1] U. Gursoy, D. Kharzeev, E. Marcus $et~al.$, Phys. Rev. C ${\bf 98}$, 055201 (2018).
[2] U. Gursoy, D. Kharzeev and K. Rajagopal, Phys. Rev. C $\bf{89}$, 054905 (2014).

Speaker: Diyu Shen

poster_v4.pdf

18:26 Pre-hydrodynamical effects in large and small systems

The pre-hydrodynamic evolution of a heavy-ion collision can have a considerable effect on final state observables, notably those related to the transverse momentum spectra of final particles [1]. In this work, we study two different collision systems, namely Pb-Pb and p-Pb, utilising a state-of-the-art hybrid model. We extend our previous results [1] on the effects of pre-hydrodynamical models on final state observables to small systems. We show that the artificial bulk pressure generated at the switch to hydrodynamics by the assumption of scaling invariance during the pre-hydrodynamical evolution is enhanced for smaller systems sizes. We also show that its magnitude is dependent on the duration of the pre-hydrodynamical phase, growing with longer evolution times. These results further reinforce the need for non-conformal pre-hydrodynamical models, particularly in light of concerns about the validity of hydrodynamics at early times and the resulting need for accurate pre-hydrodynamic evolution, and the growing interest in small systems. Finally, we investigate whether a free-streaming pre-hydrodynamical evolution with a velocity smaller than $c$ [2], thus effectively breaking the assumption of scale invariance, can alleviate the effects of this artefact when performing the extraction of transport coefficients and initial state parameters from hybrid simulations.

[1] Tiago Nunes da Silva, David Chinellato, Mauricio Hippert, Willian Serenone, Jun Takahashi, Gabriel S. Denicol, Matthew Luzum, Jorge Noronha, Phys. Rev. C 103, 054906 (2021)

[2] Govert Nijs, Wilke van der Schee, Umut Gürsoy, Raimond Snellings, Phys. Rev. C 103, 054909 (2021)

Speaker: Antonio Mauricio Soares Narciso Ferreira (University of Campinas)

QM2022 - Mauricio N. Ferreira - v3.pdf

17:30 → 18:30 Poster Session 1 T02

17:30 Study of non-flow baseline for the CME signal via two-particle ($\Delta\eta$, $\Delta\phi$) correlations in isobar collisions at STAR

Recently, STAR reported the isobar (${^{96}_{44}\text{Ru}}+{^{96}_{44}\text{Ru}}$, ${^{96}_{40}\text{Zr}}+{^{96}_{40}\text{Zr}}$) results for chiral magnetic effect (CME) search [1]. The Ru+Ru to Zr+Zr ratio of the CME-sensitive observable $\Delta\gamma$, normalized by elliptic anisotropy ($v_{2}$), is close to the inverse multiplicity ($N$) ratio. In other words, the ratio of the $N\Delta\gamma/v_{2}$ observable is close to the naive background baseline of unity. However, non-flow correlations are expected to cause the baseline to deviate from unity. To further understand the isobar results, we study non-flow effects using the same isobar data by two-particle correlations as functions of pseudorapidity and azimuthal angle differences ($\Delta\eta$, $\Delta\phi$) of the pairs. We extract the charge-dependent correlations by the difference between the opposite-sign (OS) and same-sign (SS) charge pairs, properly normalized such that the correlations vanish at $|\Delta\eta|\rightarrow \infty$. These charge-dependent correlations come primarily from resonance decays, intra-jet (near-side) correlations, and Coulomb effects. We study the charge-independent correlations by examining the small and large $|\Delta\eta|$ behaviors of the SS correlations. The intra-jet (near-side) can be well isolated at small $|\Delta\eta|$ and $|\Delta\phi|$. We investigate the inter-jet (away-side) correlations by exploiting Pythia and HIJING simulations, together with the knowledge of near-side correlations obtained from the data. By comparing the two isobar systems, many systematic uncertainties can be minimized. By studying how non-flows differ between the two isobar systems, we can gain insights into the baseline of the CME.

[1] M. Abdallah et al. [STAR], [arXiv:2109.00131 [nucl-ex]].

Speaker: Mr Yicheng Feng (Purdue University)

QM2022PosterSlides_YichengFeng_v27.pdf

17:34 Angular Momentum in Heavy-Ion Collisions via the Hadronic Transport Approach SMASH

We investigate the angular momentum in heavy-ion collisions applying the hadronic transport approach SMASH. In contrast to geometrical models (e.g. a Glauber approach) our transport approach allows to access the full phase-space information of every particle at any time. The importance of understanding the non-equilibrium angular momentum transferred to the fireball and in turn the quark-gluon plasma (QGP) was highlighted by recent results of the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). The spin polarization measurement of the $\Lambda$-hyperon revealed a high angular momentum of the heavy ions and provided experimental evidence for vorticity in the QGP for the first time. Therefore, a systematic exploration of the angular momentum within a dynamic calculation for beam energies from $\sqrt{s}_{NN}= 2.41GeV$ to $\sqrt{s}_{NN}= 200GeV$ is a crucial step towards the full description of vorticity as a fundamental property of the QGP. Results for the angular momentum of Au-Au collisions as function of the impact parameter are presented and the influence of the initial Fermi momentum is studied. Moreover, it is shown that the angular momentum exhibits a distinct maximum for a specific impact parameter, independent of the beam energy. We show that the remaining angular momentum $L_r$ of the system grows with increasing system size in a range of $A=16$ $(^{16}_8O)$ to $A=208$ $(^{208}_{82}Pb)$ while we observe that for smaller beam energies a larger fraction of the initial angular momentum is transferred to $L_r$. The findings are important to guide future experimental programs and indicate where the largest transfer of angular momentum is expected.

Speaker: Nils Sass

Sass_QM22_AngularMomentum.pdf

17:38 Relativistic spin-magnetohydrodynamics

Recent relativistic heavy-ion collision experiments have found evidence for the generation of strong magnetic field and global angular momentum. The numerical simulation of evolution of the QCD medium is based on either magnetohydrodynamics or spin-hydrodynamics for calculation of observables pertaining to magnetic field or global angular momentum, respectively. However, these two effects are not entirely separable due to the possible spin alignment of medium constituents in the presence of magnetic field, similar to the Einstein-de Haas effect. Therefore a unified framework of “spin-magnetohydrodynamics” needs to be developed for precise calculation of experimental observables. Here we present the first formulation of this unified framework in relativistic context.

Starting from the classical description of spin, a kinetic theory of massive spin-1/2 particles in the presence of a magnetic field is obtained in the small polarization limit. We use a relaxation time approximation for the collision kernel in the relativistic Boltzmann equation and obtain the correction to phase-space distribution function. Building on the kinetic description, we then formulate a non-resistive, relativistic dissipative spin-magnetohydrodynamics for a fluid, whose constituent particles are considered to be spin-polarizable but non-magnetizable. We find multiple novel transport coefficients and show that all dissipative currents i.e. particle diffusion, shear stress tensor, bulk viscous pressure and non-equilibrium spin-tensor contain coupling between spin and magnetic field.

Speaker: Dr Amaresh Jaiswal (National Institute of Science Education and Research)

Poster_Amaresh_Jaiswal.pdf

17:42 Understanding $\phi$ meson production through polarisation study in pp collisions with ALICE at the LHC

The study of the production of $\phi$ meson has always been of great interest both in elementary and heavy-ion collisions. As observed by ALICE, strangeness enhancement in high-multiplicity pp collisions is one of the potential manifestations of QGP formation. Recent results at LHC suggest that $\phi$ behaves like a particle with net strangeness between 1 and 2 in small systems. These observations unfold new directions for theoretical and experimental studies of $\phi$ meson production in small systems. Polarization measurements of vector mesons are crucial for understanding the particle production mechanisms in high-energy collisions. In non-central heavy-ion collisions, the presence of a large initial angular momentum can polarise the vector mesons. This might be either due to spin-orbital-angular-momentum interaction or by hadronization from polarized quarks. The $\phi$ meson polarisation in pp collisions could be used as a reference while interpreting the results from heavy-ion collisions. The huge data sample collected during the Run 2 of the LHC measurements gives access to look for the multiplicity dependence of this measurement. This poster will present the perspectives for new results on the multiplicity dependence of $\phi$ meson polarisation in pp collisions at $\sqrt{s}$ = 13 TeV in the helicity reference frame.

Speaker: Dr Arvind Khuntia

17:46 Measurement of Direct Photon Cross Section and Double Helicity Asymmetry at $\sqrt{s}$ = 510 GeV in $\vec{p}+\vec{p}$ Collisions at PHENIX

The proton spin decomposition provides key information about the structure of the nucleons. Since the late 1980s, experiments showed that the quark spin contributes only $\sim$30\% to the proton spin, with the remaining part coming from the gluon spin as well as the quark and gluon orbital angular momentum. While the quark spin contribution was better constrained by polarized deep inelastic scattering, the gluon spin contribution remains less known. The Relativistic Heavy Ion Collider (RHIC) is the only collider capable of producing two longitudinal polarized proton ($\vec{p}+\vec{p}$) beams. Direct photon, jet, and charged pion production in $\vec{p}+\vec{p}$ collisions can probe the gluon spin at leading order. Compared with hadron production, direct photon production is the most "clean" channel, since there is little fragmentation involved. However, the relatively small direct photon cross section compared to the hadron production makes it a challenging observable. To achieve this "golden channel" measurement, we utilize the RHIC 2013 run, which provides the largest integrated luminosity (155 pb$^{-1}$) in $\vec{p}+\vec{p}$, along with the PHENIX Electromagnetic Calorimeter, which has fine granularity to separate the two $\pi^0$ decay photons up to $\pi^0$ transverse momentum $p_T$ of 12 GeV/c. A shower profile analysis extends the $\gamma/\pi^0$ discrimination to beyond 20 GeV/c. This poster will present the direct photon cross section and double helicity asymmetry for the direct photon $p_T$ of 6--30 GeV/c and 6--20 GeV/c, respectively. When included in future global analyses, our results will provide an independent constraint on the gluon spin contribution to the proton spin.

Speaker: Dr Zhongling Ji (UCLA)

poster.pdf

17:50 Hyperon polarization along the beam direction relative to the second and third order event planes in isobar collisions from STAR

Non-trivial collective velocity field due to anisotropic flow leads to vorticity along the beam direction in heavy-ion collisions. Polarization of $\Lambda$ and $\bar{\Lambda}$ hyperons along the beam direction relative to the elliptic flow plane has been observed in Au+Au collisions at RHIC and Pb+Pb collisions at the LHC. However, unlike for the case of the global polarization originating from the initial orbital angular momentum, theoretical models fail to describe its magnitude and sign, which is currently under intense discussion. Measurements of the hyperon polarization in colliding systems smaller than Au+Au may shed light on this problem. One can also expect a local polarization arising from higher harmonic flow, which provides new insight into the vorticity and polarization phenomena.

We present the first measurements of $\Lambda$ hyperon local polarization relative to the second and third order event planes in Ru+Ru and Zr+Zr collisions at $\sqrt{s_{\rm NN}}$ = 200 GeV. The results will be compared to those in Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 200 GeV and the physics implications will be discussed.

Speaker: Takafumi Niida

Niida_QM2022_poster.pdf

17:54 Local spin polarization and helicity polarization in hydrodynamic approaches

We have studied local spin polarization and helicity polarization in the relativistic hydrodynamic model. Generalizing the Wigner functions previously obtained from chiral kinetic theory to the massive case, we present the possible contributions up to the order of hbar from thermal vorticity, shear viscous tensor, other terms associated with the temperature and chemical-potential gradients, and electromagnetic fields to the local spin polarization and helicity polarization. We then implement the (3+1) dimensional viscous hydrodynamic model to study the spin polarizations from these sources with a small chemical potential and ignorance of electromagnetic fields by adopting an equation of state different from those in other recent studies. Although the shear correction alone upon local polarization results in the sign and azimuthal-angle dependence more consistent with experimental observations, as also discovered in other recent studies, it is mostly suppressed by the contributions from thermal vorticity and other terms that yield an opposite trend. It is found that the total local spin polarization could be very sensitive to the equation of states, the ratio of shear viscosity over entropy density, and freezeout temperature.

Speaker: Cong Yi

Local spin polarization and helicity polarization in hydrodynamic approaches_Congyi.pdf

17:58 Relativistic Dissipative Spin Hydrodynamics from Kinetic Theory

Semi-classical evolution equations for the scalar and axial-vector components of the Wigner function are treated in the relaxation time approximation to introduce a framework of relativistic dissipative hydrodynamics of particles with spin 1/2. We show that a classical treatment of spin is consistent with earlier calculations using the Wigner function approach with a quantum description of spin. We then derive non-equilibrium corrections to the spin tensor. The detailed structure of the non-equilibrium spin tensor reveals the existence of multiple spin transport coefficients [1,2]. This development indicates that it might be necessary to incorporate the effects of the multiple hydrodynamic gradients to properly characterize the nature of spin-polarization observed in heavy-ion collisions.
[1] Bhadury, S. et. al. Phys.Lett.B 814 (2021) 136096.
[2] Bhadury, S. et. al. Phys.Rev.D 103 (2021) 1, 014030.

Speaker: Mr SAMAPAN BHADURY

QM 2022 - Samapan Bhadury.pdf

18:02 Quark coalescence model for spin alignment and polarization of hadrons

In non-central heavy-ion collisions, a large orbital angular momentum is created along the direction opposite to the reaction plane, which will be transferred to the spin of quarks through the spin-orbit coupling in parton scatterings. In our recent work, we formulate an improved coalescence model through spin density matrix with phase space dependence, which provides a uniform way to compute spin alignments of vector mesons and polarizations of baryons from polarizations of quarks and antiquarks. Within this model, various sources of spin polarization are studied, including vorticity fields, electromagnetic fields, and mean fields of vector mesons. We find that the electric part of the vector $\phi$ field can qualitatively explain the positive deviation from 1/3 for the spin alignment of $\phi$ mesons measured by the STAR collaboration. On the other hand, the spin alignment of $K^{*0}$ mesons is dominated by the electric part of vorticity fields and our model prediction also qualitatively agrees with experimental results.

Speaker: Xin-Li Sheng (Central China Normal University)

Spin coalescence.pdf

18:06 Spin Boltzmann equation and global polarization in HIC

We derive Boltzmann equations for massive spin-1/2 fermions with local and nonlocal collision terms from the Kadanoff--Baym equation in the Schwinger--Keldysh formalism, properly accounting for the spin degrees of freedom. The Boltzmann equations are expressed in terms of matrix-valued spin distribution functions, which are the building blocks for the quasi-classical parts of the Wigner functions. Nonlocal collision terms appear at next-to-leading order in ℏ and are sources for the polarization part of the matrix-valued spin distribution functions. The Boltzmann equations for the matrix-valued spin distribution functions pave the way for simulating spin-transport processes involving spin-vorticity couplings from first principles.

Speaker: Prof. Dirk Rischke (University Frankfurt)

Boltzmann_equation.pdf

18:10 Impact of the nuclear structure on the isobar run at RHIC

No chiral-magnetic effect signature has been observed in the experimental analysis of the isobar run at RHIC [1]. In this talk, based on [2], we highlight the influence of the nuclear structure of the isobar systems on the CME search within a relativistic hadronic transport approach (SMASH). We show that the quadrupole deformation of Ru enhances the eccentricity ratio between the isobars in ultra-central collisions up to 10%, thus leading to different CME backgrounds in the two isobar systems. In addition, the neutron skin of Zr reduces a factor of 2, from 10% to 5% , the magnetic field strength difference in peripheral collisions. These two predictions suggest a significantly smaller CME signal to background ratio than previously expected, as has been confirmed experimentally.

[1] 2109.00131
[2] Phys.Rev.C 101 (2020) 6, 061901

Speaker: Hannah Elfner

Elfner_QM_neutronskin.pdf

18:14 Search for the Chiral Magnetic Wave in Pb-Pb collisions with the ALICE detector

The interplay of the chiral anomaly and the strong magnetic field (~10$^{15}$ T) created in the off-central heavy-ion collisions could give rise to a collective excitation in the quark-gluon plasma called the Chiral Magnetic Wave (CMW), which can be experimentally sought by the charge asymmetry ($A_{\rm ch}$) dependence of elliptic flow $v_2$ of positively and negatively charged hadrons. However, non-CMW mechanisms such as local charge conservation (LCC) intertwined with collective flow can also lead to a similar dependence of $v_2$ on $A_{\rm ch}$. The measurement with triangular flow ($v_3$) thus serves as a reference as it is not expected to be affected by the CMW.

In this talk, we present new ALICE measurements of $v_2$ and $v_3$ of inclusive and identified hadrons as functions of $A_{\rm ch}$ in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 and 5.02 TeV. The slope parameters of $\Delta v_2$-$A_{\rm ch}$ and $\Delta v_3$-$A_{\rm ch}$ correlations, where the $\Delta v_n$ are the differences between $v_n$ of positive and negative particles, are normalized and then compared with results from other experiments and models. In addition, the Event Shape Engineering (ESE) technique is adopted for the first time to quantitatively distinguish the CMW signal and the LCC background. The upper limit of the CMW signal contribution is further extracted. Our measurements reveal that the background effect is dominant in the search for the CMW in heavy-ion collisions.

Speaker: Wenya Wu (Fudan University (CN))

QM22-CMW.pdf

video-QMPoster-CMW.mov

18:18 Causal instabilities of the Chern-Simons magnetohydrodynamics

This talk presents a novel instability in the Chern-Simons (or axionic) magnetohydrodynamics (MHD), arising from the spatial inhomogeneity of the axion-like field. In particular, this instability amplifies the Alfven waves in certain regions of spacetime in a way that is clearly parity-violating. The Aflven velocity reaches the speed of light in such regions, but it never exceeds it.

Speakers: Masoud Shokri (Goethe University), Neda Sadooghi (Sharif University of Technology)

qm-csmhd.pdf

18:22 Canonical vs. Phenomenological Formulations of the Spin Hydrodynamics

Recent observations of the spin polarization of weakly decaying Lambda hyperons have opened up a new direction to explore non-trivial vortical structures of strongly interacting matter produced in the heavy-ion experiments. A consistent framework of relativistic hydrodynamics with spin degrees of freedom (spin hydrodynamics) is under construction now to allow for future dynamic simulations of the spin polarization. This type of hydrodynamic description is based on the conservation of the total energy and linear momentum as well as the total angular momentum which includes both the orbital and spin parts.

The phenomenological approach used to construct the framework of spin hydrodynamics commonly uses a simplified form of the spin tensor [1,2]. This form does not posses an expected symmetry, namely, it is not totally anti-symmetric (which is a direct consequence of Noether's Theorem applied to the Dirac Lagrangian). Consequently, in this approach the connection between the spin hydrodynamics and the underlying field-theoretic arguments is obscured.

In our recent work [3] we demonstrate how one can connect the spin hydrodynamics constructed with a totally antisymmetric (canonical) spin tensor with the phenomenological approach used by other authors. We show that the two frameworks are not connected only by a pseudo-gauge transformation (what most people implicitly assume) but an additional subtraction of a specific divergence-free term to the canonical energy-momentum tensor should be done.

Our results help us to find and clarify connections between different formulations of spin hydrodynamics, which is important for the construction of a final, fully consistent formalism.

Speaker: Asaad Daher

poster_5_slides_Canonical_Vs__Phenomenological_Formulations_of_Spin_Hydrodynamics-2.pdf

18:26 Modelling particle polarization with spin hydrodynamics

Since the first positive measurement of the Λ-hyperon global spin polarization in heavy-ion collisions by STAR collaboration in 2017, the understanding of the nature of this phenomenon is one of the most intriguing challenges for the heavy-ion physics community. As relativistic fluid dynamics celebrates multiple successes in describing collective dynamics of the QCD matter in such reactions, the natural question arises whether the spin dynamics can also be modeled in such a framework. In this talk, we will discuss the theoretical aspects of the relativistic spin hydrodynamics framework which is based on the de Groot - van Leeuwen - van Weert forms of energy-momentum and spin tensors. We will also show how this formalism can be used to determine observables describing the spin polarization of particles measured in the experiment.

Speaker: Mr Rajeev Singh (Institute of Nuclear Physics Polish Academy of Sciences)

2112.01856.pdf

Rajeev_Singh_QM_poster.pdf

17:30 → 18:30 Poster Session 1 T02 / T03

17:30 Energy-dependence of the chiral magnetic effect in expanding holographic plasma

Based on a holographic far-from-equilibrium calculation of the Chiral Magnetic Effect (CME) in an expanding quark-gluon plasma, we study collisions at various energies. We compute the time evolution of the CME current in the presence of a time-dependent axial charge density and subject to a time-dependent magnetic field. The plasma expansion leads to a dilution and eventual annihilation of the CME current after approximately 5 fm/$c$. We study distinct combinations of how the initial magnetic field and initial axial charge behave with changing initial energy as proposed in the previous literature. Most scenarios we consider lead to an increasing CME current, integrated over time, when increasing the initial energy. This would make it more likely to observe the CME at higher collision energies. However, in the scenario that the axial charge and magnetic field are fixed while the initial energy is decreased, the holographic plasma shows an increasing time-integrated CME current. This is the only one of the six scenarios which we studied which would suggest the CME to be more likely found at lower collision energies.

Speaker: Mr Casey Cartwright (The University of Alabama)

QM_Energy_Dep_CME_Cartwright_2022.pdf

17:34 Effect of nuclear distribution uncertainties on the search for the chiral magnetic effect (CME) in isobaric collisions of Ru+Ru and Zr+Zr collisions at RHIC

The search for the chiral magnetic effect (CME) in isobaric collisions of Ru+Ru and Zr+Zr at RHIC was motivated by the assumed similarity of the backgrounds (e.g., $v_n$, $N_{\rm chg}$) for the two isobars. The effects of nuclear structure differences and deformation can lead to essential differences in the backgrounds for the two isobars. Here, we use a quark Glauber model, validated in earlier studies of small and large systems, to study the effects of nuclear distribution uncertainties, especially the details of a Zr halo and nuclear shape fluctuations, on background-related variables such $\varepsilon_n$, and particle production for the isobars. The influence of such uncertainties on both particle production and $\varepsilon_n$ is significant; they provide invaluable constraints for pinning down the requisite differences for CME study in isobaric collisions. They also show that a data-model study of relevant bulk observables could constrain nuclear distribution parameters.

Speaker: Peifeng Liu (Stony Brook University)

17:38 Study of Chiral Magnetic Effect in Isobar (Ru$+$Ru and Zr$+$Zr) and Au$+$Au collisions at $\sqrt{s_\mathrm{NN}} = 200$ GeV at STAR using Sliding Dumbbell Method

To probe the Chiral Magnetic Effect (CME) in heavy-ion collisions, a new technique, Sliding Dumbbell Method (SDM) [1] is developed to search for the back-to-back charge separation on event-by-event basis. The SDM helps in selecting the events corresponding to different charge separations ($f_{DbCS}$). The charge separation distributions for each collision centrality is divided into 10 percentile bins to select potential CME-like events corresponding to the maximum charge separation (e.g. top 10$\%$) in a given collision centrality. Results will be discussed for two- and three-particle correlators with respect to each bin of $f_{DbCS}$ for each collision centrality for isobaric and Au$+$Au collisions at $\sqrt{s_\mathrm{NN}} = 200$ GeV. The background contribution due to statistical fluctuations is obtained by shuffling the charges of particles in a given collision centrality. The correlated background amongst the produced particles which got removed due to shuffling is determined by restoring the shuffled charges.

References
[1] J. Singh, A. Attri, and M. M. Aggarwal, Proceedings of the DAE Symp. on Nucl. Phys. 64, 830 (2019) "http://www.sympnp.org/proceedings/64/E66.pdf".

Speaker: Mr Jagbir Singh (Panjab University, Chandigarh)

QM22_Poster_Jagbir_Final.pdf

17:42 Freezing out critical fluctuations

We introduce a novel freeze-out procedure connecting the hydrodynamic evolution of a droplet of quark-gluon plasma (QGP) that has, as it expanded and cooled, passed close to a critical point on the QCD phase diagram with the subsequent kinetic description in terms of observable hadrons. The procedure converts out-of-equilibrium critical fluctuations described by extended hydrodynamics, known as Hydro+, into cumulants of hadron multiplicities that can be subsequently measured. We introduce a critical sigma field whose fluctuations cause correlations between observed hadrons due to the couplings of the sigma field to the hadrons. We match the QGP fluctuations obtained via solving the Hydro+ equations describing the evolution of critical fluctuations before freeze-out to the correlations of the sigma field. In turn, these are imprinted onto fluctuations in the multiplicities of hadrons, most importantly protons, after freeze-out via a generalization of the familiar half-a-century-old Cooper-Frye freeze-out prescription which we introduce. This framework allows us to study the effects of critical slowing down and the consequent deviation of the observable predictions from equilibrium expectations quantitatively. We can also quantify the suppression of cumulants due to the conservation of baryon number. We demonstrate the prescription in practice by freezing out the Hydro+ simulation in a simplified azimuthally symmetric and boost invariant background discussed previously.

Speaker: Maneesha Pradeep (UIC)

QMPoster22copyPradeep1.pdf

17:46 Equation of state and baryon kurtosis in the presence of a critical point

We construct a family of equations of state for QCD, which reproduce the lattice results at small chemical potential and include a critical point in the 3D Ising model universality class. These equations of state, based on the original formulation developed in [1], include the constraint of strangeness neutrality, which is phenomenologically relevant for heavy-ion collisions [2]. We then use our parametrization to study the quartic cumulant of the baryon number $\chi_4^B$, which can be accessed experimentally via net-proton fluctuation kurtosis measurements. It was originally predicted, through universality arguments based on the leading singular contribution, that $\chi_4^B$ should show a specific nonmonotonic behavior due to the critical point. In particular, when following the freeze-out curve on the phase diagram by decreasing beam energy, the kurtosis is expected to dip, and then peak, when the beam energy scan passes close to the critical point. We find that, while the peak remains a solid feature, the presence of the critical point does not necessarily cause a dip in $\chi_4^B$ on the freeze-out line below the transition temperature [3].

References
[1] P. Parotto et al., Phys. Rev. C101 (2020) 3, 034901.
[2] J. M. Karthein et al., Eur. Phys. J. Plus 136 (2021) 6, 621.
[3] D. Mroczek et al., Phys. Rev. C103 (2021) 3, 034901.

Speaker: Claudia Ratti

Poster_Krakow_2022.pdf

17:50 Transport properties of the QGP in the dynamical quasi-particle model with a CEP

We explore the transport properties of the QGP matter in the high $\mu_B$ region, where a CEP is incorporated. To this aim we extend the effective dynamical quasi-particle model (DQPM) - constructed for the description of non-perturbative QCD phenomena of the strongly interacting quark-gluon plasma (QGP) - to large baryon chemical potentials, $\mu_B$, including a critical end-point and a 1st order phase transition.
The DQPM is based on covariant propagators for quarks/antiquarks and gluons that have a finite width in their spectral functions (imaginary parts of the propagators). In DQPM the determination of complex selfenergies for the partonic degrees-of-freedom at zero and finite $\mu_B$ has been performed by adjusting the entropy density to the lattice QCD (lQCD) data. The temperature-dependent effective coupling (squared) $g^2(T/T_c)$, as well as the effective masses and widths or the partons are based in this adjustment.
The novel extended dynamical quasi-particle model, named "DQPM-CP", makes it possible to describe thermodynamical and transport properties of quarks and gluons in a wide range of temperature, $T$, and baryon chemical potential, $\mu_B$, and reproduces the equation-of-state (EoS) of lattice QCD calculations in the crossover region of finite $T, \mu_B$.
We apply a scaling ansatz for the strong coupling constant near the critical endpoint CEP, located at ($T^{CEP}$, $\mu^{CEP}_B) = (0.100, 0.960)$ GeV. We show the equation-of-state as well as the speed of sound for $T>T_c$ and for a wide range of $\mu_B$, which can be of interest for hydrodynamical simulations. Moreover, one of the advantages of the quasi-particle models is a simple implementation in transport models.
Furthermore, we consider two settings for the strange quark chemical potentials (I) $\mu_q=\mu_u=\mu_s=\mu_B/3$ and (II) $\mu_s=0,\mu_u=\mu_d=\mu_B/3$. The isentropic trajectories of the QGP matter are compared for these two cases.
Despite that the phase diagram of the DQPM-CP is close to the PNJL calculations the transport coefficients of both approaches differ. This elucidates that the knowledge of the phase diagram alone is not sufficient to describe the dynamical evolution of strongly interacting matter.

Speaker: Olga Soloveva (Goethe University Frankfurt)

06Apr_2022_Solo_Olga_QM+poster.pdf

17:54 New constraints for QCD matter from improved Bayesian parameter estimation

Transport properties of the matter created in heavy-ion collisions, the quark-gluon plasma (QGP), contain essential information about quantum chromodynamics (QCD). To deepen our understanding of QCD, it is crucial to estimate these transport properties (for instance, specific shear and bulk viscosity) in the light of experimental data as accurately as possible. In this talk, we present our latest study in inferring the transport properties of QGP by an improved Bayesian analysis using the CERN Large Hadron Collider Pb-Pb data at $\sqrt{s}_{NN}=2.76$ and 5.02 TeV. To improve the uncertainties, we include new observables sensitive to specific shear and bulk viscosity, reflecting mostly nonlinear hydrodynamic responses. We show that the uncertainty of the transport coefficients is significantly reduced by including the latest flow harmonic measurements. The analysis also reveals that higher-order harmonic flows and their correlations have a higher sensitivity to the transport properties than the other observables. This observation shows the necessity of accurate measurements of these observables in the future.

Based on:
[1] J.E. Parkkila, A. Onnerstad, D.J. Kim, Phys.Rev.C 104 (2021) 5, 054904, arXiv: 2106.05019 [hep-ph]
[2] J.E. Parkkila, A. Onnerstad, S. F. Taghavi, C. Mordasini, A. Bilandzic, D.J. Kim, arXiv: 2111.08145 [hep-ph]

Speaker: Seyed Farid Taghavi (Technische Universitaet Muenchen (DE))

QM22-Bayesian-Taghavi-Final.pdf

17:58 Modeling Heavy-ion Collisions at Non-zero Chemical Potentials

Realistic modeling of nucleus-nucleus collisions at finite baryon chemical potential is necessary to extract the location of the critical point on the QCD phase diagram and to understand the findings of the recently concluded Beam Energy Scan (BES) program at RHIC and the future planned experiments at FAIR and NICA. We propose a hydrodynamic model with three new elements. Firstly, we present a new initial state model at non-zero chemical potential based on the Monte-Carlo sampling of the nucleon-nucleon scattering extrapolated to nucleus-nucleus collisions (LEXUS [1]). This model dynamically initializes hydro, which is evolved using MUSIC [2]. Secondly, we employed a new cross-over equation of state [3]. Finally, we calculated the departure functions at finite chemical-potential using a quasi-particle theory of transport [4] and used it in Cooper-Frye procedure. We present comparisons with STAR data for a wide range of collision energies - 7.7 GeV - 200 GeV.

1. S. Jeon and J. Kapusta, Phys. Rev. C 56, 468 (1997)
2. B. Schenke, S. Jeon and C. Gale, Phy. Rev. C 82, 014903 (2010)
3. M. Albright, J. Kapusta, and C. Young, Phys. Rev. C 90, 024915 (2014)
4. M. Albright and J. Kapusta, Phys. Rev. C 93, 014903 (2016)

Speaker: Mayank Singh (McGill University)

QM_2022.pdf

18:02 Thermal properties of a glueball gas

We study the thermodynamic properties, such as the pressure and the entropy density, of a gas of glueballs by considering the contribution of the tower of various glueball states obtained by using recent lattice calculations as well as other model results. We also include, to our knowledge for the first time, the effect of glueball-glueball interaction on thermodynamic properties. The results are compared with the current Yang-Mills lattice data and to other theoretical approaches.

Speaker: SHAHRIYAR JAFARZADE (Jan Kochanowski University of Kielce, Poland)

Quark_Matter_2022.pdf

18:06 Equilibrium and Dynamical Properties of Hot and Dense Quark-Gluon Matter from Holographic Black Holes

By using gravity/gauge correspondence, we employ an Einstein-Maxwell-Dilaton model to compute the equilibrium and out-of-equilibrium properties of a hot and baryon rich strongly coupled quark-gluon plasma. The family of 5-dimensional holographic black holes, which are constrained to mimic the lattice QCD equation of state at zero density, is used to investigate the temperature and baryon chemical potential dependence of the equation of state [1]. We also obtained the baryon charge transport coefficients, the bulk and shear viscosities as well as the drag force and Langevin diffusion coefficients associated with heavy quark jet propagation and the jet quenching parameter of light quarks in the baryon dense plasma, with a particular focus on the behavior of these observables on top of the critical end point and the line of first order phase transition predicted by the model.
[1] Grefa, J., Noronha, J., Noronha-Hostler, J., Portillo, I., Ratti, C., Rougemont, R. 10.1103/PhysRevD.104.034002

Speaker: Joaquin Grefa

QM_2022_poster_Grefa.pdf

18:10 Bound states and resonances in thermal models

We study the thermal properties of scalar quantum field theories (QFTs) involving 3-leg and 4-leg interaction terms, with special attention on the role of bound states and resonances. Within a suitable unitarization scheme, for which the employed QFT is unitary, finite, and well defined for each value of the coupling constant, we calculate the scattering phase shifts, whose derivatives are used to infer the pressure of the system at nonzero $T$. A bound state emerges in each when the attraction is strong enough, but we show that it does not count as one state in the thermal gas, since a cancellation with the residual scattering interaction typically occurs. The amount of this cancellation depends on the details of the model and its parameters: a variety of possible scenarios is presented. Moreover, even when no bound state occurs, we estimate the role of the interaction in general and of resonances in particular.

Speaker: Prof. Francesco Giacosa (Kielce University)

Giacosa_QM2022_krakow.pdf

18:14 Resummed thermodynamics of QCD and N=4 supersymmetric Yang-Mills theory

In this talk I review recent progress in resummed perturbative calculations of the equation of state of QCD and N=4 supersymmetric Yang-Mills (SUSY) theory. In the case of QCD, I will review progress that has been made using hard-thermal-loop perturbation theory (HTLpt) at finite temperature and quark chemical potential(s), focussing on recent NNLO HTLpt predictions for the quadratic and quartic curvatures of the QCD phase transition line in different physics cases. The NNLO HTLpt predictions are found to agree well with available lattice data for the curvature coefficients where available, and provide predictions for these coefficients in cases where they have not been accurately determined on the lattice. In the second part of my talk, I will discuss recent results which extend the perturbative determination of N=4 SUSY thermodynamics through second-order in the 't Hooft coupling. The final result contains non-analytic terms which are not present in the strong-coupling limit and the resummed perturbative series shows signs of having a finite and large radius of convergence.

References:

[1] N. Haque and M. Strickland, Phys. Rev. C 103, 031901 (2021).
[2] Q. Du, M. Strickland, and U. Tantary, J. High Energ. Phys. 2021, 64 (2021).
[3] J.O. Andersen, Q. Du, M. Strickland, and U. Tantary, forthcoming.

Speaker: Michael Strickland (Kent State University)

strickland.pdf

18:18 Non-Equilibrium Transport of Conserved Charges in High-Energy Heavy Ion Collisions

Non-equilibrium Green’s functions provide an efficient way to describe the pre-equilibrium evolution of macroscopic quantities in early stages of heavy-ion collisions.
Within the kinetic theory framework we use moments of the distribution functions to calculate time dependent non-equilibrium Green’s functions describing the evolution of initial energy/momentum/charge perturbations [1]. Using kinetic theory in relaxation time approximation we will study the pre-equilibrium evolution of a Bjorken background and compute Green’s functions for the charge current and energy-momentum tensor for initial perturbations around this background. By calculating the Green’s functions, we show that only modes with long wavelength survive up into the hydrodynamic regime.
[1] [Kamata, Martinez, PP, Ochsenfeld, Schlichting, Phys. Rev. D (2020)]

Speaker: Philip Plaschke (Bielefeld University)

QM22Poster.pdf

18:22 Causality violations in realistic nuclear collision simulations

Hydrodynamic models are a central component of nuclear collision phenomenology. In this talk, I show that relativistic causality is violated in the early stages of state-of-the-art heavy-ion hydrodynamic simulations of nuclear collisions. Up to 75% of the initial fluid cells violate nonlinear causality constraints, while superluminal propagation is observed by up to 15% the speed of light. Only after 2-3 fm$/c$ of evolution, do ∼50% of the fluid cells become definitely causal. Inclusion of pre-equilibrium evolution significantly reduces the number of acausal cells, but it does not eliminate them. These findings show that relativistic causality imposes constraints on the available model parameter space of heavy-ion collision simulations.

Speaker: Christopher Plumberg

Plumberg_Christopher.mp4

Plumberg_Christopher.pdf

Plumberg_Christopher.pptx

18:26 Chemical freeze-out of hadrons within the advanced Hadron Resonance Gas Model

An advanced Hadron Resonance Gas Model (HRGM) based on the induced surface tension equation of state [1, 2] is developed which correctly accounts for weak decays. We report our results on fits of the ratios of particle yields measured in a wide range of centre-of-mass energies from a few GeV up to 2.76 TeV. In particular, our analysis of the STAR experiment data on hadronic multiplicities demonstrates that taking into account the weak decays is extremely important to have a model that can describe the data with high accuracy and in a physically correct way. Moreover, the inclusion of weak decays in the analysis of BES data leads to a decrease in the chemical freeze-out (CFO) temperature of hadrons by about $10-15$ MeV. For the first time, the results for the CFO parameters obtained by the fits to the BES program data in the collision energy range $\sqrt{s_{NN}}=7.7-200$ GeV are in complete agreement with the ones obtained earlier in different models for the ALICE energy $\sqrt{s_{NN}}=2.76$ TeV [2,3] as well as with the Lattice QCD results for the pseudocritical line [4]. Remarkably, it is shown that the CFO parameters of light (anti-, hyper-) nuclei obtained in [5] are not affected by these modifications. They are in agreement with the PHQMD simulations [6] and provide a solution to the so-called “snowballs in hell” problem.

References:
[1] K. A. Bugaev et al., Nucl. Phys. A 970 (2018) 133.
[2] K. A. Bugaev et al., Eur. Phys. J. A 56 (2020) 293.
[3] A. Andronic et al., Nature 561 (2018) 321 and references therein
[4] B. Szabolcs et al., Phys. Rev. Lett. 125 (2020) 052001
[5] O. Vitiuk et al., Eur. Phys. J. A 57 (2021) 74.
[6] S. Gläßel et al., arXiv:2106.14839

Speaker: Elisaveta Zherebtsova

QM22_Zherebtsova.pdf

17:30 → 18:30 Poster Session 1 T04_1

17:30 Exploring jet transport coefficients by elastic scattering in the strongly interacting quark-gluon plasma

We study the interaction of leading jet partons in a strongly interacting quark-gluon plasma (sQGP) medium based on the effective dynamical quasi-particle model (DQPM). The DQPM describes the non-perturbative QCD nature of the sQGP at finite temperature $T$ and baryon chemical potential $\mu_B$ based on a propagator representation in terms of massive off-shell partons (quarks and gluons) which properties (characterized by complex self-energies, i.e. masses and widths) are adjusted to reproduce the lQCD EoS for the QGP in thermodynamic equilibrium. We present the results for the jet transport coefficients such as $\hat q$, the transverse momentum transfer per unit length, the drag coefficient $A$ as well as the energy loss per unit length $\Delta E =dE/dx$, in the QGP and investigate its dependence on QGP properties such as medium temperature $T$ and baryon chemical potential $\mu_B$ as well as on the jet properties such as leading jet parton momentum, mass, flavor, and the strong coupling constant. In this first study only elastic scattering processes of leading jet parton with the sQGP partons are explored discarding presently the radiative processes (such as gluon Bremsstrahlung) which are expected to be suppressed for the emission of massive gluons. We present a comparison of our results for the elastic energy loss in the sQGP medium with other theoretical approaches such as lattice QCD and the LO-HTL as well as with estimates of $\hat q$ by the JET and JETSCAPE collaborations based on a comparison of hydrodynamical calculations with the experimental heavy-ion data.

Speaker: Mr Ilia Grishmanovskii

QM22_Poster_Grishmanovskii.pdf

17:34 Hard-soft tomography with event engineering in heavy-ion collisions

The azimuthal anisotropy of parton energy loss in non-central heavy-ion collisions can lead to jet anisotropy which in turn can provide insight into the path-length dependence of jet quenching. Jet anisotropy flow in this study is investigated within the Linear Boltzmann Transport model, in which the dynamical evolution of the QGP is simulated within the CLVisc hydrodynamic model with fully fluctuating event-by-event initial conditions. We quantify the colliding energy, centrality, jet transverse momentum dependence of jet anisotropy flow coefficients $v^\mathrm{jet}_2$ and $v^\mathrm{jet}_{3}$, with emphasis on their event-by-event correlations with the flow coefficients of the soft bulk hadrons. We find that the correlation between jet and bulk anisotropy is approximately linear and that the effect of the bulk $v_n$ fluctuation on the event-averaged jet $v^\mathrm{jet}_n$ is negligible. Other effects such as medium excitation with different jet cone sizes and viscosity of the QGP on jet anisotropy are investigated as well.

Speaker: Dr Yayun He (South China Normal University)

Poster_YayunHe.pdf

17:38 Data-driven analysis of light parton transport properties in a factorized energy loss model

We perform a systematic data-driven extraction of the light parton transport properties in a quark-gluon plasma based on a hard-soft factorized parton energy loss model [1]. In this model, occasional hard interactions and frequent softer interactions are systematically factorized. The larger number of soft interactions makes possible an effective stochastic description of the parton-plasma interactions in terms of a small number of transport coefficients [2]. These soft transport coefficients can capture non-perturbative effects, agnostic to the strongly- or weakly-coupled nature of the underlying deconfined plasma.

We constrain the temperature dependence of these soft transport coefficients by performing a Bayesian model-to-data comparison with jet measurements from RHIC and LHC, allowing us to better understand the non-perturbative effects suffered by soft interactions in heavy ion collisions. We also study the dependence of the calibration results on the separation of the scale between soft and hard parton-plasma interactions in order to investigate the robustness of the approach. We discuss differences between this work's soft transport coefficients and the soft-hard ones extracted in other approaches, highlighting the strength of our factorized approach.

[1] Dai, Tianyu, Jean-François Paquet, Derek Teaney, and Steffen A. Bass. "Parton energy loss in a hard-soft factorized approach." arXiv preprint 2012.03441 (2020).

[2] Ghiglieri, Jacopo, Guy D. Moore, and Derek Teaney. "Jet-medium interactions at NLO in a weakly-coupled quark-gluon plasma." Journal of High Energy Physics 2016, no. 3 (2016): 1-58.

Speaker: Tianyu Dai

Tianyu_poster.pdf

17:42 Semi-inclusive recoil jet measurements via hadron-jet correlations in pp collisions at $\sqrt{s} = 5.02 ~\mathrm{TeV}$ with ALICE

In heavy-ion collisions, large transverse momentum partons traverse the colored medium and lose energy via induced gluon radiation and elastic scattering, which modify jet structure relative to jets produced in vacuum. The semi-inclusive recoil jet measurement provides precise, data-driven suppression of the large uncorrelated background and uniquely enables the exploration of medium-induced modification of jet production over wide phase space, including low$p_\mathrm{T}$ for large jet resolution parameter $R$. Such measurement in pp and p--Pb collisions provides a good test for pQCD calculations, and sets as a reference for jet quenching and acoplanarity study in nucleus-nucleus collisions.

In this contribution, we report the semi-inclusive distribution of charged jets recoiling from a high-$p_\mathrm{T}$ charged hadron trigger in pp collisions at $5.02 ~\mathrm{TeV}$, with emphasis on the region of low recoil jet $p_\mathrm{T}$ and large $R$. The semi-inclusive recoil jet distribution as a function of $p_\mathrm{T}$ and $\Delta\varphi$ will be presented, where $\Delta\varphi$ is the relative azimuthal angle between trigger track and recoil jets. The results, including the $R$-dependence, will be compared to models.

Speaker: Yongzhen Hou (Central China Normal University CCNU (CN))

220405_poster_v5.pdf

17:46 Multivariate sensitivity analysis of jet substructure observables to quenching

The modification of the substructure of jets due to interactions with a hot QCD medium, the quark-gluon plasma, can be used to study the properties of this medium. Due to the nature of a jet, as a composite object of multiple particles, there are many observables one could construct and study. There is no indication that a single observable will be sufficient to understand the interaction of the parton shower with the hot QCD medium. We investigate how the correlation of jet observables is affected by jet quenching. The medium effect on this correlation is quantified using the Kullback-Leibler divergence and a principle component analysis. We also consider the experimental constraints and the influence of the large uncorrelated background present in heavy-ion collisions on the measurement of these observables. We present a framework in which all these ingredients are combined to determine which correlation of observables can be best used to constrain the medium-jet modification while being robust against the large underlying event. As the framework is fully data driven it can easily be deployed on heavy-ion data from RIHC and LHC experiments.

Speaker: Bas Hofman (Nikhef National institute for subatomic physics (NL))

Multivariate sensitivity analysis of jet substructure observables to quenching.pdf

17:50 Studies of medium induced modification of jets using photon-tagged jets with the CMS detector

In this poster, measurements of the azimuthal opening angle and transverse momentum correlations between isolated photons and their associated jets, which are sensitive to medium induced parton momentum broadening, are reported for the first time with the high statistics pp and PbPb data recorded in 2017 and 2018. Isolated photon production and their detection techniques will also be summarized.

Speaker: Pin-Chun Chou (Massachusetts Inst. of Technology (US))

QM2022_pinchun.pdf

17:54 Thermalization of highly energetic partons in a QCD plasma

We study the thermalization of highly energetic partons in a high-temperature QCD plasma. We investigate the non-equilibrium dynamics using an effective kinetic description of QCD, following the evolution of a highly energetic parton from the hard momentum scales all the way to the medium scales, while keeping track of the recoil onto the medium [1-2]. We find that successive radiative emissions are important to develop a turbulent energy cascade which drives the fragmentation of energy to the medium scales and dominates the collinear region. Elastic interactions with the medium are more significant near medium scales, and primarily responsible for out-of-cone energy loss and the equilibration of the energy. We discuss the implications of our findings for phenomenological descriptions of jet quenching physics and studies of jet thermalization in heavy ion collisions.

[1]- S. Schlichting, I. Soudi, Fragmentation and equilibration of jets in a QCD plasma (8 2020).

[2] Y.Methar-Tani, S.Schlichting, I.Soudi, in preparation

Speakers: Soeren Schlichting (Universität Bielefeld), Dr ismail soudi (Wayne State University)

SSQMJetPoster.pdf

17:58 Measuring Jet Constituent Yields in 5.02 TeV Pb--Pb Collisions Using Jet-Hadron Correlations with ALICE

Hard partonic scatterings serve as an important probe of quark-gluon-plasma (QGP) properties. The properties of jets and their constituents can provide a tool for understanding the partonic energy loss mechanisms. Low momentum jets offer a unique window into partonic energy loss because they reconstruct the partons which have lost a significant amount of energy to the QGP medium. The main difficulty in studying low momentum jets in heavy ion collisions is the presence of a significant uncorrelated background of low momentum hadrons from soft processes. One way to deal with this background is to use jet-hadron correlations to fit and subtract the soft, flow-modulated background. This technique allows measurements of the near and away side yields. We present constituent yields for Pb--Pb collisions at $\sqrt{s_{NN}}$= 5.02 TeV. These yields are a measurement of the raw fragmentation function. We discuss prospects for unfolding the distributions of yields to get a corrected fragmentation function for low jet momenta.

Speaker: Charles Hughes (University of Tennessee (US))

Measuring Jet Constituent Yields in 5.02 TeV Pb-Pb Collisions Using Jet-Hadron Correlations with ALICE_v5.pdf

18:02 Search for large-angle jet deflection using semi-inclusive $\gamma_{\rm dir}$+jet and $\pi^{0}$+jet correlations in $p+p$ and Au+Au collisions at $\sqrt{s_\mathrm{NN}}$ =200 GeV with STAR

The measurement of jet deflection in heavy-ion collisions promises to provide unique and incisive insight into the physics of jet quenching and the quasi-particle nature of the QGP. However, observation of large-angle jet deflection favors using low transverse momenta ($p_{\rm T}$) jets, which is challenging in the high-background environment of heavy-ion collisions. The semi-inclusive approach to coincidence measurements, with data-driven background removal, is the only established analysis technique that can carry out such measurements with precision estimation of systematic uncertainties. In this poster, the STAR experiment at RHIC reports the first measurement of semi-inclusive $\gamma_{\rm dir}$+jet and $\pi^{0}$+jet azimuthal correlations in $p+p$ and central Au+Au collisions at $\sqrt s_{\rm NN}$=200 GeV. Charged-particle recoil jets are reconstructed using the anti-$k_{\rm T}$ algorithm with R = 0.2 and 0.5, and uncorrelated recoil jet contributions are corrected using a Mixed Event technique. Azimuthal distributions are reported for recoil jets with $p_{\rm T,jet} >$5 GeV/${\it c}$. The distributions in $p+p$ collisions are compared to NLO pQCD calculations including Sudakov broadening, and those in Au+Au collisions are compared to theoretical model calculations incorporating jet quenching.

Speaker: Dr NIHAR RANJAN Sahoo (Shandong University)

QM22poster_Nihar.pdf

18:06 3D structure of diffusion wake in high-energy hevay-ion collisions

Diffusion wake is a unique signal of the medium response which provides rich information of quark-gluon plasma in high-energy heavy-ion collisions. It can be characterized by a depletion of the azimuthal angle distribution of hadrons in the trigger direction in $\gamma$/Z jet events. However, this signal, if integrated over a large range of rapidity, can be overwhelmed by an enhancement of soft hadrons from multiple parton interaction (MPI) at the LHC energy, which is uniform in azimuthal angle. A recent 2D jet tomography can be applied to the event selection to enhance the path length of jet propagation and hence the signal of jet-induced diffusion wake. In this work, it is found that diffusion wake has a unique structure in the longitudinal direction and can be measured even without the assistance of 2D jet tomography at the LHC energy. We use an azimuthal cut to isolate hadrons affected by the diffusion wake and reduce contribution from the jet side. We find an unambiguous signal of diffusion wake. We further use a Gaussian fitting method to extract diffusion wake component and study its sensitivity to the properties of the dense QGP medium like flow and shear viscosity.

Speaker: Zhong Yang (CCNU)

3D_structure_of_jet_QM_ZY.pdf

meeting_01.mp4

18:10 Energy flow within jets in JEWEL simulations

Jets are excellent probes for the study of the deconfined matter formed in heavy ion collisions. In particular, jet substructure measurements can help us understand the interaction dynamics of high-energy partons with the quark-gluon plasma. We introduce a new infrared and collinear safe observable: jet energy flow measurements using jets reconstructed with different resolution parameters $R$. These measurements can help us gauge the competition between the dependence of energy loss on the opening angle of the shower on the one hand and the generation of large-angle fragments by radiative energy loss which give opposite trends for the R-dependence of the nuclear modification factor. In this poster we present a first measurement of jet energy flow in JEWEL simulations, and highlight its sensitivity to jet energy loss and medium recoil effects.

Speaker: Christos Pliatskas Stylianidis (Nikhef National institute for subatomic physics (NL))

Probing the fluctuations of energy flow within jets_QM22_CPliatskas_Animation-Free.pdf

Probing the fluctuations of energy flow within jets_QM22_CPliatskas.pdf

Probing the fluctuations of energy flow within jets_QM22_CPliatskas.pptx

17:30 → 18:30 Poster Session 1 T04_2

17:30 The primary Lund jet plane in pp collisions at 13 TeV with ALICE

Precision measurements of jet substructure are used as a probe of fundamental QCD processes. The primary Lund jet plane density is a two-dimensional visual representation of the radiation off the primary emitter within the jet that can be used to isolate different regions of the QCD phase space. We present a new measurement with the ALICE detector of the primary Lund plane density for inclusive charged-particle jets in pp collisions at $\sqrt{s} = $ 13 TeV, in the transverse momentum range [20,120] GeV/$c$.This is the first measurement of the Lund plane density in an intermediate jet $p_{\rm T}$ range where hadronization and underlying event effects play a dominant role. The projections of the Lund plane density onto the splitting scale $k_{\rm T}$ and splitting angle $\Delta{R}$ axis are shown, highlighting the perturbative/non-perturbative and wide/narrow angle regions of the splitting phase space. Through a 3D unfolding procedure, the Lund plane density is corrected for detector effects which allows for quantitative comparisons to MC generators to provide insight into how well generators describe different features of the parton shower and hadronization.

Speaker: Laura Brittany Havener (Yale University (US))

ALICELundPlane_QM2022Poster_Havener_v3.pdf

17:34 Exploiting jet topological differences in $pp$ and Au$+$Au collisions at $\sqrt{s_{\rm{NN}}}=200$ GeV at RHIC

Jets are algorithmic proxies of hard scattered quarks/gluons created in collisions of high energy particles. In the last few years, there has seen an explosion of jet substructure results from all experiments derived from exploiting clustering algorithms. Jet quenching via parton energy loss in heavy ion collisions is an established probe for exploring the properties of the quark-gluon plasma. Since jets are multi-scale objects, there is a need to characterize different likely mechanisms of medium interaction leading to energy loss for jets of varying shower topologies. In this talk, we present novel differential measurements of the jet shower in $pp$ collisions at $\sqrt{s_{\rm{NN}}} = 200$ GeV and discuss their connection to parton evolution. We then proceed to tag specific jet populations in Au$+$Au collisions based on jet substructure observables, such as opening angle and the splitting formation time calculated using the leading and subleading subjets or charged particles within the jet. These observables are shown to be experimentally robust to the heavy ion underlying event. With multiple jet classes based on their shower topology in central Au+Au collisions, we compare and contrast their energy loss via jet quenching observables such as dijet momentum asymmetry and recoil jet yield. With the topologically selected jet populations in central Au$+$Au collisions, we compare and contrast the jet energy via traditional jet quenching observables. Such measurements, for the first time, point towards a space-time study of energy loss phenomenon via selections on jet formation time and opening angle.

Speaker: Raghav Kunnawalkam Elayavalli

jet_time_angle_QM2022_poster_raghav_April2022.pdf

17:38 Machine learning assisted Jet tomography

We tried to locate the initial jet production positions in QGP, using the jet energy loss along the path length direction, the asymmetry perpendicular to the path length from gradient-tomography and the energy momentum distribution inside the jet with deep learning. These machine learning assisted Jet tomography help to locate the jet production positions with reasonable precision that helps us to look for Mach cones whose opening angles are direct measures of the QGP equation of state.

Speakers: LongGang Pang (Central China Normal University), Xin-Nian Wang (Lawrence Berkeley National Lab. (US))

17:42 Multi-scale probe of the jet-medium interaction via internal jet structure modification

We present the scale dependence of the jet-medium interactions seen in the modification of jet substructure observables in high-energy heavy-ion collisions by systematic studies with JETSCAPE 3, a publicly available software package of a framework for Monte Carlo event generators [1]. In high-energy heavy-ion collisions, jet partons interact with the quark-gluon plasma medium while changing their energy and virtuality via their shower evolution. Measured jets are reconstructed from the final state particles in the shower and thus carry information about the interactions with the medium at the various scales of the jet partons. The multi-stage framework for the jet evolution of JETSCPE is designed to cover a broader range of the scale in the in-medium parton shower evolution by stitching multiple models together; Each model becomes active depending on the virtuality or energy of a parton.

Recently, we found that the explicit virtuality dependence in the jet quenching strength qhat [2] at the early high-virtuality phase is essential for the simultaneous description of the experimental data for the reconstructed jet suppression and single-particle suppression. In this study, we perform numerical simulations with a model incorporating the virtuality-dependent formulation with MATTER+LBT setup within the JETSCAPE framework. We systematically study the observables characterizing internal structures of jets to explore the details of the strength of the interaction with the medium at each scale. In particular, we examine the splitting function, which displays the effect of the medium interaction with a parton with large virtuality at the very early stage, and the jet fragmentation function, which clearly shows the medium effect on partons throughout a wide range of scales.

[1] JETSCAPE Collaboration (A. Kumar et al.), Jet quenching in a multi-stage Monte Carlo approach, Nucl. Phys. A 1005, 122009 (2021); JETSCAPE Collaboration (A. Kumar et al.), JETSCAPE framework: p+p results, Phys. Rev. C 102, no.5, 054906 (2020).

[2] Amit Kumar, Abhijit Majumder, and Chun Shen, Energy and scale dependence of qhat and the JET puzzle, Phys. Rev. C, 101(3):034908, 2020.

Speakers: Antonio Silva, Christine Nattrass (University of Tennessee (US))

JETSCAPEQM22JetSubstructure.pdf

17:46 Constraints on jet quenching from a multi-stage energy-loss approach

The evolution of leading partons and jets through deconfined QCD matter is a multi-scale phenomenon and remains as one of the challenging problems in heavy-ion physics. To address this, we use the JETSCAPE framework [1] in which the production of the hard parton is factorized from the evolution of the produced QGP. To incorporate various scales involved in the jet-medium interaction during the different epochs of the parton shower, a multi-stage energy loss model is constructed [2]. We propose a new functional form of the transport coefficient $\hat{q}$ that weakens as the parton’s virtuality becomes larger and reduces to the traditional hard-thermal-loop (HTL) $\hat{q}$ at smaller virtuality [3]. In this talk, we demonstrate that a multi-stage jet quenching model with modified HTL $\hat{q}$ and recoil-hole based medium response are crucial for a simultaneous description of the nuclear modification factor for inclusive jets and leading hadrons at RHIC and LHC collision energies.

The study carried out also highlights one of the major successes of the JETSCAPE framework [1,2] in providing a tool to set up an effective parton evolution using a multi-stage energy-loss scheme. In this approach, the space-time information of the QGP is embedded in the parton shower during the high virtuality phase modeled using the MATTER event generator, followed by the low virtuality phase modeled by the LBT event generator. The switching between the jet energy loss stages is carried out on parton-by-parton basis based on the off-shellness or energy of the parton. The jet-medium response is incorporated through a weakly-coupled transport description with recoil particles excited from the QCD medium. The recoil-hole formalism shows sensitivity to the distribution of energy-momentum of particles inside the jet and hence puts further constraints on the jet quenching mechanism. The study presented demonstrates that the jet transport coefficient $\hat{q}$ indeed has a resolution scale dependence in addition to the conventional temperature and energy dependence encoded in hard-thermal-loop formula.

[1] JETSCAPE Collaboration (J. H. Putschke (Wayne State U.) et al.), The JETSCAPE framework, arXiv:1903.07706 [nucl-th] (2019).
[2] JETSCAPE Collaboration (A. Kumar et al.), Jet quenching in a multi-stage Monte Carlo approach, Nucl. Phys. A 1005, 122009 (2021); JETSCAPE Collaboration (A. Kumar et al.), JETSCAPE framework: p+p results,' Phys. Rev. C 102, no.5, 054906 (2020).
[3] Amit Kumar, Abhijit Majumder, and Chun Shen, Energy and scale dependence of q-hat and the JET puzzle. Phys. Rev. C, 101(3):034908, 2020.

Speaker: Abhijit Majumder (Wayne State University)

majumder_JETSCAPE_poster.pdf

17:50 Multi-dimensional measurements of the parton shower in pp collisions at RHIC

Jets are collimated sprays of hadrons and serve as an experimental tool for studying the dynamics of quarks and gluons. In particular, differential measurements of jet substructure enable a systematic exploration of the parton shower evolution. The SoftDrop grooming technique utilizes the angular ordered Cambridge/Aachen reclustering tree and provides a correspondence between the experimental observables such as the shared momentum fraction $(z_{\rm{g}})$, groomed jet radius or split opening angle $(R_{\rm{g}})$ and the QCD splitting functions in vacuum. In this poster, we present fully corrected correlations between $z_{\rm{g}}$ and $R_{\rm{g}}$ at the first split for jets of varying momenta and radii in $pp$ collisions at $\sqrt{s} = 200$ GeV. To study the evolution along the jet shower, we also present the splitting observables at the first, second and third splits along the jet shower for various jet and initiator prong momenta. As these novel measurements are presented in three dimensions, we outline the correction procedure so that it can be used as a template for future multi-differential measurements across all experiments.

Speaker: Monika Robotková (Nuclear Physics Institute, Czech Academy of Sciences)

QM2022_poster_slides_Robotkova.pdf

17:54 The Improved Opacity Expansion formalism

So far, analytical jet quenching formalisms have either assumed that modifications to the jets’ structure are dominated by a few hard in-medium scatterings or by multiple soft interactions. However, it is known that neither of these regimes corresponds to any currently available experimental set-up, and thus bridging the gap between these limits under a single framework is a crucial step towards a complete description of jet quenching. In this talk we discuss a novel strategy, dubbed the Improved Opacity Expansion (IOE), which provides a self consistent way of interpolating between the single hard and multiple soft regimes for dense media populated by a few hard scattering centers. We compute the momentum broadening distribution and the medium induced radiation rate in the IOE, showing that the two previous limits are recovered. As an application, we show how the IOE allows to take into account Moliere scattering in the computation of jet substructure observables

Speaker: João Barata

17:58 Dijet invariant mass measurement for pp and p-Pb at $\sqrt{s_\mathrm{NN}}=5.02$ TeV with ALICE

Properties of dijets may provide sensitive probes of jet quenching in Quark-Gluon Plasma. Dijet invariant mass measurements in small systems provide an essential baseline for such studies in Pb-Pb collisions. In this poster, we present the first measurements of dijet invariant mass in minimum bias pp and p-Pb collisions at $\sqrt{s_\mathrm{NN}}=5.02$ TeV by ALICE. Jets are clustered using the anti-$k_\mathrm{T}$ algorithm with $R=0.4$, and an azimuthal angle of $\pi/2$ at mininum between the two jets. The dijet invariant mass is measured in the low mass range from $80$ to $150$ GeV/$c^2$.

Speaker: Oskari Antti Matti Saarimaki (Helsinki Institute of Physics (FI))

Dijet-mass-poster-Oskari-Saarimaki-v3.pdf

18:02 Data-driven extraction of quark and gluon jet substructure

The different modification of quark- and gluon-initiated jets in the quark-gluon plasma produced in heavy-ion collisions is a long-standing question that has not yet received a definitive answer from experiments. In particular, the relative sizes of the modification of quark and gluon jets differ between theoretical models. Therefore a fully data-driven technique is crucial for an unbiased extraction of the quark and gluon jet spectra and substructure. We perform a proof-of-concept study based on proton-proton and heavy-ion collision events from the PYQUEN generator with statistics accessible in Run 4 of the Large Hadron Collider. We use a statistical technique called topic modeling to separate quark and gluon contributions to jet observables. We demonstrate that jet substructure observables, such as the jet shape and jet fragmentation function, can be extracted using this data-driven method. These results suggest the potential for an experimental determination of quark and gluon jet spectra and their substructure.

Speaker: Yueyang Ying (Massachusetts Inst. of Technology (US))

Yueyang_Ying_TopicModeling_QM2022.pdf

Yueyang_Ying_TopicModeling_QM2022.pptx

18:06 Energy loss of leading jets - from LEP to the LHC

Different than for inclusive jets, leading jet cross sections constitute normalized probability distributions for the leading jet to carry a longitudinal momentum fraction relative to the initial fragmenting parton. The formation and evolution of leading jets can be described by jet functions that satisfy non-linear DGLAP-type evolution equations. We present a parton shower algorithm that allows for the systematic calculation of leading-jet cross sections where logarithms of the jet radius and threshold logarithms are resummed to next-to-leading logarithmic (NLL) accuracy. By calculating the mean of the leading jet distribution, we are able to quantify the average out-of-jet radiation, the so-called jet energy loss. When an additional reference scale is measured, we are able to determine the energy loss of leading jets at the cross section level which is identical to parton energy loss at leading-logarithmic accuracy. We present comparisons to the first direct measurements of vacuum and medium-induced energy loss at LEP and the LHC in proton-proton and heavy-ion collisions.

[1] Neill, Ringer, Sato: JHEP 07 (2021) 041, arXiv 2103.16573

Speaker: Felix Ringer (Stony Brook University)

18:10 Measurement of b-jets in 5.02 TeV pp collisions by ALICE using ML

Heavy-flavour (charm and beauty) jets are excellent probes to study Quantum Chromodynamics (QCD). Their precise measurements in proton-proton collisions are used to verify perturbative QCD calculations and improve our modelling capabilities by constraining Monte Carlo generators. They also serve as the reference measurements for more complex systems such as Pb–Pb collisions, helping to disentangle various energy loss mechanisms and their dependence on the quark mass.

In this contribution, we present a measurement of $b$-jets in pp collisions at $\sqrt{s} = 5.02$ TeV using a machine-learning-based method. This method, which utilizes the long lifetime of beauty hadrons, was chosen to optimize $b$-jet tagging performance in terms of efficiency and purity. It also provides flexibility in the working point selection, enabling smooth switching from high efficiency to high purity settings. The projected performance gain, with enhanced $b$-jet purity relative to other approaches, will enable methodologically consistent measurements in Pb–Pb collisions, and more differential jet studies in pp collisions.

Speaker: Sebastian Bysiak (Institute of Nuclear Physics Polish Academy of Sciences (PL))

sbysiak_bjets.pdf

18:14 Systematic study of fractional momentum loss in the QGP for various collision systems at PHENIX

The phase transition from hadronic matter to quark-gluon plasma (QGP) is a phenomenon that occurs under extreme conditions of high temperature and high density, as achieved at the relativistic heavy ion collider (RHIC). The QGP causes energy loss of high momentum particles which is observed as suppression of high momentum hadron production in A+A collisions relative to p+p collisions. The study presented in this poster uses PHENIX data to evaluate the energy loss of partons in the QGP in the various collision systems provided by RHIC.
We measure the fractional momentum loss with two quantities, Sloss and S’loss. Sloss is obtained by comparing the inclusive $p_\textrm{T}$ spectra in the A+A and p+p collisions. In contrast, S’loss is obtained by comparing in-plane and out-of-plane spectra using the azimuthal anisotropy $v_2$. These quantities are extracted from PHENIX data in Au+Au, Cu+Au, and Cu+Cu collisions at $\sqrt{s_{\textrm{NN}}}$ = 200 GeV for $\pi^0$s, and the Au+Au collisions at $\sqrt{s_{\textrm{NN}}}$ = 200 GeV for charged hadrons. The interpretation of these results and their impact on our understanding of the path length dependence of energy loss in the QGP will be discussed.

Speaker: Dr Maya Shimomura (Nara Women's University (JP))

QM2022_poster_MS.pdf

18:18 Quark-flavour dependence of jet quenching in hot QCD matter

The jet transverse momentum diffusion coefficient $\hat{q}$ is an important transport coefficient governing the radiative energy loss of a parton propagating the Quark-Gluon Plasma (QGP) created in Heavy-Ion Collisions. Based on perturbative arguments [1], which were recently extended to next-to-leading order [2], the dimensionless ratio $\hat{q}/T^3$ was shown to be connected with the dimensionless specific shear viscosity $\eta/s$. This connection requires two assumptions: (a) that the medium is describable in terms of quasiparticle excitations, and (b) that the mean-free path of the parton is related to the average transport cross section of a quasiparticle in the medium implying that the interaction with the medium constituents is of the same form and strength as the interaction among the quasiparticles themselves.

Based on this idea, results of a microscopic calculation of $\hat{q}$ are presented by applying a quasiparticle model that was shown to provide a successful, effective description for the strongly coupled QGP [3]. This approach allows the determination of $\hat{q}$ in dependence of the identity of the traversing highly energetic parton and the composition of the hot strongly interacting matter. The behaviour of the jet quenching parameter as a function of temperature and parton momentum is discussed also in comparison with a recent Bayesian parameter estimation by the JETSCAPE Collaboration [4].

[1] A. Majumder, B. Müller and X. N. Wang, Phys. Rev. Lett. 99 (2007), 192301.
[2] B. Müller, Phys. Rev. D 104 (2021) no.7, L071501.
[3] V. Mykhaylova, M. Bluhm, K. Redlich and C. Sasaki, Phys. Rev. D 100 (2019) no.3, 034002.
[4] J. Mulligan et al. [JETSCAPE], arXiv:2106.11348 [nucl-th].

Speaker: Dr Marcus Bluhm (SUBATECH, Nantes)

17:30 → 18:30 Poster Session 1 T05_1

17:30 Interplay between core and corona from small to large systems

Motivated by experimental results implying the possible QGP (quark-gluon plasma) formation in small colliding systems, we extend the hydro-based framework incorporating non-equilibrated components which play an essential role in small colliding systems. It has been widely accepted that relativistic hydrodynamics well describes the dynamics of the QGP at low $p_{\mathrm{T}}$ regimes in large colliding systems. Hence hydro-based frameworks are used to tease out properties of the QGP in high-energy heavy-ion collisions. In contrast, particle productions in small colliding systems have been studied through QCD-motivated phenomenological models such as perturbative QCD (semi-)hard processes followed by string fragmentation. As keeping these pictures in each regime, the ``marriage" of relativistic hydrodynamics and QCD-motivated phenomenological framework is indispensable to explore the dynamics over wide ranges of colliding systems.

We realize this as the dynamical core--corona initialization framework (DCCI) [1-3]. In DCCI, QGP fluids are generated from initial partons obtained from PYTHIA/PYTHIA Angantyr [4-5] which reflects the total energy-momentum of incoming nuclei. We phenomenologically describe the fluidization of the initial partons with the dynamical aspects of the core--corona picture. Partons with sufficient secondary scatterings tend to generate QGP fluids (core) as equilibrated matter.
While partons with insufficient secondary scatterings tend to survive as non-equilibrated matter (corona). This framework is, so to speak, the hydrodynamic afterburner for PYTHIA. By treating both locally equilibrated QGP fluids and non-equilibrated matter, the DCCI, as a hydro-based Monte Carlo event generator, is capable of describing from low to high $p_{\mathrm{T}}$, from backward to forward rapidity, and from small to large colliding systems.

In this talk, we investigate the interplay between core and corona components in high-energy nuclear collisions using DCCI. We reveal that the particle production from the core becomes dominant above $\langle dN_{\mathrm{ch}}/d\eta \rangle \sim 18$ regardless of the system size and the collision energy. Remarkably, the corona components turn out to dilute $\langle p_T \rangle$ and $v_2\{2\}$ obtained from the core components even in Pb--Pb collisions in which the entire system is often assumed to be locally equilibrated. These results suggest the importance of both equilibrated and non-equilibrated contributions in both small and large colliding systems towards an accurate understanding of the QGP properties.

[1] Y. Kanakubo, M. Okai, Y. Tachibana, and T.~Hirano, PTEP 2018, 121D01 (2018).
[2] Y. Kanakubo, Y. Tachibana, and T. Hirano, Phys.~Rev.~C101, 024912 (2020).
[3] Y. Kanakubo, Y. Tachibana, and T. Hirano, arXiv:2108.07943 [nucl-th].
[4] T. Sj\"{o}strand, S. Mrenna, and P. Z. Skands, Comput. Phys. Commun. 178, 852 (2008).
[5] C. Bierlich, G. Gustafson, L. L\"{o}nnblad, H. Shah, JHEP 10 134 (2018).

Speaker: Yuuka Kanakubo

QM2022poster_yuuka.pdf

QM2022poster_yuuka.pptx

17:34 Event shape and multiplicity dependence of K*(892)$^{\pm}$ mesons at midrapidity in pp collisions at $\sqrt{s}$ = 13 TeV with ALICE at the LHC

Short-lived resonances can probe strongly interacting matter produced in high-energy heavy ion collisions. K$^{*}(892)^{\pm}$ resonance is particularly interesting because of its very short lifetime (∼ 4 fm/c), comparable to the one of the hadronic phase. Therefore, it may be sensitive to the competing rescattering and regeneration mechanisms which modify the particle’s momentum distributions after hadronization. In this poster, recent measurements of resonance production in proton proton (pp) collisions as a function of event multiplicity and transverse spherocity will be presented, exploiting the large sample of pp collisions at $\sqrt{s}$ = 13 TeV collected by ALICE. These measurements show the onset of phenomena typical of heavy-ion collisions, like collective behaviour and suppression of the yield ratios of short-lived resonances to stable particles with increasing multiplicity. In addition, new preliminary results for charged-particle multiplicity dependent studies of K*(892)$^{\pm}$ production in pp collisions will also be presented.

Speakers: Antonina Rosano (Universita e INFN, Catania (IT)), Suman Deb (Indian Institute of Technology Indore (IN))

QM2022_Poster_Rosano_Deb.pdf

17:38 Multiplicity dependent study of $\Lambda(1520)$ production in pp collisions at $\sqrt{s}$ = 5.02 and 13 TeV with ALICE

Hadronic resonances are effective tools for studying the hadronic phase in ultra-relativistic heavy-ion collisions. In fact, their lifetime is comparable to the hadronic phase and resonances are sensitive to the hadronic phase effects such as re-scattering and regeneration processes which might affect the resonance yields and shape of the transverse momentum spectra. $\Lambda(1520)$ has a lifetime of around 13 fm/$\it{c}$, which lies in between the lifetimes of $K^*$ and $\Phi$ resonance. The resonance to stable particle yield ratios can be used to study the properties of the hadronic phase. Recently, ALICE observed the suppression of the $\Lambda(1520)/\Lambda$ ratio in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV as a function of centrality. It is therefore interesting to investigate the multiplicity dependent study of $\Lambda(1520)/\Lambda$ ratio for pp collisions, since this can serve as a baseline for heavy-ion collisions.

In this contribution, we present new results on the measurement of the baryonic resonance $\Lambda(1520)$ as a function of charged-particle multiplicity in pp collisions at $\sqrt{s}$ = 5.02 and 13 TeV. The transverse momentum spectrum, the integrated yield $< dN/dy >$, the average ${\textit{p}_{\rm T}}$ $<{\textit{p}_{\rm T}}>$ and the $ \Lambda(1520)/\Lambda$ yield ratio will be presented as a function of charged-particle multiplicity.

Speaker: Sonali Padhan (IIT- Indian Institute of Technology (IN))

Lambda1520_pp_QM22_SonaliPadhan.pdf

17:42 Measurement of ψ(2S) production as a function of charged-particle multiplicity in pp collisions at √s =13 TeV and p--Pb collisions at √sNN = 8.16 TeV with ALICE at the LHC.

Recent measurements reveal that J/ѱ yields increase with increasing charged-particle multiplicity in pp and p—Pb collisions at the LHC. Different mechanisms have been proposed to explain this observation. One of them is the influence of multiple parton interactions (MPI) in the initial state of the collision. Measurements of the excited charmonia, as the ѱ(2S) state, state as a function of charged-particle multiplicity are important to disentangle the impact of possible final-state effects.

This poster presents the measurement of charmonium yields in pp collisions at √s = 13 TeV and p—Pb collisions at √sNN = 8.16 TeV as a function of charged-particle multiplicity. J/ѱ and ѱ(2S) are reconstructed in their dimuon decays within rapidity window -4.0 < ylab < -2.5. Charmonia yields are normalised to their respective average values. The charged-particle multiplicity is measured at central rapidity and also normalised to its average value. The excited-to-ground state ratio is also shown. Results are compared with model calculations.

Speaker: Theraa M A Tork (Université Paris-Saclay (FR))

TTork_QM_poster.pdf

17:46 J/$\psi$ production as a function of the charged-particle multiplicity by regions of azimuth angle in pp collisions at $\sqrt{s}$=13 TeV measured with ALICE

Previous ALICE publications have shown, in pp collisions at the LHC, an increase of the inclusive J/$\psi$ yields as a function of charged-particle multiplicity. Such an increase was found to be stronger than linear, and both J/$\psi$ and multiplicity were measured at midrapidity. The causes for this behavior have been investigated in previous studies with PYTHIA8 and attributed to possible auto-correlation effects. Insight on this effect could be gained by measuring the charged-particle multiplicity in three azimuth regions relative to the direction of the J/$\psi$.

Data collected with ALICE at the LHC during Run 2 is used to investigate the relative J/$\psi$ yield, measured at mid-rapidity (|y|<0.9) in its di-electron decay channel and as a function of the charged-particle multiplicity, in various regions of the azimuthal angle with respect to the emission of the J/$\psi$ meson.

In this contribution, new measurements of this correlation performed in pp collisions at $\sqrt{s}$=13 TeV TeV will be shown.

Speaker: Ailec Bell Hechavarria (Westfaelische Wilhelms-Universitaet Muenster (DE))

17:50 Event topology and multiplicity dependence of charmed hadron production in Proton+Proton Collisions at $\sqrt{s}$ = 13 TeV using pQCD inspired model

Heavy-flavor hadrons, containing charm and beauty flavors are believed to be vital probes for the understanding of Quantum Chromodynamics (QCD) in high-energy hadronic collisions: right from the study of production mechanisms in proton-proton ($pp$) collisions to the investigation of Cold Nuclear Matter (CNM) effects in proton-nucleus (p--A) collisions and their suppression in the search of Quark Gluon Plasma (QGP) in nucleus-nucleus (A--A) collisions. Recently, the observation of heavy-ion-like features in small systems ($pp$ and p$-$A) like collective-like phenomena, strangeness enhancement etc, continues to generate considerable interest in the scientific community. In this regards, a cruial question arises, whether the QGP-like phenomena involve all the particles in the system or it is the effect of contributions from the processes like resonance decays, jets, underlying events (UE) etc. Therefore, small systems need to be re-investigated properly including the light and heavy-flavor sectors. In the present work, using transverse spherocity, one of the event-topology variables used to separate jetty and isotropic events from the pool of event samples, we aim to understand the production dynamics of heavy-flavors through the transverse momentum spectra, double differential yield and mean transverse momentum of J/$\psi$, $\rm D^{0}$ and $\Lambda_{c}^{+}$ as a function of charged-particle multiplicity. For the current analysis, the events are generated by using 4C tuned PYTHIA8 for $pp$ at $\sqrt{s}$ = 13 TeV, which is quite successful in explaining the heavy-flavor particle production at the LHC energies. We observe a clear dependence of spherocity on the production of J/$\psi$, $\rm D^{0}$ and $\Lambda_{c}^{+}$.

Speaker: Suman Deb (Indian Institute of Technology Indore (IN))

17:54 Azimuthal correlations in photoproduction and deep inelastic ep scattering at HERA

Collective behaviour of final-state hadrons, and multiparton interactions are studied in high-multiplicity 𝑒𝑝 scattering at a centre-of-mass energy 𝑠√=318 GeV with the ZEUS detector at HERA. Two- and four-particle azimuthal correlations, as well as multiplicity, transverse momentum, and pseudorapidity distributions for charged-particle multiplicities 𝑁ch≥20 are measured. The dependence of two-particle correlations on the virtuality of the exchanged photon shows a clear transition from photoproduction to neutral current deep inelastic scattering. For the multiplicities studied, neither the measurements in photoproduction processes nor those in neutral current deep inelastic scattering indicate significant collective behaviour of the kind observed in high-multiplicity hadronic collisions at RHIC and the LHC. Comparisons of PYTHIA predictions with the measurements in photoproduction strongly indicate the presence of multiparton interactions from hadronic fluctuations of the exchanged photon.

Speaker: Dr Dhevan Gangadharan (University of Houston (US))

QM2022_Dhevan.pdf

17:58 Exploring origins for correlations between flow harmonics and transverse momentum in small collision systems

High statistics data sets from experiments at RHIC and the LHC with small and large collision species have enabled a wealth of new flow measurements, including the event-by-event correlation between observables. One exciting such observable $\rho$($v^2_n$,[$p_T$]) gauges the correlation between the mean transverse momentum ($p_T$) of particles in an event and the various flow coefficients ($v_n$) in the same event. Recently it has been proposed that very low multiplicity events may be sensitive to initial-state glasma correlations rather than flow-related dynamics. We find utilizing the IP-JAZMA framework that the color domain explanation for the glasma results are incomplete. We then explore predictions from PYTHIA-ANGANTYR having only non-flow correlations and AMPT having both non-flow and flow-type correlations. We find that PYTHIA-ANGANTYR has non-flow contributions to $\rho$($v^2_n$,[$p_T$]) in $p$+O, $p$+Pb, O+O collisions that are positive at low multiplicity and comparable to the glasma correlations. It is striking that in PYTHIA-8 in $pp$ collisions there is actually a sign-change from positive to negative $\rho$($v^2_n$,[$p_T$]) as a function of multiplicity. The AMPT results match the experimental data general trends in Pb+Pb collisions at the LHC, except at low multiplicity where AMPT has the opposite sign. In $p$+Pb collisions, AMPT has the opposite sign from experimental data and we explore this within the context of parton geometry. In this presentation, we will discuss the detailed model study on the $v_n$-$p_T$ correlation in [Phys. Rev. C 103, 064906 (2021)]

Speakers: Sanghoon Lim (Pusan National University (KR)), James Lawrence Nagle (University of Colorado Boulder)

QM22poster_shlim_vnpt.pdf

18:02 Checking Non-Flow Assumptions and Results via PHENIX Published Correlations in p+p, p+Au, d+Au, 3He+Au at 200 GeV

Recently the PHENIX Collaboration has made available two-particle correlation Fourier coefficients for multiple detector combinations in minimum bias p+p and 0-5% central $p$+Au, $d$+Au, $^3$He+Au collisions at 200 GeV (arXiv:2107.06634). Using these coefficients for three sets of two-particle correlations, azimuthal anisotropy coefficients $v_2$ and $v_3$ are extracted for midrapidity charged hadrons as a function of transverse momentum. As discussed in arXiv:2107.07287 and in this talk, we use the available coefficients to explore various non-flow hypotheses as well as compare the results with theoretical model calculations. The non-flow methods fail basic closure tests with AMPT and PYTHIA/ANGANTYR, particularly when including correlations with particles in the low multiplicity light-projectile going direction. In data, the non-flow adjusted $v_2$ results are modestly lower in $p$+Au and the adjusted $v_3$ results are more significantly higher in $p$+Au and $d$+Au. However, the resulting higher values for the ratio $v_3/v_2$ in p+Au at RHIC compared to p+Pb at the LHC is additional evidence for a significant over-correction. Incorporating these additional checks, the conclusion that these flow coefficients are dominated by initial geometry coupled with final-state interactions (e.g.~hydrodynamic expansion of quark-gluon plasma) remains true, and explanations based on initial-state glasma are ruled out. The detailed balance between intrinsic and fluctuation-driven geometry and the exact role of weakly versus strongly-coupled pre-hydrodynamic evolution remains an open question for triangular flow, requiring further theoretical and experimental investigation.

Speaker: Ron Belmont (University of North Carolina at Greensboro)

poster.pdf

18:06 Strange particle production in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 8.16 TeV with ALICE at the LHC

The main goal of the ALICE experiment is to study the physics of strongly interacting matter, including the properties of the Quark-Gluon Plasma (QGP). The relative production of strange hadrons with respect to non-strange hadrons in heavy-ion collisions was historically considered one of the signatures of QGP formation. However, recent measurements in proton-proton (pp) and proton-lead (p-Pb) collisions have shown features that are reminiscent of those observed in lead-lead (Pb-Pb) collisions, exhibiting an increase in the production of strange hadrons relative to pions with the charged particle multiplicity in the event.

We report the new preliminary mid-rapidity measurement of the transverse momentum spectra and yields of ${\rm K^{0}_{s}}$, $\Lambda$ and $\bar \Lambda$ in the p-Pb collision system at $\sqrt{s_{\rm NN}}$ = 8.16 TeV. Results have been obtained in several multiplicity bins, so that a comparison to lower energy p-Pb results and to similar measurements in pp and Pb-Pb collisions can be performed. Finally, the comparison to phenomenological models will be discussed.

Speaker: Meenakshi Sharma (University of Jammu (IN))

Qm_Poster_2022.pdf

18:10 Centrality dependence of jet properties in p-Pb collisions at 5.02 TeV with ALICE

Jets are collimated sprays of particles produced from the fragmentation and hadronization of hard-scattered partons in high energy hadronic and nuclear collisions. Jet properties are sensitive to details of parton showering processes and expected to get modified in the presence of a dense partonic medium. Recently features similar to those in heavy-ion collisions have been observed in high multiplicity events in small collision systems, however, the suppression of inclusive jet production cross section is found to be absent. Measurements of jet properties can shed light on the current understanding of the observed behavior of high multiplicity events in such systems. In this work, we will present the centrality dependence of charged jet properties, viz. mean charged particle multiplicity, transverse momentum profile and fragmentation functions for leading jets in the range of jet $p_{\rm T}$ from 10 – 120 GeV/c at midrapidity in p-Pb collisions at 5.02 TeV with ALICE.

Speaker: Prottoy Das (Bose Institute (IN))

2022-04-06-QM_poster_ChargedJetProp_pPb5pt02TeV_ALICE_ProttoyDas.pdf

18:14 Charged-particle jet properties and their multiplicity dependence in pp collisions at $\sqrt{s}$ = 13 TeV with ALICE

Recent results in high-multiplicity pp collisions show interesting features similar to those that are associated to the formation of a quark-gluon plasma in heavy-ion collisions [1]. Investigating the modification of the intra jet properties as a function of event multiplicity in pp collisions can provide deeper insight into the nature of these effects.

We will present the latest results of multiplicity dependence of charged-particle jet properties (average charged particle multiplicity, radial transverse momentum density and fragmentation functions) for leading charged-particle jets reconstructed using anti-$k_{\rm T}$ jet finding algorithm with radius parameter $R$ = 0.4 in the jet $p_{\rm T}$ range from 10 - 120 GeV/$c$ at midrapidity in pp collisions at $\sqrt{s}$ = 13 TeV with ALICE.

[1] Vardan Khachatryan et al. Phys. Lett. B 765 (2017), JHEP 09 (2010).

Speaker: Ms Debjani Banerjee (Bose Institute (IN))

JetProperties_pp13TeV_DebjaniBanerjee_QM22.pdf

18:18 Exploring system-size dependence of jet production and internal jet properties in pp and p-Pb collisions with ALICE

Internal properties of jets and their production in small collision systems (pp and p--Pb) are tightly connected to perturbative and non-perturbative aspects of quantum chromodynamics (QCD), such as cold nuclear matter effects. Recent studies of high-multiplicity final states of small collision systems also exhibit signatures of collective effects that are thought to be associated with hot and dense, color-deconfined QCD matter, which is known to be formed in collisions of heavier nuclei. The absence to date of jet quenching signals raises a question about the origin of the observed collectivity and calls for more accurate jet quenching measurements in small collision systems. ALICE is uniquely positioned to do precise charged-particle jet measurements due to its high efficiency in the reconstruction of charged particles.

In this contribution, we will report new results on charged-particle jet production in p-Pb and pp collisions at $\sqrt{s_{\rm{ NN}}}=5.02$ TeV measured by ALICE in LHC Run 2. The data extend the transverse momentum range and jet cone radius span of previous measurements of $p_{\rm T}$ differential cross section spectra and nuclear modification factor $R_{\rm{pPb}}$ published by ALICE. In addition, the multiplicity dependence of charged-particle jet properties (mean charged-constituent multiplicity, transverse momentum profile and fragmentation functions) in p-Pb and pp collisions at $\sqrt{s_{\rm{NN}}}=5.02~\rm{TeV}$ and $\sqrt{s_{\rm{ NN}}}=13~\rm{TeV}$ respectively will also be presented and compared to predictions of theoretical models.

Speaker: Haidar Mas'ud Alfanda (Central China Normal University CCNU (CN))

HaidarQM22Poster.pdf

18:22 Searching for viscous effects in small systems with ALICE

Two-particle differential correlators of particle numbers ($R_2$) and particle transverse momenta ($P_2$ and $G_2$), recently measured in Pb-Pb collisions, emerged as powerful tools to gain insights into particle production mechanisms and infer transport properties such as the ratio of shear viscosity to entropy density of the medium created in Pb-Pb collisions. In this talk, recent ALICE measurements of these correlators in pp collisions at $\sqrt{s}$ = 7 and 13 TeV and p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV are presented to provide baseline references to measurements in Pb-Pb collisions and seek evidence, in particular, for viscous effects expected to arise in fluid-like systems produced in these collisions. Additionally, these measurements in small systems also probe particle correlations associated with jets as well as low-$p_{\rm T}$ processes and their change with system size. The strength and shape of the correlators are studied as a function of produced particle multiplicity to identify evidence for longitudinal broadening that might reveal the presence of viscous effects in these smaller systems. The measured correlators and their evolution from pp and p-Pb to Pb-Pb are additionally compared to predictions from Monte Carlo models, and the potential presence of viscous effects is discussed.

Speaker: Victor Gonzalez (Wayne State University (US))

2022-04-03-SmallSystemsV5d.pdf

18:26 Search for jet quenching effects in high-multiplicity proton-proton collisions at $\sqrt{s} = 13~\rm{TeV}$ with ALICE

The ALICE Collaboration presents results of a search for jet quenching effects in high multiplicity pp collisions at $\sqrt{s} = 13~\rm{TeV}$ by measuring the semi-inclusive acoplanarity distribution of charged-particle jets that recoil from a high transverse momentum trigger-track. The search for jet quenching is performed by comparing the acoplanarity distributions measured in high multiplicity and minimum bias events. High multiplicity events are selected by online trigger based on a signal amplitude measured in the forward V0 scintillator detectors. Removal of background jet yield uncorrelated with a trigger-track is performed utilizing a data-driven statistical approach.

In this poster, we will show that the acoplanarity distributions, measured in high multiplicity events, exhibit a marked suppression and broadening when compared to the corresponding distributions obtained from minimum bias events. The distributions are corrected for momentum smearing due to instrumental effects. The observed features are not caused by jet quenching, since they can be reproduced by PYTHIA 8 event generator, which does not account for jet quenching. Analysis of the PYTHIA events reveals that the suppression and broadening of the hadron-jet acoplanarity distributions are the consequence of a bias induced by the ALICE high multiplicity trigger.

Speaker: Artem Kotliarov (Czech Academy of Sciences (CZ))

QM2022_Poster_Kotliarov.pdf

17:30 → 18:30 Poster Session 1 T05_2

17:30 Elliptic and triangular flow of identified particles in p–Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02$ TeV

In heavy-ion collisions at relativistic energies, a hot and dense medium called quark-gluon plasma (QGP) is created. Intriguingly, the collective motion of produced particles, which is thought to be a strong evidence of the formation of QGP, is also seen in small systems like pp and p–Pb collisions. Such a study can be done in the ALICE experiment at the LHC via long-range two-particle correlations. In this poster, we discuss how to determine the flow coefficients in pp and p–Pb collisions using the template fit method to subtract non-flow contributions based on examination of the method with event generators. A model study to understand the flow of identified particles like $\pi$, $K$, and $p$ is discussed as well.

Speaker: Su-Jeong Ji (Pusan National University (KR))

2022_QM_Su_final.pdf

17:34 Multiplicity dependence of low mass resonance production at forward rapidity in pp collisions with ALICE

Recently, many results suggesting the production of Quark-Gluon Plasma (QGP) in high multiplicity events in small collision systems have been presented. These results were reported with surprise and have been a topic of intense discussion.
The purpose of the analysis presented in this talk is to look for the possibility of QGP formation in small collision systems through the measurement of low-mass vector mesons ($\rho$, $\omega$, $\phi$) decaying in the lepton pair channel. The analysis focuses on forward-rapidity muons instead of mid-rapidity electrons since the ALICE muon tracking system at forward rapidity allows for high-purity muon identification and momentum measurement to low transverse momentum. In addition, thanks to a dedicated muon pair trigger, it has been possible to enhance efficiently the sample of muon pairs.
This presentation will report the multiplicity and transverse momentum dependence of the low-mass vector meson production in pp collisions at √s = 13 TeV with full LHC-Run2 (2015-2018) data.

Speaker: Satoshi Yano (Hiroshima University (JP))

0406_syano_QM_slide_v4.pdf

17:38 Probing QGP medium effect on jet observables in small systems with AMPT $+$ new hadronization model

Jet observables, including jet fragmentation transverse momentum $j_{\rm T}$, parallel momentum $p_{\left|\right|}$, jet fragmentation function $\xi$ and jet constituent transverse momentum $p_{\rm T, track}$ distributions, have been investigated in p $+$ p and p $+$ Pb collisions at $\sqrt{s_{\rm NN}} = 5.02~{\rm TeV}$ via a multiphase transport model (AMPT) [1,2] with new hadronization model which contains both dynamical quark coalescence and fragmentation schemes [3]. With the new hadronization model, the recent ALICE measurements of $j_{\rm T}$ distributions can be quantitatively described, especially for low and intermediate $j_{\rm T}$ regions. We observe that high-energy jets have more large-$j_{\rm T}$ particles than low-energy jets, which are consistent with the experimental measurements. Importantly, the predicted ratio of $j_{\rm T}$ distributions between p $+$ Pb and p $+$ p shows a sizeable enhancement above unity of low-$j_{\rm T}$ particles and a suppression of intermediate-$j_{\rm T}$ particles, which indicates the possible effects from jet-medium interactions in small systems. This jet observable is suggested to probe the QGP medium effects in small systems in this talk. On the other hand, the $p_{\left|\right|}$ ratio of jet distribution is proposed as a complementary observable to probe jet-medium response in small systems.

We also implement jet fragmentation $\xi$ and $p_{\rm T, track}$ distributions and compare to CMS measurements. The similar enhancement of soft jet particles and suppression of hard jet particles appear in both new hadronization model and original AMPT hadronization model, which demonstrate that this enhancement (suppression) is model independent. We also systematically study the difference between two hadronization models, and find out that it is important for studying jet observables in small systems with a proper hadronization scheme.

[1] X.-P. Duan, W. Zhao, G.-L. Ma, "Probing QGP medium effect on jet observables in small systems with AMPT $+$ new hadronization model", arXiv:2021.xxxx.
[2] Z.-W. Lin, C. M. Ko, B.-A. Li, B. Zhang, and S. Pal, "Multiphase transport model for relativistic heavy ion collisions", Phys. Rev. C 72, 064901 (2005).
[3] W. Zhao, C. M. Ko, Y.-X. Liu, G.-Y. Qin, and H. Song, "Probing the Partonic Degrees of Freedom in High-Multiplicity $p$-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV", Phys. Rev. Lett. 125, 072301 (2020).

Speaker: Xiang-Pan Duan (Fudan University)

QM2022_Duan.pdf

17:42 Probing the multiplicity dependence of strangeness enhancement in pp collisions in the regime of low multiplicity and transverse spherocity with ALICE

ALICE is the experiment at the LHC specifically designed to study the properties of the quark-gluon plasma (QGP), a deconfined state of matter created in ultrarelativistic heavy-ion collisions. In this context, light-flavour particle production measurements play a key role, as they can probe statistical hadronization and partonic collectivity. Recent measurements in small colliding systems (pp and p-Pb) highlight an enhancement of produced strange hadrons with increasing multiplicities.

How do we further probe whether the multiplicity in itself is the driving force behind this effect? In this contribution we will study the production of strange light-flavour hadrons at low-multiplicity in pp collisions at $\sqrt(s)=5.02$ TeV, extending at low multiplicity the observations reported in pp, p-Pb and A-A interactions, in order to probe the onset of strangeness enhancement.

In contrast, this contribution we will discuss light-flavour particle production in pp collisions at $\sqrt(s)=13$ TeV, constrained to high multiplicities as a function of event topology. The event topology in this analysis is estimated through the transverse spherocity, which categorizes events based on the azimuthal distribution of tracks. The transverse spherocity is sensitive to the hard and soft processes and is a useful tool to distinguish the isotropic and jet dominated events in pp collisions. The interplay between multiplicity and transverse spherocity classes on light-flavour production can be understood by comparing the results obtained from the extreme selection of multiplicity and/or transverse spherocity.

These measurements will be compared with the Monte Carlo (MC) predictions obtained from models such as PYTHIA 8 and Herwig7.

Speakers: Adrian Fereydon Nassirpour (Lund University (SE)), Rutuparna Rath (Indian Institute of Technology Indore (IN))

QM2022_v4.pdf

17:46 Measurement of flow harmonics, nonlinear flow response and symmetric cumulants in large and small systems with ALICE

Anisotropic flow is a key probe of the existence of the quark-gluon plasma. Small collision systems, such as proton-proton (pp) and proton-lead (p--Pb), are usually used to provide the reference data for collisions of heavy nuclei. However, inspection of high-multiplicity p--Pb and pp collisions revealed surprising features, usually attributed to collective effects in heavy-ion collisions.

In this poster, recent results on flow harmonics, nonlinear flow response and symmetric cumulants with the ALICE detector at the LHC will be presented. The observables characterize the properties of the strongly interacting matter. The properties include nonlinear response to initial geometry, event plane correlations and flow fluctuations. The observables are measured in both large systems (Pb--Pb, Xe--Xe) and small systems (p--Pb, pp) to show the asymptotic behavior of the flow-like effects from large to small systems.

Speaker: Mingrui Zhao (China Institute of Atomic Energy (CN))

poster.pdf

17:50 Collective evolution of a parton in the vacuum: search for the ultimate partonic “droplet”

We postulate that non-perturbative QCD evolution of a single parton in the vacuum will develop the long-range QCD collective effects of a multi-parton system, reminiscent of those observed in high-energy hadronic or nuclear interactions with large final-state particle multiplicity final-state particles [1]. Proton-Proton collisions at the Large Hadron Collider showed surprising signatures of a strongly interacting, thermalized quark-gluon plasma (QGP), which was thought only to form in collisions of large nuclear systems. Another puzzle observed earlier in electron-position collisions is that production yields of various hadron species appear to follow a thermal-like distribution with a common temperature. We propose searches for thermal and collective properties of a single parton propagating in (or “colliding into”) the vacuum using high multiplicity jets in high-energy elementary collisions, using a new frame with the jet direction defined as the beam z axis. In this single jet frame, a series of observables relevant to signatures of QGP are studied using the PYTHIA 8 Monte Carlo event generator in pp collisions at LHC energies. Experimental observation of collective and thermal effects in such single parton systems will offer a new view of non-perturbative QCD dynamics of multi-parton systems at the smallest scales. Absence of any collective effect may offer new insights into the role of quantum entanglement in the observed thermal behavior of particle production in high energy collisions. Opportunities for additional studies at future facilities, such as the EIC or a proposed muon-ion collider, future circular collider (FCC) are also discussed..

[1] https://arxiv.org/abs/2104.11735

Speakers: Austin Alan Baty (Rice University (US)), Wei Li (Rice University (US)), Parker Gardner (Rice University (US))

Rice_Gardner_QM22_Krakow.pdf

17:54 PHENIX results on collective flow in small systems

There is strong evidence for the formation of small droplets of quark-gluon plasma in $p/d/^{3}$He+Au collisions at the Relativistic Heavy Ion Collider (RHIC) and in $p$+$p$/Pb collisions at the Large Hadron Collider. In particular, the analysis of data at RHIC for different geometries obtained by varying the projectile size and shape has proven insightful. In this talk, we present a new analysis that confirms the previous results and extends the measurements of $v_2$ and $v_3$ towards larger pseudorapidity acceptances. The $v_2$ measurements are further extended to non-central collisions and minimum bias $p$+$p$ collisions.

Speaker: Takahito Todoroki (University of Tsukuba)

QM2022_poster_todoroki_v2.pdf

17:58 Study of the thermodynamical parameters using Tsallis statistics with flow velocity at freeze-out in relativistic heavy-ion collisions

The thermodynamical properties of the high-temperature and high-density system produced in relativistic heavy-ion collisions can be understood with a systematic study of the produced hadrons' transverse momentum ($p_{\rm T}$ ) spectra. The $p_{\rm T}$ spectra of these hadrons can be described well by a distribution using the Tsallis statistics. The Tsallis parameters $q$ and $T$ measure the degree of deviation of the system from an equilibrium state and the effective temperature at freeze-out conditions, respectively. The Tsallis formalism with the inclusion of flow velocity can describe the $p_{\rm T}$ spectra from low to high $p_{\rm T}$ ranges. This formalism overcomes the drawback of the limited pT range description through the blast-wave fits of the $p_{\rm T}$ spectra.

In this work, a detailed study of the $p_{\rm T}$ spectra of the identified charged particles (pions, kaons, protons) as well as all charged particles in the heavy-ion collisions at the Relativistic Heavy Ion Collider (RHIC) energies (from $\sqrt{s_{\rm NN}} = $ 7.7 GeV to 200 GeV) and at the Large Hadron Collider (LHC) energies ($\sqrt{s_{\rm NN}} =$ 2.76 TeV to 5.44 TeV) are performed using the non-extensive Tsallis statistics. The extracted Tsallis parameters are found to be dependent on the particle species, collision energy, centrality, and fitting ranges of the $p_{\rm T}$. With increases of the collision energies, $q$ increases in a systematic manner whereas $T$ has a decreasing trend. It is observed that the parameters $q, T$, changes with increasing $p_{\rm T}$ fitting ranges and at mid $p_{\rm T}$ region the parameter are found to be unchanged, which can describe the physics of the systems. The Tsallis parameters and the quality of fitting are found to follow a mass ordering. The contribution of the flow velocity of the particles are considered with the Tsallis statistics through Tsallis blast-wave (TBW) model, which is found to have a better description of the $p_{\rm T}$ spectra of different particle species. The thermodynamic parameters and extracted energy density at the kinetic freeze-out will be presented as a function of collision energy.

Speaker: Dr Rajendra Nath Patra (CERN)

18:02 Measurement of the transverse momentum($j_T$) distributions of charged-particle jet fragments in pp collisions at $\sqrt{s}$ = 5.02 TeV with ALICE

Jet fragmentation can be studied using the transverse momentum ($j_T$) and longitudinal momentum fraction ($z$) of constituent particles. The $j_T$ distributions of jet fragments have been measured in pp and p—Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV with ALICE, and various parton-shower models reasonably describe the pp results. In this analysis we carry out more detailed measurements of $j_T$ distributions for charged jets in pp collisions, in several z ranges. The $z$-dependent $j_T$ distributions will be compared with various models to test our current understanding of jet fragmentation and hadronisation. In this poster, the current status and future plans of the data analysis will be presented.

Speaker: Mr Jaehyeok Ryu (Pusan National University (KR))

Quarkmatter2022_poster_JaehyeokRyu_v1.mp4

Quarkmatter2022_poster_JaehyeokRyu_v2.pdf

18:06 Measurements of jet and soft activity in $\sqrt{s_{{\rm NN}}}=200$ GeV p+Au collisions at STAR

Proton-ion collisions at the LHC and RHIC have yielded unexpected trends, notably in measurements of jet nuclear modification factors at different collision centralities. Recent preliminary measurements from STAR in p+Au collisions at $\sqrt{s_{{\rm NN}}}=200$ GeV demonstrate inherent correlations between high-$Q^{2}$ parton scatterings and event activity (EA), measured using either detectors at backward (Au-going) rapidities or underlying event (UE) at mid-rapidity. The measurements at STAR disfavor jet quenching as an explanation for the suppression of jet yield observed in high-EA collisions. This leads to an opportunity to probe the early stages of the collisions and cold nuclear matter (CNM) effects. In this talk, we show correlations of backward-rapidity EA with mid-rapidity UE, as well as measurements of EA-dependent modifications to charged hadron spectra and jets. In particular, we present measurements of the UE for various EA selections and discuss its kinematic dependence on jet pseudorapidity and transverse momentum, $p_{{\rm T}}$, as a means of examining the initial hard scatterings. We also investigate the EA dependence of high-$p_{{\rm T}}$ hadron and jet properties -- including fully corrected ungroomed and SoftDrop groomed jet substructure observables as a function of EA -- to study the impact of initial and final state effects.

Speaker: Veronica Verkest (Wayne State University)

vverkest_QM2022_slides.pdf

18:10 Sub-nucleon geometry and multiparticle cumulants including $c_{2}\{4 \}$ in $p+p$ collisions

Collective flow-like signals including the ridge structure observed in small collision systems at high energies that are similar to those in large collision systems have led to questions about the onset of collectivity in nuclear collisions. Multiparticle cumulant methods are better in extracting the flow signals as they can suppress nonflow effects that are especially significant in small systems. For example, a negative four-particle cumulant $c_{2}\{4\}$ is expected when the correlation comes from the collective flow. A previous study from a hydrodynamics-based hybrid model could not produce negative $c_{2}\{4\}$ for $p+p$ collisions at 13 TeV [1], regardless of the analysis method such as the standard, two-subevent and three-subevent cumulants.

In this study [2], we use the string melting version of a multi-phase transport (AMPT) model without or with the sub-nucleon geometry for the proton to study multiparticle cumulants in $p+p$ collisions at 13 TeV. We have found that both versions of the model can produce $c_{2}\{4\}<0$ for high-multiplicity events. The relation between $c_{2}\{4 \}$ and the parton scattering cross section is non-monotonic, where only a finite range of parton cross sections can lead to negative $c_{2} \{4 \}$ for high-multiplicity $p+p$ events. In addition, the AMPT version with the proton sub-nucleon geometry describes the multiplicity dependence of $c_{2} \{4 \}$ much better than the version without. This demonstrates the importance of incorporating the sub-nucleon geometry and the potential of using multiparticle cumulants to probe the detailed sub-nucleon geometry in studies of small collision systems.

[1] W. B. Zhao, Y. Zhou, H. J. Xu, W. T. Deng and H. C. Song, Phys. Lett. B 780, 495-500 (2018).
[2] X. L. Zhao, Z. W. Lin, L. Zheng and G. L Ma, arXiv: 2112.01232.

Speaker: Xinli Zhao

QM2022-XinliZhao-poster.pdf

18:14 An Asymmetric Exact Solution for Longitudinally Expanding Ideal Fluid

Relativistic hydrodynamics has been successful in describing the evolution of Quark-Gluon Plasma, as well as understanding and predicting experimental measurements highlighting the collective behavior of the observed hadrons created in relativistic heavy-ion collisions. In parallel with the remarkable progress made in numerical fluid dynamics, the study of analytical solutions remains helpful in capturing intuitive pictures and important features.

In this work, we report a new exact and explicit analytical solution for relativistic ideal hydrodynamic equations. In this solution, the fluid expands in the longitudinal direction, and contains the plateau structure for finite rapidity range, and can be either symmetric or asymmetric (with respect to mid-rapidity). Both these features are controlled by two parameters in the solution, which allows flexibility in covering the longitudinal shape of p-A and A-A collisions. We further calculate the corresponding pseudorapidity distribution of hadron yields, and find good agreement with the experimental measurements in high-energy Pb-Pb, Au-Au, p-Pb, and d-Au collisions. We also stress the importance of exact solutions as a baseline for the assessment of non-equilibrium features, and for the validation of numerical simulations. Considering that this exact solution can be rapidity-asymmetric, this last point appears especially valuable.

Speaker: Dr Shuzhe SHI (Stony Brook University)

Exact Solution.key

Exact Solution.pdf

18:18 Measurement of low-momentum direct photons in Cu+Au collisions at 200 GeV

Direct photons are widely used probe to study the properties and evolution of the hot and dense medium (e.g. QGP) produced in high energy heavy-ion collisions. Being color neutral, they do not interact strongly with the medium and are produced at all stages of the collision.

A universal scaling of the direct photon yield with charged particle multiplicity has been observed for a wide range of collision systems at different center of mass energies (Au+Au at 200 GeV, 62.4 GeV, 39GeV, Cu+Cu at 200 GeV, d+Au at 200 GeV and p+Au at 200 GeV). The measurement also hints that the QGP turn off/on transition region may exist between large and small system collisions.

In this poster, the analysis status of the low transverse momentum direct photon production in Cu+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV using external conversion method with the PHENIX detector is presented. The present study will help bridge the gap between small and large systems, and hence will provide more information about the transition region.

Speaker: Mr Vassu Doomra (Stony Brook University)

Measurement of low-momentum direct photons in Cu+Au collisions at 200 GeV (1).pdf

18:22 Multiplicity dependent J/$\psi$ production at midrapidity in p-Pb collisions at 5 TeV with ALICE at the LHC

Previous ALICE results indicate a stronger than linear increase of the inclusive normalized J/$\psi$ yield with charged-particle multiplicity, both measured at mid-rapidity, in proton-lead collisions at $\sqrt{s_{NN}}=5.02$ TeV. The corresponding ALICE results on proton-proton collisions at$\sqrt{s}=13$ TeV provide a clearer picture of a stronger than linear increase.
In PYTHIA8, this behavior has been associated with auto-correlation effects in proton-proton collisions. This has been achieved by investigating the multiplicity dependence of J/$\psi$ production in different regions of the azimuthal angle, which is the difference between the J/$\psi$ meson and the charged particle emission angle. For proton-lead collisions, no results on these distributions for the J/$\psi$ meson are available yet.
This poster will present first results on the multiplicity dependence of the normalized J/$\psi$ yield for proton-lead collision in regions of the azimuthal angle, using ALICE data at $\sqrt{s_{NN}}=5.02$ TeV recorded during the LHC data taking Run 2 in 2016.

Speaker: Tabea Maria Eder (Westfaelische Wilhelms-Universitaet Muenster (DE))

PosterQM_JpsiMultpPb5TeV.pdf

17:30 → 18:30 Poster Session 1 T06 / T07

17:30 A lattice-based equation of state to study QCD matter at the Beam Energy Scan II.

With current and future heavy-ion experiments focusing on understanding the baryon-rich QCD (Quantum Chromodynamic) matter produced at low collisional energies, first-principle knowledge of the equation of state in such regions is essential for analyzing experimental data in terms of transport simulations and to constrain effective models of QCD.

We construct a novel equation of state (EoS) describing QCD matter at finite temperature $T$ and baryon $B$, electric $Q$ and strangeness $S$ chemical potentials by utilizing the alternate expansion scheme from recent lattice QCD results [1]. This procedure allows to reliably estimate the baryon and strangeness densities at larger values of the baryon chemical potential $\mu_B$ compared to the usual Taylor expansion in terms of susceptibilities. We use the latter only to incorporate the $\mu_Q$ and $\mu_S$ dependence into thermodynamic quantities, which is sufficient for studying the matter as produced in relativistic heavy-ion collisions. Our simple parametrization provides reliable results for all temperatures since it interpolates between the confined phase at low $T$ described by the Hadron-Resonance Gas (HRG) model, lattice QCD results around and above the transition temperature $T_c(\mu_B)$, and $\mathcal{O}(g^5)$ perturbative QCD results in the high-$T$ regime.

[1] S. Borsányi, Z. Fodor, J.N. Guenther, R. Kara, S.D. Katz, P. Parotto, A. Pásztor, C. Ratti, K.K. Szabó. Lattice QCD equation of state at finite chemical potential from an alternative expansion scheme. Phys.Rev.Lett. 126 (2021) 23, 232001.

Speaker: Dr Pierre Moreau (Duke University)

17:34 Heavy quark-antiquark interaction in finite temperature lattice QCD

Heavy quarkonia are important probes of the matter created in heavy ion-collisions. The complex
heavy-quark potential is an essential ingredient of dynamical models of quarkonium production in
heavy-ion collisions, e.g. in models based on open quantum system approach.
We calculate the complex heavy-quark potential in (2+1)-flavor QCD with physical quark masses on
the lattice using large temporal extent. The heavy-quark potential is extracted from the Wilson
line correlators in Coulomb gauge. Then we extract the underlying spectral functions using multiple
conceptually different analysis methods -- spectral function fits, an HTL inspired fit for the
correlation function, Padé rational approximation and the Bayesian BR spectral reconstruction and
compare the implications of each for the existence and properties of a well defined dominant
spectral peak.
The peak position corresponds to the real part of the potential, while the width corresponds to
the imaginary part of the potential. While all the methods roboustly point toward a significant
imaginary part of the potential that increases with increasing separation between quark and
antiquark, the expected screening of the real part of the potential is not evident in our
calculations.

References:

[1] D. Bala et al, e-Print: 2110.11659 [hep-lat], submitted to PRD
[2] D. Hoying et al, Contribution to: Lattice 2021, e-Print: 2110.00565 [hep-lat]

Speaker: Dr Johannes Heinrich Weber (Humboldt University of Berlin)

qm2022_hqi_poster.pdf

qm2022-weber.pdf

17:38 Do fluctuations of conserved charges evidence a deconfinement?

Above the chiral restoration crossover some cumulants
of quark (baryon) number and charge fluctuations approach
a free quark gas value already at T ~ 200-250 MeV and
are considered sometimes as evidence of deconfinement.
At the same time at these temperatures very clear patterns
of chiral spin symmetry, which is a symmetry of the color
charge and electric interactions, and which is not a symmetry
of free quark gas, are observed. This symmetry suggests that
degrees of freedom are chirally symmetric quarks connected
by electric field into color singlet objects ("long strings").

The cumulants of conserved charge fluctuations are given
by integrals of spatial correlators of conserved charge.
If quarks are free these correlators demonstrate on a
finite lattice remarkable diffractive patterns that are
induced by quarks that are separated by a large distance.
In full QCD these diffractive patterns are absent which
indicates that a confining interaction does not allow
quarks to be separated by a large distance. These effects
are clearly visible in the correlators in a region where
the correlators are suppressed by a few orders of magnitude.
Hence the cumulants of conserved charge fluctuations are
simply insensitive to the deep infrared region where
confinement is manifest.

Speaker: Leonid Glozman

17:42 Bose-Einstein correlations of charged kaons produced by $\sqrt{s_{_{NN}}}=200$ GeV Au+Au collisions in STAR at RHIC

Bulk properties of nuclear matter can be extracted by employing femtoscopic methods to study the high-energy systems emerging from relativistic heavy-ion collisions. The space-time structure of the particle-emitting source can be examined by observing the effects of quantum-statistics and final-state-interactions on the pair correlations of particles, with data collected by the STAR experiment from $\sqrt{s_{_{NN}}}=200$ GeV Au+Au collisions created at RHIC. On account of being less susceptible to resonance decays and having a smaller reaction-cross-section while interacting with hadrons, kaons provide a complementary probe of the particle-emitter as compared to pion analyses. Results from Bose-Einstein correlations between pairs of charged kaons will be presented in this study and compared to descriptions based on a Levy-shaped source distribution.

Speaker: Ayon Mukherjee

Charged_Kaons_Poster_v2_suppl.pdf

17:46 Machine learning with gauge symmetry

The breakthroughs in computer vision and image recognition of the past decade using convolutional neural networks (CNNs) have shown that adapting neural network architectures to the symmetries associated with a particular machine learning problem leads to models that perform better and are easier to train and to interpret. These successes have led to applications in lattice gauge theory, such as detecting phase transitions or improving the performance of Monte Carlo methods. In this talk we present lattice gauge equivariant convolutional neural networks (L-CNNs) [1], a general framework for formulating neural networks that are equivariant under lattice gauge symmetry, and demonstrate that L-CNNs can outperform non-equivariant CNNs in non-linear regression tasks. Moreover, we prove that L-CNNs are able to generate arbitrarily shaped Wilson loops from just a few gauge equivariant network layers.

[1] M. Favoni, A. Ipp, D. I. Müller, D. Schuh, arXiv:2012.12901

Speaker: Matteo Favoni (TU Wien)

LCNN_presentation.pdf

17:50 Lattice simulations of the QCD chiral transition at real baryon density

State-of-the-art lattice QCD studies of hot and dense strongly interacting matter currently rely on extrapolation from zero or imaginary chemical potentials. The ill-posedness of numerical analytic continuation puts severe limitations on the reliability of such methods. Here we use the more direct sign reweighting method to perform lattice QCD simulation of the QCD chiral transition at finite real baryon density on phenomenologically relevant lattices. This method does not require analytic continuation and avoids the overlap problem associated with generic reweighting schemes, so has only statistical but no uncontrolled systematic uncertainties for a fixed lattice setup. This opens up a new window to study hot and dense strongly interacting matter from first principles. We demonstrate that the method can penetrate the region where extrapolation methods stop being predictive, by performing simulations up to a baryochemical potential-temperature ratio of $\mu_B/T=2.7$ - thus covering the range of the RHIC Beam Energy Scan in the baryochemical potential.

Speaker: Attila Pasztor (Eötvös University)

QM22_5slides.pdf

QM22_poster.pdf

17:54 Measurement of direct photon anisotropy at PHENIX

Direct photons are an important probe into the thermal and collective properties of Quark Gluon Plasma (QGP). Precise measurement of the direct photon anisotropy is necessary to provide additional insight into the photon production mechanisms in QGP which helps constrain theoretical models and thus solve the so-called direct photon puzzle. In this poster, analysis status of the elliptic and triangular flow is presented from the high statistics Au+Au data taken in 2014 by the PHENIX experiment. Two different event plane detectors are used to take into account possible non-flow effects in the data.

Speaker: Michael Giles

QM 2022 Poster Session-Giles.pdf

17:58 Lattice QCD with an inhomogeneous magnetic field background

The magnetic fields generated in non-central heavy-ion collisions are among the strongest fields produced in the Universe, reaching magnitudes comparable to the scale of the strong interactions. Backed by model simulations, the resulting field is expected to be spatially modulated, deviating significantly from the commonly considered uniform profile. In this work, we present the next step to improve our understanding of the physics of quarks and gluons under extreme conditions by using lattice QCD simulations with $2+1$ staggered fermions with physical quark masses and an inhomogeneous magnetic background for a range of temperatures covering the QCD phase transition. We apply a field with strength given by a $1/\cosh^2$ function and analyze the impact on the computed observables and on the transition. We study the physics of the QCD medium by calculating local chiral condensates, Polyakov loops, electric currents and perform the continuum limit extrapolation. We find that the observables show non-trivial spatial features due to the interplay between the sea and the valence effects, especially around the critical temperature.

Speaker: Adeilton Dean Marques Valois (Bielefeld University)

QM2022_deanvalois.pdf

18:02 Corrections to the hadron resonance gas from lattice QCD and their effect on fluctuation-ratios at finite density

The hadron resonance gas (HRG) model is often believed to correctly describe the confined phase of QCD. This assumption is the basis of many phenomenological works on QCD thermodynamics and of the analysis of hadron yields in relativistic heavy ion collisions. We use first principle lattice simulations to calculate corrections to the ideal HRG model. Namely, we determine the subleading fugacity expansion coefficients of the grand canonical free energy, receiving contributions from processes like kaon-kaon or baryon-baryon scattering. We achieve this goal by performing a two dimensional scan on the imaginary baryon number chemical potential (μB)—strangeness chemical potential (μS) plane, where the fugacity expansion coefficients become Fourier coefficients. We carry out a continuum limit estimation of these coefficients by performing lattice simulations with temporal extents of
Nτ=8, 10, 12 using the 4stout-improved staggered action. We then use the truncated fugacity expansion to extrapolate ratios of baryon number and strangeness fluctuations and correlations to finite chemical potentials. Evaluating the fugacity expansion along the crossover line, we reproduce the trend seen in the experimental data on net-proton fluctuations by the STAR collaboration.

Speaker: Paolo Parotto

QM2022.pdf

18:06 Search for higher mass resonances via KK decay channel in pp collisions with ALICE at the LHC

The quark model has proven successful in describing the basic building blocks of strongly interacting particles in the Standard Model, where hadronic states consist of quarks and gluons. At the same time, Lattice QCD predicts the possibility of glueball candidates in the mass range 1550-1750 MeV/$c^{2}$, which have never been observed.
The experimental search for the existence of mesons with no quark content is both interesting and challenging as the glueball is very likely to mix with surrounding quark-antiquark scalar meson states with the same quantum numbers.
The large statistics data sample collected by ALICE in pp collisions at the highest LHC center of mass energy provides an opportunity to measure high mass resonances, whose characteristics and internal structure are still unknown. Measurements help us understanding the nature of particles as well as their formation mechanism.

We report on the measurements of invariant mass distributions of K$^{0}_\mathrm{S}$K$^{0}_\mathrm{S}$ and K$^{+}$K$^{-}$ pairs in pp collisions at $\sqrt{s}$ = 13 TeV using the ALICE detector at central rapidity. We will discuss the structure of the invariant mass distributions and perspectives for the search of glueball states.

Speaker: Dukhishyam Mallick (National Institute of Science Education and Research (NISER) (IN))

Searchforglueball_KKchannel_QM2022_Dukhishyam.pdf

18:10 Effects of hydrodynamic fluctuations in ultra-central Pb-Pb collisions at LHC

In ultra-central heavy-ion collisions, the effects of event-by-event fluctuations on anisotropic flow are relatively more pronounced due to less geometrical anisotropy of initial transverse profiles. The magnitudes of elliptic flow $v_2$ and triangular flow $v_3$ were reported to be almost the same value in ultra-central collisions [1]. Dynamical models based on relativistic viscous hydrodynamics describe anisotropic flow in non-central collisions well, however, failed to reproduce these $v_2$ and $v_3$ data in ultra-central collisions simultaneously [2,3]. Since the hydrodynamic description is supposed to be better in larger systems, the failure of the viscous hydrodynamic models in ultra-central collisions implies the existence of overlooked phenomena. This problem is known as "ultra-central puzzle" and has not been resolved yet.

In this talk, we investigate the effects of hydrodynamic fluctuations on anisotropic flow in ultra-central collisions. We employ an integrated dynamical model [4] with relativistic fluctuating hydrodynamics [5,6] to describe the dynamics of heavy-ion collisions at the LHC energy and compare the results among ideal, viscous, and fluctuating hydrodynamics. In this framework, hydrodynamic fluctuations are introduced through the fluctuation-dissipation relation [5]. Since the anisotropic flow is driven mainly by fluctuations in ultra-central collisions, hydrodynamic fluctuations are expected to play an important role in understanding anisotropic flow.

First, we employ smooth and azimuthally symmetric initial conditions at impact parameter $b=0$ fm from the optical Glauber model to investigate the effects of genuine hydrodynamic fluctuations on anisotropic flow coefficients. We show that $v_2$ and $v_3$ caused by hydrodynamic fluctuations alone are almost the same value which is, however, almost half of the experimental flow coefficients. Second, we introduce a weight function of impact parameters to simulate ultra-central collisions efficiently and compare the results from Monte-Carlo Glauber initial conditions with hydrodynamic fluctuations to experimental data. Even with hydrodynamic fluctuations, we cannot reproduce $v_2$ and $v_3$ quantitatively at the same time. Nevertheless, we find the $v_2/v_3$ ratio becomes closer to the experimental data due to hydrodynamic fluctuations.

[1] S. Chatrchyan et al., (CMS Collaboration), JHEP 02, 088 (2014).
[2] C. Shen, Z. Qiu, and U. Heinz, Phys. Rev. C 92, 014901 (2015).
[3] P. Carzon, S. Rao, M. Luzum, M. Sievert, and J. Noronha-Hostler, Phys. Rev. C 102, 054905 (2020).
[4] T. Hirano, P. Huovinen, K. Murase, and Y. Nara, Prog. Part. Nucl. Phys. 70, 108 (2013).
[5] K. Murase, Ph. D thesis, The University of Tokyo (2015).
[6] K. Murase and T. Hirano, Nucl. Phys. A 956, 276 (2016).

Speaker: Kenshi Kuroki (Sophia University)

poster_kuroki_QM2022.pdf

18:14 Exploring the chirality and criticality of QCD matter with effective field theory for fluctuating hydrodynamics

Very recently, a non-equilibrium effective field theory framework has been formulated for fluctuating hydrodynamics [1]. In this talk, we present examples of applying this novel formalism to study the properties of QCD-like systems. In the first example, we study the dependence of the conductivity/resistivity on the external magnetic field in a chiral medium (the constituent of which includes chiral fermions). While it is widely believed that chiral magnetic effect (CME) would lead to a negative magneto-resistivity, we find that CME together with hydrodynamic fluctuations gives rise to a positive magneto-resistance [2]. Second, in the view that non-Gaussian fluctuations of baryon density are important for the QCD critical point search, we derive evolution equations for the critical non-Gaussian fluctuations of a conserved density and obtain closed-form solutions based on field theory techniques [3]. Those results can be readily implemented for simulations in realistic situations of heavy-ion collisions. In addition, we find that nonlinear interactions among noise fields, which are missing in traditional stochastic hydrodynamics, could potentially contribute to the quartic (fourth-order) fluctuations in the scaling regime in off-equilibrium situations.

[1] Michael Crossley, Paolo Glorioso and Hong Liu, “Effective field theory of dissipative fluids,” JHEP 09 (2017) 095.

[2] Noriyuki Sogabe, Naoki Yamamoto and Yi Yin, “Positive magnetoresistance induced by hydrodynamic fluctuations in chiral media,” JHEP 09 (2021) 131.

[3] Noriyuki Sogabe and Yi Yin, “Off-equilibrium non-Gaussian fluctuations near the QCD critical point: an effective field theory perspective,” [arXiv:2111.14667 [nucl-th]].

Speaker: Noriyuki Sogabe (Institute of Modern Physics, Chinese Academy of Sciences)

QM2022_short.pdf

18:18 Statistical description of the initial state and validity of mode-by-mode dynamics

We develop a general decomposition of an ensemble of initial density profiles in terms of an average state and an orthonormal basis of modes that represent the event-by-event fluctuations of the initial state. The basis is determined such that the probability distributions of the amplitudes of different modes are uncorrelated. Based on this decomposition, we quantify the different types and probabilities of event-by-event fluctuations in Glauber and Saturation models and investigate how the various modes affect different characteristics of the initial state. We perform simulations of the dynamical evolution with KøMPøST and MUSIC to investigate the impact of the various modes on final-state observables and their correlations. By comparing results for the mode-by-mode linear response of $v_n$ and $\langle p_t\rangle$ with event-by-event simulations, we further quantify the accuracy of mode-by-mode approaches.

Speaker: Hendrik Roch (Bielefeld University)

QM22_Stat_description_IS.pdf

18:22 Investigating the two-particle source function in heavy-ion collisions with EPOS

Exploring the shape of the pair-source function for particles such as pions or kaons has been an important goal of heavy-ion physics, and substantial effort has been made in order to understand the underlying physics behind the experimental observations of non-Gaussian behavior. In experiments, since no direct measurement is possible, femtoscopic (momentum) correlations are utilized to gain information about the space-time geometry of the particle emitting source. Event generators such as the EPOS model, however, provide direct access to the freeze-out coordinates of particles, and thus the source function can be constructed and investigated. The EPOS model has already proven to be successful in describing many different experimental observations for systems characterized by baryon chemical potential close to zero, but so far the source shape has not been explored in detail. On this poster an event-by-event analysis will be presented, focusing on the two-particle source function measured in $\sqrt{s_{NN}}$ = 200 GeV Au+Au collisions generated by the EPOS model. The emergence of the non-Gaussian behavior at different phases of the model as well as a detailed centrality and average transverse momentum dependence of the extracted source parameters will be discussed.

Speaker: Dániel Kincses (Eötvös Loránd University)

kincsesd_QM2022_poster.pdf

17:30 → 18:30 Poster Session 1 T07_1

17:30 Fluctuations in Lambda Multiplicity Distribution in Au+Au Collisions at $\sqrt{s_{NN}} = 3.0$ GeV at STAR

The study of nuclear matter over a wide range of collision energy is provided by the RHIC Beam Energy Scan (BES). One focus of the program, namely to locate the critical point (CP) in the QCD phase diagram, is closely tied to the measurement of kurtosis in net-proton multiplicity distribution as a function of $\sqrt{s_{NN}}$.
Previous results from BES-I obtained with $3.1 \sigma$ significance motivated us to increase the statistics and to extend the collision energy down to $\sqrt{s_{NN}} = 3.0$ GeV in the BES-II. The event-by-event fluctuations in net-lambda multiplicity distribution for the first BES showed that the cumulant ratios have a similar energy and multiplicity dependence compared to those for protons, and the observed deviation from Poisson baseline can be attributed to baryon number and strangeness conservations. It is also known from the previous work that the derived freeze-out parameters show sensitivity to the quark content of the hadrons, implying a quark mass dependence in the process of hadronization. We present in this poster, the lambda fluctuation analysis in Au+Au collisions at the lowest center of mass energy ($\sqrt{s_{NN}}= 3.0$ GeV), where we continue the comparison with proton fluctuations and analyze the behaviour of both baryons, specifically in terms of their difference in quark content and applicable conservation laws.

Speaker: Jonathan Gonzalo Ball Cap (University of Houston)

QM_Poster_Lambda_Fluctuations_3GeV.pdf

17:34 Dynamics of particle emission probed by femtoscopic correlations in the STAR experiment

One of methods to study the properties of hot and dense nuclear matter created in high-energy nuclear collisions is femtoscopic measurements. This method provides information about space-time characteristics of the particle emission region, which has a size and lifetime of the order of $10^{-15}$ m and $10^{-23}$ s, respectively. From non-identical particle correlations, one can obtain information about asymmetry in the emission process between those two kinds of particles. Such an emission asymmetry gives knowledge of which type of particles, on average, are emitted earlier and from which region of the source. Using different combinations of pion, kaon, and proton pairs, one can obtain complete knowledge on geometric and dynamic (times of emission) properties of the particle emitting source. Such investigation could provide information about differences between the emission of light mesons (pions), strange mesons (kaons), and baryons (protons).

In this poster, the STAR results on femtoscopic observables of various particle combinations of pions, kaons, and protons from Au+Au collisions at Beam Energy Scan program will be presented.

Speaker: Mr Paweł Szymański

QM2022_poster_PSzymanski.pdf

17:38 Impact of hadronic interactions and conservation laws on cumulants of conserved charges in a dynamical model

Understanding the phase diagram of QCD by measuring fluctuations of conserved charges in heavy-ion collision is one of the main goals of the beam energy scan program at RHIC. For a precise measurement of the cumulants it is necessary to grasp the role of charge conservation in heavy-ion collision measurements. Within this work, we calculate the role of hadronic interactions and momentum cuts on cumulants of conserved charges up to fourth order in a system in equilibrium within a hadronic transport approach (SMASH). In our model the net-baryon, net-charge and net-strangeness is perfectly conserved on an event-by-event basis and the cumulants are calculated as a function of subvolume sizes and compared to analytic expectations. This reflects the experimental situation in which e.g. the net-baryon number is conserved in a heavy-ion collision and the results depend on the rapidity window. We find a modification of the kurtosis due to charge annihilation processes in systems with simplified degrees of freedom. Furthermore the result of the full SMASH hadron gas for the net-baryon and net-proton number fluctuations is presented for systems with zero and finite values of baryochemical potential. Additionally the problem of mapping between the net-proton and net-baryon fluctuations is addressed and we find that due to dynamical correlations the cumulants of the net-baryon number cannot be recovered from the net-protons. Finally the influence of deuteron cluster formation on the net-proton and net-baryon fluctuations in simplified system is shown. This analysis is important to better understand the relation between measurements of fluctuations in heavy-ion collisions and theoretical calculation which are often performed in a grand canonical ensemble.

Speaker: Jan Hammelmann (Frankfurt Institute for Advanced Studies (FIAS))

QM2022_Hammelmann.pdf

17:42 Seventh and eighth order cumulants of net-proton number distributions in heavy-ion collisions at STAR-RHIC

Higher-order cumulants of net-proton distributions are sensitive to the details of the phase structure of the QCD phase diagram. Lattice QCD and QCD-based model calculations indicate that the signs of sixth and eighth-order cumulants have different combinations in the hadronic phase, partonic phase, and near the transition temperature.

In this poster, we report the first measurements of seventh and eighth-order cumulants of net-proton distributions in the high statistics Au+Au collisions at $\sqrt{s_{NN}}$ = 27, 54.4, and 200 GeV. The measurements are done at mid-rapidity $|y|<0.5$ within 0.4 $< p_{T} < 2.0$ GeV/$c$ using the Time Projection Chamber and Time-of-Flight detector. The measurements in Au+Au collisions at 200 GeV will be compared to those from Zr+Zr and Ru+Ru collisions to understand the system size dependence. The signs of the measured sixth, seventh, and eighth order cumulants will be contrasted to those expected from the lattice QCD and QCD-based models. The ratios of the measured cumulants will also be compared with those obtained from the transport and thermal models to understand the role of baryon number conservation and the validity of models.

Speaker: Mr Ashish Pandav (NISER, India)

QM2022_poster_STAR_PA_e3.pdf

17:46 Centrality dependent Lévy HBT analysis in $\sqrt{s_{_{\mathrm{NN}}}} =$ 5.02 TeV PbPb collision at CMS

Investigation of the femtoscopic correlation functions in heavy ion collisions is an important tool to access the space-time structure of the hadron production of the sQGP. The description of the measured correlation functions is often assumed to be Gaussian or exponential, but a detailed analysis reveals that the statistically correct assumption is a generalized Gaussian, the symmetric alpha-stable Lévy distribution. One of the resulting source parameters, the Lévy stability parameter $\alpha$, describing the shape of the source, may be related to anomalous diffusion in the final state. In this poster we present measurements of two-particle, Bose-Einstein correlation functions in $\sqrt{s_{_{\mathrm{NN}}}} =$ 5.02 TeV PbPb collisions at CMS. We investigate the centrality and transverse mass dependence of the parameters of the correlation functions: the strength or the intercept parameter $\lambda$, the HBT scale parameter $R$ and the stability parameter $\alpha$.

Speaker: Balazs Korodi (Eotvos Lorand University (HU))

QM_poster_LevyHBT_balazskorodi.pdf

17:50 Predictions of Kaon femtoscopy in Pb-Pb collisions at 5.02 TeV

In this talk, I will review the basics of 3+1d quasiparticle anisotropic hydrodynamics (aHydroQP) and highlight some phenomenological comparisons with experimental data at different energies. Then, I will present comparisons of the kaon femtoscopic HBT radii using aHydroQP at 200 GeV where our model shows very good agreement with the experimental data.
Next, I will show predictions of the kaon’s HBT radii and their ratios at 5.02 TeV.

Speaker: Mubarak Alqahtani (Imam Abdulrahman Bin Faisal University)

poster.pdf

17:54 Quantum statistical fluctuation of energy and baryon number in subsystems of hot and dense relativistic gas

We discuss the quantum fluctuations of energy in subsystems of hot relativistic gas for both scalar and spin half particles. For small subsystem sizes, we find a substantial increase of fluctuations compared to those known from standard thermodynamic considerations. However, if the size of the subsystem is sufficiently large, we reproduce the result for energy fluctuations in the canonical ensemble. Interestingly for spin half particles, the results for quantum fluctuation depend on the form of the energy-momentum tensor used in the calculations, which is a feature described as pseudo-gauge dependence. However, for sufficiently large subsystems the results obtained in different pseudo-gauges converge and agree with the canonical-ensemble formula known from statistical physics. Although different forms of the energy-momentum tensor of gas are a priori equivalent, our finding suggests that the concept of quantum fluctuations of energy in very small thermodynamic systems is pseudo-gauge dependent. On a practical side, our results can be used in the context of relativistic heavy-ion collisions to introduce limitations of the concepts such as classical energy density or fluid element. Also, the results of our calculations determine a scale of coarse-graining for which the choice of the pseudo-gauge becomes irrelevant. In a straightforward way, our formula for quantum fluctuation can be applied in other fields of physics, wherever one deals with the hot and relativistic matter.

Further using the formalism developed to obtain the fluctuation of energy we also estimated the quantum features of the baryon number fluctuations in subsystems of a hot and dense relativistic gas of fermions. Our results for the baryon number fluctuation also suggest that for small system size quantum mechanical effects can be significant. Such a system size dependence of quantum statistical fluctuation can be helpful to shed new light on the experimental data, particularly for a small system probed in the heavy-ion collision experiments.

Speaker: ARPAN DAS (Institute of Nuclear Physics Polish Academy of Sciences Krakow, Poland)

Quark_Matter_Poster_2.pdf

17:58 Femtoscopy in small colliding systems at CMS

Femtoscopic correlations are measured over a broad multiplicity range using data from the LHC Run II collected by the CMS experiment for small colliding systems. Studies are performed for correlations of charged hadrons produced in proton-proton (pp) collisions at $\sqrt{s} = $ 13 TeV and for correlations with all pair combinations of $\text{K}^{0}_{\text{S}}$, $\Lambda$ and $\overline{\Lambda}$ in proton-lead (pPb) collisions at $\sqrt{s_{_{\mathrm{NN}}}} =$ 8.16 TeV. Results from pp collisions are compared to data from lower energies and from the ATLAS experiment, as well as with theoretical expectations from the color glass condensate and hydrodynamical models. In addition, identified particles are employed to perform the first femtoscopic correlation measurements of $\text{K}^{0}_{\text{S}}\text{K}^{0}_{\text{S}}$ and of $\Lambda~\!\overline{\Lambda}$ and $\text{K}^{0}_{\text{S}}\Lambda\oplus\text{K}^{0}_{\text{S}}\overline{\Lambda}$ correlations in pPb colliding systems. In these cases, the shape of the correlation function varies considerably for the different particle pairs, unveiling the effect of the strong final state interaction in each case. Intriguingly, the invariant radii and the correlation intensity results for $\text{K}^{0}_{\text{S}}\text{K}^{0}_{\text{S}}$ in pPb collisions share similarities with those from charged hadrons in pp collisions. On the other hand, the scattering parameters obtained for baryon-baryon and baryon-antibaryon strong interactions in pPb collisions behave as found in previous results for larger colliding systems.

Speaker: Sandra Padula (UNESP - Universidade Estadual Paulista (BR))

Femtoscopy_CMS-SandraSPadula.pdf

18:02 Higher-order event-by-event mean-$p_\mathrm{T}$ fluctuations in pp and A--A collisions with ALICE

The study of correlation and fluctuation of event-by-event mean transverse momentum ($p_\mathrm{T}$) is a useful tool to understand the dynamics of the system produced in ultrarelativistic heavy-ion collisions. The measurement of higher-order fluctuations of mean-$p_\mathrm{T}$ can help in probing the hydrodynamic behavior of the system and is considered to be a direct way of observing initial-state fluctuations. It can also be sensitive to the early-time evolution of the produced quark-gluon plasma.

We present the first measurement of three- and four-particle $p_\mathrm{T}$ correlators and their intensive ratios, related to the skewness and kurtosis of event-by-event mean-$p_\mathrm{T}$ distribution, as a function of average charged-particle density in Pb--Pb collisions at $\sqrt{s_\mathrm{NN}}$ = 5.02 TeV and Xe--Xe collisions at $\sqrt{s_\mathrm{NN}}$ = 5.44 TeV using the data recorded by the ALICE detector. For the baseline study, the analysis is performed also in pp collisions at $\sqrt{s}$ = 5.02 TeV. The measurements are compared to corresponding results from the STAR experiment at lower collision energies and to different theoretical model predictions.

Speaker: Ms Swati Saha (National Institute of Science Education and Research (NISER) (IN))

QM2022_poster_SwatiSaha_ALICE_final.pdf

18:06 Constraining interactions beyond the ideal HRG model via susceptibilities of conserved charges

We investigate extensions of the Hadron Resonance Gas (HRG) Model beyond the ideal case by implementing both attractive and repulsive additions to the model [1]. When considering additional states exceeding those measured with high confidence by the Particle Data Group, attractive corrections to the overall pressure in the HRG model are imposed. On the other hand, we also apply excluded-volume corrections, which ensure there is no overlap of baryons by turning on repulsive (anti)baryon-(anti)baryon interactions. We see that these two extensions are complementary and focus on the agreement with first-principles lattice QCD results on fluctuations of conserved charges. We note that these results are interesting for heavy-ion-collision systems at both the LHC and RHIC. In particular, we find interesting ratios of susceptibilities that are sensitive to one correction and not the other. This allows us to constrain the excluded volume and particle spectrum effects separately. Additionally, we see that strangeness susceptibilities indicate a smaller excluded volume for hyperons than non-strange baryons.

1. J. M. Karthein, V. Koch, C. Ratti, V. Vovchenko, Phys. Rev. D, 104, 094009 (2021)

Speaker: Dr Jamie Karthein (MIT)

JMKarthein_QM_2022.pdf

18:10 Stochastic Hydrodynamics Meets Hydro-kinetics

Hydrokinetic formalism is a deterministic set of relaxation type equations that tracks the evolution of n-point correlation functions of stochastic hydrodynamic quantities. Hydrokinetic formalism is a complementary approach to solving the Stochastic Differential Equations (SDE) for fluctuating hydrodynamics. Hydrokinetics is comparatively easier to solve than the SDEs, which need to deal with arbitrarily large gradients. This talk systematically compares the two approaches for the propagation and diffusion of conserved charge fluctuations in the 1D Bjorken hydrodynamic model. We solve the causal Catteneo noise in the SDE approach [1] and quantify the causality constraints on the evolution of the two-point correlation of charge fluctuations. Results are compared with those from Hydrokinetics in the white-noise limit as a function of wavelength. We further explore the consequence of colored noises on the two-point correlation of charge fluctuations. By subtracting the self-correlation term, we obtain a characteristic power-law decay of the two-point correlator as a function of the time, which agrees with the hydrokinetic approach.

[1] A. De, C. Plumberg and J. I. Kapusta, "Calculating Fluctuations and Self-Correlations Numerically for Causal Charge Diffusion in Relativistic Heavy-Ion Collisions'', Phys. Rev. C102, 024905 (2020)

Speaker: Aritra De (University of Minnesota, Twin-cities)

qm2022_aritra.pdf

18:14 New advancements in symmetry plane correlations and multiharmonic fluctuations in heavy-ion collisions with ALICE

The study of collective phenomena in ultrarelativistic heavy-ion collisions is nowadays to a great extent built on the so-called flow amplitudes $v_n$ and symmetry planes $\Psi_n$. Both appear as two distinct degrees of freedom in the parametrization of the azimuthal distribution of the produced particles, which is used in the study of the quark-gluon plasma (QGP). Investigating the complex interplay of these quantities allows one to further constrain our current knowledge of this exotic state of matter. While analyses techniques for flow amplitudes $v_n$ have advanced over the past years, observables used for measuring symmetry planes $\Psi_n$ are often plagued by built-in biases. The most important of them arises from the neglect of the correlations between different flow amplitudes, which were shown by the ALICE Collaboration to exist even between three amplitudes. Recent developments for the measurement of symmetry plane correlations (SPC) take these correlations into account and provide a new and more precise analysis technique $-$ the so-called Gaussian Estimator (GE). In this talk, we highlight the new results for higher-order multiharmonic flow fluctuations obtained with ALICE in heavy-ion collisions. These results show the presence of complex correlations between multiple flow amplitudes of different order, and also emphasise their importance in the measurement of SPC. Taking this into account, the first experimental results of SPC measured with the newly developed GE using Pb-Pb collisions data are presented. All results are compared to theoretical predictions for the initial coordinate space provided by the T$_{\rm R}$ENTo model and for the momentum space obtained with the state-of-the-art model iEBE-VISHNU.

Speakers: Cindy Mordasini (University of Jyväskylä (FI)), Marcel Markus Lesch (Technische Universitaet Muenchen (DE))

QM22_Poster_SPC_AC_Lesch_Mordasini_ALICE.pdf

18:18 Local multiplicity fluctuations in Pb$-$Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 2.76 TeV with ALICE at LHC

In this contribution, we present a first factorial moment analysis performed on the multiplicity distributions of charged particles produced in the Pb$-$Pb collisions at $\sqrt{s_{\rm{NN}}}$=2.76 TeV, recorded with the ALICE detector at the LHC. The normalized factorial moments (NFM) of spatial configurations of charged particles in two-dimensional angular ($\eta,\varphi$) phase space, $F_{q}$ for $q\ge2$, are calculated. For a system with dynamical fluctuations due to characteristic critical behaviour near the phase transition, $F_{q}$ exhibits power-law growth with increasing bin number or decreasing bin size which indicates self-similar fluctuations. Relating the $q^{\rm{th}}$ order NFM ($F_{q}$) to the second order NFM ($F_{2}$), the value of the scaling exponent ($\nu$) is extracted, which indicates the order of the phase transition within the framework of Ginzburg-Landau theory.

Speaker: Sheetal Sharma (University of Jammu (IN))

QM2022_IntermittencyAtLHCposterF11.pdf

18:22 Combinants and correlation functions in nuclear collisions

Multiplicity distributions in e+e- and pp collisions analysed via combinants exhibit oscillatory behavior of the modified combinants. The possible sources of these oscillations and their impact on our understanding of the multiparticle production mechanism were discussed [1-3]. The set of combinants, Cj provides a similar measure of fluctuations as the set of cumulant factorial moments, Kq, which are very sensitive to the details of the multiplicity distribution and were frequently used in phenomenological analyses of data. However, while cumulants are best suited to the study of the densely populated region of phase space, combinants are better suited for the study of sparsely populated regions because calculation of Cj requires only a finite number of probabilities P(N <j).
In this presentation we discuss how these method can be used in nuclear collisions. We demonstrate how correlation functions can be related to combinants and illustrate how just the information about the sign of these correlation function can be used in analyses of multiplicity distributions in nuclear collisions. It is argued that measuring couplings of the genuine multi-particle correlation functions could provide cleaner information on possible non-trivial dynamics in heavy-ion collisions.

[1] M.Rybczynski, G.Wilk, Z.Wlodarczyk PRD 103 (2021) 114026
[2] H.W.Ang, A.H.Chan, M.Ghaffar, M.Rybczynski, G.Wilk, Z.Wlodarczyk, EPJA 56 (2020) 117
[3] H.W.Ang, M.Ghaffar, A.H.Chan, M.Rybczynski, Z.Wlodarczyk, G.Wilk Mod.Phys Lett. A 34 (2019) 1950324

Speaker: Maciej Rybczynski (Jan Kochanowski University (PL))

poster_qm2022.pdf

17:30 → 18:30 Poster Session 1 T07_2

17:30 Extending the ALICE strong-interaction studies to nuclei: measurement of proton-deuteron correlations in pp collisions at $\sqrt{s} = 13$ TeV

The large data sample of high-multiplicity pp collisions collected by ALICE allows for the precise measurement of the size of source producing primary hadrons, opening the doors to a study of the interaction of different hadron species using femtoscopy techniques. In this contribution, the momentum correlation between (anti)protons and (anti)deuterons measured in pp collisions at $\sqrt{s} = 13$ TeV with ALICE is presented for the first time. The measured correlation function for $\mathrm{(\bar{p})p–(\bar{d})d}$ pairs is compared with theoretical predictions obtained considering Coulomb and Coulomb plus strong interactions and employing the Lednický-Lyuboshitz model with scattering parameters extracted from traditional scattering experiments for the p–d system. The measured correlation function can not be reproduced by any of the obtained predictions. This deviation can to large extent be interpreted as a demonstration of the late formation time of (anti)deuterons in hadron–hadron collisions. This conclusion is key for the understanding of the production mechanism of light (anti)nuclei, which is an open issue in high-energy physics. It has also important consequences for the study of antinuclei formation in the interstellar medium either from collisions triggered by high-energy cosmic rays or by decays of dark matter particles.

Speaker: Mr Bhawani Singh (Technical University of Munich, Germany)

PosterQM_slides_Bhawani_Singh.pdf

17:34 Constraining baryon annihilation in the hadronic phase of heavy-ion collisions via event-by-event fluctuations

We point out that the variance of net-baryon distribution normalized by the Skellam distribution baseline, $\kappa_2[B−B¯]/⟨B+B¯⟩$, is sensitive to the possible modification of (anti)baryon yields due to BB¯ annihilation in the hadronic phase. The corresponding measurements can thus place stringent limits on the magnitude of the BB¯ annihilation and its inverse reaction. We perform Monte Carlo simulations of the hadronic phase in Pb-Pb collisions at the LHC via the recently developed subensemble sampler + UrQMD afterburner and show that the effect survives in net-proton fluctuations, which are directly accessible experimentally. The available experimental data of the ALICE Collaboration on net-proton fluctuations disfavors a notable suppression of (anti)baryon yields in BB¯ annihilations predicted by the present version of UrQMD if only global baryon conservation is incorporated. On the other hand, the annihilations improve the data description when local baryon conservation is imposed. The two effects can be disentangled by measuring $\kappa_2[B+B¯]/⟨B+B¯⟩$, which at the LHC is notably suppressed by annihilations but virtually unaffected by baryon number conservation.

[1] O. Savchuk, V. Vovchenko, V. Koch, J. Steinheimer, H. Stoecker, arXiv:2106.08239

Speaker: Mr Oleh Savchuk (Frankfurt Institute for Advanced Studies)

17:38 Intermittency analysis in NA61/SHINE: hunting for critical point signatures in proton fluctuations

The search for experimental signatures of the critical point (CP) of strongly interacting matter is one of the main objectives of the NA61/SHINE experiment at CERN SPS. In the course of the experiment, a beam momentum (13A – 150A GeV/$c$) and system size (p+p, p+Pb, Be+Be, Ar+Sc, Xe+La, Pb+Pb) scan is performed. Local proton density fluctuations in transverse space represent an order parameter of the chiral phase transition and are expected to scale according to a universal power-law in the vicinity of the CP. They can be probed through an intermittency analysis of the proton second scaled factorial moments (SSFMs) in transverse momentum space. The first such analysis [1] revealed power-law behavior in NA49 Si+Si collisions at 158A GeV/$c$, the fitted power-law exponent being consistent with the theoretically expected critical value, within errors.

Proton intermittency analysis of experimental data poses unique challenges, in that it requires good proton identification and careful handling of statistical and systematic uncertainties, especially in the face of moderate event statistics and low per event proton multiplicity. In the present talk, we review the current status of NA61/SHINE intermittency analysis, focusing on the results of the analyzed collision systems (Be+Be, Ar+Sc, Pb+Pb), and explore the novel techniques developed and employed to account for non-critical background and estimate statistical and systematic uncertainties. In particular, we address the issue of obtaining reliable estimates and confidence intervals for the intermittency index (power-law exponent) $\phi_2$ from correlated data points, and discuss the possible treatments available. Finally, we present Monte Carlo simulation techniques used in assessing the statistical significance of intermittency results and weighing the alternative models.

References:
[1] T. Anticic et al, Eur. Phys. J. C 75: 587 (2015).

Speaker: Dr Nikolaos Davis (Institute of Nuclear Physics, Polish Academy of Sciences (PL))

Davis_QM2022.pdf

17:42 Event-by-event fluctuations of mean transverse momentum in Pb--Pb, Xe--Xe and pp collisions with ALICE

Event-by-event fluctuations of the mean transverse momentum, $\langle p_{\rm{T} }\rangle$, of charged particles produced in Pb--Pb and Xe--Xe collisions at $\sqrt {s_{\rm{NN} }}= 5.02 $ TeV and $\sqrt {s_{\rm{NN} }}= 5.44$ TeV, respectively, and pp collisions at $\sqrt s = 5.02 $ TeV are studied as a function of the charged-particle multiplicity using the ALICE detector at the LHC. Dynamical fluctuations are observed in all the three collision systems which indicates correlated particle emission. The peripheral A--A data exhibit a similar multiplicity dependence as that observed in pp. The central Pb--Pb and Xe--Xe collisions show a significant reduction of the fluctuation and are in quantitative agreement with previous measurements in Au--Au and Pb--Pb collisions at lower energies. The fluctuation has also been investigated for different transverse spherocity classes in pp collisions to understand the contribution from an underlying event.

Speaker: Tulika Tripathy (IIT- Indian Institute of Technology (IN))

17:46 Non-identical particle femtoscopy in Pb−Pb collisions at 5.02 TeV with ALICE

Femtoscopy is a tool that can be used to measure the space-time dimensions of the particle-emitting source created in heavy-ion collisions using two-particle correlations. Additionally to the measurement of the system size, one can extract the average pair-emission asymmetry between two particles with different masses. In this context, the measurement of femtoscopic correlations between charged pion and kaon pairs for different charge combinations obtained in Pb$−$Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV with ALICE at the LHC is presented. The spherical harmonics representations of the correlation functions ($C^0_0$ and $\Re C^1_1$) have been studied in different centrality bins. The obtained correlation functions are analysed, included a precise treatment of the non-femtoscopic background. The extracted source size (R) and the pair emission asymmetry ($\mu$) show an increase from peripheral to central events. Moreover, it is observed that pions are emitted closer to the centre of the particle emitting system than kaons and this result is associated to the hydrodynamic evolution of the system.

Speaker: Pritam Chakraborty (IITB- Indian Institute of Technology Bombay (IN))

Pritam_poster_QM2022_06042022.pdf

17:50 Measurement of higher-order cumulants of net-(kaon+Lambda) multiplicity distributions in $\sqrt{s_{NN}}$ = 27 GeV Au+Au collisions with STAR

The main goal of the RHIC Beam Energy Scan program is to explore the QCD phase diagram and search for the location of the QCD critical point. The cumulants of net-charge, net-proton, and net-kaon multiplicity distributions are related to the susceptibilities of conserved quantities, such as net-charge, net-baryon, and net-strangeness, respectively. However, the cumulants of net-(kaon+Lambda) multiplicity distributions are sensitive to net-strangeness susceptibility in heavy-ion collisions. Hence it can provide an insight to study flavor-dependent chemical freeze-out parameters in heavy-ion collisions. We report the higher-order diagonal cumulants ($1^{\rm st}$ up to $4^{\rm th}$ order) and their ratios in Au+Au collisions at $\sqrt{s_{NN}}$ = 27 GeV using the data taken in the year 2018. The cumulants of Lambda, kaon and their anti-particles are measured with transverse momentum between 0.4 and 1.6 GeV/$c$, and rapidity |y|<0.5. These results are compared with HRG and UrQMD models.

Speaker: changfeng li

QM2022_ChangfengPoster.pdf

17:54 Measurements of $\Lambda$-$\Lambda$ and $\Xi$-$\Xi$ correlations in Au+Au collisions at$\sqrt{{s_{\rm{NN}}}}$ = 200 $\rm{GeV}$ at RHIC-STAR

The interaction between hyperon-hyperon (YY) is not well understood theoretically and experimentally. The YY interaction is important to understand the equation of state of neutron star interior as well as to search for exotic hadrons such as H-dibaryon. The H-dibaryon was proposed as a stable six-quark state resulting from combination of two $\Lambda$ hyperons. According to the lattice QCD calculation [1], H-dibaryon could be in a deeply bound state or in a shallow bound state, or two $\Lambda$ hyperons have weak unbound attractive interaction, depending on quark mass. On the other hand, the observation of double hypernuclei [2] suggests that they are not in a deeply bound state, although more experimental inputs are needed to clarify the nature of possible H-dibaryon state. For the case of two $\Xi$ (strangeness S = -4) interaction, whether or not there is a bound state of $\Xi$-$\Xi$ is being discussed.
In high-energy heavy-ion collisions, a large number of particles including (multi-) strangeness are produced, which allows us to study those interactions via femtoscopic measurements with better precision. The correlation function is affected by strong interaction, quantum statistics, and Coulomb interaction in low relative momentum of particle pairs of interest.

In this poster, the status of measurements of $\Lambda$-$\Lambda$ and $\Xi$-$\Xi$ correlation functions in Au+Au collisions at $\sqrt{{s_{\rm{NN}}}}$ = 200 ${\rm GeV}$ at RHIC-STAR will be reported.

[1] T. Inoue ${\it et~al.}$ (HAL QCD Collaboration), Nucl. Phys. A881, 28 (2012)
[2] H. Takahashi ${\it{et~al}}$., Phys. Rev. Lett. 87, 212502 (2001)

Speaker: Moe Isshiki

20220406_QM2022_isshiki_finalfinal.pdf

17:58 Intermittency of charged hadrons in NA61/SHINE

NA61/SHINE conducts the search for a hypothesized critical point of strongly interacting matter by scanning in collision energy and mass of colliding nuclei. In this field, one of the key methods is to search for the intermittency signal that, if observed, can be related to the effect of the system self-similarity in the vicinity of a possible critical point. This would lead to the power-law correlation function. This talk will cover the experimental results obtained in Pb+Pb collisions at 30A GeV/c beam momentum for the scaled factorial moments of the second and higher orders as a function of the phase space cell size in the transverse momentum plane. The results will be presented for all charged hadrons and separately for positively and negatively charged ones. No intermittency signal is observed. This seems to be in tension with corresponding preliminary results by the STAR Collaboration.

Speaker: Tobiasz Czopowicz (Jan Kochanowski University, Warsaw University of Technology)

TC_QM-poster_2022-04-06.pdf

18:02 Measurement of Intermittency for Charged Particles in Au + Au Collisions at $\sqrt{s_\mathrm{NN}}$ = 7.7-200 GeV from STAR

One of the main goals of RHIC beam energy scan (BES) program is to search for the signatures of the QCD critical point in heavy-ion collisions. Local density fluctuations near the QCD critical point exhibit strong intermittency which is revealed as the scale (power-law) dependence of scaled factorial moments on phase-space resolution. The scaling exponent is related to the critical component and can be extracted from the intermittency analysis of scaled factorial moments. The energy dependence of the scaling exponent could be used to search for the signature of the QCD critical point. Similar measurements have been carried out by the NA49 and the NA61 experiments in heavy-ion collisions with different system sizes.

In this talk, we will report the first measurement of intermittency for charged particles in Au + Au collisions from the STAR experiment in the first phase of RHIC BES. Scaled factorial moments (up to the sixth order) for charged particles at $\sqrt{s_\mathrm{NN}}$ = 7.7-200 GeV will be presented. Moreover, we will show the energy and centrality dependence of the scaling exponent. The physics implications of these results will be discussed.

Speaker: Jin Wu (Central China Normal University)

QM2022-poster-Intermittency-STAR.pdf

18:06 Femtoscopic measurements of strange hadrons in Au+Au collisions at the STAR experiment

Relativistic heavy-ion collisions can study properties of nuclear matter in high-energy experiments like the STAR experiment. Femtoscopy, which relies on information carried by the particles produced in the collisions, is one of methods to learn about the bulk matter. By studying the quantum statistical effects and final state interactions between two particles, one can study spatial and temporal extents of particle emitting source. For the case of kaons, the correlation functions are sensitive to the early stage of the collision evolution and provide different information about particle-emitting sources compared to pions.

Information on the final state interactions amongst the particles under study can also be extracted from the measurement. Especially, in the case of strange particle correlations, one could investigate hyperon-nucleon inter- actions which is little known.

This talk will present the femtoscopic measurements of strange particle with charged and neutral kaons as well as $\Xi$ hyperons correlations in Au+Au collisions at the BES program and top RHIC energy. The results will be compared with the theoretical predictions.

Speaker: Diana Pawłowska (Warsaw University of Technology)

QM2022_poster_DPawlowska.pdf

18:10 Event-by-event correlations and fluctuations with strongly intensive quantities in heavy-ion collisions with ALICE

The strongly intensive quantity $\Sigma$ is a new observable, introduced recently to the domain of heavy-ion physics. In superposition models which assume independent particle production from statistically identical sources, $\Sigma$ is insensitive to the number of sources and its fluctuations, contrary to the standard forward-backward correlation coefficient ($b_{\rm corr}$). Therefore, it provides direct information on the multiplicity correlations and fluctuations from a single source.

This poster presents new results on forward-backward correlations studied with the quantity $\Sigma$, measured by ALICE at the LHC in Xe--Xe reactions at $\sqrt{s_{\rm NN}}=5.44$ TeV and in Pb--Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ and $5.02$ TeV. The data is shown as a function of the $\eta$ gap between forward and backward pseudorapidity intervals, the centrality of the collision, and the width of the centrality bin. The study is made with two independent centrality estimators. An opposite ordering of values of $\Sigma$ as a function of centrality class in Pb--Pb and Xe--Xe collisions is observed for the experimental data and MC HIJING simulations. This nontrivial discrepancy implies that the physical mechanism of particle production differs from that predicted by the models.

Speaker: Iwona Anna Sputowska (Polish Academy of Sciences (PL))

2022-04-01-IwonaSputowska_QM22_vol4.pdf

18:14 Jet-like correlations with $V^{0}$ triggers in pp and Pb--Pb collisions with ALICE at the LHC

The measurement of azimuthal correlations between two particles is a powerful tool to investigate the properties of strongly-interacting nuclear matter created in ultra-relativistic heavy-ion collisions. In particular, studying the near-and away-side hadron yields associated with trigger particles can provide important information to understand both the jet-medium interaction and hadron production mechanism. In this contribution, we present a study of two-particle correlations $\mathrm{V^{0}}$($\mathrm{K^{0}_{S}}$, $\Lambda/\overline{\Lambda}$) and charged hadrons as trigger particles of transverse momentum $8 < p_\mathrm{T,trig} < 16$ $\mathrm {GeV}/c$, and associated charged particles of $1$ $\mathrm{GeV}/c< p_\mathrm{T,assoc} < p_\mathrm{T,trig}$ at mid-rapidity in pp and Pb--Pb collisions at $\sqrt{s_{\rm{NN}}}$ $=5.02$ TeV recorded with the ALICE detector.
After subtracting the contributions of the flow background, the per-trigger yields are calculated on the near and away-side. The ratio of the per-trigger yields in Pb--Pb collisions with respect to pp collisions, $I_{\mathrm{AA}}$, is measured in the most central 0--10% collisions. A significant enhancement of $I_{\mathrm{AA}}$ for different particles species is observed at the lowest $p_\mathrm{T,assoc}$ on both near and away-side, while strong suppression of $I_{\mathrm{AA}}$ for $p_\mathrm{T,assoc}$ $>3$ $\mathrm{GeV}/c$ on away-side is observed as expected from strong in-medium energy loss. The data are compared to AMPT, HIJING and EPOS models. Most calculations, but HIJING, qualitatively describe the near-side and away-side yield modification at intermediate and high $p_\mathrm{T,assoc}$.

Speaker: Mustafa Anaam (Central China Normal University CCNU (CN))

Jet like correlation with V0_ poster.pdf

18:18 Fluctuations of identified particle numbers in partial chemical equilibrium

First six cumulants of proton number are calculated in the statistical resonance gas model with chemical potentials for every stable identified hadron species. The chemical potentials are chosen in such a way that the average particle numbers after decay of resonances are kept constant independently of temperature and equal to the values given at the chemical freeze-out. This corresponds to a fireball with hadron abundances set at the chemical freeze-out, which further cools down to the thermal freeze-out. It is shown that also the volume-independent ratios of cumulants stay nearly constant in such a scenario. This is useful information, because it shows that the observed non-critical values of volume independent cumulant ratios, which could be modified at any time during the fireball evolution, are not too much influenced after chemical freeze-out.

Speaker: Boris Tomasik (Univerzita Mateja Bela (SK))

tomasik_QMposter.pdf

17:30 → 18:30 Poster Session 1 T14_1

17:30 S-Matrix HRG description of light flavour hadrons and (anti-)(hyper-)nuclei production at the LHC

The yields of light flavour hadrons and light (anti-)nuclei including (anti-)hypernuclei have been measured by the ALICE collaboration at LHC/CERN at various multiplicity bins in proton-proton, proton-lead and lead-lead collisions. It is observed that the strangeness and (anti-)nuclei production increase non-linearly with charged-particle multiplicity (dNch/dy) and is independent of the collision system. We compare the above data with the thermal model analysis that accounts for the exact conservation of quantum numbers such as strangeness and baryon number. The interactions among hadrons are included using the S-matrix corrections based on known phase shift analyses.

We show that the above thermal model can capture the observed properties of light flavour hadron yields as well as light (anti-)nuclei including anti-hypertriton as a function of charged-particle multiplicity.

Speaker: Natasha Sharma (Panjab University (IN))

QM2022-Poster-Natasha.pdf

17:34 Neutral meson measurements in ALICE in pp collisions at $\sqrt{s} =$ 13 TeV

The measurement of neutral mesons in pp collisions allows a test of perturbative QCD calculations and represents an important baseline for heavy-ion studies. Neutral mesons are reconstructed in ALICE with multiple methods in a very wide range of transverse momenta and thus impose restrictions on the parton distribution functions and fragmentation functions over a wide kinematic region. Moreover, observations in high-multiplicity pp and p-Pb collisions show surprising similarities with those in heavy-ion collisions. Measured identified particle spectra in hard pp collisions give further insight into the hadron chemistry in such high charged-particle multiplicity events.

In this talk, detailed measurements of the neutral pion, eta and omega mesons will be presented in several multiplicity classes in pp collisions at $\sqrt{s}$ = 13 TeV. The different analysis techniques using two different calorimeters and the reconstruction of conversion photons via their $e^{+}e^{-}$ pairs will be briefly explained. In particular, the inclusion of the merged photon clusters analysis using the calorimeter allows the extension of the neutral pion measurement up to an unprecedented high $p_{\rm T}$ of 200 GeV/$c$ in pp and p-Pb collisions for identified hadron spectra. Results will be compared to pQCD calculations.

Speaker: Adrian Florin Mechler (Goethe University Frankfurt (DE))

QM_22_Adrian_Mechler.pdf

17:38 Charged-particle $p_{\mathrm{T}} $ spectra as a function of multiplicity in pp, p--A and A--A collisions measured with ALICE

The ALICE experiment is dedicated to investigating a hot and dense deconfined state of matter created in heavy-ion collisions. Complementary measurements in smaller collision systems have shown signs of collectivity emerging even in simple hadronic collisions. Particle production at the LHC is driven by a complex interplay of soft and hard QCD processes. It is still challenging for modern Monte-Carlo event generators to describe particle production for all collision systems consistently. The correlation between hadron transverse momentum ($p_{\mathrm{T}} $) spectra and the event multiplicity serves as a sensitive observable to provide insight into different particle production mechanisms at play.
This poster reports on the measurement of charged-particle transverse momentum spectra as a function of charged-particle multiplicity density, obtained using a 2-dimensional unfolding procedure. The $p_{\mathrm{T}} $ spectra of charged hadrons are reported as a function of center-of-mass energy in different colliding systems. In addition, particle spectra measured in pp, p--Pb, and Pb--Pb collisions at $\sqrt{s_\mathrm{NN}} = 5.02\ \mathrm{TeV}$ are compared. This allows for a study of the center-of-mass energy dependence of particle production mechanisms in different colliding systems.

Speaker: Mario Kruger (Goethe University Frankfurt (DE))

2022-04-06-QM22.pdf

17:42 From hydro, quark coalescence to jet quenching, the coupled approach to solving the RAA-v2 puzzle in high-energy heavy-ion collisions

Hydrodynamic expansion and jet quenching are responsible for the production of low and high transverse-momentum ($𝑝_𝑇$) particle in heavy-ion collisions, respectively. However, it is still a challenge to simultaneously describe hadron nuclear modification factor $𝑅_{𝐴𝐴}$ and elliptic flow $𝑣_2$, especially in the intermediate $𝑝_𝑇$ region of 2<$𝑝_𝑇$<10 GeV/c. In this talk, we combine hydrodynamics, quark coalescence and jet quenching as well as the hadron cascade, and study their effects on hadron spectra and flow. We find the key to solving the $𝑅_{𝐴𝐴}-𝑣_{2}$ puzzle is the incorporation of quark coalescence into the state-of-the-art event-by-event simulations of heavy-ion collisions. Specifically, our new theoretical framework combines 1) the Coupled Linearized Boltzmann Transport and Hydrodynamic (CoLBT-Hydro) model, 2) a hadronization model including Cooper-Frye sampling, quark coalescence and string fragmentation, and 3) a hadron cascade model. For the first time, we can consistently describe and understand the experimental data on $𝑅_{𝐴𝐴}$ and $𝑣_2$ along with their flavor dependence and hadron chemistry (proton-to-pion and kaon-to-pion ratios) from low to intermediate $𝑝_𝑇$ and high $𝑝_𝑇$ in heavy-ion collisions at both RHIC and LHC energies. Our prediction is an example of high-precision tests of the quark coalescence model in nuclear collisions.

[1] Wenbin Zhao, Weiyao Ke, Wei Chen, Tan Luo and Xin-Nian Wang,arXiv:2103.14657 [hep-ph].

[2] Wenbin Zhao, Che-Ming Ko, YuXin Liu, Guangyou Qin and Huichao Song, Phys. Rev. Lett. 125, 072301 (2020).

Speaker: Wenbin Zhao (Wayne State University)

Wenbin_Zhao_QM_2022.mp4

Wenbin_Zhao_QM_2022.pdf

17:46 Measurement of directed flow at forward and backward pseudorapidity in Au+Au collisions at $\sqrt{s_{NN}}=27 $ GeV with the Event Plane Detector (EPD) from STAR

The measurement of pseudorapidity ($\eta$) dependence of directed flow ($v_{1}$) can provide unique constraints on the three-dimensional initial conditions in heavy-ion collisions. In the year 2018, the Event Plane Detector (EPD, $2.1<|\eta|<5.1$) was installed in STAR and used for the Beam Energy Scan phase-II (BES-II) data taking. The combination of EPD and high statistics BES-II data enables us to extend the $v_{1}$ measurement to the very forward and backward psuedorapidity regions. In this poster, we will discuss the techniques for measuring $v_{1}$ with a scintillator detector like EPD and present results of $v_{1}$ in Au+Au collisions at $\sqrt{s_{NN}}=27 $ GeV. We will also compare the results to different models such as AMPT, UrQMD, and hydrodynamic simulations.

Speaker: Xiaoyu Liu

QM2022_Poster_340_Xiaoyu_Liu_v7.pdf

17:50 Neutral mesons flow and yields in AgAg@1.58 AGev at HADES

The Dielectron Spectrometer HADES operated at the SIS18 synchrotron, GSI Darmstadt recently provided new intriguing results on production of electron pairs and of strangeness from nucleus-nucleus collisions, as well as from elementary reactions, in energy region of $1 - 2$ A GeV. In 2019 the spectrometer was complemented by an electromagnetic calorimeter based on lead-glass modules, which allows us to measure photons, thus study production of the $\pi^0$ and $\eta$ mesons via their two-photon decay. The knowledge of the neutral meson production is a mandatory prerequisite for the interpretation of dielectron data and at the same time almost no respective data about their production in nucleus-nucleus collisions are presently available for this energy range.
Particularly, directed and elliptic flow of neutral mesons will be shown with respect to transverse momentum and rapidity for different centrality classes in Ag + Ag collisions at 1.58 A GeV. Results of analysis corresponding to $14\times10^9$ events will be confronted with results of other experiments and with up-to-date model calculations.

Speaker: Alexandr Prozorov

ProzorovPosterQM2022-3.pdf

17:54 Characterizing pp and p–Pb collisions using very forward energy with ALICE

The very forward energy in hadron-hadron collisions contains information about the fragmentation of the projectile and the target, providing direct insights into the initial stages of high-energy hadronic collisions. By constraining the very forward energy, one can control the event activity in the collision. Results on very forward energy, measured by the ALICE zero degree calorimeters (ZDCs), and its correlation with particle production at midrapidity will be presented for $\sqrt{s} = 13$ TeV pp collisions and $\sqrt{s_{\rm NN}} = 8.16$ TeV p–Pb collisions. Traditional underlying event (UE) studies at midrapidity provide an alternative measure of the event activity. In this poster, these two different event-activity measurements will be compared for pp collisions. Finally, the results will be compared with the expectations of hadronic interaction event generators, such as PYTHIA and EPOS, to test if models can describe the forward fragmentation, where observables are mainly driven by non-perturbative QCD physics.

Speaker: Chiara Oppedisano (Universita e INFN Torino (IT))

QM2022-Oppedisano.pdf

17:58 Status of multi-strange dibaryon and hidden strangeness pentaquark searches at the LHC with the ALICE detector

Quantum chromodynamics (QCD), the fundamental theory of strong interactions, allows the existence of exotic hadrons other than mesons and baryons. An exotic hadron consisting of six quarks is called a dibaryon, and a dibaryon containing strange quarks (multi-strangedibaryon) has not yet been discovered. An exotic hadron consisting of four quarks and an antiquark is called a pentaquark, and the recent discovery of the hidden charm pentaquarks P$_{c}(4312)^{+}$ , P$_{c}(4440)^{+}$, and P$_{c}(4457)^{+}$ by LHCb has reopened the question of whether pentaquarks exist in the strange sector.

The recent lattice QCD calculations by HAL QCD showed the attractive potentials between $\Lambda\Lambda$, N${\Xi}$, and N${\Omega}$. The strangeness enhancement, measured by ALICE as a function of increasing charged particle multiplicity even in pp collisions, further adds to the likelihood of observing strange pentaquark and dibaryon states. A consequence of these attractive potentials and strangeness enhancement is that the H-dibaryon can be a resonance state of $\Lambda\Lambda$, or N${\Xi}$, and N${\Omega}$ may appear as a quasi-bound state, strongly decaying at the collision point. Also, following analogous decay channels for the five quark P$_{c}^{+}$ states into the strange sector, a P$_{s}$ decaying strongly with daughters $\phi$p, $\Lambda K$, $\Lambda K^*$, and $\Sigma^{∗}K$ may appear as a bound state.

In this poster, current status of the searches for H-dibaryon, N$\Omega$-dibaryon, and hidden strangeness pentaquark states via invariant mass reconstruction with Run 2 data will be reported. Moreover, perspectives for LHC Run 3 will also be shown.

Speakers: Jacobb Lee Martinez (University of Houston (US)), Ryoka Tokumoto (Hiroshima University (JP))

QM_2022_Poster_Ryoka_Jacobb_v4.pdf

18:02 Measurements of charge, strangeness, and baryon number balance functions in pp and Pb-Pb collisions in ALICE

Two-particle charge-dependent correlations (balance functions) are sensitive to the production and transport of conserved quantum numbers in the medium created in hadronic collisions. In this con- tribution, recent ALICE measurements of the balance functions of charge, strangeness, and baryon numbers are presented. Balance functions for all combinations of identified charged-hadron ($\pi$, K, p) pairs are calculated in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV as a function of collision centrality. The balancing in azimuthal angle and rapidity is expected to provide information about quark diffusion and delayed hadronization, respectively. For the latter, a possible two-stage quark-production scenario $-$ early production of strange quarks and late production of light quarks $-$ is discussed. In addition, balance function integrals of (un)identified hadron pairs as a function of collision centralities, which provide the information about different pairing probabilities, are calculated for the first time. To investigate further the strangeness enhancement with multiplicity in small systems, recent measurements of how the production of doubly-strange $\Xi$ baryons is balanced with mesons (strange kaons and non-strange pions) and baryons ($\Xi$, $\Lambda$, and p) in pp collisions at $\sqrt{s}$ = 13 TeV are shown. The balance is studied by triggering on $\Xi$ baryons and subtracting the same quantum number from the opposite quantum number per-trigger yields. In particular, the multiplicity dependence is studied in order to identify if the same strangeness-production mechanism is at work in low- and high-multiplicity pp collisions. The results are compared to predictions from Monte Carlo models with various tunes of PYTHIA8 (Lund string-based approach) and EPOS LHC (based on core-corona approach).

Speaker: Sumit Basu (Lund University (SE))

QM2022_SumitBasu.pdf

18:06 Pseudorapidity distributions of charged particles measured with the STAR Event Plane Detector in 19.6 and 27 GeV Au+Au collisions

In 2018, STAR installed the Event Plane Detector (EPD) with a pseudorapidity coverage of $2.15<|\eta|<5.09$. The EPD has enhanced STAR's capabilities in triggering, centrality measurement and event plane determination. Due to its fine radial granularity, it can also be utilized to measure pseudorapidity distributions of charged particles. In order to make such a measurement, the response of the detector material to the produced primary particles has to be understood. Monte Carlo simulations are used to determine the detector response matrix which is then used in an iterative unfolding procedure to obtain the corrected pseudorapidity distributions. As a first step towards such measurements at even lower energies, we present the results on charged particle pseudorapidity distributions measured with the EPD in $\sqrt{s_{_{NN}}}=19.6$ and 27 GeV Au+Au collisions.

Speaker: Mate Csanad (Eotvos University, Budapest)

csanad_EPDdndeta_QM22_poster_allpages.pdf

18:10 K$^{*\pm}$ production in Pb--Pb collisions with ALICE at the LHC

Short-lived hadronic resonances are very useful to probe the late-stage evolution of ultra-relativistic heavy-ion collisions. Since their lifetimes are comparable to the hadronic phase timespan, their measured yields are modified via rescattering and regeneration processes. The suppression of the K$^{*0}$/K ratio in central Pb--Pb collisions compared to pp interactions already hints at the dominance of rescattering effects over regeneration effects in the hadronic phase. The mass and lifetime of K$^{*\pm}$ are comparable to those of K$^{*0}$. Hence, systematic measurements of K$^{*0}$ and K$^{*\pm}$ enable us to investigate further the dynamics of the hadronic phase, to study its lifetime and to probe in-medium parton energy loss with high $p_{\mathrm{T}}$ resonances.

We report on the first measurement of K$^{*\pm}$ production in midrapidity for Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV. The results include the transverse momentum spectra, integrated yields, mean transverse momenta, particle ratios, and nuclear modification factor as a function of charged-particle multiplicity. These results will be compared with published K$^{*0}$ measurements at the same energy.

Speaker: Prottay Das (National Institute of Science Education and Research (NISER) (IN))

Prottay_QMconf2022_CKS.pdf

18:14 Investigating strangeness production in pp collisions using multi-differential analyses with ALICE at the LHC

The ratio of strange to non-strange hadron yields increases from low- multiplicity to high-multiplicity hadronic interactions, reaching values observed in heavy-ion collisions. The ALICE experiment investigates the microscopic origin of this striking phenomenon by performing dedicated multi-differential analyses in pp collisions at $\sqrt{s}$ = 13 TeV.

To separate strange hadrons produced in jets from those produced in soft processes, the angular correlation between high-charged particles and strange hadrons is exploited. The near-side jet and out-of-jet yield of $\mathrm{K^0_S}$ and $\Xi^{\pm}$ are studied as a function of the charged particle multiplicity, up to values comparable to those reached in peripheral Pb–Pb collisions.

In order to disentangle initial and final state effects, a new analysis exploits the concept of the effective energy available for particle production, which is anti-correlated with the forward energy deposited in the Zero Degree Calorimeters (ZDC). (Multi-)strange hadron production is studied as a function of the charged particle multiplicity measured at midrapidity and of the forward energy detected by the ZDC.

The results suggest that soft (i.e., out-of-jet) processes are the dominant contribution to strange particle production and provide new insights on the role of initial state effects on strangeness enhancement in pp collisions.

Speakers: Chiara De Martin (Universita e INFN Trieste (IT)), Francesca Ercolessi (Universita e INFN, Bologna (IT))

QMPoster_FErcolessi.pdf

18:18 Study of the full Probability Density Function for strange hadron production in pp collisions with ALICE

Measurements of strange hadron production in pp and p-Pb collisions had been used as a reference for the study of the so-called strangeness enhancement effect, occurring in heavy ion collisions where QGP formation is observed.
Recently, the ALICE Collaboration studied strangeness production in pp interactions, unveiling unexpected features in the strange hadron to pion yield ratios. These observations have been obtained by a statistical analysis of the number of strange particles in a given set of inelastic pp events. In this sense, formation rates account for the Probability Density Function (PDF) underlying the production mechanism on an average. More insightful information on the production of strange particles and, more in general, on hadronization would come from the knowledge of the full PDF.
In this work a new event-by-event technique for extracting the full PDF for single and multi-strange hadron production will be illustrated, together with first estimates on the statistical accuracy achievable by analyzing LHC Run 2 data and the soon-to-come new data from the LHC Run 3 campaign.

Speaker: Sara Pucillo (Universita e INFN Torino (IT))

SaraPucillo_QM2022_poster.pdf

17:30 → 18:30 Poster Session 1 T14_2

17:30 Study of underlying event activity in pp and p-Pb collisions at 5.02 TeV with ALICE

The underlying event (UE) has been studied in ALICE for pp collisions at $\sqrt{s}$ =5.02 TeV. The average number density and the average total transverse momentum ($p_{\rm T}$) are studied in the near, away and transverse regions as a function of the leading particle $p_{\rm T}$. Results at 5.02 TeV show qualitatively the same behavior as observed at different energies.
For the first time the UE studies were performed also in p--Pb collisions, available at LHC at the same center-of-mass energy as for pp collisions. The transverse region is the most sensitive to the underlying event, while the toward and away regions include both the UE and jet fragments from the hard partonic scattering. To isolate the jet-like signal, the event activity in the transverse region is subtracted from the toward and away regions. Results for the two colliding systems will be compared with predictions from event generators like PYTHIA 8 and EPOS-LHC.

Speaker: Ahsan Mehmood Khan (Central China Normal University CCNU (CN))

17:34 Deep learning the physics of heavy-ion collisions at the CBM experiment with PointNet

Deep Learning methods are a popular tool for efficient and fast data analysis in high energy/ nuclear physics experiments. The upcoming Compressed Baryonic Matter (CBM) experiment will study nuclear-nuclear collisions in the range of 10- 40 AGeV at an unprecedented event rate of up to 10MHz, creating about 1TB/s of raw data. In order to run the experiment to its full potential, novel methods for event characterisation and subsequent data analysis are necessary. In this talk, we show that PointNet based DL models are an ideal candidate for such tasks on experimental data with minimal pre-processing. We demonstrate that PointNet based models can perform, event-by-event impact parameter reconstruction at CBM experiment using directly the hits/ tracks of particles from the detector planes [1, 2]. The models have their mean error varying from -0.33 to 0.22 fm for impact parameters 2-14 fm and outperform conventional methods based on a single observable such as track multiplicity. We also show that PointNet models can accurately identify the nature of QCD transition at the CBM experiment [3]. The DL models distinguish a first order phase transition from a crossover transition using the reconstructed tracks of charged particles with an accuracy of up to 99.8%. The models are also shown to outperform methods relying on conventional mean observables.

References
[1] Omana Kuttan, M., Steinheimer, J., Zhou, K., Redelbach, A., & Stoecker, H. (2020). A fast centrality-meter for heavy-ion collisions at the CBM experiment. Physics Letters B, 811, 135872

[2] Omana Kuttan, M., Steinheimer, J., Zhou, K., Redelbach, A., & Stoecker, H. (2021). Deep Learning Based Impact Parameter Determination for the CBM Experiment. Particles, 4(1), 47-52.

[3] Omana Kuttan, M., Zhou, K., Steinheimer, J., Redelbach, A., & Stoecker, H. (2021). An equation-of-state-meter for CBM using PointNet. Journal of High Energy Physics, 2021(10), 1-25.

Speaker: Manjunath Omana Kuttan (Frankfurt Institute for Advanced Studies, Goethe-University Frankfurt am Main)

qm22_manjunath.pdf

17:38 CBM performance for anisotropic flow of charged hadrons and (multi)-strange hyperons in heavy-ion collisions

Anisotropic flow of produced hadrons, in particular of multi-strange hyperons, is an important observable for understanding the dynamics and properties of the QCD matter created in heavy-ion collisions at high net baryon densities. The performance of the Compressed Baryonic Matter (CBM) experiment at FAIR is presented for anisotropic flow measurement relative to the projectile spectator plane for charged hadrons and rarely produced multi-strange hyperons. Multi-differential results for different flow harmonics are obtained as a function of rapidity and transverse momentum in different centrality classes.
The performance for collisions of gold ions for the FAIR energy range, $\sqrt{s_{NN}} = 2.9 - 4.9\ GeV$, is studied using various heavy-ion event generators in GEANT4 Monte-Carlo transport coupled to simulations of the CBM detector response. The evaluation of possible systematic biases in CBM, such as due to non-flow, detector anisotropies and inefficiencies, will be presented. It will be complemented with the comparison of various flow measurement techniques, including the scalar product method with multiple subevents and the invariant mass fit method for flow extraction of (multi-)strange decays, where large combinatorial background has to be subtracted. The application of the multi-particle correlation techniques and flow cumulants for low multiplicity collisions at CBM will also be presented.

Speaker: Oleksii Lubynets (GSI, Darmstadt, Germany; Goethe Universität Frankfurt, Germany)

QM2022_poster_Strange_flow_Lubynets.pdf

17:42 Performance of the CBM experiment at FAIR for measurement of charged hadron anisotropic flow

The Compressed Baryonic Matter experiment (CBM) at FAIR aims to investigate the high net baryon density and moderate temperature region of the QCD phase diagram, using collisions of heavy ions at center-of-mass energies of a few GeV per nucleon. Anisotropic transverse flow is among the key observables to study the properties of matter created in such collisions. The CBM performance for charged hadron’s anisotropic flow measurements is studied with Monte-Carlo simulations using gold ions at SIS-100 energies with lab momentum up to 12A GeV/c employing different heavy-ion event generators. Various combinations of CBM detector subsystems are used to investigate the possible systematic biases in flow measurement and to study the effects of detector azimuthal non-uniformity. The resulting performance of CBM for flow measurements is demonstrated for different harmonics of identified charged hadron anisotropic flow as a function of rapidity and transverse momentum in different centrality classes.

Speaker: Oleg Golosov (National Research Nuclear University MEPhI (RU))

17:46 Measurement of neutral meson production as a function of multiplicity in pp collisions at $\sqrt{s}$ = 13 TeV with ALICE

The precise measurement of the neutral meson production in pp collisions can be used to constrain fragmentation functions and parton density functions needed by pQCD calculations. Additionally, those measurements serve as input for direct photon analyses. Moreover, the dependence of the neutral meson cross section on the event charged-particle multiplicity could give further insight into possible final-state effects in high-multiplicity pp collisions, in which other measurements show surprising similarities with those in heavy-ion collisions
In this poster, the invariant cross sections of the $\pi^0$ and $\eta$ meson as a function of $p_{\rm T}$ in pp collisions at $\sqrt{s}$ = 13 TeV for different charged-particle multiplicity classes, measured with ALICE, will be presented. The measurement covers a $p_{\rm T}$ range from 0.2 to 200 GeV/$c$ for the $\pi^0$ and up to 50 GeV/$c$ for the $\eta$ meson. This large $p_{\rm T}$ coverage is achieved by combining the results from several partially independent reconstruction techniques available in ALICE where the decay photons were detected with the electromagnetic calorimeters, or via the central tracking system using $e^+e^-$ pairs from conversions in the detector material. Furthermore the results will be compared to pQCD calculations.

Speaker: Joshua Leon Konig (Goethe University Frankfurt (DE))

NeutralMesons_JoshuaKoenig_QM_Poster_V4.pdf

17:50 Anisotropic flow of φ mesons in Au+Au collisions at √sNN = 14.6 and 19.6 GeV in the second phase of beam energy scan program

The Relativistic Heavy-Ion Collider aims to study the deconfined state of quarks and gluons known as Quark-Gluon Plasma and its transition from hadronic matter. $\phi$($s\bar s$) meson has a small hadronic cross-section implying lesser final state interactions in the medium. Thus, the elliptic flow ($v_{2}$) of $\phi$ mesons is sensitive to the properties of the medium in the initial stages of heavy-ion collisions. The $v_{2}$ of $\phi$ mesons hints at being lower than that of the other hadrons and deviates drastically from the number of constituent quark scaling below the center-of-mass energy of 19.6 GeV obtained in the first phase of Beam Energy Scan (BES-I) program indicating a difference in dynamics of the medium. Triangular flow ($v_{3}$), originating from initial geometry fluctuations, is suggested to be an even more sensitive probe for the viscosity of the medium and initial density profile of the colliding nuclei. Further, the ratios of higher-order flow harmonics are suggested to depend on the transport properties of the medium. \

In this poster, we will present $v_{2}$($p_{T}$) and $v_{3}$($p_{T}$) of $\phi$ mesons and their ratio in Au+Au collisions at $\sqrt{s_{\mathrm {NN}}}$ = 14.6 and 19.6~GeV from the second phase of Beam Energy Scan (BES-II) program. The centrality and energy dependence of the observables will be presented. The new results shall also be compared with the previous results from BES-I.

Speaker: Priyanshi Sinha

Priyanshi_QMposterUpdated.pdf

17:54 Energy dependence of underlying event observables measured with ALICE at the LHC

The transverse region of di-hadron correlations is known to be
very sensitive to the underlying event (UE), and initial- and
final-state radiation (ISR and FSR). In pp collisions, particle
production in the transverse azimuthal region, with respect to
the leading particle, reaches a plateau for $p^{leading}_{T}>$ 5
GeV/c. In this contribution, a study of the multiplicity
distributions in the plateau region for pp collisions at
$\sqrt{s}$ = 0.9, 2.76, 5.02, 7 and 13 TeV with ALICE is
reported within $|\eta|<$ 0.8. This region is further divided
into trans-max and trans-min regions which are sensitive to ISR,
FSR and UE, respectively. The UE component is found to increase
like a power of the center-of-mass energy, resembling the
center-of-mass energy dependence of the parameter which
regulates multiparton interactions in event generators like
Pythia. KNO-like scaling properties of the multiplicity
distributions are also reported. Measurements are compared with
general-purpose Monte Carlo generators.

Speaker: Feng Fan (Central China Normal University CCNU (CN))

QM22_poster_Feng.pdf

17:58 Application of the Three-fluid Hydrodynamics-based Generator THESEUS in CBM at FAIR

The Compressed Baryonic Matter experiment (CBM) aims to study the area of the
QCD phase diagram at high net baryon densities and moderate temperatures. It is predicted by Three-fluid Hydrodynamics-based Event Simulator (THESEUS) that one of the signatures of phase transition is a change in shape of the mid-rapidity curvature and yield.
In this contribution we will present CBM performance for proton rapidity- transverse mass spectra. The results are obtained for Au+Au collisions at $\sqrt(s_NN)$ = 2.7 - 4.9 GeV/c produced by THESEUS model. CBM detector response is simulated with the GEANT3 engine and reconstruction is done using the CbmRoot framework. Protons are identified with Time-of-Flight technique using 2 different approaches. Obtained spectra are corrected for detector biases using the UrQMD event generator. Results are compared with simulated values and sources of systematic biases are discussed.

Speaker: Elena Volkova (Eberhard Karls Universität Tübingen)

QM BW 2022-2.pdf

18:02 Charged kaon femtoscopy with Lévy sources in $\sqrt{s_{NN}}=200$ GeV Au+Au collisions at PHENIX

The PHENIX experiment measured two-particle Bose- Einstein quantum-statistical correlations of charged kaons in Au+Au collisions $\sqrt{s_{NN}}=200$ GeV collision. The correlation functions are parametrized assuming that the source emitting the particles has a Lévy-shaped characterized by the $\alpha$ Lévy exponent and the $R$ Lévy scale. By introducing the $\lambda$ intercept parameter we account for the core-halo fraction. The parameters are investigated as the function of transverse mass. The comparison of the parameters measured for charged kaons to those measured from pion-pion correlation may clarify the connection of Lévy parameters to physical processes.

Speaker: Mr László Kovács (Eötvös University)

qm22_kaon_femtoscopy_poster.pdf

18:06 Rapidity dependence of K*$^{0}$ and $\phi$ production in p-Pb collisions with ALICE at the LHC

Hadronic resonances are interesting probes of the hot and dense matter created in the heavy-ion collision. Due to their short lifetimes, resonances are useful tools to understand the mechanism of particle production and properties of the hadronic phase created after the collision. The yield of resonances might be modified with respect to expectations due to effects such as rescattering and regeneration. Moreover, the study of resonance production in p--Pb collisions fills the gap between pp and heavy-ion (Pb--Pb, Xe--Xe) collisions and helps us understand initial state effects due to cold nuclear matter. In asymmetric collisions (p--Pb), the particle yield will differ in the p and Pb-going direction. The rapidity asymmetry ($Y_{\rm{asym}}$) and nuclear modification factor will help in understanding the nuclear modification effects, like shadowing, the Cronin enhancement, multiple scattering, and energy loss.
We will report on the production of K*$^{0}$ and $\phi$ resonances in p--Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 5.02 TeV. The measurements are performed in five rapidity windows in the interval -1.2 $< y <$ 0.3 . The results include transverse momentum spectra ($p_{\mathrm{T}}$), integrated yields, mean transverse momenta for various rapidity windows, and multiplicity classes, including minimum bias. The rapidity asymmetry ($Y_{\rm{asym}}$) and nuclear modification factor (Q$_{\rm{CP}}$) are studied to understand the particle production mechanisms and nuclear effects. The results will also be compared with model predictions.

Speaker: Mr Sandeep Dudi (For ALICE Collaboration) (Panjab University (IN))

QM22_poster_presentation_sandeep.pdf

18:10 Higher order transverse momentum fluctuations in heavy-ion collisions

In relativistic heavy ion collisions, the event-by-event mean transverse momentum ($\langle{p_{T}}\rangle$) fluctuations are sensitive to fluctuations in overlap area and reflect the nature of initial-state fluctuations in energy density. We present a cumulant framework to measure the event-by-event $\langle{p_{T}}\rangle$ fluctuations up-to $4^{\mathrm{th}}$ order which is then validated using HIJING, which is an independent source model. We observe a power law dependence for the measured cumulants of all orders as a function of charged particle multiplicity as expected from an independent source scenario. For a given $N_{\mathrm{ch}}$, the measured fluctuations show a larger magnitude for $pp$ collisions than for $p+$Pb, Pb+Pb and Xe+Xe collisions due to a bias in number of contributing sources for a given $N_{\mathrm{ch}}$. In addition, a suppression of short-range correlation was observed upon using two-subevent method in comparison to the standard method. This study provides a baseline for higher order $\langle{p_{T}}\rangle$ fluctuations arising from independent superposition of nucleon-nucleon collisions and consisting only of short-range correlations.

Speaker: Somadutta Bhatta (Stony Brook University (US))

QM2022_pTFlucHij_Som.pdf

18:14 Precision hydrodynamic predictions for particle production in isobar collisions at RHIC

The STAR collaboration has recently released measurements of soft particle production in Ru+Ru and Zr+Zr collisions [1]. Due to the isobar running mode and the huge statistics of collected events, such measurements are essentially devoid of experimental error, and permit us to perform precision tests of hydrodynamic models of the quark-gluon plasma (QGP).
In this contribution, we discuss hydrodynamic results for particle production in isobar collisions where we achieve the same precision reached in the experimental data. Our approach relies on a background-fluctuation splitting of the equations of hydrodynamics. In a given centrality class, and assuming boost invariance, we decompose the QGP as an event-averaged and azimuthally-isotropic background plus an event-by-event fluctation, $\text{QGP}(r,\phi)=\langle \text{QGP} \rangle (r) + \delta\text{QGP}(r,\phi)$. Linearizing the equations of hydrodynamics with respect to the fluctuation, we show that final particle spectra are determined by the isotropic background, with the fluctuation contributing only at next-to-next-to-leading order. Computing the evolution of $\langle \text{QGP} \rangle (r)$ requires solving 1+1D hydrodynamic equations, which can be done quickly for a large number of collision events.
We perform, thus, precision calculations of hadron production in isobar collisions by means of FluiduM [2], a solver for the 1+1D evolution of the QGP which implements 2nd order Israel-Stewart relativistic hydrodynamics as well as QGP particlization and resonance decays. We show predictions for particle spectra, yields and average transverse momenta of identified hadrons [3]. Looking at ratios of quantities between Ru+Ru and Zr+Zr systems, we find that they are insensitive to viscosities and other medium parameters. They are instead driven by initial-state effects, mainly originating from the larger neutron skin of 96Zr.
[1] STAR collaboration, https://arxiv.org/abs/2109.00131
[2] S. Floerchinger, E. Grossi, J. Lion, https://arxiv.org/abs/1811.01870
[3] F. Capellino, S. Floerchinger, G. Giacalone, E. Grossi, A. Kirchner, in preparation

Speaker: Andreas Kirchner

QM_Presentation.pdf

18:18 New results on $\phi$-pair production in proton-proton collisions at $\sqrt{s}$=7TeV with the ALICE detector

Recent measurements in high multiplicity proton-proton collisions have shown the emergence of several features that are reminiscent of QGP phenomenology, one of which is the enhanced production of strange and multi-strange hadrons. Strange hadron production represents a key probe to study QGP formation in hadronic collisions as well as to understand the mechanisms behind hadronisation.
In this context the $\phi$ meson is a very interesting candidate because of its structure, being a strangeness-neutral hadron that shows the characteristic features of strangeness enhancement, contrary to the expectations from of the strangeness-canonical implementation of thermal models.
A new analysis has been developed to measure the production of $\phi$-meson pairs in proton-proton collisions with the ALICE experiment at the LHC. This novel approach allows one to measure the second moment (variance) of the $\phi$-meson number distribution and therefore to gain insight into deeper details of the $\phi$-meson production statistics in minimum bias pp collisions and as a function of the final-state charged-particle multiplicity. The results are compared to the most commonly used Monte Carlo event generators and to theoretical predictions.

Speaker: Mr Nicola Rubini (Universita e INFN, Bologna (IT))

[QM][06-04-2022] Poster.pdf

18:30 → 19:30 Poster Session 2 T01

18:30 Analytic and Semi-Analytic Solutions for Color Glass Condensate in the Weak-Field Limit

The McLerran-Venugopalan Model (MV) of Color Glass Condensate for two colliding nuclei has been solved in the past using numerical methods and recursive analytic solution. On the other hand, in the weak field limit explicit analytic solutions in transverse momentum space have, in principle, been known for quite some time. Based on the latter we derive analytic expressions for gluon 2-point correlation functions $\langle F^{\mu\nu}(x^\alpha) F^{\kappa\lambda}(y^\beta)\rangle$ in nuclear collisions in the MV-model in the weak-field limit. In simple cases these expressions lead to solutions in closed analytic forms valid at all times. Our results allow for a straight forward evaluation of the time dependence of the energy momentum tensor, the angular momentum density and the momentum broadening coefficient $\hat q$ of the gluon fields in nuclear collisions in this limit.

Speakers: Stephen Robicheaux (Texas A&M University), Rainer Fries (Texas A&M University)

QM Poster.pdf

QM Poster.pptx

18:34 Probing the nuclear deformation effects in Au+Au and U+U collisions from STAR experiment

Nuclear deformation is an ubiqutous phenomenon for most atomic nuclei, reflecting collective motion induced by interaction between valance nucleons and shell structure. In most cases, the deformation has a quadrupole shape that is charactorized by overall strength $\beta_2$ and triaxiality $\gamma$ (prolate $\gamma=0$, obolate $\gamma=\pi/3$ and triaxial otherwise). Collisions of deformed nuclei lead to large shape and size fluctuations in the initial state geometry, which after collective expansion, lead to enhanced fluctuation of elliptic flow $v_2$ and event-by-event mean transverse momentum $[p_{\mathrm{T}}]$. Therefore, detailed study of the $v_2$, and $[p_{\mathrm{T}}]$ and correlations beween them can constrain the deformation parameters $(\beta_2,\gamma)$. A comparion of $(\beta_2,\gamma)$ with those measured from nuclear structure experiment could then be used to constrain the hydrodynamic responses of heavy-ion collisions. In this poster, we present results of $v_2$, $[p_{\mathrm{T}}]$ fluctuations and $v_2^2-[p_{\mathrm{T}}]$ correlation for harmonics $n=2,3,4$ in modestly-deformed $^{197}$Au+$^{197}$Au collisions at 200 GeV and highly-deformed $^{238}$U+$^{238}$U collisions at 193 GeV. Significant differences for mean, variance $c_2$ and skewness $c_3$ of $[p_{\mathrm{T}}]$ fluctuations, are observed between the two systems as a function of centrality. The $v_2^2-[p_{\mathrm{T}}]$ results remain positive over the full centrality in Au+Au collisions, while they change sign in 0-5\% central U+U collisions. The ratio of $v_2$ and $c_2$ between U+U and Au+Au in ultra-central collisions (UCC) are used to constrain the value of $\beta_2$, which leads to an estimate of $\beta_{2Au}\sim0.18$. On the other hand, the value of $\gamma$ can be constrained from the ratios of $v_2^2-[p_{\mathrm{T}}]$ and $c_3$ between U+U and Au+Au. The enhancement of $c_3$ and the suppression of $v_2^2-[p_{\mathrm{T}}]$ in UCC confirm that Uranum is prolate deformed with $\gamma\sim0$. Comparison with state-of-art model calculations is discussed.

Speaker: Jiangyong Jia (Stony Brook University (US))

JiangyongJia_PosterSTAR.pdf

Jiangyong_qm2022star.mp4

18:38 Initializing BSQ with Open-Source ICCING

While it is well known that there is a significant amount of conserved charges in the initial state of nuclear collisions, the production of these due to gluon splitting has yet to be thoroughly investigated. The ICCING (Initial Conserved Charges in Nuclear Geometry) algorithm reconstructs these quark distributions, providing conserved strange, baryon, and electric charges, by sampling a given model for the $g \rightarrow q\bar{q}$ splitting function over the initial energy density, which is valid at top collider energies, even when $\mu_B = 0$. The ICCING algorithm includes fluctuations in the gluon longitudinal momenta, a structure that supports the implementation of dynamical processes, and the c++ version is now open-source. A full analysis of parameter choices on the model has been done to quantify the effect these have on the underlying physics. We find there is a sustained difference across the different charges that indicates sensitivity to hot spot geometry.

Speaker: Patrick Carzon

Quark Matter Talk 2022.pdf

18:42 Probing gluon saturation via hard inelastic diffraction at the Electron-Ion Collider

We demonstrate that hard dijet production via inelastic diffraction is a promising channel for probing gluon saturation at the Electron-Ion Collider. Diffraction refers to a process in which there is a large rapidity gap between the produced jets and the nuclear target, while inelastic means that the two hard jets - a quark-antiquark pair generated by the decay of the virtual photon - are accompanied by a softer gluon jet, emitted by the quark or the antiquark.The recoil due to this gluon emission is responsible for transverse momentum imbalance between the 2 hard jets. This diffractive process can be described as the elastic scattering between an effective gluon-gluon dipole and the nucleus. The dominant contribution comes from the black disk limit, where the scattering is as strong as possible. Hence the dijet imbalance is of the order of the nuclear saturation momentum $Q_s$ evaluated at the rapidity gap. Measuring the imbalance of the dijet distribution for various rapidity gaps, one can study gluon saturation in the nuclear target. Integrating out the dijet imbalance, we obtain a collinear factorization where the initial condition for the DGLAP evolution is set by gluon saturation.

Speaker: Edmond Iancu (Université Paris-Saclay (FR))

18:46 Transverse momentum broadening in the glasma: real-time lattice simulations and the weak-field limit

Jets produced in heavy-ion collisions provide important information about the medium that they traverse. Their seeds, highly energetic partons that are created via hard scatterings during the collision, are affected by all different stages of the medium, including the pre-equilibrium precursor state of the quark-gluon plasma, which is known as the glasma. We will report on our numerical real-time lattice simulations of partons traversing the boost-invariant, nonperturbative glasma, which is generated at the early stages of heavy-ion collisions and calculate the effect for RHIC and LHC energies [1]. We observe that partons quickly accumulate transverse momentum up to the saturation momentum during the glasma stage. Moreover, we notice an anisotropy in transverse momentum broadening with larger broadening in the rapidity than the azimuthal direction. We compare our lattice simulations to a semi-analytic weak-field approximation [2], where we also find such an anisotropy and are able to link it to correlations among the color-electric and color-magnetic flux tubes in the initial state of the glasma.
[1] A. Ipp, D. I. Müller, D. Schuh, Phys. Lett. B 810 (2020), arXiv:2009.14206
[2] A. Ipp, D. I. Müller, D. Schuh, Phys. Rev. D 102 (2020), arXiv:2001.10001

Speaker: Daniel Schuh (Vienna University of Technology)

Transverse momentum broadening in the glasma - real-time lattice simulations and the weak-field limit.pdf

18:50 Initial State Anisotropies in Ultra-Central collisions of Deformed Nuclei

We use the boost-invariant IP-Glasma+MUSIC+UrQMD framework to isolate and study the effects of initial state geometry on observables. The study of spherically symmetric nuclei via heavy ion collisions cannot fully distinguish between the effects of collision centrality and initial state geometry on the hydrodynamic QGP or the hadron resonance gas. By using deformed collision systems such as $^{238}$U, one can create geometrically non-trivial initial states that help differentiate initial state and centrality effects. By focusing on ultra-central collisions, we show that emulation of ZDC binning can help select specific geometric sub-types of events solely based on final state observables. Selecting these events provides key insights into how these distinct anisotropies impact QGP flow, anisotropic flow coefficients, and transverse momentum distributions. Finally, we show that the QCD- and saturation-based IP-Glasma, coupled to relativistic hydrodynamics and hadronic cascade simulations, reproduces STAR data for U+U at $\sqrt{s_{NN}} = 193$ GeV.

Speaker: Nicolas Miro Fortier

Initial State Anisotropies in Ultra-Central collisions of Deformed Nuclei

18:54 Onset of non-conformal hydrodynamics and non-conformal hydrodynamic attractor in expanding ultra-relativistic plasmas

Hydrodynamic attractor behavior plays a key role in the pre-equilibrium evolution of expanding quark-gluon plasmas. Especially, the early-time hydrodynamic attractor allows for early-time initialization of hydrodynamic modelings, which strongly supports the applications of fluid dynamics to small colliding systems.

The hydrodynamic attractor has been well-established in conformal fluids, where initial fluctuations around the attractor evolution follow a power-law decay at early times. Nonetheless, in this talk, by solving 2nd order non-conformal fluid dynamics for out-of-equilibrium systems, we find that early-time attractor behavior is absent in non-conformal fluids. The absence of early-time attractor behavior can be proven to be generic in non-conformal fluids, as a consequence of the instability exhibited in the evolution of initial fluctuations, with a power-law growth. Although the mixing between the shear and the bulk modes can be tuned stable, to fully restore the early-time hydrodynamic attractor, and thus to be conceptually consistent with experimental observations, constraints on the second-order transport coefficient $\delta_{\Pi\Pi}$ can be deduced.

arXiv:2109.06658

Speaker: Li Yan (Fudan University)

18:58 Emergence of slow modes and the memory of initial momentum anisotropy in rapidly-expanding quark-gluon plasma

A crucial open question is why many models of expanding systems exhibit an apparent simplification in their description while gradients in the system are still large and hydrodynamics is not expected to apply. We discuss a new conceptual approach to understand the pre-equilibrium bulk evolution of a system in terms of a reduced set of slow modes. For concreteness we consider a kinetic theory describing a general expanding system with transverse flow and momentum space anisotropy. We find that these slow modes at early times give rise to far-from-equilibrium attractor behavior of moments of the distribution function. However, the slow modes are qualitatively distinct from hydrodynamic modes at early times, and only some of them evolve into hydrodynamic modes in the hydrodynamic limit. This framework suggests a general criterion for the presence of a simplified description even when gradients are large, if they are small compared to the energy gap between slow modes. This criterion can be satisfied in small systems, meaning that slow modes could be relevant for understanding flow-like correlations in small systems. We additionally find an attractor for the momentum space anisotropy that indicates the memory of initial anisotropy due to the presence of slow modes.

Speaker: Li Yan (Fudan University)

19:02 Towards a kinetic theory event generator for (heavy) ion collisions

Recently observed signs of collectivity in small systems has highlighted the need for a better understanding of equilibration in small and large collisions systems. In search of this, the QCD effective kinetic theory formulated by Arnold, Moore and Yaffe (AMY) [1] has emerged as a promising candidate. In order to bridge the gap between theory and experiments we develop a parton cascade that implements the AMY kinetic theory, i.e. solves the Boltzmann equation with the full AMY kernels (elastic scattering and splitting/merging processes) by explicitly simulating the evolution of a parton ensemble. It is constructed in a fully Lorentz invariant way by using a method pioneered in [2], which also underlies the parton cascade PCPC [3]. A complication arises from quantities like the screening mass, that enter the AMY kernels and are defined as integrals over the phase space densities. We develop a method for extracting these locally from the parton ensemble without the need for further information. We first study the thermal equilibrium and compare our results to other numerical solutions of the AMY theory. Given the complexity of the AMY kernels and the additional challenges of translating them into a Lorentz invariant parton cascade, this is a non-trivial step. The thermal equilibrium case will form the basis for a full event generator for collisions of light and heavy ions.

[1] Peter Brockway Arnold, Guy D. Moore, and Laurence G. Yaffe. “Effective kinetic theory for high temperature gauge theories”. JHEP 01 (2003), p. 030. doi:10.1088/1126-6708/2003/01/030. arXiv:hep-ph/0209353.

[2] G. Peter, D. Behrens, and C. C. Noack. “Poincare covariant particle dynamics. 1: Intranuclear cascade model”. Phys. Rev. C 49 (1994), pp. 3253–3265. doi:10.1103/PhysRevC.49.3253.

[3] V. Borchers et al. “A Poincare covariant parton cascade model for ultra-relativistic heavy ion reactions”. Phys. Rev. C 62 (2000), p. 064903. doi:10.1103/PhysRevC.62.064903. arXiv:hep-ph/0006038.

Speaker: Robin Törnkvist (Lund University)

Poster_QM22_Robin_Tornkvist.pdf

19:06 Progress towards full NLO accuracy and massive quarks in dipole picture fits to HERA data

Color Glass Condensate (CGC) effective field theory (EFT) at leading order describes well the Deep Inelastic Scattering (DIS) inclusive cross section data at small-x as measured by the HERA experiments [1-3]. Recently the inclusive DIS impact factors have been calculated in Next-to-Leading Order (NLO) accuracy in CGC EFT [4-6], and the soft gluon divergence present at NLO has been factorized successfully [7].

In this talk we discuss our recent work [8] on the first comparisons of the NLO DIS cross sections to HERA data. Fitting the HERA reduced cross section data determines a parametrization for the non-perturbative initial condition to the BK evolution. Since the available NLO DIS inclusive cross sections are calculated in the massless quark limit, we construct and fit a dataset of light-quark-only cross sections using an independent parametrization of HERA total and heavy quark data. We find an excellent description of the HERA data. As the NLO BK is computationally challenging [9], we compare a number of beyond-LO prescriptions that approximate the full NLO BK, including the recent evolution parametrized in target momentum fraction [10]. These beyond-LO evolution equations include important higher order contributions by resumming corrections enhanced by large transverse logarithms. The determined initial condition is a necessary input for all NLO calculations in the GCC framework.

To assess the impact of the full NLO BK equation on the fits, we study how well the fit parametrizations describe HERA data when NLO BK evolution is used. We find that the NLO BK is approximated quite well by the enhanced BK equations.

The NLO DIS cross sections for massive quarks are becoming available, the longitudinal case already having been published [11], and the transverse case will soon follow. These massive quark results will have immeadiate improvement on the fit analysis as they enable us to take into account the substantial charm and bottom contributions present in the HERA data. This talk will also discuss recent progress on including massive quarks in the fit.

[1] T. Lappi, H. Mäntysaari, Phys.Rev. D88 (2013) 114020, arXiv:1309.6963 [hep-ph]
[2] E. Iancu, J.D. Madrigal, A.H. Mueller, G. Soyez, D.N. Triantafyllopoulos, Phys.Lett. B750 (2015) 643-652, arXiv:1507.03651 [hep-ph]
[3] B. Ducloué, E. Iancu, G. Soyez, D.N. Triantafyllopoulos, Phys.Lett.B 803 (2020) 135305, arXiv:1912.09196 [hep-ph]
[4] G. Beuf, Phys.Rev. D94 (2016) no.5, 054016, arXiv:1606.00777 [hep-ph]
[5] G. Beuf, Phys.Rev. D96 (2017) no.7, 074033, arXiv:1708.06557 [hep-ph]
[6] H. Hänninen, T. Lappi, R. Paatelainen, Annals Phys. 393 (2018) 358-412, arXiv:1711.08207 [hep-ph]
[7] B. Ducloué, H. Hänninen, T. Lappi, Y. Zhu, Phys.Rev. D96 (2017) no.9, 094017, arXiv:1708.07328 [hep-ph]
[8] G. Beuf, H. Hänninen, T. Lappi, H. Mäntysaari, Phys.Rev. D102 (2020) 074028, arXiv:2007.01645 [hep-ph]
[9] T. Lappi, H. Mäntysaari, Phys.Rev. D91 (2015) no.7,074016, arXiv:1502.02400 [hep-ph]
[10] B. Ducloué, E. Iancu, A.H. Mueller, G. Soyez, D.N. Triantafyllopoulos, JHEP 04 (2019) 081, arXiv:1902.06637 [hep-ph]
[11] G. Beuf, T. Lappi, R. Paatelainen, Phys.Rev. D104 (2021), 056032, arXiv:2103.14549 [hep-ph]

Speaker: Henri Hänninen (University of Jyväskylä)

Hänninen_QM22_nlodis_poster.pdf

19:10 Observation and detailed measurements of nuclear deformations at STAR

Nuclear deformation is an ubiquitous phenomenon for most atomic nuclei, reflecting collective motion induced by interaction between valance nucleons and shell structure. In most cases, the deformation has a quadrupole shape that is characterized by overall strength $\beta_2$ and triaxiality $\gamma$, and/or a octuple shape $\beta_3$. Nuclear deformation enhances the fluctuations of harmonic flow and radial flow, and therefore, can be probed by $v_2$, $v_3$, and mean transverse momentum $[p_\mathrm{T}]$ fluctuations. Furthermore, deformation parameters can be constrained very precisely from ratios of flow measurements in two systems of isobar collisions. We present two sets of results:

i) The measurement of $v_2$, cumulants of $[p_\mathrm{T}]$, and Pearson correlation coefficient $\rho(v_2^2,[p_\mathrm{T}])$ in $^{197}$Au+$^{197}$Au and $^{238}$U+$^{238}$U collisions. Significant differences for variance and skewness of $[p_\mathrm{T}]$ fluctuations are observed between the two systems. The $\rho(v_2^2,[p_\mathrm{T}])$ values are positive over the full centrality in Au+Au collisions, while they change sign in 0-5\% central U+U collisions. The enhancement of $[p_\mathrm{T}]$-skewness and the suppression of $\rho(v_2^2,[p_\mathrm{T}])$ is consistent with large prolate deformation for Uranium.

ii) The measurement of $v_2$, $v_3$, and cumulants of $[p_\mathrm{T}]$ in $^{96}$Ru+$^{96}$Ru and $^{96}$Zr+$^{96}$Zr isobar collisions at 200 GeV. The ratios of these observables between the isobars show significant deviations from unity as a function of centrality. A comparison with hydrodynamic model simulations implies a large quadrupole deformation in Ru nucleus ($\beta_{2,\mathrm{Ru}}\sim0.16$) and a large octuple deformation in Zr nucleus ($\beta_{3,\mathrm{Zr}}\sim0.2$). The non-monotonic centrality dependence of ratios of $v_2$ and $[p_\mathrm{T}]$ fluctuations, especially for mid-central collisions also requires a difference in the surface diffuseness between Ru and Zr. Our results provide the first observation and quantitative extraction of the quadrupole and octuple deformation in Ru and Zr nuclei using heavy-ion collisions.

Speaker: chunjian zhang

QM2022_STAR_ChunjianZhang.pdf

19:14 Scaling and adiabaticity in a rapidly expanding gluon plasma

Scaling phenomena, and the associated self-similar evolution, play an important role in characterizing the off-equilibrium evolution of many physical systems. In far-from-equilibrium QCD, the distribution functions of quarks and gluons have been found to have self-similar evolution in terms of a scaling function and scaling exponents [1,2,3]. In this work [4] we use the collision kernel for small-angle QCD scatterings [5,6] as our working example to investigate the connections between self-similar evolution and the dominance of an effective ground state from very early times in the kinetic theory. We find that the adiabatic evolution of the ground state adequately describes the dynamics of the full system for a wide range of initial conditions and naturally explains the emergence of scaling for small-angle scattering. Furthermore, we show that the evolution of the time-dependent scaling exponents follows a renormalization group equation as a function of time and discuss the novelties of its fixed points. As a demonstration of the relevance of these results, we compute the “anomalous dimensions” of the scaling exponents and show that the correction to the BMSS fixed point matches the numerical EKT results of [3].

[1] J. Berges, K. Boguslavski, S. Schlichting and R. Venugopalan, “Turbulent thermalization process in heavy-ion collisions at ultrarelativistic energies,” Phys. Rev. D 89 (2014) 074011
[2] J. Berges, K. Boguslavski, S. Schlichting and R. Venugopalan, “Universal attractor in a highly occupied non-Abelian plasma,” Phys. Rev. D 89 (2014) 114007
[3] A. Mazeliauskas and J. Berges, “Prescaling and far-from-equilibrium hydrodynamics in the quark-gluon plasma,” Phys. Rev. Lett. 122 (2019) 122301
[4] J. Brewer, B. Scheihing-Hitschfeld, Y. Yin “Time-dependent scaling and adiabatic hydrodynamization in Bjorken-expanding gluon plasmas,” (in preparation)
[5] P.B. Arnold, G.D. Moore and L.G. Yaffe, “Effective kinetic theory for high temperature gauge theories,” JHEP 01 (2003) 030
[6] A.H. Mueller, “The Boltzmann equation for gluons at early times after a heavy ion collision,” Physics. Lett. B 475 (2000) 220

Speaker: Bruno Sebastian Scheihing Hitschfeld (Massachusetts Institute of Technology)

ScalingAdiabaticityPoster.pdf

19:18 First Results for the New Trento-3D Initial-Conditions Ansatz

Trento-3D is a parametric initial condition model, specifically designed for rapidly generating 3D energy distributions to initialize fully (3+1)-dimensional, event-by-event hydrodynamic simulations of ultrarelativistic heavy-ion collisions. Trento-3D builds upon the well-established T${}_\mathrm{R}$ENTo model [1], which samples nuclear configuration with subnucleonic structure and determines nucleon participation at the instant of collision. In Trento-3D, the total energy deposition is then divided among a central fireball near midrapidity and two fragmentation regions motivated by the limiting fragmentation hypothesis [2]. This extension, with a moderate number of parameters, allows for the faithful simulation of rapidity-dependent observables for a wide variety of collision systems over the gamut of ultrarelativistic energies.

In this presentation, we briefly describe the Trento-3D model and present first results of an ongoing, extensive calibration, demonstrating the capabilities of the model to describe various observables--such as yields, eccentricities, and derived quantities--as functions of rapidity. We explore the use of a (1+1)D linearized hydrodynamics model and the Cooper-Frye particlization procedure for conversion from 3D initial conditions to final-state, rapidity-dependent observables at significantly reduced computational cost. We validate these results vis-à-vis the MUSIC (3+1)D hydrodynamic code and offer predictions on future results and capabilities.

[1] J. S. Moreland, J. E. Bernhard, and S. A. Bass, Phys. Rev. C 92, 011901 (2015).
[2] J. Benecke et al., Phys. Rev. 188, 2159 (1969).

Speaker: Derek Soeder (Duke University)

Trento3D-QM2022-poster-Soeder.pdf

19:22 LPM effect and gluon saturation in dijet production at EIC

Large angle gluon radiations induced by multiple parton scatterings contribute to dijet production in deeply inelastic scattering off a large nucleus at the Electron- Ion Collider. Within the generalized high-twist approach to multiple parton scattering, the dijet cross section of eA at the leading order in perturbative QCD and large Bjorken momentum fraction xB can be expressed as a convolution of the multiple parton scattering amplitudes, quark and gluon TMD parton distribution function (PDF). We find that the calculated total dijet correlation for these mini-jets, is sensitive to the transverse momentum broadening in the quark TMD PDF at large x and saturation in the gluon TMD PDF at small x inside the nucleus. The contribution to dijet cross section from double scattering are power- suppressed and only become sizable at small transverse momentum. The correlation from double scattering is also found to increase with the dijet rapidity gap and have a quadratic nuclear-size dependence because of the Landau-Pomeranchuk- Migdal (LPM) interference in gluon emission induced by multiple scattering. Experimental measurements of such unique features in the dijet correlation can shed light on the LPM interference in strong interaction and gluon saturation in large nuclei.

Speaker: Yuan-Yuan Zhang (CUHK-SZ)

QM2022.pdf

19:26 Using local scaling of initial condition parameters to improve the system size dependence of transport model descriptions of nuclear collisions

A multi-phase transport (AMPT) model has been successful in reproducing a wide range of observables in relativistic heavy-ion collisions. However, certain key parameters need to have significantly different values for pp and central AA collisions for the model to well describe the yield and transverse momentum spectrum of the bulk matter.

In this work[1], we extensively study the system size dependence of nuclear collisions with a multiphase transport model. We scale two key initial condition parameters, the Lund string fragmentation parameter bL and the minijet transverse momentum cutoff p0, with local nuclear thickness functions from the two colliding nuclei. This allows the model to use the parameter values for pp collisions with the local nuclear scaling to describe the system size and centrality dependences of nuclear collisions self-consistently. In addition to providing good descriptions of pp collisions from 23.6 GeV to 13 TeV and reasonable descriptions of the centrality dependence of charged particle yields for Au+Au collisions from 7.7A to 200A GeV and Pb+Pb collisions at LHC energies, the improved model can now for the first time well describe the centrality dependence of the mean transverse momentum of charged particles. It works similarly well for smaller systems including pPb, Cu+Cu and Xe+Xe collisions.
[1] C. Zhang, L. Zheng, S.S. Shi, Z-W. Lin, Phys. Rev. C 104 (2021) 014908

Speaker: Chao Zhang (Central China Normal University)

18:30 → 19:30 Poster Session 2 T02

18:30 Vector resonances spin alignement as a probe of spin hydrodynamics

We argue that a detailed analysis of the spin aligement of vector mesons can serve as a probe of some aspects of spin dynamics in the vortical fluid for which there have been quite a few theoretical developments but relatively little phenomenology:
The degree of relaxation between vorticity and parton spin polarization, and the degree of coherence of the hadron wavefunction at freeze-out.
We show, using a coalescence model, that local spin density and vorticity impact the hadron wavefunction in different ways, and this is much more straight-forward to disentangle for a vector meson than for a spin 1/2 baryon.
We comment on the relevance of this issue for the current lack of consistency between experimental data on Lambda polarization and K*,phi spin alignment.

Based on https://arxiv.org/abs/2104.12941 and ongoing work.

Speaker: Mr Kayman Jhosef Carvalho Gonçalves (Unicamp)

Kayman_QuarkMatter 2022.pdf

18:34 Feasibility studies of $\Lambda$ transverse polarization in p+p interactions within NA61/SHINE at the CERN SPS

NA61/SHINE is a fixed-target experiment at the CERN SPS. Its spectrometer has unique properties including large particle acceptance and precise momentum measurement. These properties together with high statistics of collected proton-proton collisions at beam momentum 158 GeV/c allow analyzing the transverse polarization of $\Lambda$ hyperons produced in the primary vertex.
The opportunities for measurements of transverse polarization of $\Lambda$ hyperons in NA61/SHINE were studied based on Monte-Carlo simulations and the results will be presented. Especially, the biasing impact of magnetic field on polarization will be discussed in detail. The results suggest that the bias of $\Lambda$ polarization due to precession in the magnetic field is limited and less than biases due to limited detector acceptance.

Speaker: Mr Yehor Bondar (Jan Kochanowski University (PL))

Lambda_presentation_Bondar_QM2022_07_04_2022.pdf

18:38 Novel spin transport under chirality, vorticity and magnetic fields

Spin is an intrinsic quantum degree of freedom for various elementary particles that together make all of matter in our Universe. A salient feature of spin is its polarizability when subject to external conditions such as chirality, vorticity and magnetic fields. In recent years, there have been significant interests and considerable progress in understanding novel transport effects arising from the interplay between spin and these conditions in the environment of heavy ion collisions. Notable examples include e.g. the chiral magnetic effect as well as the global and local spin polarization of hyperons and vector mesons. In this talk, we will discuss some of the latest theoretical developments in light of the fresh experimental data. In the case of chiral magnetic effect, emphasis will be put on the interpretation of the STAR isobar experimental results based on the state-of-the-art phenomenological simulations. Regarding the spin polarization phenomenon, the implications of the latest STAR and HADES measurements in the few-GeV collision energy region will be analyzed and a possible construction of hydrodynamic framework with finite angular momentum will be presented.

Speaker: Jinfeng Liao

18:42 Chiral anomaly and small viscosity of Quark Gluon Plasma

Lattice calculations indicate that the chiral systems such as Quark Gluon Plasma posses domains of finite topological charge density. The scattering processes are significantly modified in these domains. In particular, the transport cross section acquires a resonance at the scattering angle proportional to the chiral conductivity. As a result, the transport coefficients such as the electrical conductivity and viscosity are suppressed at high temperatures. The phenomenological significance of this result is discussed.

Speaker: Kirill Tuchin

18:46 Dynamical evolution of magnetic fields in the pre-equilbrium quark-gluon plasmas

High-energy heavy-ion collisions generate an extremely strong magnetic field which plays a key role in a number of novel quantum phenomena in quark-gluon plasma (QGP), such as the chiral magnetic effect (CME). However, due to the complexity in theoretical modelings of the coupled electromagnetic fields and the QGP system, especially in the pre-equilibrium stages, the lifetime of the magnetic field in the QGP medium remains undetermined.

In this talk, we present a kinetic framework to study the dynamical decay of the magnetic field in the early stages of a weakly coupled QGP by solving the coupled Boltzmann and Maxwell equations. We find a universal separation of scales between the energy scale in the QGP medium and the strength of the magnetic field, irrespective of detailed interactions among quarks and gluons. The separation of scales allows for effective couplings between EM fields and the splittings among quarks and anti-quarks, which gives rise to the out-of-equilibrium induction effect. At late times, a magnetohydrodynamic description of the coupled system emerges. With respect to realistic collisions at RHIC and the LHC, we find that the residual strength of the magnetic field in the QGP satisfies a hierarchy relation: $m_q^2\ll |eB| \ll T^2$, when the system starts to evolve hydrodynamically. We also notice that the relative dominance from the electrical field and magnetic field can be reversed between RHIC and the LHC energies.

arXiv:2104.00831

Speaker: Li Yan (Fudan University)

18:50 Global polarization of \Lambda hyperons in Au+Au \sqrt{s_{NN}} = 7.2 GeV collisions with fi xed-target mode at RHIC-STAR experiment

Non-central heavy-ion collisions produce a large angular momentum that leads to vorticity of the created system.Due to the spin-orbit coupling, spin directions of particles are aligned with the orbital angular momentum of the system. Global polarization of $\Lambda$ and $\overline{\Lambda}$ hyperons has been measured in Au+Au collisions from $\sqrt{\rm{s_{NN}}}$ = 7.7 GeV to 5.02 TeV [1-3]. The STAR fixed target program provides an opportunity to extend such measurements at even lower energies.In this poster, differential measurements such as centrality, rapidity, and transverse momentum dependence of global polarization of $\Lambda$ hyperons in Au+Au collisions at $\sqrt{s_{\rm{NN}}}$ = 7.2 GeV with the fixed-target configuration are reported.

L.Adamczyk et al,(STAR) Nature 548 62 (2017).
J.Adam et al.(STAR), Phys. Rev. C 98 14910 (2018)
S.Acharya et al.(ALICE), Phys. Rev. C 101, 044611 (2020)

Speaker: Kosuke Okubo

QMposter_KosukeOkubo_ver7.pdf

18:54 Spin transport in quark gluon plasma

We present a theoretical framework to describe spin transport phenomena in quark-gluon plasma based on a hydrodynamical picture. We discuss how different power counting schemes lead to different spin hydrodynamic equations. We also discuss the role played by chiral anomaly in spin transport. Finally, the possible implications to hyperon spin polarization will also be discussed.

Speaker: Xu-Guang Huang

18:58 Chiral kinetic theory with collisions and its applications to the spin polarization

We have derived the chiral kinetic theory (CKT) with collisions in a QED matter. We have discussed the global equilibrium conditions in the presence of collisions. Then, we implement the CKT with effective collision term in the moment expansion and derive the off-equilibrium corrections to the axial currents and spin polarization vector.

Speakers: Mr Shuo Fang, Shi Pu, Di-Lun Yang (University of Crete)

19:02 Measurements of Global and Local Polarization of Hyperons in 200 GeV Isobar Collisions from STAR

In heavy-ion collisions, the observation of the global and local polarization of hyperons has revealed the existence of large vorticities perpendicular to reaction plane due to systems's orbital angular momentum and along beam direction due to collective velocity field, respectively. With the high-statistics data from isobar collisions of Ru+Ru and Zr+Zr at $\sqrt{s_{NN}}= 200$ GeV collected by the STAR experiment, we present differential measurements of global polarization for $\Lambda$/$\bar{\Lambda}$ and $\Xi^{\pm}$ as a function of centrality, $p_{T}$, and $\eta$.
These measurements allow us to study the possible magnetic field driven effects through the polarization difference between Ru+Ru and Zr+Zr, owing to a larger magnetic field in the former. Furthermore, the first measurements of $\Lambda$ hyperon local polarization along beam direction relative to the third order event plane as well as the second order event plane will be presented. A comparison on results from isobar and Au+Au collisions provides important new insights into the collision system size dependence of the vorticities in heavy-ion collisions.

Speaker: Xingrui Gou

QM2022 poster_Xingrui Gou.pdf

19:06 Differential study of Λ-hyperon polarization in a few-GeV regime within transport model approach

We present a systematic study of $\Lambda$ hyperon polarization in heavy-ion collisions at HADES energies within the framework of microscopic transport model UrQMD combined with the hadron-resonance gas statistical model. This study demands a complex analysis of the fireball evolution including time slices, extraction of temperature and baryonic chemical potentials, as well as freeze-out conditions of $\Lambda$ hyperons and study of the formation and space-time evolution of thermal vorticity. Two systems and four impact parameters are considered: Au+Au at $\sqrt{s_{NN}}=2.42$ GeV and Ag+Ag at $\sqrt{s_{NN}}=2.55$ GeV with $b = 3.0, 5.5, 7.5, 9.0$ fm. Rapidity and transverse momentum dependence of the polarization are obtained and show a good agreement with preliminary experimental data as well as centrality and energy dependence of global polarization.

Speaker: Mr Oleksandr Vitiuk (University of Wroclaw, Institute of Theoretical Physics)

QM_2022_Poster.pdf

19:10 Splitting of elliptic flow in non-central relativistic heavy-ion collisions

We predict a new effect due to the presence of the global vorticity in non-central relativistic heavy-ion collisions, namely a splitting of the elliptic flow parameter $v_2$ at non-zero rapidity. The size of the splitting is proposed as a new observable that can be used to constrain the initial vortical configuration of the produced QCD matter in experiments. The new findings are demonstrated by numerical calculations employing the parton cascade model, Boltzmann Approach of MultiParton Scatterings (BAMPS), for non-central Au + Au collisions at $\sqrt{s_{NN}} = 200 \ GeV$.

Speaker: Zhengyu Chen

19:14 Two- and three-particle nonflow effects on the CME measurements in Au+Au and isobar collisions at RHIC

QCD vacuum fluctuations can lead to chirality anomaly and parity violation in metastable local domains. This would result in a charge separation along the strong magnetic field produced in off-center relativistic heavy-ion collisons, a phenomenon called the chiral magnetic effect (CME). A widely used observable to search for the CME is the charge-dependent three-point correlator, $\Delta\gamma\equiv\langle \cos(\phi_{\alpha}+\phi_{\beta}-2\Psi_{\text{RP}})\rangle$, measured by the azimuthal angles of two particles relative to the reaction plane ($\Psi_{\text{RP}}$) or a third particle. The observable is, however, contaminated by a major elliptic flow ($v_{2}$) induced background. Recent measurements in Au+Au collisions at $\sqrt{s_{\text{NN}}} = 200 \text{ GeV}$ with respect to the spectator and participant planes, where the flow-induced background is eliminated, indicate a postive CME signal ($f_{\text{CME}}$) with a $\sim 2 \sigma$ significance [1]. The newly released isobar results by STAR, properly normalized by the observed multiplicity difference, are systematically above the naive baseline expectation of unity [2].

Nonflow contaminations in $v_{2}$ and three-particle correlations, however, can still affect the $f_{\text{CME}}$ measurements in Au+Au collisions and the isobar baseline to deviate from unity. In this talk, we estimate the effects of nonflow correlations on $f_{\text{CME}}$ [3] by using a multiphase transport (AMPT) and heavy ion jet interaction generator (HIJING) together with available experimental data on nonflow. It is found that the nonflow correlations can introduce a small (even possibly negative) contribution to $f_{\text{CME}}$, insufficient to explain the positive measurements by STAR. We further investigate the effects of nonflow correlations on the background baseline of the isobar data, and discuss the implication of our results to the CME search in isobar collisions.

[1] M. Abdallah et al. (STAR Collaboration), [arXiv:2106.09243 [nucl-ex]].
[2] M. Abdallah et al. (STAR Collaboration), [arXiv:2109.00131 [nucl-ex]].
[3] Y. Feng, J. Zhao, H. Li, H. j. Xu and F. Wang, [arXiv:2106.15595 [nucl-ex]].

Speaker: Dr Jie Zhao (Purdue University)

19:18 Jet-medium excitations induced Λ polarization as a gradient tomographic probe in heavy-ion collisions.

Recent measurements on $\Lambda$ hyperon's polarization suggest a strong correlation with the local fluid vorticity in hydrodynamic models. Jet-medium interactions induce a generic vortex ring structure of the fluid kinematic vorticity along the quenched jet axis. In this talk, we propose a novel ring observable R^J to capture such a ring excitation in the fluid's flow field by high-energy partons [1]. This observable $\mathcal{R}^{\hat{J}}$ shows a strong sensitivity to the fluid's shear viscosity. We verify our results with event-by-event hydrodynamic backgrounds. Furthermore, we expand our (3+1)D calculations by systematically studying the $\mathcal{R}^{\hat{J}}$'s dependence on the temporal-spatial size and magnitude of the deposited energy-momentum current. Finally, we quantify how the angular distribution of $\mathcal{R}^{\hat{J}}$ is correlated with the background flow field and can serve as a tomographic probe for the flow gradient field.

[1] W. M. Serenone, J. G. P. Barbon, D. D. Chinellato, M. A. Lisa, C. Shen, J. Takahashi, and G. Torrieri, "Lambda polarization from thermalized jet energy,'' Phys. Lett. B820, 136500 (2021)

Speaker: Willian Matioli Serenone (Universidade de São Paulo)

JetPolarizationTomographicProbeWillianMSerenone.pdf

19:22 Probing early-time longitudinal dynamics with the $\Lambda$ hyperon's spin polarization in relativistic heavy-ion collisions

We present a systematic study of the hyperon global polarization's sensitivity to the collision systems' initial longitudinal flow velocity, by extending our previous work [1] to event-by-event 3+1D hydrodynamic simulations. By explicitly imposing local energy-momentum conservation when mapping the initial collision geometry to macroscopic hydrodynamic fields, the evolution of systems' orbital angular momentum (OAM) and fluid vorticity are studied. We find that a simultaneous description of the $\Lambda$ hyperons' global polarization and the slope of pion's directed flow can strongly constrain the size of longitudinal flow at the beginning of hydrodynamic evolution. We constrain the initial longitudinal flow size and the fraction of orbital angular momentum in the produced QGP fluid as a function of collision energy with the STAR measurements in the RHIC Beam Energy Scan program. We examine the effects of the new thermal shear gradients on the hyperon's polarization. The gradients of $\mu_B / T$ can change the ordering between $\Lambda$'s and anti-$\Lambda$'s polarization. Finally, we investigate a variety of collision systems, including isobar, Cu+Au, Au+Au, and U+U, at the top RHIC energies. It enables us to study the system-size dependence of novel correlations among hyperons polarization and charge hadrons' averaged transverse momentum and anisotropic flow coefficients. These correlations are one of the key observables to verify the OAM-vorticity-polarization paradigm in heavy-ion collisions.

[1] S. Ryu, V. Jupic and C. Shen, "Probing early-time longitudinal dynamics with the $\Lambda$ hyperon's spin polarization in relativistic heavy-ion collisions", arXiv:2106.08125 [nucl-th]

Speaker: Dr Sangwook Ryu (Wayne State University)

poster_SRyu_QM2022.pdf

18:30 → 19:30 Poster Session 2 T03

18:30 Tackling the infamous $g^6$ term of the QCD pressure

The determination of the hot QCD pressure has a long history, and has --
due to its phenomenological relevance in cosmology, astrophysics and heavy-ion collisions — spawned a number of important theoretical advances in perturbative thermal field theory applicable to equilibrium thermodynamics.

In particular, the long-standing infrared problem that obstructs the perturbative series has been overcome by a systematic use of dimensionally reduced effective
theories, essentially mapping the problem of determining a full physical leading-order determination of the pressure to an extremely tough, but in principle doable, four-loop perturbative calculation in finite-temperature Yang-Mills theory.

We present advances in organizing this challenging calculation, by classifying the distinct contributions, filtering out a large fraction of sub-diagrams that exhibit a factorized structure, and push ahead systematic simplifications of the remaining core sum-integral structures taking into account systems of linear relations that originate from symmetry- as well as integration-by-parts-relations.
This will eventually allow us to gauge the grade of difficulty of a full determination of the physical leading-order QCD pressure. by analytic means.

Speaker: Pablo Navarrete (Universidad del Bio-Bio)

navarrete.pdf

18:34 Recent results in the extended linear sigma model: (axial)vector meson in-medium masses and finite volume effects via low momentum cutoff

Effective models play an important role in the investigation of the phase structure of the strongly interacting matter. Such an effective model is the (axial) vector meson extended linear sigma model (ELSM), which was already analyzed at finite temperature and gave predictions to thermodynamical quantities in good agreement with current lattice results. Recently, several advancements were done in the ELSM from which we plan to present two. Foremost, the (axial) vector in-medium masses, that were calculated by taking into account the (axial) vector meson-fermion interaction. Secondly, the effect of finite volume on the thermodynamics and the phase diagram, which was studied within the ELSM via a low momentum cutoff.

Speaker: Győző Kovács (Wigner RCP)

A0_format_Poster_KovacsGy.pdf

Poster_pres_QM22_KovacsGy.pdf

18:38 Quarkyonic Mean Field Theory: Quark-Nucleon duality and Ghosts

We discuss mean field theory of Quarkyonic matter at zero temperature. this field theoretical description of quarkyonic matter consisting of quark, nucleon and ghost fields. The ghosts are present to cancel over-counting of nucleon states that are Pauli blocked by the quark Fermi sea. We treat the nucleons with contact interactions in mean field approximation and the quarks without mean field vector interactions, but allow mass terms to be generated consistent with the addivive quark model for quark masses.

Speaker: Dr Saúl Fernando Hernández Ortiz (Institute for Nuclear Theory)

18:42 Exploring bulk QGP properties through high-pt theory and data

High-pt theory and data are traditionally used to explore high-pt parton interactions with QGP, while bulk QGP properties are commonly explored through low-pt data. However, rare high-pt light and heavy flavor can also be a powerful tool for inferring bulk QGP properties, as they are sensitive to global QGP parameters. A prerequisite for such QGP tomography is a proper description of high-pt parton-medium interactions, which we here achieve through our finite-temperature dynamical energy loss formalism, recently implemented within the DREENA numerical framework.

We here advocate a novel QGP tomography approach, where bulk QGP properties are jointly constrained by low and high-pt data. The approach can include arbitrary temperature profiles from bulk QGP simulations, which are implemented in the dynamical energy loss framework, and subsequently compared with high-pt data. We will show how this method can be used to i) constrain the early evolution of QGP, ii) study the temperature dependence of eta/s, iii) explore if QGP in small systems is consistent with high-pt data. This research demonstrates inherent interconnections between low and high-pt QGP physics, strongly supporting the utility of such a synergistic approach to QGP tomography.

Speaker: Dusan Zigic (Institute of Physics Belgrade)

QM2022_DZ_v2.pdf

18:46 Using active learning to constrain the size and location of the QCD critical point

The BEST collaboration’s equation of state (EoS) maps a 3D Ising model onto the lattice QCD EoS but contains 4 free parameters related to the size, location, and spread of the critical region across the QCD phase diagram. However, certain combinations of those 4 free parameters lead to acausal ($c_s^2>1$) or unstable ($\chi_2^B<0$) realizations of the EoS that should not be considered. Here, we use an active learning framework to rule out pathological EoS efficiently. We show that checking stability and causality for a small fraction of the available parameter combinations is sufficient to produce algorithms that perform with >96% accuracy across the entire parameter space. Though we work with a specific case, this approach can be generalized to any model containing a parameter space-class correspondence.

Speaker: Debora Mroczek (University of Illinois at Urbana-Champaign)

Mroczek_QM22.pdf

18:50 Shear viscosity at large baryon densities

The HADES experiment at GSI has recently provided data on the flow coefficients $v_1,...,v_4$ for protons in Au+Au reactions at $E_{\rm lab} = 1.23$ $A$GeV (or $\sqrt{s_\mathrm{NN}}=2.4$ GeV). This data allows to estimate the shear viscosity over entropy density ratio, $\eta/s$, at low energies via a coarse graining analysis of the UrQMD transport simulations of the flow harmonics in comparison to the experimental data. By this we can extract the space and time dependence of the $\eta/s$ ratio and provide for the first time an estimate of $\eta/s\approx0.65\pm0.15$ (or $(8\pm2)\,(4\pi)^{-1}$) for baryon rich matter at such low energies.

[1] T. Reichert, G. Inghirami and M. Bleicher, Phys.Lett.B 817 (2021) 136285

Speaker: Tom Reichert

Poster_QM22_Reichert.pdf

Presentation_QM22_Reichert.pdf

18:54 Exploring the dense QCD matter with spin hall effect

Spin Hall effect (SHE) is a generation of spin polarization for moving spin carriers in material under an external electric field. Recent theoretical analyses show that spin Hall current can be induced by the baryon chemical potential $\mu_{B}$ gradient[1], which plays role of the analogous electric field and becomes sizable at the beam scan energies of RHIC .

We study and predict this SHE signature for the hot and dense QCD matter created at RHIC-BES, using 3+1-d viscous hydrodynamics with AMPT initial condition. We propose to use the second Fourier coefficients of the local spin polarization of net Lambda hyperon as a sensitive probe to SHE. The resulting SHE observables show a qualitative difference in both the sign and beam energy dependence in calculations with and without SHE. Experimental observation of these distinct qualitative features would constitute strong evidence for SHE in the QCD matter under extreme density[2].

We also investigate the sensitivity of SHE signature to the initial Baryon stopping, QCD EoS at finite density and Baryon diffusive constant, and discuss the prospect of employing SHE to extract the properties of QCD matter at RHIC-BES energies[2].

Reference
[1] Y. Hidaka, S. Pu, and D.-L. Yang, Phys. Rev. D97, 016004 (2018), 1710.00278; Shuai Liu and Yi Yin, Phys. Rev. D 104 (2021) 5, 054043.
[2] B. Fu, L. -G. Pang, H. Song, Yi Yin in preparation

Speaker: Huichao Song

18:58 Diffusion matrix associated with the diffusion processes of multiple conserved charges in a hot and dense hadronic matter

Bulk matter produced in heavy ion collisions has multiple
conserved quantum numbers like baryon number, strangeness and electric charge. The diffusion process
of these charges can be described by a diffusion matrix describing the interdependence of diffusion of
different charges. The diffusion coefficient matrix is estimated here from the Boltzmann kinetic theory
for the hadronic phase within relaxation time approximation. In the derivation for the same,we impose the Landau-Lifshitz
conditions of fit. This leads to e.g. the diagonal diffusion coefficients
to be manifestly positive definite. The explicit calculations are performed
within the ambit of hadron resonance gas model with and without excluded volume corrections. It is seen that the off-diagonal
components can be significant to affect the charge diffusion in a fluid with
multiple conserved charges.The excluded volume correction effects is seen to be not significant in the estimation of the
elements of the diffusion matrix.

Speaker: Prof. Hiranmaya Mishra (Physical Research Laboratory, Ahmedabad)

19:02 Polarization effects at finite temperature and magnetic field

Understanding the impact of strong magnetic fields on QCD dynamics is important for an accurate description of non-central heavy-ion collisions and neutron stars. Lattice simulations found that a finite magnetic field affects the chiral dynamics of QCD in a non-trivial way. At low temperatures, the magnitude of chiral condensate increases with the magnetic field, the phenomenon known as the magnetic catalysis (MC). At finite temperature, the magnetic field leads to a faster melting of the condensate and thus the chiral transition temperature decreases with the magnetic field. This phenomenon is called the inverse magnetic catalysis (IMC). Lattice simulations suggest that IMC may be related to a competition between different effects in the magnetized QCD medium. The role of various interactions can be explored with the aid of effective models which makes them important tools, complementary to LQCD. While most chiral models are able to capture MC, they predict the opposite trend from LQCD calculations on the magnetic field dependence of the chiral transition temperature. In this talk we discuss the screening of a four-quark interaction by the ring diagram and its back-reaction on the quark gap equation in an effective chiral quark model. In consequence, a medium-dependent coupling is derived. This naturally reduces the chiral transition temperature in a class of chiral models and generates the inverse magnetic catalysis at finite temperatures and magnetic fields. These results provide a coherent description of inverse magnetic catalysis anchored to a reliable field-theoretical basis. We also demonstrate the important role of confining forces, via the Polyakov loop, in a positive feedback mechanism which reinforces the inverse magnetic catalysis. The contribution is based on the following works: arXiv:2107.05521, arXiv:2109.04439.

Speaker: Michal Szymanski (University of Wroclaw)

QM_2022_Szymanski.pdf

19:06 The upper right corner of the Columbia plot with staggered fermions

QCD with heavy dynamical quarks exhibits a first order thermal transition which is driven by the spontaneous breaking of the global $\mathcal{Z}_3$ center symmetry. Decreasing the quark masses weakens the transition until the corresponding latent heat vanishes at the critical mass.
We explore the heavy mass region with three flavors of staggered quarks and analyze the Polyakov loop and its moments in a finite volume scaling study. We calculate the heavy critical mass in the three flavor theory in the infinite volume limit.

Speaker: Ruben Kara

QM22_Ruben_Kara.pdf

19:10 Lattice QCD calculation of thermal photon rate

Thermal photons from the QGP provide important information about the interaction among the plasma constituents. The thermal photon production rate from a thermally equilibrated plasma is proportional to the transverse spectral function $\rho_{T}(k_0=|\vec k|,\vec k)$. One can calculate the photon production rate also from the difference between $\rho_{T}$ and $\rho_{L}$(longitudinal) correlator as $\rho_{L}$ vanishes on the photon point. The UV part of $\rho_{T}-\rho_{L}$ is not dominant and therefore the corresponding Euclidean correlator gets most of the contribution from the IR part of $\rho_{T}-\rho_{L}$. We calculate the continuum extrapolated T-L correlator non-perturbatively on the lattice at 1.1$T_c$ and 1.5$T_c$ for a gluonic medium. We will present the extraction of spectral function from this Euclidean correlator using a hydrodynamic inspired model in combination with the Backus-Gilbert method, which allows us to estimate the photon production rate at these temperatures.

Speaker: Dibyendu Bala

Dibyendu_QM22_poster.pdf

19:14 Ambiguities in the hadro-chemical freeze-out of Au+Au collisions at SIS18 energies and how to resolve them

The thermal fit to preliminary HADES data of Au+Au collisions at $\sqrt{s_{_{NN}}}=2.4$ GeV shows two degenerate solutions at $T\approx 50$ MeV and $T\approx 70$ MeV. The analysis of the same particle yields in a transport simulation of the UrQMD model yields the same features, i.e. two distinct temperatures for the chemical freeze-out. While both solutions yield the same number of hadrons after resonance decays, the feeddown contribution is very different for both cases. This highlights that two systems with different chemical composition can yield the same multiplicities after resonance decays. The nature of these two minima is further investigated by studying the time-dependent particle yields and extracted thermodynamic properties of the UrQMD model. It is confirmed, that the evolution of the high temperature solution resembles cooling and expansion of a hot and dense fireball. The low temperature solution displays an unphysical evolution: heating and compression of matter with a decrease of entropy. These results imply that the thermal model analysis of systems produced in low energy nuclear collisions is ambiguous but can be interpreted by taking also the time evolution and resonance contributions into account.

[1] Anton Motornenko, Jan Steinheimer, Volodymyr Vovchenko, Reinhard Stock, Horst Stoecker, Phys.Lett.B 822 (2021) 136703, arXiv:2104.06036 [hep-ph]

Speaker: Dr Anton Motornenko (Frankfurt Institute for Advanced Studies)

19:18 Fermion spectral function in a highly occupied non-Abelian plasma

Motivated by the quark-gluon plasma, we develop a simulation method to obtain the spectral function of fermions non-perturbatively in a non-Abelian gauge theory with large gluon occupation numbers. We apply our method to a non-Abelian plasma close to a far-from-equilibrium self-similar regime, and find very good agreement with perturbative hard loop (HTL) calculations for medium-induced masses, dispersion relations and quasiparticle residues. For the first time, we extract the full momentum dependence of the damping rate of fermionic collective excitations, and compare our results to recent non-perturbative extractions of gluonic spectral functions.

Speaker: Kirill Boguslavski (Vienna University of Technology (AT))

BACKUP slides

Boguslavski_QM2022.pdf

19:22 Baryon number fluctuations and search for the CEP of QCD

Fluctuations of conserved charges, in particular the baryon number fluctuations, are thought of as experimental observables which are sensitive to the QCD critical end point (CEP), where the singular part of thermodynamic functions plays a dominant role. Indeed, in the past several years significant fluctuation measurements have been performed in the Beam Energy Scan program at RHIC, and an amount of relevant data are available. However, how can the experimental data be used to extract the information of CEP, e.g., the existence or location of CEP in the QCD phase diagram? This question could be answered through the combination of efforts from both experiments and theories.

In this talk, first of all, I would like to discuss recent progress in the theoretical studies of baryon number fluctuations in the functional approach [1]. We compute the baryon number fluctuations up to tenth order at finite temperature and density. We show that a non-monotonic energy dependence of baryon number fluctuations can arise in the non-critical crossover region of the phase diagram. Our results compare well with recent experimental measurements of the kurtosis and the sixth-order cumulant of the net-proton distribution from the STAR collaboration. Then, I would like to discuss the influence of different locations of CEP in the QCD phase diagram on the collision-energy dependence of the observed cumulants, which could help us to constrain the regime of CEP based on the experimental data [2], especially in the region of interest, muB~(450-650) MeV, where the location of CEP is predicted by recent first-principle functional QCD [3].

Reference:
[1] Wei-jie Fu, Xiaofeng Luo, Jan M. Pawlowski, Fabian Rennecke, Rui Wen, Shi Yin, Phys. Rev. D 104, 094047, 2021 (DOI: https://doi.org/10.1103/PhysRevD.104.094047, Editors’ Suggestion), arXiv: 2101.06035 [hep-ph].
[2] Wei-jie Fu, Xiaofeng Luo, Jan M. Pawlowski, Fabian Rennecke, Rui Wen, Shi Yin, in preparation.
[3] Wei-jie Fu, Jan M. Pawlowski, Fabian Rennecke, Phys. Rev. D 101, 054032, 2020, arXiv: 1909.02991 [hep-ph]; Fei Gao and Jan M. Pawlowski, Phys.Lett.B 820, 136584, 2021, arXiv: 2010.13705 [hep-ph].

Speaker: Prof. Wei-jie Fu (Dalian University of Technology)

18:30 → 19:30 Poster Session 2 T04_1

18:30 Anisotropy of the QGP droplet explored through high-$p_{\perp}$ data

Through analytical arguments, numerical calculations and comparison with experimental data, we show that the ratio of high-$p_{\perp}$ observables $v_2/(1-R_{AA})$ reaches a well-defined saturation value at high $p_{\perp}$, which depends on the spatial anisotropy of quark-gluon plasma formed in ultrarelativistic heavy ion collisions. By using our recently developed DREENA framework, which can accommodate any temperature profile, we calculate this ratio for various temperature evolutions and demonstrate that it is robustly related to the time-averaged anisotropy of the evolving QGP, as seen by jets. With the future reduction of experimental errors, our method will provide a way to constrain an important bulk property of the medium – spatial anisotropy of QGP – directly from high-$p_{\perp}$ experimental data.

Speaker: Mr Stefan Stojku

QM2022_presentation_StojkuStefan(1).pdf

18:34 In-medium propagation in flowing matter

The theory of jet quenching has been steadily evolving in order to incorporate the effects of having a longitudinally evolving plasma. On the other hand, the transverse dynamics of the medium evolution has been largely ignored due to the fact that its effects are suppressed by powers of the energy of the probe. Recently, a calculation of the effects of medium motion on transverse momentum broadening and medium-induced radiation was completed within the opacity expansion. In this talk we show how to generalize this result to the case of multiple scatterings by explicitly calculating the correction due to medium motion to the in-medium propagator of a fast moving particle.

Speaker: Fabio Dominguez (Universidade de Santiago de Compostela)

18:38 Jet and photon polarization as a measure of QGP anisotropy

The quark-gluon plasma formed in heavy-ion collisions has a large momentum anisotropy, especially during early stages of collisions. For jet partons this leads to momentum broadening which is not isotropic in the parton's transverse plane. In this talk we discuss such anisotropic momentum broadening of jets in detail and evaluate how it changes the radiation of hard gluons, and gives rise to a net polarization of jets. We first present a microscopic calculation of momentum broadening of a jet parton. This calculation assumes an anisotropic distribution of quarks and gluons in the medium and is done in the hard thermal loops formalism with careful treatment of plasma instabilities [1]. A main result is increased magnetic screening at lower transverse momenta which reduces momentum broadening substantially [2]. In the second half of this talk, we calculate in detail the rate for a jet parton to radiate a gluon when undergoing anisotropic momentum broadening. Using the harmonic oscillator approximation, we show that the radiated gluon is polarized and that after successive branching this leads to net polarization of jets in heavy-ion collisions. We present a similar analysis for the polarization of photons. Finally, we discuss briefly how the anisotropy of the quark-gluon plasma could be measured directly from jet and photon polarization.

[1] S. Hauksson, S. Jeon, C. Gale, Phys. Rev. C 103, 064904 (2021), arXiv:2012.03640

[2] S. Hauksson, S. Jeon, C. Gale, arXiv:2109.04575

Speaker: Sigtryggur Hauksson (McGill University)

presentation_QM2022_hauksson.pdf

18:42 Transport of hard probes through glasma

Hard probes, due to their large momenta (or masses), are produced only through hard interactions with large momentum transfer at the earliest phase of a heavy-ion collision. They then propagate through the evolving medium probing QCD matter at different energy scales and different phases of the fireball evolution. During this propagation heavy quarks and high-$p_T$ partons lose a substantial fraction of their initial energy. While machanisms of the energy losses are quite well understood in equilibrated QGP, the influence of pre-equilibrium phases on transport of hard probes has been only fragmentarily explored.

In the talk, I will demonstrate that the glasma can indeed play an important role in transport of hard probes. I will discuss the transverse momentum broadening coefficient $\hat q$ and collisional energy loss $dE/dx$ of hard probes moving through the glasma. First, I will present the methodology that is used to compute the transport coefficients: the Fokker-Planck equation, whose collision terms determine $\hat q$ and $dE/dx$, and the proper time expansion that describes the temporal evolution of the glasma. The correlators of chromodynamic fields that determine the Fokker-Planck collision terms are computed to fifth order. The transport coefficients are shown to be strongly dependent on time and orientation of the probe's velocity. They are large, $\hat q$ is of the order of a few ${\rm GeV^2/fm}$ and $dE/dx \sim 1~{\rm GeV/fm}$, in the domain of validity of the proper time expansion and their values depend on the probe's velocity ${\bf v}$ and the parameters: coupling constant $g$, saturation momentum $Q_s$ (UV scale), and IR regulator $m$, fixed by the confinement scale. I will show how $\hat q$ depends on all these quantities. Different regularization procedures will be also analysed and shown to lead to similar results for $\hat q$. Finally, I will discuss limitations of the whole our approach, such as the validity of the proper-time expansion and constraints resulting from the Fokker-Planck equation.

Speaker: Alina Czajka (National Centre for Nuclear Research)

poster-quark-matter-czajka.pdf

18:46 Deciphering jet quenching effects with novel reclustering tools

Jet substructure applied to a heavy-ion environment can provide valuable information about jet-medium interaction. This class of observables, mostly inherited from proton-proton collisions, is still far from being fully exploited as a tool for QGP tomography. So far, measurements are restricted to quantities that provide an average quantification of the medium parameters, missing the critical fast time evolution experienced by the QGP. In this talk, we use a novel clustering tool based on the concept of a parton formation time [1] to select samples with enhanced sensitivity to jet quenching effects. We show that we can overcome the effects of jet selection biases that make the current interpretation of jet results challenging. Moreover, we further explore the link of the jet clustering scale to the QGP time structure by using the information of the first and second steps of the jet clustering sequence. The output allows to select jets with the potential to provide time-differential measurements of the created medium.

[1] L. Apolinário, A. Cordeiro, K. Zapp, Eur.Phys.J.C 81 (2021) 6, 561

Speaker: Pablo Guerrero Rodríguez (University of Jyväskylä)

Rodríguez_poster.pdf

18:50 Impact of the initial stages on the medium-induced radiation spectrum

Recently, we developed a framework to evaluate the single-inclusive gluon emission spectrum without further assumptions, including full resummation of multiple scatterings. In this talk, we compare this formalism with well-known analytical approximations, determining in that way their validity in all kinematical regions and showing to what extent accounting for multiple scatterings is crucial to properly describe in-medium gluon emissions. We then obtain the radiation spectrum when the medium is produced with a time delay with respect to the hard process in which the probe was originated. We analyze the impact on phenomenological studies of the extra medium-induced radiation due to the propagation of the hard parton before the formation of the medium. This kind of analysis becomes imperative given the recently proven sensitivity of some jet quenching observables to the initial stages after the collision.

Speaker: MARCOS GONZALEZ MARTINEZ (IGFAE - Universidade de Santiago de Compostela (ES))

GonzalezMartinezMarcos_QM2022.pdf

18:54 Computationally efficient description of QGP medium response jet-by-jet

The injection of energy and momentum from a jet into the QGP generates a wake, which leads to soft and semi-hard particle creation correlated with the jet direction after the QGP hadronizes. As several jet quenching studies have shown, this medium response phenomenon plays a crucial role in our understanding of many jet structure and substructure observables. Nevertheless, a detailed account of the phenomenological consequences of those wakes is still lacking, partly because of the computational complexity of current techniques used to describe their properties. In this work we present a computationally efficient description of the event-by-event, jet-by-jet, determination of the properties of the hadrons coming from QGP wakes. By making use of a single set of universal solutions obtained within linearized hydrodynamics on top of a Bjorken flow, and performing the adequate set of scalings, translations, rotations and boosts, we are able to match the results obtained (with much greater computational cost) using 3+1D hydrodynamics. The transparency and simplicity of our approach allows us to identify the key variables affecting the shape of the measurable hadron distributions, such as the evolution time of the wakes between its formation and freeze-out and the local QGP flow velocity, both its magnitude and its direction relative to that of the wake, at the location on the freeze-out surface where the wake freezes out. With this knowledge, we will discuss how to design observables that can measure these effects experimentally.

Speaker: Dr Xiaojun Yao (Massachusetts Institute of Technology)

QM22 jet wake.pdf

18:58 A system of evolution equations for scattering and medium induced radiation of quarks and gluons

Partonic jets, i.e. highly energetic collimated sprays of strongly interacting particles, provide an excellent means to study the hot and dense medium
of a quark gluon plasma (QGP), since the highly energetic jet particles interact with the medium particles, however do not thermalize.
Jet particles in the medium undergo both processes of scatterings off medium particles as well as emission processes induced by the medium.
Medium induced radiation processes are created over time scales long enough that simultaneously multiple scattering processes off medium particle can
occur, which gives rise to interference effects. The resulting spectra were first described by Baier, Dokshitzer, Mueller, Peigné, Schiff and
independently Zakharov (BDMPS-Z). A resulting evolution equation for the fragmentation functions of gluons in jets was found by Blaizot,
Dominguez, Iancu, and Mehtar-Tani (BDIM). We extend this approach to a system of evolution equations for the in-medium evolution of both kinds of
jet partons, quarks and gluons, via coherent medium induced radiations as well as scatterings off medium particles[1].
The system of equations is solved numerically by a Monte-Carlo algorithm that also allows to obtain results for individual jets that propagate in the
medium[2]. Thus, we are able to study the in-medium angular jet-broadening of quark and gluon jets, where we find that the latter are less collimated
than the former.

References:
[1] E. Blanco, K. Kutak, W. Płaczek, M. Rohrmoser, K. Tywoniuk, arxiv: 2109.05918 [hep-ph]
[2] M. Rohrmoser, arxiv: 2111.00323 [hep-ph]

Speaker: Martin Rohrmoser (IFJ-PAN Krakow)

posterqmrohrmoser.pdf

19:02 Scaling properties of jets in high-energy proton-proton collisions

Measurements of jet profiles in high-energy collisions are sensitive probes of QCD parton splitting and showering. Precise understanding of the jet structures are essential for setting the baseline not only for nuclear modification of jets in heavy-ion collisions, but also for possible semi-soft cold QCD effects such as multi-parton interactions (MPI) that may modify jets in high-multiplicity proton-proton collisions. We analyzed the jet radial profiles in simulations, and defined a multiplicity-dependent characteristic jet size that is universal in a broad range of model classes regardless of parton distributions and the presence or absence of MPI and color-reconnection [1].
In this contribution we demonstrate that the radial jet profiles in proton-proton collisions exhibit scaling properties with charged-hadron event multiplicity in the full experimentally accessible transverse-momentum range. Based on this we propose that the scaling behavior stems from fundamental statistical properties of jet fragmentation [2]. We also study the multiplicity distributions of events with hard jets and show that the charged-hadron multiplicity distributions scale with jet momentum. This suggests that the Koba--Nielsen--Olesen (KNO) scaling holds within a jet. The in-jet scaling is fulfilled without MPI, but breaks down in case of its presence without color reconnection. Our findings imply that KNO scaling is violated by parton shower or MPI in higher-energy collisions [3]. Besides these results, newest findings on the flavor-dependence of scaling properties will also be presented.

[1] Z.V., R.V., G.G.B., Adv. High Energy Phys. 2019 (2019), 6731362, arXiv:1805.03101.
[2] A.G., R.V., G. Papp, G.G.B., in Gribov-90 Memorial Volume: Algebraic Methods in QFT (2021), arXiv:2008.08500.
[3] R.V., A.G., G.G.B., Phys. Rev. D 103, L051503 (2021), arXiv:2012.01132.

Speaker: Robert Vertesi (Wigner Research Centre for Physics (Wigner RCP) (HU))

vertesi-jetstruct-QM22.pdf

19:06 Intra-jet asymmetry in heavy-ion collisions

The interaction between the jet and QGP fluid will deflect particles associated with the jet from their initial orientation. Such deflection will depend on the energy of the jet constitutes and the velocity of the flow. The soft particles suffering stronger deflection will drift towards the direction of the flowing medium, away from the center of the jet cone where the hard particles are located, leading to an angular intra-jet asymmetry of particle distribution coupled with flow inside the jet. In this work, we first calculate the angular distribution of particles with different pT inside the jet and compare it with the experimental data to obtain the average effect of the jet-flow coupling. We further explore the intra-jet asymmetry in longitudinal and transverse directions and study their dependence on jet path length and fluid viscosity. Together with gamma-jet asymmetry, we can use the transverse intra-jet asymmetry to identify the initial production position of the gamma-jet. We further compare the difference between dijet and gamma-jet to investigate the effect of the diffusion wake induced by the back-side jet. With the implementation of a mirror-subtraction method, we observe a clear rapidity ordering of particles with different pT, which shows a clear jet-flow coupling in the longitudinal direction. Furthermore, we find that the longitudinal intra-jet asymmetry can provide solid proof of the jet-induced diffusion wake in heavy-ion collisions.

Speaker: Tan Luo (IGFAE)

19:10 The information content of jet quenching and machine learning assisted observable design

We employ machine learning techniques to identify important features that distinguish jets produced in heavy-ion collisions from jets produced in proton-proton collisions [1]. We formulate the problem using binary classification and focus on leveraging machine learning in ways that inform theoretical calculations of jet modification: (i) we quantify the information content in terms of Infrared Collinear (IRC)-safety and in terms of hard vs. soft emissions, (ii) we identify optimally discriminating observables that are analytically tractable, and (iii) we assess the information loss due to the heavy-ion underlying event and background subtraction algorithms. We illustrate our methodology using Monte Carlo event generators, where we find that important information about jet quenching is contained not only in hard splittings but also in soft emissions and IRC-unsafe physics inside the jet. This information appears to be significantly reduced by the presence of the underlying event. We discuss the implications of this for the prospect of using jet quenching to extract properties of the QGP. Since the training labels are exactly known, this methodology can be used directly on experimental data without reliance on modeling. We outline a proposal for how such an experimental analysis can be carried out, and how it can guide future measurements.

[1] Lai, Mulligan, Ploskon, Ringer [arXiv 2111.14589]

Speaker: James Mulligan (University of California, Berkeley (US))

Mulligan_QM_Poster.pdf

19:14 Medium modification of jet-shape observables in PbPb collisions at $\sqrt{s_{NN}}$=2.76 TeV using EPOS and JEWEL event generators

Study of modification of the substructure of charged jets due to the presence of medium provides insight into the energy loss mechanisms of jets in the medium. We have studied the in-medium modification of two jet-shape observables, differential jet-shape ($\rho(r)$) and angularity ($g$) in PbPb collisions at $\sqrt{s_{NN}}$=2.76 TeV using JEWEL and EPOS event generators. While JEWEL (recoil OFF) does not explain the distribution of lost energy at higher radii with respect to the jet-axis, EPOS-3 explains the effect quite well. This study can provide important new insights on mechanisms regarding the modeling of the medium and hard-soft interactions in heavy ion collisions.

Speaker: Mr Sumit Kumar Saha (VECC)

19:18 Reconstructed Jets and Jet Substructure in 200 GeV p+p and p+Au Collisions with PHENIX

Measurements of reconstructed jets and jet substructure offer opportunities to study fragmentation in a nuclear environment. Jet measurements in $p$+A collisions can provide crucial information for understanding the relationship between hard and soft processes in small collision systems. However, at RHIC this promise is complicated by the low jet energies and lack of hadronic calorimetry in the current experiments. In this talk, we report new results with reconstructed jets, including substructure measurements applying jet grooming techniques, in $p$+$p$ and $p$+Au collisions at a center of mass energy of 200 GeV using the PHENIX experiment. Jets are reconstructed from charged particle tracks and electromagnetic calorimeter clusters with the anti-kT algorithm. The measurements are unfolded for detector response using a multi-dimensional algorithm to extract both the cross section and jet substructure quantities in a self-consistent fashion. We report jet cross sections and substructure observables in 200 GeV $p$+$p$ collisions as well as the nuclear modification factor and substructure as a function of centrality for $p$+Au collisions. These measurements have implications for developing a quantitative understanding the modification of jets in heavier systems, such as Cu+Au and Au+Au collisions at RHIC.

Speaker: John Lajoie (Iowa State University)

Lajoie_PHENIX_Jets_QM22_Poster_Rev3.pdf

19:22 Dynamically groomed jet radius in heavy-ion collisions

Jet substructure is a powerful tool to probe the perturbative regime of jet evolution in proton-proton and heavy-ion collisions. Over the past few years, a wide variety of substructure observables have been proposed in order to understand specific aspects of jet dynamics in a quark-gluon plasma (QGP).

In this talk, based on [1], we will explore the ability of such an observable, called Dynamical Grooming [2], to pin down the properties of the QGP. In particular, we will present the computation via analytic resummation techniques and Monte-Carlo simulations, of the opening angle $\theta_g$ of the hardest splitting in the jet as defined by Dynamical Grooming. This calculation, grounded in perturbative QCD, accounts for the factorization in time between vacuum-like and medium-induced processes in the double logarithmic approximation.
Our main result is that the dominating scale in the $\theta_g$-distribution is the decoherence angle $\theta_c$ which characterizes the resolution power of the medium to propagating color probes, which makes this observable particularly interesting to measure $\theta_c$ experimentally. To that aim, we will highlight a suitable combination of the Dynamical Grooming condition and the jet radius that leads to a pQCD dominated observable with a very small sensitivity to medium response.

Refs:
[1] P. Caucal, A. Soto-Ontoso and A. Takacs, arXiv:2111.14768
[2] Y. Mehtar-Tani, A. Soto-Ontoso and K. Tywoniuk, arXiv:1911.00375

Speaker: Dr Paul Caucal (Brookhaven National Laboratory)

QM2022-caucal.pdf

18:30 → 19:30 Poster Session 2 T04_2

18:30 Jets as sources of acoustic probes for flowing quark-gluon plasma

We explore the thermalization of energetic partons in quark-gluon plasma medium by analyzing the medium response effect on jet substructure observables. In high-energy heavy-ion collisions, jets become more populated by soft partons through the induced radiation and scatterings in the medium. Consequently, the energies of some soft jet partons reach the typical energy of the medium constituents, and they thermalize in the medium. The thermalized component of the jet propagates hydrodynamically and emits hadrons correlated with the jet core. Those hadrons carry crucial information about the jet thermalization process and are measured as a part of clustered jets.

In this talk, we systematically study the medium response by performing simulations with two distinctive prescriptions: propagation of recoils in partonic scatterings based on a weakly-coupled description and its combination with hydrodynamical medium response assuming the partial thermalization of jets [1]. Furthermore, by studying the angular structure of jets with different flow configurations of the medium, we demonstrate that the background medium flow and the analysis for the large-angle region $r>1$ are essential to extract the details of the in-medium jet thermalization.

[1] Y. Tachibana, C. Shen and A. Majumder, ``Bulk medium evolution has considerable effects on jet observables!,'' arXiv:2001.08321 [nucl-th].

Speaker: Yasuki Tachibana (Akita International University)

tachibana_QM_poster.pdf

18:34 Constraining the color-charge dependence of parton-medium interactions with new photon-tagged jet measurements in ATLAS

Quarks and gluons traversing a QCD medium may lose energy through a variety of processes, including medium-induced radiation sensitive to their QCD color factor.
The color-charge dependence of the parton-medium interaction is a critical component in all jet energy loss models and generally in heavy-ion physics phenomenology. In this talk, the color charge dependence of jet-medium interactions is quantitatively studied
with a new measurement that compares the nuclear modification factor for photon-tagged jets to that for inclusive jets. These measurements exploit the known difference in the fraction of quark-/gluon-initiated jets with and without the photon tag, allowing for a precise extraction of the color-charge sensitivity. Additionally, the possible impact of the color charge factor on
jet-medium interactions is studied in photon-tagged multi-jet systems where the most likely configuration of jets is one quark and one gluon initiated. Comparisons with state-of-the-art theoretical models are shown.

Speaker: Yeonju Go (University of Colorado Boulder (US))

QM22_photonTaggedJetRAA_ATLAS_YeonjuGo_v3.pdf

18:38 Jet quenching studies with new jet substructure and suppression measurements in ATLAS

Measuring the jet substructure in heavy-ion collisions provides exciting new opportunities to study detailed aspects of the dynamics of jet quenching in the hot and dense QCD medium created
in these collisions. In this talk, we present new ATLAS measurements of jet substructure performed using various jet (de)clustering and grooming techniques. Measurements of inclusive jet suppression ($R_{AA}$) in heavy-ion collisions are presented for the first time as a function of the jet substructure using both nominal ($R=0.4$) and large-radius ($R=1.0$) jets in Pb+Pb and
$pp$ collisions at $\sqrt{s_{NN}} = 5.02$ TeV. The jet substructure is characterized using the Soft-Drop grooming procedure in order to identify subjets corresponding to the hardest parton
splitting in the jet. The dynamics of jet quenching is measured and presented as a function of the transverse momentum scale ($\sqrt{d_{12}}$) and the angle of the hardest splitting in the jet.
Novel reconstruction methods are utilized to combine and optimize information from the tracker and calorimeter and build jet constituents for the first time in heavy-ion collisions. These new
measurements test the sensitivity of jet suppression in the QCD medium to its substructure and the emergence of a critical angle for the onset of color decoherence.

Speaker: Wenkai Zou (Columbia University (US))

poster_2022qm.pdf

18:42 Jet $R_{AA}$ and $v_n$ for PbPb 5.02 TeV with JEWEL+v-USPhydro

The Quark-Gluon Plasma, a state of matter characterized by its extreme energy density and temperature generated in heavy-ion collision experiments, is expected to modify hard-scattered partons traveling through it and, consequently, the jets they produce. Analyses regarding jets may recover information about the medium and its partonic energy-loss mechanism. This work applies the Monte Carlo event generators JEWEL and PYTHIA for the simulation of observables comparable to current experimental research, focusing on the impact of a realistic description of the medium, provided by the state-of-the-art (2+1)D v-USPhydro code and $\rm T_RENTo$ initial conditions, in the azimuthal distribution and energy modification of jets.

We present the jet nuclear modification factor $R_{AA}$ and anisotropic flow coefficients $v_{n=2,3,4}$ for multiple models, centralities and jet radii $R$. The $R_{AA}$ simulated presents good agreement with experimental data for central collisions only. The evolution of the results in terms of centrality and $R$ indicates a possibility of better understanding of medium response in the JEWEL framework. The realistic hydrodynamics models behave differently to JEWEL's longitudinal-only expansion, mainly in the circumstances where less quenching is expected. The correlation between the jet azimuthal distribution and those generated by soft particles resulted from the realistic medium profiles enables the event-by-event calculation of higher-order jet anisotropic flow coefficients that can be compared to experimental measurements. The simulations show a transverse momentum-dependent elliptic flow $v_2$ and a positive triangular flow $v_3$.

Speaker: Leonardo Barreto De Oliveira Campos (Universidade de Sao Paulo (BR))

qm2022_Leonardo_v2.pdf

18:46 Unified picture of jet fragmentation from early to late times

We revisit the picture of jets propagating in the quark-gluon plasma. In addition to vacuum radiation, related to the high initial virtuality of a jet, jet particles scatter on the medium constituents resulting in induced emissions. Analytical approaches to resumming these interactions have traditionally dealt separately with multiple, soft [1,2], or rare, hard scatterings [3,4]. A full resummation has so far only been available using numerical methods [5,6,7]. Our goal is to achieve full analytical control of the relevant scales and map out the dominant physical processes in the full phase space. To this aim, we extend existing resummation schemes for the medium-induced spectrum [4,8,9] to the Bethe-Heitler regime, to cover the whole phase space from early to late times, and from hard splittings to emission below the thermal scale. Based on the separation of scales, a space-time picture naturally emerges: at early times, jets start to build from both vacuum and rare, hard scattering induced emissions. At a later stage, determined by a resolution criterion, these emissions initiate a turbulent cascade [10] that rapidly degrades their energy down to, and including the Bethe-Heitler regime. We quantify the impact of such an improved picture, compared to the current state of the art factorization that includes only soft scatterings [11], by both analytical and numerical methods for the jet fragmentation function. Our work serves to improve our understanding of jet quenching from small to large systems and for future upgrades of Monte Carlo generators.

[1] R. Baier, Y. L. Dokshitzer, A. H. Mueller, S. Peigne, and D. Schiff, Nucl. Phys. B 483 (1997) 291–320.
[2] B. Zakharov, JETP Lett. 63 (1996) 952–957.
[3] M. Gyulassy, P. Levai, and I. Vitev, Nucl. Phys. B 594 (2001) 371–419.
[4] U. A. Wiedemann, Nucl. Phys. B 588 (2000) 303–344.
[5] S. Caron-Huot and C. Gale, Phys. Rev. C82 (2010) 064902.
[6] C. Andres, L. Apolinario, and F. Dominguez, JHEP 07 (2020) 114.
[7] S. Schlichting and I. Soudi, arXiv:2111.13731.
[8] Y. Mehtar-Tani, JHEP 07 (2019) 057.
[9] J. a. Barata and Y. Mehtar-Tani, JHEP 10 (2020) 176.
[10] J.-P. Blaizot, E. Iancu, and Y. Mehtar-Tani, Phys. Rev. Lett. 111 (2013) 052001.
[11] P. Caucal, E. Iancu, A. H. Mueller, and G. Soyez, Phys. Rev. Lett. 120 (2018) 232001.

Speaker: Adam Takacs (University of Bergen)

Adam_Takacs_QM2022.pdf

18:50 Jets and leading hadrons at high virtuality

Jet modification is a multi-stage (multi-scale) process: an initial high virtuality stage gives way to a lower virtuality transport stage for high energy partons, and a strongly coupled phase for lower energy parts of the shower. The transition from the high virtuality medium-modified DGLAP stage takes place when the virtuality reaches the medium induced scale 𝑞̂ 𝜏, where 𝜏 is the lifetime of a given parton. A recent outstanding dispute has arisen on the role of energy loss in the high virtuality phase, and its contribution to jet observables [1,2]. In this presentation, we demonstrate that in a realistic, dynamically evolving medium, the effect of the higher virtuality stage on leading hadron suppression is comparable or dominant to the lower virtuality stages. This is due to the fact that, for most jets, 𝑞̂ scales with entropy density, and thus falls faster than the virtuality of the leading partons. As a result, the combined lifetime of partons with virtuality larger than the medium induced scale is sufficiently long that these partons scatter with the plasma multiple times before reaching the medium scale.

To systematically address this, we derive the complete next-to-leading twist single gluon emission contribution. Going beyond previous work, we include higher-twist contributions from both the modulus of the amplitude and the phase in interference terms. We also include all momentum fraction (𝑦) suppressed contributions from quark scattering prior to emission. This calculation [3] allows us to successfully address the issues raised in the work by Aurenche et al. [4,5]. Based on this formalism, a Monte-Carlo event generator (MATTER+LBT+hydrodynamics within the JETSCAPE v0 framework) is further developed for simulating parton showers through the QGP. We demonstrate that while the medium-modified DGLAP process dominates jet observables at high 𝑝𝑇, such as the leading hadrons, the subsequent near-on-shell transport process dominates at low 𝑝𝑇. Only by combining these two stages can we naturally obtain a simultaneously good description of the nuclear modification factors of hadrons and jets [6].

References:
1. Caucal, P., Iancu, E., Mueller, A. H., & Soyez, G. (2018). "Vacuum like jet fragmentation in a dense qcd medium." Physical review letters, 120(23), 232001.
2. Casalderrey-Solana, J., Mehtar-Tani, Y., Salgado, C. A., & Tywoniuk, K. (2013). "New picture of jet quenching dictated by color coherence." Physics Letters B, 725(4-5), 357-360.
3. C. Sirimanna, S. Cao and A. Majumder, "Final State Gluon Emission in Deep-Inelastic Scattering at Next-to-Leading Twist," e-Print: 2108.05329 [hep-ph].
4. Aurenche, P., Zakharov, B. G., & Zaraket, H. (2008). "Failure of the collinear expansion in the calculation of the induced gluon emission." JETP letters, 87(11), 605-610.
5. Aurenche, P., Zakharov, B. G., & Zaraket, H. (2008). "Comment on``Success of collinear expansion in the calculation of induced gluon emission''." arXiv preprint arXiv:0806.0160.
6. S. Cao, C. Sirimanna, and A. Majumder, "The medium modification of high-virtuality partons," e-Print: 2101.03681 [hep-ph].

Speaker: Shanshan Cao (Shandong University)

QM2022 poster.pdf

18:54 The onset of light and heavy meson quenching in small systems

Ultra-relativistic collisions of small nuclear systems can shed light on the onset of QGP formation. So far, proton-nucleus (p+A) and deuteron-nucleus (d+A) collisions have been used to study the emergence of the smallest QGP droplets, producing the puzzling results that the non-zero elliptic flow of hadrons at intermediate transverse momenta is not correlated to the suppression of their spectra. An oxygen-oxygen (O+O) run at the LHC will provide a unique opportunity to investigate in detail the onset of jet quenching, differentiate between models of energy loss, and flesh out the differences between light parton and heavy quark dynamics over small length scales. We present the first calculation of heavy meson suppression and elliptic flow at moderate and high $p_T$ in O+O reactions from medium-induced scaling violations in QCD and compare to the corresponding light hadron observables. The theoretical approach that we employ goes beyond traditional energy loss phenomenology and bridges the gap between high energy and nuclear physics. The nuclear modification is found to be surprisingly large up to transverse momenta of order 100 GeV. We finally discuss the implications of our results, should they be confirmed by the future LHC measurements, for the interpretation of the p+A data.

Speaker: Weiyao Ke (Los Alamos National Laboratory)

Poster-1.pdf

18:58 Unsupervised machine learning of heavy-ion underlying event subtraction from only ion data

Central and mid-peripheral heavy-ion collisions produce a significant underlying event superimposed on the hard scattering of interest. So far, traditional underlying event mitigation algorithms introduced for heavy-ion often impose limitations in their applicability. The jet typically has to be clustered in the presence of the underlying event. Observables like the energy have to be corrected for the underlying event offset afterward. Furthermore, while machine learning methods can have improved performance for underlying event mitigation, no such approach has been proposed that can be trained without seeing jets from clean hard scatterings — trained in-situ on experimental ion (e.g., PbPb) data only, independent of any Monte Carlo or detector modeling. Overcoming this constraint is particularly crucial for heavy-ion jet measurements, as any reliance on Monte Carlo inserts a theory uncertainty in modeling heavy-ion jets. For the first time, an algorithm is presented that removes all these limitations: (a) the algorithm preserves the complete event information, (b) it retains only positive transverse momentum particles without the need for negative or counterbalancing particles, (c) it uses machine learning to optimize the signal-to-noise ratio, and (d) it can be trained in-situ using only ion data. Specifically, it overcomes the lack of ground truth clean events using self-supervised machine learning. The performance of the algorithm is demonstrated using jet kinematics, substructure, and axes observables, and compared to existing underlying event mitigation methods. The implication of this algorithm for future and novel measurements is discussed.

Speaker: Yue Shi Lai (Lawrence Berkeley National Lab. (US))

qm-20220406.pdf

19:02 Disentangling Jet Modification in Jet Simulations and in Z+Jet Data

The selection of jets in heavy-ion collisions based on their quenched $p_T$ is known to bias towards jets that lost little energy. We illustrate this explicitly in a simplified Monte Carlo study in which it is possible to identify the same jet before and after quenching. We find that selecting a sample of jets based on their quenched $p_T$ yields a sample of jets whose fractional energy loss is substantially smaller than would have been the case if it were possible to select a sample of jets based upon their $p_T$ before quenching. This has substantial impacts on jet structure and substructure observables, and dramatically reduces the observable consequences of medium response in a sample of jets selected based upon their quenched $p_T$, since the jets that are selected are those that lost little energy and hence created little medium response. We then show that the same qualitative effect can be seen in Z+jet events, and that selecting jets in such events based on either the jet $p_T$ or the boson $p_T$ provides an experimentally-accessible way to quantify the role of selection biases in jet observables. Selecting such jets based on the Z boson $p_T$ removes the bias towards jets that lost little energy, making the observable impact of medium response apparent.

Speaker: Quinn Brodsky

QuarkMatter2022-V2.pdf

19:06 Probing hadronization and jet quenching with flavor correlations of leading particles in jets

We study nonperturbative flavor correlations between pairs of leading and next- to-leading charged hadrons within jets and their modifications in the presence of a QCD medium. A charge correlation ratio observable $r_{c}$, generalized from the balance function 1 which distinguishes between same-sign and opposite-sign charged pairs, is introduced. This observable $r_c$ is studied as a function of different kinematic variables in different colliding particle species using different Monte Carlo event generators. We demonstrate the feasibility of such measurements at the Electron Ion Collider in the context of hadronization studies 2. This will provide new tests of hadronization models and hopefully lead to improved quantitative understanding of nonperturbative QCD dynamics. Also, with robust understanding of hadronization using $r_c$, we examine its medium modification which will shed light on the jet quenching mechanisms in hadronization and in-medium jet evolution.

References
1 S. A. Bass, P. Danielewicz and S. Pratt, Clocking hadronization in relativistic heavy ion collisions with balance functions, Phys. Rev. Lett. 85 (2000), 2689-2692
2 Y. T. Chien, A. Deshpande, M. M. Mondal and G. Sterman, Probing hadronization with flavor correlations of leading particles in jets, arXiv:2109.15318 [hep-ph]

Speakers: Dr M. M. Mondal (CFNS, Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY), Dr Y.-T. Chien (Physics and Astronomy Department, Georgia State University, Atlanta, GA)

19:10 Expected jet energy resolution and underlying event fluctuations in the sPHENIX detector

The sPHENIX detector at the Relativistic Heavy Ion Collider is designed to measure high momentum probes of the quark-gluon plasma such as jets. Jet measurements in heavy-ion collisions require subtraction of the large underlying event consisting of low momentum particles produced from the QGP medium. While subtraction techniques can remove the average size of the background, localized fluctuations can result in an over- or under-subtraction of the underlying event. This effect leads to an increase in the jet energy resolution, which can be understood through the size of the underlying event fluctuations. This poster presents a study of the expected jet energy resolution from both detector effects and underlying event fluctuations using simulations of the sPHENIX detector.

Speaker: Virginia Bailey (Univ. Illinois at Urbana Champaign (US))

sPHENIX_QM22_jets_poster_vbailey_v2.pdf

19:14 Resummation in the presence of energy loss: jet observables and substructure

Experimental data on a wide range of jet observables measured in heavy-ion collisions provide strong constraints on the underlying medium dynamics and are addressed by state-of-the-art Monte Carlo models. However, so far there has been little theoretical guidance on the systematics of medium modifications on such diverse quantities as the inclusive jet spectrum, the intra-jet fragmentation functions and (groomed) substructure observables. We put forward a versatile and systematically improvable resummation framework for calculating jet observables that accounts for radiative and elastic energy loss [1,2,3]. This relies only on the separation of jet scales and medium scales that lead to the factorization of hard, early vacuum emissions and soft, medium-induced branchings [1,4]. As three concrete examples, we discuss the a) inclusive jet spectrum for different radii [2], b) the distribution of microjets/hadrons inside large jets, and c) the jet mass in heavy-ion collisions. Tuning the medium parameters to the nuclear modification factor of inclusive jets simultaneously provides a baseline modification of the fragmentation function as well as the shift and distortion of the jet mass peak. This program grants, on one hand, a powerful framework to consistently study modifications of jets across a wide range of observables (with a grip on their resilience to non-perturbative effects) and, on the other hand, furnishes access to the value of the coupling between individual jet color charges with the underlying medium.

[1] Y. Mehtar-Tani and K. Tywoniuk, "Sudakov suppression of jets in QCD media," Phys.Rev.D 98 (2018) 051501 [arXiv:1707.07361 [hep-ph]].

[2] Y. Mehtar-Tani, D. Pablos and K. Tywoniuk, "Cone size dependence of jet suppression in heavy-ion collisions," (accepted for publication in Phys.Rev.Lett.) [arXiv:2101.01742 [hep-ph]].

[3] Y. Mehtar-Tani and K. Tywoniuk, in preparation

[4] P. Caucal, E. Iancu, A. H. Mueller and G. Soyez, "Vacuum-like jet fragmentation in a dense QCD medium," Phys.Rev.Lett. 120 (2018) 232001 [arXiv:1801.09703 [hep-ph]].

Speaker: Konrad Tywoniuk (University of Bergen (NO))

19:18 Jet momentum broadening in heavy ion collisions from effective kinetic theory

We study jet momentum broadening in heavy ion collisions at initial stages. We focus on the jet quenching parameter $\hat q$, which we extract using effective kinetic theory. We obtain its non-equilibrium properties during the initial stages in a Bjorken-expanding plasma with non-thermal anisotropic initial conditions.

Speaker: Florian Lindenbauer (TU Wien)

Quark_Matter_2022_Lindenbauer_Poster.pdf

19:22 Gluon radiation in the fragmentation region

I will discuss recent work that aims to understand the initial state of the fragmentation region of heavy ion collisions using an entirely classical framework that incorporates the phenomenon of gluon saturation. The first step in the program, recently carried out by Kajantie, McLerran, and Paatelainen, is to study the gluon radiation from a classical point particle struck by a sheet of colored glass. We show how to improve their results for the gluon radiation distribution to take into account the recoil of the struck "quark". It is then a straight-forward matter to extend this result to the case of nucleus-nucleus collisions.

Speaker: Mawande Lushozi (University of Washington)

18:30 → 19:30 Poster Session 2 T05 / T13

18:30 Measurement of $\omega$ mesons in pp collisions at the LHC with ALICE

Measurements of neutral mesons in small collision systems can serve as a baseline to understand modifications in heavy-ion collisions, where a QGP is formed.
These measurements can also be used to test pQCD predictions and to constrain fragmentation functions as well as parton distribution functions.
Furthermore, a good understanding of particle production enables the measurement of direct photons yields, where a large background of decay photons is present and needs to be accounted for.

In this poster the invariant cross section of the $\omega$-meson production in pp collisions at a center of mass energy of $\sqrt{s}=13\,$TeV, as measured by ALICE via its dominant decay channel $\omega \rightarrow \pi^+ \pi^- \pi^0$, will be presented.
While charged pions can directly be measured by the ALICE central barrel trackers, neutral pions are reconstructed using their decay channel into two photons. This reconstruction is realized with several complementary methods making use of various calorimeters and the ALICE central barrel trackers. The combined result covers an unprecedented $p_T$ range with small statistical and systematic uncertainties.

Speaker: Jens Robert Luhder (Westfaelische Wilhelms-Universitaet Muenster (DE))

QuarkMatter_2022_JensLuehder_OmegaIn13TeV.pdf

18:34 QCD matter properties in small LHC collision systems

Increasingly many studies have involved the use of Bayesian statistics in estimating the transport properties of quark-gluon plasma through hydrodynamic calculations. So far, most of these studies have obtained their estimates in Pb-Pb collision systems at varying center-of -mass energies. It has been since learned that the inclusion of multiple collision configurations and high harmonic observables is crucial in obtaining results of high precision [1, 2].

In this talk, we constrain the QCD matter properties further by adding collision systems of varying sizes, such as Xe-Xe and pPb collision data measured by ALICE at LHC. In addition, we utilize the Bayesian analysis to constrain the Xe nuclear deformity, which provides an additional constraint to the initial conditions. We also present predictions for the O-O collision system using results obtained by constraints from this study.

[1] J. E. Parkkila, A. Onnerstad, and D. J. Kim, Phys. Rev. C 104, 054904, Bayesian estimation of the specific shear and bulk viscosity of the quark-gluon plasma with additional flow harmonic observables.
[2] J. E. Parkkila, A. Onnerstad, S. F. Taghavi, C. Mordasini, A. Bilandzic and D. J. Kim, arXiv:2111.08145, New constraints for QCD matter from improved Bayesian parameter estimation in heavy-ion collisions at LHC.

Speaker: Jasper Parkkila (University of Jyvaskyla (FI))

18:38 JEWEL for Small Systems

Despite almost a decade of work, the absence of jet-modification in small systems is yet to be satisfactorily explained. Although JEWEL (Jet Evolution With Energy Loss) is a Monte Carlo (MC) generator designed to study the evolution of jets with a variety of background media, the publicly available versions are not able to simulate small systems. We present the first results using an adaptation of JEWEL that is appropriate for small colliding systems such as $ pPb $, $ dAu $, and very peripheral $ AA $: Building on the radially symmetric hydrodynamic interface developed by Korinna Zapp, we allow for (2+1)D generality, thereby allowing for the first-ever MC jet data that is faithful to the underlying dynamics of small colliding systems. We present comparisons with experimental data for jet observables in a multitude of colliding systems, as well as predictions for $ OO $, using a variety of publicly available hydrodynamical simulations.

Speaker: Dr Isobel Kolbe (Institute for Nuclear Theory)

JEWEL for small systems.pdf

18:42 Disentangling the gluon Bremsstrahlung effects from the underlying event in high-multiplicity pp collisions

Recently, the so-called relative transverse activity classifier, $R_T$, has been proposed as a tool to disentangle the particle production originated from the soft and hard QCD processes in proton-proton (pp) collisions. $R_T$ is a useful quantity to study particle production in events with exceptionally large or small activity in the transverse region with respect to the event-averaged mean. Contrary to the expectations, the preliminary results of the ALICE Collaboration indicate that, e.g., the proton-to-pion ratio does not exhibit the characteristic enhancement at intermediate $p_T$ in events with large \rt with respect to minimum-bias pp collisions. In this work, we investigate the origin of this effect using the Pythia 8 and Herwig 7 Monte Carlo event generators. The effect is a consequence of a selection bias attributed to wide-angle gluon emissions which creates jets that populate the transverse region. Therefore, we propose a modified version of $R_T$ in order to suppress its sensitivity to hard gluon Bremsstrahlung, and enhance the sensitivity to soft Multiparton Interactions (MPI). This approach could be useful in order to study the particle production in the jet-like region as a function of MPI. The implementation of these ideas in data will provide more insight into the production mechanisms of hadrons in high-multiplicity pp collisions, and its connection with heavy-ion phenomena.

Speaker: Gyula Bencedi (Wigner Research Centre for Physics (Wigner RCP) (HU))

Bencedi_QM22.pdf

18:46 Title: Net-Proton directed flow in 19 GeV Au+Au collisions

Directed flow of particles is an important feature seen in heavy-ion collisions and is a sensitive probe of the equation of state (EoS) of the matter produced in the collisions. Model calculations have also predicted that directed flow could be a sensitive probe of the softening of EOS associated with a first order phase transition. Directed flow of protons and anti-protons are of particular interest as they offer sensitivity to both the contributions from the transported quarks and also the medium generated component from the produced quarks. We will present measurements of the directed flow of protons and antiprotons from 19.6 GeV Au+Au collisions, using high statistics BES-II data from STAR. The new results have significantly reduced uncertainties and allow the study of how the two contributions vary over different centrality and transverse momentum regions.

Speaker: Edwin Duckworth

QM2022_poster_presentation_duckworth_2022-04-05.pdf

18:50 A Simple Geometrical Model for p+p and Nucleus-nucleus Collisions, and its Comparison to Experimental Data on Small and Large Systems

The aim of this work was to investigate the properties of a new, simple model of the nucleus+nucleus collisions at high energy, and its applicability to the CERN SPS energy regime. The model was uniquely based on the system's geometry and local energy and momentum conservation in the quark gluon plasma produced in the reaction.

We studied Pb+Pb collisions at $\sqrt{s_{NN}}$ = 17.3 GeV and 8.8 GeV, and obtained a surprisingly good agreement between our model and the experimental data (rapidity spectra) collected by the NA49 experiment at CERN SPS as a function of centrality. Furthermore, we applied this model to the nucleon+nucleon (N+N) collisions by taking into account the changes in the overall energy balance between the Pb+Pb and N+N system (baryon stopping, strangeness enhancement, and isospin content). The obtained results again display a very good agreement between the model prediction and experimental rapidity distributions in proton+proton collisions measured by the NA49 and NA61/SHINE Collaborations. This shows that our approach is applicable also for small systems in the CERN SPS energy range.

A discussion of future applications of this model to small and large systems at LHC energies will be included in this poster.

References:

Ł. Rozpłochowski, Acta Phys. Polon. Supp. 13 (2020) 893, and references therein

Speaker: Lukasz Rozplochowski (Institute of Nuclear Physics Polish Academy of Sciences)

QM2022_poster_Rozpłochowski.pdf

18:54 Performance of high-p$_{T}$ electrons in proton-lead collisions in the ATLAS experiment

Electrons constitute an essential component of final states from the leptonic decay channels of W and Z bosons. Their reconstruction and identification are especially challenging in heavy-ion collisions due to high detector occupancy. Therefore, the evaluation of electron performance is crucial for precision measurements of properties of quark-gluon plasma produced in heavy-ion collisions at the LHC energies. The poster will present the measurement of electron reconstruction, identification, isolation, and trigger efficiencies in proton-lead collisions collected at 8.16 TeV in 2016. The tag and probe method will be used to derive electron efficiencies in data and MC simulation independently, and the results will be compared.

Speaker: Patrycja Anna Potepa (AGH University of Science and Technology (PL))

QM2022-Potępa.pdf

18:58 From QCD to QED and back: medium effects in neutrino-nucleus and electron-nucleus scattering from Glauber photon interactions

Effective field theories of QCD, such as soft collinear effective theory with Glauber gluons, have led to important advances in understanding of many-body nuclear effects. We provide first applications to QED processes. We study the exchange of photons between charged particles and the nuclear medium for (anti)neutrino-, electron-, and muon-induced reactions
inside a large nucleus. We provide analytical expressions for the distortion of (anti)neutrino-nucleus and charged lepton-nucleus cross sections and estimate the QED-medium effects on the example of elastic lepton-nucleon reactions in kinematics of modern and future experiments. We find new percent-level effects, which were never accounted for in
either (anti)neutrino-nucleus or electron-nucleus scattering. Our treatment can be easily generalized to photon emission and exchanges in the QGP.

Speaker: Oleksandr Tomalak

QM_2022_Tomalak.pdf

19:02 Intermediate mass dileptons as a speedometer of QGP equilibration

We compute the spectrum of dileptons produced by the quark-gluon plasma in the intermediate mass range 1<M<5 GeV using state-of-the-art QCD kinetic theory. Our calculation takes into account the anisotropy of the quark and gluon momentum distributions at early times, as well as the underpopulation of quarks relative to gluons. The resulting dilepton spectrum satisfies approximate transverse mass scaling, up to a modest breaking which results from the momentum anisotropy. We discuss the dependence of dilepton production on system size, centrality, and collision energy, on the basis of dimensional arguments. Our main result is that the viscosity to entropy ratio, which controls the equilibration time of the quark-gluon plasma, can be extracted from the inverse slope of the transverse mass spectrum. We evaluate the background from the Drell-Yan process and argue that future detector developments can suppress the additional background from semileptonic decays of heavy flavors.

Speaker: Maurice Louis Coquet (Université Paris-Saclay (FR))

QM2022_COQUET.pdf

19:06 Examination of the universal behavior of the $\eta$-to-$\pi^0$ ratio in heavy-ion collisions

We demonstrate that the $p_T$ dependence of the $\eta/\pi^0$ ratio at mid rapidity is universal within a few percent for high energy $p$+$p$, $p$+A and $d$+A collisions, over a broad range of collision energies. The $\eta/\pi^0$ ratio increases with $p_T$ up to 4 to 5 GeV/$c$ where it saturates at a nearly constant value of 0.487$\pm$0.024. Above $p_T = 5$ GeV/$c$ the same constant value is also observed in A+A collisions independent of collision system, energy, and centrality. At lower $p_T$, where accurate $\eta/\pi^0$ data is absent for A+A collisions, we estimate possible deviations from the universal behavior, which could arise due to the rapid radial hydrodynamic expansion of the A+A collision system. For A+A collisions at RHIC we find that possible deviations are limited to the $p_T$ range from 0.4 to 3 GeV/$c$, and remain less than 20\% for the most central collisions.

Speaker: Axel Drees

Ren-Drees-Poster-QM2022.pdf

19:10 Dilepton Signature of a First-Order Phase Transition

Dileptons provide a unique way to access the properties of the fireball created in heavy-ion collisions. Since the dilepton yield directly depends on the duration of the fireball evolution, dileptons are valuable probes of the phase structure of strongly interacting matter. We study dilepton production in the SIS18 energy range by calculating and comparing the thermal dilepton emission for coarse grained microscopic transport models and hydrodynamical approaches with different equations of state, applying state-of-the-art in-medium spectral functions from hadronic many-body theory, chiral mixing in a chiral mean field model as well as from functional renormalization group methods. Presenting systematic comparisons of the space-time evolution of the fireball by means of various coarse-grained transport simulations and collision systems with respect to energy and participant number, we will show that the influence of the system size on the spectra is well under control and enhancements in heavy-ion collisions at SIS18 energies stem primarily from phase transitions.
Supported by VH-NG-823, DFG CRC-TR 211 and GSI.

Speaker: Maximilian Wiest

MWiest_QM2022_Poster.pdf

19:14 Electrical conductivity of the quark-gluon plasma from the low energy limit of photon and dilepton spectra

Fluid dynamic considerations are used to determine the electric current spectral density in the regime of small energies and momenta. The spectral density in this regime is parameterized by the electric conductivity, the charge susceptibility, and the relaxation time for the electric current, which is needed for relativistic causality. Experimentally, the spectral function can be accessed through the production rates of photons and dileptons in the expanding quark-gluon plasma. We use fluid dynamic simulations of high energy nuclear collisions, together with the transport limit of the spectral density, to obtain photon and dielectron spectra for different values of the conductivity and relaxation times. The yields of photon and dileptons produced in the plasma are compared to the background from decays of short-lived hadrons. We discuss how experiments can constrain the electrical conductivity and associated relaxation time of the quark-gluon plasma.

Based on: C. Gebhardt, S. Floerchinger and K. Reygers, Electrical conductivity of the quark-gluon plasma from the low energy limit of photon and dilepton spectra, to appear.

Speaker: Stefan Floerchinger (Heidelberg University)

Poster.pdf

19:18 Centrality and system size dependence of the thermal dilepton excess yield in HADES

Electromagnetic probes offer a unique opportunity to study the conditions in heavy-ion collisions throughout their whole evolution. In particular, the spectral shapes of dilepton distributions entail information about the temperature of the hot and dense fireball, while the integrated dilepton yield is connected to its lifetime.

In this poster, measurements of dilepton observables are presented for varying centralities and for two collision systems: Au+Au and Ag+Ag at $\sqrt{s_{NN}}=2.42$ GeV.
While the collision centrality as well as beam energy are arguably the two major determinants for the conditions reached within the hottest and densest stage of the collision, the impact of the overall system size is less clear. Therefore, the Au+Au collisions are compared with Ag+Ag collisions at the same mean amount of participating nucleons $\langle A_{part} \rangle$ to provide insights about the system size dependence. First results on thermal dilepton anisotropy and anisotropy coefficients will also be presented.

Speaker: Niklas Schild

NiklasSchild_QM2022_Poster.pdf

19:22 Ratio of photon anisotropic flow

The anisotropic flow of direct photons produced in relativistic heavy ion collisions is known to be dominated by the thermal radiations. The non-thermal contributions dilute the photon anisotropic flow by adding extra weight factor in the $v_n$ calculation. The discrepancy between experimental photon anisotropic flow data and results from theoretical model calculations is not well understood even after significant developments in the model calculations as well as in the experimental analysis methods.

We show that the ratio of photon $v_n$ can be a potential observable in this regard by minimizing the non-thermal contributions and the ratio along with the individual flow parameters could be valuable to constrain the initial state as well as to understand the photon anisotropic flow from heavy ion collisions better [1].

The photon $v_2/v_3$ is found to be larger for peripheral collisions than for central collisions and the $p_T$ dependent behavior of the ratio is found to be different from the individual flow parameters. The ratio is found to be sensitive to the initial conditions of the model calculation at different $p_T$ regions compared to the individual anisotropic flow parameters.

The $v_1/v_2$ ( and $v_1/v_3$ ) shows a completely different $p_T$ dependent nature compared to $v_2/v_3$ of photons. An experimental determination of photon $v_1/v_n$ is expected to confirm the range of thermal contribution. In addition, the $v_1/v_n$ is found to be less sensitive to the initial formation time compared to $v_2/v_3$. However, $v_1/v_n$ is expected to be much more sensitive to the final freeze-out temperature as photon $v_1$ does not depend strongly on the value of $T_f$ .

[1] R. Chatterjee and P. Dasgupta, arXiv: arXiv:2106.15922

Speaker: Pingal Dasgupta

jg_QM_Pingal.pdf

18:30 → 19:30 Poster Session 2 T07_1

18:30 Correlations from global baryon number conservation

The search for the predicted first-order phase transition and the corresponding critical endpoint between the hadronic matter and quark-gluon plasma is one of the most important current challenges in high-energy physics. This problem can be addressed based on the fluctuations of e.g. net-baryon number, net-charge, or net-strangeness number measured in relativistic heavy-ion collisions. The factorial cumulants, which represent the integrated genuine multi-particle correlation functions, can be applied to quantify such fluctuations and correlations. However, the effects other than related to the first-order phase transition, e.g. the impact parameter fluctuation or correlation laws, can also generate the correlations. In this talk, the number of particles factorial cumulants originating from the global baryon number conservation will be presented. The inclusion of the short-range correlations assumption and its consequences will also be discussed. The feasibility of testing our formulas for the factorial cumulants will be mentioned.

Speaker: Michał Barej

Barej-poster-QuarkMatter2022.pdf

18:34 Origin of elliptic flow correlations between low-pT and high-pT regions in heavy ion collisions at the LHC energies

Two-component hydrodynamic model with jets, HYDJET++, is employed to analyse the data on elliptic flow correlations at low (pT < 1.25 GeV/c) and high (pT > 14 GeV/c) transverse momenta in Pb+Pb collisions at \sqrt{sNN} = 5.02 TeV. Because of these two mechanisms, describing soft and hard processes, the model calculations restored by the four-cumulant method reproduce the centrality dependence of differential elliptic flow in both soft and hard pT regions rather well without any additional tuning of model parameters. Without jet quenching in hot and dense medium the correlations in the model are very weak. We show that the experimentally observed correlations between elliptic flow at low and high transverse momenta in peripheral lead-lead collisions arise mainly because of correlations of particles in jets.

[1] L.V. Bravina et al., Phys. Rev. C 103 (2021) 034905

Speaker: Prof. Larisa Bravina (University of Oslo)

18:38 A fast method to compute conserved charge cumulants in hydrodynamic simulations

We propose and test a fast method to compute cumulants in hydrodynamic simulations of heavy-ion collisions. They comprise one of the promising tools to investigate the existence and location of the QCD critical point, as fluctuations should diverge near it. However, evaluating these from event-by-event hydrodynamic simulations is a time-consuming task, since it requires very large statistics. As a consequence, systematic analyses of the behavior of cumulants as a function of beam energy, parametrizations of bulk and shear viscosities, values of the baryon diffusion coefficient, become prohibitive. Our method is based on separating the contributions to the final fluctuations into before and after the hydrodynamical evolution, and determining the latter analytically, which reduces the number of full hydro runs required – along with the total runtime. The method is tested in the NeXSPHeRIO code and leads to reasonable results for the proton, anti-proton and net-proton cumulants of Au+Au collisions at $\sqrt{s_{NN}}=200$ AGeV.

Speaker: Frederique Grassi

sempos22.pdf

18:42 Initial state fluctuations, eccentricities and novel A-dependence of the flow harmonics in central heavy-ion collisions

The influence of initial state fluctuations on elliptic e2 and triangular e3 eccentricities and on elliptic v2 and triangular v3 flows in relativistic heavy ion collisions is studied within three Monte Carlo models. The models are based on (i) number of participant nucleons, (ii) number of binary collisions, and (iii) partonic energy density in color glass condensate (CGC) phase, respectively. We show that both, e2 and v2, weakly depend on the fluctuations except for the collisions with centrality 0-2%. In contrast, e3 and v3 are mostly determined by the initial state fluctuations. Obtained results reproduce the nontrivial centrality dependence of the ratio of flow components, v2/v3, measured in LHC experiments. For these very central collisions, a novel scaling dependence of the anisotropic flow harmonics vn on atomic number A of colliding nuclei is predicted. Namely, vn ~ A^{-1/3}. This prediction agrees well with the available experimental data.
References:
[1] G. Eyyubova, V. Korotkikh, A. Snigirev, E. Zabrodin, J. Phys. G 48 (2021) 095101

Speaker: Dr Evgeny Zabrodin (University of Oslo and SINP MSU)

18:46 A study of the (anti)deuterons source in Pb–Pb collisions with ALICE

The production of (anti)deuterons in relativistic heavy-ion collisions is currently well described by two models that point to different mechanisms of particle creation. The first of the two, the coalescence model, describes the (anti)deuteron’s creation as a result of final-state interactions among (possibly off-shell) nucleons after the chemical freeze-out. The second, the thermal model predicts the formation of the (anti)deuterons inside the fireball even before the chemical freeze-out where these particles would be in equilibrium with other hadrons. The presented study aims to improve the understanding of deuterons production by studying the pion-deuteron source magnitude employing the femtoscopy method to determine the latter. The pion-deuteron particle-emitting source size can be evaluated as a function of the pair transverse mass $m_{\rm T}$ and can be compared to the source obtained for pion-pion pairs. Differences in the $m_{\rm T}$ scaling could help in discriminating between the coalescence and thermal scenario of (anti)deuteron’s creation. The presented analysis is based on the measurement of femtoscopic correlation functions of pion-deuteron pairs in Pb--Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV using the ALICE detector.

Speaker: Wioleta Rzesa (Warsaw University of Technology (PL))

posterQM_WioletaRzesa.pdf

18:50 Direct photon-photon HBT correlations in Ag+Ag collisions at $\sqrt{S_{NN}}$ = 2.55 GeV

The study of femtoscopic correlations of photon pairs, emitted from heavy-ion collisions, can serve as an unique probe of the evolution of the source in space and time. Unlike commonly used charged particles photons are not subject to strong, nor electromagnetic interactions. These properties imply no distortion of the information carried by $γ$ from the point of their creation up to the detection in experiment. As a consequence it is plausible to investigate source features, which are not only based on the information available after thermal freeze-out, but also include previous stages of expansion. Moreover, results obtained this way are not burdened with distortions caused by surrounding particles. Unfortunately direct photon detection is not trivial and the photon yield is mainly dominated by $π^{0}$ meson decays, making a direct photon analysis suffering from the need to separate them from a background of photons emitted at different (later) stages of collision. We present first preliminary results from such an analysis of Ag+Ag collisions at $\sqrt{s_{NN}}$ = 2.55 GeV, measured with HADES at the GSI-SIS18.

Speaker: Mateusz Grunwald (Warsaw Universty of Technology)

QM2022_MGrunwald_v3.pdf

18:54 Performance studies of femtoscopy at CBM

The study of nucleon-nucleon (N-N), nucleon-hyperon (N-Y), and hyperon-hyperon (Y-Y) interactions are fundamental to understanding the physics of relativistic heavy-ion collisions and neutron stars the existence of various exotic hadrons. Geometry and dynamics of the particle-emitting source in heavy-ion collisions can be inferred via the femtoscopy method. Two-particle correlations at small relative momentum exploit Quantum Statistics (QS) and the Final State Interactions (FSI), which allow one to study the space-time characteristics of the source of the order of 10^{−15} m and 10^{−23} s. Femtoscopy also enables the investigation of FSI between hadrons, as searches of possible bound states in neutron stars. The CBM experiment will cover a significant part of the QCD Phase Diagram using collisions of heavy nuclei for several beam energies, which baryon-rich region will be studied via femtoscopy. Baryon measurements together with meson ones provide complementary information about source characteristics.
In this poster, performance studies of femtoscopic measurements of various particle combinations at different collision energies and centralities will be shown.

Speaker: Daniel Wielanek (Warsaw University of Technology, Faculty of Phycis, LHEP JINR)

QM2022_poster_CBM-22_2.pdf

18:58 Probing the initial conditions of ultra-relativistic nuclear collisions at the LHC with multi-particle cumulants of transverse momentum

The primary goal of the ultrarelativistic heavy-ion collision program at the LHC is to recreate the quark-gluon plasma (QGP) and study its properties. However, the lack of knowledge on the initial conditions of heavy-ion collision results in a significant uncertainty of the extraction of the transport properties of QGP. Recently, it has been realized that the generation of transverse momentum is sensitive to the initial conditions, including the size and the initial shape, in terms of the deformation parameter of the colliding nucleus. In this contribution, we propose that multi-particle cumulant of mean transverse momentum $p_{\rm T}$ as a powerful probe of initial conditions in relativistic nuclear collisions. This study is based on establishing a whole new generic algorithm of multi-particle cumulants of mean transverse momentum. It significantly extends the current study to very higher-order cumulants that have never been investigated before. We will present the first Monte Carlo calculations using AMPT transport model to illustrate the implications of this new tool to probe the initial conditions. In addition, based on PYTHIA model simulations, we will show how to eliminate the trivial few-particle transverse momentum correlations that will potentially bias future experimental measurements at the LHC.

Speakers: Anna Ingmer Boye (Niels Bohr Institute), Frederik Sebastian Kehn Jensen (Niels Bohr Institute)

QM22_v3.pdf

19:02 Anisotropic flow decorrelation in heavy-ion collisions at RHIC-BES energies with 3D event-by-event viscous hydrodynamics

In the RHIC Beam Energy Scan program, gold nuclei are collided with different collision energies in the range from few to 62.4 GeV. The goals of the program are to explore the onset of QGP creation, locate the critical point of QCD and study dense baryon matter.
In this talk, we report on the first application of 3D Monte Carlo Glauber (GLISSANDO2) and TrENTO p=0 initial states for 3D event-by-event viscous fluid dynamic (vHLLE) + cascade modelling of Au+Au collisions at √sNN=27 and 62.4 GeV, which is the upper region of RHIC BES energies. The initial states are extended into both the longitudinal direction and for finite baryon density using simple ansätze. The full energy and baryon charge counting in the initial states is implemented. We show the reproduction of basic hadronic observables - pseudorapidity distributions of charged hadrons and net protons, transverse momentum spectra and elliptic flow, at both collision energies and with both initial states. We compare it to the existing results obtained with UrQMD initial state.
Furthermore, we show the results for rapidity decorrelation of elliptic flow r2 at √sNN=27 and 200 GeV from the same setup of hydrodynamic calculations with the 3D Monte Carlo Glauber and UrQMD initial states. We discuss the features of the initial states responsible for the magnitude of the observed flow decorrelation, and the effect of the final-state hadronic cascade.
Publication references: Phys. Rev. C 103, 034902 (2021), Phys. Rev. C 104, 014904 (2021)

Speakers: Jakub Cimerman (Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University), Barbara Antonina Trzeciak (Czech Technical University in Prague)

Poster_Cimerman_QM.pdf

19:06 Symmetric Levy HBT measurements at NA61/SHINE

In the recent decades of high energy physics, it was revealed that in ultra-realistic ion-ion collisions, a strongly interacting quark-gluon plasma (sQGP) is created. One of the most important goals of NA61/SHINE is to investigate and understand the phase structures of this matter. The investigation of the phase-diagram can be achieved by varying the collision energy or by changing the collision system. Investigating femtoscopic correlations in these collisions reveals the space-time structure of the hadron emitting source of the sQGP.
Here we report the comparison of the measurements of femtoscopic Bose-Einstein correlations in Be+Be and Ar+Sc collisions at 150A GeV/c beam momentum. Comparing the measurements to calculations based on alpha-stable symmetric Levy sources, we discuss the average pair transverse mass dependence of the source parameters. One of the source parameters, the Levy exponent alpha, is of particularly importance. It describes the shape of the source, which, in the vicinity of the critical point of the phase diagram, may be related to the critical exponent eta. Its measurement hence may contribute to the search for and characterization of the critical end point of the phase diagram.

Speaker: Barnabas Porfy (Wigner Research Centre for Physics (Wigner RCP) (HU))

bporfy_poster_win.pdf

19:10 Space-time evolution of critical fluctuations in an expanding system

The search for the QCD critical point is one of the main topics in high-energy nuclear collisions. There are active studies aiming to find signals of the QCD critical point and the first order phase transition, such as the BES programs at the Relativistic Heavy-Ion Collier (RHIC), and many future experiments such as FAIR, NICA, J-PARC-HI, and HIAF. For detecting the signals of the critical point in these experiments, we need a proper model describing the evolution of the dense QCD matter created in the nuclear collisions. To this end, it is very important to understand dynamical effects of the critical fluctuations on experimental observables.

Critical phenomena associated with the QCD critical point are characterized by the divergent fluctuations of the chiral condensate $\sigma = \langle\bar{q}q\rangle$ and the baryon number density $n_B$ [1,2]. In the idealized case where the system is close to equilibrium, the fluctuations of (non-conserved) chiral condensate $\sigma$ can be integrated out as a fast mode, and the critical dynamics is governed by fluctuations of the baryon number density and other hydrodynamic modes. However, it is quite non-trivial whether we can ignore the $\sigma$ mode as the fast mode in the high-energy nuclear collisions because the time-scale separation is unclear there; The $\sigma$ mode could affect the space-time evolution of the critical dynamics.

In our study, we construct a framework to describe the dynamics of the critical fluctuations including the relaxation time for baryon diffusion current and the coupling of the chiral condensate $\sigma$ to the baryon density $n_B$. We apply this to one-dimensionally expanding system with the QCD critical point and investigate the effect of the relaxation time and the mode coupling on the correlation of baryon density $n_B$ as a function of rapidity interval.

[1] H. Fujii and M. Ohtani, Phys. Rev. D 70, 014016 (2004)
[2] D. T. Son and M. A. Stephanov, Phys. Rev. D 70, 056001 (2004)

Speaker: Azumi Sakai (Sophia University)

QM2022_Sakai.pdf

19:14 Measurement of $R_{2}(\Delta\eta, \Delta\varphi)$ and $P_{2}(\Delta\eta, \Delta\varphi)$ correlation functions in pp collisions at $\sqrt{\textit{s}}$ = 13 TeV using ALICE data

Two-particle normalized cumulants of particle number correlations ($R_{2}$) and transverse momentum correlations ($P_{2}$) measured as a function of relative pseudorapidity and azimuthal angle difference $(\Delta\eta, \Delta\varphi)$ provide key information about particle production mechanism, diffusivity, charge and momentum conservation in high-energy collisions. To complement the recent ALICE measurements in Pb--Pb collisions, as well as for better understanding of the jet contribution and nature of collectivity in small systems, we measure these observables in pp collisions at $\sqrt{\textit{s}}$ = 13 TeV with similar kinematic range, 0.2 $<$ $\textit{p}_{\rm T}$ $\leq$ 2.0 $\rm{GeV}/\textit{c}$. The near-side and away-side correlation structures of $R_{2}$ and $P_{2}$ are qualitatively similar, but differ quantitatively. Additionally, a significantly narrower near-side peak is observed for $P_{2}$ as compared to $R_{2}$ for both charge-independent and charge-dependent combinations like in the recently published ALICE results in p--Pb and Pb--Pb collisions. Being sensitive to the interplay between underlying event and mini-jets in pp collisions, these results not only establish a baseline for heavy-ion collisions but also allow one to understand better signals which resemble collective effects in small systems.

Speaker: Baidyanath Sahoo (IIT- Indian Institute of Technology (IN))

Baidya_Poster_QM22.pdf

19:18 Flow-Plane Decorrelations and Longitudinal Dynamics in Heavy-Ion Collisions

The azimuthal correlations among local flow planes at forward, middle and backward (pseudo)-rapidities have been measured with the observable of factorization ratio derivative $F_2$ for heavy-ion collisions at LHC and RHIC energies. The physical dynamics for the longitudinal decorrelation have not been determined. To study various longitudinal dynamics, we introduce an observable for the torque measurements ($T_2$) using multiple-plane cumulants, and systematically evaluate the $F_2$ and $T_2$ performance through simulations of AMPT, AMPT embedded with PYTHIA jet, and non-flow phenomenological toy models. Possible longitudinal dynamics such as initial twist of participant matter and jet induced non-flow correlations would lead to distinct different rapidity dependence of $F_2$ and $T_2$ measurements. In particular, we show that $T_2$ observable can significantly suppress the non-flow contributions because of the cumulant method. We argue that such decorrelation measurements with both $F_2$ and $T_2$ observables are important for low energy heavy-ion collisions at RHIC, where hydrodynamic fluid may not extend over sufficiently broad rapidity range.

Speaker: Zhiwan Xu

19:22 Fluctuations in heavy ion collisions and global conservation effects

We analyze the behavior of cumulants of conserved charges in a subvolume of a thermal system with exact global conservation laws by extending [1] a recently developed [2] subensemble acceptance method (SAM) to multiple conserved charges. Explicit expressions for all diagonal and off-diagonal cumulants up to sixth order that relate them to the grand canonical susceptibilities are obtained. The derivation is presented for an arbitrary equation of state with an arbitrary number of different conserved charges. The global conservation effects cancel out in any ratio of two second order cumulants, in any ratio of two third order cumulants, as well as in a ratio of strongly intensive measures $\Sigma$ and $\Delta$ involving any two conserved charges, making all these quantities particularly suitable for theory-to-experiment comparisons in heavy-ion collisions. We also show that the same cancellation occurs in correlators of a conserved charge, like the electric charge, with any non-conserved quantity such as net proton or net kaon number. The main results of the SAM are illustrated in the framework of the hadron resonance gas model. We also elucidate how net-proton and net-$\Lambda$ fluctuations are affected by conservation of electric charge and strangeness in addition to baryon number.

[1] V.Vovchenko, R.V.Poberezhnyuk, V.Koch, JHEP 10 (2020) 089
[2] V.Vovchenko, O.Savchuk, R.V.Poberezhnyuk, M.I.Gorenstein, V.Koch, Phys.Lett.B 811 (2020) 135868

Speaker: Mr Roman Poberezhnyuk (Bogolubov Institute for Theoretical Physics)

18:30 → 19:30 Poster Session 2 T07_2

18:30 Measurement of long-range correlations and $\it{v}_{2}(\eta)$ in pp and p--Pb collisions with ALICE

Measurements of long-range correlations are one of the important tools for evaluation of the interplay between the initial- and final-state effects. Recently, non-vanishing second Fourier harmonic $\it{v}_{2}$ has been observed in small collision systems such as pp and p--Pb collisions. In this contribution, we present measurements of $\it{v}_{2}$ extracted from long-range two-particle correlations for different charged particles multiplicities in pp at $\sqrt{s} = 13~\rm{TeV}$ and in p--Pb collisions at $\sqrt{s_{\rm NN}} = 5.02~\rm{TeV}$.These measurements utilize the Forward Multiplicity Detector, which allows for unprecedented pseudorapidity ($\Delta\eta$) ranges to be explored (up to $\Delta\eta ~\sim 8$). We show the result of the $\eta$ dependence of $\it{v}_{2}$ over a wide pseudorapidity range ($-3.1<\eta<4.8$). Results are compared with the AMPT and hydrodynamical calculations.

Speaker: Ms Yuko Sekiguchi (University of Tokyo (JP))

QM22_yuko_v4.pdf

18:34 Critical point particle number fluctuations from molecular dynamics

We study fluctuations of particle number in the presence of critical point by utilizing molecular dynamics simulations of a classical Lennard-Jones fluid in a periodic box. The numerical solution of the $N$-body problem naturally incorporates all the relevant effects like physics of the correlation length, exact conservation laws, and finite size effects, allowing us to study the luctuation signatures of the critical point in a dynamical setup.We find that large fluctuations associated with the critical point are observed when measurements are performed in the coordinate subspace, but, in the absence of collective flow and expansion, are essentially washed out when momentum cuts are imposed instead. We put our findings in the context of event-by-event fluctuations in heavy-ion collisions.

Speakers: Mr Volodymyr Kuznietsov, Oleh Savchuk (Frankfurt Institute for Advanced Studies), Volodymyr Vovchenko (Lawrence Berkeley National Laboratory)

KuznietsovQM2022.pdf

18:38 Complementary Two-Particle Correlation Observables for Relativistic Nuclear Collisions

Two-particle correlations are a widely used tool for studying relativistic nuclear collisions. Multiplicity fluctuations have been studied as a possible signal for QGP and the QCD critical point. Momentum correlations and covariances of momentum fluctuations, which arise from the same correlation function, have also been used to extract properties of the nuclear collision medium such as the shear viscosity to entropy density ratio, the shear relaxation time, and temperature fluctuations. We derive a mathematical relationship between several number and momentum density correlation observables and outline the different physics mechanisms often ascribed to each. This set of observables also contains a new multiplicity-momentum correlation. Our mathematical relation can be used as a validation tool for measurements, as a method for interpreting the relative contributions of different physics mechanisms on correlation observables, and as a test for theoretical and phenomenological models to simultaneously explain all observables. We compare an independent source model to simulated events from PYTHIA for all observables in the set.

Speaker: Prof. George Moschelli (Lawrence Technological University)

Moschelli_poster_QM2022.pdf

18:42 ATLAS measurement of the two-particle correlation sensitivity to jets in $pp$ collisions

Measurements of two-particle correlations in $pp$ collisions show the presence of long-range correlations along $\Delta\eta$ that are strikingly similar to those seen in heavy-ion collisions.
In larger systems, the long-range correlations are known to arise from the collective dynamics of the produced quark-gluon plasma (QGP). The similarity between the $pp$ and heavy-ion measurements raises the possibility that a tiny droplet of the QGP is produced even in $pp$. However, models that attribute the correlation in $pp$ collisions to semi-hard processes can qualitatively reproduce the measurements. Thus performing the $pp$ measurements with distinguishing particles associated with semi-hard processes, such as low-$p_{\mathrm{T}}$ jets, can further elucidate the origin of the long-range correlations. This talk presents a new measurements of two-particle correlations in $pp$ collisions at $\sqrt{s}=13$ TeV with two different particle pair selections. In the first case, tracks associated with jets are excluded from the correlation analysis. This case results in a minor influence on the magnitude of the long-range correlation. In the second case, the two-particle correlations are measured between jet constituents and the underlying-event tracks. In this case, the correlations show no ridge-like structure.

Speaker: Pengqi Yin (Columbia University (US))

QM2022_poster_PengqiYin.pdf

QM2022 poster slides.pdf

18:46 Searching for the gluon saturation scale at $x \sim 10^-5$ with the LHCb detector using direct photons

Because of the increasing gluon density towards small-$x$, a regime where these densities reach a saturation ($Q_{\rm sat}$) is expected. The observation of this gluon saturated matter has several consequences to particle production and is a matter of an entire effective field theory, the Color Glass Condensate. The Large Hadron Collider beauty (LHCb) experiment has a privileged geometry for the search of the gluon saturation achieving an unprecedent small-$x$ coverage. The most direct measurement of gluon densities and kinematics in hadronic collisions is the inverse Compton process $(q+g\rightarrow \gamma+q)$. The LHCb experiment measured pairs of isolated photons correlated with hadrons from the quark fragmentation in pPb and Pbp collisions at 8.16 TeV probing a Bjorken-$x$ between $10^{-5}

Speaker: Cesar Luiz Da Silva (Los Alamos National Laboratory (US))

gamma_hadron-QM22.pdf

18:50 Study of the kurtosis out-of-equilibrium

The search for the Quantum Chromodynamics (QCD) critical point is underway at the Relativistic Heavy-Ion Collider (RHIC) Beam Energy Scan II. The primary signature of the critical point is a peak (divergence) in the kurtosis of the net-proton number distribution, $\kappa_4$. Most previous studies of kurtosis have focused on equilibrium physics, whereas it is well-known that out-of-equilibrium effects are vital in understanding the Quark Gluon Plasma (QGP). Out-of-equilibrium effects near the vicinity of the critical point can dramatically alter the trajectory through the QCD phase diagram from equilibrium. We find that the size and shape of the critical region play an important role in whether or not the critical point will be effectively seen in the dynamic evolution. Critical regions which extend in the $T$ direction have a stronger dip in the speed of sound, which focus trajectories towards the critical point and influence the kurtosis.

Speaker: Travis Dore (University of Illinois at Urbana-Champaign)

DORE_QM21.mp4

DORE_QM21.pdf

DORE_QM21.pptx

18:54 PHENIX measurements of elliptic flow of inclusive open heavy flavor mesons at forward rapidity in 200 GeV Au+Au collisions

Near perfect fluid behavior is a hallmark signature of the quark gluon plasma (QGP), however, how this behavior emerges is still not fully understood. Thus, measurements of many different particles over a wide rapidity range are needed to understand this phenomenon. Heavy quark flow is expected to be different from light quark flow due to their larger masses, making heavy flavor flow measurements particularly important for understanding QGP behavior. The flow of heavy flavor particles can be measured via their decay muons in forward and backward rapidity using PHENIX’s muon spectrometers (1.2<|η|<2.2). Additionally, PHENIX has unique capabilities for measuring the radial distance of closest approach (DCAr) using the forward silicon vertex detector (FVTX), which allows for improved background subtraction from the heavy flavor signal, making it the only RHIC detector capable of performing this measurement at forward and backward rapidities. We will present the status of elliptic flow measurements of the inclusive heavy flavor decayed muons in the 0-7 GeV/c transverse momentum range using the Run14 Au+Au 200 GeV dataset (roughly 16 billion events). Preliminary results for charged hadron and inclusive muon elliptic flow will also be presented.

Speaker: Mr Brandon Blankenship (PHENIX Collaboration)

18:58 Dynamics of coupled baryon, electric charge and strangeness fluctuations in expanding heavy-ion collision.

Fluctuation observables in heavy-ion collisions probe the medium constituents, the chemical freeze-out and the transport properties of strongly interacting matter, and signal phase transitions. However, diffusion in the medium may blur some of the expected signals. It is thus crucial to understand the diffusive dynamics of the conserved charge fluctuations to know to which degree measured fluctuations report bulk fluctuations during the evolution.
Two major ingredients determine the dynamical evolution of the fluctuations, the natural coupling between the diffusive properties of the conserved charges and the longitudinal expansion of the medium. Their non-trivial interplay largely impacts the in- or out- of equilibrium nature of the fluctuations.
We present the coupled diffusive dynamics of net-baryon, net-charge and net-strangeness fluctuations in a rapidly expanding medium. The model consists of a set of three coupled stochastic diffusion equations. The diffusion matrix comes from microscopic calculations both in the hadron phase and in the QGP. We particlize the density fluctuations in order to obtain fluctuations in particle numbers, which reflect the cross-correlations between the charges. Special emphasis is put on the Lambda fluctuations. The phenomenological consequences on the determination of the freeze-out condition determination via strangeness observables are discussed.

Speaker: Grégoire PIHAN

19:02 What initial energy fluctuations are necessary to correctly describe flow in ultra-central collisions?

Modern models for describing heavy-ion collisions have difficulty reproducing observed flow in very central collisions -- a problem known as the ultra-central flow puzzle. It is therefore useful to understand what properties the initial stages must have in order to be compatible with experimental data. To this end, we parameterize the early-time energy density and its fluctuations via its 1-point and 2-point function, and constrain them by using experimental data for vn{2} in conjunction with hydrodynamic simulations, including a systematic scan of model parameters such as shear and bulk viscosity. We compare the results to current models, and comment on why they fail to describe measurements.

Speaker: Liner Santos (Universidade de Sao Paulo)

apresentacao-QM-2022-resumo.pdf

19:06 Signals from the critical point in Bjorken fluid dynamics

A non-monotonic net-proton kurtosis for very central collisions at $\sqrt{s} = 200$ GeV has been suggested and may be confirmed by recent BES-II program results advocating the existence of the QCD critical point. Fluctuations at the origin of this peculiar behavior are produced in the highly dynamical environment of ultra-relativistic collisions. Especially, the violent longitudinal expansion and the associated temperature cooling may have a non-trivial impact on how we interpret the experimental data. The in- or out-of equilibrium nature of the fluctuations during this expansion is a crucial question in discriminating between critical contributions and purely dynamical features.
Here, we inspect the diffusive dynamics of the critical net-baryon density fluctuations coupled to energy and momentum fluctuations. Equations are expressed in the Milne coordinates to include the longitudinal Bjorken-type expansion in 1+1D. Fluctuations are connected to critical point physics using a stochastic diffusion equation in which the potential is derived from a free-energy functional including non-linear coupling and fully parametrized by the second a fourth order susceptibilities. The latter come from the 3D Ising model correlation length in the scaling region and lattice QCD calculations at vanishing baryo-chemical potential.
We demonstrate the great sensitivity of the second and fourth order cumulants of the net-baryon and energy density fluctuations to the expansion dynamics. Via particlization the net-proton number cumulants are obtained. Special emphasis is put on the dependence on the diffusion length and the freeze-out conditions. The phenomenological consequences of these two parameters are discussed. We study the non-trivial rapidity dependence as a signal for the QCD critical point.

Speaker: Marlene Nahrgang (Subatech)

19:10 New approach to study intermittency by NA61/SHINE

The existence and location of the QCD critical point is an object of both experimental and theoretical studies. One of the main goals of NA61/SHINE, a fixed-target experiment at the CERN SPS, is the search for the critical point of the strongly interacting matter. The comprehensive data collected during a two-dimensional scan in beam momentum (13A-150A GeV/c) and system size (p+p, p+Pb, Be+Be, Ar+Sc, Xe+La,Pb+Pb) allows for a systematic search for the critical point - the search for a non-monotonic dependence of various correlation and fluctuation observables on collision energy and size of colliding nuclei. An example of such observable is local fluctuations of particle densities in transverse momentum space, which can be probed with an intermittency analysis by measuring the scaling behavior of factorial moments of multiplicity distributions.

This contribution will present a new approach to search for the critical point of strongly interacting matter via intermittency analysis using cumulative variables and independent sub-sample for each data point.

HA_QM2022_Poster.pdf

19:14 Inferring nuclear structure from heavy isobar collisions using Trajectum

Nuclei with equal number of baryons but varying proton number (isobars) have many commonalities, but differ in both electric charge and nuclear structure. Relativistic collisions of such isobars provide unique opportunities to study the variation of the magnetic field, provided the nuclear structure is well understood. In this Letter we simulate collisions using several state-of-the-art parametrizations of the 9640Zr and 9644Ru isobars and show that a comparison with the exciting STAR measurement arXiv:2109.00131 of ultrarelativistic collisions can uniquely identify the structure of both isobars. This not only provides an urgently needed understanding of the structure of the Zirconium and Ruthenium isobars, but also paves the way for more detailed studies of nuclear structure using relativistic heavy ion collisions.

Speaker: Dr Wilke Van Der Schee (CERN)

talk_IsobarQM.pptx

19:18 Impact of mini-jets in bulk observables within a concurrent evolution approach

Mini-jets, created by perturbative hard QCD collisions at moderate energies, can represent a significant portion of the total multiplicity of a heavy-ion collision event. Given the fact that their transverse momenta are initially larger than the typical saturation scale describing the bulk of the equilibrating QGP, they ought to be described through the physics of parton energy loss. Indeed, their typical stopping distances are larger than the usual hydrodynamization time, so they do not in general hydrodynamize at the same pace than the bulk of the collision. Therefore, in general mini-jets cannot be described solely by a unique pre-equilibrium stage that bridges the initial, over-occupied glasma state, with the hydrodynamical evolution.

In this work we make use of a new concurrent mini-jet+hydrodynamic framework in which the properties of the hydrodynamically evolving QGP are modified due to the injection of energy and momentum from the mini-jets. We study the system for different choices of the minimum transverse momentum associated to mini-jet production. In order to achieve a realistic description of charged particle multiplicity, the amount of entropy associated to the low-x initial state needs to be reduced. Moreover, the fact that the injected momentum from the randomly oriented mini-jets is not correlated with the spatial gradients of the system reduces overall flow, and the value of the QGP transport coefficients needs to be reduced accordingly in order to describe the measured flow coefficients in experiments. They are, in effect, an important new source of fluctuations, resulting in a spikier, notably modified hydrodynamical evolution when compared to the scenario in which the presence of mini-jets is ignored. We avow that their abundance makes it necessary to include their physics in holistic descriptions of heavy-ion collisions. We will discuss the potential impacts of this modified hydrodynamical evolution on a number of observables, and also propose ways in which the currently unknown relevant scale for mini-jet production can be constrained by data.

Speaker: Dr Daniel Pablos (University of Bergen)

qm22_pablos.pdf

19:22 Studies of strong interactions with femtoscopy in Au+Au collisions at RHIC/STAR

Two particle correlation analysis is often used to study the spatial and temporal extents of particle emitting source in high-energy nuclear collisions. By studying the quantum statistical effects (QS) and final state interactions (FSI) between two particles, one can extract emission source parameters used to describe the geometrical and dynamical properties of the homogeneity region. Traditional two-meson correlations can be sensitive to the early stage of the collision evolution and provide different information about particle-emitting sources. From hyperon-nucleon correlations, one can extract interactions between them. It is particularly interesting to study the dependence on the collision energy because freeze-out condition depends on the energy.

In this poster, femtoscopic results of the system of different particle species including kaons, protons, $\Lambda$, and $\Xi$ in Au+Au collisions from STAR will be presented. The new results will be compared with model calculations.

Speaker: Zhi Qin (Tsinghua University)

pXi_CorrelationFunction_qm22poster_v5.pdf

19:26 Unfolding the effects of final-state interactions and quantum statistics in two-particle angular correlations

Angular correlations of identified particles measured in ultrarelativistic proton-proton (pp) and heavy-ion collisions exhibit a number of features which depend on the collision system and particle type under consideration. Those features are produced by mechanisms, such as (mini)jets, elliptic flow, resonance decays, and conservation laws. In addition, of particular importance are those related to the quantum statistics (QS) and final-state interactions (FSIs).

In our recent work [1] we show how to unfold the QS and FSI contributions in angular correlation functions by employing a Monte Carlo approach and using momentum correlations (femtoscopy), focusing on pp reactions. We validate the proposed method with PYTHIA 8 Monte Carlo simulations of pp collisions at $\sqrt{s}=13$ TeV coupled to calculations of QS and FSI effects with the Lednický and Lyuboshitz formalism and provide predictions for the unfolded effects. In particular, we show how those effects modify the shape of the angular correlation function with emphasis on pions and protons. Most importantly, specific structures in the near-side region ($(\Delta\eta,\Delta\varphi)\approx(0,0)$) of the two-baryon angular correlation function, namely a small enhancement in the middle of a depletion for proton-proton pairs in pp collisions at $\sqrt{s}=7$ TeV, observed by ALICE [2], and a depletion for $\rm p\overline{p}$ pairs in Au-Au collisions at collision energies from $\sqrt{s_{\rm NN}}=7.7$ GeV to $\sqrt{s_{\rm NN}}=200$ GeV, observed by STAR [3], originating from the strong interaction, are unveiled with the proposed method. The unfolding of the FSI and QS effects is not able to explain the wide anticorrelation effect at near-side observed by ALICE universally for all baryon-baryon and corresponding antibaryon-antibaryon pairs ($\rm pp\oplus\overline{p}\overline{p}$, $\rm p\Lambda\oplus\overline{p}\overline{\Lambda}$ and $\rm \Lambda\Lambda\oplus\overline{\Lambda}\overline{\Lambda}$).

The inverse unfolding procedure, from the angular space to the relative momentum space, is also possible. Our preliminary studies suggest that it can allow for a data-driven estimation of non-femtoscopic background in femtoscopic correlations using measured two-particle angular correlations instead of relying on Monte Carlo models.

[1] Ł. Graczykowski, M. Janik, Phys. Rev. C 104, 054909 (2021)
https://arxiv.org/abs/2108.00678
[2] J. Adam et al. (ALICE Collaboration), Eur. Phys. J. C77 (2017) 56
https://arxiv.org/abs/1612.08975
[3] J. Adam et al. (STAR Collaboration), Phys. Rev. C 101, 014916 (2020)
https://arxiv.org/abs/1906.09204

Speaker: Lukasz Kamil Graczykowski (Warsaw University of Technology (PL))

QM2022_poster_wide_v8.pdf

18:30 → 19:30 Poster Session 2 T08 / T09

18:30 Initial electromagnetic field dependence of photon-induced production in isobaric collisions at STAR

Strong electromagnetic field arising from the Lorentz-contraction and a large number of charges (Z) in the colliding nuclei at ultrarelativistic speeds can generate a large flux of quasi-real photons. Consequent photon-induced interactions could reasonably explain the observed enhancements of $J/\psi$ and $e^{+}e^{-}$ pair productions at very low transverse momenta ($p_{T}$) in peripheral high-energy heavy-ion collisions, via photonuclear ($\propto$ $Z^{2}$) and photon-photon ($\propto$ $Z^{4}$) processes. STAR has collected a large sample of $^{96}_{44}Ru$+$^{96}_{44}Ru$ and $^{96}_{40}Zr$+$^{96}_{40}Zr$ collisions at $\sqrt{s_\mathrm{NN}}$ = 200 GeV in 2018, around two billion good events for each collision system. The isobaric collisions, with different number of charges and same number of nucleons in the colliding nuclei, provide a unique opportunity to test the electromagnetic field dependence of photon-induced production.
In this presentation, we will present the first measurement of the electromagnetic field dependence of $J/\psi$ and $e^{+}e^{-}$ pair production at very low $p_{T}$, via comparisons between the new measurements in isobaric collisions as well as to the published results in Au+Au collisions at $\sqrt{s_\mathrm{NN}}$ = 200 GeV. Physical implications of these results will be discussed.

Speaker: Kaifeng Shen

QM_poster_Kaifeng_v7.pdf

video1253084164.mp4

18:34 Low-$p_{T}$ $\mu^{+}\mu^{-}$ pair production in Au+Au collisions at $\sqrt{s_{_{\rm NN}}}$ = 200 GeV at STAR

Recently, significant enhancements of $e^{+}e^{-}$ pairs at very low transverse momentum ($p_{T}$) were observed by the STAR collaboration in peripheral Au+Au collisions. The excess can be explained by photon-photon interactions induced by the extremely strong electromagnetic field produced by the fast-moving heavy ions. These photon-photon interactions could provide a novel probe to the Quark-Gluon Plasma (QGP) since the very-low-$p_{T}$ dileptons are produced at the early stage of the collisions. Furthermore, the linearly polarized photons will lead to angular modulations of produced dileptons, which is related to vacuum birefringence. Theoretical calculations predict that the angular modulation of $\mu^{+}\mu^{-}$ pairs is different from $e^{+}e^{-}$ pairs due to the different masses. Therefore, measurements of $\mu^{+}\mu^{-}$ pairs provide new insight to these phenomena in heavy-ion collisions.
In 2014 and 2016, the STAR experiment recorded large samples of Au+Au collisions at $\sqrt{s_{_{\rm NN}}}$ = 200 GeV. In this presentation, we will present the first measurements of photo-produced $\mu^{+}\mu^{-}$ pairs at STAR. Physics implications will be discussed together with model comparisons.

Speaker: Jian Zhou (USTC)

QM2022_poster_JianZhou.mp4

QM2022_poster_slide_JianZhou_v2_1.pdf

18:38 Perspectives for future UPC measurements in ALICE during Run 3, Run 4 and Run 5

The ALICE experiment has significantly upgraded its detectors. It will make possible to perform new measurements in the Ultra Peripheral Collisions (UPCs) of lead nuclei for the integrated luminosity of $\mathcal{L}^{\rm Pb-Pb}=13$/nb during Run 3 and Run 4. For Run 5 and beyond, a completely new next-generation heavy-ion experiment ALICE 3 is proposed. The new detector system will cover
much larger pseudorapidity range $\Delta \eta \sim 8$ and reach very low $p_{\rm T} \sim 10$ MeV/$c$. The target integrated luminosity in Run 5 and beyond is $\mathcal{L}^{\rm Pb-Pb}=35$/nb. In this presentation, we will focus on prospects for measurements of the light-by-light scattering at low invariant masses below $M_{\rm inv}<5$ GeV/$c^2$ and $\tau$ pair production in UPCs sensitive to the $\tau$ anomalous magnetic moment. Both processes are sensitive to physics beyond the Standard Model, in particular, light-by-light scattering measurements can be used to set new upper limits in axion-like particles searches. Perspectives of vector meson photoproduction measurements which allow for gluon distribution function constraints will be also presented.

Speaker: Adam Matyja (Polish Academy of Sciences (PL))

QM2022_AdamMatyja_final.pdf

18:42 Final state electromagnetic interaction of electrons and positrons with heavy nuclei in ultra-peripheral ultra-relativistic heavy-ion collisions

The photon-photon interaction in ultra-relativistic heavy-ion collision is a source of the $(e^+,e^-)$ pairs. The photon-photon fusion leads to the lepton creation in the broad configuration space around ''collision'' point. Those created close to heavy nuclei may undergo strong interaction with them.
The impact parameter space distributions of electrons and positrons are calculated within the b-space EPA model and Wigner-function approach. The evolution due to the electromagnetic final state interaction (FSI) of $(e^+,e^-)$ with nuclei is studied, and the distortion of rapidity and transverse momentum distributions are shown. Part of the analysis is independent of the production model (initial condition).

We show first exploratory results for the reaction Pb+Pb at $\sqrt{s_{NN}}=$ 17.3~GeV (SPS) and 200~GeV (RHIC) energies. We provide results for selected creation points and when integrating over their position as dictated by the $b$-space EPA model. We observe a strong influence at low transverse momenta, so far not measured regions of the phase space. In particular, we predict a possible sizeable accumulation of electrons with rapidities close to the beam rapidity. The EM effects lead to asymmetry in the production of electrons and positrons.

[1] K. Mazurek at el. arXiv:2107.13239

Speaker: Katarzyna Mazurek (IFJ PAN)

EMlepton_QM.pdf

18:46 Light-by-light scattering at low diphoton energies from ultraperipheral heavy-ion collisions at the LHC

We present a study of photon-photon scattering in the mass range $W_{\gamma \gamma}<5$ GeV. We extend earlier calculations of this cross section for $W_{\gamma \gamma}>5$~GeV into the low mass range where photoproduction of the pseudoscalar resonances $\eta$, $\eta'(958)$ contributes to two-photon final states. We present the elementary photon-photon cross section as a function of diphoton mass $M_{\gamma \gamma}$ arising from lepton and quark loop diagrams, and the visible cross section obtained with the gamma-gamma decay branching fractions of the resonances $\eta$, $\eta'(958)$, $\eta_C(2S)$, $\chi_{c0}(1P)$. We derive the corresponding cross sections in ultraperipheral Pb-Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV by folding the elementary cross section with the heavy-ion photon fluxes. We consider the dominating background of the two-photon final
state which arises from gamma decays of photoproduced $\pi^0$-pairs. Such $\pi^0$-pairs contribute to the background when only two of the four decay photons are within the experimental acceptance, while the other two photons escape undetected. We show how to reduce this background by applying cuts on asymmetries of transverse momenta of the two photons and indicate how the background can be further suppressed using a multivariate sideband analysis. We present the cross section for the signal and the background at midrapidity $|\eta|<0.9$, and in the forward rapidity range $2.0<\eta<4.5$.

Mariola Kłusek-Gawenda, Ronan McNulty, Rainer Schicker, and Antoni Szczurek,
Phys. Rev. D99 093013 (2019).

Speaker: Dr Mariola Klusek-Gawenda (Institute of Nuclear Physics Polish Academy of Sciences)

MKG_QM2022_poster.pdf

18:50 Lepton pair photo-production in Ultra-peripheral and peripheral heavy ion collisions

The lepton pair production in ultraperipheral collisions is studied in the classical field approximation. We derive a general form of the cross section in terms of photon distributions that depend on the transverse momentum and coordinate based on the wave packet form of nuclear wave functions. Such a general form of the cross section in the classical field approximation contains the results of the generalized equivalent photon approximation (EPA) as well as the corrections beyond EPA in the Born approximation. By rewriting the general form of the cross section in light-cone coordinates, we find a good connection with the transverse momentum dependent distribution factorization formalism in the Born approximation. Our numerical results are consistent with current experimental data. We also present the results for different centralities and the contributions from high order corrections.

Speakers: Qun Wang (University of Science and Technology of China), Shi Pu, Ren-jie Wang (USTC)

UPC-poster-qm2022.pdf

18:54 Predictions for future electron-hadron colliders using the Balitsky-Kovchegov equation

We present the latest predictions for several QCD processes at low-x in the color dipole picture which are of interest for current hadron-hadron and future electron-hadron colliders. The predictions are derived using the solution to the Balitsky-Kovchegov equation for proton and nuclear targets with the collinearly improved kernel and including the impact-parameter dependence. Two different approaches to the nuclear case are studied: a solution obtained using a newly proposed type of initial condition which represents the given nucleus and the solutions based on an initial condition representing a proton coupled to a Glauber-Gribov prescription to obtain dipole-nucleus amplitudes. We study the influence from the different energy evolutions of these two approaches in the following photo-nuclear processes: inclusive and diffractive DIS, coherent production of a J/psi meson in ultra-peripheral collisions at the LHC, and the deeply virtual Compton scattering. By comparison to the available data and to other CGC-inspired models, we demonstrate that the future measurements will be useful to discriminate among different approaches to saturation physics. These studies are therefore of interest for future measurements of QCD dynamics in the region of high parton densities to be performed at the LHC in ultra-peripheral collisions and at future electron-hadron colliders.

Speaker: Dagmar Bendova (Czech Technical University in Prague (FNSPE))

prez_Bendova_v2.pdf

18:58 First measurement of the forward rapidity gap distribution in pPb collisions at $\sqrt{s_{_{\mathrm{NN}}}} =$ 8.16 TeV with the CMS experiment

We present, for the first time at LHC energies, the forward rapidity gap spectra from proton-lead collisions for both pomeron-lead and pomeron-proton topologies. The analysis is performed over 10.4 units of pseudorapidity at a nucleon-nucleon center-of-mass energy of 8.16 TeV, i.e. almost 300 times higher than previous measurements of diffractive production in proton-nucleus collisions. For the pomeron-lead topology the EPOS - LHC predictions are a factor of two below the unfolded data but the model does give a reasonable description of the shape of the spectrum. For the pomeron-proton topology the EPOS - LHC , QGSJET II and HIJING generator predictions are all at least a factor of five below the data. This effect can be explained by a significant contribution of ultra-peripheral photoproduction events mimicking the signature of diffractive processes. The obtained data may be of significant help in understanding the high energy limit of QCD and modeling cosmic ray air showers.

Speaker: Michael Murray (The University of Kansas (US))

qm22-poster_murray_sosnov(1).pdf

19:02 Beyond Standard Model searches in ultraperipheral heavy-ion collisions with ATLAS

In heavy-ion collisions, the highly relativistic ions act as a strong source of electromagnetic radiation, enhanced by the large proton charge number $Z$. Ultra-peripheral collisions (UPC) offer a natural environment in which to observe the photon-initiated production of Beyond Standard Model (BSM) processes with QED couplings. One such process sensitive to BSM effects is light-by-light scattering. This process was directly observed for the first time in UPC events at the LHC by ATLAS. In this talk, the final ATLAS measurements of light-by-light scattering will be presented. These measurements are performed using the full Run-2 dataset which results in substantially reduced uncertainties compared to the previous measurements. They provide a precise and unique opportunity to investigate extensions of the Standard Model, such as presence of axion-like particles. Measurements of tau-pair production via two-photon scattering that investigate the anomalous magnetic moment of the tau lepton are also presented. This process is also potentially sensitive to BSM effects.

Speaker: Agnieszka Ewa Ogrodnik (AGH University of Science and Technology (PL))

QM2022Poster.pdf

19:06 Study of charmonium photoproduction in ultra-peripheral lead-lead collisions at LHCb

The LHCb detector is a single-arm forward spectrometer covering the pseudorapidity range 2 < 𝜂 < 5, designed for the study of particles containing bottom or charm quark. The study of exclusive vector meson photoproduction in ultra-peripheral lead-lead collisions is essential to understand physics at low Bjorken x. In particular, coherent J/ψ and ψ(2S) mesons are promising probes of nuclear shadowing due to their sensitivity to the nuclear parton distribution function of gluons.
In this presentation, we report the measurements of the differential coherent cross section productions as a function of transverse momentum and rapidity separately for J/ψ and ψ(2S) mesons, as well as the ratio of coherent ψ(2S) to J/ψ differential cross sections as a function of rapidity. in ultra-peripheral PbPb collisions at a nucleon-nucleon centre-of-mass energy of 5.02TeV. The J/ψ and ψ(2S) mesons are reconstructed in the dimuon decay channel using a data sample collected by the LHCb experiment in 2018, corresponding to an integrated luminosity of 228±10𝜇𝑏^(−1). The comparisons with theoretical predictions are also presented.

Speaker: Xiaolin Wang (South China Normal University (CN))

QM2022_oral-poster2015.pdf

19:10 Gluon shadowing and the role of the $c \bar c g$-Fock state in the diffractive photoproduction of $J/\psi$

We discuss the role of $c \bar c g$-Fock states in the diffractive photoproduction of J/ψ-mesons on heavy nuclei. We build on our earlier description of the process in the color-dipole approach, where we took into account the rescattering of $c \bar c$ pairs using a Glauber-Gribov form of the dipole-nucleus amplitude. The results of our calculations are compared to recent data on the photoproduction of J/ψ by the ALICE and LHCb collaborations. We argue that our results can be interpreted as a model calculation of shadowing in the gluon distribution of a heavy nucleus at a low factorization scale.

Speaker: Wolfgang Schaefer

QM_2022_WS.pdf

19:14 The study of v_2 as a function of multiplicity at different rapidities with PHENIX in AuAu at √s_NN = 200 GeV

The PHENIX experiment was operated at BNL-RHIC which collides heavy ions at
relativistic energy to create a quark-gluon plasma (QGP), in which quarks and gluons are deconfined. It is well known that the QGP produced in heavy ion collisions exhibits collective motion. In recent years, similar collective effect have been discovered in small systems at high energy collisions. This result attracts the attention to the multiple parton effect in nucleon such as Multi-Parton Interactions (MPI).

In this study, we attempt to observe the effect of multiple parton collisions in Au+Au at $\sqrt{s_{\textrm{NN}}}$ =200GeV. We assume that within an event selection with similar $N_{\textrm{part}}$, events with higher particle multiplicity would have more multiple parton collisions. In these events we would expect a large $v_2$ because of the larger energy density. In order to obtain $N_\textrm{part}$, we utilize the Zero Degree Calorimeter (ZDC) which detects the energies of spectator-neutrons. The particle multiplicity is measured in different rapidity ranges, with the Beam Beam Counter (BBC) at 3.1 < |η| < 3.9 and the Central Arm Tracking (CNT) at |η| < 0.35. In this poster, we will present the multiplicity dependence of
$v_2$ for several different ZDC selections. We also will discuss the rapidity dependence and the possible bias on the measurement.

Speaker: Ms Runa Takahama (Nara Women's University)

QM2022poster_Runa.pdf

19:18 Identified hadron spectra and baryon stopping in $\gamma+\rm{Au}$ collisions at STAR

Photonuclear collisions are one of the simplest processes that can happen in a heavy-ion collision. They occur when one nucleus emits a quasi-real photon which interacts with the other colliding nucleus, similar to an $e+A$ collision except that the photon tends to have a much smaller virtuality. Photonuclear collisions can be used to study bulk properties of the medium such as collectivity due to initial-state effects and hadron chemistry. Results are presented for identified $\pi^\pm$, $K^\pm$, and $p(\bar{p})$ spectra in photonuclear collisions at STAR for $\rm{Au}\rm{+}\rm{Au}$ collisions at $\sqrt{s_{NN}} = 54.4~\rm{GeV}$. Significant baryon stopping and rapidity asymmetry is observed at low transverse momentum, which could indicate the existence of a baryon junction within the nucleon, a nonperturbative Y-shaped configuration of gluons which carries the baryon number and is attached to all three valence quarks. Measuring the same spectra using the 2019 $\rm{Au}\rm{+}\rm{Au}$ dataset at $\sqrt{s_{NN}} = 200~\rm{GeV}$ shows how these effects change as a function of beam energy. Measurements of particle spectra and their rapidity dependence in photonuclear events will give insight into the origin of small-system collectivity, the gluon structure of the nucleon and will help inform future measurements using particle identification at the Electron Ion Collider.

Speaker: Nicole Lewis (Brookhaven National Laboratory)

Nicole_Lewis_QM2022_poster.pdf

19:22 Search for elliptic azimuthal anisotropies in photon-proton and pomeron-Pb interactions with ultraperipheral pPb collisions with the CMS experiment

Since 2011 a wide variety of measurements suggest the existence of strong collectivity in collisions of small systems such as proton-proton (pp) and proton-nucleus (pPb) with hydrodynamic models and gluon saturation in the initial state as two theory alternatives showing consistency with the observations. These results raise the question as to whether such phenomena may be present in even smaller systems. Just recently the ATLAS, ALEPH, and ZEUS collaborations have extended the studies to photon-Pb, electron-electron (ee), and electron-proton (ep) systems respectively. This talk will summarize the latest CMS results on the study of long-range particle correlations extended to photon-proton and pomeron-lead interactions using pPb collisions at a nucleon-nucleon center-of-mass energy of 8.16 TeV. Such interactions provide unique initial conditions with event multiplicity lower than in pp and pPb systems but comparable with ee and ep systems.

Speaker: Javier Alberto Murillo Quijada (Universidad de Sonora (MX))

jam_QM_abr_2022.pdf

18:30 → 19:30 Poster Session 2 T13

18:30 The evolution of electromagnetic fields in relativistic heavy-ion collisions

The electromagnetic fields produced by non-central heavy ion collisions are extremely powerful and give rise to a plethora of fascinating subjects in strongly interacting matter. Their evolution is a significant and unresolved issues. Because the relaxation time of the hot QCD matter to the electromagnetic fields is comparable with the lifetime of external electromagnetic field, we question, for the first time, the use of the Ohm’s law directly to compute the Faraday current and further induced magnetic field. By calculations employing the parton transport model combined with the solution of Maxwell's equations, we focus on the generation of the induced electric current and examine the validity of Ohm's law. We find that the electric current builds from zero and then relaxes towards the value given by Ohm's law. The relaxation time is not so short that can be neglected. The real Faraday current is much lower than expected. And this significantly suppresses the induced magnetic field. We call this incomplete electromagnetic response.In addition, we will present recent results about the electromagnetic evolution in the pre-equilibrium stages after the collisions. Also, we discuss the formation time of quarks to the electromagnetic development.

Speaker: Zeyan Wang (Tsinghua University)

18:34 Multi-messenger constraints on heavy-ion collision dynamics with hadrons and photons

In this talk, we present a study of direct photons in relativistic nuclear collisions, along with the production of hadrons, from RHIC Beam Energy Scan (BES) to LHC energies. Thermal photons are soft and penetrating probes of the strongly-coupled nuclear matter created in relativistic heavy-ion collisions. Their spectrum and momentum anisotropies remember the QGP’s chemistry evolution and its dynamical expansion. Using medium profiles well-calibrated with hadronic data at LHC energies, we highlight that photon observables can additionally reveal the chemical equilibration process and signal the formation of QGP in small systems [1]. At RHIC BES energies, a study of direct photon production in Au+Au collisions at 19.6 - 62.4 GeV will quantify the role of finite baryon chemical potential in thermal photon emission. Photon spectrum and anisotropic flow coefficients show strong sensitivity to the early-time dynamical initialization. This survey confirms photons as a powerful tool to elucidate QGP dynamics over a wide range of collision energies and serve as a necessary complement to hadronic measurements.

[1] C. Gale, J. F. Paquet, B. Schenke and C. Shen, "Multi-messenger heavy-ion physics," arXiv:2106.11216 [nucl-th]

Speaker: Jean-Francois Paquet (Duke University)

qm2022_jfpaquet.pdf

18:38 Prospects of dilepton and charmonium measurements with CBM experiment

The Compressed Baryonic Matter (CBM), currently under construction at the Facility for Anti-proton and Ion Research (FAIR) accelerator complex in Darmstadt, Germany aims to explore the QCD phase diagram at high baryon densities. Till date, no dilepton data have been collected in heavy-ion collisions at beam energies between 2A and 40A GeV. CBM aims to perform pioneering measurements of lepton pairs in nuclear collisions, employing both electron ($e^{+}e^{-}$) and muon ($\mu^{+}\mu^{-}$) channels, in the energy domain $\sqrt{s_{NN}}\sim$ 2.7 - 4.9 GeV, using unprecedented reaction rates of up to 10 MHz. The expected performance in the two channels are compared in terms of signal significances and background components. In particular the dimuon system will allow to employ charm as a probe of compressed baryonic matter via $J/\psi$ detection in p+A and A+A collisions.

Speaker: Mr Sayak Chatterjee (Bose Institute (Kolkata))

QM2022_s_chatterjee_poster_06042022.pdf

18:42 Photon-Jet correlations in central heavy-ion collisions with JETSCAPE

We present a comparison of observables related to photon-triggered jets for different collision energy systems, at LHC and RHIC energies, with the latest update of the JETSCAPE framework [1,2]. In heavy-ion collisions, multiple probes are used to study the properties of the Quark-Gluon Plasma (QGP). Photons can be produced at any stage of the heavy-ion collision. Since photons do not interact with the medium constituents, prompt photons that are produced early, directly in the hard sub-processes, can be used to differentially study the modification of the recoiling jet. In this work, we study photon-triggered jets through charged jet yields, momentum fraction correlations $(x_J)$, and angular $(\Delta \phi)$ correlations, using the JETSCAPE framework. We extend our previous work of $(x_J)$ and $(\Delta \phi)$ [3] with new high statistics runs, using the latest version of the multi-stage JETSCAPE framework. We use the corresponding isolation cut on the final state to identify the prompt-photons, to get a reasonable comparison with the experimental data. The same set of parameters tuned for single inclusive jet and leading hadron analysis, with a new virtuality dependent transport coefficient $\hat{q}$, are used in this calculation as well, with no refitting. For the first time, the study is done simultaneously for both RHIC and LHC energies. The comparison with experimental data for different collision systems and energies provides a wide-ranging, parameter-free, and independent verification of the multistage approach in heavy-ion collisions.

1. Putschke, J. H., et al. "The JETSCAPE framework." arXiv preprint arXiv:1903.07706 (2019).

2. Cao, Shanshan, et al. "Multistage Monte Carlo simulation of jet modification in a static medium." Physical Review C 96.2 (2017): 024909.

3. Sirimanna, C. (2021). Photon-jet correlations in p-p and Pb-Pb collisions using the JETSCAPE framework. PoS, HardProbes2020, 051. https://doi.org/10.22323/1.387.0051

Speaker: Chathuranga Sirimanna (Wayne State University)

PhotonJetCorrelations_Poster.pdf

18:46 Dilepton production at NLO and intermediate invariant mass observables

Because photons and dileptons are unlikely to interact after production within a quark-gluon plasma (QGP), they can probe the inner dynamics of this strongly interacting system. To leading order in the electromagnetic coupling and all orders in the strong coupling, the observable emission rates can be determined from the QCD vector channel spectral function. The resummed next-to-leading order (NLO) spectral function is intimately related to the Euclidean correlator, which can be estimated from continuum-extrapolated lattice data [1]. We report on two aspects of our theoretical investigation: i) we embed derived NLO dilepton rates (at $\mu_B = 0$) in viscous, relativistic hydrodynamical simulations of heavy ion collisions and focus our analysis on the invariant mass region $1 < M < 3$ GeV where QGP manifestations are expected to be prevalent, and ii) we generalize the perturbative calculation to non-zero baryon chemical potential $\mu_B$. In the first part, we show results for dilepton measurements at RHIC and LHC energies. In the second part, we report that the presence of $\mu_B$ not only modifies the quark distribution in the QGP, but also the thermal masses that control the necessary screening effects. While the latter has been examined for real photons [2], we present new results away from the light cone. This involves properly understanding how $\mu_B$ enters the strict NLO computation, the so-called LPM effect (at low invariant masses), and how to smoothly interpolate between the two regimes as originally advocated in Ref. [3]. These results enable predictions to be made for low-energy heavy ion experiments that will explore QGPs with net baryon content.

[1] G. Jackson and M. Laine, "Testing thermal photon and dilepton rates," JHEP 11, 144 (2019)
[2] H. Gervais and S. Jeon, "Photon Production from a quark-gluon-plasma at finite baryon chemical potential," Phys. Rev. C86, 034904 (2012)
[3] I. Ghisoiu and M. Laine, "Interpolation of hard and soft dilepton rates," JHEP 10, 083 (2014)

Speaker: Greg Jackson (INT, University of Washington)

GJ_April2022.pdf

18:50 Measurement of low-momentum direct photons in Au+Au collisions at 200 GeV

Direct photons are a useful probe to study the properties of QGP and the dynamic evolution of the collision system as they do not interact with the medium strongly. Low transverse momentum direct photons are believed to originate primarily from thermal radiation, however, calculations of thermal photon emission fall short in describing the measured direct photon yield and the anisotropy at the same time. The question is tied to the photon production mechanism in heavy ion collisions.

In this poster, more precise measurements of the direct photon momentum spectrum in the range of $0.8-10$ GeV/c from the high statistics data taken by the PHENIX experiment in 2014 is presented. The effective temperature of the system formed in such heavy-ion collisions is studied. In addition, direct photon production as a function of collision system size is analyzed, wherein a power law scaling behavior is observed. The extracted fit parameter to the scaling will put more constraints on the current theoretical models.

Speaker: Wenqing Fan (Lawrence Berkeley National Lab. (US))

QM2022_poster_wenqing_040722.pdf

18:54 Direct photon HBT correlations in pp and Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV measured with ALICE

The temperature and size of the quark-gluon plasma that is created in heavy-ion collisions are properties that are to be experimentally constrained. This can be done via direct photon Hanbury Brown and Twiss (HBT) measurements that are able to both quantify the excess of thermal photons as well as the size of the emitting source. In contrast to femtoscopic measurements of bulk particles, this measurement is more sensitive to earlier times in the systems evolution.

In the ALICE experiment, photons can be reconstructed either by using the calorimeters or via conversions in the detector material. Conversions benefit from an excellent energy resolution and are able to provide direct photon measurements down to very low momentum. For HBT correlations, the detector setup can be exploited to combine a conversion photon with a calorimeter photon, such that near zero opening angles are measured which is where the main signal is situated.

The poster presents the first results on direct photon HBT correlations in pp and Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV by ALICE. Although this is a challenging measurement with the existing LHC Run 2 data, fits of the signal in Pb--Pb collisions can be used to provide constraints of the direct photon excess and size of the source.

Speaker: Mike Henry Petrus Sas (Yale University (US))

msas_poster_DirectPhotonHBT_v4.pdf

18:58 Enhancement of photon momentum anisotropies during the late stages of relativistic heavy-ion collisions

We present a consistent photon production calculation from hadronic cross sections, including bremsstrahlung and 2-to-2 reactions, matching the usually employed thermal rates [1]. Using the hadronic transport approach SMASH as the afterburner for the hadronic stage at RHIC and LHC energies, we find a significant increase in the calculated momentum anisotropies of these photons due to microscopic non-equilibrium dynamics. This enhancement is found in comparison to standard calculations, which rely on the folding of equilibrium rates to a hydrodynamical evolution. Once combined with photons produced above the particlization temperature in the hydrodynamical evolution, the differences between the two approaches are modest regarding $p_\perp$-differential spectra, but are clearly noticeable at low $p_\perp$ for the elliptic flow: non-equilibrium dynamics enhance the photon $v_2$ below $p_\perp \approx 1.5$ GeV.

[1] A. Schäfer, O. G-M., J-F. Paquet, H. Elfner, and C. Gale. arXiv: 2111.13603

Speaker: Oscar Garcia-Montero (Institut für Theoretische Physik, Johann Wolfgang Goethe-Universität)

QM2022Poster.pdf

19:02 Anomalous enhancement of dilepton production due to diquark fluctuations in dense quark matter

The high-statistics search for high baryon-density matter at relatively low temperature comes to be possible by the recent experiments using heavy-ion collision (HIC), which may realize the color superconductivity (CSC): Such experiments include the beam-energy scan program at RHIC, and HADES and NA61/SHINE collaborations as well as those to be performed in future experimental facilities such as FAIR, NICA and J-PARC-HI. In the present report, we calculate the effect of diquark correlations or diquark fluctuations, which persist even away from the critical temperature of CSC, on the dilepton production rate using the two-flavor NJL model. In the calculation, we consider the Aslamazov-Larkin, Maki-Thompson and Density of States terms due to diquark fluctuations, which are known to give rise to anomalous excess of electric conductivity in metals in the vicinity of the critical temperature of superconductivity. The results show that the dilepton production rate due to the diquark fluctuation is anomalously enhanced in the low energy region even at 1.5 times the critical temperature. We shall explain the physical mechanism of such production process and suggest that this enhancement would be detectable as the experimental signal for CSC in the HIC experiments.

Speaker: Toru Nishimura

QM2022_nishimura.pdf

19:06 Significance estimation for virtual photon polarization measurement with dimuons at ALICE

An ultra-intense magnetic field is expected to be created in relativistic heavy-ion collisions with an intensity up to 10$^{15}$ T. These strong magnetic fields are predicted to produce various nonlinear QED behaviors and other interesting phenomena, such as the chiral magnetic effect and quark synchrotron radiation. However, such a magnetic field has not yet been detected experimentally. The decay plane of dileptons from virtual photons is predicted to be anisotropic in the presence of an ultra-intense magnetic field and thus carry information about the existence of the magnetic field.

In this poster, numerical QED calculations for virtual photon polarization will be presented. Moreover, feasibility studies for virtual photon polarization measurements using dimuons with $p_{\rm T}$ > 4 GeV/$c$ reconstructed by the ALICE muon spectrometer in Pb--Pb collisions at $\sqrt{s_{\rm NN}} =$ 5.02 TeV and 5.5 TeV will be reported. The different sources of background will be explained, and projections for Run 3 with the new Muon Forward Tracker will be shown.

Speaker: Kento Kimura (Hiroshima University (JP))

kimura_QM22_Poster.pdf

19:10 Dynamical broadening of vector-meson spectral functions

We reconstruct effective spectral functions of the $\rho$-meson in different scenarios via lifetime analysis using the hadronic transport SMASH (Simulating Many Accelerated Strongly-interacting Hadrons). The theoretical interest in the behavior of in-medium spectral functions lies in the expected restoration of chiral symmetry at high energy densities, which may be accessed experimentally by studying dilepton mass spectra in heavy-ion collisions. Within SMASH, the phase space of all particles is available at all times, as well as information on interactions, allowing for a direct assessment of particle lifetimes and the mass distributions. Our reconstruction of the spectral function consists in using the total width — considering both decays and collisions — as input for a Breit-Wigner ansatz. The broadening of the spectral function in a thermalized system is shown to be consistent with model calculations [1], and the dependence of total width on local hadron density is provided. This broadening develops dynamically, since SMASH relies only on vacuum properties of resonances as an input. On the other hand, we present the effective $\rho$-meson spectral function for the dynamical evolution of heavy-ion collisions, finding a clear correlation of broadening to system size. Furthermore, we discuss the difference in the results between the thermal system and full collision dynamics, which may point to out-of-equilibrium effects. The results shown in this work are of interest to distinguish dynamical broadening from additional genuine medium-modified spectral functions.

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[1] R. Rapp and J. Wambach, Eur. Phys. J. A 6 (1999), 415-420 [arXiv:hep-ph/9907502].

Speaker: Renan Hirayama (FIAS)

QM2022_Hirayama_poster.pdf

19:14 Scaling properties of direct photons in heavy ion collisions

A recent analysis from the PHENIX collaboration on direct photon production yield in heavy ion collisions has shown a universal, within experimental uncertainties, multiplicity scaling, in which the photon $p_T$-spectra for transverse momenta up to 2 GeV/c are scaled with charged-hadron pseudorapidity density at midrapidity raised to the power $\alpha=1.25$. This low-$p_T$ scaling suggests that the main photon sources contributing to it, could be similar across beam energies. On the other hand, particle production in large and small system collisions, including direct photons, exhibits geometrical scaling in a similar $p_T$ range. The geometric scaling follows from gluon saturation and collision geometry. In particular, the direct photon spectra obtained for large and small system collisions at different centrality classes and various beam energies depend on a specific combination of number of participants, beam energy, and saturation scale - rather than on all these three variables separately. In our presentation, we show that the multiplicity and geometric scaling laws for direct photons are interconnected and discuss physical conditions needed to relate one to another. This interrelation may help us better understand the direct photon production during the early evolution of the matter produced in heavy ion collisions.

Speaker: Dr Vladimir Khachatryan (Duke University, Stony Brook University)

QM2022_GS_poster_VK_MP.pdf

19:18 Centrality dependence of dilepton production via photon-photon fusion processes from Wigner functions of photons in nuclei

A new complete method, based on the Wigner distributions of photons, how to calculate differential distributions of dileptons created via photon-photon fusion in semicentral ($b<2R_{AA}$) AA collisions is reviewed [1]. The formalism is used to calculate different distributions of invariant mass, dilepton transverse momentum and acoplanarity for different regions of centrality. The results of calculation are compared with recent STAR, ALICE and ATLAS experimental data. Very good agreement with the data is achieved without free parameters and without including additional mechanisms such as a possible rescattering of leptons in the quark-gluon plasma.

We will also refer to our earlier paper [2] where we discussed competition with thermal radiation. We verify that the combination of photon fusion, thermal radiation and final-state hadron decays gives a fair description of the low-$P_T$ invariant-mass as well as $P_T$ spectra as recently measured by the STAR collaboration in $\sqrt{s_{NN}}=200$ GeV Au+Au collisions for different centrality classes.

[1] Mariola Kłusek-Gawenda, Wolfgang Schaefer, Antoni Szczurek,
Phys. Lett. B814 (2021) 136114.

[2] Mariola Kłusek-Gawenda, Ralf Rapp, Wolfgang Schaefer, Antoni Szczurek,
Phys. Lett. B790 (2019) 339-344.

Speaker: Mariola Klusek-Gawenda (Institute of Nuclear Physics Polish Academy of Sciences)

MKG_QM2022_poster_Wigner.pdf

19:22 Dielectron production in high-multiplicity pp collisions at 13TeV with ALICE

Dielectron production in high-multiplicity pp collisions at $\sqrt{s}$ = 13 TeV with ALICE

Dielectron production is a powerful tool to investigate the properties of the quark-gluon plasma created in relativistic heavy-ion collisions, as they carry information about the temperature of the medium and its space-time evolution without any distortion due to final-state interactions. Dielectron measurements in pp collisions serves as reference for heavy-ion studies since no medium effect is expected. As of now, results of such measurements at the LHC and the RHIC are compatible with expected hadron decays and no significant sign of medium modification has been reported. However in recent studies, collective behavior of hadrons has been seen in high-multiplicity pp and p-Pb collisions at the LHC and the RHIC similarly to previous observations in heavy-ion collisions. If a medium is created in such small colliding systems, it should give rise to an additional contribution of electromagnetic radiation in the direct photon spectrum. For each real direct photon production mechanism, an associated process producing a virtual photon which converts to a low mass dilepton exists as well. These processes, referred to as internal conversions, allow for the measurement of virtual direct photons with better signal to background ratio compared to real direct photon measurement at low transverse momentum, which is where the thermal radiation signal sits.
In this poster, the measurement of virtual photon production in minimum-bias and high-multiplicity pp collisions at $\sqrt{s}$ = 13 TeV will be presented. The analysis uses the full ALICE Run 2 dataset, and the results are compared with pQCD calculations when possible.

Speaker: Hikari Murakami (University of Tokyo (JP))

2022-04-01-QM22_poster_v4_murakami.pdf

18:30 → 19:30 Poster Session 2 T14_1

18:30 Quantify phenomenological effects of causality constraints in the hydrodynamic description of relativistic heavy-ion collisions

We study theoretical uncertainties in the hydrodynamic description of relativistic heavy-ion collisions by examining the full nonlinear causality conditions [1] and quantifying their effects on flow observables [2]. The causality conditions impose physical constraints on the maximum allowed values of inverse Reynolds numbers during the hydrodynamic evolution. We develop a new numerical scheme to impose the necessary and sufficient causality conditions on individual fluid cells during the evolution. We find that the necessary causality condition can effectively stabilize event-by-event hydrodynamic simulations with large pressure gradients. Performing systematic simulations with and without the necessary and sufficient causality conditions, we quantify their effects on flow observables in p+Au and Au+Au collisions at the top RHIC energy and p+Pb and Pb+Pb collisions at LHC. Their impacts on the global Bayesian extraction of the QGP transport properties will be discussed.

[1] F. S. Bemfica, M. M. Disconzi, V. Hoang, J. Noronha, and M. Radosz, “Nonlinear Constraints on Relativistic Fluids Far from Equilibrium,‘’ Phys. Rev. Lett. 126, 222301 (2021)
[2] C. Chiu and C. Shen, “Exploring theoretical uncertainties in the hydrodynamic description of relativistic heavy-ion collisions,” Phys. Rev. C 103, 064901 (2021)

Speaker: Cheng Chiu (Wayne State University)

Causality Presentation - QM 2022.pdf

Cheng_Chiu_Quark_Matter_2022_Recording.mp4

18:34 Probing initial baryon stopping and baryon diffusive transport with rapidity-dependent directed flow of identified particles

We develop a new parametric 3-dimensional initial condition for low-energy heavy-ion collisions based on collision geometry for a multistage hybrid framework. The longitudinal structure of the collision profile is constrained by rapidity-dependent experimental measurements, especially the directed flow of pions and protons (i.e., $v_1(y)$). We introduce a baryon stopping parameter which controls the initial rapidity distribution of baryon charge after the nuclei interpenetration, and the amount of energy and momentum deposited from the incoming nucleons into the produced quark-gluon plasma. The energy-momentum and net baryon charge conservation impose correlations among the initial energy, baryon distributions, and longitudinal flow.

The (3+1)-dimensional hydrodynamic evolution shows that the baryon density distribution and baryon diffusion can change the sign of identified particles’ directed flow coefficients. Furthermore, the rapidity-dependent $v_1(y)$ is affected by the longitudinal diffusive baryon transport and flow velocity. We further quantify how the rescattering between mesons and baryons affect their $v_1(y)$ slopes in the hadronic stage. Finally, we will present a systematic study of $v_1(y)$ in Au+Au collisions at different centrality classes, various beam energies, and additional identified species (kaons and lambdas) to test our hybrid model. Our results shed light on the initial baryon stopping and the hydrodynamic baryon transport, and are relevant for the model-to-data comparison in the BES-II.

Speaker: Lipei Du (McGill University)

QM 22 - L Du.pdf

18:38 Dynamical modeling of particle production, flow correlations, and baryon distributions in heavy-ion collisions from GeV to TeV

Building upon Ref. [1], we present an improved three-dimensional dynamical initialization model for heavy-ion collisions, implementing local energy-momentum conservation and baryon charge fluctuations at string junctions [2]. These improvements lead to an excellent description of the charged hadron and net proton rapidity distributions in Au+Au collisions from 7.7 to 200 GeV [3]. Based on these results, we quantify the amount of baryon stopping at the initial impact and baryon transport during the hydrodynamic evolution and hadronic scattering phases. The effects of strangeness neutrality and the finite overlap time at low collision energies on hadronic flow observables are quantified. We further expand the model description to asymmetric p+Al and (p, d, 3He, Cu)+Au collisions at the top RHIC energy and p+Pb and PbPb collisions at LHC energies. The particle rapidity distributions in asymmetric collision systems can provide additional constraints on modeling the early-time longitudinal dynamics. Enabled by this 3D framework, we quantify the rapidity (de)correlation of anisotropic flow in large and small systems.

[1] C. Shen and B. Schenke, "Dynamical initial state model for relativistic heavy-ion collisions," Phys. Rev. C97 (2018), 024907
[2] D. Kharzeev, “Can gluons trace baryon number?,” Phys. Lett. B 378, 238 (1996)
[3] C. Shen, "Dynamic modeling for heavy-ion collisions," arXiv:2108.04987 [nucl-th]

Speaker: Chun Shen (Wayne State University)

Shen_QM2022_poster.pdf

18:42 Accuracy vs. precision: the importance of theoretical uncertainties in Bayesian constraints of the quark-gluon plasma's properties

Determining QCD properties via experimental observations is an
essential part of the heavy-ion program, and a crucial aspect of any
such study is an accurate assessment of uncertainty. This uncertainty
comes not only from experiments but also from theoretical modeling.
Bayesian inference methods provide an ideal framework for a systematic
treatment of these sources of uncertainty and an accurate
determination of QGP properties. We present a Bayesian Model
Averaging framework to account for different sources of theoretical
uncertainty [1] and show results obtained from comparison to RHIC and
LHC measurements. We further show how including additional deuteron
observables affect the posterior constraints. Finally, we discuss the
choice of observables to use in an analysis, especially the benefits
and risks of including observables with strong constraining power but
also significant sensitivity to theoretical uncertainty.

[1] D. Everett et al. [JETSCAPE], Phenomenological constraints on
the transport properties of QCD matter with data-driven model
averaging, Phys. Rev. Lett. 126, 242301 (2021)

Speaker: Matthew Luzum

LuzumQM2022.pdf

18:46 A Systematic Study of In-Medium Hadronization of Jet Showers with JETSCAPE and Hybrid Hadronization

“Hybrid Hadronization” is a Monte Carlo package that hadronizes systems of partons. It smoothly combines quark recombination, applicable when distances between partons in phase space are small, and string fragmentation appropriate for dilute parton systems, following the picture outlined by Han et al. [PRC 93, 045207 (2016)]. Hybrid Hadronization can be applied to a variety of systems from $e^++e^-$ to A+A collisions. It takes systems of partons and their color flow information, for example from a Monte Carlo parton shower generator, as input. In addition, if for A+A collisions a thermal background medium is provided, the package allows to sample thermal partons that contribute to hadronization. Hybrid Hadronization is available for use as a standalone code and is part of JETSCAPE since the 2.0 release. In this presentation we review the physics concepts underlying Hybrid Hadronization. We then quantify the effects that an ambient medium has on the hadronization process of jet showers. We focus in particular on the dependence of medium effects on the flow and size of the medium. Jet showers are simulated in JETSCAPE either in vacuum or in an ambient medium. We systematically vary parameters like jet energy, jet flavor, medium size, medium flow velocity, medium flow direction, and orientation of the hadronization hypersurface. Among other observables we compute hadron fragmentation functions, ratios of identified hadrons, properties of clustered jets, and jet shapes. We see clear signatures of the medium interacting with jets during hadronization. Our results clarify the effect we expect from in-medium hadronization of jets on observables like fragmentation functions, hadron chemistry, jet shape, or acoplanarity. They could be useful to further constrain our understanding of the interaction of jet showers in the parton phase extracted from experimental data.

Speaker: Arjun Sengupta (Texas A & M University)

Quark_Matter_2022_HH_Study_Sengupta.pdf

18:50 Study of identified hadrons in Au+Au collisions at $\sqrt{s_{NN}}$ = 27 and 54.4 GeV using the STAR detector at RHIC

Quantum Chromodynamics (QCD), the theory of strong interactions, predicts that at sufficiently high temperature and/or high energy density normal nuclear matter converts into a deconfined state of quarks and gluons, known as the Quark-Gluon Plasma (QGP). To investigate the phase diagram of QCD matter, the Relativistic Heavy Ion Collider (RHIC) started the first phase of the Beam Energy Scan (BES-I) program in 2010. Under the BES-I program, Au+Au collision data were taken at $\sqrt{s_{NN}}$ = 7.7 to 62.4 GeV in collider mode. In 2017, a high statistics dataset from Au+Au collisions at $\sqrt{s_{NN}}$ = 54.4 GeV was recorded by the STAR experiment to fill the energy gap between 39 and 62.4 GeV. The success of the BES-I program justified the second phase of Beam Energy Scan (BES-II) with higher statistics and detector upgrades. The first collider energy from BES-II was 27 GeV, which was recorded in 2018. The spectra of identified hadrons are essential to study bulk properties, such as integrated yield (dN/dy), average transverse momenta ($\langle p_{T} \rangle$), particle ratios, and freeze-out parameters of the medium produced. The difference in mean transverse mass ($\langle m_{T} \rangle$) and rest mass ($m_{0}$), i.e., $\langle m_{T} \rangle$ - $m_{0}$, as a function of $\sqrt{s_{NN}}$ can shed light on the formation of a mixed phase of a QGP and hadrons during the evolution of the heavy-ion system.

In this talk, we will present the spectra of identified hadrons ($\pi^{\pm}$, $K^{\pm}$, p and $\bar{p}$) at mid-rapidity in Au+Au collisions at $\sqrt{s_{NN}}$ = 27 and 54.4 GeV. The midrapidity yields of identified hadrons show the expected signatures of large baryon stopping region at lower energies and the dominance of the pair production mechanism at higher energies. The constant value of $\langle m_{T} \rangle$ - $m_{0}$ around RHIC BES energies could be interpreted as the formation of a mixed phase. The centrality dependence of dN/dy, $\langle p_{T} \rangle$, particle ratios, chemical freeze-out, and kinetic freeze-out parameters will also be presented, and their physics implications will be discussed. The rapidity dependence of the identified hadron spectra will also be presented from Au+Au collisions at $\sqrt{s_{NN}}$ = 27 GeV to understand the rapidity dependence of freeze-out properties.

Speaker: Matthew Harasty (University of California, Davis)

QM_2022_Harasty_4April2022_v3.pdf

18:54 Directed flow of identified particles in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 19.6 and 14.6 GeV

Determination of equation of state for nuclear matter at high baryon density region is one of the most important motivations for RHIC Beam Energy Scan program. Directed flow ($v_{1}$), which is the first harmonic coefficient in the Fourier expansion of the final state azimuthal distribution of produced particles relative to the collision reaction plane, is one of good probes to early stage of collision dynamics for its high sensitivity.

STAR Beam Energy Scan program phase I (BES I) covers collision energies from $\sqrt{s_{\mathrm{NN}}}$ = 7.7 GeV to 200 GeV. We observed that $v_{1}$ slopes ($dv_{1}/dy|_{y=0}$) at mid-rapidity region for net-proton and net-$\Lambda$ show a minimum value when collision energy is around $\sqrt{s_{\mathrm{NN}}}$ = 10-20 GeV. The slope of $\phi$ mesons has a hint of sign change between 11.5 and 14.5 GeV. With large statistics from BES II, we will present $v_{1}$ results of pions, kaons, protons, and $\phi$ mesons. The corresponding $v_1$ slopes will be studied as a function of centrality. The data will constrain the model calculations and offer information about possible first order QCD phase transition.

Speaker: Zuowen Liu

QM2022_poster_presentation_Zuowen.pdf

18:58 Spheroid expansion and freeze-out geometry heavy-ion collisions in the few-GeV energy regime

Models based on statistical hadronisation were found to be applicable for ultra-relativistic heavy-ion experiments where high nucleon transparency is present. It is not well established whether such models are also valid for the part of the QCD diagram where the collision energies are lower (of the order of a few GeV). In our previous work, by implementing spherical fireball geometry and expansion shape corresponding to the few-GeV regime into the THERMal heavy IoN generATOR (THERMINATOR), it was possible to replicate experimental distributions of transverse-mass with satisfactory accuracy. However, rapidity distributions came out narrower than measured experimentally, which suggests a deviation from the spherical symmetry. In our current work, we introduce the spheroidal symmetry of the fireball, which in turn allows to reproduce well the rapidity distributions of the most abundant particles measured by the HADES collaboration in Au+Au 10% central collisions at $\sqrt{s_{\rm NN}}= 2.4$ GeV. We use measured particle spectra and femtoscopic correlations to constrain the parametrization of the shape and the expansion profile of the fireball. Moreover, in the light of recent publications analysing this topic, we extend our study to discuss different formulations of the statistical hadronisation models, aiming at a better understanding of the statistical nature of particle production in heavy-ion collisions.

Speaker: Jędrzej Kołaś

Spheroild_Expansion_QM_kolas_poster.pdf

19:02 Relativistic Resistive Magneto-Hydrodynamics in High-Energy Heavy-Ion Collisions: Hadron Distribution and Flow

In high-energy heavy-ion collisions, strong and transient electromagnetic fields (~$10^{14}~[\rm{T}]$) are induced inside generated hot and dense QCD medium.
The space-time evolution of the electromagnetic field in electrically conducting nuclear matter is completely different from that of vacuum; the lifetime of it becomes much longer than that in the vacuum. Also, the electrical conductivity of the QCD matter plays an important role for space and time dependencies of an electromagnetic field [1].

Several studies of the non-resistive QCD matter have been performed in a relativistic ideal magneto-hydrodynamic framework [2]. Usually, initial electric fields produced by collision spectators are neglected because they grow $-\vec{v}\times\vec{B}$ instantaneously due to the infinite electrical conductivity.
However, for realistic analyses of the consequences of the existence of an electromagnetic field in high-energy heavy-ion collisions, electrical conductivity is important. In particular, in anisotropic collision systems such as Cu + Au collisions($\sqrt{s_{NN}} = 200~[\rm{GeV}]$), the effect of electrical conductivity can be clearly found [3]. A numerical framework with the electrical conductivity of QCD matter is indispensable, for the investigation of the effect of electromagnetic fields on the final hadron distributions and flows in high-energy heavy-ion collisions.

We present a first study of the effect of the electromagnetic fields on physical observables, utilizing a newly developed relativistic resistive magneto-hydrodynamics (R2MHD) simulation code. We check our code, using several test problems; 1D shock tube test and 2D Resistive Rotor test. In addition, our numerical results of magnetized Bjorken flow and Rotor test in Milne coordinates with high electrical conductivity are consistent with the ideal relativistic magneto-hydrodynamics [4].
We show numerical results of Au +Au ($\sqrt{s_{NN}} = 200~[\rm{GeV}]$) and Cu + Au ($\sqrt{s_{NN}} = 200~[\rm{GeV}]$) at RHIC. We focus on the rapidity odd profile of directed flow $v_1$, charge-dependent splitting of elliptic flow $v_2$ and so on.

[1] K. Tuchin, Phys. Rev. C $\textbf{88}$, no.2, 024911 (2013).
[2] G. Inghirami, M. Mace, Y. Hirono, L. Del Zanna, D. E. Kharzeev and M. Bleicher, Eur. Phys. J. C $\textbf{80}$, no.3, 293 (2020).
[3] Y. Hirono, M. Hongo and T. Hirano, Phys. Rev. C $\textbf{90}$, no.2, 021903 (2014).
[4] G. Inghirami, L. Del Zanna, A. Beraudo, M. H. Moghaddam, F. Becattini and M. Bleicher,Eur. Phys. J. C $\textbf{76}$, no.12, 659 (2016).

Speaker: Mr Kouki Nakamura (Nagoya Univ., Hiroshima Univ.)

QM2022_NAKAMURA.pdf

19:06 Hydrodynamic description of heavy ion collisions using the EKRT model with dynamical decoupling

In the EKRT model for ultrarelativistic heavy-ion collisions, we compute the initial fluctuating QCD-matter energy densities from NLO pQCD and saturation, and describe the subsequent space-time evolution of the system with dissipative fluid dynamics, event by event [1,2,3]. This model agrees remarkably well with the low-$p_T$ flow observables measured in Pb+Pb and Xe+Xe collisions at the LHC, and Au+Au collisions at RHIC, in the centrality range 0-50 %. To extend this validity range further, and to perform a simultaneous comparison of the centrality dependence of hadronic multiplicities, $p_T$ spectra and various flow correlators against the latest LHC and RHIC data, we have now improved the fluid-dynamics part of the model significantly [4]. An essential new feature is the dynamical freeze-out that accounts both for a local Knudsen-number based criterion, and for a global criterion set by the overall size of the system. Importantly, our model is based purely on hydrodynamics also in the hadronic phase, so that a continuous parametrization of the temperature dependence of transport coefficients is possible. Adding a non-zero bulk viscosity and taking the chemical freeze-out at $T = 155$ MeV, we obtain a good simultaneous description of the average $p_T$ and the proton multiplicity, and at the same time we show that the setup clearly improves the agreement with the $v_n\{2\}$ LHC measurements in peripheral collisions while maintaining the earlier good agreement with other flow correlations. We also show that bulk viscosity together with the dynamical freeze-out clearly improves the quantitative description of the recently measured $p_T, v_n$ correlations.

[1] H. Niemi, K. J. Eskola and R. Paatelainen, Phys. Rev. C 93, no.2, 024907 (2016)
[2] H. Niemi, K. J. Eskola, R. Paatelainen and K. Tuominen, Phys. Rev. C 93, no.1, 014912 (2016)
[3] K. J. Eskola, H. Niemi, R. Paatelainen and K. Tuominen, Phys. Rev. C 97, no.3, 034911 (2018)
[4] H. Hirvonen, K. J. Eskola, H. Niemi, in preparation

Speaker: Henry Hirvonen (University of Jyväskylä)

HirvonenQM2022.pdf

19:10 Longitudinal flow decorrelation by hydrodynamic fluctuations and event-shape engineering in Xe+Xe collisions

In this talk, we analyze the factorization ratio $r_n(\eta_p^a,\eta_p^b)$ in Xe+Xe and Pb+Pb collisions [1] using event-shape engineering within the integrated dynamical model [2,3] constructed of the Monte-Carlo Glauber model for the initialization, rfh for 3+1D relativistic fluctuating hydrodynamics with hydrodynamic fluctuations [2], and JAM for hadronic cascades [4]. We also address recent topics of the fluctuating hydrodynamic about the correction of the fluctuation-dissipation relation [5] and the renormalization of the equation of state.

To precisely determine the properties of the matter created in heavy-ion collisions---such as the viscosity and diffusion coefficients, and the finite-$\mu_B$ equation of state---, it is important to constrain the model uncertainties that affect the collective dynamics such as the initialization models and the hydrodynamic fluctuations. The comprehensive description of collective flows and their correlations, including the factorization ratios, mixed correlations, and symmetric and asymmetric cumulants, is the key to constraining the model parameters.

We here focus on the longitudinal factorization ratio $r_n(\eta_p^a,\eta_p^b)$ [6] which is a useful tool to understand and constrain the longitudinal fluctuations generated by initialization models and hydrodynamic fluctuations. We have shown that both the hydrodynamic fluctuations and the initial longitudinal fluctuations are needed to explain the centrality dependence of $r_2(\eta_p^a, \eta_p^b)$ in our previous study [7]. To discern the effect of the hydrodynamic fluctuations more clearly from that of the other fluctuations, it is a great opportunity to investigate the longitudinal decorrelation observed in the Xe+Xe collisions [1], where the deformation of the colliding nuclei plays a non-trivial role. We first analyze the eccentricities $\varepsilon_n$ and initial decorrelations $r_n^\varepsilon(\eta_s^a,\eta_s^b)$ calculated from initial entropy densities for Xe+Xe collisions with/without deformation and for Pb+Pb collisions. We find the effect of the deformation on the decorrelations $r_n^\varepsilon$ in the central collisions and further analyze them by classifying the events by $\varepsilon_n$. We then perform the event-by-event simulations with and without hydrodynamic fluctuations and calculate $r_n(\eta_p^a,\eta_p^b)$. We discuss the effects of the hydrodynamic fluctuations by classifying the events by the magnitude of flow vectors $q_n$.

[1] G. Aad et al. (ATLAS Collaboration), Phys. Rev. Lett. 126 (2021) 122301.
[2] K. Murase, T. Hirano, Nucl. Phys. A 956 (2016) 276-279.
[3] A. Sakai, K. Murase, T. Hirano, Phys. Rev. C 102 (2020) 6, 064903.
[4] Y. Nara, N. Otuka, A. Ohnishi, K. Niita, S. Chiba, Phys. Rev. C 61 (2000) 024901.
[5] K. Murase, Annals Phys. 411 (2019) 167969.
[6] V. Khachatryan, et al. (CMS Collaboration), Phys. Rev. C 92 (3) (2015) 034911.
[7] A. Sakai, K. Murase, T. Hirano, preprint arXiv:2111.08963 [nucl-th].

Speaker: Koichi Murase (Kyoto University)

20220406-murase-QM2022-XeXeDecorrelation+Backup.pdf

20220406-murase-QM2022-XeXeDecorrelation+Backup-v2.pdf

19:14 $p_T$ dependent correlation between initial spatial anisotropy and final momentum anisotropy in heavy ion collisions

The initial spatial asymmetry of the overlapping zone between two colliding nuclei in heavy ion collisions gives rise to the final momentum anisotropy characterized by the anisotropic flow parameters. The efficiency of conversion from initial spatial anisotropy ($\epsilon_n$) to final momentum anisotropy ($v_n$) is quantified by the linear correlation between $\epsilon_n$ and $v_n$. We have studied the transverse momentum, collision centrality and beam energy dependence of the correlation for charged particles using a hydrodynamical model framework [1]. The $p_T$ dependent correlation shows a strong dependence on the mass and $p_T$ of the emitted particles. In addition, we see that the relative fluctuation in anisotropic flow is strongly sensitive to the value of shear viscosity of the medium whereas the correlation coefficient shows no such dependence on $\eta/s$.
Reference:
[1] S.Thakur, S.K.Saha, P.Dasgupta, R.Chatterjee and S.Chattopadhyay,"$p_T$ dependence of the correlation between initial spatial anisotropy and final momentum anisotropies in relativistic heavy ion collisions",Nucl. Phys. A \textbf{1014} (2021), 122263
doi:10.1016/j.nuclphysa.2021.122263
[arXiv:2101.09998 [nucl-th]].

Speaker: Mr Sumit Kumar Saha (VECC)

19:18 Model investigations of the beam-energy dependence of the transverse momentum and flow correlations

Extraction of the Quark-Gluon Plasma (QGP) transport properties (i.e. specific shear viscosity $\eta/s$) is a prime goal of the heavy-ion programs at the Relativistic Heavy-Ion Collider (RHIC) and the Large Hadron Collider (LHC). Correlators that are sensitive to both initial-state effects and final-state viscous attenuation can give invaluable constraints for temperature ($T$) and chemical potential ($\mu_{B}$) dependence of $\eta/s$. The $\rho(v^{n}_{2},\langle p_{T} \rangle)$ correlator, that gives the strength of the correlation between an event’s mean-transverse momentum $[p_{\mathrm{T}}]$ and its $v_2$ magnitude, shows more sensitivity to the initial state than to final stat effects [1--2]. Correspondingly, the transverse momentum correlator $G_{2}\left(\Delta\eta,\Delta\varphi\right)$ has been shown to be sensitive to $\eta/s$ [3--4]. A comprehensive set of $G_{2}\left(\Delta\eta,\Delta\varphi\right)$ and $\rho(v^{2}_{2},\langle p_{T} \rangle)$ calculations for Au+Au collisions spanning the beam energy range $\sqrt{s_{\rm NN}}$ = 2760--19.6 GeV using the Hydro-hybrid, AMPT and EPOS models, will be presented for several centralities and event shape selections. Our simulated results [1--4] show characteristic beam-energy-dependent and event shape trends that can give significant constraints for the respective influence of initial-state fluctuations, system-size, system-shape, and $\eta/s(\mu_{B},T)$.

[1]~N. Magdy, et al., Phys.Lett.B 821 (2021) 136625
[2]~N. Magdy, et al., arXiv:2111.07406
[3]~N. Magdy, et al., Phys.Rev.C 104 (2021)
[4]~N. Magdy, et al., Eur.Phys.J.C 81 (2021) 8, 779

Speakers: Dr Niseem Abdelrahman (University of Illinois at Chicago), Roy Lacey (Stony Brook University)

19:22 Kaon flow in Au+Au collisions at 1.23AGeV measured with HADES

We present result on an anisotropic transverse flow of kaons ($K^+$, $K^0_S$ and $K^-$) in Au+Au collisions at $\sqrt{s_\mathrm{NN}} = 2.42\,\mathrm{GeV}$ measured with HADES. It was proposed already in mid-nineties that kaon flow around its production threshold might be a good probe for kaon-nucleon potential, and consequently for nuclear equation-of-state [1]. The presented analysis was performed on more than 2 billions events of the 40\% most central collisions which opened the possibility to differential kaon flow analysis even at this low energy regime. The measurements are compared to microscopic transport model predictions, namely UrQMD, SMASH, PHSD, and GiBUU.

[1] G. Q. Li, C. M. Ko, and Bao-An Li: Kaon Flow as a Probe of the Kaon Potential in Nuclear Medium, Phys. Rev. Lett. 74, 235 (1995).

Speakers: Alexandr Prozorov, Dr Lukáš Chlad (Nuclear Physics Institute of the CAS and Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague), Alexandr Prozorov (NPI CAS CZ)

qm22_chlad_kaonflow_poster.pdf

18:30 → 19:30 Poster Session 2 T14_2

18:30 Assessing the ultra-central flow puzzle in the Bayesian era

A longstanding problem in the field is the inability for any simulation model to describe experimental flow data in extremely central collisions --- in particular, models always predict either an elliptic flow that is too large or triangular flow that is too small (or both). We reassess the status of this puzzle in light of recent progress in Bayesian parameter estimation, in which a large model parameter space can be efficiently explored to determine what parameters are necessary for a good fit to experimental results, and how well state-of-the-art models are able to describe data. We explore predictions for flow in ultra-central collisions from multiple recent Bayesian models [1,2] that were tuned to various observables in different collision systems at typical centralities. We find that ultra-central data can now be described with better accuracy than in previous calculations. However, the tension with experimental observation still exists, and gets worse as one goes to more central collisions. Thus, the physics of ultra-central collisions is still not fully understood. We speculate on ways that the puzzle could be solved in the future.

[1] D. Everett et al. [JETSCAPE], Phys. Rev. C 103, no.5, 054904 (2021).
[2] J. S. Moreland, J. E. Bernhard and S. A.Bass, Phys. Rev. C 101, no.2, 024911 (2020).

Speaker: Dr Andre Veiga Giannini

AVGiannini_QM22_ultracentral_poster.pdf

18:34 Beam-energy dependence of the anisotropy scaling functions for identified particle species

Anisotropy scaling functions can provide unique insights into the QCD phase diagram's structure and the transport properties of its respective phases. Scaling functions and scaling coefficients for unidentified and identified particle species spanning the beam energy range $0.007 \le \sqrt s_{NN} \le 5.44$ TeV will be presented and discussed. The scaling functions clarify the respective influence of initial-state eccentricity, expansion dynamics, and final-state viscous attenuation. They also indicate characteristic signatures for the specific viscosity's dependence on the temperature $T$ and the baryon ($\mu_{B}$), strangeness ($\mu_{S}$), and isospin ($\mu_{I}$) chemical potentials. The extracted scaling coefficients provide unique constraints for characterizing both the phase structure of the QCD phase diagram and the dependence of $\eta/s$ on temperature and charged currents. Specific testable predictions (derived from the scaling functions) for future anisotropy measurements in O+O collisions at RHIC (0.20 TeV) and the LHC (7.0 TeV) will also be presented.

Speaker: Roy Alphanso Lacey

18:38 Scaling approach to nuclear structure in high-energy heavy-ion collisions

In high-energy heavy-ion collisions, the energy density profile of the produced quark-gluon plasma and its space-time dynamics are sensitive to the shape and radial profiles of the nuclei, described by the collective nuclear structure parameters including quadrupole deformation $\beta_2$, octupole deformation $\beta_3$, radius $R_0$ and surface diffuseness $a$ [1-3]. Using a transport model simulation as a proxy for hydrodynamics, we find a general scaling relation between these parameters and a large class of experimental observables such as elliptic flow $v_2$, triangular flow $v_3$ and particle multiplicity distribution $p(N_\mathrm{ch})$ In particular, we show that the ratio of these observables between two isobar collision systems depends only on the differences of these parameters. Using this scaling relation, we show how the nuclear structure parameters of $^{96}$Ru and $^{96}$Zr conspire to produce the non-monotonic centrality dependence of ratios of $v_2$, $v_3$ and $p(N_\mathrm{ch})$ between $^{96}$Ru+$^{96}$Ru and $^{96}$Zr+$^{96}$Zr collisions, in agreement with measurements by the STAR Collaboration. We investigate how these scaling relations depend on the transport properties such as $\eta/s$ and found they are insensitive to these final-state effects. Furthermore, we extend this study to include the systems with similar mass number, and rather robust corrections to these scaling relations are found. This scaling approach towards heavy-ion observables demonstrates that isobar collisions is a precision tool to probe the shape and radial structures, including the neutron skin, of the atomic nuclei across energy scales.

[1] arXiv:2111.15559 [nucl-th].
[2] arXiv:2109.01631 [nucl-th].
[3] arXiv:2105.05713 [nucl-th].

Speaker: Chunjian Zhang

QM2022_Scaling_CZhang.pdf

18:42 Probing the hadronic phase of large hadronizing system through the study of the Λ(1520) resonance with ALICE at the LHC

The measurement of hadronic resonance production in heavy-ion collisions at the LHC has led to the observation of a prolonged hadronic phase after hadronisation. Due to their short lifetime, resonances experience the competing effects of regeneration and rescattering of the decay products in the hadronic medium. Studying how the experimentally measured yields are affected by these effects can extend the current understanding of the properties of the hadronic phase and the mechanism that determines the shape of particle transverse momentum spectra.

New preliminary results are presented on the production of the $\Lambda$(1520) resonance measured in Pb-Pb collisions at $\sqrt{s}_{NN}$ = 5.02 TeV with the ALICE detector at the LHC. These results are compared with the set of hadronic resonances with a lifetime span of 1 to 46 fm/$c$ such as $\rho(770)^{0}$, $Κ^{\ast}(892)^{0}$, $\Sigma(1385)^{\pm}$, $\Xi(1530)^{0}$ and $\phi(1020)$ measured by the ALICE experiment. The spectral shapes, mean-$p_{\rm{T}}$ and particle ratios are compared with Fast Reso Blast-Wave model, MUSIC with SMASH afterburner and statistical hadronisation model predictions.

Speaker: Neelima Agrawal (Universita e INFN, Bologna (IT))

2022-04-04-[20220406]QM_Poster_Agrawal_v2_1.pdf

18:46 Left-right splitting of elliptic flow due to directed flow in heavy ion collisions

Recently the splitting of elliptic flow $v_2$ at finite rapidities has
been proposed to be the result of global vorticity in non-central
relativistic heavy ion collisions [1]. Here we confirm the existence
of the $v_2$ splitting. However, we show that this left-right $v_2$
splitting (on opposite sides of the impact parameter axis) is mostly
due to the non-zero directed flow $v_1$ at finite rapidities, with the
splitting given by $v_2(p_x>0)-v_2(p_x<0)\sim 8v_1/3\pi$
[2]. It is thus expected to depend sensitively on the transverse
momentum, rapidity range, particle species, and colliding energy. We
then use a multi-phase transport model, which automatically includes
the vorticity field and flow fluctuations, to demonstrate these features.

We also find that the $v_2$ splitting contains a contribution from a
new type of triangular flow, which at finite rapidities correlates to
the reaction plane. In addition, the $v_2$ splitting measurement
does not necessarily need to measure the 1st-order event plane
$\Psi_1$; it only needs to know whether the 2nd-order event plane angle
$\Psi_2$ or $\pi+\Psi_2$ corresponds to the $p_x>0$ side. So the
left-right $v_2$ splitting contains similar but somewhat different
information compared to the conventional separate $v_1$ and $v_2$
measurements; and it could be easier to do. Therefore, this observable
should benefit the studies of the three-dimensional geometry and
evolution of the dense matter created in heavy ion collisions.

[1] Z. Chen, Z. Wang, C. Greiner, and Z. Xu, arXiv:2108.12735
[hep-ph].
[2] C. Zhang and Z.-W. Lin, 2109.04987 [nucl-th].

Speaker: Prof. Zi-Wei Lin (East Carolina University)

v2splitting-QM2022.pdf

18:50 Bayesian quantification of the Quark-Gluon Plasma from a hybrid model with an IP-Glasma initial state

We present the first comprehensive Bayesian model-to-data comparison of heavy-ion measurements with IP-Glasma initial conditions, which we combine with state-of-the-art hydrodynamics (MUSIC), particlization (iS3D), and transport simulations (SMASH). By using IP-Glasma initial conditions with varied parameters, we produce a result with a consistent and realistic microscopic physics model for the early stages of heavy ion collisions, allowing us to rigorously address the significant uncertainty from initial conditions. We further introduce a systematically-improvable method for exploring the parameter space of the model for the first time in a nuclear physics study, allowing for a more efficient training of the surrogate model emulator. We obtain improved constraints on the temperature dependence of the QGP viscosities by studying simultaneous use of multiparticle correlation observables, which couple initial state geometry and hydrodynamic evolution. Postdictions and predictions are shown using the newly-obtained Bayesian results. This analysis highlights the importance of using realistic pre-equilibrium dynamics and hydrodynamic evolution to accurately quantify the QGP.

Speaker: Matthew Heffernan

Heffernan-QM2022-Poster.pdf

18:54 Investigating strangeness enhancement in jets and medium in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV with ALICE

We probe the origin of strangeness enhancement by separating the strange particles produced in hard processes (jets) from those produced in soft processes (bulk) using the measurement of triggered hadron-$\phi$(1020) and hadron-$\Lambda$ angular correlations. Separating these measurements by event muliplicity in p-Pb collisions allows one to measure the effects of increasing system size on both strange quark production and hadron formation. Previous inclusive strangeness measurements show an increase in the yield ratios of strange over non-strange particles (e.g. an increase in the $\phi/\pi$ and $\Lambda/\pi$ ratios) with increasing system size in Pb-Pb, p-Pb, and pp collisions. In this poster we present current measurements of the $\phi$(1020)/h ratio in jets and medium in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV using the ALICE detector. We also present the first steps towards investigating $\Lambda$ production in jets within the same collision system. These steps include the optimization of the momentum of the triggering hadron and the $\Lambda$ signal extraction via V$^0$ and mixed-event techniques.

Speaker: Ryan Hannigan (University of Texas at Austin (US))

QM2022_Poster_RyanHanniganv8.pdf

18:58 Early-time development of azimuthal anisotropies from small to large Knudsen numbers

We investigate the onset of anisotropic flow in various particle-based transport approaches, ranging from the quasi-collisionless case to the hydrodynamic regime. In the former case, general arguments applied to a phase-space distribution obeying the Boltzmann equation in the limit of few rescatterings lead to a power-law increase of $v_n$ as a function of time. We confirm this behavior in numerical transport calculations with a fixed initial profile, and further study how the exponent of the power law changes when the average number of rescatterings per particle increases, yielding a different result in the hydrodynamic limit. This shows that the early-time development of anisotropic flow is not universal across different theories.

Speaker: Nicolas Borghini

Onset-flow_Poster.pdf

19:02 Triangular Flow of Identified Particles in Fixed Target Au+Au Collisions at STAR

Directed and elliptic flow have been extensively studied in heavy-ion collisions while triangular flow ($v_3$) could be further explored. $v_3$ could prove very useful as a signal for Quark-Gluon Plasma (QGP) formation due to its link to viscosity and the possibility that it is less affected by transport dynamics at very low energies [1]. This poster presents the current progress of an analysis on $v_3$ for $\pi$, $K$, $p$, $d$, and $t$ at the fixed target energies of $\sqrt{s_{NN}}=3.0$ GeV and $7.2$ GeV from phase-II of the Beam Energy Scan at STAR. The results include a correlation between $v_3$ and the first-order event plane and a clear rapidity-odd $v_3$ for $p$. This is the first in a series of collision energies at STAR below and above the QGP phase transition where triangular flow for identified particles will be studied.

[1] J. Auvinen, and H. Petersen. Evolution of elliptic and triangular flow as a function of $\sqrt{s_{NN}}$ in a hybrid model. Phys. Rev. C, 88:064908, 2013.

Speaker: Cameron Racz (University of California, Riverside)

CRacz_Poster_QM2022_slides.pdf

19:06 Directed flow of $\Lambda$ from heavy-ion collisions and hyperon puzzle of neutron stars

The hyperon puzzle is one of the biggest problems in neutron star physics. Using two-body interactions based on hypernuclear data, $\Lambda$ appears in neutron star matter at $(2-4)\rho_0$. This would soften the equation of state and make it difficult to explain the existence of $2 M_\odot$ neutron stars. Therefore, $\Lambda$ should feel a strong repulsive potential in dense nuclear matter. Phenomenologically, it is possible to introduce repulsion at high density by introducing $\Lambda NN$ 3-body repulsion. It is also known that repulsion appears at high density in model calculations based on chiral EFT [1], but there is no experimental data to support this repulsion.

Now, let us focus on the directed flow of $\Lambda$, which is considered to be sensitive to the potential at high densities. It was shown that the proton directed flow in the beam energy of $2\, \mathrm{GeV} < \sqrt{s_{NN}} < 20\, \mathrm{GeV}$ can be explained by the hadron transport model [2]. The repulsive EOS contributes positively to the slope in the early stage (compression stage), while the tilted ellipsoid contributes negatively in the late stage (expansion stage). Sum of these contributions causes the $dv_1/dy$ sign change at $\sqrt{s_{NN}}\simeq 10\, \mathrm{GeV}$ [3]. This mechanism predicts that the $\Lambda$ directed flow slope becomes negative at lower beam energies since $\Lambda$ does not exist before the collision, but the data [4] show the balance energy of $\Lambda$ is similar to that of proton. Then the positive contribution needs to be larger and the repulsion should be stronger for $\Lambda$.

In this work, we study the directed flow of $\Lambda$ by using the transport model (JAM2-RQMDv) [2] and estimate the potential of $\Lambda$ at high densities. We use the Fermi momentum expansion of the potential given in [5], and constrain the slope ($L_\Lambda$) and the curvature ($K_\Lambda$) parameters of the $\Lambda$ potential.

[1] D. Gerstung, N. Kaiser, W. Weise, Eur. Phys. J. A 56 (2020), 175.
[2] Y. Nara, A. Ohnishi, arXiv:2109.07594 [nucl-th].
[3] L. Adamczyk et al. [STAR], Phys. Rev. Lett. 112 (2014), 162301.
[4] P. Shanmuganathan et al. [STAR], Nucl. Phys. A 956 (2016), 260.
[5] I. Tews, J. M. Lattimer, A. Ohnishi, E. E. Kolomeitsev, Astrophys. J. 848 (2017), 105.

Speaker: Akira Ohnishi

full version

QM2022-AO-poster-short.pdf

19:10 Study of resonances' properties with respect to jet leading particle in Pb--Pb collisions at $\sqrt{s_\mathrm{NN}}$ = 5.02 TeV in ALICE experiment

Hadronic resonances can act as useful probes to examine the hadronic phase in ultra-relativistic heavy-ion collisions. On the other hand, there could also be perspectives and unexplored methods for studying the partonic phase via resonances. Properties, such as the masses and widths, of resonances produced or decaying during the partonic phase could be modified.

In order to reach resonances from the partonic phase, resonances' properties as a function of emission direction with respect to high transverse momentum particles (~ jet leading particle) should be investigated.

In this contribution, the study of the mass and width of the resonances $K^{*}(892)^{0}$ and $\phi(1020)$ in lead-lead collisions at $\sqrt{s_\mathrm{NN}}$= 5.02 TeV with respect to the leading jet particle will be presented and the influence of the background (thermal resonances) will be shown.

Speaker: Zuzana Jakubčinová (Pavol Jozef Safarik University (SK))

Poster_JakubcinovaQM22_final.pdf

19:14 The spatially constrained QCD colour re-connection for heavy-ion collisions in Pythia8/Angantyr model

We have extended the so-called QCD colour re-connection model with spatial constraints on the allowed re-connection between the colour strings in the Pythia8/Angantyr model. The Angantyr model uses the Pythia8 event generator machinery with sophisticated stacking of pp-like collisions to simulate heavy-ion events, without any assumption of a thermalized medium of QGP. So far, all sub-collisions are colour reconnected and hadronized independently in the heavy-ion collisions in the Angantyr model. In this work, we introduce a parameter that constrains the allowed colour re-connection between two colour strings based on the transverse spatial separation between the strings. This new parameter now allows us to combine all sub-collisions in a heavy-ion collision event at the parton level in Angantyr and perform re-connections between partons from different sub-collisions. We use the so-called QCD colour re-connection model of Pythia8, because its feature of junction formation enhances the baryon production with increasing multiplicity in collision events. We constrain the re-tuning of our model parameters to the pp collision level, and only parameters introduced in the Angantyr model are re-tuned at the pA collision level. We will show the effects of the spatial constraint in the colour re-connection model on the final state charged multiplicity, and production of identified hadron (and their ratios) in pp and pA collisions.

Speaker: Harsh Shah (Lund University)

QM22-Angantyr-HS.pdf

19:18 Hydrodynamics with Baryon, Strangeness, and Electric Charge conservation

Heavy-ion collisions has 3 relevant conserved charges: baryon number (B), strangeness (S), and electric charge (Q). We have developed a new 2+1 relativistic viscous hydrodynamic code using Smoothed Particle Hydrodynamics that conserves BSQ, coupled to a 4D Lattice Quantum Chromodynamics equation of state. ICCING initial conditions that account for gluon splittings into quark anti-quark pairs provide BSQ initial charge densities relevant for the LHC and top RHIC energies. We explore new experimental observables with a specific focus on strangeness.

Speakers: Dekrayat Almaalol (University of Illinois Urbana-Champaign), Jacquelyn Noronha-Hostler (University of Illinois Urbana Champaign)

QM22_BSQ.pdf

20:00 → 21:00 Wine and cheese

21:00 → 22:30 CONCERT: SPECIAL EVENT

Thursday, 7 April

09:00 → 10:40 Parallel Session T02: Chirality, vorticity and spin polarization: III

Convener: Jurgen Schukraft (University of Copenhagen (DK))

09:00 Measurements of charge-dependent correlations with CMS

Charge-dependent azimuthal anisotropy Fourier coefficients are measured with two- and three-particle correlations in pPb and PbPb collisions. The difference between positively and negatively charged particles for the second-order two-particle $(v_2\{2\})$ and three-particle $(v_2\{3\})$ coefficients for both pPb and PbPb, and third order two-particle coefficient $(v_3\{2\})$ for PbPb, are presented. The observed results are challenging the hypothesis that attributes charge-dependent azimuthal correlations in heavy ion collisions to the chiral magnetic effect. In addition, the two-particle electric charge balance function is used as a probe to study the charge creation mechanism in high energy heavy ion collisions, for the first time in CMS. The balance function is constructed using like and unlike charged-particle pairs. The width of the balance function, both in relative pseudo-rapidity and relative-azimuthal angle, increases from more central collisions to peripheral ones. Narrowing and widening of these widths indicate late and early hadronization, respectively.

Speaker: Subash Chandra Behera (Indian Institute of Technology Madras (IN))

QM2022_CMW.pdf

09:20 Kinetic theory for massive spin-1 particles

We derive a semi-classical kinetic theory for massive spin-1 particles from the Wigner-function formalism.

Starting from an interacting Proca Lagrangian, we obtain equations of motion for the Wigner function of massive charged vector bosons in classical electromagnetic fields. Performing a power-expansion up to first order in the Planck constant $\hbar$, we then derive generalized Boltzmann equations and mass-shell contraints, in which quantum effects are pertubatively included. In particular, we obtain an equation of motion for the tensor polarization. If the latter is neglected, we recover known results for the kinetic equations of scalar distribution and vector polarization of spin-1/2 particles.

As a next step, we study the collision kernel emerging from a general interaction. Analogous to spin-1/2 particles, the collision term contains local and nonlocal contributions, allowing for the exchange of spin and orbital angular momentum, providing a mechanism for spin polarization from vorticity.

Our framework can be used describe polarization phenomena of spin-1 particles, e.g. $\rho$ mesons, in heavy-ion collisions.

Speaker: David Wagner (Goethe University Frankfurt)

QM_Kinetic_theory_spin_1.pdf

09:40 Collectivity in intermediate-scale QGP and extended hydrodynamic regime

The quark-gluon plasma (QGP) is a fluid at a long wavelength and becomes a collection of weakly-coupled partons at an asymptotically short wavelength. However, its properties at the "mesoscopic" length scale, which is too short for a fluid description and too long for a perturbative treatment, remain elusive. In this work, we consider the response of QCD-like plasma to energy/momentum disturbance as a function of the gradient. For both N=4 super-Yang Mills theory in strong coupling limit and kinetic theory under relaxation time approximation, we find that hydrodynamic modes continue dominating medium's response even in the region where Knudsen number is large. However, in this extended hydrodynamic regime, both the first-order and second-order hydrodynamics fail to characterize medium's behavior. Inspired by the recent development in extended hydrodynamics, such as Hydro+ [1], we construct a simple yet not trivial extension of the Muller-Israel-Stewart theory, namely MIS, and show this novel framework can quantitatively describe hydrodynamic modes in both hydrodynamic and extended hydrodynamic regimes with a suitable choice of model parameters for representative microscopic theories with and without quasi-particle descriptions [2]. As an illustration, we apply MIS to study how a Bjorken-expanding QGP responds to a moving energetic parton [3].

Refs.

[1] M. Stephanov and Yi Yin , "Hydro+: hydrodynamics with parametric slowing down and fluctuations near the critical point", Phys. Rev. D 98 (2018) 036006. 

[2] Weiyao Ke and Yi Yin, in preparation. 

[3] Weiyao Ke and Yi Yin, "Beyond the wake: non-hydrodynamic response of an expanding Quark-gluon plasma", PoS HardProbes2020 (2021) 187

Speaker: Dr Yi Yin (Institute of modern physics, Chinese Academy of Sciencessti)

QM_MIS_v2_inpdf.pdf

10:00 Measurements of hyperon polarization in heavy-ion collisions at \sqrt{sNN} = 3 - 200 GeV with the STAR detector

In heavy-ion collisions, the observation of the global hyperon polarization, $\overline{P}_\mathrm{H}$, ranging from $\sqrt{s_\mathrm{NN}}=7.7$~GeV to 5.02~TeV has revealed the existence of large vorticities perpendicular to the reaction plane due to system's orbital angular momentum. We present recent results on $\overline{P}_\mathrm{H}$, and differential measurements thereof, extended to the low energies of 3 and 7.2~GeV~[1]. A notable advantage of the STAR acceptance at low $\sqrt{s_\mathrm{NN}}$ is the ability to measure the dependence of $\overline{P}_\mathrm{H}$ on $y$ across the full range of hyperon production in $y$ which can test the predictions of numerous model calculations. Further studies of differential measurements of $\overline{P}_\mathrm{H}$ are presented as well using Au+Au collisions at $\sqrt{s_\mathrm{NN}}=19.6$ and $27$~GeV which allow for comparisons to the low-$\sqrt{s_\mathrm{NN}}$ measurements presented here and to the high-energy measurements studied in Ref.~[2]. Studies of the vortical flow structure's dependence on system size are also possible using Ru+Ru and Zr+Zr collisions at $\sqrt{s_\mathrm{NN}}=200$~GeV which are presented here as well. Furthermore, while $\overline{P}_\mathrm{H}$ reveals information about the vorticity driven by angular momentum, a recent study~[3] measuring local polarization along the beam direction, $\overline{P}_\mathrm{Z}$, revealed vorticity in the QGP arising from collective flow. The measurement stands in disagreement with a number of model calculations and, to shed light on the matter, measurements of $\overline{P}_\mathrm{Z}$ can be conducted in smaller systems than Au+Au or relative to higher-order event-plane angles. These measurements of $\overline{P}_\mathrm{Z}$ in Ru+Ru and Zr+Zr at $\sqrt{s_\mathrm{NN}}=200$~GeV presented here will provide valuable insight into the mechanisms of flow-driven vorticity.

[1]~M. S. Abdallah et al. Global $\Lambda$-hyperon polarization in Au+Au collisions at $\sqrt {s_{\rm NN}}$=3~GeV. {\it Phys. Rev. C}, 104(6):L061901, 2021.

[2]~J. Adam et al. Global polarization of $\Lambda$ hyperons in Au+Au collisions at $\sqrt{s_{_{NN}}}$ = 200 GeV. {\it Phys. Rev. C}, 98:014910, 2018.

[3]~J. Adam et al. Polarization of $\Lambda$ ($\bar{\Lambda}$) hyperons along the beam direction in Au+Au collisions at $\sqrt{s_{_{NN}}}$ = 200 GeV. {\it Phys. Rev. Lett.}, 123(13):132301,2019.

Speaker: Joseph Adams (Ohio State University)

Adams_Polarization_QuarkMatter22_v12.pdf

10:20 Search for the chiral effect using isobar collisions and BES-II data from STAR

Quantum Chromodynamics allows for the formation of parity-odd domains inside the medium produced in heavy-ion collisions associated with a net chirality of the quarks. As a consequence, the Chiral Magnetic Effect (CME) and Chiral Vortical Effect (CVE) are phenomena predicted to occur and cause electric-charge and baryonic-charge separation along the direction of the magnetic field and vorticity created in heavy-ion collisions, respectively. Recently, the STAR experiment has performed a precision measurement of the possible difference in charge separation along the magnetic field direction between isobar systems $^{96}_{44}{\rm Ru}+^{96}_{44}{\rm Ru}$ and $^{96}_{40}{\rm Zr}+^{96}_{40}{\rm Zr}$ at $\sqrt{s_{\rm NN}}=200$ GeV. In this talk, we will present the findings from the isobar blind analysis. While the isobar blind analyses were dedicated towards CME searches at the top RHIC energy, the RHIC BES-II program provides a unique opportunity and advantages at lower energies, where the magnetic field lifetime may be longer than those at the higher energy collisions. We will also present the latest results on the search for CME and CVE at 27 GeV Au+Au collisions with the unique capabilities of the STAR Event Plane Detector.

Speaker: YU HU

QM22_Apr07_YuHu_ChiralEffect.pdf

09:00 → 10:40 Parallel Session T07: Correlations and fluctuations: II

Convener: Jiangyong Jia (Stony Brook University (US))

09:00 Measurements of collectivity in the forward region at LHCb

Particle flow measurements, which provide evidence of the QGP medium, are a powerful tool to study the QGP evolution in heavy-ion collisions. Using the two-particle correlation technique, LHCb has observed the ridge structure due to particle flow, in the forward pseudorapidity range $2<\eta<5$ alongside the leading jet peak in long-range correlations ($|\eta|>2$). This talk will detail the analysis of the ridge structure in $p$Pb/Pb$p$ collisions at 5~TeV and the results, which show that the ridge structure is more pronounced in the low transverse momentum region and the high multiplicity events where the collective flow property of QGP may be significant. This presentation will also include the details of new LHCb analyses to extract the flow harmonics in the forward region.

Speaker: Cheuk Ping Wong (Los Alamos National Laboratory (US))

QM2022_LHCb_flow_ver4.pdf

09:20 Longitudinal Decorrelation Measurements from $pp$ to A+A with the ATLAS detector

This talk presents a new measurement of longitudinal decorrelation in $pp$ collisions with ATLAS. It is expected that the deposited energy in the transverse ($x,y$) plane varies, depending on the longitudinal ($z$) slice examined, which is correlated with the rapidity of the produced particles. Thus, particles from different rapidity slices will have flow vectors that differ in magnitude and orientation due to the longitudinal variation, longitudinal decorrelation, which grows with increasing particle rapidity separation. For flow harmonic $n$, such longitudinal decorrelations have been characterized, for large systems, in terms of $r_{n}$, the ratio of large-rapidity-gap to small-rapidity-gap correlations. This analysis performs the first measurements of $r_n$ in $pp$ collisions at 5~TeV and 13~TeV. The analysis is carried out via a two-particle correlation method, utilizing charged tracks of varying $\eta$ within $|\eta| < 2.5$ and topo-clusters of $4.0<|\eta_\text{ref}|<4.9$. Because non-flow effects are more significant in $pp$ collisions, non-flow template subtraction procedures are applied. Final results are quoted for $r_{2}$ and its slope $F_{2}$, over a range of multiplicities. Similar non-flow subtraction techniques are applied to the full multiplicity range of Xe+Xe collision data and the results are compared to the two $pp$ energies at appropriate multiplicities. This gives some of the first detailed information on the correlation between longitudinal and transverse energy deposition in $pp$ collisions.

Speaker: Blair Daniel Seidlitz (University of Colorado Boulder (US))

BSeidlitz_Decor_QM22_Final.pdf

09:40 Probing flow fluctuations through factorization breaking in heavy-ion collision

The collective flow of particles, generated in the expansion of the dense matter that is created in heavy-ion collisions, fluctuates from event to event. In particular, the flow vectors at two different transverse momenta fluctuate with respect to each other. One way to probe this flow fluctuation is to study the decorrelation between the flow at two different momentum bins. However, the flow vector decorrelation
can occur as a combined effect of flow magnitude fluctuation and flow angle (flow direction) fluctuation. Thus, these flow fluctuations can be mapped using the flow factorization breaking coefficient. Moreover, the factorization breaking coefficient for second moments of flow vectors can be constructed. This additional observables allow to measure separately the flow magnitude and the flow angle decorrelation. Following the preliminary data from ALICE, we study the correlation between the harmonic flow squared, where one of the flow is fixed at a transverse momenta and the other is averaged over the momentum range (global flow). As a result of the factorization, the independent measurement of the flow vector correlation and flow magnitude correlation can lead to the possible extraction of flow angle correlation. Our model results are compared to the data. We also study the momentum dependent correlation between mixed flow harmonics and present possible predictions, which
could be used to gain additional information on the fluctuating initial state and the dynamics in heavy-ion collisions. (P. Bozek , R. Samanta, arXiv:2109.07781)

Speaker: Rupam Samanta (AGH University of Science and Technology)

QM2022_Rupam.pdf

10:00 Charmed hadron interactions and correlation functions

Charmed hadron interactions are very important in current exotic hadron physics. For example, charmed pentaquark state ($P_c$) appears around the $\Sigma_c \bar{D}^{(*)}$ thresholds, and then $P_c$'s are suggested to be hadron molecules caused by the attraction between $\Sigma_c$ and $\bar{D}^{(*)}$. While it is difficult to perform charmed hadron scattering, recent femtoscopic studies allows us to get information on charmed hadron interactions. Since the correlation function $C(q)$ is given as the convolution of the source function and the wave function squared, $C(q)$ tells us how much the wave function is enhanced or suppressed from the free case provided that the source function is known.

In this presentation, we discuss the charmed hadron interactions and correlation functions [1]. Specifically, we consider $pD^{\pm}$, $DD^{*}$ and $D\bar{D}^{*}$ pairs, which are related to the (singly) charmed pentaquark state, $T_{cc}$, and $X(3872)$, respectively. As the first step, we use one-range Gaussian potentials whose strength are determined to reproduce the scattering lengths in theoretical models ($DN$ and $\bar{D}N$) or the binding energies ($DD^*$ and $D\bar{D}^*$). The calculated correlation functions show significant dependence on the interactions and the source size. Thus measurement of these correlation functions will judge theoretical models and the molecule picture of exotic hadrons.

[1] Y. Kamiya, T. Hyodo, and A. Ohnishi, in preparation.

Speaker: Akira Ohnishi

QM2022-AO.pdf

10:20 Higher-Order Cumulants of Net-Proton Multiplicity Distributions in Zr+Zr and Ru+Ru Collisions at $\sqrt{s_{_{\mathrm{NN}}}}$ = 200 GeV by the STAR Experiment

The Relativistic Heavy Ion Collider (RHIC) at Brookhaven is a facility to create and study the strongly interacting Quark-Gluon Plasma (sQGP). Higher-order cumulants of the conserved quantities and their ratios are powerful tools to study the properties of sQGP and explore the QCD phase structure, such as critical point and/or the first-order phase transition boundary. It has been reported by the STAR Collaboration that the fourth-order cumulant of the net-proton multiplicity distribution shows a non-monotonic energy dependence ($\sqrt{s_{_{\mathrm{NN}}}}$ = 7.7 - 62.4 GeV). In addition, the comparison between the sixth-order net-proton cumulant results and Lattice QCD calculations suggests a smooth crossover transition in central Au+Au collisions at $\sqrt{s_{_{\mathrm{NN}}}}$ = 200 GeV.

In this talk, we will present the net-proton cumulants and their ratios up to sixth-order as a function of multiplicity using high statistics data of Zr+Zr and Ru+Ru collisions at $\sqrt{s_{_{\mathrm{NN}}}}$ = 200 GeV. The STAR experiment collected two billion events for each colliding system. We will compare the multiplicity dependence to the published net-proton cumulants in Au+Au collisions at $\sqrt{s_{_{\mathrm{NN}}}}$ = 200 GeV. In addition, we will compare the results to Lattice QCD, the Hadron Resonance Gas model, and hadronic transport model calculations. The physics implications will be discussed.

Speaker: Ho San Ko

HoSanKO.pdf

09:00 → 10:40 Parallel Session T09: Ultra-peripheral collisions: I

Convener: Dariusz Miskowiec (GSI Darmstadt)

09:00 Measurements of light-by-light scattering and lepton pair photoproduction in PbPb collisions with the CMS experiment

Ultraperipheral lead-lead collisions at $\sqrt{s_{_{\mathrm{NN}}}} =$ 5.02 TeV produce very large photon fluxes that provide the conditions to study photon-photon fusion processes in phase space regions inaccessible with proton-proton data. Measurements of light-by-light (LbyL) scattering and lepton pair photoproduction in ultraperipheral PbPb collisions will be presented with data collected by the CMS detector during the LHC Run 2. These processes open up a unique window through which to search for physics beyond the standard model, e.g., the LbL study allows for competitive searches for axion-like particles (ALPs) in the 5--100 GeV ALP mass range. The lepton pair photoproduction provides the first data-driven demonstration that the average transverse momentum of photons emitted from relativistic heavy ions has an impact parameter dependence, the latter determined based on the number of neutrons detected in the very forward pseudorapidity. All results are compared with quantum electrodynamics calculations and provide crucial new tests and constraints on models of photon-induced interactions in ultraperipheral collisions.

Speaker: Arash Jofrehei (University of Zurich (CH))

QM_Arash_Jofrehei.pdf

09:20 J/$\psi$ photoproduction and the production of dileptons via photon-photon interactions in hadronic Pb–Pb collisions measured with ALICE

Photon-photon and photonuclear reactions are induced by the strong electromagnetic field generated by ultrarelativistic heavy-ion collisions. These processes have been extensively studied in ultra-peripheral collisions with impact parameters larger than twice the nuclear radius. Since a few years, both the photoproduction of the J/$\psi$ vector meson and the production of dileptons via photon-photon interactions have been observed in A–A collisions with nuclear overlap. Photoproduced quarkonia can probe the nuclear gluon distributions at low Bjorken-x, while the continuum dilepton production could be used to further map the electromagnetic fields produced in heavy-ion collisions and to study possible induced or final state effects in overlapping hadronic interactions.
Both measurements are complementary to constrain the theory behind photon induced reactions in A–A collisions with nuclear overlap and the potential interaction of the measured probes with the formed and fast-expanding QGP medium. In this presentation, measurements of coherent J/$\psi$ photoproduction cross sections in Pb-Pb collisions in the 40%-90% centrality range, measured at midrapidity in the dielectron channel with ALICE will be presented for the first time using the full Run 2 data. Thanks to the excellent tracking resolution of the TPC, the transverse momentum distribution of coherently photoproduced J/ψ can be accurately measured. Final results on coherent J/ψ photoproduction cross-sections at forward rapidity in the dimuon decay channel in the 30-90% centrality range will also be shown. Finally, the measurement of an excess in the midrapidity dielectron yield at low mass and $p_{\rm T}$, in the centrality interval 50-90% will be shown. Results will be compared with available models.

Speaker: Alexandra Neagu (University of Oslo (NO))

QM_aneagu_final.pdf

09:40 Quarkonia Production in Ultraperipheral PbPb collisions at LHCb

Measurements of quarkonia production in peripheral and ultra-peripheral heavy-ion collisions are sensitive to photon-photon and photon-nucleus interactions, the partonic structure of nuclei, and the mechanisms of vector-meson production. LHCb has studied both coherent and incoherent production of $J/\psi$ mesons in peripheral and ultra-peripheral collisions using PbPb data at forward rapidity with the highest precision currently accessible. Here we will present these measurements, along with comparisons with the latest theoretical models and with results from other experiments. Future UPC measurements with the upgraded LHCb detector in Run 3 will also be discussed.

Speaker: Samuel Belin (Universidade de Santiago de Compostela (ES))

quark_matter_2022_belin_final.pdf

10:00 Measurements of photon-photon fusion processes in ultra-peripheral Pb+Pb collisions with ATLAS

Relativistic heavy-ion beams are accompanied by a large flux of equivalent photons, giving rise to a set of photon-induced processes. These can lead to photon-photon interactions in ultraperipheral collisions. This talk presents a series of measurements of such processes performed by the ATLAS Collaboration. New measurements of exclusive dilepton production (electron, muon, or tau pairs) are presented. This process provides detailed constraints on the nuclear photon flux and its dependence on the impact parameter and photon energy. In particular, the study of the cross-sections in the presence of forward neutron production, provides an additional experimental handle on the impact parameter range sampled in the observed events. The final ATLAS measurements of light-by-light scattering are also presented. These measurements are performed using the full Run-2 dataset which results in substantially reduced uncertainties compared to the previous measurements. They provide a precise and unique opportunity to investigate extensions of the Standard Model, such as presence of axion-like particles.

Speaker: Peter Alan Steinberg (Brookhaven National Laboratory (US))

Steinberg_QM2022b_v4.pdf

10:20 Collision species and beam energy dependences of photon-induced lepton pair production at STAR

Ultra-strong electromagnetic field can generate a large flux of quasi-real photons arising from the Lorentz-contraction and the large electric charge (Z) of heavy nuclei colliding at ultra-relativistic speeds. These ultra-strong fields can be studied through dileptons ($e^{+}e^{-}$ and $\mu^{+}\mu^{-}$) and vector mesons ($J/\psi$) produced via photon-photon and photonuclear processes, respectively, in which the photon flux is proportional to $Z^{2}$. In particular, the photo-produced dileptons carry information about the strength and spatial distribution of the colliding fields. Therefore, they provide a novel tool to test the spatial and polarization dependent effects predicted by QED for vacuum birefringence and the Breit-Wheeler process.

In this talk, we present the first investigation of impact parameter and collision species dependences of dilepton and $J/\psi$ photo-production in isobaric collisions ($^{96}_{44}Ru$ + $^{96}_{44}Ru$, $^{96}_{40}Zr$ + $^{96}_{40}Zr$) at $\sqrt{s_\mathrm{NN}} =$ 200 GeV. The collision energy dependence of these photo-production processes is further studied in peripheral Au+Au collisions with measurements at $\sqrt{s_\mathrm{NN}} =$ 54.4 GeV and 200 GeV. We discuss the physics implications of these results and compare them to models.

Speaker: Xiaofeng Wang (Shandong University)

QM2022_XiaofengWang.pdf

09:00 → 10:40 Parallel Session T11: Heavy flavors, quarkonia, and strangeness production: II

Convener: Joerg Aichelin (Subatech/CNRS)

09:00 Charm production: constraint to transport models and charm diffusion coefficient with ALICE

In this contribution the nuclear modification factor ($R_\mathrm{AA}$) of prompt charm hadrons and heavy-flavour hadrons decaying to leptons measured in Pb-Pb collisions at $\sqrt{s_\mathrm{NN}}=5.02$ TeV by the ALICE Collaboration are presented. The measurement of heavy-flavour leptons in Xe-Xe collisions is also discussed. Heavy quarks are a very suitable probe to investigate the quark-gluon plasma (QGP) produced in heavy-ion collisions, since they are mainly produced in hard-scattering processes and hence in shorter timescales compared to the QGP. Measurements of charm-hadron production in nucleus-nucleus collisions are therefore useful to study the properties of the in-medium charm-quark energy loss via the comparison with theoretical models. Moreover, the comparison of different colliding systems provides insights in the dependency on the collision geometry.
Models describing the heavy-flavour transport and energy loss in an hydrodynamically expanding QGP require also a precise modelling of the in-medium hadronisation of heavy quarks, which is investigated via the measurement of prompt $\mathrm{D_s^+}$ mesons and $\Lambda_\mathrm{c}^{+}$ baryons.
In addition, the measurement of the azimuthal anisotropy of strange and non-strange D mesons is discussed. The second harmonic coefficient provides information about the degree of thermalisation of charm quarks in the medium, while the third one relates to its sensitivity to event-by-event fluctuations in the initial stage of the collision.
A thorough systematic comparison of experimental measurements with phenomenological model calculations will be performed in order to disentangle different model contributions and provide important constraints to the charm-quark diffusion coefficient $D_s$ in the QGP.

Speaker: Lucas Anne Vermunt (Utrecht University (NL))

QM22_LVermunt.pdf

09:20 Measurements of heavy-flavor quark probes of the QGP with the ATLAS detector

Open heavy-flavor hadron production, azimuthal anisotropy and correlations in heavy-ion collisions serve as powerful tools to study quark-gluon plasma (QGP) properties, heavy-flavor energy loss due to interaction with QGP, and heavy-flavor hadronization.
This talk presents recent ATLAS results on the azimuthal anisotropy ($v_2$ and $v_3$) and nuclear modification factor ($R_\mathrm{AA}$), separately for muons from charm and bottom hadrons, as well as di-muon azimuthal correlations and yields in Pb+Pb and $pp$ collisions.
Muons from both charm and bottom hadrons are found to have significant non-zero, second- and third-order azimuthal anisotropies in Pb+Pb collisions, with larger anisotropies for muons from charm hadrons than for muons from bottom hadrons. We highlight that a precise measurement of $v_3$ for bottom is presented.
Muons from both sources are also observed to be strongly suppressed with respect to the $pp$ baseline, in a way that depends on the mass of the parent hadron at low to moderate muon $p_\mathrm{T}$.
These studies can help to determine whether collisional or radiative processes dominate the energy loss of HF quarks as they traverse the QGP produced in heavy-ion collisions. In particular, the simultaneous measurement of multiple observables for both charm
and bottom with the same detector and technique is crucial in providing constraints to state-of-the-art theoretical predictions.
Finally, azimuthal correlations and yields of heavy-flavor muon pairs in Pb+Pb collisions are compared to the $pp$ reference and are quantified by the nuclear-modification factor $R_{\mathrm{AA}}$,
The modifications of the widths of these correlations are also measured.

Speaker: Qipeng Hu (Lawrence Livermore Nat. Laboratory (US))

QM2022_ATLASHF_QHu_final.pdf

09:40 Detailed study of Upsilon suppression with the measurement of the $\Upsilon$(3S) meson in PbPb collisions at 5.02 TeV in CMS

Because of the different binding energies, bottomonium mesons are particularly useful probes to understand the thermal properties of quark-gluon plasma. Previously, CMS observed the sequential suppression of $\Upsilon$(1S), $\Upsilon$(2S), and $\Upsilon$(3S) in heavy ion (AA) collisions, which was widely accepted as evidence for the QGP formation. However, the $\Upsilon$(3S) yield was excessively low, thus allowing us to report only statistical upper limits. In this talk, we present a detailed study of the measurement of excited bottomonium states with improved analysis technique and high-statistics data that enables us to observe the $\Upsilon$(3S) meson in AA for the first time. The results are discussed together with the previous measurements in pPb collisions, which finally provides a full scan of all $\Upsilon$(nS) states over the whole phase space.

Speaker: Soohwan Lee (Korea University (KR))

QM2022_upsilon_soohwanlee_final.pdf

10:00 Production of exotic hadrons in high multiplicity $pp$ and $p$Pb collisions at LHCb

The recently discovered abundance of hadrons with more than three valence quarks remains poorly understood. Measurements of these exotic hadrons and their interactions with the QCD medium provides a new avenue to investigate their properties. Additionally, the production of hadrons with more than three quarks presents new testing grounds for models of particle transport and recombination in hadron collisions. This talk will explore data on the exotic $X$(3872) and $T_{cc}^{+}$ hadrons, similarities in their properties, and differences in their production as a function of charged particle multiplicity in $pp$ collisions. We will also present the first measurement of the nuclear modification factor $R_{pA}$ for a four-quark state, the $X$(3872), in $p$Pb collisions. The outlook for future measurements in heavy ion collisions and with the LHCb fixed-target system SMOG II will be discussed.

Speaker: Eliane Epple (Los Alamos National Laboratory (US))

QM22_Epple_V3.pdf

10:20 Studies of heavy quark dynamics using $B^+$, $B^0_s$ and $B_{c}$ mesons with the CMS detector

Heavy quarks are one of the most important probes to study the properties of quark-gluon plasma (QGP). Hadronization of beauty quarks is not as well understood as in the charm sector. Illuminating the hadronization mechanism is crucial for extracting the transport properties of the QGP. We present new results on nuclear modification factors of $B^0_s$ and $B^+$ mesons and their yield ratios in pp and PbPb collisions at 5.02 TeV, using data recorded with the CMS detector in 2017 and 2018. The reported B-meson nuclear modification factors over an extended transverse momentum range will provide important information about the diffusion of beauty quarks and the flavor dependence of in-medium energy loss. The $B^0_s/ B^+$ yield ratio in pp and PbPb can shed new light on beauty hadronization mechanisms from small to large systems and on the relevance of parton recombination in the medium. We also report the first observation of the $B_{c}$ meson in nucleus-nucleus collisions, through partial reconstruction of the semi-leptonic decay $B_{c^{+}}$ $\rightarrow$ (J/$\psi$ $\rightarrow$ $\mu^{+}\mu^{-}$) $\mu^{+}$ $\nu_{\mu}$. Given the low production cross-section in proton-proton collisions, its production could be dramatically enhanced by the combination of beauty quarks with the charm quarks present in the plasma, providing additional insights into the recombination mechanism. The $B_{c}$ nuclear modification factors are compared with similar (CMS) measurements for other heavy-flavor mesons and quarkonia.

Speaker: Tzu-An Sheng (Massachusetts Inst. of Technology (US))

qm2022_ta.pdf

10:40 → 11:10 Coffee break

11:10 → 13:10 Parallel Session T07: Correlations and fluctuations: III

Convener: Adam Trzupek (Institute of Nuclear Physics Polish Academy of Sciences (PL))

11:10 Kinetics of the chiral phase transition in a quark-meson $\sigma$ model

A challenging goal in relativistic heavy-ion physics is the
investigation of the phase diagram of strongly interacting matter and
the determination of its phase structure, governed by the approximate
chiral symmetry of the light-quark sector of QCD. In this study [1] we
investigate a linear quark-meson $\sigma$ model in and out of
equilibrium employing Schwinger-Keldysh real-time techniques to derive a
set of coupled Boltzmann-Uehling-Uhlenbeck (BUU) equations for the
$\sigma$-mean field (the order parameter of the phase transition) and
the quark- and meson phase-space distribution function from a
$\Phi$-derivable approximation, which is then numerically solved using
an accurate quadrature algorithm to evaluate the collision terms. This
numerical scheme is used to evaluate the grand-canonical baryon-number
fluctuations for an expanding fireball. Even when starting with a purely
Gaussian initial distribution the evolution results in a temporary
buildup of higher-order fluctuations of the net-baryon number like the
curtosis at low momenta when the system is evolving close to the
critical point or the first-order phase-transition line. This is mainly
caused by the slowly evolving $\sigma$-mean field, i.e., the order
parameter of the phase transition. This is partially counterballanced by
the further dissipative evolution due to collisions of the quarks,
mesons, and the mean field, leading to a considerable weakening of the
final fluctuations, depending on the expansion rate of the fireball.

[1] Annals of Physics 431, 168555 (2021)

Speakers: Prof. Carsten Greiner (Institut für Theoretische Physik, Goethe-Universität Frankfurt), Hendrik van Hees

Hees_qm22.pdf

11:30 Extracting effective viscosities from heavy ion collisions

In this presentation, I'll introduce the effective viscosity that can be computed from the viscous damping of anisotropic flow in heavy-ion collisions for arbitrary temperature-dependent shear and bulk viscosities, running ideal and viscous hydrodynamic simulations. I'll show that the damping is solely determined by effective shear and bulk viscosities, which are weighted averages over the temperature. We determine the relevant weights for LHC and RHIC and present their dependence, where the effective bulk viscosity is driven in the earlier stages of the collision, and the effective shear viscosity coming from the lowest temperatures, just above freeze-out. I'll also show recent developments on the effective viscosities, where we can use the "data-driven" (Bayesian analysis) and Lattice computations to the temperature dependence on viscosities and extract the effective viscosities to heavy-ion collisions. Then we can compare the different parametrizations for viscosities.

Speaker: Dr Fernando Gardim (Federal University of Alfenas)

QM22-Gardim.pdf

11:50 Flow and transverse momentum correlation in Pb+Pb and Xe+Xe collisions with ATLAS: assessing the initial condition of the QGP

One important challenge in our field is to understand the initial condition of the QGP and constrain it using sensitive experimental observables. Recent studies show that the Pearson Correlation Coefficient (PCC) between $v_n$ and event-wise mean transverse momentum $[p_\mathrm{T}]$, $\rho_n(v_n, [p_\mathrm{T}])$, and its centrality dependence can probe several ingredients of the initial state, such as number and size of sources, nuclear deformation, volume fluctuation, and initial momentum anisotropy. In particular, a recent calculation shows that the $^{129}$Xe nucleus is triaxially deformed, which is expected to enhance $\rho_2$ in $^{129}$Xe+$^{129}$Xe relative to $^{208}$Pb+$^{208}$Pb collisions.

This talk presents new, comprehensive and precision measurements of $v_n-[p_\mathrm{T}]$ correlation in $^{129}$Xe+$^{129}$Xe and $^{208}$Pb+$^{208}$Pb collisions for harmonics $n = 2$, 3, and 4. The results are obtained via the standard and subevents cumulant methods to assess the role of non-flow and flow decorrelations in these observables, and they are found to be small in the mid-central and central collisions in these systems. All PCC coefficients, $\rho_2$, $\rho_3$ and $\rho_4$ show rich and non-monotonic dependence on centrality, $p_\mathrm{T}$ and $\eta$, reflecting the fact that different ingredients of the initial state impact different regions of the phase space. For example, it was found the result depends on the centrality estimator used in the analysis, indicating a strong influence of volume fluctuations. On the other hand, the ratio of $\rho_2$ between the two systems is less sensitive to the centrality estimator, and in the ultra-central region, the value of the ratio suggests that $^{129}$Xe has large quadrupole deformation but with a significant triaxial. All current models fail to describe many of the observed trends in the data, pointing to the unprecedented constraining power enabled by this precision measurement.

Speaker: Somadutta Bhatta (Stony Brook University (US))

QM_ATLASvnpT_Somadutta.pdf

12:10 Results of femtoscopic correlations at CMS

Femtoscopic correlations of identified and unidentified hadrons are measured with data re-corded by the CMS experiment at the LHC over a broad multiplicity range and pair transverse momentum. The first femtoscopy measurements carried in CMS for all pair combinations of $\mathrm{K}^{0}_{\mathrm{S}}$, $\Lambda$ and $\overline{\Lambda}$ are reported. These identified particles are employed to perform $\mathrm{K}^{0}_{\mathrm{S}}\mathrm{K}^{0}_{\mathrm{S}}$, $\Lambda\overline{\Lambda}$ and $\mathrm{K}^{0}_{\mathrm{S}}\Lambda\oplus\mathrm{K}^{0}_{\mathrm{S}}\overline{\Lambda}$ femtoscopic correlations in pPb collisions at $\sqrt{s_{_{\mathrm{NN}}}} =$ 8.16 TeV, and of $\Lambda\Lambda\oplus\overline{\Lambda}~\!\!\overline{\Lambda}$ in PbPb collisions at $\sqrt{s_{_{\mathrm{NN}}}} =$ 5.02 TeV, for the first time. The shape of the correlation function is observed to largely vary for different particle pair species, revealing the effect of the strong final state interaction in each case. Charged particle correlations measured in pp at $\sqrt{s} =$ 0.9, 2.76, 7 and 13 TeV, pPb at $\sqrt{s_{_{\mathrm{NN}}}} =$ 5.02 TeV and peripheral PbPb collisions at $\sqrt{s_{_{\mathrm{NN}}}} =$ 2.76 TeV with the CMS detector are shown in addition. The invariant radii results for $\mathrm{K}^{0}_{\mathrm{S}}\mathrm{K}^{0}_{\mathrm{S}}$ in pPb and PbPb collisions show similar behavior with multiplicity and pair transverse momentum as observed for charged hadrons in all colliding systems and energies. The strong interaction scattering parameters, scattering length and effective range, are extracted from $\Lambda\Lambda\oplus\overline{\Lambda}~\!\!\overline{\Lambda}$ and $\Lambda\overline{\Lambda}$ correlations using the Lednick\'y-Lyuboshits model for both pPb and PbPb collisions, and compared with other experimental and theoretical results.

Speaker: Dener De Souza Lemos (University of Illinois at Chicago (US))

QM_04072022_DSLemos_v3.pdf

12:30 Femtoscopy of Protons, Light Nuclei, and Strange hadrons in Au+Au Collisions at the STAR experiment

Two-particle correlations at small relative momenta contain information about the space-time characteristics of the particle emitting source and final-state interaction effects. Light nuclei, such as deuteron ($d$), triton ($t$), and helium ($^{3}\mathrm{He}$, $^{4}\mathrm{He}$), are loosely bound objects that are expected to be formed at the late stage of relativistic heavy-ion collisions. The measurement of two-particle correlations for various light nuclei combinations provides a unique tool to obtain detailed information about the spatial and temporal evolution of the particle emitting source as well as the isospin dependence of strong interaction. This analysis can be further applied to investigate the production mechanism of light nuclei in heavy-ion collisions, such as coalescence vs. thermal production.

For the case of strange particles, such as kaons and hyperons, the correlation functions are sensitive to the early stage of the collision evolution and provide different information about particle-emitting sources compared to pions. Information on the final state interactions amongst the particles under study can also be extracted from the measurement. Further, one could investigate hyperon-nucleon interactions which is little known.

In this talk, we will present measurements of proton, light nuclei, and strange particle with charged and neutral kaons as well as $\Xi$ hyperons correlation functions in Au+Au collisions at the BES program and top RHIC energy. The experimental results will be compared with theory predictions to extract the size of emitting source and the properties of final state interactions. The collision energy and centrality dependence of the source size will be studied. Also, the implications for the production mechanism of light nuclei will be discussed.

Speaker: ke mi

QM2022_KeMi.pdf

12:50 Accessing the initial conditions of heavy-ion collisions with correlations and fluctuations of anisotropic flow in ALICE

The main goal of ultrarelativistic heavy-ion collisions is to create a new state of matter called quark-gluon plasma (QGP) and study its properties. One of the dominant uncertainties present in such a study originates from poorly constrained initial conditions. In this talk, we present the final results of anisotropic flow measurements with high-order cumulants for inclusive and identified hadrons over the transverse momentum range of 0.2 < $p_{\rm T}$ < 20 GeV/c in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV. The measurements are also performed for the inclusive charged hadrons with a large coverage in pseudorapidity of 3.5 < $\eta$ < 5.0. With the combinations of two- and multiparticle cumulants, the relative flow fluctuations are studied in both transverse and pseudorapidity directions, providing unique insights into initial eccentricity fluctuations. In addition, the investigation on the $p_{\rm T}$-dependent flow vector fluctuations, originating in the event-by-event fluctuations of the initial geometry, is performed in Pb-Pb collisions. For the first time, we separate the potential contributions from flow angle and flow magnitude fluctuations via two newly proposed flow observables and report the first discovery of both effects with a confidence of more than 5$\sigma$. Finally, the latest results of correlations between mean transverse momentum and anisotropic flow coefficient, $\rho(v^2_n, [p_{\rm T}])$, which are expected to provide direct access to the correlations between initial size and shape of the created hot QCD matter, will be shown for Pb-Pb and Xe-Xe collisions. Together with the comparisons to the various hydrodynamic model calculations, we will highlight that the models based on the T$_{\rm R}$ENTo initial state model and tuned using the Bayesian analyses fail to describe measured values of the $\rho(v^2_n, [p_{\rm T}])$. Results presented in this talk have a great potential to improve our knowledge of initial conditions and the properties of the QGP.

Speaker: Vytautas Vislavicius (University of Copenhagen (DK))

VVislavicius_QM2022.pdf

11:10 → 13:10 Parallel Session T09: Ultra-peripheral collisions: II

Convener: George Stephans (Massachusetts Inst. of Technology (US))

11:10 Studies of low-$x$ phenomena with the LHCb detector

With a unique geometry covering the forward rapidity region, the LHCb detector provides unprecedented kinematic coverage at low Bjorken-$x$ down to $x \sim 10^{-5}$ or lower. The excellent momentum resolution, vertex reconstruction and particle identification allow precision measurements down to very low hadron transverse momentum. In this contribution, we present the latest studies of the relatively unknown low-$x$ region using the LHCb detector, including recent measurements of charged and neutral hadron production, as well as direct photon and hadron correlations in proton-proton and proton-lead collisions. Comparisons to various theoretical model calculations are also discussed.

Speaker: Óscar Boente García (Universidade de Santiago de Compostela (ES))

lowx_QMLHCb_oboente_v2.pdf

11:30 $\rm{J/\psi}$ photoproduction results from ALICE

The diffractive photoproduction of $\rm{J/\psi}$ vector mesons is studied at the LHC with the ALICE detector in p--Pb and Pb--Pb ultra-peripheral collisions (UPCs), where the Pb ions act as powerful sources of quasi-real photons.

In this talk, the first measurement at the LHC of dissociative photoproduction of $\rm{J/\psi}$ off protons is presented; this process is sensitive to quantum fluctuations of the structure of the target at the subnucleon level. In addition, cross sections for the exclusive channel and for continuum dimuon production at small masses, were obtained in the same kinematic region. This latter process probes our simultaneous understanding, in a new kinematic region, of the photon flux coming off protons and off lead ions. We also present the transverse momentum dependence of $\rm{J/\psi}$ photoproduction on lead targets in Pb--Pb collisions at midrapidity, which is sensitive to the gluonic structure of Pb in the impact-parameter plane.

The measurement of $\rm{J/\psi}$ photoproduction off hadrons sheds light onto the initial state of QCD targets and provides important constraints to the initial conditions used in hydrodynamical models of heavy ion collisions.

Speaker: Tomas Herman (Czech Technical University in Prague (CZ))

QM-2022.pdf

11:50 Measurement of exclusive vector meson photoproduction in pPb and PbPb collisions with the CMS experiment

The exclusive photoproduction of vector mesons provides a unique opportunity to constrain the gluon distribution function within protons and nuclei. Measuring vector mesons of various masses over a wide range of rapidity and as a function of transverse momentum provides important information on the evolution of the gluon distribution within nuclei. A variety of measurements, including the exclusive J/$\psi$, $\rho$, and $\Upsilon$ meson production in pPb (at nucleon-nucleon center of mass energies of 5.02 and 8.16 TeV) and PbPb (5.02 TeV) collisions, will be presented as functions of squared transverse momentum and the photon-proton center of mass energy. Finally, compilations of these data and previous measurements are compared to various theoretical predictions.

Speaker: Kousik Naskar (Bhabha Atomic Research Centre (IN))

Kousik_CMS_QM22.pdf

12:10 Observation of $\gamma+\gamma$->$\tau+\tau$ in Pb+Pb collisions and constraints on the $\tau$-lepton g-2 with the ATLAS detector

This talk reports the observation of $\tau$-lepton pair production in ultraperipheral lead-lead collisions and a measurements of for the $\tau$-lepton anomalous magnetic moment, $a_{\tau}$. The dataset corresponds to an integrated luminosity of 1.44/nb of Pb+Pb collisions at 5.02 TeV recorded by the ATLAS experiment in 2018.

Speaker: Jakub Kremer (Johannes Gutenberg Universitaet Mainz (DE))

QM2022-ATLAS-yytautau.pdf

12:30 Anomalous electromagnetic moments of $\tau$ lepton from $\gamma \gamma \to \tau^+ \tau^-$ processes in ultrapheripheral Pb+Pb collisions at the LHC

We discuss the sensitivity of the process in ultraperipheral Pb+Pb collisions on the anomalous magnetic ($a_\tau$) and electric ($d_\tau$) moments of $\tau$ lepton at LHC energies. We derive the corresponding cross sections by folding the elementary cross section with the heavy-ion photon fluxes and considering semi-leptonic decays of both $\tau$ leptons in the fiducial volume of ATLAS and CMS detectors. We present predictions for total and differential cross sections, and for the ratios to $\gamma \gamma \to e^+ e^- (\mu^+\mu^-)$ process. These ratios allow to cancel theoretical and experimental uncertainties when performing precision measurements at the LHC. The expected limits on $a_\tau$ with existing Pb+Pb dataset are found to be better by a factor of two comparing to current best experimental limits and can be further improved by another factor of two at High Luminosity LHC.

[1] Mateusz Dyndal, Mariola Klusek-Gawenda, Matthias Schott and Antoni Szczurek,
Phys. Lett. B809 (2020) 135682.

Speaker: Dr Mariola Klusek-Gawenda (Institute of Nuclear Physics Polish Academy of Sciences)

MKG_QM2022_tau.pdf

12:50 Exclusive J/Psi production in ultraperipheral Pb+Pb collisions to NLO pQCD

Coherent exclusive J/Psi photoproduction in ultraperipheral heavy-ion collisions (UPCs) at the LHC, Pb+Pb $\rightarrow$ Pb+J/Psi +Pb, has traditionally been suggested as an efficient probe of nuclear gluon distributions. While in the leading order pQCD this is so, we show that the situation changes rather dramatically at NLO. We present the first NLO study of this process in heavy-ion collisions [1], building our numerical code on the NLO calculation of Ref. [2]. Approximating the generalized parton distributions involved in this process with collinear PDFs, we quantify the NLO contributions in the cross section, show that the real part of the amplitude must not be neglected, study the nuclear quark-PDF contributions, and chart the uncertainties due to the scale choice and PDFs. We compare our calculations with ALICE, CMS and LHCb J/Psi data in Pb+Pb UPCs, exclusive J/Psi photoproduction data from HERA, and LHCb data in p+p. We show that for the y-differential cross sections the scale dependence is significant but a scale choice can be found which reproduces the UPC data both at 2.76 and 5.02 TeV collision energies. In particular, we show that the NLO gluon contribution partly cancels against the LO one in the amplitude, making the process clearly more sensitive to the nuclear quark PDFs than thought before.

[1] K.J. Eskola, C.A. Flett, V. Guzey, T. Loytainen and H. Paukkunen, work in progress.

[2] D.Yu. Ivanov, A. Schafer, L. Szymanowski, G. Krasnikov, Eur. Phys. J. C 34 (2004) 297.

Speaker: Topi Loytainen

Quark_Matter_2022.pdf

11:10 → 13:10 Parallel Session T11: Heavy flavors, quarkonia, and strangeness production: III

Convener: Enrico Scomparin (Universita e INFN Torino (IT))

11:10 Constraining hadronization processes with charm baryons in pp and p-Pb collisions with ALICE

In this contribution, we present the latest measurements of $\mathrm{D}^0$, $\mathrm{D}^+$ and $\mathrm{D_s}^+$ mesons together with the final measurements of $\Lambda_\mathrm{c}^+$, $\Xi_\mathrm{c}^{0,+}$, $\Sigma_\mathrm{c}^{0,++}$, and the first measurement of $\Omega_\mathrm{c}^0$ baryons performed with the ALICE detector at midrapidity in pp collisions at $\sqrt{s}=5.02$ and $\sqrt{s}=13$ TeV. Recent measurements of charm-baryon production at midrapidity in small systems show a baryon-to-meson ratio significantly higher than that in $\mathrm{e^+e^-}$ collisions, suggesting that the fragmentation of charm is not universal across different collision systems. Thus, measurements of charm-baryon production are crucial to study the charm quark hadronization in a partonic rich environment like the one produced in pp collisions at the LHC energies.
Furthermore, the recent $\Lambda_\mathrm{c}^+/\mathrm{D}^0$ yield ratio, measured down to $p_\mathrm{T}=0$, and the new $\Xi_\mathrm{c}^{0,+}/\mathrm{D}^0$ yield ratio in p-Pb collisions will be discussed. The measurement of charm baryons in p-nucleus collisions provides important information about possible additional modification of hadronization mechanisms as well as on cold nuclear matter effects and on the possible presence of collective effects that could modify the production of heavy-flavour hadrons.
Finally, the first measurements of charm fragmentation fractions and charm production cross section at midrapidity per unit of rapidity will be shown for both pp and p-Pb collisions using all measured single charm ground state hadrons.

Speaker: Mattia Faggin (Universita e INFN, Padova (IT))

QM2022_mfaggin_v6.pdf

11:30 Measurements of $\Lambda_{c}^{+}$ and X(3872) production in PbPb for the studies of charm hadronization with CMS

Being a powerful probe of the quark-gluon plasma (QGP), charm quarks have been widely studied in heavy-ion collisions. They have provided unique insights into the parton energy loss and the degree of thermalization in the hot medium, but an inadequate knowledge of the hadronization processes has hampered the interpretation of experimental results. In heavy-ion collisions, charm hadron production can occur via coalescence, where charm quarks combine with the surrounding light quarks in the QGP. The relative coalescence contribution is expected to be more significant for hadrons with a larger number of constituent quarks, so the modification of the baryon-to-meson ratio in heavy-ion collisions will reflect the effect of coalescence, and the effect is stronger for particles with more than three constituent quarks. Therefore, measurements of $\Lambda_{c}^{+}$ and X(3872) production can provide important input to the understanding of coalescence. The high luminosity datasets collected by the CMS detector have been used to measure $\Lambda_{c}^{+}$ and X(3872) production via $\Lambda_{c}^{+} \to p^{+} K^{-} \pi^{+}$ and $\mathrm{X}(3872) \to \mathrm{J}/\psi \pi^{+}\pi^{-}$. Results of the ratios of $\Lambda_{c}^{+}$ over $D^{0}$ yields in pp and PbPb collisions and of X(3872) over $\psi(2S)$ yields in PbPb collisions will be shown. The nuclear modification factors of $\Lambda_{c}^{+}$ will also be presented.

Speaker: Jing Wang (Massachusetts Inst. of Technology (US))

20220407_QM22_JingWang_v4.pdf

11:50 $\Upsilon$(nS) meson production in Pb+Pb and $pp$ collisions

Measurements of bottomonium states in heavy-ion collisions provide a powerful tool to study both initial-state effects on heavy-quark production and final-state interactions between heavy quarks and the quark-gluon plasma (QGP).

The ATLAS experiment at LHC has measured the production of bottomonium states $\Upsilon$(1S), $\Upsilon$(2S) and $\Upsilon$(3S), in Pb+Pb and $pp$ collisions at a center-of-mass energy per nucleon pair of 5.02 TeV. The data correspond to integrated luminosities of 1.38 nb$^-1$ of Pb+Pb data collected in 2018, 0.44 nb$^-1$ of Pb+Pb data collected in 2015, and 0.26 fb$^-1$ of pp data collected in 2017. The final ATLAS result on the production of three bottomonium states will be reported. The mesurement in Pb+Pb collisions is compared to that in $pp$ collisions to extract the nuclear modification factor, $R_{\mathrm{AA}}$, as a function of event centrality, $p_{\mathrm{T}}$ and rapidity, and compared to several theoretical models.

We will also present a new measurement studying the relationship between the production of hard and soft particles through the correlation of Upsilon meson states with the inclusive-charged particle yields. The analysis is performed using the full-luminosity ATLAS Run-2 13 TeV $pp$ data. A description of the technical challenges associated with a heavy-ion style analysis in high-pileup $pp$ data will be shown, as well as the results and their physics implications.

Speaker: Alexandre Lebedev (Iowa State University (US))

QM2022-Lebedev-Upsilons-v1.pdf

12:10 An Investigation of Charm Quark Jet Spectrum and Shape Modifications in Au+Au Collisions at $\sqrt{s_{NN}} = 200$ GeV

Partons (quarks/gluons) in heavy-ion collisions interact strongly with the Quark-Gluon Plasma (QGP), and hence have their energy and shower structure modified compared to those in vacuum, e.g., those produced in proton-proton collisions. Theoretical calculations predict that radiative energy loss, which is the dominant mode of energy loss for gluons and light quarks in the QGP, is suppressed for heavy quarks (such as charm and bottom) at low transverse momenta ($p_{\text{T}}$). A measurement of the $D^0 (c\bar{u})$ meson radial profile in jets from the CMS experiment at the LHC hints at its modification at low $D^0$ $p_{\text{T}}$ in heavy-ion collisions, which is qualitatively different from that of the inclusive hadrons. The excellent secondary vertex resolution provided by the Heavy Flavor Tracker in the STAR experiment at RHIC enables reconstruction of $D^0$ mesons at low $p_{\text{T}}$ with high significance, making STAR ideal for similar measurements.

We report the first measurements of the $D^0$ meson tagged jet $p_{\text{T}}$ spectra and $D^0$ meson radial profile in anti-$k_\text{T}$ jets from Au+Au collisions at $\sqrt{s_{\text{NN}}} = 200$ GeV at RHIC, collected by the STAR experiment in 2014. We compare the results to PYTHIA-8 predictions at the same center-of-mass energy. We also report the nuclear modification factor $R_{\text{CP}}$ for these $D^{0}$-meson tagged jets. Such measurements are expected to shed light on parton flavor and mass dependencies of jet quenching, and constrain theoretical models.

Speaker: Diptanil Roy (Rutgers University)

QMTalk_DiptanilRoy.pdf

12:30 Heavy quarkonium dynamics in the QGP with a quantum master equation approach

In recent years, a significant theoretical effort has been made towards a dynamical description of quarkonia inside the Quark-Gluon Plasma (QGP), using the open quantum systems formalism. In this framework, one can get a real-time description of a quantum system (here the quarkonium) in interaction with a thermal bath (the QGP) by integrating out the bath degrees of freedom and studying the system reduced density matrix.

We investigate the real-time dynamics of a correlated heavy quark-antiquark pair inside the QGP using novel coupled quantum master equations derived from first QCD principles and based on the work of Blaizot & Escobedo [1]. The equations are solved numerically in 1D to lessen computing costs and are used for the first time to gain insight on the dynamics in both a static and evolving medium following a Björken-like temperature evolution. Several initial conditions will be explored and a first feasability analysis of a semi-classical treatment will be presented, in order to see if this approach can be used to treat multiple charm-anticharm pairs at the same time.

[1]-J. P. Blaizot and M. A. Escobedo, Quantum and classical dynamics of heavy quarks in a quark-gluon plasma, J. High Energy Phys. 06 (2018) 034.

Speaker: Stéphane DELORME

QM2022_DELORME.pdf

12:50 Studies of heavy quark diffusion in QGP with nonprompt $D^0$ collectivity and jet-$D^0$ angular correlations in PbPb collisions

Measurements of the correlations of the final-state heavy flavor hadrons are of great interest since they provide information about the initial collision geometry and its fluctuation. More importantly, those measurements could reveal the mass dependence of parton energy loss and quark diffusion in the Quark-Gluon Plasma (QGP). In this talk, we report the first measurement of the azimuthal anisotropy of nonprompt $D^0$ in PbPb collisions at $\sqrt{s_{_{\mathrm{NN}}}}=$ 5.02 TeV. The elliptic ($v_2$) and triangular ($v_3$) coefficients are performed as functions of $D^0$ transverse momentum $p_\mathrm{T}$, in three centrality classes. Compared to the results from promptly produced $D^0$, the nonprompt $D^0$ $v_2$ flow coefficients are systematically lower. But those results have a similar dependence on $p_\mathrm{T}$ and centrality. A non-zero $v_3$ coefficient of the nonprompt $D^0$ is seen in PbPb data. We also present the first azimuthal angular correlation measurement between jets and $D^0$ mesons in pp and PbPb collisions. The jet-$D^0$ correlation measurement is performed using jets with $p_\mathrm{T} > 60$ GeV and $D^0$ mesons with $p_\mathrm{T} > 4$ GeV. In PbPb collisions at 5.02 TeV, compared to the pp, the $D^0$ distribution hints at the diffusion of charm quarks in the medium, created in heavy-ion collisions. The results could provide new constraints on the mechanism of the heavy quark diffusion and energy loss in the QGP.

Speaker: Milan Stojanovic (Purdue University (US))

MStojanovic_QM2022.pdf

11:10 → 13:10 Parallel Session T12: New theoretical developments

Convener: Michał Praszałowicz (Instytut Fizyki Teoretycznej UJ)

11:30 Characteristics of early time gluon fields in relativistic heavy ion collisions

We present some analytic results that describe the gluon field, or glasma, that exists at very early times after a collision of relativistic heavy ions at proper time $\tau=0$. We use a Colour Glass Condensate approach, and perform an expansion in $\tau$. We show that the expansion to order $\tau^6$ can be trusted to about $\tau=0.05$ fm/c. We calculate the transverse and longitudinal pressures and show that for $\tau \lt 0.05$ fm/c they move towards their equilibrium values of one third of the energy density. We study the spatial eccentricity of the plasma, and the Fourier coefficients of the azimuthal momentum distribution. Our results for the Fourier coefficients are larger than expected, which contradicts the usual assumption that anisotropy is mostly generated during the hydrodynamic evolution of the plasma. We find a significant correlation between the elliptic flow coefficient and the eccentricity, which indicates that the spatial inhomogeneity introduced by the initial geometry is effectively transmitted to the azimuthal distribution of the gluon momentum field, even at very early times. This result is interesting because correlations of this kind are characteristic of the onset of hydrodynamic behaviour. We also calculate the angular momentum of the glasma and obtain results that are many orders of magnitude smaller than the initial angular momentum of two ions colliding with non-zero impact parameter. This indicates that most of the angular momentum carried by the valence quarks is not transmitted to the glasma. The result is significant because it contradicts the picture of a rapidly rotating initial glasma state.

Speaker: Margaret Carrington

QM-carrington-2022.pdf

11:50 Far-from-equilibrium attractor in non-conformal plasmas

We explore the far-from-equilibrium dynamics of a (0+1)-dimensionally expanding system of massive particles with Bjorken symmetry using kinetic theory and hydrodynamics. By comparing the decay of various initializations on the attractor in both frameworks, we test the effectiveness of hydrodynamics in providing an accurate description of the underlying kinetic theory in far-off-equilibrium regimes. We demonstrate that inclusion of even a small mass scale in units of the system’s local temperature drastically alters the well-known attractor behavior of the shear Reynolds number as observed in a weakly-coupled gas with exactly massless excitations. For generic nonzero particle mass, neither shear nor bulk viscous pressure relaxes to a far-from-equilibrium attractor; universal hydrodynamic behavior is manifest only at small values of the inverse Reynolds numbers. In kinetic theory, we find that the scaled longitudinal pressure exhibits fast decay to an early-time attractor, driven by the rapid longitudinal expansion of the medium [1]. Second-order dissipative hydrodynamics, based on a gradient expansion around local thermal equilibrium, fails to accurately describe the attractor. These results will be discussed in the light of fixed lines and fixed points of non-conformal kinetic theory and hydrodynamics. A modified anisotropic hydrodynamic prescription that provides excellent agreement with kinetic theory and reproduces the attractor will be presented [2].

[1] Non-conformal attractor in boost-invariant plasmas, C. Chattopadhyay, S. Jaiswal, L. Du, U. Heinz, and S. Pal, arXiv: 2107.05500 (2021)

[2] On non-conformal kinetic theory and hydrodynamics for Bjorken flow, S. Jaiswal, C. Chattopadhyay, L. Du, U. Heinz, and S. Pal, arXiv: 2107.10248 (2021)

Speaker: Sunil Jaiswal (Tata Institute of Fundamental Research)

QM2022_sunil_jaiswal.pdf

12:10 A first step towards quantum simulating jet evolution in a dense medium

The fast development of quantum technologies over the last decades has offered a glimpse to a future where the quantum properties of multi-particle systems might be more fully understood. So far, quantum computing has seen ample application in areas such as quantum chemistry or condensed matter, but its usage in high energy physics is still in its infancy. In the particular case of QCD jets, these technologies might offer a way to, for the first time, fully understand the intricate interference pattern arising from the multi-parton cascade. In jet quenching, such aspects are intimately related to the natural scales at which the jet probes the medium. In this talk, we introduce a strategy to quantum simulate single particle evolution in a stochastic background field. We discuss how jet evolution can be translated to a digital quantum circuit and which measurement protocols can be implemented to extract physically relevant quantities. Future extensions of this strategy to include gluon radiation are discussed.

Speaker: João Barata

Barata.pdf

12:30 The PanScales project: parton showers beyond leading-log accuracy

Parton showers lie at the core of general purpose Monte Carlo event generators. They aim at correctly describing the phase-space for QCD branchings across disparate energy scales. A natural question, largely overlooked in the literature, is up to which degree of logarithmic accuracy do parton showers meet this goal. In this talk, I’ll present a new class of dipole showers for hadronic collisions, the PanScales showers, that are next-to-leading log accurate according to the criteria first introduced in [1]. In turn, I’ll show that a standard dipole shower mimicking the one used in Pythia, Herwirg or Sherpa fails to reach NLL accuracy in certain global observables. To end up, I’ll outline some ideas on how to incorporate the PanScales showers into jet quenching Monte-Carlo event generators.
[1] Phys.Rev.Lett. 125 (2020) 5, 052002

Speaker: Dr Alba Soto Ontoso (IPhT)

qm_aso.pdf

12:50 Non-perturbative determination of the collisional broadening kernel and medium-induced radiation in QCD plasmas

Collisional broadening in QCD plasmas leads to the emission of medium induced radiation, which governs the energy loss of highly energetic particles or jets. While recent studies have obtained non-perturbative contributions to the collisional broadening kernel $C(b_{\bot})$ using lattice simulation of the dimensionally reduced long-distance effective theory of QCD, Electrostatic QCD (EQCD) [1], so far all phenomenological calculations of jet quenching rely on perturbative determinations of the collisional broadening kernel. By matching the short-distance behavior of the lattice extracted EQCD broadening kernel [2], we determine the fully matched QCD broadening kernel non-perturbatively. We present results for the collisional broadening kernel in impact-parameter ($C_{\rm QCD}(\bf{b}_\perp)$) and momentum space ($C_{\rm QCD}(\bf{q}_\perp)$) and employ them to determine the rates of medium induced radiation in infinite and finite size QCD plasmas [3]. By contrasting our results with leading and next-to-leading order perturbative determinations as well as various approximations of the splitting rates employed in the literature, we investigate the effect of the non-peturbative determination of $C_{\rm QCD}(\bf{q}_\perp)$ on medium-induced radiation rates.

[1] - G. D. Moore and N. Schlusser, Phys. Rev., vol. D100, no. 3, p. 034510, 2019

[2] - G. D. Moore, S. Schlichting, N. Schlusser and I. Soudi, JHEP 10 (2021), 059

[3] - S. Schlichting,and I. Soudi, In preparation

Speaker: Dr Ismail Soudi (Wayne State University)

BroadeningKernel.pdf

13:10 → 14:40 Lunch

14:40 → 16:20 Parallel Session T11: Heavy flavors, quarkonia, and strangeness production: IV

Convener: Elena Bratkovskaya

14:40 Charmonium production in Pb–Pb collisions with ALICE

Charmonium production is a direct probe of deconfinement in heavy-ion collisions. For J/$\psi$, a bound state of ${c}\bar{c}$ quarks, its (re-)generation within the QGP or at the phase boundary, is found to be the dominant production mechanism at low transverse momentum ($p_{\rm T}$) and in central Pb–Pb collisions at the LHC energies. The relative production of the $\psi$(2S) excited state with respect to the J/$\psi$ is one possible discriminator between the two different regeneration scenarios. In addition, the non-prompt component of J/$\psi$ production from b-hadron decays allows one to access the interaction of b-hadrons with the QGP down to low transverse momentum. In this talk, we present for the first time new results on the $\psi$(2S)-to-J/$\psi$ double ratio in Pb–Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV with respect to a new pp reference with improved precision, thanks to a new Run 2 data sample with an increase of the statistics collected by a factor 10. The combined Run 2 data set of ALICE allows the extraction of a significant $\psi$(2S) signal in central Pb–Pb collisions at forward rapidity down to 0 transverse momentum. The $\psi$(2S) nuclear modification factor $R_{AA}$ as a function of $p_{\rm T}$ and centrality will also be shown, as well as the inclusive J/$\psi$ $R_{AA}$ at forward rapidity. At midrapidity, the inclusive, prompt and non-prompt J/$\psi$ $R_{AA}$ as a function of centrality and $p_{\rm T}$ will be presented, based on the full Run 2 statistics. The extraction of the non-prompt J/$\psi$ fraction extends down to very low $p_{\rm T}$ and its precision is improved significantly compared to the previous publications. Additionally, the measurements of inclusive, prompt and non-prompt J/$\psi$ in p–Pb collisions will be discussed in view of the interpretation of the Pb–Pb data. All the results will be compared with model calculations.

Speaker: Jon-Are Saetre (University of Bergen (NO))

CharmoniumProductionPbPbALICE.pdf

15:00 Heavy flavor production at LHCb

Charm and bottom quark production is an important experimental observable that sheds light on the heavy quark interaction with the nuclear medium. With high statistics datasets, tracking and PID at very low transverse momentum, and
excellent vertexing capabilities, LHCb performs precision measurements of a rich set of heavy flavor hadrons, including B mesons, open charm hadrons and charmonia. These capabilities allow for precise studies of strangeness enhancement, baryon enhancement, and charmonia suppression in various colliding systems from $pp$ to $p$Pb and PbPb. We will present these results along with comparisons to theoretical calculations.

Speaker: Benjamin Audurier (Centre national de la recherche scientifique)

HF_audurier_qm2022_v6.pdf

15:20 New measurements in fixed-target collisions at LHCb

The LHCb spectrometer has the unique capability to function as a fixed-target experiment by injecting gas into the LHC beampipe while proton or ion beams are circulating. The resulting beam+gas collisions cover an unexplored energy range that is above previous fixed-target experiments, but below the top RHIC energy for AA collisions. Here we present new results on antiproton and charm production from pHe, pNe, and PbNe fixed-target collisions at LHCb. Comparisons with existing measurements and various theoretical models of particle production and transport through the nucleus will be discussed.

Speaker: Jiayin Sun (Universita e INFN, Cagliari)

Smog_QM2022_sun_final.pdf

15:40 $J/\psi$ Forward rapidity azimuthal anisotropy in Au+Au collisions and multiplicity dependence in $p$+$p$ and $p$+Au at $\sqrt{s_{NN}}$=200 GeV measured by the PHENIX Experiment

Nearly twenty $c\bar{c}$ pairs are produced in central Au+Au collisions at
the top RHIC energy of $\sqrt{s_{NN}}=$200 GeV, with the largest yields at
mid-rapidity. The enhanced production of charmonium states from combinations of independently produced charm quarks could contribute to the observation that, in Au+Au collisions at RHIC, J/$\psi$ yields are smaller at forward rapidity than at mid-rapidity relative to observations in $p+p$ collisions at the same energy. A signature of such charmonium coalescence could be the presence of J/$\psi$ flow. The PHENIX experiment collected a large sample of J/$\psi\rightarrow \mu^+\mu^-$ decays at the pseudorapidity region of 1.2$<\eta<$2.2 in Au+Au collisions during the 2014 and 2016 runs. These data will allow the most precise measurement so far of J/$\psi$ flow component $v_2$ in a region where the number of charm quark pairs is smaller than at mid-rapidity.

The PHENIX experiment has also a large sample of J$/\psi\rightarrow\mu^+\mu^-$ decays measured at a forward rapidity of 1.2$<\eta<$2.2 in $p$+$p$ and $p$+Au collisions at $\sqrt{s_{NN}}$=200 GeV. The yields can be measured as a function of the multiplicity determined over a broad range of rapidity, a golden channel for multiparton interaction studies. A comparison between yields observed in $p$+$p$ and $p$+Au at the same multiplicity could help explain how the multiparton interactions (in $p$+$p$) can affect the measurement of multinucleon interactions (in $p$+Au), as well as the measured nuclear modification factors, after evaluating the competing effects such as charmonium breakup in co-moving particles. This presentation will show preliminary results of J/$\psi$ azimuthal anisotropy and the status of the J/$\psi$ studies in different event activity categories.

Speaker: Luis Bichon (Vanderbilt University)

Quark Matter Final Presentation.pdf

16:00 Recent heavy flavor results from the STAR experiment

Quarkonia and open-charm hadrons are important probes to study the properties of the Quark-Gluon Plasma (QGP). Heavy quarks are produced predominantly in hard partonic scatterings at the very early stage of heavy-ion collisions, and subsequently experience the whole evolution of the hot and dense medium. Measurements of quarkonia and open charm hadron production yields and $J/\psi$ anisotropic flow provide comprehensive information about the QGP properties, such as degree of charm quark thermalization, quarkonium dissociation as well as the charm quark hadronization mechanisms.

In this talk, we will present measurements of $J/\psi$ elliptic flow in Ru+Ru and Zr+Zr collisions at $\sqrt{s_{\rm{NN}}}$ = 200 GeV, and quarkonium nuclear modification factors in p+Au, Ru+Ru and Zr+Zr collisions at $\sqrt{s_{\rm{NN}}}$ = 200 GeV as well as in Au+Au at $\sqrt{s_{\rm{NN}}}$ = 54.4 GeV. We will also present measurements of the nuclear modification factors for $D^{0}$ and $D^{\pm}$ mesons, the transverse momentum and centrality dependences of $D^{\pm}$ , $D_{s}$, and $\Lambda_{c}$ over $D^{0}$ meson yield ratios as well as the total charm quark production cross section in Au+Au collisions at $\sqrt{s_{\rm{NN}}}$ = 200 GeV.

Speaker: Ziyue Zhang (University of Illinois at Chicago)

qm2022_zyzhang.pdf

14:40 → 16:20 Parallel Session T13: Electroweak probes: I

Convener: Sasha Milov

14:40 Direct photon production and HBT correlations in Pb–Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV with the ALICE experiment

Measurements of direct photons can provide valuable information on the properties and dynamics of the quark-gluon plasma (QGP) by comparing them to model calculations that describe the whole evolution of the system created in heavy-ion collisions, from the initial conditions to the pre-equilibrium, QGP, and hadronic phases.
In the ALICE experiment, photons can be reconstructed either by using the calorimeters or via conversions in the detector material. The photon conversion method benefits from an excellent energy resolution and is able to provide direct photon measurements down to $p_{\rm T}$ = 0.4 GeV/c . For Hanbury Brown and Twiss (HBT) correlation studies, the detector setup can be exploited to combine a conversion photon with a calorimeter photon, such that near-zero opening angles are measured.
In this talk, we present the first measurements of direct photon production in Pb–Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV by ALICE, including direct photon spectra from central to peripheral events. The latest results of the first analysis of photon HBT correlations will be shown as well.

Speaker: Meike Charlotte Danisch (Ruprecht Karls Universitaet Heidelberg (DE))

danisch_directPhotons.pdf

danisch_directPhotons_v2.pdf

15:00 Light-by-light scattering cross-section measurements at LHC

We present the first combination of light-by-light scattering ($\gamma\gamma\rightarrow \gamma\gamma$) cross-section measurements at LHC, using lead-lead data recorded by the ATLAS and CMS Collaborations at $5.02\,\text{TeV}$ and corresponding to integrated luminosities of 2.2 and $0.39\,\text{nb}^{-1}$, respectively. The combined cross-section is $115\pm 19\,\text{nb}$, with the two measurements contributing with factors of 0.8 and 0.2, accordingly. The combined result improves upon the best individual determination of $\gamma\gamma\rightarrow\gamma\gamma$ by approximately 10%, and it is consistent with the standard model prediction within two standard deviations. For the first time, we calculate the potential contribution of the $\eta_b(1S)$ meson production to the $\gamma\gamma\rightarrow\gamma\gamma$ invariant mass distributions, by calculating its inclusive photoproduction cross-section.

Speaker: Dr Georgios Krintiras (The University of Kansas (US))

arXiv:2204.02845

LbyL_QM22

LbyL QM22.pdf

15:20 Thermal radiation and direct photon production in Pb-Pb and pp collisions with dielectrons in ALICE

Electromagnetic probes such as photons and dielectrons are a unique tool to study the space-time evolution of the hot and dense matter created in ultra-relativistic heavy-ion collisions. They are produced by a variety of processes during all stages of the collision with negligible final-state interactions. At low dielectron invariant mass ($m_{\rm ee}$), thermal radiation from the hot hadron gas contributes to the dielectron spectrum via decays of $\rho$ mesons, whose spectral function is sensitive to chiral-symmetry restoration. At larger $m_{\rm ee}$, thermal radiation from the QGP carries information about the early temperature of the medium. It is nevertheless dominated by a large background of correlated heavy-flavour hadron decays affected by energy loss and flow in the medium. Alternatively, the transverse momentum ($p_{\rm T,ee}$) of virtual direct photons, including thermal photons at low $p_{\rm T,ee}$, can be extracted from the dielectron data together with inclusive photon measurements. In proton--proton (pp) collisions, such measurement serves as a fundamental test for perturbative QCD calculations and as a baseline for the studies in heavy-ion collisions. Recently, pp collisions with high charged-particle multiplicities have been found to exhibit interesting phenomena showing surprising similarities with those in heavy-ion collisions. Low-mass dielectrons could provide additional information regarding the underlying physics processes in such collisions.

In this talk, the latest ALICE results on dielectron studies in Pb-Pb and pp collisions at the center-of-mass energies of $\sqrt{s_{\rm NN}}$ = 5.02 TeV and 13 TeV will be presented using the large data sample collected during the LHC Run 2. The results will be compared to the expected dielectron yield from known hadronic sources and predictions for thermal radiation from the medium. The production of direct photons in the different colliding systems including high-multiplicity pp collisions will be discussed.

Speaker: Jerome Jung (Goethe University Frankfurt (DE))

QM22_dielectrons_jjung_v10.pdf

15:40 Temperature measurement via thermal dileptons in Au+Au collisions at 27 and 54.4 GeV with the STAR experiment

Due to the minimal interactions with the medium constituents, thermal dileptons emitted throughout the medium evolution are suggested as excellent probe of the hot QCD medium created in relativistic heavy-ion collisions. The invariant mass distribution of thermal dileptons can reveal the temperature of their emitting source without suffering from the blue-shift effect. By analyzing the invariant mass distributions of thermal dileptons in the in-medium $\rho$ meson dominant region and the QGP thermal radiation dominant region, we can extract the temperatures of hot QCD matter averaged over the dense hadronic phase and the deconfined partonic phase (QGP), respectively.

In this talk, we will present the latest measurements of the dielectron mass spectra and the extracted medium temperature in Au+Au collisions at $\sqrt{s_{\text{NN}}}$ $=27$ GeV and 54.4 GeV with the STAR experiment. The dependencies of medium temperature on the collision centralities and the collision energies will be discussed together with the NA60 and HADES measurements.

Speaker: Zaochen Ye (Rice University (US))

Slides_T_via_Thermal_Dileptons_AuAu_STAR_ZaochenYe_QM22_v13.pdf

16:00 Opportunities with ultra-soft photons: Bremsstrahlung from stopping

We examine the spectrum of bremsstrahlung photons that results from the stopping of the initial net charge distributions in ultra-relativistic nucleus-nucleus collisions at the LHC. This effect has escaped detection so far since it becomes sizeable only at very low transverse momentum and at sufficiently forward rapidity. We compute the spectra of photon yields from different models of initial charge-rapidity distributions and discuss the distinguishability of the different models. We argue that it may be within reach of the next-generation LHC heavy-ion detector ALICE-3 that is currently under study, and comment on the physics motivation for measuring it.

Based on:  Sohyun Park, Urs Achim Wiedemann, Phys.Rev.C 104 (2021) 4, 044903 and additional model studies.

Speaker: Sohyun Park (CERN)

QM2022_SohyunPark.pdf

14:40 → 16:20 Parallel Session T14: Hadron production and collective dynamics: I

Convener: Claudia Ratti

14:40 Strange particle collectivity in pPb and PbPb

The collective behavior of \ensuremath{\mathrm{K^0_S}} and \ensuremath{\Lambda}/\ensuremath{\bar{\Lambda}} strange hadrons is studied using the scalar-product and multiparticle correlation methods. Proton-lead (pPb) collisions at the nucleon-nucleon center-of-mass energy $\sqrt{s_{\mathrm{NN}}} =$ 8.16 TeV and lead-lead (PbPb) collisions at $\sqrt{s_{_{\mathrm{NN}}}} =$ 5.02 TeV are investigated. The data samples were collected by the CMS experiment at the LHC. Nonflow effects in the pPb collisions are investigated by a subevent cumulant analysis and by excluding events where a jet with transverse momentum greater than 20 GeV is present. The jet exclusion study allows for a quantitative estimate of the dijet contribution to higher-order cumulants in the pPb system. For the first time, the collectivity of strange particles is observed in pPb collisions. A comparison of the pPb and PbPb results for both strange particles and charged hadrons shows how event-by-event flow fluctuations are affected by the system size.

Speaker: Quan Wang (The University of Kansas (US))

QM2022.pdf

15:00 Production yield and azimuthal anisotropy measurements of strange hadrons from BES at STAR

Searches for the onset of deconfinement are one of the main motivations of the Beam Energy Scan (BES) program at RHIC. Strangeness production has been suggested as a sensitive probe to the early-time dynamics of the deconfined matter, due to their small hadronic interaction cross section, early freezeout from the medium and short lifetime for some resonances, e.g. $K^{*0}$. The BES Phase I (BES-I) data taken during 2010 and 2011 have indicated signatures of the first-order phase transition and potential changes of medium properties at low energies. However, the statistics collected during BES-I is not sufficient to draw definitive conclusions. Since 2018, STAR has accumulated high statistics Au+Au datasets at various energies below 27 GeV during BES-II program.

Measurements of yield and flow harmonic coefficients ($v_{1}$, $v_{2}$, and $v_{3}$) of $K_{S}^{0}$, $\Lambda$, $\Xi$, $\Omega$, and $\phi$ from BES-II Au+Au collisions at $\sqrt{s_{NN}}$ = 3 - 27 GeV with both fixed-target and collider modes will be presented in this talk. The strange hadron spectra, nuclear modification factors, particle ratios, rapidity density distributions, and flow coefficients will be reported. The physics implications on the collision dynamics from these measurements will be discussed. The energy dependence of hadronic phase lifetime will also be studied through measurements of the mass, width, and invariant yields of $K^{*0}$ using BES-I data ($\sqrt{s_{NN}}$ = 7.7-39 GeV). The average transverse momenta, as well as the resonance to non-resonance particle ratios will be shown and compared to measurements at SPS and LHC energies.

Speaker: Aswini Kumar Sahoo (IISER,Berhampur)

QM2022_Aswini_v6.pdf

15:20 Temperature and net baryochemical potential dependence of $\eta/s$ in a hybrid approach

In this work, the qualitative impact of the net baryochemical potential dependence of the shear viscosity to entropy density ratio $\eta/s$ in hydrodynamical simulations is studied. The effect of a predicted non-constant $\eta/s(\mu_B)$ is largely unexplored in hydrodynamic simulations. Previous studies focus only on a temperature dependence[1-3] or even only a constant effective shear viscosity[4]. This work addresses this issue by studying qualitatively the effect of a generalized $\eta/s(T,\mu_B)$ in the novel hybrid approach SMASH-vHLLE, composed of the hadronic transport approach SMASH[5] and the (3+1)d viscous hydrodynamic code vHLLE[6]. In order to reduce the bias of the result on the equation of state used in the hydrodynamic part of the model, $\eta/s$ is parameterized directly in the energy density and baryon number density. The parameterization takes into account the constraints of matching to the transport coefficients in the hadronic phase[7], as well as of recent Bayesian analysis results. This work compares the impact of the density dependence for different system sizes and energies and constrains the behaviour of $\eta/s(T,\mu_B)$ by ruling out regions of the parameter space. This is achieved by comparing the observables with experimental results in the RHIC - BES region $\sqrt{s_{NN}}$= 4.3 - 17.3 GeV, as the effect of this generalisation is especially relevant for intermediate collision energies, for which the system is in equilibrium for a relevant amount of time, but the net baryochemical potential does not vanish.

References
[1] J. E. Parkkila, A. Onnerstad, F. Taghavi, C. Mordasini, A. Bilandzic und D. J. Kim, New constraints for QCD matter from improved Bayesian parameter estimation in heavy-ion collisions at LHC, 2021.
[2] D. Everett u. a. (JETSCAPE), „Phenomenological constraints on the transport properties of QCD matter with data-driven model averaging“, Phys. Rev. Lett. 126, 242301 (2021).
[3] D. Everett u. a. (JETSCAPE), „Multisystem Bayesian constraints on the transport coefficients of QCD matter“, Phys. Rev. C103,054904 (2021).
[4] J. Auvinen, J. E. Bernhard, S. A. Bass und I. Karpenko, „Investigating the collision energy dependence of $\eta$/s in the beam energy scan at the BNL Relativistic Heavy Ion Collider using Bayesian statistics“, Phys. Rev. C97, 044905 (2018).
[5] https://github.com/smash-transport/smash
[6] https://github.com/yukarpenko/vhlle
[7] J.-B. Rose, J. M. Torres-Rincon, A. Schäfer, D. Oliinychenko and H. Petersen, "Shear viscosity and resonance lifetimes in the hadron gas", Nuclear Physics A 982, 807-810 (2019).

Speaker: Niklas Götz (Institute for Theoretical Physics, Goethe University, Max-von-Laue-Strasse 1, 60438 Frankfurt am Main, Germany; Frankfurt Institute for Advanced Studies, Ruth-Moufang-Strasse 1, 60438 Frankfurt am Main, Germany)

qm2022_niklas_goetz.pdf

15:40 Fluctuations of conserved charges in strong magnetic fields

Strong magnetic fields are created at the early stage of non-central heavy-ion collisions. However, whether the magnetic fields survive in the late stage of heavy-ion collisions and experimental measurements of various observables are reminiscent of the initially-created magnetic fields still remain elusive. In this talk we show that fluctuations of and correlations among net baryon number, strangeness and electrical charge can be useful to probe the imprint of the magnetic field in heavy-ion collisions. This is based on the fact that 1) these fluctuations and correlations have been shown to be very useful in understanding the QCD phase structure in the vanishing magnetic fields and 2) our very recent lattice QCD studies on these quantities in magnetic fields.

We will show the first lattice QCD results of the second-order fluctuations of and correlations among net baryon number, electric charge and strangeness in (2+1)-flavor lattice QCD in the presence of a background magnetic field. Lattice QCD simulations are performed on $32^3\times N_\tau$ lattices using the highly improved staggered fermions in a fixed scale approach with $N_\tau\in[8,96]$ [1,2]. We study these quantities from zero temperature up to $\sim$1.7 $T_{pc}$ with 15 values of the magnetic field strength $eB\in[0,60~m_\pi^2]$ with pion mass $m_\pi=$220 MeV [1]. We also extend the above lattice QCD studies to the realistic case with physical pion mass $m_\pi=135$ MeV, and focus on a smaller temperature interval around the pseudo-critical temperature ranging from 0.9 $T_{pc}$ to 1.1 $T_{pc}$. To mimic the magnetic field strength produced in the early stage of heavy-ion collision experiments we now have 6 different values of the magnetic field strength up to $\sim$10$m_\pi^2$ with $m_\pi=135$ MeV [3].

We discuss the temperature and $eB$ dependences of the second-order fluctuations of and correlations among net baryon number, electric charge and strangeness. We find that these second-order fluctuations and correlations are substantially affected by $eB$. They even develop peak structures at sufficiently large $eB$ which could be related to a possible critical end point in the $T-eB$ plane. We propose to investigate these quantities in experiments in different centrality classes and collision systems where $eB$ could be different.

[1] H.-T. Ding, S.-T. Li, Q. Shi and X.-D. Wang, Eur. Phys. J. A 57 (2021) 202.
$~~~~~~~$[2] H.-T. Ding, S.-T. Li, A. Tomiya et al., Phys. Rev. D 104 (2021) 014505.
$~~~~~~~$[3] H.-T. Ding, S.-T. Li, J.-H. Liu and X.-D. Wang, work in progress.

Speaker: Dr Jun-Hong Liu (Central China Normal University)

fluctuations-extB.pdf

16:00 Heavy-flavour production as a function of the event activity with ALICE

Differential studies of heavy-flavour production as a function of the event charged-particle multiplicity provide insights into the role of multi-parton interactions on heavy-quark production, the relevance of color-reconnection mechanisms in heavy-quark hadronization, and the interplay of hard and soft processes in pp, p--Pb, and Pb--Pb collisions. A complementary approach on the above phenomena can be obtained by comparing the production of heavy-flavour particles in jet-like and isotropic events, as well as measuring their production as a function of the underlying event activity, which allows us to reduce possible auto-correlation effects. In addition, measurements of charm baryon-to-meson and strange to non-strange meson yield ratios provide a unique tool to investigate charm hadronization mechanisms and to explore if these mechanisms get modified as a function of the event multiplicity.

A comprehensive collection of new measurements on heavy-flavour particle production versus event activity and their comparison to model predictions will be presented. In particular, self-normalised yields of heavy-flavour particles in pp and p--Pb collisions will be presented. A systematic comparison of the results for the different particle species, and the separation of charm and beauty origins, allow us to shed further light on this topic. New measurements on D-meson production as a function of the event spherocity, as well as of the underlying-event activity, will also be discussed. The most recent developments and the final measurements about the $\Lambda_{\rm c}/{\rm D^0}$ and ${\rm D_{s}^{+}}/{\rm D^0}$ as a function of multiplicity in pp, p--Pb and Pb--Pb collisions will be presented. Final results of heavy-flavour decay muon elliptic-flow coefficient in high-multiplicity p-Pb collisions, and its comparison with models including initial-state effects, will also be discussed.

Speaker: Luigi Dello Stritto (Universita e INFN, Salerno (IT))

ldellost_QM2022.pdf

14:40 → 16:20 Parallel Session T15: Future facilities and new instrumentation: II

Convener: Piotr Salabura (IFUJ)

14:40 Commissioning runs of J-PARC E16 experiment performed in 2020-21

Hadrons are elementary excitations of the QCD vacuum, and their properties reflect the state of the vacuum. The properties of the vacuum are theoretically suggested to be modified at finite density or temperature. Therefore, measuring hadrons under such an environment will lead to understanding of the property of QCD vacuum.
The J-PARC E16 experiment focuses on a measurement of the spectral modifications of vector mesons at nuclear density. In the experiment, 30 GeV primary proton beam is irradiated on carbon and copper targets to produce vector mesons, ${\rho}$, ${\omega}$ and ${\phi}$. We measure the spectra of these mesons at nuclear density from their dilepton decay.
In order to obtain large statistics, we constructed a new spectrometer having high rate capability to detect dileptons produced in pA reaction. The spectrometer consists of Silicon Strip Detectors (SSD), GEM TRackers (GTR) for tracking, and Hadron Blind Detectors (HBD) and Lead Glass calorimeters (LG) for electron identification. GTR is used to cope with the expected high particle rate 5 kHz/${\textrm{mm}^2}$. The spectrometer is designed 5.8 MeV/${c^2}$ mass resolution for ${\phi}$ mesons and 99.97 % pion rejection power.
The experiment has been successfully launched at a J-PARC high momentum beam line in 2020, and three commissioning runs have been carried out so far. The first physics run is planned in 2022-2023. In the physics run, we will obtain 15,000 ${\phi}$ mesons.
Preliminary results of the commissioning runs and the expected physics results will be presented in this talk.

Speaker: Masaya Ichikawa (Kyoto Univ.)

20220407_qm_ichikawa.pdf

15:00 Measuring dilepton and heavy quark production at large $\mu_{\rm B}$; the NA60+ experiment at the CERN SPS

The high-$\mu_{\rm B}$ region of the QCD phase diagram has become the object of several studies, focused on the investigation of the order of the phase transition and the search for the critical point. Accessing rare probes, which include electromagnetic observables and heavy quark production, is experimentally challenging as it requires large integrated luminosities, and a fixed-target environment may represent an ideal solution for these studies. The CERN SPS can cover, with large beam intensity, the collision energy region $5<\sqrt{s_{\rm NN}}<17$ GeV, which was little studied until now with rare observables. A future experiment, NA60+, is being proposed to access this region and perform accurate measurements of the dimuon spectrum from threshold up to the charmonium region, as well as a study of charm and strange hadrons, via their 2- and 3-body hadronic decays. The experiment, which is also part of the Physics Beyond Colliders CERN initiative, includes a muon spectrometer, based on tracking gas detectors (GEM, MWPC) coupled to a vertex spectrometer based on Si detectors (MAPS). The time slot after the Long Shutdown 3 of the LHC ($>$2027) is foreseen for the first data taking, with Pb and proton beams.

In this contribution we will review the project and its recent developments, including the technical aspects and the R&D status, as well as detailed studies of the physics performances for the observables under study.

Speaker: Enrico Scomparin (Universita e INFN Torino (IT))

QM2022_NA60plus_v2.pdf

15:20 Upgrades toward a comprehensive QGP detector at CMS for the high luminosity LHC era

The Compact Muon Solenoid (CMS) detector at the CERN Large Hadron Collider (LHC) will undergo an extensive Phase II upgrade program to prepare for the more challenging conditions of the High-Luminosity LHC (HL-LHC) in the high energy particle and nuclear physics program. A new time-of-flight layer is designed to measure minimum ionizing particles (MIPs) with a time resolution of ${\sim}30$ ps and to provide hermetic coverage up to a pseudorapidity of $|\eta|$=3. This mip timing detector (MTD) will provide excellent particle identification (PID) via TOF in QCD and heavy ion physics for the LHC Run 4 and beyond. Together with the extended coverage of tracking ($|\eta|<4$) and calorimetry ($|\eta|<5$), the MTD will enable a broad range of unique measurements and realize a comprehensive QGP detector for heavy ion physics. Moreover, the measurement of forward neutrons and photons in Zero Degree Calorimeters, or ZDCs, is essential for event classification and triggering. In order to reach the required luminosities, the LHC interaction regions will be completely remodeled, necessitating the need to build new ZDCs that are both thinner and much more radiation hard. This challenge motivated the formation of a joint project between ATLAS and CMS to build new ZDCs for Run 4. After introducing the technology and status of the MTD and ZDC projects, we present the performance of a broad CMS heavy ion physics program with TOF-PID at the HL-LHC, including heavy flavor dynamics in (3+1)D, QGP medium response to high-$p_\mathrm{T}$ parton energy loss at wide jet cone angles, collectivity in small systems, fluctuations and transport of initially conserved charges, and light nuclei physics.

Speaker: Andre Govinda Stahl Leiton (CERN)

QuarkMatter2022_talk_v2.pdf

15:40 ALICE upgrades and preparations for physics in Run 3

ALICE has undergone a major upgrade in preparation of LHC Run 3 (2022-2025). All detectors have been upgraded to allow readout at higher rates, matching the interaction rates provided by the LHC. The Inner Tracking System now completely consists of Monolithic Active Pixel Sensors, which also improves pointing resolution. The Time Projection Chamber has been equipped with GEM-based readout chambers to allow the operation with Pb-Pb collision rates of ~50 kHz. The muon system has also been upgraded and extended by the Muon Forward Tracker. New trigger detectors were installed to allow the clean identification of interactions. All detectors have seen upgrades of the readout chain to make use of the increased luminosity expected from the LHC. Furthermore, the computing infrastructure and software stack have been redesigned for continuous read-out and including a synchronous reconstruction stage making use of 2000 GPUs to achieve the required computing performance. An asynchronous reconstruction stage after data taking provides an improved reconstruction by taking into account calibration results. The reconstructed data are stored on grid sites for analysis through an improved system of analysis trains. In this presentation, we will report on the installation of the detectors and the computing farm, their commissioning with and without beam, as well as first results with pp collision.

Speaker: Anton Alkin (CERN)

QM22-Alkin-Upgrade-v3-fix.pdf

16:00 Future ALICE upgrades for Run 4 and beyond

ALICE pursues several upgrades to further extend the physics reach. For Run 4, ALICE is pioneering the usage of bent, wafer-scale pixel sensors to replace the three innermost layers of the inner tracking system. This makes it possible to construct truly cylindrical layers, which consist practically only of the silicon sensors. The resulting improvement in pointing resolution will allow better measurements of heavy-flavour hadrons and dielectrons. In addition, a Forward Calorimeter (FoCal) is proposed to provide unique constraints on the low-x gluon structure of protons and nuclei via forward measurements of direct photons. The FoCal combines a high-resolution electromagnetic Si-W calorimeter with a conventional hadronic calorimeter. For Run 5 and beyond, ALICE 3 is proposed, using a novel detector concept to gain unique access to heavy flavour probes of the QGP and the approach to thermalisation as well as real and virtual photons. At its core, it combines a high-resolution vertex detector with a large-acceptance silicon pixel tracker. For the identification of particles, a combination of a time-of-flight system, a Ring-Imaging Cherenkov detector, an electromagnetic calorimeter, a muon identifier, and a dedicated forward detector for ultra-soft photons, are being studied. In this presentation, we will discuss the upgrade plans, report on R&D results for ITS3 and FoCal, and present the requirements and concepts for ALICE 3.

Speaker: Horst Sebastian Scheid (Goethe University Frankfurt (DE))

qm2022_scheid_final.pdf

16:20 → 16:50 Coffee break

16:50 → 19:10 Parallel Session T04: Jets, high-pT hadrons, and medium response: IV

Convener: Boris Tomasik (Univerzita Mateja Bela (SK))

16:50 New results on the parton mass and color-charge dependence of jet quenching with ATLAS

The suppression of jets in heavy-ion collisions provides a powerful method to probe the dynamics of the hot, dense plasma formed in these collisions at the LHC.
Jet quenching in heavy-ion collisions is expected to depend on the mass of the fragmenting parton as well as its QCD color charge.
For light quarks and gluons, energy loss via gluon bremsstrahlung, which is sensitive to the QCD color factor, is expected to dominate. In the case of heavy-quark-initiated jets, the radiative energy loss is expected to be suppressed by the dead cone effect and collisional energy loss may play a more important role.
In this talk, we report two new measurements by the ATLAS detector at the LHC in 5.02 TeV Pb+Pb collisions. First, we present a measurement of photon-tagged jets which exploits the known difference in the fraction of quark-/gluon-initiated jets with and without the photon tag. Second, we present a measurement of $b$-tagged jets, identified through the semileptonic decays of $B$-hadrons into muons.
The RAA values for photon-tagged jets and b-jets are compared to those for inclusive jets, allowing for the extraction of the color charge and mass dependence of parton energy loss. The results are compared to a variety of theoretical calculations.

Speaker: Sebastian Tapia Araya (Illinois at Urbana)

MassAndColor_QM2022_stapia_V4.pdf

17:10 Medium-enhanced $c\bar{c}$ radiation

We show that the same QCD formalism that accounts for the suppression of high-$p_T$ hadron spectra in heavy-ion collisions predicts a medium-enhanced $c\bar{c}$ pair production in high-$p_T$ jets.

Speaker: Gian Michele Innocenti (CERN)

GMInnocenti_ccbarsplitting_finalv5.pdf

17:30 Combined constraining power of jet and hadron quenching on the jet transport parameter

We found that collisional and radiative processes affect hadron and jet $R_{AA}$ with different $p_T$ dependence. It is then interesting to analyze the combined constraining power from both jet and hadron quenching to the jet transport parameter $\hat{q}$.

We conduct the study with the improved transport model (LIDO), including elastic and radiative processes, and a simple treatment of jet-medium response. The model only applies in the ''transport regime'': hard partons with virtuality less than a characteristic momentum broadening scale $Q^2_{\rm med} \approx \langle \Delta k_t^2\rangle$ in a medium with temperature greater than $T_f \approx T_c$. $\hat{q}$ is determined by a temperature dependent jet-medium coupling $g_s(\mu \pi T)$.

We used a Bayesian analysis to determine the temperature and momentum dependence using hadron (light and heavy) and $R=0.4$ jet $R_{AA}$ at RHIC and LHC for the first time [1]. Experimental uncertainty and ambiguity from $\mu$, $Q_{\rm med}$ and $T_f$ are propagated to the final $\hat{q}$. Then, we made predictions with quantified uncertainty to the jet-cone-sized dependence of $R_{AA}$, modified jet shape, and fragmentation functions.

[1] Weiyao Ke and Xin-Nian Wang JHEP 05 (2021) 041

Speaker: Weiyao Ke (Los Alamos National Laboratory)

QM22-WK-Apr7.pdf

17:50 Are jets narrowed or broadened in medium?

We compute the in-medium jet broadening $\langle p_\perp^2\rangle$ to leading order in energy in the opacity expansion. At leading order in $\alpha_s$ the elastic energy loss gives a jet broadening that grows with $\ln E$. The next-to-leading order in $\alpha_s$ result is a jet narrowing, due to destructive LPM interference effects, that grows with $\ln^2 E$. We find that in the opacity expansion the jet broadening asymptotics are---unlike for the mean energy loss---extremely sensitive to the correct treatment of the finite kinematics of the problem; integrating over all emitted gluon transverse momenta leads to a prediction of jet broadening rather than narrowing. We compare the asymptotics from the opacity expansion to a recent twist-4 derivation of $\langle p_\perp^2\rangle$ and find a qualitative disagreement: the twist-4 derivation predicts a jet broadening while the opacity expansion method predicts a narrowing. Comparison with current jet measurements cannot distinguish between the broadening or narrowing predictions. We comment on the origin of the difference between the opacity expansion and twist-4 results.

Speaker: William Horowitz (University of Cape Town)

220407(QM)Horowitz.pptx

18:10 Measurements of the R-dependence of inclusive jet suppression and groomed jet splittings in heavy-ion collisions with ALICE

Jets in relativistic heavy-ion collisions interact with the quark-gluon plasma (QGP), leading to effects such as a suppression of jet yields and modification of internal jet structure that are used to measure the properties of the QGP. This talk will show the inclusive jet nuclear modification factors in Pb--Pb collisions in various centrality classes at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV recorded with the ALICE detector for resolution parameters up to R = 0.6 for momenta down to 40 GeV/c. This achieved by utilizing machine learning techniques to correct the large background in heavy-ion collisions allowing to extend the measurement of inclusive jets to lower jet $p_{\mathrm{T}}$ and R than previously achieved in heavy-ion collisions at the LHC. We also present a new suite of measurements characterizing groomed jet splittings using both the Soft Drop and Dynamical Grooming algorithms in central and semi-central Pb--Pb collisions. We report the groomed jet radius, $\theta_g \equiv R_g/R$, the groomed jet momentum fraction, $z_g$, and the transverse momentum of the groomed splitting, $k_{\mathrm{T,g}}$. These measurements are enabled by the high-precision tracking system of ALICE, and reveal the full kinematics of the hardest jet splitting. All measurements are fully corrected through unfolding and compared to a plethora of theoretical calculations.

Speaker: Hannah Bossi (Yale University (US))

HBossi_QuarkMatter_2022.pdf

18:30 Jet acoplanarity and energy flow within jets in Pb-Pb and pp collisions with ALICE

Jets are excellent probes for the study of the deconfined matter formed in heavy ion collisions. We present measurements of the semi-inclusive distribution of charged-particle jets recoiling from a high-pT trigger hadron in pp and central Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV. We compare the semi-inclusive recoil jet yields in pp and Pb-Pb collisions over a broad $p_\mathrm{T}$ jet range, which probes energy loss due to jet quenching. We report the first measurement of hadron-jet acoplanarity in pp collisions. The comparison of acoplanarity measurements in pp and Pb-Pb collisions at low $p_\mathrm{T}$ jet gives unique and incisive exploration of medium-induced jet deflection. The measurements are compared to theoretical calculations based on pQCD, and to models incorporating jet quenching.
The jet substructure measurements can also help us understand the interaction dynamics of high-energy partons with the quark-gluon plasma. We present two new infrared and collinear safe observables: the angle between different definitions of the jet axis, $\Delta R_{\rm axis}$, as well as jet energy flow measurements using jets reconstructed with different resolution parameters R. Both the jet energy flow and $\Delta R_{\rm axis}$ measurements can help us gauge the comparative strength of competing energy loss mechanisms in a heavy ion environment. The first measurement of the $\Delta R_{\rm axis}$ observable, both in pp and Pb-Pb, are presented and discussed in the context of event generators and analytic calculations. A new measurement of jet energy flow in pp collision data is compared to prediction of various pp event generators. A study of the sensitivity of this observable to energy loss effects in Pb-Pb collisions with the JEWEL event generator will also be presented.

Speaker: Reynier Cruz Torres (Lawrence Berkeley National Lab. (US))

220407_QM22_v3_upload.pdf

18:50 Exploring jet modification via $\gamma$-hadron and $\pi^{0}$-hadron correlations in Au+Au collisions at PHENIX

PHENIX has quantified the modification of jets in heavy-ion collisions due to partonic energy loss in the quark gluon plasma (QGP) by measuring the distribution of hadrons relative to a trigger particle, such as a high momentum photon or $\pi^{0}$. These two-particle correlations have revealed that high momentum hadrons are suppressed, while yield of low momentum hadrons is enhanced. This enhancement is most pronounced at relatively large angles away from the opposing jet axis. More recent analyses have further investigated and quantified this phenomena by studying the yield modification as a function of the azimuthal angle ($I_{AA}$ vs $\Delta\phi$). The larger data sets collected by PHENIX in 2014 and 2016 enhance the statistical precision and enable more differential measurements, which provide insight to how the jets substructure is modified by the QGP and crucial constraints on models of partonic energy loss and medium response. This talk will report the latest analyses of $\pi^{0}$-hadron and $\gamma$-hadron correlations in Au+Au collisions measured by PHENIX, and discuss how these results impact our understanding of jet modification and partonic energy loss in the QGP and the medium response to jets.

Speaker: Megan Connors

Connors_QM2022v3.pdf

16:50 → 19:10 Parallel Session T13: Electroweak probes: II

Convener: Itzhak Tserruya (Weizmann Institute of Science (IL))

16:50 Probing the valence quark region of nucleons with $Z$ bosons at LHCb

The unique forward coverage of the LHCb spectrometer allows the valence quark distributions of protons and nuclei to be probed with unprecedented precision. In this high-$x$ region, both the flavor content and structure of the nucleon's parton distribution functions remain relatively poorly known. New LHCb measurements of $Z$+charm jet production could be indicative of a valence-like intrinsic-charm component in the proton wavefunction, and measurements of $Z$ production in $p$Pb collisions provide new constraints on the partonic structure of nucleons bound inside nuclei. Here we will discuss these new LHCb measurements and comparisons with state-of-the-art parton distribution function calculations.

Speaker: Tianqi Li (South China Normal University (CN))

QM2022_tianqi_v3.pdf

17:10 Electroweak-boson production from small to large collision systems with ALICE at the LHC

Electroweak W and Z bosons created in hard-scattering processes at the early stage of the collisions are efficient probes of the initial state of the collisions. While the measurements of W and Z bosons in p–Pb and Pb–Pb collisions provide insights on the nuclear modification of the parton distribution functions, the results in pp collisions are a stringent test of perturbative QCD-based calculations and production mechanisms. In pp collisions, W bosons can be produced by pair annihilation but also by higher order processes with additional hadron production. An investigation of these bosons, in relation to the hadrons in the rest of the event, can give insight into multi-parton interactions in high-multiplicity events and the role of color-reconnection mechanisms.
Electroweak bosons are studied with ALICE in pp collisions at $\sqrt{s}$ = 13 TeV, p–Pb collisions at $\sqrt{s_{\rm NN}}$ = 8.16 TeV and Pb–Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV via their leptonic decays in the muon and electron channels at forward rapidity (−4 < $\eta$ < −2.5) and midrapidity (|$\eta$| < 0.8), respectively. The observations in p–Pb and Pb–Pb collisions at forward rapidity give access to low Bjorken-x values, a phase-space region poorly constrain by heavy-ion experiments.
A review of the most recent results on the production of W$^+$, W$^−$ and Z bosons is presented. The results include differential measurements of the normalised production yields, production cross sections and nuclear modification factors as a function of rapidity, transverse momentum, collision centrality and charged-particle multiplicity. The lepton-charge asymmetry measurement is also reported. A particular emphasis will be placed on the new measurement of the production of W bosons in association with hadrons as a function of the charged-particle multiplicity in pp collisions. Comparisons with theoretical model calculations, providing insights on production mechanisms and new constraints for the determination of the nuclear parton distributions functions will also be discussed.

Speaker: Shingo Sakai (University of Tsukuba (JP))

QM_WZ_ssakai.pdf

17:30 Electroweak probes as tools for understanding initial state effects in heavy ion collisions with the CMS detector

Z bosons and the Drell-Yan process are considered as essential probes to study the initial state effects in nuclear collisions. The CMS experiment has measured differential cross sections of Z bosons decaying to pairs of leptons in lead-lead collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The second order Fourier coefficient of the azimuthal distribution of Z bosons are measured to be compatible with zero, showing that Z bosons do not experience significant final-state interactions. Yields of Z bosons are compared to Glauber model predictions and are found to deviate from these expectations in peripheral collisions, indicating the presence of initial collision geometry and centrality selection effects. The precision of the measurement allows, for the first time, for a data-driven determination of the nucleon-nucleon integrated luminosity as a function of lead-lead centrality, thereby eliminating the need for its estimation based on a Glauber model. The results of the Drell-Yan process are also reported in pPb collisions at center-of-mass energy of 8.16 TeV. The differential cross sections are presented in a wide dimuon mass range down to 15 GeV/$c^{2}$. In addition, the forward-backward asymmetries are presented, providing useful information to probe the presence of nuclear effects. All results are compared to CT14, EPPS16, and nCTEQ15WZ (n)PDFs, to better understand the nuclear PDF and the sensitivity of the detailed models.

Speaker: Austin Alan Baty (Rice University (US))

Baty_QM2022_CMS_EWKProbes_v5.pdf

17:50 Low $p_T$ direct photon production at RHIC measured with PHENIX

PHENIX has used the versatility of RHIC to map out low $p_T$ direct photon production as function of collision system size and beam energy. For systems with a size corresponding to a $dN_{ch}/d\eta$ larger than 20-30, we observe a large yield of direct photons, a large azimuthal anisoptropy with respect to the reaction plane, and a characteristic centrality dependence of $dN_\gamma/dy \propto (dN_{ch}/dy)^\alpha$, with $\alpha \sim 1.2$.
In this talk, we will present new results from Au+Au and Cu+Au collisions at $\sqrt{s_{NN}}$ = 200~GeV. After subtracting the prompt photon component, the inverse slope for the $p_T$ range from 1-2~GeV/c is 250~MeV, but increases to about 400~MeV for the range from 2 to 4~GeV/c. Within the experimental uncertainty, there is no indication of a system size dependence of the inverse slope. Furthermore, the system size dependence of the yield, expressed through the power $\alpha$, remains independent of $p_T$ over the entire observed range from 1 to 6~GeV/c. Like the large yield and azimuthal anisotropy, these features, while qualitative consistent with the emission of thermal photons from the quark gluon plasma, elude a quantitative description through theoretical model calculations.

Speaker: Roli Esha (Center for Frontiers in Nuclear Science, Stony Brook University)

Esha_DirectPhoton_PHENIX.pdf

18:10 Jet-medium photons as a probe of early time dynamics and parton energy loss mechanisms

Heavy ion collision experiments at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC) have resulted in the creation of an exotic state of matter: the quark-gluon plasma (QGP). Over the past two decades, our understanding of the QGP has evolved significantly, from measurements of nuclear modification functions of jets due to energy loss in medium to the realization of the applicability of hydrodynamics in matching the soft particle spectra. Direct photons exclude those from hadronic decays, and have proven themselves as versatile probes of the QGP. They are emitted at all stages of the evolution and can be soft but penetrating probes of the medium due to their electromagnetic nature and lack of final state interactions [1]. An important channel of photon production in jet-medium interactions is the conversion process, where a high energy quark or anti-quark is converted to a photon via a soft exchange with the medium [2]. In this talk, we present a new and modern calculation of direct photons created by the interaction of hard partons with the viscous relativistic fluid-dynamical medium. We calculate the conversion photon contribution to the total photon spectrum as well as to the photon $v_2$. We find that in the mini-jet domain of transverse momenta ($4 − 10$ GeV), jet- medium photons can contribute as much as 20% of the total photon yield with a significant portion coming from the conversion mechanism. We also explore the potential of conversion photons as a probe of different energy loss approaches. We perform this comparison using the conversion photon spectrum from the evolving parton distributions computed with the AMY-McGill[3] and CUJET[4,5] parton energy loss formalisms.
[1] C. Gale et al., arXiv: 2106.11216
[2] G.-Y. Qin et al., Phys. Rev. C 80 (2009) 054909
[3] B. Schenke et al., Phys.Rev.C 79 (2009) 054908
[4] M. Gyulasy et al., Nucl.Phys.B 571 (2000) 197-233
[5] S. Shi et al. Chin.Phys.C 43 (2019) 4, 044101

Speaker: Mr Rouzbeh Modarresi-Yazdi (McGill University)

Quark_Matter_2022_RMY.pdf

18:30 Photon production in high-energy heavy-ion collisions: thermal photons and radiative recombination

Electromagnetic probes are one of promising tools to investigate properties of the hot and dense matter created in high-energy heavy-ion collisions. However, even the state-of-the-art phenomenological models which can correctly explain spectra and anisotropic flows of charged hadrons underpredict yield and elliptic flow of photons [1]. It is known as “photon puzzle”.

Here, we propose photon emission at hadronization as a possible resolution to the photon puzzle [2].
First, we calculate yields and collective flows of thermal photons at RHIC and the LHC, using a relativistic viscous hydrodynamical model which is combined with a hadron-based event generator, UrQMD [3]. Initial conditions are given by TRENTO. Our calculated yields and elliptic flows of thermal photons are smaller than those of experimental data at RHIC and the LHC, which is consistent with the previous study [1].

Then, we discuss the effect of radiative hadronization on thermal photons from fluid. We find that radiative hadronization enhances both direct photon yields and elliptic flows as the same time and reproduces experimental data at RHIC and the LHC. The ratio of yield of pions produced through the radiative hadronization to that from the original recombination model at RHIC is 20 %. It means that the radiative recombination does not break the nature of quark number scaling in elliptic flow which is expected from the original recombination model [4]. On the other hand, in spite of the small contribution in hadron production, the radiative recombination process increases both the yield and collective flows of direct photon. The ratio at the LHC is 5 % which is smaller than that at RHIC. We show the detailed analyses on photon production during space-time evolution of fluid and at hadronization in high-energy heavy-ion collisions.

[1] J. F. Paquet, C. Shen, G. S. Denicol, M. Luzum, B. Schenke, S. Jeon and C. Gale, Phys. Rev. C 93 (2016) no.4, 044906.
[2] H. Fujii, K. Itakura and C. Nonaka,　Nucl. Phys. A967 (2017), 704-707.
[3] K. Okamoto and C. Nonaka, Phys. Rev. C98 (2018) no.5, 054906.
[4] R. J. Fries, B. Muller, C. Nonaka and S. A. Bass, Phys. Rev. Lett. 90 (2003), 202303.

Speaker: Chiho Nonaka

QM2022_nonaka.pdf

18:50 Virtual Photon Measurements with the HADES at GSI

The High Acceptance DiElectron Spectrometer (HADES) is dedicated to the measurement of electromagnetic probes from heavy ion collisions and to study the in-medium behaviour of dileptons in the moderate temperature and high density regime of the QCD phase diagram. This region recently gained more attention as conditions turn out to be similar as in neutron-star mergers. Dileptons as penetrating probes are messengers of this dense medium and can reveal the thermal properties and the lifetime of the medium but also give insight into meson properties at high densities.
In this talk we present preliminary results of HADES on the dielectron analysis of 4.5 billion Ag+Ag collisions ($0-40\%$ centrality) at a centre-of-mass energy of $\sqrt{s_{NN}} = 2.55 \, GeV$. The upgraded RICH detector offers excellent electron identification and suppression of conversion-pairs resulting in a signal-to-background ratio larger than 1 for $M_{e^+e^-}>500 MeV/c^2$. The high statistics data sample in combination with a strongly increased electron detection effciency and background suppression allow for a differential analysis in terms of centrality or electron-pair-momentum with a signal up to the phi meson mass region. For higher pair-momenta a signal of the omega meson is clearly seen while vanishing for lower pair-momenta. The temperature extracted from the intermediate mass region compares well with the HADES measurement in Au+Au collisions at $\sqrt{s_{NN}} = 2.42 \, GeV$. The obtained dielectron signal spectrum is compared to simulated hadronic cocktail and nucleon-nucleon reference spectra revealing a strong in-medium contribution.

Speaker: Jan-Hendrik Otto

QM_2022_Jan_Otto.pdf

16:50 → 19:10 Parallel Session T14: Hadron production and collective dynamics: II

Convener: Radoslaw Ryblewski (Institute of Nuclear Physics PAN)

16:50 Search for collective effects in small systems obtained in ep collisions at HERA

Measurements of two- and multi-particle angular correlations are presented in both $ep$ deep-inelastic scattering at $\sqrt{s}=319$ GeV and in photoproduction off protons at energies $W_{\gamma p}=270$ GeV, as a function of charged-particle multiplicity. No long-range ridge structure is observed in the correlation functions. The second-order ($V_{2∆}$) and third-order ($V_{3∆}$) azimuthal anisotropy Fourier harmonics are extracted. Further, $C_2\{4\}$ signals are extracted from four-particle correlations for the first time in $ep$ collisions and are found to be positive or consistent with 0. In summary, collective behavior has not been observed in collisions of protons with virtual or quasi-real photons at HERA energies.

H1prelim-20-033

Speaker: Chuan Sun (Stony Brook University)

20220407 - QM2022 - ChuanSun.pdf

17:10 Nuclear modification of hard scattering processes in small systems at PHENIX

Collisions of small systems at RHIC exhibit a significant suppression of the nuclear modification factor $R_{xA}$ of jets and high momentum neutral pions in events with large event activity. This suppression is accompanied by an enhancement of $R_{xA}$ in events with low event activity. Since event activity is commonly interpreted as a measure of the centrality of the collisions, these results call into question any interpretation of the suppression in central collisions that invokes energy loss in a QGP produced small systems. In this talk, we will compare prompt photon to $\pi^0$ production measured by PHENIX in $d$+Au collision at $\sqrt{s_{NN}} = 200$ GeV to demonstrate that the apparent centrality dependence is not related to a nuclear modification of hard scattering processes, but likely due to deviations from the proportionality of event activity and centrality in the underlying standard Glauber model calculations. Furthermore, we will use prompt photon production in $d$+Au relative to $p+p$ collisions to empirically determine the effective number of binary collisions $N_{coll}$ of a given event sample. We find that for all event selections, except for those with the highest event activity, $R_{xA}$ of $\pi^0$ is consistent with unity. By comparing $p$+Au and $d$+Au collisions, we will investigate the significance of the remaining suppression of high $p_T$ $\pi^0$ production in events with high event activity.

Speaker: Niveditha Ramasubramanian (Stony Brook University)

QuarkMatter2022_dAu-HighpTDP.pdf

17:30 Investigation of in-medium effects of charmonia using azimuthal anisotropy and jet fragmentation function in PbPb collisions at 5.02 TeV with the CMS experiment

To understand the in-medium effects of quarkonia in heavy ion collisions, it is necessary to perform differential studies of various observables to have a global picture of the quarkonium dynamics in the quark-gluon plasma (QGP). Recent results in proton-proton collisions have suggested that J/$\psi$ mesons are produced with much more jet activity than model predictions, which indicate that the amount of isolated J/$\psi$ mesons with respect to the total production cross section plays an important role in interactions between charmonia and the QGP medium. In this presentation, we present the second-order and third-order Fourier coefficients, $v_{2}$ and $v_{3}$ for prompt and nonprompt J/$\psi$, and prompt $\psi(2S)$ mesons, with reporting the $v_{2}$ and $v_{3}$ for prompt $\psi(2S)$ mesons for the first time in heavy ion collisions. The results are discussed with theoretical calculations and discussed in terms of suppression and recombination effects. Also, we show the final results of the measurement of J/$\psi$-jets in pp and PbPb collisions. The jet fragmentation function of jets containing a J/$\psi$ meson is studied to probe the dependence of quenching effects on the degree of associated hadro-production inside the jet.

Speaker: Geonhee Oh (University of Illinois at Chicago (US))

Geonhee_CharmoniaFlowCMS_QM22.pdf

17:50 ALICE search for the collective origin of strangeness enhancement

One of the key challenges of hadron physics today is understanding the origin of strangeness enhancement in high-energy hadronic collisions, i.e. the increase of (multi)strange hadron yields relative to non-strange hadron yields with increasing charged-particle multiplicity. In particular, what remains unclear is the relative contribution to this phenomenon from hard and soft QCD processes and the role of initial-state effects such as effective energy. The latter is the difference between the total centre-of-mass energy and the energy of leading baryons emitted at forward/backward rapidities. The superior tracking and particle-identification capabilities of ALICE make this detector unique in measuring (multi)strange hadrons via the reconstruction of their weak decays over a wide momentum range. The effective energy is measured using zero-degree hadronic calorimeters (ZDC).

In this talk, recent results on $K_s^0$ and Ξ production in- and out-of-jets in pp collisions at $\sqrt s $ = 13 TeV using the two-particle correlation method are presented. To address the role of initial and final state effects, a double differential measurement of (multi)strange hadron production as a function of multiplicity and effective energy is also presented. The results of these measurements are compared to expectations from state-of-the-art phenomenological models implemented in commonly-used Monte Carlo event generators.

Speaker: Chiara De Martin (Universita e INFN Trieste (IT))

QM2022_ChiaraDeMartin.pdf

18:10 Probing initial and final state effects of heavy-ion collisions with STAR experiment

Understanding the initial conditions, the transport properties, and the dynamical evolution of the quark-gluon plasma are central objectives of the heavy-ion program at RHIC. The transverse momentum correlator $G_{2}\left(\Delta\eta,\Delta\varphi\right)$ has been shown to be sensitive to the shear viscosity $\eta/s$~[1,2]. On the other hand, the $\rho(v^{2}_{2},\langle p_{T} \rangle)$ correlator indicates more sensitivity to the initial-state than to final-state effects~[3,4]. A comprehensive set of $G_{2}\left(\Delta\eta,\Delta\varphi\right)$ and $\rho(v^{2}_{2},\langle p_{T} \rangle)$ measurements for Au+Au collisions spanning the beam energy range $\sqrt{s_{\rm NN}}$ = 11.5-200 GeV will be presented for several centralities and event shape selections. Furthermore, we also explore the initial-state effects in longitudinal directions using the de-correlation observables which measure the factorization ratio for flow harmonics, $r_{n}(\eta)(n = 2,3)$ and $R_{2}(\eta)$. The new results from isobar collisions as well as BES II energy Au+Au collisions will provide important insights on the 3D modeling of initial-state of heavy-ion collisions, especially its collision energy and collision size dependence. These results are also compared to LHC measurements and theoretical model calculations~[2,4] to provide constraints on initial-state fluctuations and $\eta/s(\mu_{B},T)$.

[1]~S. Gavin and M. Abdel-Aziz, Phys. Rev. Lett. 97, 162302 (2006)

[2]~N. Magdy et al., arXiv:2111.07406

[3]~P. Bozek, Phys. Rev. C 93, 044908 (2016).

[4]~N. Magdy et al., Phys. Lett. B 821 (2021) 136625

Speaker: Gaoguo Yan

QM2022_Gaoguo.pdf

18:30 Latest results on resonance production from small to large systems with ALICE

Short-lived hadronic resonances are key tools to study the hadron-gas phase that characterizes the late-stage evolution of high-energy nuclear collisions. Regeneration and rescattering processes occurring in the hadron gas can be studied by measuring the yields of hadronic resonances and comparing them with model predictions with and without the simulation of hadronic interactions. Modification of the yields of hadronic resonances is also observed in pp and p-Pb collisions suggesting the possibility of a short-lived hadronic phase also in small collision systems.
In this talk, new results on Σ(1385) and Ξ(1820) production measured in pp collisions at 13 TeV with ALICE are presented. These results, which extend to higher mass the study of baryonic resonances measured at the LHC, complement existing measurements on resonance production in pp, p–Pb, Xe– Xe, and Pb–Pb collisions at various centre-of-mass energies. Moreover, new preliminary results on double-phi production yields in measured pp collisions at 7 TeV will be shown. The obtained results are compared to lower energy measurements and model calculations where available.

Speaker: Bong-Hwi Lim (Pusan National University (KR))

ALICE_Resonance_QM2022-BHLIM.pdf

18:50 Relativistic fluid dynamics of multiple conserved charges

The strongly interacting matter created in high-energy heavy-ion collisions contains a multitude of conserved quantum charges, like the baryon number, strangeness, and electric charge. These conserved charges and their currents are generally coupled to each other, e.g. a baryon diffusion current also implies a current in electric charge.
In this talk, we present a novel derivation of second-order relativistic dissipative fluid dynamics from the Boltzmann equation for multicomponent reactive mixtures with $N_{\text{spec}}$ particle species and with $N_q$ conserved charges. In the single-fluid approximation there are $4+N_q$ conservation laws for multiple conserved quantum charges and for the total energy-momentum. The second-order equations of motion are derived in the $10+4N_q$-moment approximation for the dissipative quantities to provide closure to the conservation equations. This derivation also delivers explicit expressions for the transport coefficients of the theory. The resulting transport coefficients, such as bulk viscosity, multiple charge-diffusion and shear-viscosity coefficients are also calculated in the ultrarelativsitic limit. We will show and discuss the coupled-charge transport, the resulting separation of charge, and the implied baryon-electric or baryon-strangeness correlations in heavy-ion collisions, and argue that such effects may be relevant for programs at the future FAIR and NICA facilities, or for the discussion of the recent isobar run at RHIC.

Speaker: Mr Jan Fotakis (University of Frankfurt)

fotakis_QM22.pdf

16:50 → 19:10 Parallel Session T16: Light nuclei production

Convener: Yuriy Sinyukov (Bogolyubov Institute for Theoretical Physics)

16:50 Production of Strange Mesons, Hyperons and Hypernuclei in Ag+Ag Collisions at √sNN = 2.55 GeV measured with HADES

In the scope of the FAIR Phase-0 physics program, the HADES collaboration recorded 13.7 billion Ag(1.58A GeV)+Ag events in March 2019. With an available energy of 2.55 GeV in binary nucleon nucleon collisions, the lightest hadrons containing strangeness are produced at their free nucleon nucleon threshold energy. Therefore, they are ideal probes to investigate medium effects due to their steep excitation function.

In this contribution we present preliminary results on the production of Λ hyperons and K⁰_S mesons which are identified based on their weak decay topologies with the help of an artificial neural network (ANN). Both particles are analyzed multi-differentially as a function of transverse momentum, rapidity and centrality. Furthermore, we present the reconstruction of the ³_ΛH which is the lightest known hypernucleus via its weak ³He + π^– decay channel. This constitutes the first successful measurement of hypernuclei at mid-rapidity in heavy-ion collisions at such low beam energies. We contribute to resolving the ³_ΛH lifetime puzzle by performing a ³_ΛH lifetime measurement. Finally, we explore our capabilities of measuring multi-strange hyperons which are produced far below their free nucleon nucleon threshold energy. All presented results are discussed with respect to our findings in Au+Au collisions at √s_NN = 2.42 GeV and the available world data.

Speaker: Simon Spies (Johann-Wolfgang-Goethe Univ. (DE))

SimonSpies_HADESHypernuclei.pdf

17:10 Properties and production of hypernuclei in relativistic ion reactions

The study of hypernuclei and their production mechanisms open new opportunities for nuclear/particle physics and astrophysics. The hyperons influence many nuclear properties in finite nuclei and in neutron stars (infinite nuclear matter). We review the main processes leading to the production of hypernuclei in nuclear reactions including relativistic ion collisions. Such deep-inelastic high-energy interactions do lead to fragmentation and multifragmentation of nuclear matter, and hyper-fragments can be abundantly produced [1,2]. The binding energies of hyperons influence the hypernuclei formation [3,4] and this gives a chance to evaluate experimentally the hyperon effects in nuclear matter. The promising process for such a hypernuclear research is a disintegration of large excited hyper-nuclear residues produced in peripheral relativistic nucleus-nucleus collisions. In central collisions, there is another mechanism responsible for combining hyperons and other baryons into light clusters [5]: The primary nuclear clusters can be formed at the subnuclear densities from the dynamically produced baryons. These clusters are excited and their subsequent decay is able to explain all phenomena of the fragment production observed in central heavy-ion collisions. Our approach is able to describe the FOPI experimental data, in particular, nuclei yields, nuclei kinetic energies, and the modification of the nuclear isotope yields with increasing the beam energy. Previously, it was not reachable with other models. Also our mechanism can lead to the correlations of the produced nuclear species and to unstable hypernuclear states. We use the transport, coalescence and statistical models to describe the whole process, and demonstrate the important regularities of the hypernuclei formation and the advantages of such reactions over the traditional hypernuclear methods: A broad distribution of predicted hypernuclei in masses and isospin allows for investigating properties of exotic hypernuclei. We point at the abundant production of multi-strange nuclei that will give an access to multi-hyperon systems and strange nuclear matter. The realistic estimates of hypernuclei yields in various collisions are presented.

[1] A.S. Botvina, et al., Phys. Rev. C95, 014902 (2017).
[2] A.S. Botvina, et al., Phys. Rev. C94, 054615 (2016).
[3] N. Buyukcizmeci, et al., Phys. Rev. C98, 064603 (2018).
[4] N. Buyukcizmeci, et al., Eur. Phys. J. A56, 210 (2020).
[5] A.S. Botvina, et al., Phys. Rev. C103, 064602 (2021).

Speaker: Dr Alexander Botvina (Univ. Frankfurt)

qm2022-botvina-web.pdf

17:30 The dark side of ALICE: from antinuclei interactions to dark matter searches in space

Space: the final frontier for antinuclei physics. There, antinucleosynthesis models already tested on the bench of hadronic colliders and particle physics experiments are put at work to crack one of the biggest problems of modern physics: the existence and nature of dark matter.

In fact, the observation of an antinucleus in cosmic rays would most probably mean a breakthrough in searches for dark matter. However, to correctly interpret future results, the precise knowledge of both the antinuclei production mechanism and their nuclear inelastic cross sections is needed.
The ALICE collaboration already investigated in detail the anti nucleosynthesis models in small and large colliding systems at the LHC and has recently performed several measurements of antideuteron, $^3\overline{\text{H}}$ and $^3\overline{\text{He}}$ inelastic cross sections, providing the first experimental information of this kind.

In this talk, the final results on antideuteron and $^3\overline{\text{He}}$ inelastic cross-section and the new results on $^3\overline{\text{H}}$ inelastic cross sections are discussed as well how, thanks to them, it is possible to determine for the first time the transparency of the Galaxy to antinuclei stemming from dark matter and Standard Model collisions.

Speaker: Stephan Alexander Konigstorfer (Technische Universitaet Muenchen (DE))

QM2022_Antinuclei_Koenigstorfer.pdf

17:50 Production of Light Nuclei in Au+Au Collisions at $\sqrt{s_{\mathrm{NN}}}$ = 3, 14.6, 19.6 GeV and in Ru+Ru and Zr+Zr Collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV measured by RHIC-STAR

Light nuclei production is predicted to be sensitive to local baryon density fluctuations and can be used to probe the QCD phase structure and the properties of medium created in heavy-ion collisions. Since 2018, the STAR experiment has collected high statistics data in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 3 GeV (BES-II fixed-target mode), 14.6, 19.6 GeV (BES-II collider mode) and isobaric collisions (Ru+Ru and Zr+Zr) at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV. Those datasets allow us to access the QCD phase structure over a broad range of baryon density ($\mu_{B} : 20 \sim$ 750 MeV).

In this talk, we will present the first measurement of centrality, transverse momentum, and rapidity dependences of proton ($p$), deuteron ($d$), triton ($t$), $^{3}\mathrm{He}$, and $^{4}\mathrm{He}$ production in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 3 GeV, $p$, $d$, $^{3}\mathrm{He}$ at $\sqrt{s_{\mathrm{NN}}}$ = 14.6, 19.6 GeV, and $p$, $d$, $t$, $^{3}\mathrm{He}$ in Ru+Ru and Zr+Zr collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV. The kinetic freeze-out parameters ($T_{kin}$ and $\langle \beta_{T} \rangle$) versus collision centrality and particle rapidity will be presented and compared with those of light hadrons ($\pi$, $K$, $p$).
\end{linenumbers}

Speaker: Hui Liu

QM2022_LightNuclei_HuiLiu.pdf

18:10 Measurement of the hypertriton properties and production with ALICE

The ${{}^{3}_{\Lambda}\mathrm{H}}$ is a bound state of proton (p), neutron (n) and Λ. Studying its characteristics provides insights about the strong interaction between the lambda and ordinary nucleons. In particular, the ${{}^{3}_{\Lambda}\mathrm{H}}$ is an extremely loosely bound object, with a large wave-function. As a consequence, the measured (anti) ${{}^{3}_{\Lambda}\mathrm{H}}$ production yields in pp and p–Pb collisions are extremely sensitive to the nucleosynthesis models. Thanks to the very large set of pp, p–Pb and Pb–Pb collisions collected during Run 2 of the LHC the ALICE collaboration has performed systematic studies on the ${{}^{3}_{\Lambda}\mathrm{H}}$ lifetime, binding energy and production across different collision systems. The new ALICE results on hypertriton properties have a precision which is comparable with the current world averages and they can be used to constrain the state-of-the-art calculations which describe the ${{}^{3}_{\Lambda}\mathrm{H}}$ internal structure. Furthermore, with the precision of the presented production measurements some configurations of the Statistical Hadronisation and Coalescence models can be excluded leading to tighter constraints to available theoretical models.

Speaker: Francesco Mazzaschi (Universita e INFN Torino (IT))

qm2022_mazzaschi_final.pdf

18:30 Recent Hypernuclei Measurements in the High Baryon Density Region with the STAR Experiment at RHIC

Light nuclei and hypernuclei are expected to be abundantly produced in intermediate to low energy heavy-ion collisions due to the high baryon density. However, their production mechanisms are currently not well understood. Measurements of the yield and collective flow are sensitive to their production mechanisms and the dynamics of the produced medium. In particular, hypernuclei measurements may also bear implications on the hyperon-nucleon interaction, which is critical to understanding the nuclear equation of state in high baryon density medium including strangeness degrees of freedom.

The STAR Beam Energy Scan Phase II program, including fixed target Au+Au collisions and carried out during 2018-2021, is particularly suited for such studies. In this talk, the collision energy dependence of light hypernuclei $({}^{3}_{\Lambda}$H, ${}^{4}_{\Lambda}$H, ${}^{4}_{\Lambda}$He$)$ production yields in $\sqrt{s_{\rm{NN}}}=3, 19.6$ and 27 GeV Au+Au collisions will be presented. We will also report the energy dependence of light nuclei directed and elliptic flow as well as the first observation of hypernuclei $({}^{3}_{\Lambda}$H, ${}^{4}_{\Lambda}$H) directed flow in $3$ GeV collisions. These results will be compared to thermal and transport model calculations. Furthermore, precision measurements of the ${}^{3}_{\Lambda}$H, ${}^{4}_{\Lambda}$H and ${}^{4}_{\Lambda}$He lifetime and the relative branching ratio $R_{3}$ of ${}^{3}_{\Lambda}$H and ${}^{4}_{\Lambda}$H will be presented. We will also present studies of hypernuclei binding energy and Dalitz decays. The physics implications of our measurements in the context of hypernuclear structure and their production mechanisms will be discussed.

Speaker: Yue-Hang Leung (Lawrence Berkeley National Laboratory)

qm2022hypernucleiv9.pdf

18:50 New experimental observables to probe (anti)nucleosynthesis at the LHC with ALICE

The formation of light (anti)nuclei in heavy-ion collisions as well as in hadron collisions has been studied experimentally and theoretically for many decades. Two competing (anti)nucleosynthesis models are typically used to describe light (anti)nuclei yields and their ratios to other hadrons in heavy-ion collisions: the statistical hadronization model (SHM) and the nucleon coalescence model.
In this talk, new measurements of (anti)nuclei production in Pb–Pb collisions with ALICE at the LHC are presented. These measurements are compared to predictions from the state-of-the-art statistical hadronization and coalescence models and we show how (anti)nuclei can be used to measure both the chemical freezeout temperature and the baryon chemical potential of the system created in the collision with high precision. Moreover, the first measurement of event-by-event antideuteron number fluctuations in heavy-ion collisions is also presented and compared with expectations of the SHM and coalescence. This new observable represents an additional testing ground for these two production models.

Speaker: Sourav Kundu (CERN)

Lightnuclei_QM_final.pdf

Friday, 8 April

09:00 → 10:30 Plenary Session IV: Collectivity

Convener: Larry McLerran (BNL)

09:00 Initial state and approach to equilibrium (TH)

Speaker: Michał Spaliński

QM2022.Spalinski.pdf

09:30 Experimental review of collective phenomena in different collision systems (EX)

Speaker: Soumya Mohapatra (Columbia University (US))

Slides.pdf

10:00 Theoretical developments on system size dependence of collective phenomena (TH)

Speaker: Giuliano Giacalone (Universität Heidelberg)

talk.pdf

10:30 → 11:00 Coffee break

11:00 → 13:00 Plenary Session V: Jets

Convener: Marco Van Leeuwen (Nikhef National institute for subatomic physics (NL))

11:00 Jet production and suppression in heavy-ion collisions (EX)

Speaker: Leticia Cunqueiro Mendez (Roma Sapienza University)

QM2022_Cunqueiro.pdf

11:25 Experimental overview on jet substructure and medium response (EX)

Speaker: Martin Rybar (Charles University (CZ))

QM2022_Rybar.pdf

11:50 Jet quenching and jet-medium interactions (TH)

Speaker: Jasmine Therese Brewer (CERN)

JasmineBrewer-QM2022.pdf

12:30 Transport properties of QCD medium (TH)

Speaker: Jacopo Ghiglieri (SUBATECH)

ghiglieri_QM2022-2.pdf

13:00 → 14:00 Lunch boxes

14:00 → 15:00 Poster Session 3 T10

14:00 The sexaquark dilemma in neutron stars and its solution by quark deconfinement

Following the idea that a light, compact sexaquark state with quark content (uuddss) might
might be a candidate for baryonic dark matter that has gone unnoticed by experiments so far
because its decay channels are practically closed [1], we investigate its possible role in the
physics of compact stars. We find that the stringent constraints on the equation of state
from mass and radius measurements of the high mass pulsar PSR J0740+6620 and bounds
on the compactness from the tidal deformability measurement for the binary neutron star
merger GW170817 cannot be accommodated simultaneously when the sexaquark would
survive under the conditions of high densities in neutron star interiors.
As a solution to this dilemma, we present the dissociation of the sexaquark by a deconfinement
transition to color superconducting quark matter, fulfilling all present constraints from
multi-messenger astronomy.
The sexaquark mass parameter favored by the present analysis has recently been used
to predict within a thermal statistical model the yield of sexaquarks produced in heavy-ion
collisions at LHC [2].
[1] G. Farrar, 6-quark Dark Matter, arXiv:1711.10971 [hep-ph]
[2] D. Blaschke et al., Int. J. Mod. Phys. A 36 (2021) 2141005; arXiv:2111.03770 [hep-ph]

This work is supported by NCN under grant number 2019/33/B/ST9/03059.

Speaker: Mahboubeh Shahrbaf

QM2022_poster_new.pdf

14:04 The special point - a tool to extract the hybrid equation of state from neutron star observations.

In my talk, I will present the results of a systematic investigation of the possible locations of the special point (SP), a unique feature of hybrid neutron stars manifesting in their mass-radius relation. The study demonstrates that the SP is invariant both to the choice of the low density hadronic equation of state (EoS) as well as to the two phase transition construction. This is shown in [1,2,3], where the SP is used to interpret the novel multi-messenger neutron star observations in the context of hybrid stars with a deconfined quark matter core. The result is an estimate on the statistics of a measurement that could be considered as indisputable evidence for the hybrid nature of high mass stars, as well as a demonstration of a reversal in the common paradigm of hybrid star compactness. The study produced massive hybrid stars of decreasing compactness in agreement with the latest NICER measurement of pulsar PSR J0740+6620.

This work has been supported by the Polish National Science Centre (NCN) under grant number 2019/33/B/ST9/03059.

References:
[1] Cierniak, M., Blaschke, D., 2021, Astron. Nachr., 342, 5, 819. https://doi.org/10.1002/asna.202114000
[2] Blaschke, D., Cierniak, M., 2021, Astron. Nachr., 342, 1-2, 227. https://doi.org/10.1002/asna.202113909
[3] Cierniak, M., Blaschke, D., 2020, Eur. Phys. J. Spec. Top. 229, 3663. https://doi.org/10.1140/epjst/e2020-000235-5

Speaker: Mateusz Cierniak (University of Wrocław)

QM2022_Cierniak.pdf

14:08 Collective flow at SIS energies within a hadronic transport approach: Influence of light nuclei formation and equation of state

The interest in the equation of state (EoS) of nuclear matter has been renewed with the observation of gravitational waves from neutron star mergers. Since nuclear matter under similar conditions as in neutron star mergers can be studied in heavy ion collisions at low collision energies, additional information about the EoS can be extracted from the precise measurements performed at GSI or in the future at FAIR.

In this work we apply the hadronic transport approach SMASH to calculate flow coefficients that are known to be very sensitive to the EoS which enters the calculation through nuclear potentials. We present calculations for different equations of state and compare methods of taking the formation of light nuclei into account. At beam energies of $E_{\rm lab} = 1.23A\,\mathrm{GeV}$ a large fraction of nucleons is bound in clusters, therefore they are crucial to gain an understanding. Without momentum-dependent potentials the hard equation of state is preferred in the comparison to HADES data on $v_1(p_T,y)$ and $v_2(p_T,y)$ and for low transverse momenta the dependence on the clustering method is found to be strong. This work is a starting point for a detailed analysis to determine the equation of state with upgraded nuclear potentials and applying Bayesian methods.

Speaker: Justin Mohs

Mohs_poster22.pdf

14:12 Berry monopole and topology of color superconductivity

The color superconducting phase with single flavor pairing can be relevant at environments inside the core of neutron stars. In this case, the ground state is described by the BCS pairing between quarks with opposite chirality. Very recently, Li and Haldane argue that the Cooper pair inherits a non-trivial topological structure from the underlying single-particle Berry monopole for superconducting Wely semi-metal. In this work, we generalize Li-Haldane argument to the single flavor color super-conductor and uncover novel topological properties of this phase, which have been overlooked for decades. Depending on the color-spin structure, we find that either the gap function acquires topological nodal structure, as is the case for planar phase, or the gapless quasi-particle excitations carry non-zero Berry monopole. We present the evidence that the latter possibility, which Li-Haldane do not discuss, is energetically favored and is realized in the so-called color-spin locking phase, the ground state. We discuss the relevance of our findings to quark-hadron continuity, anomaly matching, and topological phase transition in Baryon-rich matter.

[1] Yi Li and F. D. M. Haldane, “Topological nodal Cooper pairing in doped Weyl metals,” Phys. Rev. Lett. 120, 067003 (2018).


[2] N. Sogabe and Yi Yin, in preparation.

Speaker: Yi Yin

Berry_flux_one_flavor_SC_pdf.pdf

14:16 Radial perturbations in neutron stars obtained from QCD

We investigate the dynamical stability of neutron stars by performing radial perturbations on their stellar structure obtained after solving the hydrostatic-equilibrium equations which uses as input a collection of equations of state obtained from successive matchings between perturbative QCD at high densities and chiral effective theory at low densities and constrained by observational data at intermediate densities where a first-order transition is expected to occur. We do this by solving a pair of first-order coupled differential equations equivalent to the original Sturm-Liouville problem to obtain the fundamental-mode frequencies characterizing stable stars. We further analyze the effects of mild and large violations of the conformal bound for the speed of sound, c_{s}=1/\sqrt{3}, in stars that can possibly contain a quark matter core. We find that some neutron-star families display an unusual behavior in the mass-radius diagram which are associated to large oscillation amplitudes near the core.

Speaker: Dr José C. Jiménez (University of São Paulo)

14:20 Particle composition and nuclear pairing models of neutron star cores: a study of transiently-accreting star MXB1659-29

The nature of the equation of state (EOS) of neutron stars is an open research problem. The high baryonic density and isospin asymmetry that characterize this system hinder first principle calculations of the EOS, its particle composition and in-medium particle interactions. Therefore, at the moment there is no consensus on the presence of quark matter in neutron star cores, or on the nuclear pairing model to describe neutron triplet superfluidity and proton superconductivity in the system. However, using cooling data from transiently-accreting neutron stars, one has obtained the first unambiguous signature of the presence of fast neutrino-cooling processes in the core of a star for the MXB 1659-29 source. Neutrino emissivity is directly related to neutron star’s core composition; thus this data can set important constraints on the EOS.

In this talk, we present the results of a study of a set of realistic relativistic mean field (RMF) EOS reproducing MXB 1659-29 luminosity and making predictions for its mass and nuclear pairing models. We also investigate whether quark matter can be present in this source and for which densities, for each EOS. Finally, we calculate the core heat capacities for all scenarios and check whether long-term measurements of temperature variation combined with inferred luminosity for a star can set them apart and potentially provide information on the star’s core composition. This is an important step towards an eventual universal equation of state for neutron stars and, therefore, towards a better understanding of the phase diagram of asymmetric matter at high densities.

Speaker: Melissa Mendes Silva (McGill University)

Melissa Mendes - QM 2022 poster.pdf

14:24 Constraining Neutron-Star Matter with Microscopic and Macroscopic Collisions

Interpreting high-energy, astrophysical phenomena, such as supernova explosions or neutron-star collisions, requires a robust understanding of matter at supranuclear densities. However, our knowledge about dense matter explored in the cores of neutron stars remains limited. Fortunately, dense matter is not only probed in astrophysical observations, but also in terrestrial heavy-ion collision experiments. In this work, we use Bayesian inference to combine data from astrophysical multimessenger observations of neutron stars and from heavy-ion collisions of gold nuclei at relativistic energies with microscopic nuclear theory calculations to improve our understanding of dense matter. We find that the inclusion of heavy-ion collision data indicates an increase in the pressure in dense matter relative to previous analyses, shifting neutron-star radii towards larger values, consistent with recent NICER observations. Our findings show that constraints from heavy-ion collision experiments show a remarkable consistency with multi-messenger observations and provide complementary information on nuclear matter at intermediate densities. This work combines nuclear theory, nuclear experiment, and astrophysical observations, and shows how joint analyses can shed light on the properties of neutron-rich supranuclear matter over the density range probed in neutron stars.

Speaker: Mr Kshitij Agarwal (Physikalisches Institut, Eberhard Karls Universität Tübingen, Germany)

20220408_Agarwal-LeFevre_QM2022-v2.pdf

14:28 The rigidity of matter at its limits: understanding the peak in the speed of sound

In the core of neutron stars, extreme gravitational fields probe the stiffness of matter at very large densities. Recent neutron-star observations indicate that ultradense matter must be stiffer than previously thought, with the speed of sound potentially rising well above its asymptotic conformal limit of $1/\sqrt{3}$ [1]. Nonetheless, the implications of this large speed-of-sound peak for the phenomenology of cold and dense QCD are far from being understood. In this work, we address the general physics requirements that must be fulfilled for the speed of sound of cold and dense QCD to have a peak surpassing the conformal limit, and propose a generic mechanism to explain this feature [2]. We build a model realization of this mechanism and explore its possible connection to the formation of diquarks, as well as the transition to quark or quarkyonic matter. Our results suggest that diquark interactions might play a pivotal role in the equation of state of highly compressed matter.

[1] Christian Drischler, Sophia Han, James M. Lattimer, Sanjay Reddy, Tianqi Zhao, Phys. Rev. C 103, 045808 (2021)
[2] Maurício Hippert, Eduardo S. Fraga, Jorge Noronha, Phys. Rev. D 104, 034011 (2021)

Speaker: Jorge Noronha (University of Illinois at Urbana-Champaign)

PosterNoronhaQM22-v0.pdf

14:32 Neutron Stars with a Crossover Equation of State

The question of whether quark matter exists in neutron stars is a long standing one. Generally one finds that a first order phase transition from baryons to quarks softens the equation of state so much that the star would collapse into a black hole. We consider a crossover equation of state, similar to the crossover that is found in lattice QCD studies at finite temperature and zero or small baryon chemical potentials. We find that with reasonable parameters it may be possible to support neutron stars up to about 2.2 solar masses. In that case 1 to 10% of the pressure would be contributed by quark matter in the central core of the highest mass stars.

Speaker: Thomas Welle (University of Minnesota)

QM2022.pdf

14:36 Bayesian inference on quark matter from observations of neutron stars

The existence of quark matter inside the cores of massive neutron stars can be probed by modern astrophysical observations. We model these hybrid stars using an (axial)vector meson extended quark-meson model to describe their quark cores, together with various hadronic models. We show that crossover phase transitions between the hadronic and quark phases can naturally create equations of state that are stiffer than both the hadronic and quark ones, enabling more massive neutron stars. We also show that the properties of the maximum mass hybrid star can be used to constrain the parameters of the quark model, while radius limits from GW170817 also give restraints on them. We combine gravitational wave and NICER measurements in our Bayesian analysis to determine the properties of quark matter and the hadron-quark phase transition.

Speaker: János Takátsy

QM2022_poster_Janos_Takatsy.pdf

QM2022_poster_slides.pdf

14:40 Non-radial oscillation modes in hybrid stars: consequences of a mixed phase

We study the possible existence of deconfine quark matter in the core of neutron stars. A relativistic mean field model is used to describe the nuclear matter at low densities while Nambu--Jona-Lasinio model is used to describe the quark matter at high densities. A Gibbs construct is used to describe the quark-hadron phase transition at large densities and at zero temperature. Within the model, as the density is increased, a mixed phase appears at about $2.5$ times the nuclear matter saturation density $(\rho_0)$ and ends at about $5~\rho_0$ beyond which pure quark matter phase appear. It turns out that a stable hybrid star of maximum mass, $M=2.27 ~ M_{\odot}$ with radius $R=14$ km, can exist with a quark matter core in a mixed phase only. As the density decreases from the center to the surface, there is a sharp increase of the velocity of sound at the point where the quark-hadron phase transition occurs. This leads to the possibility of low frequency non-radial oscillations, the $g$ modes, in hybrid stars in contrast to canonical neutron stars which do not have such quark matter core. The higher $f$ modes frequencies of neutron stars get enhanced in the presence of quark matter core in hybrid stars. The magnitude of $g$ mode frequencies decrease with increase the repulsive interaction in quark matter.

Speaker: Mr Deepak Kumar (Physical Research Laboratory)

14:44 Magnetic effects in dense nuclear matter through Skyrme model

Skyrme model is among the simplest extensions of chiral effective theory including anomaly. Within such framework we investigate how an external magnetic field deforms a Skyrmion while preserving its topological winding. A crystal constituted by multiple magnetically deformed Skyrmions provides us insights of the ground state of nuclear matter in strong magnetic field. We manifest such Skyrme crystal can realize the previously found \pi^0 domain wall structure as one special class of solution. Another class of solution with both charged and neutral pions is revealed by us, entitled "Normal Crystal". For these two classes of baryonic structure, we establish their thermodynamics and phase diagram, demonstrating how they compete to take place as the ground state, underneath which is the topological transmutation between \pi^3(S^3) and \pi^1(S^1).

Speaker: Zebin Qiu (The University of Tokyo)

2022.4.8_Zebin_Qiu.pdf

14:48 When Phase Transitions Wave

The observation of gravitational waves from neutron stars opens up the possibility to learn about Quantum Chromodynamics at baryon densities above nuclear saturation and at very low temperatures. Interestingly, introducing non-trivial structure in the speed of sound sourced by changes in the degrees of freedom (possibly quarks) of ultra-dense matter can lead to extremely heavy neutron stars with unusual tidal deformabilities that lead to specific signatures in gravitational wave observables [1]. Here, I will discuss these signatures and describe their measurability with current and future gravitational wave detectors.

[1] H. Tan, J. Noronha-Hostler, and N. Yunes, Phys. Rev. Lett. 125, 261104 (2020).

Speaker: Prof. Nicolas Yunes

14:00 → 15:00 Poster Session 3 T11_1

14:00 Study of $\phi$ mass modification with $K^{+}K^{-}$ decay in p+A collisions at J-PARC

We are proposing an experiment to study $\phi$ mass modification through $K^{+}K^{-}$ decay in p+A collisions at J-PARC. We exect to obtain several hundred thousands of $\phi \rightarrow K^{+}K^{-}$ decays in p+C and p+Cu collisions with 30 GeV proton beams. The $\phi$ mass modification is sensitive not only to the $K^{+}K^{-}$ modification but also to the branching ratio due to the small Q value. In this presentation, we discuss the physics of $\phi$ in nucleus, the design of the experiment, and the R&D status and plan of the kaon identification detectors.

Speaker: Dr Susumu Sato (Japan Atomic Energy Agency (JP))

0405_2022_Qm2022_SSato_v009.pdf

14:04 Heavy quarkonia in hot and dense strongly magnetized quark matter

In this work, we address how the properties of a specific
hadronic probe in the form of heavy quark-antiquark bound states
can be affected in a thermal medium
of quarks and gluons with finite chemical potential ($\mu$) under
the influence of a strong magnetic field, unlike the same
in the absence of finite $\mu$ reported in the literature.
The aforesaid problem may be relevant to the matter
produced in relativistic heavy ion collisions. The effect of strong magnetic field
on the properties of the heavy quarkonia in a baryon symmetric matter
has recently been studied either by computing the potential perturbatively or by a
generalized Gauss law.
However, the medium correction to the non-perturbative string term
gets inducted by dimension-two gluon condensate in usual resummed
HTL propagator.

We have started with the general covariant tensor
structure of the gluon self-energy in above environment for a thermal QCD
medium with finite $\mu$ and have
obtained the real and imaginary parts of
resummed gluon propagator by calculating the relevant
form factors. These real and imaginary parts of the resummed propagator
in the static limit facilitate the computation of
the complex potential between $Q$ and $\bar Q$ in coordinate
space through inverse Fourier transform. We have included
a phenomenological non-perturbative term induced by the dimension two
gluon condensate to the usual HTL resummed propagator to evaluate the medium modification to string part of the $Q\bar{Q}$ potential.
We observe that in the presence of the baryon asymmetry, the real-part of
potential becomes slightly more attractive.
The more attractive nature of the real part can be
understood in terms of the Debye mass which inherits the medium properties
and decreases with the chemical potential. The magnitude of the
imaginary-part gets reduced in the medium having finite chemical potential.
We have solved the radial part of the Schr\"{o}dinger equation numerically plugging the real-part of the potential to obtain the energy eigenvalues which are utilized to calculate the binding energy of quarkonia.
The decay width has been calculated considering the imaginary part of the potential as a perturbation in the small distance limit.
Presence of the chemical potential in the medium
leads to the enhancement of binding energies and the reduction
of thermal widths of $Q \bar Q$
ground states, respectively. Finally, we compute the dissociation temperatures of $J/\psi$ and $\Upsilon$ states by
studying the relative competition between the binding energy and decay width.
Dissociation temperatures are found to have slightly larger values in the medium
having non-zero baryon density. We have noticed that $J/\psi$ gets dissociated at
$1.64~T_c$, $1.69~T_c$, and $1.75~T_c$, whereas $\Upsilon$ is
dissociated at $1.95~T_c$, $1.97~T_c$ and $2.00 ~T_c$, for
$\mu=0, 60$ and $ 100 $ MeV, respectively. In conclusion, the strongly
magnetized hot quark matter having non-zero baryon density prevents
early dissociation of quarkonia as compared to the baryonless matter.

Speaker: Mr Salman Ahamad Khan (Department of Physics, Indian Institute of Technology Roorkee, Roorkee 247 667, India)

QM2022_Salman.pdf

14:08 Measurements of prompt and non-prompt D meson production and anisotropy in Pb-Pb at $\sqrt{s_{\rm NN}}$ = 5.02 TeV with ALICE

The production of heavy quarks (charm and beauty) in heavy-ion collisions occurs via hard partonic scattering processes at early times. Thus they represent a unique probe of the properties of the quark-gluon plasma (QGP), as they interact with the system throughout its entire lifetime. The heavy-flavour nuclear modification factor ($R_{\rm AA}$) and elliptic flow ($v_{\rm 2}$) are two of the main experimental observables that allow us to investigate the interaction strength of heavy quarks with the expanding medium. The $R_{\rm AA}$ measurements provide information about the modification of heavy-flavour hadron yields in heavy-ion collisions with respect to pp collisions, after the proper binary NN collision scaling is applied on the latter system. The comparison of the $R_{\rm AA}$ of charm, beauty and light-flavour hadrons can provide information about the colour-charge and parton-mass dependence of the parton energy loss.

High precision $v_{\rm 2}$ measurements of heavy-flavour particles provide stringent information about the thermal degrees of freedom of heavy quarks in the QGP, path-length dependence of heavyquark in-medium energy loss and recombination effects. In this contribution, prompt and non prompt D-meson $R_{\rm AA}$ and $v_{\rm 2}$ measurements in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV, performed with the ALICE detector will be presented.

Speakers: Biao Zhang (Central China Normal University CCNU (CN)), Dr Renu Bala (University of Jammu (IN))

BiaoRenu_qm22poster_v4.pdf

14:12 $\Upsilon$(1S) polarization in pp collisions at $\sqrt{s}$ = 13 TeV with ALICE

The quarkonium production mechanism in elementary proton-proton (pp) collisions remains unclear. Indeed, none of the production models is able to describe it over the full kinematic range. One of the most discriminating observable between models is the polarization state of quarkonium produced in high energy collisions. The ALICE experiment has measured the polarization of inclusive J/$\Psi$ produced in pp collisions at $\sqrt{s} = $ 7 and 8 TeV and of the inclusive J/$\Psi$ and $\Upsilon({\mathrm{1S}})$ produced in Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02$ TeV. In this contribution, we will present the ALICE measurement for $\Upsilon$(1S) polarization in pp collisions at $\sqrt{s}=13$ TeV. The measurement is done at forward rapidity ($2.5 < y < 4$) via the dimuon decay channel ($\Upsilon({\mathrm{1S}})\rightarrow \mu^{+}\mu^{-}$) both in helicity and Collins-Soper frames and the results are given in $p_{\mathrm{T}}$ intervals, from 0 to 15 GeV/$c$.

Speaker: Ms Yanchun Ding (CCNU and IP2I)

dQM2022_poster_final.pdf

14:16 Measurements $\rm{\Lambda^{+}_{c}}$ production cross section as a function of multiplicity and charm fragmentation fractions in pp and p-Pb collisions with ALICE

The production cross sections of open heavy-flavour hadrons in pp and p-Pb collisions are typically described within the factorisation approach as the convolution of the parton distribution functions of the incoming protons, the perturbative QCD partonic cross section, and the fragmentation functions. The latter are typically parametrised from measurements in ${\rm e^+e^-}$ collisions, assuming universality across different collision systems. Measurements of charm baryon and meson production in pp and p-Pb collisions, and measurements of their yield production as a function of multiplicity, help to investigate hadronization processes and to study how these processes are modified across systems, from pp to Pb-Pb and from low to high multiplicities.

In this poster, the latest measurements of $\Lambda^+_{\rm c}$ down to $p_{\rm T}=0$, performed with the ALICE detector at midrapidity in pp and p–Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV, are presented. This is the first ALICE measurement, down to $p_{\rm T}=0$, of the $\Lambda^+_{\rm c}/{\rm D^0}$ ratio in pp and p–Pb collisions. This result, together with the already published measurement of the cross section for the ${\rm D^0}$, ${\rm D^+}$, ${\rm D^+_{\rm s}}$ and ${\rm \Xi^0_{\rm c}}$ production, allows an evaluation of the total section and fragmentation fractions. The result unambiguously shows that the charm fragmentation is not universal across leptonic and hadronic collision systems. The $\Lambda^+_{\rm c}/{\rm D^0}$ yield ratios as measured as a function of charged particle multiplicity in pp and p-Pb collisions is also shown and compared to different hadronization models.

Speakers: Annalena Sophie Kalteyer (GSI - Helmholtzzentrum fur Schwerionenforschung GmbH (DE)), Oveis Sheibani (University of Houston (US))

QM2022-3-2.pdf

14:20 Nuclear modification factors of prompt and non-prompt J/$\psi$ in Pb$-$Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV at midrapidity with ALICE

Ultrarelativistic nuclear collisions offer an opportunity to study the production of heavy quarkonia as well as the properties of nuclear matter at extreme temperature and density. Heavy quarks are considered excellent probes to study the properties of the state of matter where quarks and gluons are deconfined, known as quark-gluon plasma (QGP) expected to be formed in nuclear collisions.
Prompt J/$\psi$ are produced directly or from the feed-down of higher-mass charmonium states, and are sensitive to suppression and recombination effects in the QGP and at hadronization. Non-prompt J/$\psi$ production originates from the weak decays of beauty hadrons and is directly related to that of beauty quarks. In nuclear collisions, such measurements are important to investigate the energy loss dependence on the quark mass in the hot nuclear medium as well as for providing additional constraints to extract heavy-quark diffusion coefficients from experimental data.
In this contribution, ALICE results on nuclear modification factors ($R_{\rm AA}$) of prompt and non-prompt J/$\psi$, reconstructed at midrapidity in the dielectron decay channel, as a function of $p_{\rm T}$ and centrality will be presented and compared with theoretical predictions. Presented results are obtained by analyzing data from Pb$-$Pb collisions collected at $\sqrt{s_{\rm NN}}$ = 5.02 TeV during LHC Run 2. In addition, prompt and non-prompt J/$\psi$ cross sections in pp collisions at the same energy will also be shown.

Speaker: Mr Himanshu Sharma (Polish Academy of Sciences (PL))

hsharma_PosterQM22_.pdf

14:24 Influence of string interactions on strangeness yields in dense systems in Pythia8/Angantyr

In this talk, we present our ongoing work on the inclusion of string interactions, namely rope hadronization and string shoving in heavy ion (PbPb and XeXe) collisions, as an alternative to QGP. Both string shoving, which is the repulsion between two strings, and rope hadronization, where strings in close proximity form higher-order colour multiplets, have been earlier observed to explain QGP-like effects in p-p collisions such as final state collective flow and strangeness enhancement.
The main challenge involved in implementing such mechanisms in dense environments is that the majority of strings in dense systems lie in random spatial orientation, which makes calculating the force among all strings during an event a complex problem.
In our approach, we use a special Lorentz frame, where a pair of string pieces are in parallel planes with respect to each other. Hence, for a whole Pythia/Angantyr event, every possible string pair is boosted to this frame to calculate the shoving and rope effects.
This novel approach of string shoving and rope hadronization can produce the cumulative result of generating QGP-like effects in dense environments, for both small and large systems. In this talk, we present our new implementation - the Gleipnir framework - in Pythia8/Angantyr and results from strangeness yield analyses performed in high-multiplicity p-p and heavy-ion collisions with comparison to data for both minimum bias and jet triggered events.

Speaker: Smita Chakraborty

SChak_QM22_poster.pdf

14:28 Cold Nuclear Matter Effects on $J/\psi$ and D Meson Production at High Baryon Densities

Open heavy flavors and quarkonium have played important roles in the understanding of the QCD matter produced at high temperatures and low baryon densities. However, they could also provide crucial information about QCD at the lowe center of mass energies employed to probe high baryon density matter at existing or planned facilities.

For example, a nonperturbative contribution to charm production, intrinsic charm, has long been speculated, with much contradictory empirical evidence. LHCb recently reported evidence for intrinsic charm in $Z + {\rm jet}$ events at $\sqrt{s} = 13$~TeV [1]. While $J/\psi$ production by intrinsic charm would normally only manifest itself outside the range of the LHC detectors, even at forward rapidity, the high $Q^2$ of these events allowed for their detection.

On the other hand, at low center of mass energies, $J/\psi$ and $D$ meson production by intrinsic charm could manifest itself at midrapidity, as described for the SeaQuest experiment at Fermilab [2]. This talk will explore the rapidity and $p_T$ dependence of an intrinsic charm signature for laboratory beams of 40~GeV and higher, both in $p+p$ and $p+A$ interactions and place the results in context of previous experimental evidence [3].

[1] https://lhcb-public.web.cern.ch/Welcome.html#IC, 27 July 2021.

[2] R. Vogt, Limits on Intrinsic Charm Production from the SeaQuest Experiment, Phys. Rev. C 103, 035204 (2021).

[3] R. Vogt, in preparation, to be submitted to Phys. Rev. C.

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics (Nuclear Theory) under contract number DE-SC-0004014 and supported by LDRD project 21-LW-034.

Speaker: Ramona Vogt

QM2022_poster_RVogt.pdf

14:32 Analysis of b-jet production in p-Pb and pp collisions at \sqrt{s_NN} = 5.02 TeV with ALICE

This poster presents the final recent measurements of $p_{\rm T}$-differential production cross section of charged-particle anti-$k_{\rm T}$ $R = 0.4$ b jets in pp and p--Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV done by the ALICE collaboration. The production cross sections were measured down to $p_{\rm{T}}$ = 10 GeV/$c$, which is lower than in previous measurements of b jets done at the LHC. The spectra were used to evaluate the corresponding nuclear modification factor and the fraction of b jets among inclusive jets. The nuclear modification factor is found to be consistent with unity, suggesting that within the current statistical and systematical uncertainties b-jet production is not sensitive to CNM effects in the measured $p_{\rm{T}}$ range. The measurements are well reproduced by POWHEG NLO pQCD calculations with PYTHIA fragmentation.

Speaker: Artem Isakov (Czech Academy of Sciences (CZ))

2022-03-23-aisakov_QM22_v11.pdf

14:36 Angular correlations of heavy-flavour decay electrons and charged particles in pp collisions at $\sqrt{s}=$ 5.02 TeV with ALICE at the LHC

Two-particle azimuthal correlations triggered by electrons from heavy-flavour hadron decays can be used for heavy-flavour jet studies. By changing the momentum scales of the trigger and associated particles, the heavy-flavour jet structure can be investigated. In pp collisions, heavy-flavour correlations can be used in particular to study the production and fragmentation of heavy quarks.

In this poster, we present the recent ALICE measurements of azimuthal correlations of high-$p_{\rm T}$ heavy-flavour decay electrons with charged particles in pp collisions at $\sqrt{s}$ = 5.02 TeV from the LHC Run 2 data. The results from pp collisions are compared with PYTHIA8 calculations to investigate the fragmentation processes.

Speaker: Ravindra Singh (Indian Institute of Technology Indore (IN))

Poster_QM2022_HFEh.pdf

14:40 Measurement of $\mathrm{D}$-meson production as a function of charged-particle multiplicity in proton--proton collisions at $\sqrt{s} = 13$ TeV with ALICE at the LHC

The study of charm production as a function of charged-particle multiplicity allows the investigation of the role of multi-parton interactions (MPI), and provides insight into the processes occurring at the partonic level and on the interplay between the hard and soft particle production mechanisms in proton--proton (pp) collisions. In this contribution, measurements of open heavy-flavor production as a function of charged-particle multiplicity, via the study of the $\mathrm{D}$-meson self-normalized yields in pp collisions at the center-of-mass energy of $\sqrt{s} = 13$ TeV is presented. The $\mathrm{D}$-meson yields are measured in different $p_{\rm{T}}$ intervals at midrapidity via their hadronic decay channels. The $\mathrm{D}$-meson self-normalized yield is found to increase stronger than linearly with increasing charged-particle multiplicity, with a significant $p_{\rm{T}}$ dependence. The measurements are compared with the results in pp collisions at $\sqrt{s} = 7$ TeV and model calculations.

Speaker: Yoshini Bailung (Indian Institute of Technology Indore (IN))

QuarkMatter2022_v5.pdf

14:44 D-meson production as a function of transverse spherocity in pp collisions at √s =13 TeV with ALICE

Measurements of the production of heavy-flavour hadrons in proton-proton collisions
provide the baseline for the observations of hot-medium effects in heavy-ion collisions,
as well as tests of perturbative QCD calculations. Moreover, measurement of charm-
hadron production in hadronic collision systems allow investigating the charm-quark
hadronization mechanisms.
Measurements based on event shape observables allow isolating events according to
their topologies, dominated by soft and hard processes. They provide information about
the energy distribution in an event and provide tools to study the perturbative as well as
non-perturbative aspects of the QCD. The event shape observables permit to isolate
jetty-like (high-p T jets) and isotropic (partonic scattering with low Q 2 ) events.
In this contribution, recent results on open-charm meson production measured by the
ALICE Collaboration in pp collisions at √s = 13 TeV from the Run 2 of the LHC will be
presented. Measurements of the averaged self-normalized yield as a function of
transverse spherocity (S_{0} ) at midrapidity for D ∗+ + , D + and D 0 mesons will be shown. The
self-normalized yield will be calculated in different multiplicity, transverse spherocity
and p T intervals. In addition, comparison with measurements performed at √s = 7 TeV
will be shown and comparison with models will be discussed.

Speaker: Randhir Singh (University of Jammu (IN))

Poster_QM_2022_Randhir.pdf

14:48 Measurement of electrons from beauty-hadron decays in pp collisions at $\sqrt{s}$ = 13 TeV with ALICE

The measurement of heavy-flavour (charm and beauty) production in proton-proton (pp) collisions at the LHC provides a crucial information about quantum chromodynamics (QCD) in high-energy regime. Due to their large masses, heavy quarks are mainly produced in initial hard scattering processes. Therefore, heavy-flavour production cross section represents a primary benchmark for perturbative QCD (pQCD) calculations. Furthermore, heavy-flavour measurements in pp collisions provide a reference for measuring nuclear modification in nucleus-nucleus collisions.

In this contribution, the $p_{\rm T}$-differential production cross section of electrons from beauty-hadron decay electrons in pp collisions at $\sqrt{s}$ = 13 TeV with ALICE detector at midrapidity will be reported. Electrons from beauty-hadron decays were extracted based on the distance of closest approach (DCA) to the collision vertex. Comparison of the result with the FONLL (Fixed-Order with Next-to-Leading Log) pQCD calculation will also be shown.

Speakers: Jonghan Park (Inha University (KR)), Vivek Singh (Department of Atomic Energy (IN))

220408_QM_poster.pdf

14:52 Charmonium abundance as a probe for remnants of confinement

The charm quark at energies of the LHC and above is expected to remain well out of chemical equilibrium,with its abundance dominated by initial stage production, and yet be abundantly enough produced ($N_{c\bar{c}} \simeq 10^2$) for coalescence to be non-negligible.
Using a simple analytically solvable model, we argue that it makes charmonium abundance the ideal probe of remnants of confinement, expected to be present at arbitrary high temperature [1,2] but thermodynamically irrelevant, since the nearest neighbor thermal scale $1/T$ is parametrically smaller than the confinement scale. We show that confinement remnants, while not affecting averages and higher cumulants of light and strange hadrons, will dramatically affect charm recombination dynamics, preventing the onset of charmonium and charmed baryon enhancement for arbitrary $\sqrt{s}$ and system size.

[1] D. Zwanziger, hep-ph/0303028 (PRD)
[2] G. Bali et al, hep-lat/9306024 (PRL)
[3] A. Maas et al, hep-ph/0408074 (EPJC)

Speaker: Mr Paulo Henrique De Moura (IFGW Unicamp)

DeMoura_QM2022.pdf

14:00 → 15:00 Poster Session 3 T11_2

14:00 CBM performance for (multi-)strange hadron measurements using Machine Learning techniques

The Compressed Baryonic Matter (CBM) experiment at FAIR will investigate the QCD phase diagram at high net-baryon density ($\mu_{B} > 400\ \textrm{Me}V$) in the energy range of $\sqrt{s_{NN}} = 2.9−4.9\ \textrm{Ge}V$. Precise determination of dense baryonic matter properties requires multi-differential measurements of strange hadron yields, both for most copiously produced kaons and $\Lambda$ as well as for rare (multi-)strange hyperons and their anti-particles.
In this presentation, the CBM performance for the multi-differential yield measurements of strange hadrons ($K_{s}^{0}$, $\Lambda$, and $\Xi^{-}$) will be reported. The strange hadrons are reconstructed via their weak decay topology using the Kalman Filter algorithm. Machine Learning techniques, such as XGBoost, are used for non-linear multi-parameter selection of weak decay topology, resulting in high signal purity and efficient rejection of the combinatorial background. Yield extraction and extrapolation to unmeasured phase space is implemented as a multi-step fitting procedure, differentially in centrality, transverse momentum, and rapidity at different collision energies. Variation of the analysis parameters allows estimating systematic uncertainties. A novel approach to study feed-down contribution to the primary strange hadrons using Machine Learning algorithms will also be discussed.

Speaker: Mr Shahid Khan (Eberhard Karls University of Tübingen, Tübingen, Germany)

CBM performance for (multi-)strange hadron measurements using Machine Learning techniques (QM2022) slides.pdf

14:04 Measurement of non-prompt $\Lambda_c^+$ production in pp collisions at $\sqrt{s}$ = 13 TeV with ALICE

Measurement of non-prompt $\Lambda_c^+$ production in pp collisions at $\sqrt{s}$ = 13 TeV with ALICE

Daniel Battistini for the ALICE Collaboration

In proton-proton (pp) collisions, the production of HF hadrons is typically described as a convolution of the parton distribution functions of the colliding protons, the partonic cross section, and the Fragmentation Functions (FFs). The latter describes the hadronisation of the heavy quarks in the different hadron species, and, since this process is non-perturbative, it is usually parametrised from measurements in $e^+e^-$ collisions. However, recent studies by the ALICE Collaboration show that the ratio between the production of charm baryons with respect to mesons is significantly higher in hadronic collisions compared to $e^+e^-$ interactions, invalidating the assumption that the FFs are independent of the collision system.

This contribution presents an extension of the studies on HF-baryon production in hadronic collisions to the beauty sector, via the measurement of the transverse-momentum-differential production cross section of $\Lambda ^+_c$-baryon originating from beauty-hadron decays in pp collisions at $\sqrt{s}=$ 13 TeV. The measurement will also be compared to theoretical predictions based on fixed order plus next to the leading logarithm pQCD calculations folded with the beauty-hadron to $\Lambda ^+_c$ decay kinematics from PYTHIA8 simulations.

Speaker: Daniel Battistini (Universita e INFN Torino (IT))

2022-03-29-20220408_npLc_QM22_4_0.pdf

14:08 D$^0$ meson production in dependence on the transverse activity classifier $R_{\rm T}$ in pp collisions at $\sqrt{s}$=13 TeV with the ALICE experiment

The origin of possible collective phenomena in pp collisions with high final-state multiplicity still remains an open question. Recent theories explain the presence of collectivity with cold QCD effects. These can be studied in experiments by categorizing the events with transverse activity classifier $R_{\rm T}$, which is correlated to the intensity of these QCD effects. The ALICE detector allows high-precision measurements of heavy flavour down to low transverse momenta. With the help of the heavy-flavour probes in pp collisions we can better understand colour-charge and mass dependence of parton production and fragmentation, while $R_{\rm T}$-differential measurements allow for the testing of flavour dependence of QCD processes at the soft-hard boundary.

In this poster we will present the latest results of the D$^0$ meson production studies in dependence on the transverse activity classifier $R_{\rm T}$ in pp collision data at $\sqrt{s}$=13 TeV.

Speaker: Laszlo Gyulai (Wigner Research Centre for Physics (Wigner RCP) (HU))

Gyulai_QM2022.pdf

14:12 Beauty measurement prospects with ALICE 3

Heavy-flavour quarks (charm and beauty) are produced on a very short time scale in initial hard-scattering processes. They experience the entire evolution of the ultrarelativistic-collision which makes them excellent probes for the characterization of the quark-gluon plasma (QGP) formed in heavy-ion collisions.

In particular, the comparison between beauty and charm measurements is a crucial tool for testing our understanding of mass-dependent energy loss in heavy-ion collisions. Measurements of beauty production in pp collisions are important to test perturbative QCD (pQCD) calculations, as well as to provide the baseline for Pb–Pb measurements. In p–Pb collisions, beauty-production is crucial to isolate cold nuclear matter effects.

The design of the next-generation detector for the heavy-ion program at the LHC, ALICE 3, features extremely good vertex resolution, particle identification of a broad range, and a large rapidity coverage to enable high-precision measurements of beauty production and elliptic flow in AA and pp collisions.

In this poster, the reconstruction performances of beauty hadrons at ALICE 3 will be shown, focusing the attention on the exclusive hadronic decays $B^{+}\to\overline{D^{0}}\pi^{+}$ in pp and AA collisions.

Speakers: Antonio Palasciano (Universita e INFN, Bari (IT)), Deepa Thomas (University of Texas at Austin (US))

Poster_BPlus_ALICE3_QM2022.pdf

14:16 Reconstruction of beauty jets in proton-proton collisions at $\sqrt{s}=13\,$TeV with ALICE

In this contribution, the performance of a beauty-jet tagging algorithm based on transverse impact-parameter threshold cuts will be discussed for data collected by the ALICE experiment in proton-proton collisions at $\sqrt{s}=13\,$TeV. Owing to the relatively large lifetimes and the cascade of weak decays of beauty hadrons, the measurement of the impact parameter of tracks within jets can be utilised to select beauty jets.
Measuring the beauty-jet production cross section in proton-proton collisions is a fundamental step towards a thorough testing of QCD calculations for the production and fragmentation of heavy flavours in nucleon-nucleon collisions. Thereby, the ALICE experiment offers excellent capabilities to assess theory predictions down to low $p_\text{T,Jet}$ due to its unique tracking performance.
In addition, the investigation of beauty-jet observables in proton-proton collisions is a reference for respective analyses on heavy-ion collisions. As such, it opens the possibility to study the mass dependence of particle interactions with the Quark-Gluon Plasma (QGP).

supported by the DFG GRK2149 and BMBF ErUM FSP-T01 AL-
ICE 0519PMCA1

Speaker: Katharina Demmich (Westfaelische Wilhelms-Universitaet Muenster (DE))

KDemmich_QM2022.pdf

14:20 Probing Gluon Dynamics and Hadronization with Heavy Flavor Production at the Future Electron Ion Collider

Heavy quarks, due to their large external masses, are produced predominantly through initial hard scatterings involving gluons in high energy ion-ion and electron-ion collisions. This makes them unique probes to study QCD emergent properties of the hot QGP as well as of the cold nuclear medium. Measurements of heavy quark hadron production also offer new insights into the hadronization mechanisms in these collisions. With high luminosity electron-ion collisions for a range of ions at the future Electron Ion Collider (EIC), a new generation of experiments will enable precision investigations of gluon dynamics and hadronization in nucleons and nuclei.

In this talk, we will present physics simulation studies utilizing a silicon tracker optimized for heavy quark measurements at the future EIC. These studies include projections for heavy quark production with polarized and unpolarized beams to constrain parton distribution functions, correlation measurements to study hadronization, and baryon to meson ratios to study hadrochemistry. In addition, we will discuss the detector and luminosity requirements for these measurements to be able to extract the science.

Speaker: Xin Dong (LBNL)

20220407_QM_HFEIC.pdf

14:24 $J/\psi$ production in isobaric collisions at $\sqrt{s_\mathrm{NN}}$ = 200 GeV with the STAR experiment

J/$\psi$ is an important probe to the properties of the quark-gluon plasma (QGP) created in heavy-ion collisions. Measurements from SPS, RHIC, and the LHC experiments show that J/$\psi$ production in heavy-ion collisions is an interplay of several effects, including dissociation and regeneration in QGP and cold nuclear matter effects. Studying the properties of the QGP via J/$\psi$ requires a good understanding of all these effects which is very challenging and requires high precision. In 2018, STAR collected a large sample of isobaric collisions ($^{96}_{44}Ru$ + $^{96}_{44}Ru$ and $^{96}_{40}Zr$ + $^{96}_{40}Zr$) at $\sqrt{s_\mathrm{NN}}$ = 200 GeV. The total number of good minimum bias triggered events is around 4 billion. This dataset provides a unique opportunity to perform centrality and transverse momentum ($p_T$) differential measurements of J/$\psi$ yields with good precision and in fine bins.
In this contribution, precision measurements of inclusive $J/\psi$ production in isobaric collisions at $\sqrt{s_\mathrm{NN}}$ = 200 GeV via the $e^{+}e^{-}$ decay channel will be presented. The centrality and $p_{T}$ dependences of the nuclear modification factor $R_\mathrm{AA}$ and $\left\langle p_{\rm{T}} \right\rangle$ as a function of centrality will be shown. The first measurement of the ratio of $\psi(2S)$ yield over that of J/$\psi$ in heavy-ion collisions at RHIC will also be presented.

Speaker: Yan Wang

QM_poster_slides Yan_20220408.mp4

QM_poster_slides Yan_20220408.pdf

14:28 Measurements of $D^{0}$-tagged Jet Spectra and Radial Profiles in Au+Au collisions from STAR

Measurements of hard probes such as jets and heavy flavor hadrons are essential to study the microscopic properties of the Quark-Gluon Plasma. In particular, due to their large intrinsic mass, measurements involving heavy flavor quarks are important to understand the mass dependence of the parton energy loss. With the Heavy Flavor Tracker at STAR, the opportunity to use fully reconstructed $D$ mesons to tag a clean and large sample of charm jets is enabled as combinatorial backgrounds can be removed by requiring a secondary $D$ meson decay vertex. In this poster we present the details of the first measurements of $D^{0}$-tagged jet spectra and radial profiles in Au+Au collisions at $\sqrt{s_{NN}}=$ 200 GeV. We introduce a new approach of simultaneously subtracting the residual $D^{0}$-jet combinatorial background and applying efficiency corrections using the $_{s}\mathcal{P}$lot method. We additionally show the central-to-peripheral nuclear modification factor, $R_{\rm CP}$, as a function of $D^{0}$-jet transverse momentum. Finally, we compare our data to measurements from the Large Hadron Collider, and PYTHIA 8 simulations and various heavy quark transport models.

Speaker: Mattew Kelsey

Kelsey_HFJet_Poster_QM22.pdf

14:32 Strange hadron and resonance production in Au+Au collisions at RHIC Beam Energy Scan

Strangeness production has been suggested as a sensitive probe to the early-time dynamics of the nuclear matter created in heavy-ion collisions. Transverse momentum distributions and yields of strange hadrons and resonances provide important information about the particle production mechanisms and help us to understand the properties of the created medium and its evolution in these collisions. RHIC Beam Energy Scan (BES) program covers a wide range of energies from $\sqrt{s_{\rm NN}} = 62.4$ - 3 GeV. Of particular interest is the high baryon density region which is accessible through the STAR fixed-target (FXT) program, extending the energy reach down to 3 GeV

This poster will report on the measurements of strange hadrons and resonances production using the data from Phase-I ($\sqrt{s_{\rm NN}}=7.7-54.4$ GeV) and new data from Phase-II ($\sqrt{s_{\rm NN}}=27, 19.6, 14.6$ and 3 GeV) of the BES program in Au+Au collisions. These results include the transverse mass spectra, rapidity density distributions, and particle ratios of strange hadrons and resonances ($K^0_S,~K^{*0},~\Phi,~\Lambda, ~\Xi,~\Omega$). The collision centrality dependence of the yields and particle ratios will be presented. In addition, results will be compared with those from higher collision energies.

Speaker: yingjie zhou (central china normal university)

Yingjie_qm22poster_v5.pdf

14:36 Commission the machine learning technique to the non-prompt J/$\Psi$ measurement in Pb--Pb collisions with ALICE

Quarkonium production is one of the essential probes for studying the properties of the quark-gluon plasma (QGP) created in relativistic heavy-ion collisions. The suppression of J$/\psi$ meson due to colour screening in medium and medium-induced dissociation was initially proposed as direct evidence of QGP formation. The non-prompt component of J$/\psi$ production from b-hadron decays allows one to access the interaction of beauty quarks with the QGP. The main challenge to extend the measurements to low $p_{\rm T}$ is the huge combinatorial background. The machine learning approach has been used in this data analysis to improve J/$\psi$ meson signal-to-background ratio.

In this poster, the performance of the new machine learning approach, applied on data of Pb--Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV, will be presented. The signal reconstruction efficiency and signal over background ratio, obtained from machine learning approach, will be compared with the classical cut approach, as a function of centrality and $p_{\rm T}$. A similar comparison between the two methods will be eventually discussed for efficiency corrected quantities, such as yields.

Speaker: Pengzhong Lu (University of Science and Technology of China (CN))

QM2022.pdf

14:40 Very low-$p_{T}$ J/$\psi$ production in Au+Au collision at $\sqrt{s_{_{\rm NN}}}$ = 200 GeV at STAR

The strong electromagnetic field generated by the colliding nuclei in heavy-ion collisions can be represented by a spectrum of equivalent photons, leading to photon-induced interactions. Significant enhancements of the J/$\psi$ production via $e^{+}e^{-}$ decay channel at very low transverse momentum ($p_{T}$) have been observed by the STAR and ALICE collaborations in peripheral heavy-ion collisions. The excess yields exhibit a much weaker centrality dependence compared to the expectation for hadronic production, and are consistent with coherent photon-nucleus interactions. Measurement of J/$\psi$ production via $\mu^{+}\mu^{-}$ decay channel can provide additional inputs to investigate these phenomena.
In 2014 and 2016, the STAR experiment recorded large samples of Au+Au collisions at $\sqrt{s_{_{\rm NN}}}$ = 200 GeV with the di-muon trigger enabled by the Muon Telescope Detector. In this presentation, we will show the measurement of invariant yield and nuclear modification factor of $J/\psi$ at $p_{T} <$ 0.15 GeV/c via $\mu^{+}\mu^{-}$ decay channel. Physics implications will also be discussed.

Speaker: Ziyang Li

video_poster_ziyang.mp4

Ziyang_QM2022.pdf

14:44 Accessing saturation and subnuclear structure with multiplicity dependent J/ψ production in p+p and p+Pb collisions

We compute the production of J/ψ mesons in different rapidity bins as a function of event activity in p+p and p+Pb collisions at LHC energies within the color glass condensate framework combined with non-relativistic QCD (NRQCD) or an Improved Color Evaporation model (ICEM) to describe the J/ψ hadronization. We demonstrate that deviations from a linear increase of J/ψ multiplicity with increasing charged hadron multiplicity is sensitive to gluon saturation and the details of sub-nucleonic fluctuations in the proton and nucleus. We find that saturation effects are paramount to accurately describe experimental data in p+Pb collisions from the ALICE Collaboration for both forward and backward going J/ψ. The parameters we find for the model of the nucleon structure are consistent with those obtained from fits to diffractive vector meson production in e+p collisions at HERA. In addition, the observables studied here are better suited to distinguish whether size fluctuations or density fluctuations contribute more to the fluctuations of hadron multiplicities. This suggests a strong potential for a combined global analysis of HERA (and future EIC) and LHC data to constrain (sub-)nucleon structure at high energies.

Speaker: Bjoern Schenke (Brookhaven National Lab)

poster_schenke.pdf

14:48 Measurement of heavy-flavor production in the high-mass dimuon spectrum in pp collisions at $\sqrt{s}$=13 TeV with ALICE

Heavy-quark production in nuclear collisions is an important tool to access the properties and evolution of deconfined matter. Corresponding studies on pp collisions serve as a reference process, as well as a test of various aspects of QCD. A detection technique that was little explored until now at LHC energy is the analysis of the high-mass region of the dilepton invariant mass spectrum ($m>m_{J/\Psi}$), where a significant contribution comes from the semileptonic decay of pairs of charm and beauty hadrons.

A preliminary study is performed, where the Monte Carlo event generator PYTHIA8 is used to simulate pp collisions at $\sqrt{s}$=13 TeV, and the mass and transverse momentum spectra of muon pairs from heavy-flavour decays in the rapidity region 2.5<y<4 are obtained, separately for charm and beauty hadrons. This kinematic region corresponds to the coverage of the ALICE muon spectrometer. The goal of this study is a first comparison between the spectrum measured by ALICE in pp collisions at $\sqrt{s}$=13 TeV, where the experiment has collected an integrated luminosity $\mathcal{L}_{int} \sim 25$ pb$^{-1}$, and the PYTHIA8 calculations.

In this poster, I will present the status of this analysis for what concerns the simulation chain and the prospects for the extraction of the heavy-quark cross sections from this study.

Speaker: Michele Pennisi (Universita e INFN Torino (IT))

Michele_Pennisi_QM2022_Poster.pdf

14:00 → 15:00 Poster Session 3 T11_3

14:00 Study of heavy-flavor jet measurements with sPHENIX

Jets including heavy flavor quarks (HF-jets) are mostly produced from initial hard scattering in relativistic heavy ion collisions. Therefore it is a good probe to study the properties of quark gluon plasma produced from heavy ion collisions. Jets initiating from bottom quarks ($b$-jets) can be identified by the characteristic of b-hadrons such as long lifetime and heavy mass. sPHENIX experiment at Relativistic Heavy Ion Collider is designed for precise measurements of $b$-jets with a MAPS based vertex tracker (MVTX), and the first run is expected to start in 2023. An extensive simulation study has been performed to develop and test $b$-jet tagging algorithms such as secondary vertex method and displaced track counting method. In this poster, simulation studies on $b$-jet tagging algorithms and their performance at sPHENIX will be presented.

Speaker: Sanghoon Lim (Pusan National University (KR))

QM22poster_shlim_HFjet_sPHENIX_v2.pdf

14:04 Energy loss and flows of charm and bottom quarks from single electron measurements in Au+Au collisions at PHENIX

Charm and bottom production is a powerful tool to study the properties
of the Quark Gluon Plasma (QGP).Heavy quarks lose their energies via final state interactions in the QGP.The magnitude of the energy losses is expected to depend on their mass.The elliptic flow of charm and bottom also provide a medium coupling of heavy flavor with the QGP.
PHENIX performed the statistical separation of electrons from charm and bottom
decays using the distance of closest approach from the primary vertex with the silicon vertex detector (VTX) covering electrons with $1 The centrality dependence of the $c\rightarrow e$ and $b\rightarrow e$ nuclear modifications and the elliptic flow parameter $v_2$ are measured using a large amount of statistics recorded in the Au+Au run taken in 2014 at $\sqrt{s_{NN}}$=200 GeV.
In this poster, the final results of electrons from charm and bottom decays in
Au+Au collisions are presented and their nuclear modifications and flows are discussed.

Speakers: Takashi Hachiya (Nara Women's University (JP)), for the PHENIX collaboration

QM2022_poster_hachiya.pdf

14:08 Quarkonium production in p+p collisions measured by the STAR experiment

In heavy-ion collisions, quarkonium states are used to study the properties of the quark-gluon plasma. Measurements of quarkonia in p+p collisions serve as important references. However, the production mechanism of quarkonium states in p+p collisions is still not fully understood because it involves both perturbative and non-perturbative QCD processes. Measurements of $J/\psi$ production with jet activity (number of jets in an event) provide important insight into the production mechanism as Color Singlet Model (CSM) and Color Octet Model (COM) give different predictions on the number of jets produced in $J/\psi$ events. In addition, the production mechanism can also be studied by measuring inclusive quarkonium production cross section and differential production within jets.

In this presentation, the transverse momentum and rapidity spectra of $\Upsilon$ states, including $\Upsilon$(2S) and $\Upsilon$(3S) states separately, measured in p+p collisions at $\sqrt{s}=500 \mathrm{GeV}$ will be shown. Furthermore, the first measurements of the $J/\psi$ production with jet activity in p+p collisions at $\sqrt{s}=200\:\mathrm{GeV}$ and $J/\psi$ production in jets at $\sqrt{s}=500\:\mathrm{GeV}$ will be presented. All results will be compared to quarkonium production model calculations.

Speaker: Leszek Kosarzewski (Czech Technical University in Prague)

QM2022_Quarkonium_Poster_LK_2022.4.8_v5.pdf

14:12 Measurements of open-charm hadron production and total charm cross section in Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 200\,GeV by the STAR experiment

Measurements of open-charm hadrons in ultra-relativistic heavy-ion collisions are an important part of the heavy-ion physics program of the STAR experiment. The charm quarks can be used to study the properties of the Quark-Gluon Plasma (QGP) as they are produced predominantly in hard partonic scatterings at the very early stage of heavy-ion collisions which means that they experience the whole evolution of the hot and dense medium. The STAR experiment is capable of topological reconstruction of hadronic decays of the open charm hadrons thanks to the excellent pointing resolution of the Heavy Flavor Tracker.

In this poster, we present the final results on the measurements of D$^0$, D$^\pm$, D$_\mathrm{s}$, and $\Lambda_\mathrm{c}$ in Au+Au collisions at $\sqrt{s_\mathrm{NN}}$ = 200 GeV. The extracted invariant yields of D$^0$ and D$^\pm$ mesons are used to calculate the nuclear modification factor $R_\mathrm{AA}$ which reveals a significant suppression of high-$p_T$ D mesons in central Au+Au collisions. The D$^{\pm}$, D$_\mathrm{s}$, and $\Lambda_\mathrm{c}$ measurements are compared to that of D$^0$ mesons via transverse momentum and centrality dependent yield ratios. These ratios are compared to multiple theoretical models incorporating various charm quark hadronization schemes. The measurement of D$^{\pm}$ concludes the measurements of major ground states of open-charm hadrons in Au+Au collisions by the STAR experiment. This allows, for the first time, to calculate the total charm quark production cross section per nucleon-nucleon collision in Au+Au collisions, which will also be shown.

Speaker: Jan Vaněk (Nuclear Physics Institute, Czech Academy of Sciences)

QM2022_poster_slides_Vanek_final.pdf

14:16 Anisotropic flow of (multi-)strange hadrons and $\phi$ mesons in Au+Au collisions at $\sqrt{s_{NN}}$ = 3 - 19.6 GeV at STAR

In low energy heavy-ion collisions, directed and elliptic flow, $v_1$ and $v_2$, are sensitive to the dynamics at the early stage of the system evolution and equation of state of the medium. The triangular flow $v_{3}$ provides complementary information on the initial geometry fluctuations and transport properties of the medium. The hadronic interaction cross sections of multi-strange hadrons and $\phi$ mesons are expected to be small and their freeze-out temperatures are close to the transition temperature between quark and hadronic matter. Hence, these hadrons may provide information primarily from the early stage of the high energy collisions.

From the measurements based on the first phase of RHIC beam energy scan (BES-I), we observed that $v_{1}$ slopes ($dv_{1}/dy$) at mid-rapidity region for net-proton and net-$\Lambda$ show a minimum value around $\sqrt{s_{NN}}$ = 10 - 20 GeV~\cite{ref3}. The $v_2$ of $\phi$ mesons seems to be lower at $\sqrt{s_{NN}}$ = 7.7 and 11.5 GeV compared to other charged hadrons~\cite{ref4}. In this talk, with the much enhanced statistics from the second phase of RHIC beam energy scan (BES-II) dataset, we present precision measurements of $v_1$, $v_2$, and $v_3$ for (multi-)strange hadrons at $\sqrt{s_{NN}}$ = 3 - 19.6 GeV with both fixed-target and collider modes at STAR. Implications of these measurements on the QCD phase structure at high $\mu_{B}$ region are discussed.

Speaker: Prabhupada Dixit

QM_poster_slide_v7.pdf

14:20 Study of J/$\psi$ elliptic flow in Zr+Zr and Ru+Ru collisions at $\sqrt{s_{_{\mathrm{NN}}}}$ = 200 GeV with the STAR experiment

Quark-gluon plasma (QGP) is an interacting localized assembly of quarks and gluons at thermal and chemical equilibrium at extremely high temperature or density. It is believed that the suppressed J/$\psi$ production in relativistic heavy-ion collisions is one of the important experimental observations for the production of the QGP. However, in order to correctly interpret those results, the hot and cold nuclear effects need to be distinguished. The elliptic flow ($v_{2}$) of the J/$\psi$ mesons is another way to study the properties of QGP. Measurements of J/$\psi$ $v_{2}$ in different collision systems and energies will provide unique and important information.
In this contribution, we will present the progress of the study of J/$\psi$ $v_{2}$ in different transverse momentum and centrality intervals using Zr+Zr and Ru+Ru collisions at $\sqrt{s_{_{\mathrm{NN}}}}$ = 200 GeV with the STAR experiment at RHIC.

Speaker: Yu-Ming Liu

QM2022_poster_yuming_plot_update_ver10.pdf

14:24 Heavy flavor production in heavy ion collisions with JETSCAPE

The dynamics of shower development for a jet traveling through the quark-gluon plasma (QGP) involves a variety of scales, including the mass for heavy flavors in jets. During the high virtuality portion of the jet evolution, the mass of the heavy quark affects longitudinal drag and diffusion, stimulating additional radiation. These emissions partially compensate the reduction in radiation from the dead cone effect. In the lower virtuality part of the shower evolution, when the mass is comparable to the transverse momentum of the parton, scattering and radiation processes off heavy quarks are different than off light quarks. All these factors result in a different shower development for heavy-flavor tagged jets. The QGP evolution is modeled on an event by event basis using the JETSCAPE Framework. Energy-momentum exchange with the medium, essential for the study of jet modification, proceeds using a weak coupling recoil approach. We present a multi-stage calculation that explores the importance of differences between various heavy quark energy-loss mechanisms. Those differences have been explored using leading hadron and open heavy flavor observables.

Speaker: Wenkai Fan

Heavy flavor production in heavy ion collisions with JETSCAPE.pdf

Heavy flavor production in heavy ion collisions with JETSCAPE.pptx

14:28 Simulation study of bottomonium suppression measurement by the sPHENIX experiment.

Measurements of bottomonium states in heavy-ion collisions provide a
powerful tool to study both initial-state effects on heavy-quark production
and final-state interactions between heavy quarks and the hot and dense
nuclear matter created in relativistic heavy ion collisions.

The sPHENIX experiment, which will start taking data in early 2023, plans
to measure the production of bottomonium states Υ(nS) in Pb+Pb and
p+p collisions in di-electron channel.
In this poster we describe the results of a full Monte-Carlo study of Upsilon
measurements by the sPHENIX experiment with the emphasis on estimation of
expected accuracy of nuclear modification factor ($R_{AA}$) measurement.
Details of the study as well as plans for the nearest future are presented.

Speaker: Alexandre Lebedev (Iowa State University (US))

Lebedev_QM22_sPHENIX.pdf

14:32 Heavy Quark Potential in QGP: Deep Neural Network meets Lattice QCD

Bottomonium states are key probes for experimental studies of the quark-gluon plasma (QGP) created in high-energy nuclear collisions. Theoretical models of bottomonium productions in high-energy nuclear collisions rely on the in-medium interactions between the bottom and antibottom quarks. The latter can be characterized by the temperature ($T$) dependent potential, with real ($V_R(T,r)$) and imaginary ($V_I(T,r)$) parts, as a function of the spatial separation ($r$). Recently, the masses and thermal widths of up to $3S$ and $2P$ bottomonium states in QGP were calculated using lattice quantum chromodynamics (LQCD) [Phys.Lett.B 800, 135119 (2020)]. We find that the HTL complex potential is disfavored by the lattice result, which motives us to employ a model-independent parameterization --- the Deep Neural Network (DNN) --- to represent the Bottomonium potential, extract the potential allowed by the lattice data. Starting from these LQCD results and through a novel application of DNN, here, we obtain $V_R(T,r)$ and $V_I(T,r)$ in a model-independent fashion. The temperature dependence of $V_R(T,r)$ was found to be very mild between $T\approx0-330$~MeV. For $T=150-330$~MeV, $V_I(T,r)$ shows rapid increase with $T$ and $r$, which is much larger than the perturbation theory based expectations.

Ref: arXiv:2105.07862[hep-ph]

Speakers: Dr Shuzhe SHI (Stony Brook University), Kai Zhou (FIAS, Goethe-University Frankfurt am Main)

Complex Potential.key

Complex Potential.pdf

14:36 Using Jet Substructure to probe Heavy-Flavor Energy-Loss

The dynamics of shower development for a jet traveling through the quark-gluon
plasma (QGP) involves a variety of scales, including the mass for heavy flavors
in jets. During the high virtuality portion of the jet evolution, the mass of
the heavy quark affects longitudinal drag and diffusion, stimulating additional
radiation. These emissions partially compensate the reduction in radiation from
the dead cone effect. In the lower virtuality part of the shower evolution, when
the mass is comparable to the transverse momentum of the parton, scattering
and radiation processes off heavy quarks are different than off light quarks. All
these factors result in a different shower development for heavy-flavor tagged
jets vs. light-flavor jets.
In this work, we present a multi-stage calculation using a weak coupling recoil
approach to calculate jet and jet substructure observables to explore differences
between various heavy quark energy-loss mechanisms. Our work extends and
compares to previous studies that have used leading hadron and open heavy
flavor observables.
1

Speaker: Wenkai Fan

Using Jet Substructure to probe Heavy-Flavor Energy-Loss.pdf

14:40 Measurement of prompt D$^0$, $\Lambda_c^+$, and $\Sigma_c^{0,++}$(2455) production in proton–proton collisions at $\sqrt{s}$ = 13 TeV with ALICE

The measurement of relative production rates of different charm hadrons allows us to study hadronization mechanisms of charm quarks and to investigate different hadronization models. Various hypotheses are inspected like recombination, colour reconnection and decay from unknown excited states.

The results discussed in this contribution provide the first $\Sigma_{c}^{0,++}$ production measurement in hadronic collisions and show that the hadron production is significantly larger than in e$^+$e$^-$ collisions, indicating that baryon enhancement in hadronic collisions extends also to the $\Sigma_{c}$.

The measurements of the $p_\mathrm{T}$-differential cross section of prompt D$^0$, $\Lambda_c^+$, and $\Sigma_c^{0,++}$(2455) in pp collisions at $\sqrt{s}$ = 13 TeV performed by the ALICE experiment at the LHC at midrapidity will be shown. The baryon-to-meson ratios $\Lambda_c^+/$D$^0$ and $\Sigma_c^{0,+,++}/$D$^0$ as well as the fraction of $\Lambda_c^+$ feed-down from $\Sigma_c^{0,+,++}$ will be discussed and compared to expectations from theoretical models including: the Statistical Hadronisation Model (SHM) combined with Relativistic Quark Model (RQM), the Catania model, the quark (re-)combination mechanism (QCM) model, and various tunes of PYTHIA8.

Speaker: Marco Giacalone (Universita e INFN, Bologna (IT))

Quark Matter.pdf

Quark Matter.ppsx

14:44 Hydrodynamic approach to heavy-quark diffusion in the quark-gluon plasma

Exciting experimental results on the flow of charmonia and bottomonia with an unprecedented level of precision pose the important physics question about the possible heavy-quark thermalization in the quark-gluon plasma (QGP). In this work, a new hydrodynamic approach to the transport of heavy quarks in the QGP is presented. We exploit the conservation of the number of heavy quark-antiquark pairs within the evolution of the QGP to construct causal second-order hydrodynamic equations of motion. The hydrodynamic transport coefficients associated with the heavy-quark diffusion current are then compared with the momentum-diffusion coefficients obtained in transport theory (Fokker-Planck equation). We provide new insights concerning the level of local thermalization of charm and beauty quarks inside the expanding QGP by investigating the relation between the two approaches. Our results show that a fluid dynamic description of diffusion is feasible for charm quarks. In particular, in Bjorken flow the hydrodynamization time of charm quarks is in general short compared to the typical expansion time of the QGP, justifying a fluid description of charm diffusion. Analogous considerations for beauty quarks are presented.
Based on: F. Capellino, A. Beraudo, A. Dubla, S. Floerchinger, S. Masciocchi, J. M. Pawlowski, I. Selyuzhenkov, in preparation. This work is funded via the DFG ISOQUANT Collaborative Research Center (SFB 1225).

Speaker: Federica Capellino (Ruprecht Karls Universitaet Heidelberg (DE))

Hydrodynamic approach to heavy-quark diffusion in the quark-gluon plasma.pdf

14:48 Searching for novel charmed hadrons in relativistic heavy-ion collisions at LHC

The deconfined quark-gluon plasma (QGP) created in relativistic heavy-ion collisions is not only a perfect fluid with very small $\eta/s$ but also a most "charming" system with hundreds of charm quarks. Meanwhile, it is widely accepted that the quark hadronization mechanism changes with the appearance of QGP. The production of charmed hadrons differs significantly in $A$-$A$ collisions from that of $p$-$p$ and $e^+$-$e^-$ collisions. The yield of hadrons(including exotic hadrons like tetraquarks, pentaquarks, etc.) with multiple charm quarks would be enhanced through the charm coalescence process in the "charming" QGP medium.
In this talk, we will present our recent studies on the generation of novel charmed hadrons, such as $B_c$, $X(3872)$, $T_{cc}$, and $X_{cc\bar c\bar c}(6900)$ in relativistic heavy-ion collisions at LHC. We study the static properties of those charmed hadrons in vacuum and finite temperature by solving the two/four-body Schroedinger equations. Their yields in heavy ion collisions are investigated dynamically through the transport and coalescence hadronization model. The results show the yield of $B_c$, $X(3872)$, $T_{cc}$, and $X_{cc\bar c\bar c}(6900)$ are order of 1-3 magnitude increased in heavy-ion collisions. This provides a new avenue for scientists to observe/discover those charmed hadrons in the experiment.

Speaker: Jiaxing Zhao (Tsinghua University)

Jxzhao_QM2022_T11-3.pdf

14:00 → 15:00 Poster Session 3 T11_4

14:00 Heavy flavour hadron production in a coalescence plus fragmentation approach from AA to pp

Measurements of heavy baryon production in $pp$, $pA$ and $AA$ collisions from RHIC to top LHC energies have recently attracted more and more attention, currently representing a challenge for the heavy-quark hadronization theoretical understanding.
The $\Lambda_c/D^0$ ratio observed in $AA$ collision at RHIC and LHC energies has a value of the order of the unity.
Recent experimental measurements in $pp$ collisions at both $\sqrt{s}=5.02 \,\rm TeV$ $\sqrt{s}=13 \,\rm TeV$ have shown ratios for charm baryons $\Lambda_c$, $\Xi_c^0$ and $\Omega_c^0$ respect to $D^0$ meson larger than that measured and expected in $e^+e^-$, $ep$ collisions.
We study the hadronization after the propagation of charm quarks in the quark-gluon plasma (QGP). The propagation is described by means of a relativistic Boltzmann transport approach where the non-perturbative interaction between heavy quarks and light quarks is described by means of a quasi-particle approach.
We present a coalescence plus fragmentation model for the hadronization and the results obtained in $AA$ collisions for $D^0$, $D_s$, $\Lambda_c$ spectra and the related baryon to meson ratios at RHIC and LHC.
We found a large $\Lambda_c$ production resulting in a baryon over meson ratio of order O(1).
We propose the $v_2$ of charmed baryons as a possible way to have a deeper insight into the hadronization mechanism.
We have furthermore extended this approach to study the production of hadrons containing multiple charm quark, i.e. $\Xi_{cc}$, $\Omega_{cc}$ and $\Omega_{ccc}$, and bottom quarks.
We present, also, results for the charmed hadron production in $pp$ collisions at top LHC energies (5 TeV, 13 TeV) assuming the formation of an hot QCD matter at finite temperature for these systems.
We calculate the heavy baryon/meson ratio and the $p_T$ spectra of charmed hadrons with and without strangeness content: $D^{0}$, $D_{s}$, $\Lambda_{c}^{+}$, $\Sigma_{c}$ and the recently measured $\Xi_c$ baryon, finding an enhancement in comparison with the ratio observed for $e^+e^-$, $ep$ collisions; moreover with this approach we predict also a significant production of $\Omega_c$ respect to $D^0$ such that $\Omega_c/D^0 \sim 0.15$.

[1] V. Minissale, S. Plumari and V. Greco, Physics Letters B 821 (2021) 136622.
[2] S. Plumari, V. Minissale, S.K. Das, G. Coci and V. Greco, Eur.Phys.J. C 78 (2018) no.4, 348

Speaker: Vincenzo Minissale (University of Catania - INFN/LNS)

Minissale_poster_QM2022.pdf

14:04 Heavy quark dynamics in a strongly magnetized quark-gluon plasma

We have explored [1] the heavy quark transport coefficients in a quark- gluon plasma under the presence of a strong external magnetic field, within the Lowest Landau Level (LLL) approximation. In particular, we apply the Hard Thermal Loop (HTL) technique for the resummed effective gluon propagator, generalized for a hot and magnetized medium. Using the effective HTL gluon propagator and the LLL quark propagator we analytically derive the full results for the longitudinal and transverse momentum diffusion coefficients as well as the energy losses for charm and bottom quarks beyond the static limit. We also show numerical results for these coefficients in two special cases where the heavy quark is moving either parallel or perpendicular to the external magnetic field. From our most general beyond the static limit result, we have successfully traced back the previously explored [2] static limit expressions for the heavy quark transport coefficients in a strongly magnetized medium.

[1] A. Bandyopadhyay, J. Liao and H. Xing, [arXiv : 2105.02167 [hep-ph]]
[2] K. Fukushima, K. Hattori, H. U. Yee and Y. Yin, Phys. Rev. D 93, (2016)

Speaker: Aritra Bandyopadhyay

14:08 Heavy quarks in the evolving Glasma: diffusion, 2-particle correlations and comparison with Langevin dynamics

Heavy quarks, charm and beauty, form well before light quarks in high energy nuclear collisions. Therefore, they can probe the early, gluon rich and out-of-equilibrium stage, namely the evolving Glasma. The diffusion of heavy quarks in this system can be analyzed by coupling the Classical Yang-Mills equations for the Glasma to the relativistic kinetic equations (Wong equations) for the heavy quarks. Within this framework, we study in detail the diffusion of heavy quarks in the early stage of proton-nucleus and nucleus-nucleus collisions.
Firstly, we discuss transverse and longitudinal momentum broadening, emphasizing the impact of this on the nuclear modification factor and on the estimates of the diffusion coefficients of the heavy quarks. Then, we analyze the 2-particle correlations developed by heavy quarks in the Glasma and discuss their potential impact on D-Dbar correlations recently measured at the LHC. Finally, we compare the evolution in the Glasma with that in a gluon plasma, described by Langevin equations with transport coefficients borrowed from quasi-particle models and tuned to reproduce the nuclear modification factor of heavy mesons.

A. Ipp, D. I. Muller and D. Schuh,
Jet momentum broadening in the pre-equilibrium Glasma,
Phys. Lett. B 810, 135810 (2020)
doi:10.1016/j.physletb.2020.135810
[arXiv:2009.14206 [hep-ph]].

Y. Sun, G. Coci, S. K. Das, S. Plumari, M. Ruggieri and V. Greco,
Impact of Glasma on heavy quark observables in nucleus-nucleus collisions at LHC,
Phys. Lett. B 798, 134933 (2019)
doi:10.1016/j.physletb.2019.134933
[arXiv:1902.06254 [nucl-th]].

D. Avramescu, V. Baran, V. Greco, D. Muller and M. Ruggieri,
Heavy quarks in the evolving Glasma: diffusion, 2-particle correlations and comparison with Langevin dynamics, in preparation.

Speaker: Dana Avramescu (University of Bucharest)

da_qm22.pdf

14:12 Study of $J/\psi$ production with jet activity in $pp$ collisions at $\sqrt{s}$ = 200 GeV with the STAR experiment

The production mechanism of quarkonia is an important topic to investigate since it involves both perturbative and non-perturbative processes. Quarkonium production from Color Singlet Model and Color Octet Mechanism should result in different jet activities (the number of jets per event) due to different number of emitted hard partons. Therefore, studies associated with jets can further help to differentiate between the different quarkonium production mechanisms.

In this poster, we will present the first results from RHIC of the $J/\psi$ production cross section as a function of jet activity using the p+p collision data at $\sqrt{s}$ = 200 GeV collected by the STAR experiment in 2015. These results will be compared to different production model calculations.

Speaker: Hao Huang

Hao_Huang_QM2022_Poster_v8.pdf

14:16 Heavy-flavour meson and baryon production in high-energy nucleus-nucleus collisions

Recent experimental measurements display an enhanced production of charmed baryons in high-energy nucleus-nucleus collisions. Quite surprisingly the same is found in proton-proton collisions, in which the relative yields of charmed baryons do not agree with the expectations based on e+e- collisions and with the predictions of those QCD event generators in which the hadronization stage is tuned to reproduce this more elementary situation.
Medium modification of hadronization, via some mechanism of recombination with light thermal partons, has been known for long to be an essential ingredient to implement in transport calculations in order to describe experimental data of heavy-flavour production in nucleus-nucleus collisions. This is true both for the momentum and angular distributions of the final charmed/beauty hadrons and for their relative yields.
In this talk I will present the main features of a novel hadronization scheme we developed and implemented in our POWLANG transport setup, showing also our first results for the heavy-flavour particle ratios and flow coefficients in nucleus-nucleus collisions, in satisfactory agreement with recent experimental data. The model is based on the formation of color-singlet clusters via recombination of a charm quark with a light thermal antiquark or diquark (assumed to be present in the medium around the critical temperature) from the same fluid cell. If the cluster is sufficiently light it undergoes a two-body decay, if its invariant mass is larger it is treated as a Lund string and accordingly fragmented. The model has some nice features: modelling hadronization as a 2->N process allows exact four-momentum conservation; involving particles from the same fluid-cell it contains by construction space-momentum correlations; recombination with diquarks allows one to describe charmed-baryon production; at large pT it naturally approaches standard vacuum-like fragmentation.
A consistent modelling of the proton-proton reference, with the assumption of the formation of a small short-lived QGP droplet, in medium heavy-quark transport and hadronization is currently under development and preliminary results will be shown.

Speaker: Andrea Beraudo (INFN, sezione di Torino (IT))

14:20 Anisotropic flow of (multi-)strange hadrons and $\phi$ mesons in Au+Au collisions at $\sqrt{s_{NN}}$ = 3 - 19.6 GeV from STAR

Directed and elliptic flow, $v_1$ and $v_2$, are sensitive to dynamics of heavy-ion collisions at the early stage of the system evolution and equation of state of the medium. The hadronic interaction cross sections of multi-strange hadrons and $\phi$ mesons are expected to be small and their freeze-out temperatures are close to the quark-hadron transition temperature. Hence, these hadrons may provide information primarily from the early stage of the high energy collisions and are important for the study of QCD phase diagram at RHIC.

In the first phase of RHIC beam energy scan (BES-I), we observed that $v_{1}$ slopes ($dv_{1}/dy$) at mid-rapidity region for net-proton and net-$\Lambda$ show a minimum value when the collision energy is around $\sqrt{s_{NN}}$ = 10 - 20 GeV [1]. The $v_2$ of $\phi$ mesons seems lower than those of other particles at $\sqrt{s_{NN}}$ = 7.7 and 11.5 GeV [2]. In this poster, with large statistics from the STAR fixed-target (FXT) and second phase of RHIC beam energy scan (BES-II), we will present precise measurements on $v_1$ and $v_2$ of $K^\pm$, $K_S^0$, $\Lambda$, $\bar{\Lambda}$, $\Xi$, $\bar{\Xi}^{+}$, $\Omega$, $\bar{\Omega}^{+}$, and $\phi$ mesons in Au+Au collisions at $\sqrt{s_{NN}}$ = 3 - 19.6 GeV from STAR.

[1] L. Adamczyk $\textit{et al.}$, Phys. Rev. Lett. $\textbf{120}$, 062301 (2018).
[2] L. Adamczyk $\textit{et al.}$, Phys. Rev. Lett. $\textbf{110}$, 142301 (2013).

Speaker: Ding Chen

0408_2022_dchen_QM2022_v9.pdf

14:24 Azimuthal anisotropy measurement of (multi)strange hadrons and $\phi$ mesons in Au+Au collisions at $\sqrt{s_{NN}}$ = 3 - 19.6 GeV in BES-II at STAR

Azimuthal anisotropies are sensitive observables to the initial stage of heavy-ion collisions. Strange and multi-strange hadrons are suitable candidates to measure these flow coefficients due to their small hadronic interaction cross section and early freezeout from the medium. Earlier in beam energy scan phase-I (BES-I), STAR collaboration measured the rapidity-odd directed flow for $\Lambda$, $\bar{\Lambda}$, $K^{\pm}$, $K_{S}^{0}$, and $\phi$ at $\sqrt{s_{NN}}$ = 7.7 - 200 GeV. The $v_{1}$ slope ($dv/dy$) at mid-rapidity shows a minimum value for the net-proton and net-$\Lambda$ when the collision energy is around 10-20 GeV which may be related to a signature of the first-order phase transition in the QCD phase diagram. It has been observed that $v_{2}$ of $\phi$ mesons shows quite different trend at $\sqrt{s_{NN}}$ = 7.7 and 11.5 GeV compared to other charged hadrons. The NCQ scaling also fails at these low energies for $\phi$ mesons and other anti-baryons which may indicate different hadron formation mechanism at these low energies. Due to less statistics, it was difficult to make any quantitative conclusion. %High statistics measurements are required to confirm the $v_{2}$ trend of $\phi$ mesons as well as validity of the NCQ scaling at low energies.

The STAR experiment has finished the data taking of BES-II program in 2021 with improved detector conditions. In this poster, we will present the high statistics measurements of $v_{1}(y)$ and $v_{2}(p_{T})$ for $K_{S}^{0}$, $\Lambda$, $\bar{\Lambda}$, $\Xi^{-}$, $\bar{\Xi}^{+}$, $\phi$, $\Omega^{-}$, and $\bar{\Omega}^{+}$ at $\sqrt{s_{NN}}$ = 3, 7.7, 14.6, and 19.6 GeV. The centrality dependence of $v_{2}$ and NCQ scaling will be shown for all the particles.

Speaker: Li-Ke Liu

QM2022_poster807_Like.pdf

14:28 Phenomenological aspects of colliding and radiating charm quark in an expanding quark-gluon plasma

Heavy quarks, namely charm and bottom quarks, serve as efficient probes to characterize the properties of the quark-gluon plasma (QGP) created in the relativistic heavy-ion collisions. The QGP evolution is modeled using relativistic viscous 3+1 D hydrodynamics approach MUSIC, initialized with a central Pb-Pb collision event using IP-GLASMA. Measured observables associated with charm quark are explored within the Langevin approach by treating the charm quark transport coefficients as the input parameters for the LHC and RHIC energies. To that end, drag and diffusion coefficients due to the collisional (elastic scattering process with the medium constituents) and radiative processes (soft gluon emission) of charm quark in the expanding QGP medium are analyzed. The effects of viscous corrections to the transport coefficients and the gluon emission process of the charm quark on the nuclear suppression factor are also studied. This work is the first up-to-date calculation of heavy quark experimental signals using the latest developments in the relativistic hydrodynamical simulation of heavy-ion collisions that will have a significant role in understanding different observables with the RHIC and LHC data.

Speaker: Dr Manu Kurian (Indian Institute of Technology Gandhinagar)

QM_2022.pdf

14:32 Strange and charm quark production in hot QCD

We investigate the time evolution of strange and charm quark number densities utilizing the rate equations in the quasiparticle approach. The deconfined matter then consists of the dynamical quarks and gluons dressed by the effective temperature-dependent masses. The temperature dependence is specified by a running coupling deduced from lattice QCD thermodynamics. For the evolution of the QGP in 2+1 dimensions, we employ the results of hydrodynamic simulations, which incorporate the shear viscosity computed in the quasiparticle model. We study the heavy quark production in hot QCD medium with $N_f=2+1(+1)$ with the charm quarks contributing to the equation of state.

Speaker: Valeriya Mykhaylova (University of Wrocław)

QM22_Mykhaylova.pdf

14:36 Measurement of $\Xi_{c}^{0}$ in pp collisions at 13 TeV as a function of multiplicity and in p–Pb collisions at 5.02 TeV with ALICE

Recent results of charmed baryon production in pp collisions showed significant enhancement of baryon-to-meson ratio compared with the predictions from $e^{+}e^{-}$ collisions due to the modification of the charm fragmentation fractions and possible coalescence mechanism at play. Therefore, the measurements of charmed baryon production are crucial to investigate the hadronisation mechanism of charm quarks.

In pp collisions, further study on the multiplicity dependence of the baryon-to-meson yield ratios can provide information on how the charm hadronisation process evolves. Measurements in protonnucleus collisions are important to separate the cold nuclear matter effect from the effects associated with the formation of quark-gluon plasma.

In this study, we report the analysis status on the $\Xi_{c}^{0}$ measurements at midrapidity via the semileptonic decay channel $\Xi_{c}^{0}$ → $\Xi^{-} e^{ +} \nu_{ e}$ (and charge conjugates), especially the multiplicity dependence in pp collisions at $\sqrt{s}=13~\mathrm{TeV}$ and $\Xi_{c}^{0}$ production in p–Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV. In addition, the recent results of $\Xi_{c}^{0}$ in pp collisions at $\sqrt{s}=13~\mathrm{TeV}$ will be shown.

Speakers: Chong Kim (Pusan National University (KR)), Jeongsu Bok (Inha University (KR))

QM22Poster_Session3_T11_4_ALICE_Xic0_JeongsuBok_ChongKim.pdf

14:40 Memory effects in high energy nuclear collisions

Stochastic processes with memory are characterized by noises that possess correlations at different times;
namely, the stochastic terms in the differential equations at a time t have memory of the noise at previous times.
Heavy ion collisions are an interesting framework in which processes with memory take place,
in particular when one considers the very early, out-of-equilibrium stage that is dominated by the intense fields of the evolving Glasma.
In this talk, we discuss the diffusion of heavy quarks in the early stages of heavy ion collisions, in which the stochastic term is furnished by
the strong (and random) gluon fields that develop in the interaction region of the two colliding objects.
Then we turn to quantitative estimates of the effects of the diffusion in the early stage on the nuclear modification factor, particle correlations
and elliptic flow of heavy mesons. Finally, we discuss the applicability of generalized Langevin equations to the diffusion of heavy probes in the early stages.

References

Pooja, S.~K.~Das, L.~Oliva and M.~Ruggieri,
Heavy quarks in the early stage of high energy nuclear collisions at RHIC and LHC: Brownian motion versus diffusion in the evolving Glasma,
[arXiv:2110.14610 [hep-ph]].

J.~H.~Liu, S.~K.~Das, V.~Greco and M.~Ruggieri,
Ballistic diffusion of heavy quarks in the early stage of relativistic heavy ion collisions at RHIC and the LHC,
Phys. Rev. D \textbf{103}, no.3, 034029 (2021)
doi:10.1103/PhysRevD.103.034029
[arXiv:2011.05818 [hep-ph]].

M.~Y.~Jamal, S.~K.~Das and M.~Ruggieri,
Energy Loss Versus Energy Gain of Heavy Quarks in a Hot Medium,
Phys. Rev. D \textbf{103}, no.5, 054030 (2021)
doi:10.1103/PhysRevD.103.054030
[arXiv:2009.00561 [nucl-th]].

J.~H.~Liu, S.~Plumari, S.~K.~Das, V.~Greco and M.~Ruggieri,
Diffusion of heavy quarks in the early stage of high-energy nuclear collisions at energies available at the BNL Relativistic Heavy Ion Collider and at the CERN Large Hadron Collider,
Phys. Rev. C \textbf{102}, no.4, 044902 (2020)
doi:10.1103/PhysRevC.102.044902
[arXiv:1911.02480 [nucl-th]].

Y.~Sun, G.~Coci, S.~K.~Das, S.~Plumari, M.~Ruggieri and V.~Greco,
Impact of Glasma on heavy quark observables in nucleus-nucleus collisions at LHC,
Phys. Lett. B \textbf{798}, 134933 (2019)
doi:10.1016/j.physletb.2019.134933
[arXiv:1902.06254 [nucl-th]].

M.~Ruggieri and S.~K.~Das,
Cathode tube effect: Heavy quarks probing the glasma in p -Pb collisions,
Phys. Rev. D \textbf{98}, no.9, 094024 (2018)
doi:10.1103/PhysRevD.98.094024
[arXiv:1805.09617 [nucl-th]].

Speaker: Prof. Marco Ruggieri (Labzhou University)

14:44 Study of multiplicity dependent $J/\psi$ and $\psi(2S)$ production in $p$+$p$ collisions with PHENIX

The PHENIX experiment at RHIC has a special ability to detect muons at the region $1.2<|y|<2.2$ from heavy quarks which are studied extensively to understand their production and modification in high energy hadron-hadron collisions. Quarkonia states like $J/\psi$ and $\psi(2S)$ of different binding energies are expected to have their yields modified differently by the medium or comoving particles. The $\psi(2S)$ is significantly more suppressed than $J/\psi$ in heavy-ion collisions by color screening effect. Quarkonia production in small collision systems like $p$+$A$ collisions is also modified due to the initial state and final state effects, and a relative modification between $J/\psi$ and $\psi(2S)$ can provide important information on final state effects. We have been studied the multiplicity dependence of the production of $J/\psi$ and $\psi(2S)$ in $p$+$p$ collisions at PHENIX to analyze the behavior of the potentially smallest QGP (collision system). In this poster, we will present the status of this study along with recent measurements of $J/\psi$ and $\psi(2S)$ in $p$+$p$ collisions at $\sqrt{s_{NN}}=200$ GeV with other experiments and theoretical models.

Speaker: Jongho Oh (Pusan National University (KR))

QM2022poster_Jongho_Oh.pdf

14:48 Exploring the high baryon-density regime of the QCD phase diagram within a novel hybrid approach

A novel hybrid approach coupling the hadronic transport approach SMASH to the 3+1D viscous hydrodynamics code vHLLE is introduced. The SMASH-vHLLE-hybrid is suitable to describe heavy-ion collisions ranging from $\sqrt{s}_\mathrm{NN}$ = 4.3 GeV - 5.02 TeV and is publicly available on Github. This talk focuses on collisions towards the high baryon-density regime of the QCD phase diagram, where the first order phase transition and critical end point are expected. Experimentally, this region of the phase diagram is studied within the NA61/SHINE experiment at CERN, the recently conducted BESII program at RHIC and the future FAIR and NICA facilities. After a thorough validation, the SMASH-vHLLE-hybrid is applied to study particle production and collective flow over a large range of beam energies. It is demonstrated that hadron dN/dy and m$_\mathrm{T}$ spectra are in good agreement with experimental measurements. In particular, it is found that the SMASH-vHLLE-hybrid is capable of properly capturing the baryon stopping dynamics in collisions at finite baryon densities. The transition from a Gaussian net baryon distribution to a double-hump structure as a function of rapidity can be reproduced. The agreement with experimental data for multiplicity, mean p$_\mathrm{T}$ excitation functions and flow is significantly improved as compared to a pure hadronic transport evolution.
This work constitutes a first step in systematically studying heavy-ion collisions at finite baryon densities. Next, the SMASH-vHLLE-hybrid can be applied with different equations of state -with and without first order phase transition- to study the implications for final state observables, particularly focusing on those sensitive to a phase transition.

References:
- A. Schäfer, I. Karpenko, H. Elfner: arXiv: 2109.08578
- A. Schäfer, I. Karpenko, X.-Y. Wu, J. Hammelmann, H. Elfner: "Particle production in a hybrid approach for a beam energy scan of Au+Au/Pb+Pb collisions between $\sqrt{s}_\mathrm{NN}$ = 4.3 GeV and $\sqrt{s}_\mathrm{NN}$ = 200.0 GeV", in preparation
- Github: https://github.com/smash-transport/smash-vhlle-hybrid

Speaker: Anna Schäfer (Frankfurt Institute for Advanced Studies (FIAS))

QM_Poster_2022_Anna_Schaefer.pdf

14:52 Extracting the dead cone effect through heavy flavor data

The upcoming high-luminosity measurements at RHIC and LHC will generate heavy flavor data with unprecedented precision. How to utilize the high-$p_\perp$ heavy flavor data to analyze the interaction mechanisms in the quark-gluon plasma? For this, we employ our recently developed DREENA framework based on our dynamical energy loss formalism. We will propose: i) How to disentangle the relevance of different energy loss mechanisms (i.e., radiative and collisional energy losses) at the same dataset. ii) Novel observables sensitive to these different mechanisms to be tested by future high-precision experiments. iii) Demonstrate, analytically and numerically, that the mass hierarchy/dead cone effect in energy losses can be readily extracted through these observables.

Speaker: Bojana Ilic (Blagojevic) (Institute of Physics Belgrade)

QM22BojanaIlic.pdf

14:00 → 15:00 Poster Session 3 T11_5

14:00 $\Lambda_{c}^{+}$ production in 5.02 TeV pp and PbPb collisions with CMS

In heavy-ion collisions, charm hadron production can occur via coalescence, where charm quarks combine with the surrounding light quarks in the QGP. The relative coalescence contribution is expected to be more significant for hadrons with a larger number of constituent quarks. Such an effect will contribute to the modification of the baryon-to-meson ratio in heavy-ion collisions, compared to pp collision. Therefore, measurements of $\Lambda_{c}^{+}$ production in PbPb and pp collisions can provide important input to the understanding of the coalescence mechanism for charm quark. The high luminosity datasets collected by the CMS detector have been used to measure $\Lambda_{c}^{+}$ production via $\Lambda_{c}^{+} \to p^{+} K^{-} \pi^{+}$. Results of the ratios of $\Lambda_{c}^{+}$ over $D^{0}$ yields in pp and PbPb collisions will be shown. The nuclear modification factors of $\Lambda_{c}^{+}$ will also be presented.

Speaker: Soumik Chandra (Purdue University (US))

Poster for QM2022 final update.pdf

Poster for QM2022 final update.pdf

14:04 Signature of early freeze-out of strangeness in relativistic heavy ion collisions

Freeze-out scenarios with separate freeze-out hypersurfaces for strange and non strange hadrons have been shown to successfully resolve the proton anomaly at the LHC and further improve the description of hadron yields across beam energy. These studies suggest that data favors an early freeze-out of strangeness. Such studies have been so far restricted within the framework of the hadron resonance gas thermal models to describe mid rapidity hadron yields. We implement the flavor dependent freeze-out scenarios within a relativistic viscous hydrodynamics framework by performing separate Cooper-Frye freeze-out of the strange and non strange hadrons. Our study suggests such flavor differential freeze-out scenarios have unique signature on the phase space dependence of produced particles. In particular elliptic flow of pion and spectra ratio of lambda to proton are most sensitive to such freeze-out systematics.

Speaker: Mr Tribhuban Parida (IISER Berhampur)

QM2022.pdf

14:08 Heavy Flavor Prospects at sPHENIX

In 2023, the sPHENIX experiment will begin collecting data which will include the largest recorded sample of b-hadron decays from Heavy Ion collisions at RHIC. This sample will allow for precision charm and beauty studies, part in thanks to the excellent vertexing of the MVTX detector, the timing of the INTT, and precision of the TPC along with the calorimetry system. The sPHENIX collaboration has adapted and developed several tools to complement the detector system and we have undertaken realistic data simulations to understand and refine these tools. These simulations have demonstrated that the collaboration can run automated heavy flavor reconstruction at the offline stage, storing heavy flavor candidates in containers which will allow for rapid and consistent analyses when data taking commences. The collaboration is also developing AI-assisted smart firmware, capable of heavy flavor selections during online data-taking which will improve the signal-to-background ratio of heavy flavor events.

Speaker: Cameron Dean (Los Alamos National Laboratory (US))

HF_at_sPHENIX_C_Dean_QM22_v3.pdf

14:12 Observation of top-quark pair production in proton-lead collisions in ATLAS

Top-quarks, tau leptons, and Higgs boson are the only elementary particles that have not been observed in heavy-ion collisions in the ATLAS detector yet. In particular top quarks, the heaviest elementary particles carrying colour charges, have been argued to be attractive candidates for probing the quark-gluon plasma produced in heavy-ion collisions. In proton-lead collisions, top-quark production is expected to be sensitive to nuclear modifications of parton distribution functions (PDF) at high Bjoerken-x values which are hard to access experimentally using other probes available so far. In 2016 the ATLAS experiment collected proton-lead collisions at centre-of-mass energy of 8.16 TeV per nucleon pair. The high integrated luminosity of the sample amounting to 164 nb-1 allows for top-quark pair production measurement for the first time in this data set with ATLAS. In this poster, we discuss the inclusive cross-section measurement for the top-quark pairs production using dilepton and lepton+jet decay modes with electrons and muons in ATLAS. The measurement will be compared to the NNLO predictions for top-quark production using various PDF sets.

Speaker: Santu Mondal (Czech Technical University in Prague (CZ))

14:16 Fragmentation functions of identified charmed mesons

We present the progress of reconstructing the fragmentation functions of the charmed mesons, X(3872), $\psi(2S)$ and $\Upsilon$ within reconstructed jets. The charmed mesons were measured within reconstructed anti-k$_{T}$ jets with R=0.5 in the $p_{T}$ range of 5 to 40GeV. The data stem from pp collisions at 13 TeV measured by the LHCb detector. The z$_{T}$ distributions of the mesons are reconstructed and compared to each other and to simulations. Since these mesons have very different quark contents, differences between their fragmentation might give insight into the underlying mechanisms of hadronization as well as the production mechanisms in the hard process in which they could be created.

Speaker: Sara Sellam

Poster_QM2022_sara_sellam.pdf

14:20 Studies on charm-strange baryon $\Xi_c^+$ in 8.16TeV pPb collisions with LHCb

The $\Xi_c^+$ baryon is an open charm state comprised of an up, strange, and charm quark. For its peculiar composition with the presence of the strange quark, studies of baryon-to-baryon ratio of $\Xi_c^+$ to $\Lambda_c^+$ can provide valuable information on charm hadronization mechanisms, and possibly observe strangeness enhancement in small systems. We present the first study of $\Xi_c^+$/$\Lambda^+_c$ ratio in proton lead and lead proton collisions at the $\sqrt{s} = 8.16$ TeV with the LHCb experiment. The baryons are reconstructed in their decay with a proton, a kaon, and a pion in about 30 $nb^{-1}$ of data. The results will be compared to existing measurements in other collision systems and at different energies, and to recent theoretical predictions.

Speaker: Roman Litvinov (Universita e INFN, Cagliari (IT))

poster_QM.pdf

14:24 Prompt $\Lambda^+_c$/$D^0$ ratio in peripheral PbPb collisions at 5.02 TeV by LHCb

Coalescence hadronization in QGP would enhance $\Lambda^+_c$/$D^0$ at intermediate $p_T$ and are supposed to occur in PbPb collisions.
The charmed baryon to meson ratio, $\Lambda^+_c$/$D^0$ ratio is sensitive to hadronization, can provide important information on the charm hadronization process and formation of QGP.
Prompt $\Lambda^+_c$/$D^0$ ratio are measured in peripheral PbPb collisions at $\sqrt{s_{NN}}=5.02$ TeV by LHCb, and are measured up to $p_T = 8$ GeV/c and in the rapidity region of 2.0 to 4.5.
This poster presents the $\Lambda^+_c$/$D^0$ ratio together with comparisons to ALICE results and calculations using pythia plus color recombination and other models.

Speaker: Di Yang (Tsinghua University (CN))

Lambda_ctoD_0_QO_POSTER.pdf

14:28 Prompt $D^+$ and $D_s^+$ production in 8.16TeV $p$Pb collisions at LHCb

The enhanced production of strangeness was first proposed as a signature of the quark gluon plasma creation in heavy ion collisions. Recently, increased strangeness production is also observed experimentally in high multiplicity small systems such as pp and pPb collisions, where formation of QGP is not expected. In this study, production of prompt $D^+$ and $D_s^+$ in $p$Pb collisions is measured with the LHCb detector at center-of-mass energy $\sqrt{s_{NN}}=8.16$ TeV. LHCb's unique forward coverage together with its precise tracking and vertexing provides the possibility to measure the charm hadrons at very low transverse momentum with high accuracy. In addition to the recent results of prompt $D^+$ and $D_s^+$ production, we will also present $D_s^+$ to $D^+$ production ratio as a function of multiplicity and its comparisons to theoretical models.

Speaker: Chenxi Gu (Tsinghua University (CN))

Strangeness Enhancement in Small System at LHCb.pdf

14:32 Prompt open charm production in 5.02TeV pPb collisions with LHCb

Open charm hadrons are collected by the LHCb detector in proton-lead collisions at $\sqrt{s_{NN}}$=5.02 TeV. The excellent performance of particle reconstruction and identification in forward rapidity acceptance allows these charm states to be studied down to very low transverse momentum. This poster presents the LHCb measurement of the production of charm mesons, reconstructed in exclusive hadronic final states. Cold Nuclear Matter effects are studied, quantified by the nuclear modification factors, forward-backward production ratios. Comparisons to theoretical calculations, particularly the ones based on nuclear PDF, are also shown.

Speaker: Yiheng Luo (Tsinghua University (CN))

poster_YihengLuo.pdf

14:36 $\Sigma^0$ reconstruction in Ag+Ag collisions at 1.58$A$ GeV with HADES

HADES investigates the moderate temperature and high density regime of the QCD phase diagram. Strangeness can give a direct insight into the created dense matter, in particular close to the nucleon nucleon production threshold. In 2019 HADES collected Ag+Ag collisions at 1.58$A$ GeV kinetic beam energy. A newly installed electromagnetic calorimeter allows for photon detection. Furthermore the RICH detector was upgraded, which strongly improves electron identification and the detection of conversion-pairs.
In this contribution preliminary results on the search for the $\Sigma^0$ baryon, decaying electromagnetically into $\Lambda + \gamma$ will be presented. Detailed simulations prove the feasibility of this measurement using photon detection in the electromagnetic calorimeter or by employing photon conversion method based on the reconstruction of low momentum electrons in the RICH. Using the photon detected in the electromagnetic calorimeter an estimate of the $\Lambda$/$\Sigma^0$ ratio will be extracted.

Speaker: Marten Becker

QM2022_MBecker.pdf

14:40 Open Charm and Bottom production in Heavy-Ion Collisions: $R_{AA}$ and $v_n-v_m$ correlations within event-shape selection

We discuss the dynamical evolution of charm quark elastic energy loss in a bulk medium at fixed temperature $T$ extending the Boltzmann (BM) collision integral to include off-shell dynamics. We show the results on the transport coefficients and the time evolution of charm quark making a comparison among the Langevin dynamics, the BM collisional integral within a Quasi-Particle Model(QPM) approximation with on-shell QGP medium and the BM collision integral extended to a dynamical quasi-particles model with off-shell bulk particles. We also study the propagation of both charm and bottom quarks in the QGP by means of a full on-shell Boltzmann transport approach within an hybrid coalescence plus fragmentation hadronization model. We show the D-mesons $R_{AA}$ and $v_2$ at RHIC and LHC energies also discussing the role of the initial state fluctuations on the development of high-order heavy-flavor flow harmonics ($v_n(p_T)$, $n=3,4$). The results presented include event-shape selected D-meson spectra and $v_n$, correlations between different D-meson flow harmonics at LHC energies in different range of centrality selections. The events in centrality class are divided according to magnitude of the second-order harmonic reduced flow vector $q_2$. In the same scheme we show predictions for $R_{AA}$, $v_2$ and $v_3$ of B-mesons and both electrons and muons from semileptonic B-meson decays at top LHC energies. Within this approach the extracted T-dependence of the space-diffusion coefficient $D_s$ of both charm and bottom quarks is in a agreement with lattice QCD data within the systematic uncertainties. Lately, we have extended QPM approach to partonic propagators that explicitly depend on three-momentum of particles, futhermore we discuss the impact of momentum-dependent partonic masses on the $D_s$ coefficient providing novel and powerful constraints for heavy-flavour transport coefficients.\

[1] M.L.Sambataro, S.Plumari and V.Greco, Eur. Phys. J. C 80, no.12, 1140
(2020).\

[2] S.Plumari et al., Phys.Lett.B 805 (2020) 135460.\

[2] M.L.Sambataro, S.Plumari, Y. Sun, V. Minissale and V.Greco, in preparation.

Speaker: Maria Lucia Sambataro (University of Catania-INFN(LNS))

Sambataro_QM2022.pdf

14:44 Impact of the initial electromagnetic field on heavy quarks and leptons from Z0 decay and Z0 leptonic invariant mass

Ultra-relativistic heavy ion collisions are expected to generate a huge electromagnetic (e.m.) field that is envisaged to induce several effects on hot QCD matter including the possibility of local parity and local parity and charge conjugation symmetry violations. A direct signature of such e.m. fields and a first quantitative measurement of its strength and lifetime are still missing.
We will discuss why it is expected to generate a splitting of the directed flow of charged particles and anti-particles, which allow to constraint the e.m. field and can be considered also as a possible probe of the formation of the quark-gluon plasma phase. Moreover, we have found a general formula for all possible charge dependent flow observables that can be generated by the strong electromagnetic fields in non-central relativistic heavy ion collisions. The formula has a very simple form at pT larger than several GeV/c, which can be treated as the signature of charged dependent flow observables induced by e.m. fields. Furthermore, we found that the v1 splitting depends critically on the time evolution of the magnetic field. Based on this study, we finally discuss why the measurement of leptons from Z0 decay and its correlation to the charmed mesons are better in probing e.m. fields and thus opening a new way to constrain the EM field.
The second topic we want to discuss is the modification of the Z0 leptonic invariant mass in the presence of EM fields. We found that EM fields will decrease the Z0 leptonic invariant mass and increase the width of it by few hundred MeV if the large of D0 and anti-D0 measured by ALICE is all due to EM fields. Moreover, both the invariant mass and its width are found to approximately depend on the integral of magnetic field quadratically. This provides an independent way to constrain the EM field.

[1] Y. Sun, V. Greco and X.N. Wang, arXiv: 2111.01716.
[2] Y. Sun, S. Plumari and V. Greco, Phys. Lett. B 816, 136271 (2021).
[3] Y. Sun, V. Greco and S. Plumari, Eur. Phys. J. Plus 136, 726 (2021).
[4] S. K. Das, S. Plumari, S. Chatterjee, J. Alam, F. Scardina and V. Greco, Phys. Lett. B 768, 260-264 (2017).

Speaker: Yifeng Sun (INFN-LNS)

Yifeng Sun-QM22.pdf

14:48 Heavy quark momentum diffusion coefficient during hydrodynamization

We extract the heavy quark momentum diffusion coefficient $\kappa$ during the bottom-up thermalization scenario using effective kinetic theory simulations. We compare our nonequilibrium results to the gluonic thermal value for the same energy density, screening mass and infrared temperature. When matching the equilibrium and nonequilibrium systems for the same infrared temperature, we find an agreement at a 10% level when the system is still far from equilibrium with considerable pressure anisotropy of the order of $P_L/P_T=0.1$, while the values of $\kappa$ agree at late times.

Speaker: Jarkko Peuron

QM22.pdf

14:52 Measurement of the correlation between Upsilon states and the underlying event in $pp$ collisions with ATLAS

We present a new measurement studying the relationship between the production of hard and soft particles through the correlation of Upsilon meson states with the inclusive-charged particle yields in 13 TeV $pp$ collisions. Measurements are made differentially for Upsilon momentum and for different Upsilon states. The analysis is performed using the full-luminosity ATLAS Run-2 13 TeV $pp$ data. A description of the technical challenges associated with a heavy-ion style analysis in high-pileup $pp$ data will be shown, as well as the results and their physics implications.

Speaker: Iakov Aizenberg (Weizmann Institute of Science (IL))

AizenbergPosterQM2022.pdf

14:56 Transverse Mass Scaling of Heavy Mesons in $pp$ collisions at the LHC Energies

Transverse mass scaling has been observed for a wide range of particle
species in $pp$ collisions at various energies from the SPS to RHIC and
the LHC. The observed scaling is different for baryons and mesons, and
in this work, we present a comprehensive study of the $m_{T}$-scaling at
LHC energies also extended to the heavier mesons. The study reveals a
systematic pattern in the scaling properties of mesons, which is related
to the particle quark content. In particular, light species and
ground-state quarkonia obey the same scaling, whereas open flavor
particles deviate from it because their spectra are significantly
harder. The magnitude of deviation depends on the flavor of the heaviest
quark in the meson. Extending the transverse mass scaling assumption to
the excited bottomonia states leads to the conclusion that the existing
measurements of their cross-section correspond to approximately a factor
of two suppression in production of these mesons in $pp$ collisions with
respect to expectations from the scaling.

Speaker: Alexander Milov (Weizmann Institute of Science (IL))

sasha_MTS_2022_04_07.pdf

14:00 → 15:00 Poster Session 3 T12_1

14:00 Towards a causal and stable first-order theory of viscous chiral hydrodynamics

Over the past years, considerable effort has been made to study the novel phenomena displayed by chiral systems arising from the interplay between quantum anomalies and the electromagnetic and vortical fields in a hydrodynamic framework [1]. Such novel theory is often referred to as chiral hydrodynamics. It is possible to derive the equations of motion of chiral hydrodynamics from a kinetic theory formulation, the so-called chiral kinetic theory [2]. While this approach has provided great insight into the physics of chiral matter, very little is known about the properties of the chiral hydrodynamic equations of motion and their solutions, especially in the nonlinear regime. Such knowledge is crucial when studying the consequences of the chiral anomaly in hydrodynamic simulations of the quark-gluon plasma formed in heavy-ion collisions. In this work [3] we prove that ideal chiral hydrodynamics, as derived from chiral kinetic theory, is acausal and its initial-value problem is ill-posed. Therefore, such theory cannot be used to determine how the chiral anomaly affects the hydrodynamic evolution. We show that these fundamental issues can be cured by using different definitions (frames) for the hydrodynamic fields. Finally, a new causal and stable first-order theory of viscous chiral hydrodynamics is presented.

[1] D. E. Kharzeev, J. Liao, S. A. Voloshin and G. Wang, Prog. Part. Nucl. Phys. 88, 1-28 (2016)
[2] J-Y Chen, D. T. Son and M. A. Stephanov, Phys. Rev. Lett. 115, 021601 (2015)
[3] E. Speranza, F. S. Bemfica, M. M. Disconzi and J. Noronha, 2104.02110 (2021)

Speaker: Enrico Speranza (University of Illinois at Urbana-Champaign)

speranza_qm_poster.pdf

14:04 New paradigm in anisotropic flow analyses with correlation techniques

The measurements of anisotropic flow in heavy-ion collisions were crucial in establishing the perfect-liquid paradigm about quark--gluon plasma (QGP) properties. Most of these results were obtained with two- and multi-particle correlation techniques, which are in an environment characterized by large multiplicities and large flow values a precision tool. However, in the flow measurements in small-collision systems, correlation techniques are not reliable.

To make further progress, we reconcile for the first time the strict mathematical formalism of multivariate cumulants with the usage of cumulants in anisotropic flow analyses. We demonstrate that properties of cumulants are preserved only for the stochastic observables on which the cumulant expansion has been performed directly, and if there are no underlying symmetries due to which some terms in the cumulant expansion are identically zero. This reconciliation yields to the next generation of observables to be used in flow analyses which do satisfy all fundamental properties of cumulants: symmetric and asymmetric cumulants of flow amplitudes, cumulants of symmetry plane correlations, and event-by-event cumulants of azimuthal angles. Their measurements will provide new and independent constraints on the QGP properties, and in this contribution the first predictions from state-of-the-art theoretical models are presented [1].

We demonstrate how the new event-by-event cumulants of azimuthal angles can disentangle flow and nonflow contributions in the measured correlations. To achieve that goal, we present the first analytic solutions for the long-standing problem of combinatorial background in the measured correlations [2].

We conclude that the observed universality of flow measurements in pp, p-Pb and peripheral Pb-Pb collisions can be attributed solely to the interplay between nonflow correlations and combinatorial background, which always exhibits universal scaling as a function of multiplicity.

[1] A. Bilandzic, M. Lesch, C. Mordasini and S. F. Taghavi, arXiv:2101.05619

[2] A. Bilandzic, arXiv:2106.05760

Speaker: Ante Bilandzic (Technische Universitaet Muenchen (DE))

Bilandzic_TH_20220404-4.pdf

14:08 Exact equilibrium distributions for massive and massless fermions with rotation and acceleration

The equilibrium distribution function of free fermions including
the spin degrees of freedom is a cornerstone for chirality and
polarization studies in relativistic heavy ion physics.
In this talk, we present the first calculation of the exact
Wigner function, spin polarization vector and the chiral distribution
function for massless and massive free fermions at general
global equilibrium with non-vanishing vorticity and acceleration.
The final expression includes all quantum corrections at all orders in
thermal vorticity, hence in $\hbar$.
The method is based on an analytic continuation from imaginary thermal
vorticity, factorization of the density operator and an iterative
solution of the algebraic equations in the thermal expectation values.
A comparison with the previously assumed equilibrium expressions is
made and implications are discussed.

[1] F. Becattini, M. Buzzegoli and A. Palermo, JHEP 02 (2021) 101
[2] A. Palermo, F. Becattini and M. Buzzegoli, JHEP 10 (2021) 077

Speaker: Andrea Palermo

poster.pdf

14:12 Anomalous diffusion in QCD matter

Transverse momentum broadening (TMB) of energetic partons in QCD matter plays a central role in a variety of processes studied at colliders to probe QCD ranging from jet suppression in heavy ion collisions (HIC) to TMD gluon distributions that encode information on the 3D structure of the proton and nuclei in electron-proton or proton-proton collisions. We investigate in this work [1] the leading quantum corrections to the TMB distribution of fast partons in large QCD media. We show in particular that the resummation to all orders of double logarithmic contributions from gluon radiation in the presence of a saturation boundary yields a universal distribution which exhibits anomalous scaling of super diffusive type in contrast with normal diffusion seen at tree level. Exploiting a formal analogy with traveling waves in reaction-diffusion processes and gluon saturation we derive exact pre-asymptotic analytic solutions for fixed [1] and running coupling [2].

This remarkable anomalous diffusion caused by nonlocal quantum corrections is reflected by the emergence of a heavy tail at large transverse momentum, akin to Lévy random walks, which may have measurable effects in dijet production in HIC.

Refs:
[1] Paul Caucal and Yacine Mehtar-Tani (BNL), 2109.12041 [hep-ph]
[2] Paul Caucal and Yacine Mehtar-Tani (BNL), in preparation

Speaker: Dr Yacine Mehtar-Tani (Brookhaven National Laboratory)

QM2022.pdf

14:16 Numerical solutions of the JIMWLK equation with the kinematical constraint

In this talk, I will describe the implementation of the kinematical constraint within the Langevin formulation of the JIMWLK equation following the proposal of Hatta and Iancu. I will discuss the numerical stability and continuum and infinite volume extrapolations. I will compare the solutions with and without the collinear improvement. I will also comment on the rapidity evolution rate of the saturation radius and its modification due to the kinematical constraint. Some of the discussed results were published in arxiv:2111.07427[hep-ph]. Calculations were performed using the software published in SoftwareX 16 (2021) 100887.

Speaker: Dr Piotr Korcyl (Jagiellonian University)

QUARK_MATTER_2022_poster_talk.pdf

14:20 Forward quark jet-nucleus scattering in a light-front Hamiltonian approach

We develop a numerical method to nonperturbatively study scattering and gluon emission of a quark from a colored target using a light-front Hamiltonian approach. The target is described as a classical color field, as in the color glass condensate effective theory. The Fock space of the scattering system is restricted to the |𝑞⟩+|𝑞𝑔⟩ sectors, but the time evolution of this truncated system is solved exactly. This method allows us to study the interplay between coherence and multiple scattering in gluon emission. It could be applied both to studying subeikonal effects in high-energy scattering and to understanding jet quenching in a hot plasma.

Speaker: Meijian Li (University of Jyväskylä)

quarkjet_LFH_MeijianLi_v3.pdf

14:24 Search for dark photons in heavy-ion collisions

The vector $U$-bosons, or so called 'dark photons', are one of the possible candidates for the dark matter (DM) mediators. They are supposed to interact with the standard matter via a 'vector portal' due to the $U(1)-U(1)^\prime$ symmetry group mixing which might make them visible in particle and heavy-ion experiments. While there is no confirmed observation of dark photons, the detailed analysis of different experimental data allows to estimate the upper limit for the kinetic mixing parameter $\epsilon^2$ depending on the mass $M_U$ of $U$-bosons which is also unknown.

In Ref. [1] we have introduced a procedure to define theoretical constraints on the upper limit of $\epsilon^2(M_U)$ from heavy-ion (as well as $p+p$ and $p+A$) dilepton data. Our analysis is based on the microscopic Parton-Hadron-String Dynamics (PHSD) transport approach which reproduces well the measured dilepton spectra in $p+p$, $p+A$ and $A+A$ collisions. Additionally to the different dilepton channels originating from interactions and decays of ordinary (Standard Model) matter particles (mesons and baryons), we incorporate in the microscopic transport approach - for the first time - the decay of hypothetical $U$-bosons to dileptons, $U\to e^+e^-$, where the $U$-bosons themselves are produced by the Dalitz decay of pions $\pi^0\to \gamma U$, $\eta$-mesons $\eta \to \gamma U$ and Delta resonances $\Delta \to N U$.

Using the fact that dark photons are not observed in dilepton experiments so far one can require that their contribution can not exceed some limit which would make them visible in experimental data. By varying the parameter $\epsilon^2(M_U)$ in the model calculations, one can obtain upper constraints on $\epsilon^2(M_U)$ based on pure theoretical results for dilepton spectra under the constraint that the 'surplus' of the DM contribution doesn't overshine the SM contributions (which is equivalent to the measured dilepton spectra) with any requested accuracy. We confront our results with the analysis from the HADES Collaboration [2] at SIS18 energies where the dark photons are not observed as well as with the world data collection.

This analysis can help to estimate the requested accuracy for future experimental searches of 'light' dark photons by dilepton experiments. We note that this procedure can be extended for the search of dark photons of any masses when the corresponding production and decay channels are implemented in the transport approach.

[1] I. Schmidt, E. Bratkovskaya, M. Gumberidze and R. Holzmann, Phys. Rev. D104, 015008 (2021); [arXiv:2105.00569 [hep-ph]].
[2] G.Agakishiev et al. [HADES], Phys. Lett. B731, 265 (2014); [arXiv:1311.0216 [hep-ex]].

Speaker: Prof. Elena Bratkovskaya (GSI, Darmstadt & Frankfurt Uni.)

QM22-Dark_photons_Elena_Bratkovskaya.pdf

14:28 Non-hydrodynamic modes from linear response in effective kinetic theory

Viscous hydrodynamics serves as a successful mesoscopic description of the quark-gluon plasma (QGP) produced in relativistic heavy-ion collisions (HICs). In order to investigate, how such an effective description emerges from the underlying microscopic dynamics we calculate the linear response of energy and flow perturbations in the sound and shear channels from a first-principle calculation in kinetic theory. By using both QCD kinetic theory and Relaxation Time Approximation we investigate the similarities and differences of the excitations in different microscopic theories and compare them to first and second order hydrodynamics. Surprisingly, we find that even for large gradients the Greens functions in QCD Kinetic theory are well described by one hydrodynamic and one non-hydrodynamic mode. We extract the dispersion relations of hydrodynamic and non-hyrodynamic modes and speculate how these results can be used to improve hydrodynamic descriptions of hot QCD matter.

Speaker: Stephan Ochsenfeld

PosterQM2022.pdf

14:32 Maximum entropy kinetic matching conditions for heavy-ion collisions

We propose a new `particlization’ prescription for the conversion of hydrodynamic degrees of freedom to hadrons at the decoupling stage of heavy-ion collisions. Unlike existing particlization schemes, this method uses only macroscopic information provided by the hydrodynamic output and follows directly from the connection between information theory and statistical mechanics. We further use this approach to construct a far-from-equilibrium macroscopic theory that smoothly connects between the free-streaming and hydrodynamic regimes of heavy-ion collisions.

Speaker: Dr Chandrodoy Chattopadhyay (North Carolina State University)

QM22_CC.pdf

14:36 Hydrodynamics of spin currents

We study relativistic hydrodynamics in the presence of a non vanishing spin chemical potential. Using a variety of techniques we carry out an exhaustive analysis, and identify the constitutive relations for the stress tensor and spin current in such a setup, allowing us to write the hydrodynamic equations of motion to second order in derivatives. We then solve the equations of motion in a perturbative setup and find surprisingly good agreement with measurements of global Λ-hyperon polarization carried out at RHIC.

Speaker: Prof. Umut Gursoy (Utrecht university )

14:40 Causal and stable third-order fluid dynamics

Second-order theories of fluid dynamics have been successfully employed to describe the time evolution of the hot and dense matter produced in heavy-ion collisions. Nevertheless, it has been shown that the inclusion of terms that are asymptotically of third order in gradients may be required to describe the dynamics of a fluid in the extreme conditions present at the early stages of these collisions [1]. For this purpose, third-order formulations of relativistic dissipative fluid dynamics were also developed [2]. Recently, a linear stability analysis was performed for such theories and it was demonstrated that they are intrinsically acausal and unstable [3]. In this contribution, we derive linearly causal and stable third-order fluid-dynamical equations from the Boltzmann equation using the method of moments. We show that we recover the theory proposed in Ref. [2] when certain relaxation times are taken to zero, but this limiting procedure is forbidden by causality and stability conditions. Finally, we compare the solutions of our novel theory with those of Boltzmann equation in 0+1 Bjorken flow and show that they are in good agreement.

[1] A. Jaiswal, Phys. Rev. C 87, 051901 (2013).
[2] A. Jaiswal, Phys. Rev. C 88, 021903 (2013).
[3] C. V. Brito and G. S. Denicol, arXiv:[2107.10319]

Speaker: Caio Brito (Universidade Federal Fluminense)

CaioBrito_Poster_QM2022.pdf

14:44 N=4 supersymmetric Yang-Mills thermodynamics from effective field theory

The free energy density of N=4 supersymmetric Yang-Mills theory in four space-time dimensions is derived through second order in the 't Hooft coupling λ at finite temperature using effective-field theory methods. The contributions to the free energy density at this order come from the hard scale T and the soft scale λ√T. The effects of the scale T are encoded in the coefficients of an effective three-dimensional field theory that is obtained by dimensional reduction at finite temperature. The effects of the electric scale λ√T are taken into account by perturbative calculations in the effective theory.

Speaker: Mr Ubaid Tantary (Kent State University)

14:48 Bayesian uncertainty analysis of the elastic nucleon-deuteron scattering observables

Model emulation is an important tool for tackling many nuclear physics problems, including an estimation of model parameters. As Bayesian parameter estimation becomes more common in heavy-ion physics, there is a need for an analysis package to facilitate such projects and to reduce efforts duplication. While the Bayesian statistical formalism handles this exists, the Bayesian Analysis of Nuclear Dynamics (BAND) Framework [1] aims to use computational research to transform these theoretical relationships into practical tools and techniques for making reliable computational predictions of complex systems with well-quantified uncertainties. The latter means using Bayesian statistics to increase the modeling accuracy of theoretical predictions and help in experimental design.

In this poster, for the first time, we outline the emulation (Gaussian processes toolset) and calibration components of the BAND framework to estimate theoretical uncertainties. As an example, we focus on the application of Bayesian inference (in particular Bayesian parameter estimation) to quantify uncertainty for the elastic nucleon-deuteron (Nd) scattering calculations at nucleon laboratory energies up to 200 MeV performed within the Faddeev approach. To that end, we use the current chiral effective interactions comprising semilocal momentum-space regularized two- and three-nucleon forces up to the third chiral order developed by the Low Energy Nuclear Physics International Collaboration (LENPIC) [2]. The uncertainties arising from these effective potentials can be quantified within the BAND framework. We also show truncation errors, which give an important contribution to the uncertainty budget. In this case, we use a slightly modified version of the Bayesian approach [3] developed by the BUQEYE Collaboration [4].

1. D.R. Phillips et al., J. Phys. G: Nucl. Part. Phys. 48 072001 (2021).
   https://bandframework.github.io/
2. P. Maris et al., Phys. Rev. C 103 054001 (2021).
   http://www.lenpic.org/
3. E. Epelbaum et al. Eur. Phys. J. A 56, 92 (2020).
4. J.A. Melendez et al., Phys. Rev. C 96, 024003 (2017).
   https://buqeye.github.io/

Speaker: Dr Yuriy Volkotrub (AGH University of Science and Technology)

QM2022-poster-Volkotrub.pdf

QM2022-presentation-Volkotrub.pdf

14:52 Causal second order magnetohydrodynamics from kinetic theory using RTA approximation

The magnetic field seems to play a significant role in shaping and working the visible universe. It gives rise to a lot of non-trivial and anomalous behavior in the system in which they are present, extending from the effects seen in condensed matter physics in Dirac and Weyl semi-metals to large cosmological objects like in neutron stars or black holes. The strength of the magnetic field in natural systems can be as low as $10^{-5}$T for that of the Earth to as high as $10^{11}$ T in the Magnetars. But the strongest magnetic field on the Earth is manmade and is produced in high-energy heavy-ion collision experiments at RHIC or LHC. The magnitude of the magnetic field produced here is 3 to 4 orders larger than that produced in Magnetars[1]. In a heavy-ion collision, a strongly coupled Quark-Gluon Plasma(QGP) is formed, and its space-time evolution can be described using viscous hydrodynamics formulation. The presence of a strong transient electromagnetic field in the initial stages of heavy-ion collisions indicates that the dynamics of the QGP can be better understood using the RMHD (Relativistic Magnetohydrodynamics) formulation. The RMHD framework describes the system of any relativistic charged fluid and its interaction with the electromagnetic field, and the governing laws for fluid and electromagnetic fields need to be solved in a self-consistent manner. There are a few underlying microscopic theories by which these studies can be done; the kinetic theory is one of them. In our current work[2,3], we use the relativistic Boltzmann equation in the relaxation time approximation for the collision kernel. Here, we have formulated the second-order causal evolution equations for the viscous stresses, e.g., bulk, diffusion, and shear stresses, along with the calculation of relevant transport coefficients for both ideal and resistive MHD. We have also computed anisotropic components of the electrical conductivity. These formulations can serve as an input to numerical studies. Last but not least, we have given $\delta f$ (slight deviation from the equilibrium distribution function), which can be readily applied to the Cooper-Frye prescription for calculating particle spectra in phenomenological studies.

1.Event-by-event fluctuations of magnetic and electric fields in heavy ion collisions,Bzdak, Adam and Skokov, Vladimir.

2."Relativistic resistive dissipative magnetohydrodynamics from the relaxation time approximation", Panda, Ankit Kumar and Dash, Ashutosh and Biswas, Rajesh and Roy, Victor, arxiv:2104.12179

3.Relativistic non-resistive viscous magnetohydrodynamics from the kinetic theory: a relaxation time approach",
Panda, Ankit Kumar and Dash, Ashutosh and Biswas, Rajesh and Roy, Victor,
{10.1007/JHEP03(2021)216}

Speaker: Mr Ankit Kumar Panda (NATIONAL INSTITUTE OF SCIENCE EDUCATION AND RESEARCH)

qm2022.pdf

14:56 Inverse Reynolds-dominance approach to transient fluid dynamics

In the original DNMR derivation [1], irreducible moments are used to derive the evolution equations of second order hydrodynamics for the dissipative quantities (bulk viscous pressure, diffusion current and shear tensor) from kinetic theory. In general, this procedure gives rise to terms of order Kn^2 (second order in gradients), which are parabolic in nature and thus acausal. In this contribution, we rigorously eliminate all parabolic terms by systematically expressing the Kn^2 terms as terms of order Re^{-1} Kn (proportional to the first order gradient of the dissipative quantities). We therefore refer to this scheme as the Inverse Reynolds Dominance (IReD) approach [2]. This procedure fixes the relaxation times of the dissipative quantities in terms of the inverse of the collision matrix and thermodynamic integrals. In particular, we find that the relaxation times corresponding to higher order moments grow as their order increases, thereby contradicting the separation of scales paradigm. The formal (up to second order) equivalence with the standard DNMR approach is proven and the connection between the IReD transport coefficients and the usual DNMR ones is established.

[1] G. S. Denicol, H. Niemi, E. Molnar, D. H. Rischke, Phys. Rev. D 85 (2012) 114047. DOI: 10.1103/PhysRevD.85.114047.
[2] D. Wagner, A. Palermo, V. E. Ambrus, arXiv:2203.12608 [nucl-th].

Speakers: Victor E. Ambrus, Victor Eugen Ambrus (West University of Timisoara (RO))

Ambrus_poster.pdf

14:00 → 15:00 Poster Session 3 T12_2

14:00 The fragmentation region

The very far forward, or ``fragmentation'', region of heavy-ion collisions is critically understudied. The physics of this region is incredibly rich and may lead to insight into a variety of other problems. We present a simple model for understanding the hydrodynamics of the fragmentation region, arguing that a density of 2-3 times nuclear saturation density is reached. We also present a method for understanding bremsstrahlung in the fragmentation region, reconciling the non-perturbative, color-glass-condensate-governed nature of a highly boosted nucleus with the high-$k_T$ physics of perturbative quantum field theory for the first time. These studies provide crucial initial conditions for the correct hydrodynamical modelling of the fragmentation region and give insight into high-density regions of the QCD phase diagram.

Speakers: Isobel Kolbe (Institute for Nuclear Theory), Mawande Lushozi (University of Washington)

The fragmentation region.pdf

14:04 Semi-analytical method of calculating the nuclear collision trajectory in the QCD phase diagram

The finite nuclear thickness affects the energy density $\epsilon(t)$ [1] and conserved-charge densities [2] such as the net-baryon density $n_B(t)$ produced from the primary NN collisions of heavy ion collisions. While the effects are small at high collision energies compared with the standard Bjorken model of the initial state, they are large at low collision energies, where the nuclear passing time is not small compared to the parton formation time. The temperature $T(t)$ and chemical potentials $\mu(t)$ of the dense matter can be extracted from the densities [2]. Therefore, including the nuclear thickness is essential for the determination of the $T-\mu_B$ trajectory in the QCD phase diagram for relativistic nuclear collisions at low to moderate energies such as the RHIC-BES energies.

In this talk, I will discuss our semi-analytical method that includes the nuclear thickness effect and its results on densities $\epsilon(t)$, $n_B(t)$, $n_Q(t)$, and $n_S(t)$. Then, I will show the extracted $T(t)$, $\mu_B(t)$, $\mu_S(t)$, and $\mu_Q(t)$ for a quark-gluon plasma with either quantum statistics or Boltzmann statistics. Next, I will show our results on the $T-\mu_B$ trajectories, highlighting how the trajectories depend on the chosen statistics and the nuclear thickness in relation to the possible location of the critical end point (CEP). Finally, I will show how this semi-analytical model can be useful to researchers who study high density physics and search for the CEP.

References
[1] T. Mendenhall and Z. W. Lin, Phys. Rev. C 103 024907 (2021).
[2] T. Mendenhall and Z. W. Lin, arXiv:2111:13932 [nucl-th].

Speaker: Todd Mendenhall (East Carolina University)

qm-2022-mendenhall-poster.pdf

14:08 The problem of overlapping formation times: IR single-logs

Soft radiative corrections to in-medium g->gg splitting processes have been known to produce double-logarithmic enhancement of the splitting rate. In our previous work on corrections to the leading order LPM effect, we have shown that this double-log enhancement is accompanied by a sub-leading single log behavior. It has been shown by previous authors that these double log enhancements can be absorbed into a running of the medium parameter q-hat. However, less has been known about the sub-leading single logarithmic IR behavior. In the present work, we present analytic results for these single logs and discuss their origin.

Speaker: Dr Shahin Iqbal (National Centre for Physics)

14:12 The hydrodynamic expansion through regularized moments

Relativistic hydrodynamics is surprisingly predictive, even in the presence of large gradients and large deviations from equilibrium. In some of its incarnations, the method of moments can be used to justify the hydrodynamic behavior of a relativistic gas. However, it can’t be directly generalized. If long range interactions are introduced through a medium-dependent mass or a semi-classical gauge field, some diverging integrals would appear at the higher orders after a naive, direct, application of the method [1]. Even if it is not necessary at the lowest orders, it has been shown that it is convenient to reorganize the expansion around resummed moments. In this way one avoids systematically, at all orders, any coupling with ill-defined moments [1].
If one uses the quantum precursor of the distribution function, that is the Wigner distribution, such ill-defined moments arise at the very first step, therefore a regularization scheme is needed from the very the lowest order (hydrodynamics). Even in a physical case that is arbitrarily close to the kinetic limit, some of the moments, which are otherwise well defined in kinetic theory, are divergent due to the off-shell nature of the Wigner distribution. However, in this case too, it is possible to introduce a set of regularized moments [2]. They are well defined at all orders, and they can be used to generalize the method of moments (and the hydrodynamic expansion) in the quantum case. In the kinetic limit they reproduce the ordinary expansion from the method of moments. More importantly, they can be used to estimate whether hydrodynamics is expected to work or to fail in the cases in which the naive generalization of the method is ill-defined and gives no answers. Finally, it can be checked in the exactly solvable (0+1)-dimensional expansion, that the approximate solutions from the regularized hydrodynamic expansion maintain the fast convergence to the exact solutions (already seen in relativistic kinetic theory) even for initial conditions which are very far from the kinetic limit [2].

[1]arXiv:1808.06436
[2]arXiv:2003.09268

Speaker: Dr Leonardo Tinti (Goethe University)

Tinti_QM2022.pdf

14:16 Precise description of multi-parton correlators in the quark-gluon plasma

The high quality experimental data on hard probes in heavy-ion collisions call for a more precise theoretical description of jet evolution in a quark-gluon plasma. To accomplish that we study jet fragmetation via $1\to 2$ final-state parton splittings in the medium. In earlier works [1,2] the authors have usually calculated these processes by invoking one or two approximations: the large-$N_c$ and the eikonal approximations. We want to develop methods to do the calculations without using these approximations, and to quantify the error that is introduced by employing them.

As partons go through the medium their color continuously rotates, an effect that is encapsulated in a Wilson line resumming multiple medium interactions along their trajectory. When calculating observables, one typically has to calculate medium averages of the traces of two or more Wilson lines, leading to correlators of 2 or more partons extended in time. For 2- or 3-point correlators, analytical solutions exist (at least for soft medium interactions described by a harmonic oscillator potential). However, 4-point correlators are usually dealt with in the literature by invoking the large-$N_c$ limit, but exact calculations have been lacking in many cases. In our work [3], we showed how correlators of multiple Wilson lines appear, and developed a method to calculate them numerically to all orders in $N_c$. This result is quite general, and can be used to calculate Wilson line correlators that appear in many areas of particle physics.

In our previous paper, though, we made use of the eikonal approximation, meaning that the partons are assumed to travel in straight lines through the medium. This is a good approximation for hard, balanced splittings. For soft and imbalanced splittings the produced partons can be kicked around by the medium, which is described mathematically by a path integral. We show how the full problem can be transformed into solving a set of coupled Schrödinger equations describing a set of mutually interacting color representations, with the aforementioned Wilson line correlators acting as the potential term. These results are relevant for high-$p_T$ jet processes, multi-gluon emissions in the QGP [4] and initial stage physics [5] at the LHC.

[1] F. Dom ́ınguez, J. G. Milhano, C. A. Salgado, K. Tywoniuk, and V. Vila, “Mapping collinearin-medium parton splittings,”The European Physical Journal C, vol. 80, Jan 2020.
[2] J.-P. Blaizot, F. Dominguez, E. Iancu, and Y. Mehtar-Tani, “Medium-induced gluon branch-ing,”Journal of High Energy Physics, vol. 2013, Jan 2013.
[3] J. H. Isaksen and K. Tywoniuk, “Wilson line correlators beyond the large-Nc,”JHEP, vol. 21,p. 125, 2020.
[4] P. Arnold, T. Gorda, and S. Iqbal, “The LPM effect in sequential bremsstrahlung: nearlycomplete results for QCD,”JHEP, vol. 11, p. 053, 2020
[5] T. Lappi, H. M ̈antysaari, and A. Ramnath, “Next-to-leading order Balitsky-Kovchegov equa-tion beyond largeNc,”Phys. Rev. D, vol. 102, no. 7, p. 074027, 2020.

Speaker: Johannes Hamre Isaksen (University of Bergen)

QM.pdf

14:20 Quantum simulation of string breaking in Schwinger model as open quantum system

Currently there exists no viable ``ab initio'' approach to simulate QCD dynamics at the LHC/RHIC that is universally applicable. This profoundly limits our understanding of the formation, real-time evolution and hadronization of the quark-gluon plasma in heavy ion collisions. Quantum computing may provide a potential solution to efficiently simulate these real-time dynamics within the Hamiltonian formulation of QCD.

In this talk, we discuss a formulation to simulate hard probes of the QGP, such as heavy quarks or jets, on quantum computers through the formalism of open quantum systems [1]. As a start, we present quantum simulation of an open system described by a toy quantum field theory, by studying the non-equilibrium behavior and thermalization of the U(1) gauge theory in 1+1D, i.e., the Schwinger model [2]. We simulate string breaking of fermion pairs in the presence of a thermal environment, which provides a real-time picture of the microscopic dynamics of deconfinement and quarkonium dissociation. We report simulations both on classical simulators as well as quantum devices from IBM, using state-of-the-art error mitigation techniques. These formulations provide the groundwork to extend to QCD and simulate the dynamics of hard probes in the QGP, and we will discuss the prospects of doing so.

[1] de Jong, Metcalf, Mulligan, P\l osko\'n, Ringer, Yao: arXiv 2010.03571
[2] de Jong, Lee, Mulligan, P\l osko\'n, Ringer, Yao: arXiv 2106.08394

Speaker: Dr Xiaojun Yao (Massachusetts Institute of Technology)

QM22 Schwinger.pdf

14:24 How many particles do make a fluid? Searching for fluid dynamic behavior with expanding clouds of few and many cold atoms

The observation of long-range azimuthal anisotropies in small collision systems triggers pressing questions concerning the applicability of fluid dynamics and whether ensembles of only a small number of particles may be effectively treated as fluids. We propose to use experiments on expanding clouds of cold atoms to answer the latter question. We consider strongly-interacting fermions confined in a two-dimensional trap with an elliptical deformation, and, upon release of the trap, we use the emergence of elliptic flow, $v_2$, as an indicator of collective behavior. Borrowing a well-known method from heavy-ion collisions, we quantify the collectivity of the system through the ratio $v_2/\varepsilon_2$, where $\varepsilon_2$ is the anisotropy of the trapping potential. By experimentally controlling both the value of $\varepsilon_2$ and the number of trapped atoms (down to a single particle), one can investigate what particle number is needed for the system to yield a $v_2/\varepsilon_2$ as large as in the fluid dynamic regime. Interestingly, in a quantum formulation, we find that a small number of particles can show elliptic flow even in the absence of interactions, and we discuss how this quantum effect disappears quickly with increasing particle number.

Based on: S. Floerchinger, G. Giacalone, L. H. Heyen, L. Tharwat, https://arxiv.org/pdf/2111.13591.pdf

Speaker: Lars Helge Heyen (Heidelberg University)

Poster_Heyen_QM2022_Collectivity_in_the_few_particle_limit.pdf

14:28 One-loop light cone wave functions with massive quarks

A central ingredient in calculations of scattering processes in the high energy saturation regime of QCD is the light cone wavefunction. It is a universal QCD quantity encoding the light cone gauge partonic structure of a high energy projectile, and a necessary ingredient in cross section calculations for different scattering processes. This talk will report on the recent calculation of the light cone wave functions for a longitudinal [1] or transverse [2] virtual photon to split into quark-antiquark states, including for the first time quark masses at one loop accuracy. These wave functions can be used to calculate cross sections for several precision probes of perturbative gluon saturation at the Electron-Ion Collider. Using these wave functions we derive, for the first time, the total dipole picture DIS cross sections for longitudinal and transverse virtual photons with quark masses. The calculation has required solving a longstanding issue concerning quark mass renormalization in light cone perturbation theory. The quark masses are renormalized in the pole mass scheme, satisfying constraints from the requirement of Lorentz invariance of the quark Dirac and Pauli form factors.

[1] G. Beuf, T. Lappi and R. Paatelainen, Phys.Rev.D 104 (2021) 5, 056032, [2103.14549 [hep-ph]]

[2] G. Beuf, T. Lappi and R. Paatelainen, in preparation.

Speaker: Tuomas Lappi

qm22.pdf

14:32 Spin Alignment of Vector Mesons Induced by the Hydrodynamics Gradients

The measurements of the spin observables open a new window for understanding the quantum properties of the hot and dense medium created in heavy-ion collisions. However, there are still several puzzling phenomena begging for satisfactory explanations. Particularly, the measured spin-alignments of the vector boson is unexpectedly large compared to a class of model calculations. To investigate this problem systematically, we employ the linear response theory formulated in work [1,2] to derive the induced spin-alignment (i.e. spin density matrix) of the vector mesons, such as phi-mesons, by the hydrodynamic gradients [3]. We obtain expressions on spin density matrix that are qualitatively different from those based on the coalescence model. We discuss phenomenological implication of our results.

Refs.

[1] Baochi Fu, Shuai.Y.F.Liu, Longgang Pang, Huichao Song and Yi Yin , “Shear-Induced Spin Polarization in Heavy-Ion Collisions”, Phys. Rev. Lett. 127 (2021) 14, 142301.

[2] Shuai Y.F. Liu and Yi Yin , “Spin polarization induced by the hydrodynamic gradients”, JHEP 07 (2021) 188.

[3] Feng Li, Shuai Y.F. Liu and Yi Yin, in prepration.

Speaker: Feng Li (Lanzhou University)

QM2022PolarizationShortSlides.pdf

14:36 Soft photon radiation in hadronic collisions: color dipole description

The Low theorem, proven only for diffractive photon radiation, cannot be extended to inelastic hadronic collisions with multi-particle production. Comparison with incorrect calculations led to the so-called soft-photon puzzle. We describe soft photon production within the color-dipole approach. The required quark distribution in the colliding hadrons at a soft scale is calculated employing the popular quark-gluon string model (QGSM). The dipole cross section is parametrized and fitted to HERA DIS data at low $Q^2$. Our results are in good accord with data on low-$k_T$ photon yield in pp inelastic collisions.

Speaker: Michal Krelina (Czech Technical University in Prague)

Poster QM2022 v2.pdf

14:40 Promoting gluon saturation to higher precision with dijets at the EIC

The search for gluon saturation is one of the major goals of the future Electron-Ion Collider (EIC). Significant progress has been made in advancing saturation physics to a precision science as we prepare for the EIC era. Focusing on inclusive dijet production in deeply inelastic electron-nucleus, we contribute to these efforts in two ways. First, we quantify the size of kinematic twist and genuine higher twist contributions included in the saturation framework and absent in the TMD framework [1,2]. Second, we perform the first complete next-to-leading order (NLO) computation of inclusive dijets within the Color Glass Condensate (CGC) [3]. I will also comment on implications of our results to the physics of ultra-peripheral collisions at RHIC and the LHC.

References:

[1] Multi-gluon correlations and evidence of saturation from dijet measurements at an EIC. H. Mäntysaari, N. Mueller, F. Salazar, B. Schenke.
PRL 124 (2020) 11, 112301 [arXiv:1912.05586]

[2] The importance of kinematic twists and genuine saturation effects in dijet production at the EIC. R. Boussarie, H. Mäntysaari, F. Salazar, B. Schenke.
JHEP 09 (2021) 178 [arXiv:2106.11301]

[3] Dijet impact factor in DIS at next-to-leading order in the Color Glass Condensate. P. Caucal, F. Salazar, R. Venugopalan.
JHEP 11 (2021) 222 [arXiv:2108.06347]

Speaker: Farid Salazar (UCLA)

QM_2022_dijets_NLO_CGC_Salazar.pdf

14:44 Transient Relativistic Fluid Dynamics in a General Hydrodynamic Frame

The formulation of a causal and stable theory of relativistic viscous hydrodynamics is an important field of current research, with direct applications to the modeling of ultrarelativistic heavy-ion collisions. While the theory of relativistic ideal fluids is well established, the incorporation of dissipation introduces qualitatively new challenges due to the need to maintain relativistic causality and stability. A paradigmatic example of how to ensure causality in the linearized regime and stability is the Mueller-Israel-Stewart (MIS) theory [1]. The key idea is that the dissipative contributions are promoted to new degrees of freedom, whose evolution is determined by additional relaxation-type equations coupled with the conservation laws. In a recent development, an alternative formulation of causal and stable first-order relativistic hydrodynamics was introduced by Bemfica, Disconzi, Noronha [2] and Kovtun [3] (BDNK) and proved to be causal in the nonlinear regime and stable. The basic observation of [2] was that the hydrodynamic variables do not have a unique definition out of equilibrium and one can formulate first-order hydrodynamics in a general hydrodynamic frame, which differs from Eckart and Landau’s standard choices, without employing additional fields beyond those already found in ideal hydrodynamics. In this work [4], we propose a new theory of second-order viscous relativistic hydrodynamics in a general hydrodynamic frame. It differs from MIS by including additional degrees of freedom, and its first-order truncation reduces to BDNK. Causality and stability hold at the linearized level if suitable conditions on transport coefficients are met. Apart from its conceptual implications, this new theory has potential applications to the modeling of the physics of the quark-gluon plasma as well as viscous simulations of neutron star mergers. As an illustrative example we consider Bjorken flow solutions to our equations and identify variables which make an early-time attractor manifest.

[1] W. Israel and J. M. Stewart, Ann. Phys. 118 (1979) 341–372.

[2] F. S. Bemfica, M. M. Disconzi and J. Noronha, Phys. Rev. D 98 (2018), 104064; Phys. Rev. D 100 (2019) 10, 104020; arXiv:2009.11388.

[3] P. Kovtun, JHEP 10 (2019) 034.

[4] J. Noronha, M. Spalinski and E. Speranza, 2105.01034 (2021).

Speaker: Enrico Speranza (University of Illinois at Urbana-Champaign)

speranza_qm_poster_transient.pdf

14:48 Chromoelectric correlators for quarkonia and heavy quarks: a comparison at weak and strong coupling

Suppression of open heavy flavors and quarkonia in heavy-ion collisions is among the most informative probes of the quark-gluon plasma. Interpreting the full wealth of data obtained from the collision events requires a precise understanding of the evolution of heavy quarks and quarkonia as they propagate through the nearly thermal and strongly coupled plasma. In particular, a complete theoretical calculation of the dissociation and recombination rates of quarkonia has thus far been lacking.

It has recently been shown in [1] that such a calculation requires the evaluation of a particular gauge-invariant correlator of chromoelectric fields dressed with Wilson lines, which is very similar to, but different from the correlator used to define the well-known heavy quark diffusion coefficient [2]. Surprisingly, the difference between these two correlators turns out to be subtle: they only differ by a temperature-independent constant at next-to-leading order (NLO) in perturbation theory, as was shown in [3] by comparing to [4]. In this talk, we will explain the similarities and differences between the correlator for heavy quark diffusion and that for quarkonia dissociation/recombination. We will illuminate the differences from both the qualitative physical grounds and the formal expressions. We will explain why the finite-temperature parts agree at NLO. Going beyond the perturbative theory, we will show how an AdS/CFT calculation can unambiguously establish the different nature of these two correlators within N=4 SYM. Finally, we will discuss how our calculation in the strong coupling limit provides important guidance to understand quarkonium evolution at low temperature.

[1] X. Yao and T. Mehen, “Quarkonium Semiclassical Transport in Quark-Gluon Plasma: Factorization and Quantum Correction,” JHEP 02 (2021) 062
[2] J. Casalderrey-Solana and D. Teaney, “Heavy quark diffusion in strongly coupled N=4 Yang-Mills”
[3] T. Binder, K. Mukaida, B. Scheihing-Hitschfeld, X. Yao, “Non-Abelian Electric Field Correlator at NLO for Dark Matter Relic Abundance and Quakonium Transport,” arXiv:2107.03945 [hep-ph]
[4] Y. Burnier, M. Laine, J. Langelage, L. Mether, “Colour-electric spectral function at next-to-leading order”

Speaker: Bruno Sebastian Scheihing Hitschfeld (Massachusetts Institute of Technology)

EECorrelatorsPoster.pdf

14:52 Critical point, Lee-Yang singularities and series expansions

Determining the existence and the location of the QCD critical point remains a major open problem, both theoretically and experimentally. In this work, I present a new way of reconstructing the equation of state in the vicinity of the nearest thermodynamic singularity (the Lee-Yang edge singularity in the crossover region) from a truncated Taylor series expansion in baryon chemical potential. Then, I show that this information can be used to (i) determine the location of the critical point and (ii) constrain the non-universal mapping parameters between the Ising and QCD equations of state.

Speaker: Prof. Kemal Basar (University of North Carolina, Chapel Hill)

14:00 → 15:00 Poster Session 3 T15 / T16

14:00 Cluster and hyper-cluster production in relativistic heavy-ion collisions within the Parton-Hadron-Quantum-Molecular-Dynamics approach

The understanding of the production of (hyper) clusters at midrapidity is presently one of the largest theoretical challenges in the physics of relativistic heavy ion collisions. We study this production employing the Parton-Hadron-Quantum-Molecular-Dynamics (PHQMD) approach [1], a microscopic n-body transport model based on the QMD propagation of the baryonic degrees of freedom with density dependent 2-body potential interactions. All other ingredients of PHQMD, including the collision integral and the treatment of the quark-gluon plasma (QGP) phase, are adopted from the Parton-Hadron-String Dynamics (PHSD) approach. In PHQMD the cluster formation occurs dynamically, caused by the interactions. The clusters are recognized by the Minimum Spanning Tree (MST) algorithm.
We present the PHQMD results for cluster and hypernuclei formation in comparison with the available experimental data at AGS, SPS, RHIC-BES and RHIC fixed target energies. We also provide predictions on cluster production for the upcoming FAIR and NICA experiments.PHQMD allows to study the time evolution of formed clusters and the origin of their production, which helps to understand how such weakly bound objects are formed and survive in the rather dense and hot environment created in heavy-ion collisions. It offers therefore an explanation of the 'ice in the fire' puzzle (cf. [2]).

[1] J. Aichelin et al. Phys. Rev. C 101 (2020) no.4, 044905 [arXiv:1907.03860]
[2] S. Gläßel, et al., 2106.14839 [nucl-th], to be published in Phys. Rev. C.

Speaker: Susanne Gläßel

Phqmd_Experiment_QM.pdf

14:04 Towards solving the puzzle of high temperature light (anti)-nuclei production in ultra-relativistic heavy ion collisions

The creation of loosely bound objects in heavy ion collisions, e.g.~light clusters, near the phase transition temperature ($T_{\rm ch} \approx 155 MeV$) has been a puzzling observation that seems to be at odds with Big Bang nucleosynthesis suggesting that deuterons and other clusters are formed only below a temperature $T\approx 0.1-1 MeV$. We solve this puzzle by showing that the light cluster abundancies in heavy ion reactions stay approximately constant from chemical freeze-out to kinetic freeze-out. To this aim we develop an extensive network of coupled reaction rate equations including stable hadrons and hadronic resonances to describe the temporal evolution
of the abundancies of light (anti-)(hyper-)nuclei in the late hadronic
environment of an ultrarelativistic heavy ion collision.
It is demonstrated that the chemical equilibration of the light
nuclei occurs on a very short timescale as a consequence of the strong
production and dissociation processes.
However, because of the partial chemical equilibrium of the stable hadrons, including the nucleon feeding from $\Delta$ resonances, the abundancies of the light nuclei stay nearly constant during the evolution and cooling of the hadronic phase. This solves the longstanding contradiction between the thermal fits and the late stage coalescence (and the Big Bang nucleosynthesis) and explains why the observed light cluster yields are compatible with both a high chemical production temperature and a late state emission as modelled by coalescence. We also note in passing that the abundancies of the light clusters in the present approach are in excellent agreement with those measured by ALICE at LHC.

Speaker: TIm Neidig (Goethe University Frankfurt )

poster_krakow.pdf

14:08 Light nuclei production with/without critical fluctuation

Light nuclei production is a hot research topic in heavy-ion collision at RHIC-BES. The observed non-monotonic behavior with the colliding energies[1,2] was declared to be related to the critical point of the QCD phase diagram[3,4]. In this talk, we focus on investigating the light nuclei production with and without critical fluctuations within the framework of the coalescence model.

In the first part, we derive the yield of light nuclei in terms of various orders of cumulants for the density distribution function by the implementation of the characteristic function of the phase space density without considering the critical fluctuations. We found that the leading terms of the phase-space cumulants in the yield of light nuclei share a similar form and could be canceled out in light nuclei ratio, whereas the higher-order ones (non-Gaussian shaped density profile) remain and play an important role in the interpretation of the behavior of light nuclei yield ratio.

In the second part, we introduce the static critical correlation contribution to the phase space density and derive the light nuclei production in terms of phase space cumulant. Because the leading terms of the phase-space cumulants in the yield of light nuclei share the similar form, we can construct a new light nuclei yield ratio, which is directly proportional to the critical contribution and can be measured in future experiments.

[1] H. Liu, D. Zhang, S. He, K.-j. Sun, N. Yu, and X. Luo, Phys. Lett. B 805, 135452 (2020).
[2] D. Zhang (STAR), JPS Conf. Proc. 32, 010069 (2020).
[3] E. Shuryak and J M.Torres-Rincon, Eur.Phys.J.A 56 (2020) 9,241.
[4] K.-j. Sun, F.Li and C.M.Ko, Phys.Lett.B 816 (2021) 136258.

Speaker: Shanjin Wu (Peking University)

2022_Shanjin_QM2022.pdf

14:12 Affects of criticality on the light nuclei yields and the hard probes

The existence and the location of the critical end point (CEP) on the QCD phase diagram remains a puzzle. Probing the critical phenomena and locating the CEP are the key goals of the beam energy scan (BES) experiments. When approaching the CEP, the long-range correlation is established, and hence leads to a large fluctuation of the conserved charges. In this presentation, we show, based on the coalescence model and the Landau-Ginzberg theory, that the light nuclei yields and their ratios are enhanced as a consequence of the long-range correlation, which make them ideal probes of criticality [1]. The behavior of the hard probes in the vicinity of the CEP is studied as well [2]. These observables provide us new perspectives for seeking the CEP in the heavy-ion collisions.

Refs.

[1] K. Sun, F. Li and C.M. Ko, "Effects of QCD critical point on light nuclei production", Phys.Lett.B 816 (2021) 136258
[2] F. Li and S. Cao, in prepration

Speaker: Feng Li (Lanzhou University)

QM2022CEP.pdf

14:16 Propagation of tracks using accurate model of ALICE detector magnet system for event visualisation

Phenomenon of bending the trajectory of charged particles in a magnetic field is used as part of the particle tracking and identification system of the ALICE detector at CERN. The detector contains two electromagnets - a large solenoid which generates a magnetic field for the barrel tracking detectors of strength 0.5 Tesla, and a dipole magnet for the Muon Arm Spectrometer which generates a magnetic field of strength 0.7 Tesla. During the calibration of the detector the magnetic field characteristics were measured by the scientific team. The measurement points were then fitted using Chebyshev polynomials to create a field model. This accurate model is applied extensively in the particle trajectory reconstruction. To store the particle data efficiently, only the first detected position of the particle, its type, and the momentum vector is preserved in storage. The particle trajectory, if needed, can be recreated by simulating its propagation in the detector's magnetic field. In the case of track visualisation software however a simpilfied, uniform 0.5 Tesla magnetic field has been used for this purpose so far. For this reason the visualised tracks are not an accurate representation of what was originally detected, especially in the case of particles that interact mostly with the magnetic field generated by the (completly omited in the simplified model) dipole magnet, such as muons.
In our previous publication we have studied how the accurate model could be implemented as a shader program for execution on a GPU, allowing its use in interactive magnetic field visualisations. In this work we explore the benefits of using the accurate model (in the form of our shader program) as a part of a propagation simulation for visualisation of tracks with improved fidelity.

Speaker: Piotr Nowakowski (Warsaw University of Technology (PL))

PN_QuarkMatterPres2022.pdf

14:20 Correcting Distortions in the sPHENIX Time Projection Chamber

The sPHENIX experiment, under construction at Brookhaven National Lab’s Relativistic Heavy Ion Collider, will take first data in 2023, beginning a broad experimental program that will study the emergent properties of QCD in the Quark Gluon Plasma, the structure of jets, and the spin structure of nucleons. The observables that enable these studies require precise tracking provided by three tracking detectors: The innermost MAPS-based vertex detector, a high time-resolution silicon strip detector, and a compact time projection chamber (TPC) with continuous readout through a GEM-based avalanche stage. To meet the needs of the physics program, distortions of the trajectories of drift electrons in the TPC, due to magnetic field and spacecharge effects, must be accurately measured and corrected. In addition to monitoring time-averaged distortions through particle tracks, the TPC has several dedicated components to constrain the distortions. The charge arriving at the readout is digitized and summed into a 'digital current', which monitors the spacecharge flowing back into the volume, and two laser calibration systems monitor the static and short-timescale components of the distortions directly. This poster will discuss the expected magnitudes and structures of the distortions, the systems that monitor those distortions, and the derivation of the necessary corrections; details of how these corrections are implemented in tracking are described in a separate poster.

Speaker: Ross Corliss

QM22_sPHENIX_Distortions.2022.04.08.key

QM22_sPHENIX_Distortions.2022.04.08.pdf

14:24 Feasibility Studies of Di-Electron Spectroscopy with CBM at FAIR

The Compressed Baryonic Matter experiment (CBM) at FAIR is designed to explore the
QCD phase diagram at high net baryon densities and moderate temperatures by means of heavy ion collisions with energies from 2-11 AGeV beam energy (Au+Au collisions) and interaction rates up to 10 MHz, provided by the SIS100 accelerator.
Leptons, as penetrating probes not taking part in the strong interaction, leave the fireball without being modified thus carrying information from the dense baryonic matter. However, di-leptons are rare probes therefore calling for high efficiency and high purity identification capabilities.
In CBM, electron identification will be performed by a Ring Imaging Cherenkov Detector (RICH) and by a Transition Radiation Detector (TRD).
In this contribution, feasibility studies of di-electron spectroscopy from low mass vector meson decays will be presented. Special emphasis is put on the experimental challenge to reduce the combinatorial background in order to get a high significance of the extracted di-electron signal.

Speaker: Cornelius Feier-Riesen

QM2022_poster_Feier-Riesen.pdf

14:28 The Electromagnetic Module for an LHC Run-4 Zero Degree Calorimeter

The Zero Degree Calorimeter (ZDC) at the LHC is primarily a far-forward hadronic calorimeter used to measure spectator neutrons from heavy-ion collisions at the LHC. In addition to spectator neutrons, an electromagnetic module within the ZDC can be used to measure far-forward photons. The Joint ZDC Project (JZCaP) is a collaboration between ATLAS and CMS groups working on R\&D towards an upgraded ZDC for LHC Run-4. In this context, the poster will present design considerations, especially regarding the module segmentation, and results of prototype testing of an EM module for the ZDC.

Speaker: Shir Shenkar (Ben-Gurion University of the Negev (IL))

QM poster.pdf

14:32 Triggering for high-multiplicity events in $pp$ collisions in ATLAS

Conducting inclusive studies by the ATLAS experiment requires collecting maximally unbiased collision samples. The signature of such a collision is the presence of charged particles tracked down to a very low transverse momentum. In addition, the sample of events with high track multiplicity needs to be enriched in $pp$ and $p$+Pb collisions. In the case of $pp$ collisions, the trigger needs to be robust to select high multiplicity collisions with high purity despite not insignificant pileup. The ATLAS trigger system consists of hardware L1 and software HLT systems. The former is incapable of initiating detector readout based on the presence of reconstructed track. Instead, it provides indications of a signal in Minimum Bias Trigger Scintillators, summed energy deposit in calorimeters, or simply random events that are used to direct the events to further analysis by the HLT. The HLT in turn is capable of reconstructing tracks.
Both systems underwent an upgrade during the LHC Long Shutdown 2. In particular, the HLT software was rewritten to be multi-threaded and thus better use modern hardware. The functionality of the inclusive trigger needed to be restored.
Given that the HLT resources are limited, the sequence of selection consists of several fine-tuned steps that need modernization and adaptations. Among various triggers the selection of high multiplicity events is particularly demanding due to the high computational cost of performing tracks reconstruction online. To mitigate that, a ZFinder algorithm for finding an approximation of the collision vertices without reconstructing charged particle tracks was developed. The ZFinder uses extrapolations of approximate helix segments through multiplets of space-points from the tracking detectors. Along with the vertex position an estimate of multiplicity is obtained and can be used for triggering on high multiplicity events in pp and p+Pb.

The performance studies; efficiency, purity, and pileup robustness of the ZFinder algorithm for the high-multiplicity pp collisions will be presented in the poster.

Speaker: Alexander Kevin Gilbert

ATL-COM-PHYS-2022-179-v.1.pdf

14:36 Performance evaluation and mass production status for sPHENIX intermediate silicon tracker

The sPNENIX collaboration will start data taking in 2023 at the Relativistic Heavy Ion Collider in BNL to study the Quark-Gluon Plasma and cold-QCD. A detector complex consisting of the solenoid magnet, a hadron calorimeter, an electromagnetic calorimeter, a time projection chamber, a MAPS-based vertex detector, and the intermediate silicon tracker (INTT) is under construction. A tracking system formed by the three latter detectors enables us to measure the heavy flavor jets and identify the three upsilon states. The INTT surrounding the collision point azimuthally at about 10 cm away with two layers of silicon strip sensors detects hit points at the intermediate area of the tracking system to have better tracking precision. In addition to that, the INTT also provides timing information of the hits, which is possible only by INTT, thanks to its good timing resolution, to eliminate pile-up events by misidentifying bunch-crossing. This poster presentation will show the performance evaluation performed at laboratories and at a beam facility, and mass production status.

Speaker: Dr Genki Nukazuka (RIKEN BNL Research Center)

20220408_poster_slides.pdf

14:40 A Micromegas detector to reconstruct space charge distortions in the SPHENIX TPC

The sPHENIX detector is being constructed at the Relativistic Heavy Ion Collider (RHIC) at the Brookhaven National Laboratory. It will be commissioned for data taking in 2023. It will focus on measuring jets as well as open and hidden heavy flavor production in heavy ion collisions to study the properties of the Quark Gluon Plasma. To achieve its physics program sPHENIX needs a robust and efficient calibration of its constituting detectors. In particular, the distortions of the electrons drift in the sPHENIX TPC (the main tracking device of the experiment) due to magnetic field and space charge effects, must be accurately measured and corrected. The TPC Outer Tracker (TPOT) is a new detector subsystem that will be installed on the outside of the TPC and will greatly facilitate measuring the electron drift distortions in the TPC, in addition to the other existing solutions in sPHENIX. In particular it will allow to make the maximum use of tracks to reconstruct beam-induced space charge distortions and monitor the electron drift velocity. The subsystem consists of 16 Micromegas detectors grouped two-by-two to provide an additional space point on the outside of the TPC in a limited fraction of its acceptance. This poster will discuss the technology used for the Micromegas detectors, the performances of the first detector prototypes, the configuration adopted for the TPOT subsystem, how the subsystem fits into the overall strategy for reconstructing the TPC distortions as well as progress in the construction of the detector itself.

Speaker: Audrey Francisco (CEA)

QM22_sPHENIX_TPOT.pdf

14:44 Calibration of the sPHENIX hadronic calorimeter system

The sPHENIX detector at RHIC is designed to perform high precision measurements of jets and heavy flavor observables to elucidate the microscopic nature of strongly interacting matter. In addition to its electromagnetic calorimeter (EMCal), the sPHENIX calorimeter system includes two hadronic calorimeters (HCals) – the inner HCal (iHCal) and outer HCal (oHCal).
The oHCal (iHCal) are composed of alternating layers of scintillating tiles and steel (aluminum) plates. As hadrons traverse the HCals, the plates cause them to shower and deposit energy in the tiles which is then directed to silicon photomultipliers (SiPMs). The signal from the SiPMs is then aggregated into towers.
Jets will typically deposit energy in all calorimeters; however, this energy must be properly calibrated to get the truth energy, i.e., the energy void of detector effects.
Since the response in the calorimeter varies from tower-to-tower, the calibration must include a tower-by-tower calibration as well as an overall calibration.
This poster will present the calibration plans for the HCals which includes a study comparing cosmic ray data collected by the assembled HCal sectors to the energy deposited by cosmic muons in the GEANT4 simulation of sPHENIX hadronic calorimeter.

Speaker: Ejiro Naomi Umaka (Iowa State University (US))

QM22_sPHENIX_HCAL_v2.pdf

14:48 The mCBM experiment at SIS18 of GSI/FAIR - a CBM precursor and demonstrator

The Compressed Baryonic Matter experiment (CBM) at FAIR is designed to measure nucleus-nucleus collisions at an unprecedented interaction rate of up to 10MHz which will allow the study of extremely rare probes with high precision. To achieve this high rate capability, CBM will be equipped with fast and radiation-hard detectors, which are readout via a triggerless-streaming data acquisition system, transporting data with a bandwidth of up to 1 TB/s to a large scale computer farm for event reconstruction and first level event selection. In order to commission and optimize prototypes and pre-series productions of CBM detector systems with their triggerless-streaming read-out chains under realistic experiment conditions, a precursor experiment and demonstrator named mCBM@SIS18 (short “mCBM") has been constructed 2017/18 at the SIS18 facility of GSI/FAIR, taking data within the FAIR phase-0 program since 2019. The primary aim of mCBM is to commission and optimize (i) the triggerless-streaming data acquisition system including data transport to a high performance computer farm, (ii) the online track and event reconstruction and event selection algorithms and (iii) the online data analysis as well as the controls software packages. mCBM comprises prototypes and pre-series components of all CBM detector subsystems and their read-out systems. During the mCBM beam campaign ‘21 high-rate tests with nucleus-nucleus collisions for various detector subsystems could be performed, furthermore first runs with the final DAQ / data transport configuration of CBM were taken in O+Ni collisions at 2.0AGeV kinetic bombarding energy, running at approx. 1MHz collision rate. First results of the 2021 campaign will be presented.

Adrian Weber for the CBM collaboration

Speaker: Dr Adrian Amatus Weber (Justus-Liebig Universität Giessen)

QM2022_poster_AdrianWeber.pdf

14:52 An Event Plane Detector for sPHENIX

The sPHENIX experiment is currently under construction and will be commissioned for data taking in 2023 at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. The sPHENIX Event Plane Detector (sEPD) will be a new detector sub-system that can be installed into sPHENIX and deliver measurements of jet quenching anisotropy. The sEPD comprises two scintillator disks, one in each of the forward and backward angle regions. Each disk comprises 12 azimuthal sectors, each with 31 segments. Each segment is a scintillator tile with an optical fiber embedded to extract the light signal, which is then read out via silicon photomultipliers. As designed, the sEPD will provide precision measurements of both the event plane and the centrality of heavy-ion collisions recorded during the sPHENIX running. This poster will discuss the physics processes that can be accessed due to this detector, as well as the progress in the constructions of the detector itself.

Speaker: Rosi Reed (Lehigh University)

RReed_QM22_sEPD.pdf

14:00 → 15:00 Poster Session 3 T15_1

14:00 Feasibility study of multiparticle correlations in flow analyses in CBM at FAIR

Analyses techniques based on multiparticle azimuthal correlations are widely used at RHIC and LHC experiments for the measurements of anisotropic flow and related phenomena. These techniques are reliable only when the number of produced particles and the values of flow harmonics are large. This limitation originates from the fact that for flow results obtained with multiparticle correlations, both the statistical error and the most important sources of systematic errors, scale with the inverse powers of multiplicity and flow.

In this poster, we present results from Monte Carlo studies for the feasibility of using multiparticle azimuthal correlations in flow analyses in the CBM experiment at FAIR. The performance in a fixed-target environment characterized with small multiplicities is scrutinized. Both the classical flow observables, $v_n\{k\}$, and the multiharmonic flow correlations obtained with symmetric cumulants, SC($m$,$n$), are presented. The applicability of recently proposed event-by-event cumulants of azimuthal angles in the CBM environment is addressed as well.

Speaker: Ante Bilandzic (Technische Universitaet Muenchen (DE))

Bilandzic_CBM_20220402-1.pdf

14:04 First results with Muon Forward Tracker in pilot pp collisions at LHC-ALICE

In the ALICE experiment at LHC (CERN), the experimental study of quark gluon plasma with the world’s highest energy heavy ion collisions is being conducted for many years. From the LHC Run 3, a new silicon pixel detector, the Muon Forward Tracker (MFT), is installed in front of the muon spectrometer in order to improve the muon tracking in the forward rapidity region. The MFT is made of 5 double-sided disks, concentric with the beam pipe, on which almost 1000 CMOS pixel chips are installed. In addition, a new data computing system called O2 (Online-Offline) is introduced in ALICE to allow synchronous data acquisition and reconstruction from continuous readout, together with asynchronous treatment of the data. The control of the ALICE detector, including MFT, is based on the SCADA (Supervisory Control and Data Acquisition) system integrated into O2. The finite state machine, a hierarchical logical model, is employed for a comprehensive operation to control the MFT. In addition, the interlock system automatically responds to the abnormal state of the detector to ensure a safe operation.

In October 2021, pilot pp collisions were performed in the LHC after the Long Shutdown 2 period. It was the first data acquisition of pp collisions by MFT, and it lasted for five days with a total run time of 28 hours. The detector operation and data processing were tested through the pilot run. Raw data were read out continuously with the frequency of 200 kHz during pilot collisions, and data processing with O2 was commissioned. The data masking based on the noisy pixels and the time duration without physics signals was performed. Processed data were sampled to check the calibration and reconstruction behave as expected. From the hit information, charged-particle tracks were reconstructed, and it succeeded in showing the tracks on the event display. Some data analysis based on the acquired data is already ongoing.

This poster will report the result of the first data acquisition with MFT in pilot pp
collisions.

Speaker: Motomi Oya (Hiroshima University (JP))

20220408_oya_qm_online_final.pdf

14:08 Study of the material budget and data rates for the STS detector system of the CBM experiment

The Compressed Baryonic Matter (CBM), a fixed target experiment is under development at the Facility for Anti-Proton and Ion Research (FAIR) in Darmstadt (Germany). The aim of the experiment is to study the QCD phase diagram of strongly interacting matter at high density and moderate temperature employing heavy-ion beams in the energy range between 2 AGeV – 11 AGeV.

The experiment is designed to run with beam intensities up to 10^9 Au +Au particles/sec and an interaction rate of up to 10^7 collisions/sec. Therefore, fast and free streaming electronics is needed for read-out and data transfer. The silicon tracking system (STS), installed inside a 1 Tm magnet, is the key detector for tracking charged particles. It uses double-sided microstrip silicon sensors of four different sizes to match the varying particle occupancy from the beam axis towards the detector periphery. The read-out electronics are connected to the sensors via polyimide - Al micro-cables placed outside the active region of STS to minimize the material budget. Detailed realistic knowledge of the detector geometry, including both active and passive material, is necessary to estimate the material budget of the detector which has a large impact on the absorption of delta electrons created in beam-target interaction, as well as in nuclear interaction of particles created in the heavy-ion collision with the active and passive materials. We present the status of the simulations of the STS detector geometry and its impact on the expected signal rates.

Speaker: Mr Mehulkumar Shiroya

QM2022_poster_template.pdf

14:12 Test and characterization of the final readout ASIC for the CBM Silicon Tracking System experiment

The Compressed Baryonic Matter (CBM) experiment is a fixed-target heavy-ion physics experiment at the Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany. The CBM physics program aims at exploring the QCD phase diagram at very high baryon densities, where a first-order phase transition from hadronic to partonic matter and a chiral phase transition is expected to occur. For high-statistics measurements of rare probes, CBM is designed to cope with very high interaction rates up to 10 MHz. Therefore, the experiment will be equipped with fast and radiation hard detectors employing free-streaming readout electronics.
The Silicon Tracking System (STS) is the essential component for tracking up to 1000 charged particles per event in nucleus-nucleus collisions. The experimental conditions pose demanding requirements in terms of channel density and read-out bandwidth to be met by the front-end electronics. An essential component is the STS-XYTER, a dedicated ASIC for the readout of the double-sided silicon micro-strip sensors. It is a low power, self-triggering ASIC with 128 channels, 5-bit ADC charge and 14-bit timing information. It needs to be fully integrated into a very confined space and it should perform in a high radiation environment. Several tests have been carried out to check the chips functionalities, the performance of modules as well as integration aspects. This contribution summarizes the characterization procedures of the final STS front-end electronics for different data taking scenarios.

Speaker: Mr Osnan Maragoto Rodriguez (GSI Helmholtzzentrum für Schwerionenforschung GmbH)

QM2022_poster_OsnanMR.pdf

14:16 The ALICE Fast Interaction Trigger Upgrade

Run 3 opens the high luminosity era of the LHC. Collecting vast data samples will enable measurements with unprecedented precision. ALICE aims to record all minimum bias data at the projected 1 MHz pp and 50 kHz heavy ion collision rates. The expected data processing and storage rate will reach ~3 TB/s. To meet this challenge, ALICE underwent a major upgrade of its detectors and systems. One of the four new detectors is the Fast Interaction Trigger (FIT). FIT consists of three subdetectors: FT0, FV0 and FDD. FT0 will generate online triggers, allow multiplicity and vertex determination, background monitoring and luminosity measurements. FT0 will also allow event plane, centrality determination, and provide the precise collision time for the time-of-flight-based particle identification in the offline mode. FT0 is composed of two Cherenkov arrays, installed on both sides of the interaction point, at -0.8 m (-3.4 < 𝜂 < -2.3) and +3 m (3.8 < 𝜂 < 5.0). One of the FT0 arrays is attached to the FV0. FV0 is a segmented, ~1.5 m in diameter plastic scintillator disc, covering the pseudorapidity range of 2.2 < 𝜂 < 5.1. FV0, together with FT0, will serve as the main forward multiplicity detector with a major role in the event plane and centrality determination. The two FDD plastic scintillator arrays are installed at the distance of +17, and -19.5 m from the IP, covering the pseudorapidity ranges of 4.7 < 𝜂 < 6.3 and -6.9 < 𝜂 < -4.9, respectively. FDD will contribute to diffractive measurements and triggers. All FIT detectors use custom-designed front-end electronics with ~200 ns signal processing time. Our poster will include photos of the installed FIT components and the main performance plots from the October 2021 LHC pilot beam.

Speaker: Sandor Lokos (Institute of Nuclear Physics Polish Academy of Sciences (PL))

The ALICE Fast Interaction Trigger Upgrade v5.pdf

The ALICE Fast Interaction Trigger Upgrade v5.pptx

14:20 Performance study of $\rm \Xi^{++}_{\rm cc}$ via decays into $\pi^{+} + \Xi^{+}_{\rm c}(\rightarrow pK^{-}\pi^{+}) $ with ALICE 3

Multi-charm baryons containing multiple charm quarks provide a unique window on uncovering the hadronisation mechanism in the quark-gluon plasma (QGP). The production yield of multi-charm baryons from single hard scattering is negligible compared to the one by coalescence of charm quarks from multiple hard scatterings. In Pb–Pb collisions, multi-charm baryon can be formed by a combination of charm quarks which are formed in independent hard scatterings, leading to an increase of the yield by up to 3 orders of magnitude compared with that in pp collisions.

ALICE 3, the next-generation heavy-ion programme for LHC Run 5, will offer an advanced opportunity to understand QGP, measuring the multi-charm baryon production from proton-proton to heavy-ion collisions. This contribution will present the performance study of $\rm \Xi^{++}_{\rm cc}$ via decays into the non-strangeness channel in pp collisions at $\sqrt{s}$ = 14 TeV with ALICE 3.

Speaker: Jinjoo Seo (Inha University (KR))

220408_jj_QM2022_v4.pdf

14:24 Studying high-density baryonic matter at J-PARC Heavy-Ion Project

J-PARC Heavy-Ion Project (J-PARC-HI) aims at exploring high-baryon density matter in heavy-ion collisions at 1-12 AGeV/c with high-intensity frontier heavy-ion beams. We have designed a heavy-ion acceleration scheme, where a heavy-ion beam is produced in a new heavy-ion injector consisting of a heavy-ion linac and a booster ring, and further accelerated with the existing high-intensity 3-GeV (RCS) and 30-GeV (MR) proton synchrotrons. The heavy-ion beam extracted from MR is transported to the Hadron Experimental Facility to perform the experiment. We will study the properties of the dense matter, explore the phase structures of the QCD phase diagram in the high-baryon density regime such as the first-order phase boundary and the QCD critical point, and search for color-superconducting phases. We will also measure various strange particles/nuclei and study their correlations to unveil the EOS of the matter. In this presentation, we show the development of the staging plan of the project, where in the first phase we will perform the experiment at the upgraded J-PARC E16 spectrometer with $10^{8}$ Hz beams, and in the second phase we will perform the experiment at a new large acceptance spectrometer with $10^{11}$ beams. In particular, we discuss detailed experimental plans with detector upgrades in the first phase such as di-electron and hadron measurements, and the design of a large acceptance spectrometer for event-by-event fluctuations, di-lepton, and heavy flavors in the second phase.

Speaker: Dr Hiroyuki Sako (Japan Atomic Energy Agency)

QM2022-poster-J-PARC-HI-20220408.pdf

14:28 Dielectron physics opportunities with ALICE 3

The ALICE 3 experiment is planed as a compact, next-generation multipurpose detector at the LHC as a follow-up to the present ALICE experiment. It will provide unprecedented tracking and vertexing capabilities down to a few tens of MeV/$c$ in pp, pA and AA collisions and will have a large rapidity coverage $|\eta|<4$. Such detector performances allow to study precisely the dielectron production over a broad range of pair $p_{\text{T}}$ and mass. Dilepton production at very low $p_{\text{T}}$ and mass is particularly sensitive to the electric conductivity of the medium via thermal dielectrons in heavy-ion (AA) collisions. At higher dielectron invariant masses (m$_{ee}$), dielectrons from $\rho$ meson decays carry information about chiral-symmetry restoration, e.g. via the chiral mixing between $\rho$ and $a_1$ mesons. Moreover, the m$_{ee}$ spectrum of thermal dielectrons from the QGP directly provides a mean to estimate the early temperature of the medium in the 1.1 $<$ m$_{ee} <$ 2.7 GeV/$c^{2}$ region, whereas elliptic flow measurement as a function of m$_{ee}$ and pair transverse momentum allow a study of the dynamic in the medium as a function of time. \newline

This poster will give an overview of the performance studies for dielectron analyses with the ALICE 3 experiment aiming at specific criteria to optimise the layout of the detector. A possible way to track and identify electrons will be presented. Furthermore, it will be explained how the combinatoric background can be reduced with a so-called prefilter technique. The capability to reject the correlated heavy-flavour background will be discussed. Finally projections for differential dielectron measurements will be shown.

Speaker: Florian Eisenhut (Goethe University Frankfurt (DE))

QM22-Poster_ALICE3_DielectronOpportunities.pdf

14:32 Background studies for a soft-photon measurement with the Forward Conversion Tracker in ALICE 3

We propose to construct a forward conversion tracker at the LHC to measure photons of a few MeV in transverse momentum, so called ultra-soft photons, which have the potential to resolve the long standing "soft-photon puzzle": Several experiments have observed an excess of ultra-soft photon production with respect to the expected yield from Low's theorem, which is very fundamentally relating ultra-soft photon production from inner Bremsstrahlung and the spectrum of charged hadrons.

It is proposed to include a Forward Conversion Tracker (FCT) in ALICE 3, the next-generation heavy-ion collision experiment proposed for Run 5 and 6 at the LHC, to measure ultra-soft photons at forward rapidities. The dominant background in this measurement, decay photons and external Bremsstrahlung from detector-material interaction, has been investigated and compared to the signal expectation derived from Low's theorem. This is achieved by simulations including the implementation of the proposed ALICE 3 detector geometry, with the beam pipe, barrel tracking layers, and forward disks of the experiment, in a GEANT4 setup. Pp collisions at 13 TeV are simulated with PYTHIA and the produced particles are propagated through the detector system. Aiming at a significant soft-photon measurement, several background-suppression capabilities have been explored: Major improvements were achieved by the rejection of events with an electron or positron in the $\eta$ - range of the FCT and by reducing the material budget in optimising the shape of the beam pipe.
This poster will present the current status of the simulation and the background studies for a soft-photon measurement with the ALICE 3-FCT.

Speaker: Tim Sebastian Rogoschinski (Goethe University Frankfurt (DE))

background_studies_ALICE3_FCT_QM2022.pdf

14:36 Space-charge distortion calibration for the ALICE TPC in Run 3

The Time Projection Chamber (TPC) is the main tracking and particle identification detector of the ALICE experiment at the CERN LHC. For Run 3, starting in 2022, interaction rates of 50 kHz in Pb-Pb collisions require a major upgrade of the TPC readout system. The Multi-Wire Proportional Chambers (MWPCs) were replaced by stacks of four Gas Electron Multiplier (GEM) foils, allowing continuous data acquisition. Due to intrinsic properties of the GEMs, a significant amount of ions produced during the electron amplification drifts into the active volume of the TPC, leading to space-charge distortions of the nominal drift field. Various effects, such as variations in the number of collisions for a given time interval, cause fluctuations of the space-charge distortions on very short time scales. These fluctuations have to be corrected to preserve the intrinsic tracking precision of the TPC of 100 $\mu$m. A dedicated calibration procedure has been developed for the correction of the space-charge distortions. The measured integrated digital currents (IDCs) on the pads, which are used as an estimate for the space-charge density, are processed and taken as an input for a data-driven machine learning approach.
In this poster, procedures developed for the space-charge distortion calibration for the ALICE TPC in Run 3 will be presented.

Speaker: Matthias Kleiner (Goethe University Frankfurt (DE))

QM-2022-space-charge-distortions_V4.pdf

14:40 New method of linseed oil coating for bakelite RPCs for heavy-ion experiments

Single gap Resistive Plate Chambers (RPCs) are currently used in High Energy Physics (HEP) experiments for triggering (ALICE) and tracking (CBM) purposes for high efficiency (> 90%), good time resolution ($\sim$1-2 ns) and low-cost of fabrication. Multigap RPCs (MRPCs) are used for Time of Flight (TOF) measurements for their excellent time resolution. MRPCs are also potential candidates for high-resolution medical imaging.

Keeping in mind their high rate handling capability and cost effectiveness, bakelite plates having moderate to low bulk resistivity are being explored for use as large area RPC in future heavy-ion (HI) collision experiments.

In bakelite RPC, the electrode plates are coated with linseed oil to get rid of the surface roughness of the electrodes, reduce the UV sensitivity and to save the electrode surface from hydrofluoric acid (HF) vapor attack. In conventional bakelite RPC, the linseed oil coating is done after making the gas gap keeping no scope for visual inspection for presence of any uncured linseed oil droplet. In this work, a new technique is introduced to coat the linseed oil in bakelite RPC before making the gas gap. After the linseed oil coating, the plates are cured for several days and then the gas gap is made. The advantage of this procedure is that after linseed oil coating it can be checked visually whether the curing is properly done, or any uncured droplet of linseed oil is present in the gas gap.

Standard NIM electronics is used to test the prototype. When operated with 100% Tetrafluoroethane (C$_{2}$H$_{2}$F$_{4}$) gas in the avalanche mode an efficiency $\sim$90% is achieved using cosmic rays.

Speaker: arindam sen

New Method of Linseed Oil coating for Bakelite_qm2022.pdf

14:44 Forward silicon tracking detector developments for the future Electron-Ion Collider

The proposed high-luminosity high-energy Electron-Ion Collider (EIC) will provide a clean environment to precisely study several fundamental questions in the high energy and nuclear physics fields. A low material budget silicon vertex/tracking detector with fine spatial resolution (hit spatial resolution < 10 $\mu$m) is critical to carry out heavy flavor hadron and jet measurements at the future EIC. Fast timing capability (< 10 ns) helps suppressing backgrounds from neighboring collisions. We will present the design of a proposed Forward Silicon Tracking (FST) detector with the pseudorapidity coverage from 1.2 to 3.5, which can provide both fine spatial and temporal resolutions for the EIC. This detector geometry has been implemented in the GEANT4 simulation in integration with different magnet options and the other EIC detector sub-systems. The proposed FST meets the EIC tracking performance requirements and enables a series of high precision heavy flavor measurements in the forward pseudorapidity region. Several advanced silicon technologies including the Low Gain Avalanche Diode (LGAD) and radiation hard Monolithic Active Pixel Sensor (MALTA) have been considered for the FST design. Progresses and results from the ongoing detector R$\&$D for LGAD and MALTA will be presented as well.

Speaker: Dr Xuan Li (Los Alamos National Laboratory)

QM2022_XuanLi_v2.pdf

14:00 → 15:00 Poster Session 3 T15_2

14:00 Track Reconstruction with the sPHENIX Experiment

The sPHENIX detector at Brookhaven National Laboratory's Relativistic Heavy Ion Collider (RHIC) has a broad experimental QCD physics program that is highlighted by jets, their substructure, and open and closed heavy flavor production. To measure these observables, the sPHENIX tracking system is composed of a monolithic active pixel sensor based vertex detector (MVTX), a silicon strip detector called the intermediate tracker (INTT), and a compact, continuous readout time projection chamber (TPC). Measuring these observables requires precise and efficient track reconstruction in these detectors. This presents challenges due to the large track density environment present in central heavy ion collisions, the high luminosity environment that RHIC will provide, and the streaming readout model that sPHENIX will collect data with. In this poster, we discuss the physics performance of the current track reconstruction. This includes the implementation of TPC distortion corrections into the workflow; details of the distortion calibrations are discussed in a separate poster. Future track reconstruction plans as the experiment approaches first data taking in 2023 will also be discussed.

Speaker: Joe Osborn (Oak Ridge National Laboratory)

QM22Poster.pdf

14:04 sPHENIX MVTX Quality Control and Online System

sPHENIX is a state-of-the-art detector for jet and heavy flavor physics in heavy-ion collisions and going to take data at RHIC in 2023. The sPHENIX MVTX detector has excellent position resolution and vertexing capabilities, which is crucial for heavy flavor physics studies. A dedicated online software system, including the quality control and detector slow control system, is being developed. The quality control system will analyze and display the performance of MVTX in real time for online monitoring. The analysis results will be stored in the database to be retrieved later and studied over a period of time. The detector slow control system is based on WinCC. Shifters can use it to operate the MVTX detector according to real time feedback from the quality control system to maintain the functionality and safety of MVTX. The online system will be used in MVTX commissioning and in the runs to ensure high quality data taking. In this poster, the design and framework of the online system will be discussed. We will also present the general interface and selected hit, cluster, and tracking performance plots from recent Fermilab test beam data and Monte Carlo simulations.

Speaker: Dr Zhaozhong Shi (Los Alamos National Laboratory)

QM22_sPHENIX_Slides_Final_Draft.pdf

14:08 The powering scheme of the CBM Silicon Tracking System: concept and first implementations

The Silicon Tracking System (STS) is planned to be the principal tracking detector of the future CBM experiment at FAIR. It will perform charged-particle track measurement with momentum resolution better than 2% in a 1 Tm dipole-magnetic field. A main challenge for the STS is to maintain high track reconstruction efficiency throughout the projected lifetime of the experiment which means being exposed to an accumulated fluence of up to 10^{14} n_{eq}/cm^2, expected to be reached in beam-target interaction rates of 10 MHz. Therefore, front-end electronics with self-triggering architecture needs to have sufficient signal-to-noise ratio (S/N>10) which requires an ultra-low noise system design.
The STS will consist of eight tracking stations comprising 876 double-sided silicon detector modules installed onto 106 carbon fibre ladders with a total of 1.8 million readout channels. Operation of the system requires a detailed understanding of the electrical scheme at different hierarchical levels, including: low and high voltage systems, copper data lines from the front-end electronics to the read-out and data combiner boards, signal path, as well as grounding and shielding concepts. The performance parameter of the system is equivalent noise charge (ENC) value measured by the front-end electronics.
The electrical scheme of the system as well as its experimental validation in the laboratory and beam will be presented.

Speaker: Anton Lymanets (GSI - Helmholtzzentrum fur Schwerionenforschung GmbH (DE))

QM2022_poster_AL.pdf

14:12 Performance of the mSTS detector in O+Ni collisions at 2 AGeV with the mCBM setup at SIS18

The Compressed Baryonic Matter (CBM) is one of the experimental pillars at the FAIR facility. CBM focuses on the search for signal of the phase transition between hadronic and quark-gluon matter, the QCD critical endpoint, new forms of strange-matter, in-medium modifications of hadrons, and the onset of chiral symmetry restoration.

The Silicon Tracking System is the central detector for momentum measurement and charged-particle identification. It is designed to measure Au+Au collisions at interaction rates up to 10 MHz. It consists of approximately 900 double-sided silicon strip sensors with 1024 strips per side, arranged in 8 tracking stations. This results in 1.8 million channels, having the most demanding requirements in terms of bandwidth and density of all CBM detectors.

In the context of FAIR phase 0, the mini-CBM (mCBM) project is a small-scale precursor of the full CBM detector, consisting of sub-units of all major CBM systems which aims to verify CBM's concepts of free-streaming readout electronics, data transport, and online reconstruction.

In the 2021 beam campaign at SIS18 (GSI) O+Ni collisions at 2 AGeV were measured with a beam intensity up to $10^{10}$ ions per spill. The mini-STS (mSTS) setup used for the 2021 campaign consists of 2 stations with 11 sensors.

First results obtained from data taken in the 2021 beam campaign will be presented with a focus on the hit reconstruction and mSTS performance studies.

Speaker: Dario Alberto Ramirez Zaldivar

QM2022_Ramirez,D.pdf

14:16 A new experiment of di-electron measurements at the 1st stage of J-PARC Heavy-Ion Project.

The purpose of J-PARC Heavy-Ion Project (J-PARC-HI) is to study very
high-baryon density matter with a heavy ion beam of 1-12AGeV. A new
heavy-ion injector and a new booster are necessary for the heavy-ion
acceleration at J-PARC. Reuse of the KEK 500-MeV booster proton
synchrotron is planned at the first stage of J-PARC-HI. The beam
intensity at the first stage is expected to achieve $10^{8}$ Au ions per
spill, which exceeds the beam intensity of the existing high-energy
heavy-ion facilities.
We proposed a new experiment at the first stage of J-PARC-HI using the J
-PARC E16 spectrometer with a moderate detector and DAQ upgrade. The
goal of the new experiment is to search for the first-order phase transition
to the deconfinement phase at extremely high baryon densities using a di
-electron probe. One of the experimental clearest pieces of evidence for
the first-order phase transition is an observation of a plateau structure in
the "caloric curve", which is the dependence of the temperature on the
excitation energy of the system. The virtual photon with intermediate
mass($1<$M$_{ee}<3$GeV/c$^{2}$) will provide information about the initial
temperature of space-time evolution of the medium. The medium
modification of vector mesons and the lifetime of the hot medium also
can be studied from the di-electron spectra in this experiment.
In this poster, we will show the detailed plan of the experiment and
discuss the experimental feasibility.

Speaker: Dr Yuhei Morino (KEK)

ymorino_qm22_v2.pdf

14:20 Projected physics and detector performances for a future fixed target programme at ALICE

It was recently proposed that a Fixed Target (FT) program in the ALICE experiment can give access to the far backward rapidity region for p-A and Pb-A collision systems at an intermediate center of mass energy ($\sqrt{s_{\rm NN}}$ = 115 and 72 GeV for the proton and Pb beam respectively) between RHIC and SPS [1]. The structure of the nuclei can be studied at large x and as a function of the mass number, thanks to the versatility of the target. Moreover, the FT experiment with heavy ion beams at ALICE allows us to make precise studies of quarkonium states, heavy-quark energy loss, transport properties of QGP in new energy and rapidity domains - complementary to the existing LHCb FT setup. The detailed physics motivation, projected performance and possible implementation of a fixed target programme at the LHC can be found in [1,2].

The success of this proposal depends on the integration of the FT setup with the main collider program of ALICE. One of the main concerns is whether the central barrel detectors, namely the TPC can track and reconstruct the fixed target events with sufficient efficiency and resolution. This study uses the ALICE Run 3 software framework (O$^{2}$) to estimate the tracking performance of the TPC for FT events with a solid target placed a few meters upstream to the nominal interaction point of the ALICE detector. In this poster we present the inclusive charged particle tracking efficiency and transverse momentum resolution for inclined tracks (-2 $\leq\eta\leq$ -1) from the simulated FT collisions. Two different target positions have been considered for this study. We also present a fast simulation study of some general physics observables ($e.g.$ collective flow) as well as the reconstruction efficiency of strange ($\Lambda$) and heavy quark ($\rm D^{0}$) hadrons.

[1] C. Hadjidakis et. al., arXiv:1807.00603 [hep-ex].
[2] Galluccio, Francesca et. al., CERN-PBC-Notes-2019-004 (https://cds.cern.ch/record/2671944})

Speaker: Dr Md Rihan Haque (Warsaw University of Technology (PL))

ALICEFTQM22PosterVer4.pdf

14:24 Performance studies of D0D0bar azimuthal correlations in ALICE3

ALICE 3 is a next-generation heavy-ion experiment for LHC Run 5, which will
address physics questions that are not accessible with Runs 3 and 4. One of the main goals of ALICE3 is to understand the connection between heavy quark heavy quark transport and hadronisation. One such example is the measurement of azimuthal correlations between charm and anti-charm mesons. ALICE 3 would provide unique access to this topics and open up new possibilities in other areas too.

In this poster we will present an evaluation of the performance for $\mathrm{D^0-\bar{D}^0}$ correlation studies based on a simulated analysis in ALICE 3. The measurement of azimuthal angle correlations of charm particles provides unique information on the production and transport of charm quarks in the QGP. These methods will be applicable in $\mathrm{pp}$ as well as $\mathrm{A-A}$ collisions. We will also show in details the fitting procedure of 2D distribution of the $\mathrm{D^0-\bar{D}^0}$ invariant mass pairs.

Speaker: Eszter Frajna (Wigner Research Centre for Physics (Wigner RCP) (HU))

Performance_studies_slides.pdf

14:28 A novel algorithm of event mixing for ALICE Run 3

The incoming Run 3 at LHC for ALICE will be characterized by a 50-100 times larger data-taking rate, which requires a redesign of many analysis algorithms in order to meet stricter memory and computational time constraints.

This applies especially to event mixing, which is a crucial component of correlation frameworks. Mixing is a technique of selecting distinct collisions grouped by, e.g., multiplicity and z-vertex and iterating over the tracks (V0s, cascades, …) belonging to these collisions. The resulting tuples of tracks are then used for calculating multiparticle correlations.

Previously, mixing was done in buffers, which directly represented bins of the properties under consideration. However, this approach is slow and requires additional linear memory, unattainable with typical data sizes expected for Run 3. Therefore, a new algorithm was developed with a lazy generation of combinations of data elements. It needs only a small constant memory for storing one combination at a time. The implementation is as generic as possible. It allows for tuples of any size, from any analysis table, and for any number of grouping properties. Moreover, many calculations are performed already during compile time thanks to C++17/20 meta-programming. The mixing algorithm can also be applied beyond particle physics, e.g., to generate pairs of sport competitors from different countries belonging to the same international federation.

Speaker: Maja Kabus (Warsaw University of Technology (PL))

2022-03-29-Quark Matter Maja Kabus.pdf

14:32 Optimization of the calibration parameters for the font-end electronics of the Silicon Tracking System of the CBM experiment

The CBM is a next-generation experiment to be operated at FAIR facility, currently under construction in Darmstadt, Germany. Its goal is to investigate the phase diagram of strongly interacting matter in the region of high baryon-net densities and moderate temperatures, using high-intensity nucleus-nucleus collisions. The setup is designed as a forward multipurpose detector capable to measure hadrons, dileptons, and muons with high precision. To achieve the high rate capability CBM will be equipped with fast and radiation hard detectors employing free-streaming readout electronics. Inside a 1 Tm superconductive dipole magnet is placed the Silicon Tracking System (STS), the main detector for charged particle measurements and momentum determination. The STS is designed as eight tracking layers built from 876 modules. The custom-designed front-end electronics for reading out the double-sided silicon sensors is the STS-XYTER ASIC: analog front-end with CSA, slow and fast shaper paths, ADC, digital part with hit generation and readout.
The characterization of the chip is an extensive procedure that includes multiple functional tests such as proper amplitude and time calibration. These are necessary steps to correctly interpret the collected data. The design of the analog front-end, with a double processing path for independent time and energy measurements, implies that the calibration should consider not only the ADC linearity aspects but also a homogeneous time response among all channels, and a well-known correlation of the threshold in both measuring paths. This work describes the characterization of the timing discriminator of the ASIC, the optimization of other-related chip parameters, and their effect on the measured data.

Speakers: Adrian Rodriguez Rodriguez, Dairon Rodriguez Garces, Dario Ramirez Zaldivar, Osnan Maragoto Rodriguez

QM2022_DAIRON_RODRIGUEZ_GARCES.pdf

14:36 Recent developments in the Silicon Tracking System of the CBM experiment towards starting system assembly

The Silicon Tracking System (STS) is the main tracking detector of the CBM experiment. It is designed to reconstruct trajectories of charged particles with high efficiency, to achieve momentum resolution better than 2% inside a 1 Tm magnetic field, and to be capable of identifying complex decay topologies. The main STS functional building block is the detector module. It consists of a double-sided silicon sensor connected through a stack of low-mass microcables to the custom-developed readout ASICs on two front-end electronics boards. 876 modules are arranged in 8 tracking stations, where 1.8 million channels are read out with self-triggering electronics, matching the experiment’s data streaming and online event analysis concept.  
Currently, the construction of the STS detector advances on multiple fronts: finalizing and testing the mechanical design, testing of the cooling concept via a thermal demonstrator, and the assembly of 3 ladders comprising 30 modules with the final components and procedures for the so-called pre-series production phase. The latter task is essential for testing the assembly concept of the final detector and requires a thorough quality control to ensure reliable performance of the modules and a high production yield. For this purpose, multiple quality control steps have been implemented before and during the assembly of the components and the necessary hardware and software have been developed. This work will present an overview of the results of systematic testing of the STS modules and components, and the most significant achievements and challenges in the detector mechanical assembly and integration.

Speaker: Dr Adrian Rodríguez Rodríguez (CBM Collaboration)

QM2022_Poster_ARRodríguez.pdf

14:40 Prospects for testing Low's theorem with ALICE 3

Soft theorems play a fundamental role in the development of quantum field theory. In scattering processes the production of soft photons diverges in the infrared in a controlled manner. Low's theorem relates the production cross section of a process with and without additional soft photon emission by a simple formula without dependence on the details of the process. However, this simple and fundamental prediction was found to strongly underestimate measured soft photon production in hadronic processes for previous experiments.

With this contribution we discuss the prospects of measuring and investigating this effect with the future ALICE 3 experiment using the proposed Forward Conversion Tracker (FCT). This detector can measure photons from collisions at LHC energies down to very low photon momenta. The resulting measured photons can then be related to the information about the hadronic event measured with ALICE 3. This allows exploration of the apparent discrepancy between calculations and experiment which would significantly impact our fundamental understanding of quantum field theories.

Speaker: Martin Andreas Volkl (Ruprecht Karls Universitaet Heidelberg (DE))

QM22PosterVoelkl.pdf

14:44 Solutions for humidity and temperature monitoring in the Silicon Tracking System of the CBM experiment: Sensors, Testing and DCS integration

The Compressed Baryonic Matter (CBM) is one of the core experiments at the future Facility for Anti-proton and Ion Research (FAIR), Darmstadt, Germany. The Silicon Tracking System (STS) is a central detector system of CBM, placed inside a 1T magnet and with an operation temperature of about $-10 ^oC$ to keep low radiation-induced bulk current in the silicon sensors.

Due to the conditions inside the STS an efficient temperature and humidity monitoring and control are required to avoid icing or water condensation on the electronics or silicon sensors. Most important properties of a suitable sensor candidate are resilience to the magnetic field, ionizing radiation tolerance and fairly small size.

In this contribution we introduce two different approaches to implement relative humidity (RH) and temperature Fiber Bragg Grating Fiber Optic Sensors (FBG FOS). The first approach is based on inscribing both RH and temperature FBG into one fiber and the second one features two separate FBGs arrays. In both cases the RH-sensitive FBGs are coated with polyimide.

Moreover, the applicability and efficiency of FOS in comparison to dew point transmitters and capacitive RH sensors will be discussed. The focus will be also put on the potential integration of the sensors in different levels of interlocks

Speaker: Marcel Bajdel

QM2022_Bajdel_poster.pdf

14:48 Performance study of CBM Muon Chamber detectors at the mCBM setup of SIS18 with Pb+Au collisions at 1.06 AGeV

The CBM experiment at FAIR aims to explore the QCD phase diagram at high net­ baryon density and moderate temperature by colliding heavy nuclei in the energy range 4­-12 AGeV. The Muon Chamber (MuCh) detector at CBM is dedicatedly designed to detect muon pairs originating at different phases in the evolution of the fireball produced in nuclear collisions. MuCh consists of several absorber pieces and detector chambers (called stations), where chambers are placed in between the absorbers to facilitate momentum dependent track identification in high particle density environment upto an interaction rate ~10 MHz. Gas Electron Multiplier detector are used in first two stations of MuCh. Two prototype real size GEM detectors have been tested in mCBM (mini CBM) experiment at SIS18. This mCBM is a part of FAIR phase-­0 program where a pre ­series production of CBM detector systems have been tested with their triggerless streaming readout chain under high particle density environment.

In mCBM campaign ­2020 data for mMuCh along with other sub detectors have been collected for Pb+Au collisions at 1.06 AGeV upto beam intensity of 10$^{8}$/3s spill and with different Au target thicknesses. In this work, we will present the performance of mMuCh in terms of linearity of mMuCh with beam intensity and its time and spatial correlations with other sub detectors. Employing a time­ based event reconstruction technique we have also studied the mMuCh performance in terms of degree of spatial correlations by constructing residual distributions between reconstructed mMuCh hit and projected mTOF tracks at the mMuCh plane.

Speaker: Ms Ekata Nandy (VECC, Kolkata, India)

Ekata_QM2022_poster.pdf

14:52 Dual-readout Calorimeter for the EIC

The Electron Ion Collider(EIC) is considered to construct at Brookhaven National Laboratory. A Dual-readout Calorimeter(DRC) is proposed as the forward calorimeter of the ECCE experiment at the EIC. The DRC consisting of two optical fibers, Cherenkov and Scintillating fibers, of different hadronic and electromagnetic responses allows us to measure electromagnetic and hadronic showers simultaneously with a high resolution. Simulation study is ongoing to implement geometry and evaluate the performance of single particle and jet energy measurements. In this poster, details on the simulation study of the DRC as a forward calorimeter for the EIC will be discussed.

Speaker: Yongjun Kim

QM_poster_presentation_YongjunKim_f.pdf

14:56 Performance Evaluation of Forward Muon Track Matching in ALICE Run 3

In preparation for the LHC Run 3, which will provide collisions at higher luminosity and center-of-mass energy, the ALICE experiment has introduced new detectors in addition to upgrading the existing detectors. As a part of this upgrade, a new silicon pixel tracking detector named Muon Forward Tracker (MFT) with an excellent positional resolution is installed in the forward rapidity region. By combining this new detector with the existing ALICE forward muon detectors, the accuracy in determining a muon production point and a momentum vector, which have been a limitation so far, will be dramatically improved. In order to optimize this performance, it is necessary to correctly combine and match the tracks reconstructed by the new detectors with those reconstructed by the existing detectors. However, since thousands of charged particles are produced in high-energy heavy-ion collisions, the number of possible combinations of tracks is enormous. Especially in the low (transverse) momentum region, it is challenging to combine the tracks correctly because of the effect of multiple scattering in the hadron absorber placed between the two detector sets. Since the physics occurring in the low transverse momentum region is one of the fundamental subjects of interest in the ALICE experiment, we need to improve the efficiency and purity in connecting the tracks in the low transverse momentum region.
In this study, we will tackle this challenging task by using machine learning with simulations and we will present the solution for track matching even if there is large amount of material between trackers.
We have confirmed that the performance of our method achieves a significantly better track matching (or performance) than methods without machine learning, which was initially proposed in the ALICE experiment and mimicked the Kalman filter. We will discuss various inputs and methods for this machine learning application and evaluate the corresponding performance evolution.

Speaker: Mr Ren Ejima for the ALICE Collaboration (Hiroshima University (JP))

0405_ejima_QMposter.pdf

14:00 → 15:00 Poster Session 3 T16

14:00 Measurements of $^{3}_{\Lambda}H$ production and branching ratio fraction $R_3$ by the STAR experiment

Hypernuclei are bound states of nucleons and hyperons, and thus naturally correlated hyperon-baryon systems. Hypernuclei are regarded a unique laboratory to study the hyperon-nucleon ($Y$-$N$) interaction. The $Y$-$N$ interaction is an important ingredient, not only in the equation-of-state (EoS) of astrophysical objects such as neutron stars, but also in the description of the hadronic phase of a heavy-ion collision. The strength of the $Y$-$N$ interaction can be investigated by measuring the properties of hypernuclei. Precise determination of hypernucei structure parameters, such as $\Lambda$ separation energy $B_{\Lambda}$, lifetime, and branching ratios, may also shed light on the role that two-body $Y$-$N$ and three-body $Y$-$N$-$N$ interactions play in the density regime of neutron stars.

In this talk, we report precision measurements of the lifetime of $^{3}_{\Lambda}\mathrm{H}$, $^{4}_{\Lambda}\mathrm{H}$ and $^{4}_{\Lambda}\mathrm{He}$ obtained from Au+Au collisions collected by STAR during the Beam Energy Scan Phase-II program. Hypernuclei are reconstructed via charged pion decay channels including both two-body and three-body decay modes. We also present the relative branching ratio $R_3$ of $^{3}_{\Lambda}\mathrm{H}$ and $^{4}_{\Lambda}\mathrm{H}$, where $R_3$ is the fraction of the two-body decay rate out of the sum of two-body and three-body decay rates. The results will be compared with model calculations and physics implications will be discussed.

Speaker: Yuanjing Ji (Lawrence Berkeley National Lab)

qm22poster_v3.pdf

14:04 Lifetime measurements of light hypernuclei in Au+Au Collisions from STAR experiment

Hypernuclei are bound nuclear systems of correlated nucleons and hyperons. Therefore, the production of hypernuclei in heavy-ion collisions provides an experimental avenue for studying the hyperon$-$nucleon (Y-N) interaction, which is an important ingredient, not only in the equation-of-state (EoS) of astrophysical objects such as neutron stars but also in the description of the hadronic phase of a heavy-ion collision. The strength of the Y-N interaction can be investigated by measuring the properties of hypernuclei. For example, light $\Lambda$-hypernuclei containing one hyperon are conventionally understood as a weakly bound system of a $\Lambda$ and a nucleus, suggesting their lifetimes are close to the free-$\Lambda$ lifetime.

In heavy-ion collisions, light hypernuclei are expected to be abundantly produced at low energies due to the high baryon density. In this poster, we will report precise lifetime measurements of $^3_{\Lambda}H$, $^4_{\Lambda}H$ and $^4_{\Lambda}He$ in Au+Au collisions at $\sqrt{s_{NN}}$ = 3 GeV and 7.2 GeV, recorded by the STAR experiment at RHIC in the fixed-target mode in 2018. The results will be compared with model calculations and physics implications will be discussed.

Speaker: Xiujun Li (USTC)

qmposter_xliv3c.mp4

qmposter_xliv3c.pdf

14:08 Elliptic flow of light nuclei in Au+Au collisions at $\sqrt{s_{NN}}$ = 27 and 54.4 GeV

High energy heavy-ion collisions provide an opportunity to study the production mechanism of light (anti)nuclei. There are two main possible models to explain the production mechanism - the thermal model and the coalescence model. The thermal model has been quite successful in explaining the yields of light (anti)nuclei produced in heavy-ion collisions. Thermal model suggests that the light (anti)nuclei are produced from a thermal source, where they are in equilibrium with other species present in the fireball. However, due to the small binding energies, the produced (anti)nuclei are not likely to survive in the high temperature conditions of the fireball. The coalescence model, on the other hand, predicts that light (anti)nuclei can be formed by the final state coalescence of nucleons. Studying the azimuthal anisotropy of light (anti)nuclei and comparing them with that of nucleons, therefore, will give insights into the production mechanism of light (anti)nuclei.

In this poster, we will present the energy and centrality dependence of elliptic flow ($v_2$) of $d$, $t$, and $^3He$ and their antiparticles in Au+Au collisions at $\sqrt{s_{NN}}$ = 27 and 54.4 GeV. Mass number and number of constituent quarks (NCQ) scalings will also be shown. The $v_2(p_T)$ of light (anti)nuclei will be compared with the coalescence and hydrodynamic models.

Speaker: Rishabh Sharma (Indian Institute of Science Education and Research (IISER) Tirupati)

rishabh_poster_QM22_takafumi_v2.pdf

14:12 Multi-particle collisions in the hadronic stage: Influence of annihilation and catalysis reactions on proton and deuteron yields

Multi-particle reactions in the late stages of heavy-ion collisions are demonstrated to be significant for the final deuteron [1] and proton [2] abundances at intermediate to high beam energies. They are realized by employing a stochastic collision criterion in the hadronic transport approach SMASH.

This work sheds light on the puzzle that both final-state coalescence from nucleons and thermal approaches are able to reproduce the deuteron yield. Employing a microscopic treatment [3] of the deuteron production via direct 3<->2 pion and nucleon catalysis reactions reduces substantially the time required for deuterons to reach partial chemical equilibrium with nucleons. Subsequently, the final yield is practically independent from the number of deuterons on the Cooper-Frye hyper-surface. The results are also able to explain the apparent survival of the light nuclei bound by just few MeV at temperatures of more than hundred MeV - the "snowballs in hell" paradox. The deuteron production is studied in AuAu collisions at $\sqrt{s_{\rm NN}} = 7.7$ GeV as measured by STAR and NA49.

Furthermore, the effect of proton-antiproton annihilation on the (anti-)proton yield is investigated in the late collision stages for a wide energy range of $\sqrt{s_{\rm NN}} = 17.3\, \rm{GeV} - 5.02\, \rm{TeV}$ in AuAu/PbPb collisions. The 5-body back-reaction is included for the first time in a full microscopic description in order to fulfill detailed balance for annihilations. This is achieved by accounting for the regeneration of (anti-)protons via $5\pi\rightarrow p\bar{p}$. The results show that a back-reaction happens for a fraction of 15-20% of all annihilations. Taking the back-reaction into account results in a regeneration of half of the (anti-)proton yield that is lost due to annihilations at mid-rapidity. The decrease of the proton midrapidity yield reduces the tension of thermal model predictions ("proton anomaly") with the experimental data from LHC and could influence the ongoing efforts to constrain the QCD transport coefficients with Bayesian techniques.

[1]: JS, D. Oliinychenko, J. M. Torres-Rincon & H. Elfner, Phys. Rev. C 104, 034908 (2021)

[2]: O. Garcia-Montero, JS, A. Schäfer, J. M. Torres-Rincon & H. Elfner, arXiv:2107.08812

[3]: D. Oliinychenko, L.-G. Pang, H. Elfner, and V. Koch, Phys. Rev. C 99, 044907 (2019)

Speaker: Jan Staudenmaier (Goethe University Frankfurt)

StaudenmaierQM22Posterv2.pdf

14:16 Perspectives on (multi-strange) hypernuclei physics with the CBM experiment at FAIR

The main goal of the CBM experiment at FAIR is to study the properties of nuclear matter at very high baryonic density, where an onset of the transition to a deconfined and chirally restored phase is expected to happen. The study of (multi-strange) hypernuclei production mechanism in high baryon density region of QCD phase diagram, determination of their lifetimes, decay branching ratios and binding energy will provide information on the hyperon-nucleon and hyperon-hyperon interactions, which are essential ingredients for the understanding of the nuclear matter equation-of-state at high densities, and, hence, of the structure of neutron stars.

The CBM detector is designed to measure such rare diagnostic probes with unprecedented precision and statistics. Independent of the production mechanism, theoretical models predict that single and double hypernuclei, and heavy multi-strange short-lived objects are produced in heavy-ion collisions with the maximum yield at FAIR energies. Results of feasibility studies of single and double hypernuclei and hyperon-hyperon interaction from femtoscopic studies in the CBM experiment are discussed.

Speaker: Iouri Vassiliev (GSI)

IVassiliev_QM22_CBM.pdf

14:20 Observation of $^4_{\bar{\Lambda}}\bar{H}$ in heavy-ion collisions at RHIC

Matter-antimatter asymmetry is a precondition necessary to explain the existence of our world made predominately of matter over antimatter. Antimatter is rare in the current universe making it difficult to study, but the Relativistic Heavy-Ion Collider (RHIC) provides us a unique opportunity to study antimatter with high-energy nuclear-nuclear collisions. In this poster, we report the observation of $^4_{\bar{\Lambda}}\bar{H}$ with the STAR experiment at RHIC. $^4_{\bar{\Lambda}}\bar{H}$ is the heaviest anti-hypernucleus ever observed in experiments. Its observation will bring new opportunities for the study of matter-antimatter asymmetry.

Speaker: Tan Lu (Institute of Modern Physics, Chinese Academy of Sciences)

QM_2022_anti_h4l_tan_final.pdf

14:24 Identified particle spectra in isobaric collisions of Ru+Ru and Zr+Zr at sqrt(sNN) = 200 GeV with the STAR experiment

Transverse momentum distributions of identified hadrons provide important information on the transverse expansion and freeze-out properties of the hot and dense matter created
in relativistic heavy-ion collisions. In 2018, the STAR experiment collected large datasets of isobaric collisions of $_{44}^{96}Ru$+$_{44}^{96}Ru$ and $_{40}^{96}Zr$+$_{40}^{96}Zr$ at $\sqrt{s_{\rm {NN}}}=200$ GeV, which provide a good opportunity to study the charged particle spectra in these collisions with great precision. %Furthermore, comparing the results between the two isobaric systems can reveal possible effects induced by isospin and electromagnetic field differences.
In this presentation, we will report analysis progresses towards measuring $\pi^\pm$,$K^\pm$, proton and antiproton spectra as a function of transverse momentum for different rapidity and centrality intervals.
Bulk properties of the system at chemical and kinetic freeze-out are measured. The results bridge the gap in system size between Cu+Cu and Au+Au collisions. Physics implications of these measurements will be discussed.

Speaker: Yang Li

QM22_poster_slides_YangLi_v2.pdf

14:28 Study of Antimatter-Over-Matter Ratios for the Measurement of the Baryon Chemical Potential at the LHC with ALICE

The composition of the fireball produced in high-energy Pb-Pb collisions at the LHC can be described by the Grand Canonical Statistical Hadronisation Model (SHM). One of the parameters of the model is the baryon chemical potential $\mu_B$, which determines the fraction of antimatter and matter present in the gas. The hypothesis that at the LHC $\mu_{B}=0$, i.e. antimatter and matter are perfectly balanced, was tested by a study published in Nature in 2018, where it was found that $\mu_B=0.7\pm3.8\ \mathrm{MeV}$. The goal of this work is to improve the precision on $\mu_B$ by measuring the antimatter-over-matter ratios of protons, $^3\mathrm{He}$ and hypertriton ($^3_\Lambda\mathrm{H}$) reconstructed by ALICE in the LHC Run 2 data. In the SHM the antimatter-over-matter ratios are connected to $\mu_B$ as:

$\bar{h}/h\propto \exp\left[-2\left(B+S/3\right)\mu_{B}/T\right]$,

where $B$ is the baryon number and $S$ the strangeness number of the considered particle species $h$. The analysed species are the most sensitive to the value of $\mu_B$, as they are characterised by large $B$. The techniques used for the measurements of the analysed particles include standard analyses for the proton and helium, which are directly tracked by the ALICE detectors, while the $^3_\Lambda\mathrm{H}$ analysis is based on a Boosted Decision Tree selection applied to the candidates, which are reconstructed via the two-body charged-$\pi$ mesonic decay of the hypertriton.  The obtained $\mu_B$ represents the most precise measurement ever.

Speaker: Mario Ciacco (Politecnico and INFN Torino (IT))

qm2022_ciacco.pdf

14:32 Proton-deuteron and deuteron-deuteron correlation functions and origin of light nuclei from relativistic heavy-ion collisions

Production of light nuclei in relativistic heavy-ion collisions is well described by the thermal model, where light nuclei are in equilibrium with all other hadron species present in a fireball, and by the coalescence model, where light nuclei are formed due to final state interactions after the fireball decays. A method is proposed to falsify one of the models. We suggest to measure a hadron-deuteron or deuteron-deuteron correlation function which carries information about the source of the deuterons and allows one to determine whether a deuteron is directly emitted from the fireball or if it is formed afterwards. The $p\!-\!D$ and $D\!-\!D$ correlation functions are computed to illustrate the statement. For $p\!-\!D$ correlation function the source radius of deuterons formed due to final-state interactions is bigger by the factor of $\sqrt{4/3}$ than that of directly emitted deuterons and for $D\!-\!D$ the factor is $\sqrt{2}$. To check how sizable is the effect we compute the $p\!-\!D$ and $D\!-\!D$ correlation functions taking into account Bose-Einstein statistics of deuterons in case of the $D\!-\!D$ correlation function, $s$-wave scattering due to strong interaction and Coulomb repulsion. The correlation functions are shown to be sensitive to the source radius for sources which are sufficiently small with RMS radii smaller than 3.5 fm. Otherwise the correlation functions are dominated by the Coulomb repulsion and weakly depend on the source radius.

Based on
1. St. Mrówczyński and P. Słoń, Acta Physica Polonica B 51, 1739 (2020),
2. St. Mrówczyński and P. Słoń, Physical Review C 104, 024909 (2021).

Speaker: Patrycja Słoń (National Centre for Nuclear Research)

Slon_QM2022.pdf

14:36 Thermal model description of light nuclei and hypernuclei formation

This study confronts the idea of nuclei and hypernuclei formation within the thermal model description. We have employed a newly developed chemical freezeout (CFO) parametrization method and proposed some ratios of hadrons and nuclei. By varying the decay contribution into the hadrons, we have found that these light nuclei and hyper-nuclei states are formed near the CFO boundary, even before the decay of the hadronic resonance. In this context, we have also investigated the strangeness population factor S3. The novel findings from this study will be significant in the context of data of nuclei and hypernuclei from STAR and FAIR.

Speaker: Deeptak Biswas (The Institute of Mathematical Sciences (IMSc))

14:40 Multiplicity scaling of light nuclei productions in heavy-ion collisions

Light nuclei are the delicate probes of ultra-relativistic heavy ion collisions. Studying the light nuclei productions will help us to understand the nucleon emission source, the nucleosynthesis mechanism and the density fluctuations related to the critical point or first-order phase transition in heavy-ion collisions. In this talk, I will present our recent work about the beam energy dependence of the light nuclei productions and the multiplicity scaling of double ratio, $N_tN_p/N_d^2$, at RHIC Beam Energy Scan region.The multiplicity scaling of double ratio is naturally explained by the interplay between the sizes of light nuclei and the nucleon emission source. Such multiplicity scaling observables can used to extract light nuclei sizes and the effective volume of the firball formed in relativistic heavy-ion collision

Then, I will talk about the collective flow of deuterons and helium-3 at LHC and their sensitivities to the phase-space distributions of protons and nucleons at kinetic freeze-out. Our nucleon coalescence model calculations provide the solid baseline predictions for the yields of light nuclei in the search for the possible QCD critical points at beam energy scan. Coalescence model calculations, together with the proper phase-space distributions of nucleons, validate the picture that light nuclei might be produced through the coalescence of protons and neutrons in relativistic heavy ion collisions at RHIC and LHC.

[1] W. Zhao, K. j. Sun, C. M. Ko and X. Luo, Phys. Lett. B 820, 136571 (2021).
[2] W. Zhao, C. Shen, C. M. Ko, Q. Liu and H. Song,Phys. Rev. C 102, no.4, 044912 (2020).
[3] W. Zhao, L. Zhu, H. Zheng, C. M. Ko and H. Song, Phys. Rev. C 98, no.5, 054905 (2018).

Speaker: Xiaofeng Luo (Central China Normal University)

Light_Nuclei_QM2022.pdf

14:44 Light (anti-)nuclei production from nonlocal many-body scatterings in high-energy nuclear collisions

Understanding light (anti-)nuclei production mechanism is a long-standing challenge in heavy-ion physics. Besides its own importance, it can benefit the search of QCD critical point as well as the detection of dark matter in space. In this presentation, we present a unified description of the microscopic dynamics of light (anti-)nuclei production in high-energy nuclear collisions by solving the relativistic kinetic equations with their nonlocal collision integrals treated with a stochastic method. With the effects of finite nuclei sizes included in the nonlocal collision integrals, this kinetic approach includes the statistical model, the coalescence model, and the conventional transport model for light nuclei production as limiting cases. The stochastic method is benchmarked in a box calculation, in which the thermal limits are correctly reproduced. Besides, our kinetic approach describes well the production of deuteron and helium-3 in both pp and heavy-ion collisions. The application of using light nuclei production to probe QCD critical point is further discussed.

Speaker: Dr Kai-Jia Sun (Cyclotron Institute)

QM2022-KaiJia Sun.pdf

15:00 → 20:00 FREE AFTERNOON

Saturday, 9 April

09:00 → 10:30 Plenary Session VI: Lattice / Phase diagram

Convener: Chihiro Sasaki

09:00 Overview of the lattice QCD at finite temperature and density (TH)

Speaker: Gert Aarts (Swansea University)

QM-Aarts.pdf

09:30 Experimental and theory overview of QCD Phase Diagram (EX/TH)

Speaker: Adam Bzdak (AGH University of Science and Technology, Poland)

qm22.pdf

10:00 EOS at high-baryon density and compact stellar objects (TH)

Speaker: Veronica Dexheimer (Kent State University)

Dexheimer.pdf

10:30 → 11:00 Coffee break

11:00 → 13:00 Plenary Session VII: Spin / Conserved charges

Convener: Nu Xu

11:00 Fluctuations of conserved charges (EX)

Speaker: Toshihiro Nonaka (University of Tsukuba)

tnonaka_QM2022.pdf

11:30 CME – experimental results and interpretation (EX)

Speaker: Fuqiang Wang (Purdue University (US))

fqwang_CME_QM2022.pdf

12:00 Spin polarisation measurements (EX)

Speaker: Debojit Sarkar (Wayne State University (US))

QM_2022_dsarkar_submit.pdf

QM_2022_final_version_pdf_v2.pdf

12:30 New developments in relativistic hydrodynamics (TH)

Speaker: Nora Weickgenannt (Goethe University Frankfurt)

QM22_Weickgenannt.pdf

13:00 → 14:30 Lunch

14:30 → 16:00 Plenary Session VIII: BES / EM probes

Convener: Iwona Grabowska-Bold (AGH University of Science and Technology (PL))

14:30 Results from the BES programme at RHIC (EX)

Speaker: Hanna Zbroszczyk (Warsaw University of Technology (PL))

Zbroszczyk-Hanna.pdf

15:00 Experimental overview of electromagnetic probes (EX)

Speaker: Klaus Reygers (Ruprecht Karls Universitaet Heidelberg (DE))

reygers_qm2022_em_probes_exp_v3.pdf

15:30 Theory and phenomenology of electromagnetic probes (TH)

Speaker: Gojko Vujanovic (Wayne State University)

QM22_GV_v2.1.pdf

16:00 → 16:30 Coffee break

16:30 → 18:30 Plenary Session IX: UPC / HF

Convener: Roberta Arnaldi (Universita e INFN Torino (IT))

16:30 Experimental and phenomenological developments in ultra-peripheral collisions (EX/TH)

Speaker: Mateusz Dyndal (AGH UST Krakow)

mdyndal_qm22.pdf

17:00 Experimental results on open and hidden heavy quark production (EX)

Speaker: Cristina Terrevoli (University of Houston (US))

QM2022_terrevoli_HQ_9Apr.pdf

17:30 Production and hadronisation of heavy-flavour hadrons (TH)

Speaker: Min He (Nanjing University of Science & Technology)

M.He_QM22_v6.pdf

18:00 Overview of exotic states production and perspectives for HI collisions (EX)

Speaker: John Matthew Durham (Los Alamos National Laboratory)

Durham_Exotics_QM22.pdf

20:00 → 23:00 Conference Dinner

Sunday, 10 April

09:00 → 10:30 Plenary Session X: PDFs / Future

Convener: Luciano Musa (CERN)

09:00 Constraining PDFs and nPDFs with recent data (TH)

Speakers: Petja Kalle Matias Paakkinen (Helsinki Institute of Physics (FI)), Petja Paakkinen

QM2022_Paakkinen.pdf

09:30 The near- and mid-term future of RHIC, EIC and sPHENIX (EX)

Speaker: David Morrison

Morrison QM2022.pdf

10:00 The near- and mid-term future of the LHC (EX)

Speaker: Jochen Klein (CERN)

2022-04-10-QM-Future_LHC_exp-jkl-v1.pdf

10:30 → 11:00 Coffee break

11:00 → 12:00 Flash Talks/Poster Awards

Convener: Tadeusz Lesiak (Polish Academy of Sciences (PL))

11:00 Introduction

Speaker: Tadeusz Lesiak (Polish Academy of Sciences (PL))

Introduction.pdf

11:05 Constraining Neutron-Star Matter with Microscopic and Macroscopic Collisions

Speaker: Kshitij Agarwal (Eberhard Karls Universität Tübingen (DE))

20220408_Agarwal-LeFevre_QM2022.pdf

11:10 Heavy quarks in the evolving Glasma: diffusion, 2-particle correlations and comparison with Langevin dynamics

Speaker: Dana Avramescu

da_qm22_flash_talk.pdf

11:15 Measurement of low-momentum direct photons in Au+Au collisions at 200 GeV

Speaker: Wenqing Fan (Lawrence Berkeley National Lab. (US))

QM2022_flash_talk_wenqing_041022.pdf

11:20 Bayesian quantification of the Quark-Gluon Plasma from a hybrid model with an IP-Glasma initial state

Speaker: Matthew Heffernan (McGill University)

Heffernan-QM2022-Poster.pdf

11:25 Identified hadron spectra and baryon stopping in 𝛾+Au collisions at STAR

Speaker: Nicole Lewis (Brookhaven National Laboratory)

Nicole_Lewis_QM2022_Flash_Talk.pdf

11:30 Search for higher mass resonances via KK decay channel in pp collisions with ALICE at the LHC

Speaker: Dukhishyam Mallick (National Institute of Science Education and Research (NISER) (IN))

Searchforglueball_KKchannel_QM2022_flash_talk.pdf

11:35 Using active learning to constrain the size and location of the QCD critical point

Speaker: Débora Mroczek (University of Illinois at Urbana-Champaign)

Mroczek_QM22_flashtalk_revised.pdf

11:40 Multi-dimensional measurements of the parton shower in pp collisions at RHIC

Speaker: Monika Robotková (Nuclear Physics Institute, Czech Academy of Sciences)

QM2022_flashtalk_Robotkova.pdf

11:45 Space-time evolution of critical fluctuations in an expanding system

Speaker: Azumi Sakai

QM2022_Sakai_Flash_Talk.pdf

QM2022_Sakai_Flash_Talk.pptx

11:50 Anisotropy of the QGP droplet explored through high-𝑝⊥ data

Speaker: Stefan Stojku

QM2022_presentation_StojkuStefan(1).pdf

12:00 → 12:15 Awarding of the Zimanyi Medal

Convener: Peter Levai (Wigner Research Centre for Physics (Wigner RCP) (HU))

12:00 Awarding of the Zimanyi Medal

Speaker: Peter Levai (Wigner Research Centre for Physics (Wigner RCP) (HU))

Zimany2022_BMuller.pdf

ZimanyiMedal_QM22_Cracow_subm.pdf

12:15 → 12:30 Quark Matter 2023 presentation

Convener: Rene Bellwied (University of Houston (US))

cracow-final.mp4

12:30 → 13:30 Summary/Farewell Session