Quark Matter 2023

3 Sept 2023, 08:00 → 9 Sept 2023, 13:25 US/Central

Hilton of the Americas, 1600 Lamar, Houston, Texas, 77010, USA

Claudia Ratti, Frank Geurts (Rice University (US)), Ralf Rapp, Rene Bellwied (University of Houston (US))

Quark Matter 2023 is the XXXth International Conference on Ultra-relativistic Nucleus-Nucleus Collisions, which will be held in Houston, Texas, USA. 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.

The scientific program will cover the following topics:

• Chirality
• Collective Dynamics
• Critical point searches
• Electromagnetic Probes
• Future facilities/detectors
• Heavy flavor physics
• Initial state of particle collisions
• Jets
• Light and strange flavor physics
• New theoretical developments
• Nuclear astrophysics
• Physics of the Future Electron Ion Collider and the RHIC Spin program
• Physics of ultra-peripheral collisions
• QCD at finite density and temperature
• Small systems

 

 

Booklet4_online.pdf

Poster_Session_Map_Last5.pdf

QM2023_Poster.pdf

QM_Logos.pdf

Sunday, 3 September

08:00 → 09:00 Student Registration

09:00 → 10:30 Student Lectures

Convener: Saskia Mioduszewski (Texas A&M University)

09:00 Detectors in Heavy Ion Physics

Speaker: Thomas Hemmick

Detectors.pdf

09:45 Jet Physics

Speaker: Raghav Kunnawalkam Elayavalli (Vanderbilt University)

student_day_intro_jet_raghav_3Sept2023.pdf

10:30 → 11:00 Coffee Break

11:00 → 12:30 Student Lectures

Convener: Saskia Mioduszewski (Texas A&M University)

11:00 Bulk Physics - Flow and Correlations

Speaker: Prof. Hanna Zbroszczyk (Warsaw University of Technology (PL))

Zbroszczyk-Hanna.pdf

11:30 Bulk Physics - Critical point searches

Speaker: Lijuan Ruan

Ruan.pdf

12:00 Bulk Physics - Finite Density QCD

Speaker: Thomas Schaefer

talk_QM_2023.pdf

12:30 → 14:00 Lunch

14:00 → 16:15 Student Lectures

Convener: Manuel Calderon De La Barca (UC Davis)

14:00 Heavy Flavor Physics

Speaker: Enrico Scomparin (INFN Torino (IT))

QM23Lecture_Enrico_v4.pdf

14:45 Ultra-peripheral Collisions and Electromagnetic Probes

Speaker: Prof. Daniel Tapia Takaki (University of Kansas)

DTT - QM 2023 v2.pdf

15:30 The Physics of the EIC

Speaker: Elke Aschenauer

8_Elke.pptx

16:15 → 16:45 Coffee Break

16:45 → 18:00 Panel Discussion on Mentoring and Career Opportunities

Convener: Daniel Tapia Takaki (University of Kansas)

9_Daniel.pdf

19:00 → 22:00 An Evening at the Rustic (w. Music and Food)

Monday, 4 September

08:00 → 08:45 Registration

08:45 → 09:15 Welcome and Introductions

09:15 → 10:00 Keynote talk

Speaker: David Gross (KITP/UCSB)

10:00 → 10:30 Coffee Break

10:30 → 12:35 Plenary Session

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

10:30 ALICE Overview

Speaker: Ionut Cristian Arsene (University of Oslo (NO))

IArsene_QuarkMatter_v4.pdf

QM23proceedings_v5.pdf

11:00 ATLAS Overview

Speaker: Aaron Angerami (Lawrence Livermore Nat. Laboratory (US))

QM23_talk.pdf

11:25 CMS Overview

Speaker: Austin Alan Baty (Rice University (US))

Baty_CMSOverview_QuarkMatter_23_v10.pdf

11:50 LHCb Overview

Speaker: John Matthew Durham (Los Alamos National Laboratory)

MattDurham_LHCb_QM23.pdf

12:15 HADES Overview

Speaker: Simon Spies (Johann-Wolfgang-Goethe Univ. (DE))

SimonSpies_HADESOverview_Final.pdf

12:35 → 14:00 Lunch

14:00 → 15:30 Plenary Session

Convener: Johanna Stachel (Heidelberg University (DE))

14:00 STAR Overview

Speaker: Rosi Reed

RReedQM2023_STARoverview_v7.pdf

14:30 PHENIX Overview

Speaker: Christine Nattrass (University of Tennessee (US))

NattrassPHENIXQM2023.pdf

14:50 sPHENIX Overview

Speaker: Edward O'Brien (Brookhaven National Lab)

3_Edward_O_Biren.pdf

15:10 NA61/SHINE Overview

Speaker: Piotr Podlaski (University of Warsaw (PL))

podlaski_qm2023.pdf

15:30 → 16:00 Coffee Break

16:00 → 18:00 Plenary Session

Convener: Veronica Dexheimer

16:00 Lattice QCD Overview

Speaker: Attila Pasztor (Eötvös University)

QM23_Pasztor.pdf

16:30 Quark Matter and Nuclear Astrophysics

Speaker: Tyler Gorda (TU Darmstadt)

Tyler_Gorda-Quark_Matter_2023.pdf

17:00 New Tools for Data Analysis and Simulations

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

Mulligan_QM.pdf

17:30 Diversity, Equity and Inclusion in Nuclear and Particle Physics

Speaker: Geraldine Cochran (Rutgers University)

Cochran_2023_Quark_Matter.pdf

19:30 → 22:00 Reception at the Houston Museum of Natural Sciences

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

Tuesday, 5 September

08:30 → 10:30 Chirality: (1)

Convener: Dirk Rischke

08:30 Hyperon Polarization in Heavy Ion Collisions from STAR

The observation of hyperon polarization has revealed the existence of large vorticities in the medium created by heavy-ion collisions. Global polarization indicates vorticities perpendicular to the reaction plane due to the system's orbital angular momentum. The difference of global polarization between $\Lambda$ and $\bar{\Lambda}$ hyperon can provide essential insights into the late-stage magnetic field sustained by the QGP.

With the high-statistics data collected by the STAR experiment for isobar Ru+Ru and Zr+Zr collisions at $\sqrt{s_{\mathrm{NN}}} = 200$ GeV, we present the measurements of global polarization for $\Lambda$, $\bar{\Lambda}$, and $\Xi^{\pm}$ as a function of centrality, transverse momentum, pseudorapidity, and azimuthal angle relative to the event plane. In addition, we present the correlation between the initial tilt of the system and the vorticity through the dependence of the $\Lambda$ global polarization and directed flow on the first-order flow vector ($q_1$) in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}} = 19.6$ GeV.

The local polarization indicates vorticities along the beam direction due to anisotropic transverse expansion of the medium. We present the first measurements of $\Lambda$, $\bar{\Lambda}$ hyperon local polarization in isobar collisions at $\sqrt{s_{NN}}$= 200 GeV and Au+Au collisions at $\sqrt{s_{NN}}$= 19.6, 27 GeV. Comparisons with previous measurements in Au+Au and Pb+Pb collisions at RHIC and LHC provide important insights into the collision system size and energy dependence of the vorticities. Furthermore, the local polarization measurements at lower beam energies can probe the predicted baryonic spin hall effect in a dense baryonic environment in heavy-ion collisions.

Speaker: Xingrui Gou

QM2023_Xingrui_v4.pdf

08:50 Search for anomalous chiral effects in heavy-ion collisions with ALICE

The interplay of the chiral anomaly and the strong magnetic or vortical field created in the off-central heavy-ion collisions can give rise to anomalous chiral effects in the quark--gluon plasma. These include the Chiral Magnetic Effect (CME), the Chiral Magnetic Wave (CMW) and the Chiral Vortical Effect (CVE). The study of these novel phenomena is of fundamental significance since they may reveal the topological structure of vacuum gauge fields, as well as the possible local violation of P and/or CP symmetries in strong interactions.

In this talk, we present comprehensive measurements of anomalous chiral effects in Xe--Xe and Pb--Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.44 TeV and 5.02 TeV, respectively, with ALICE. The CME is studied using the charge-dependent two- and three-particle correlators. The Event Shape Engineering (ESE) technique, together with the Monte Carlo Glauber and T$_{\rm R}$ENTo simulations of the magnetic field are employed to derive an upper limit on the CME signal. The ESE technique is also adopted to quantitatively constrain the strength of the CMW signal, which is examined by the correlation between the charge asymmetry and the elliptic flow. The CVE is studied using several combinations of azimuthal correlations between baryon pairs at different kinematic windows, such as $\Lambda-p$, $\Lambda-\Lambda$ or $p-p$. These measurements provide new insights into the experimental search for anomalous chiral effects in heavy-ion collisions.

Speaker: Chunzheng Wang (Fudan University (CN))

AnomalousChiralEffect_ALICE_QM23_Chunzheng.pdf

09:10 QGP vortex rings as a new probe for jet-induced medium response and longitudinal dynamics

Hydrodynamics provides quantitative descriptions of various flow measurements in heavy-ion collisions, suggesting the strongly-coupled nature of the hot QCD matter. A ubiquitous phenomenon in fluid dynamics is the formation of vortex rings. In heavy-ion collisions, different conditions can give rise to toroidal vortex structure in the QGP medium, such as the medium's response to jet thermalization [1] and the early-stage longitudinal dynamics in asymmetric collisions [2]. Considering these scenarios, in this talk, we will present a systematic study of how $\Lambda$ hyperon's polarization can probe these toroidal vortex structures in QGP. We define a "ring observable" in terms of the $\Lambda$ production plane polarization [2]. It represents a measure of the effects caused by the vorticity induced in the ring formation. By conducting event-by-event analysis with the state-of-the-art (3+1)D theoretical framework [3, 4], we demonstrate that this ring observable is a highly sensitive probe for thermalizing energy-momentum currents deposited from high-energy jets and for the early-time longitudinal dynamics in asymmetric collision systems. An experimental indication of such ``smoke rings'' formed in the QGP would represent a significant advancement in studying the emergent phenomena of many-body QCD at multiple length scales.

[1] W. M. Serenone, D. D. Chinellato, M. A. Lisa, C. Shen, J. Takahashi and G. Torrieri, "$\Lambda$ polarization from thermalized jet energy", Phys. Let. B 820, 126500 (2021)

[2] M. A. Lisa, J. G. P. Barbon, D. D. Chinellato, W. M. Serenone, C. Shen, J. Takahashi and G. Torrieri, "Vortex rings from high energy central p+A collisions", Phys. Rev. C 104, no.1, 011901 (2021)

[3] V. H. Ribeiro, W. M. Serenone, D. D. Chinellato, M. A. Lisa, C. Shen, J. Takahashi and G. Torrieri, "$\Lambda$ polarization from vortex ring as medium response for jet thermalization", arXiv:2305.02428 [hep-ph] (2023)

[4] C. Shen and B. Schenke, "Longitudinal dynamics and particle production in relativistic nuclear collisions", Phys. Rev. C 105, no.6, 064905 (2022)

Speaker: Willian Matioli Serenone (Universidade de São Paulo)

TalkQM2023-Serenone.pdf

09:30 New Insights into Global Spin Alignment in Heavy-Ion Collisions: Measurements of $\phi$, $\omega$, $\rho^0$, and $J/\psi$ at STAR

The global spin alignment of particles produced in heavy-ion collisions can reveal valuable information about the strong force field and the properties of the quark-gluon plasma. The STAR collaboration recently observed a large global spin alignment of $\phi$-mesons in Au+Au collisions using the data from the first phase of the RHIC Beam Energy Scan program (BES-I) [1]. This cannot be explained by conventional mechanisms but may be attributable to the influence of vector meson force fields. In this contribution, we present new measurement of $\rho^0$ global spin alignment as a function of transverse momentum ($p_T$) and centrality for Au+Au, Ru+Ru, and Zr+Zr collisions at $\sqrt{s_{NN}}$ = 200 GeV. We discuss the implications of our results for the search for the Chiral Magnetic Effect, as the global spin alignment of $\rho^0$ mesons can effectively influence the measurement of charge separation across the reaction plane. Additionally, we present new precision and differential measurements of $\phi$-meson global spin alignment as a function of $p_T$, centrality, and rapidity (y) at $\sqrt{s_{NN}}$ = 7.7, 14.6, and 19.6 GeV, using higher-statistics data from the BES-II program. Furthermore, we have conducted a comparative study of the global spin alignment of $\phi(s,\bar{s})$, $\omega(u,\bar{u},d,\bar{d})$, and $J/\psi(c,\bar{c})$ through hadronic or leptonic decay modes in isobar collisions of Ru+Ru and Zr+Zr at $\sqrt{s_{NN}}$ = 200 GeV. These studies with more differential measurements and with vector mesons of various quark contents aim to understand the role of the strong field in nuclear structure and the evolution of nuclear matter. The addition of new particle species and measurements through previously unexplored decay channels can help understand the intricate effects of in-medium and hadronization mechanisms on global spin alignment.

Speaker: Baoshan Xi (Fudan University)

Baoshan_Xi-QM23_GlobalSpinAlignment_09052023-v17.pdf

09:50 A new stable and causal theory of viscous chiral hydrodynamics

Over the past decade, considerable research effort has focused on investigating macroscopic consequences of anomalies in quantum field theories. In particular, chiral matter is expected to exhibit novel transport phenomena arising from the interplay between quantum anomalies and electromagnetic and vortical fields [1]. In order to study these effects in fluid systems like the quark-gluon plasma formed in heavy-ion collisions, it is important to develop consistent theories of relativistic chiral hydrodynamics which capture the underlying anomaly and include dissipation. Attempts to develop such theories--even their dissipationless counterparts--have suffered from fundamental issues of acausality, instability, and ill-posedness of the initial value problem [2]. Following an effective field theory approach [3-7], we have constructed a first-order relativistic chiral hydrodynamic theory which is stable and causal within a range of values of transport coefficients. This is the first viscous theory of relativistic chiral hydrodynamics that can be used in numerical simulations of heavy-ion collisions.

[1] D. E. Kharzeev, J. Liao, S. A. Voloshin, G. Wang, Prog. Part. Nucl. Phys. 88 (2016) 1-28.
[2] E. Speranza, F. S. Bemfica, M. M. Disconzi, J. Noronha, Phys. Rev. D 107 (2023) 5, 054029.
[3] F. S. Bemfica, M. M. Disconzi, J. Noronha, Phys. Rev. D 98 (2018) 10, 104064.
[4] P. Kovtun, JHEP 10 (2019) 034.
[5] F. S. Bemfica, M. M. Disconzi, J. Noronha, Phys. Rev. D 100 (2019) 10, 104020.
[6] R. E. Hoult, P. Kovtun, JHEP 06 (2020) 067.
[7] F. S. Bemfica, M. M. Disconzi, J. Noronha, Phys. Rev. X 12 (2022) 2, 021044.

Speaker: Nick Abboud (University of Illinois at Urbana-Champaign)

nick_abboud__consistent_chiral_hydro__QM23.pdf

10:10 Search for the Chiral Magnetic and Vortical Effects Using Event Shape Variables in Au+Au Collisions at STAR

Effects from quark chirality in heavy-ion collisions probe the topological sector of Quantum Chromodynamics, where parity and charge-parity symmetries are violated locally in strong interactions. However, the experimental observables for the chiral magnetic/vortical effect (CME/CVE) are dominated by elliptic flow and nonflow backgrounds. Recent STAR isobar data revealed a substantial background in the CME observable that prevented an unambiguous observation of the difference between two isobars. The Au+Au system has significant advantages over the isobar collisions, such as the larger magnetic fields and the lower statistical fluctuations.

We improve the analysis method with event shape variables (ESV), and apply it to Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 7.7, 14.6, 19.6, 27, and 200 GeV in the search of the CME and CVE. After categorizing events based on ESV and extrapolating the CME/CVE observable towards zero flow limit, we report the $\Delta \gamma$ measurements using $h$-$h$ and $\Lambda$-$p$ correlations. To fully assess the possible CME signal, we employ a broad spectrum of observables and analysis techniques: with and without the particle pair information in constructing ESVs, utilizing invariant mass for differential studies, exploiting STAR Event Plane Detector and Zero-Degree Calorimeter to minimize nonflow backgrounds. We will discuss the physics implications on the beam energy dependence of the CME/CVE searches.

Speaker: ZHIWAN XU

QM2023_slides_CME_ZhiwanXu_v9.pdf

08:30 → 10:30 Collective Dynamics: (1)

Convener: Jun Takahashi (University of Campinas UNICAMP (BR))

08:30 Anisotropic flow of identifed particles in Au + Au collisions at $\sqrt{s_{NN}}$ = 3.0 - 19.6 GeV (remote)

Directed and elliptic flow ($v_{1}$, $v_{2}$) are sensitive to the dynamics of heavy-ion collisions at the early stage of the system evolution and the equation of state (EoS) of the medium. The $v_1$ slope ($dv_1/dy$) at mid-rapidity of net-baryons is expected to be sensitive to the first-order phase transition. Also, triangular flow ($v_3$) provides valuable information on the initial geometry fluctuations and transport properties of the medium. Studying these flow harmonics for various identified particles at different energies provides insights into the medium going through QCD phase transition. In particular, (multi-) strange hadrons with small hadronic cross-sections are cleaner probes of the early stages of heavy-ion collisions. A comprehensive study of light and (multi-) strange hadrons provides valuable insights into the subsequent stages of the medium evolution.

In this talk, the measurements of $v_1$, $v_2$, and $v_3$ for both light and (multi-) strange hadrons at $\sqrt{s_{NN}}$ = 3.0, 3.2, 3.5, 3.9, 7.7, 9.2, 11.5, 14.6, and 19.6 GeV, utilizing the enhanced capabilities of the STAR detectors and datasets with increased statistics from the second phase of the RHIC beam energy scan (BES-II) program, will be presented. The centrality dependence of anisotropic flow and the test of number of constituent quark (NCQ) scaling will be shown. Also, the energy and centrality dependence of $v_1$ slope and $p_T$-integrated $v_2$ will be discussed. The data will be compared with different model calculations, and the inferences on the QCD phase structure and EoS of nuclear matter in the high baryon density region will be discussed.

Speaker: Zuowen Liu

QM23_AnisotropicFlow_ZuowenLiu.pdf

08:50 Rapidity-dependent dynamics of the initial state via 3D multi-system Bayesian calibration

Most of our experimentally-driven knowledge about the early stages of a heavy-ion collision comes from analysis of measurements made near mid-rapidity. However, much information about the dynamics is encoded in rapidity-dependent behavior, and there exists a large amount of experimental data available to constrain this rapidity dependence. To leverage this information, we perform a systematic model-to-data comparison using three-dimensional hydrodynamic simulations of multiple collision systems --- large and small, symmetric and asymmetric, at different collision energies, from both RHIC and the LHC. Specifically, we perform fully 3D multi-stage hydrodynamic simulations initialized by a parameterized model for rapidity-dependent energy deposition [1] and we calibrate on a range of observables such as hadron multiplicity, anisotropic flow vectors, and mean transverse momentum --- including their rapidity-dependent fluctuations and correlations. We utilize Bayesian inference to constrain properties of the early- and late-time dynamics of the system, and further harness the results to do experimental design and study the effectiveness of various potential measurements (e.g. from upgraded detectors) at improving these constraints.

[1] C. Shen and B. Schenke, “Longitudinal dynamics and particle production in relativistic nuclear collisions,” Phys. Rev. C 105, no.6, 064905 (2022)
[arXiv:2203.04685].

Speaker: Andi Mankolli (Vanderbilt University (US))

Mankolli_QM23.pdf

09:10 Probing initial baryon stopping and equation of state with rapidity-dependent directed flow of identified particles

Using a (3+1)-dimensional hybrid framework with parametric initial conditions, we study the rapidity-dependent directed flow $v_1(y)$ of identified particles, including pions, kaons, protons, and lambdas in heavy-ion collisions. Cases involving Au+Au collisions are considered, performed at $\sqrt{s_{\rm NN}}$ ranging from 7.7 to 200 GeV. The dynamics in the beam direction is constrained using the measured pseudo-rapidity distribution of charged particles and the net proton rapidity distribution. Within this framework, the directed flow of mesons is driven by the sideward pressure gradient from the tilted source, and that of baryons mainly due to the initial asymmetric baryon distribution with respect to the beam axis driven by the transverse expansion. Our approach successfully reproduces the rapidity- and beam energy-dependence of $v_1$ for both mesons and baryons. We find that the $v_1(y)$ of baryons has strong constraining power on the initial baryon stopping, and together with that of mesons, the directed flow probes the equation of state of the dense nuclear matter at finite chemical potentials. We also provide predictions for the upcoming STAR Beam Energy Scan II measurements of the pseudo-rapidity dependent $v_1$ for charged particles at 27 GeV.

[1] L. Du, C. Shen, S. Jeon, and C. Gale, "Probing initial baryon stopping and equation of state with rapidity-dependent directed flow of identified particles", arXiv: 2211.16408.

Speaker: Lipei Du (McGill University)

QM 2023 - L Du.pdf

09:30 Elliptic anisotropy measurement of the $f_0(980)$ in pPb collisions and determination of its quark content by CMS

The $f_0(980)$ is a candidate exotic hadron, first observed by $\pi\pi$ scattering in the 1970’s. Its configuration still remains controversial— it can be a normal $s\bar{s}$ meson, a tetraquark $s\bar{s}q\bar{q}$ state, a $q\bar{q}g$ hybrid, or a $\mathrm{K}\bar{\mathrm{K}}$ molecule. Relativistic heavy ion collisions are in a unique position to identify the $f_0(980)$ quark content by the empirical NCQ (number of constituent quarks) scaling of elliptic flow $v_{2}$. In this talk, we present the first reconstruction of $f_0(980)$ via its main decay channel, $f_0(980) \to\pi^+\pi^-$, using proton-lead collisions recorded by the CMS experiment at 8.16 TeV. The $f_0(980)$ yield is studied as a function of the azimuthal angle relative to the event plane, reconstructed from the forward hadron calorimeters, to extract the $v_{2}$ parameter. The $v_{2}$ of the $f_0(980)$ is then compared to $v_{2}$ values from other hadrons to infer in a novel way the quark content of the $f_0(980)$.

Speaker: An Gu (Purdue University (US))

QM23_AnGu_HIN-20-002_9.pdf

09:50 Quenching minijets in a concurrent jet+hydro evolution and its consequences for extracting transport coefficients of QGP

Intermediate pT jets (minijets) are created by initial hard scatterings in heavy-ion collision experiments. They can constitute a significant portion of the particle multiplicity but do not lend themselves to hydrodynamic treatment as their transverse momenta are larger than the typical saturation scale of the bulk matter.Their orientation is independent of the underlying event and they can significantly reduce flow in the collective motion of the bulk medium. They also introduce an additional source of fluctuations.

We study minijets in a new jet+hydro concurrent framework where jet quenching leads to energy and momentum injection in the QGP. Minijets are sampled using PYTHIA and hydro is initialized using the IPGlasma framework. Both of these are concurrently evolved using MUSIC with the minijet quenching being governed by the Hybrid Model. Both the jet and thermal hadrons do hadronic cascade through UrQMD after the freezeout.

We find that this effort requires substantial recalibration of the transport coefficients in hydrodynamic simulations to explain the data. As extraction of transport properties is one of the major goals of the heavy-ion program, we posit that this significant contribution needs to be accounted for. We will also discuss the effect of these minijets on observables like pT-spectra, flow vn and correlations between different vn_s. We also look at the relation between initial state spatial anisotropy and the final state momentum anisotropy in the presence of minijets.

Speaker: Mayank Singh (University of Minnesota)

QM_2023_singh_mayank.pdf

10:10 Can we observe using the collective flow effects of the early nonequilirium dynamics

The early dynamics in heavy-ion collisions involves a rapid, far from equilibrium evolution. This early pre-equilibrium stage of the dynamics can be modeled using kinetic equations. The effect of this pre-equilibrium stage on final observables derived from transverse momenta of emitted particles is negligible. Therefore, the kinetic equations in the relaxation time approximation for a non-boost invariant system are solved (P.Bozek Phys.Rev.C 107 (2023) 034916). The asymmetry of the flow with respect to the reaction plane at different rapidities is found to be very sensitive to the degree of non-equilibrium in the evolution. This suggests that the rapidity odd directed flow is a sensitve probe of the occurrence of non-equilibrium effects and could be used to estimate the asymmetry of the pressure between the longitudinal and transverse directions. The study of kinetic evolution in the longitudinal direction allows also a modelling of the early pre-Bjorken flow stage of the equilibration.

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

kinQM.pdf

08:30 → 10:30 Critical Point: (1)

Convener: Nu Xu

08:30 Probing the nature of the QCD phase transition with higher-order net-proton number fluctuation and local parton density fluctuation measurements at RHIC-STAR

Higher-order cumulants ($C_n$) of net-baryon distributions are sensitive to the nature of the QCD phase transition. Recent lattice QCD calculations [1] suggest a negative $C_5/C_1$ and $C_6/C_2$ in the crossover regime at small baryon chemical potential ($\mu_B \leq$ 110 MeV). In addition, lattice QCD predicts a special ordering of cumulant ratios for systems of thermalized QGP [2]: $C_3/C_1 > C_4/C_2 > C_5/C_1 > C_6/C_2$. Both predictions can be tested in heavy-ion collision experiments by measuring higher-order cumulants of the net-proton multiplicity distributions.

In the high $\mu_B$ region of the QCD phase diagram, proton multiplicity distributions are utilized to probe characteristics of the phase transition. The variance of proton multiplicity within azimuthal subvolumes of phase space may provide insight into local parton density fluctuations. The deviation of this variance from a binomial baseline along with proton factorial cumulants over the full azimuth [3] may be observables sensitive to a possible first-order phase transition.

In this talk, we report measurements of net-proton $C_5/C_1$ and $C_6/C_2$ in Au+Au collisions with center-of-mass energies from 3 GeV to 200 GeV, where the 3 GeV data are from the fixed-target program and the other data sets are from the Beam Energy Scan program phase I at RHIC-STAR. Proton factorial cumulants and the variance of proton multiplicities in azimuthal partitions are also presented. The cumulant measurements are compared with a QCD-based FRG model, UrQMD, and HRG calculations as well as lattice QCD calculations. The AMPT and MUSIC+FIST models are used as non-critical references in the search for local density fluctuations.

[1] W.-j. Fu et al. \textit{Physical Review D} 104.9 094047 (2021).
[2] A. Bazavov et al. \textit{Physical Review D} 101.7 074502 (2020).
[3] A. Bzdak and V. Koch. \textit{Physical Review C} 100.5 051902 (2019).

Speaker: Dylan Neff

QM_Presentation_Neff.pdf

08:50 Critical Expectations: Non-Gaussian Cumulants of Particle Multiplicities Near the Critical Point

It has long been understood that non-monotonic variation of non-Gaussian cumulants of particle multiplicities as a function of decreasing collision energy and, hence, increasing baryon chemical potential $\mu_B$ can yield tell-tale signatures of the presence of a possible critical point in the QCD phase diagram. In this talk, we shall present quantitative estimates for the magnitude and $\mu_B$-dependence of the skewness and kurtosis of the proton multiplicity as a function of the separation $\Delta T$ between the temperature at a critical point and at freezeout. These provide a modern update of estimates first attempted in [1], for the first time including the effects of the change in the sign of the critical contribution to the kurtosis discovered in [2] in a way that incorporates the mapping between the universal physics around an Ising critical point onto the QCD phase diagram [3,4].

Several of us have recently quantified the reduction in the magnitude of the Gaussian cumulant of the proton multiplicity relative to equilibrium expectations, arising because both critical slowing down and baryon number conservation limit the growth of critical fluctuations [5]. In this talk, we describe how the dynamics in the critical regime (including critical slowing down and baryon number conservation) limit the growth of the non-Gaussian cumulants. It has been understood since they were first proposed as signatures of a critical point that dynamical effects make the actual cumulants much smaller than they would be in equilibrium; for the first time, we estimate how much smaller. We close by using the newly developed maximum entropy freezeout procedure [6] to make estimates of the magnitude of the skewness and kurtosis of proton multiplicity that can be expected in RHIC BES data if nature places a critical point near where these collisions freeze out.

[1] Athanasiou, Rajagopal, Stephanov, arXiv:1006.4636.
[2] Stephanov, arXiv: 1104.1627.
[3] Parotto et al, arXiv:1805.05249.
[4] Karthein et al, arXiv:2103.08146.
[5] Pradeep, Rajagopal, Stephanov and Yin, arXiv:2204.00639.
[6] Pradeep, Stephanov, arXiv:2211.09142.

Speaker: Maneesha Sushama Pradeep

QuarkMatter23_MPradeep.pdf

09:10 Femtoscopy analysis in small systems at NA61/SHINE

The recent measurements of femtoscopic correlations at NA61/SHINE, using small systems, unravel that the shape of the particle emitting source is not Gaussian. The measurements are based on alpha-stable symmetric L\'evy sources, and we discuss the average pair transverse mass dependence of the source parameters. One of the parameters, the L\'evy 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 endpoint of the phase diagram.

Moreover, 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 beam momentum (13A-150(8)A GeV/c) or by changing the collision system (p+p, p+Pb, Be+Be, Ar+Sc, Xe+La, Pb+Pb). This method enables to perform a two-dimensional scan of the phase diagram of QCD. Investigating HBT correlations are related to the critical exponent $\eta$, describing the spatial correlation. The search in the collisions reveals the properties of sQGP and possible signs of the critical endpoint.

Speaker: Barnabas Porfy (Wigner Research Centre for Physics (Wigner RCP) (HU))

Levy_HBT_QuarkMatter23_BP_NA61.pdf

09:30 Baryon number fluctuations at high baryon density (remote)

Calculations of baryon number fluctuations up to the sixth order at finite temperature and density in Ref.[1] have been extended to regime of high baryon chemical potentials with 400 MeV $\leq \mu_B\leq 700$ MeV. A peak structure is found for the dependence of the kurtosis of baryon number distributions, i.e., $R^{B}_{42}=\chi^{B}_{4}/\chi^{B}_{2}$, on the collision energy in a range of 3 GeV $\leq\sqrt{s_{\mathrm{NN}}}\leq 7.7$ GeV [2]. The computation is done within the functional renormalization group approach with a critical end point located at around $(T,\,\mu_B)_{\mathrm{CEP}}\sim(100,\,640)$ MeV in the phase diagram, which is in agreement with recent estimates from first-principle QCD calculations. Errors of calculated results arising from, e.g., the chemical freeze-out curves, locations of CEP, effects of baryon number conservation at low collision energy etc., have been evaluated in detail.

Reference:
[1] Wei-jie Fu, Xiaofeng Luo, Jan M. Pawlowski, Fabian Rennecke, Rui Wen, Shi Yin, Phys. Rev. D 104, 094047, 2021, arXiv: 2101.06035 [hep-ph].
[2] Wei-jie Fu, Xiaofeng Luo, Jan M. Pawlowski, Fabian Rennecke, Shi Yin, in preparation.

Speaker: Prof. Wei-jie Fu (Dalian University of Technology)

QM2023-WeijieFu.pdf

09:50 Location of the QCD critical point predicted by holographic Bayesian analysis

Predictions for the QCD critical point are made using Bayesian inference techniques within the holographic gauge/gravity correspondence. For that, we employ a Einstein-Maxwell-Dilaton (EMD) model capable of reproducing the latest lattice QCD results at zero and finite baryon density, known to predict a high-density critical endpoint. For the first time, we numerically find the posterior probability distribution for holographic model parameters from the lattice data at zero chemical potential, and extract their most likely values. This is possible thanks to new numerical developments which, by boosting the performance of our calculations, allow us to sample a large number of fits to the data via Monte Carlo methods. Thus, we find the maximum a posteriori estimate for the location of the critical point, as well as estimates for the corresponding statistical error bands. We determine the linear combination of model parameters which is the most relevant for these uncertainties and investigate its role for the equation of state at lower densities. Our analysis is performed for two competing model parametrizations, one of which may or may not present a critical point for samples of the prior distribution. We use the posterior distribution for this parametrization to infer the probability that a QCD critical point exists and is situated in a region of the phase diagram that can be probed by ongoing and future heavy ion collision experiments. Preliminary results favor a critical point around a baryon chemical potential of $570 - 650$ MeV and a temperature of $99 - 107$ MeV, with most of the uncertainty concentrated along a single line.

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

MauricioHippert_QM23.pdf

10:10 Spinodal enhancement of fluctuations in nucleus-nucleus collisions (remote)

Subensemble Acceptance Method (SAM) [1,2] is an essential link between measured event-by-event fluctuations and their grand canonical theoretical predictions such as lattice QCD. The method allows quantifying the global conservation law effects in fluctuations. In its basic formulation, SAM requires a sufficiently large system such as created in central nucleus-nucleus collisions and sufficient space-momentum correlations. Directly in the spinodal region of the First Order Phase Transition (FOPT) different approximations should be used that account for finite size effects. Thus, we present the generalization of SAM applicable in both the pure phases, metastable and unstable regions of the phase diagram [3]. Obtained analytic formulas indicate the enhancement of fluctuations due to crossing the spinodal region of FOPT and are tested using molecular dynamics simulations. A rather good agreement is observed. Using transport model calculations with interaction potential we show that the spinodal enhancement of fluctuations survives till the later stages of collision via the memory effect [4]. However, at low collision energies the space-momentum correlation is not strong enough for this signal to be transferred to second and third order cumulants measured in momentum subspace. This result agrees well with recent HADES data on proton number fluctuations at $\sqrt{s_{NN}}=2.4$ GeV which are found to be consistent with the binomial baseline of non-interacting hadrons [5]. It indicates that the large fluctuations observed in HADES data do not signal the presence of phase transition and their origin is yet to be identified. We suggest a crosscheck of this picture based on calculating the correlation between proton multiplicities in two non-overlapping rapidity intervals.

[1] V.Vovchenko, O.Savchuk, R.P., M.I.Gorenstein, V.Koch, Phys.Lett.B 811 (2020) 024908.
[2] R.P. et al., Phys. Rev. C 102 (2020) 024908.
[3] V.Kuznietsov, O.Savchuk, R.P., V.Vovchenko, M.I.Gorenstein, H.Stoecker, 2303.09193 (2023)
[4] O.Savchuk, R.P., A.Motornenko, J.Steinheimer, M.I.Gorenstein, V.Vovchenko, Phys. Rev. C 107 (2023) 2, 024913
[5] O.Savchuk, R.P., M.I.Gorenstein, Phys.Lett.B 835 (2022) 137540

Speaker: Dr Roman Poberezhnyuk (Bogolubov Institute for Theoretical Physics)

RPoberezhnyuk-QM2023.pdf

08:30 → 10:30 Heavy Flavor: (1)

Convener: Pol Gossiaux

08:30 Recent charmonium measurements in Pb-Pb collisions with ALICE (remote)

Charmonia have long been recognized as a valuable probe of the nuclear matter in extreme conditions, such as the strongly interacting medium created in heavy-ion collisions and known as quark-gluon plasma (QGP). At LHC energies, the regeneration process due to the abundantly produced charm quarks, was found to considerably affect measured charmonium observables. Comprehensive production measurements of charmonia, including both ground and excited states, are crucial to discriminate among different regeneration scenarios assumed in theoretical calculations. Charmonia can also be sensitive to the initial state of the heavy-ion collision. In particular, their spin-alignment can be affected by the strong magnetic field generated in the early phase, as well as by the large angular momentum of the medium in non-central collisions. The determination of the component originating from beauty hadron decays, known as non-prompt charmonium, grants a direct insight into the nuclear modification factor of beauty hadrons, which is expected to be sensitive to the energy loss experienced by the ancestor beauty quarks inside the QGP. Furthermore, once it is subtracted from the inclusive charmonium production, it allows for a direct comparison with prompt charmonium models.

In this contribution, newly published results of inclusive J/$\psi$ production, including yields, average transverse momentum and nuclear modification factors, obtained at central and forward rapidity in Pb--Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV, will be presented. At midrapidity, newly published measurements of prompt and non-prompt J/$\psi$ production will also be shown. Recently published results obtained at forward rapidity in Pb--Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV will be discussed. These include, among others, the $\psi$(2S)-to-J/$\psi$ (double) ratio and the $\psi$(2S) nuclear modification factor, as well as the J/$\psi$ polarization with respect to a quantization axis orthogonal to the event-plane. Results will be compared to available model calculations.

Speaker: Xiaozhi Bai (University of Science and Technology of China (USTC))

QM23_xbai_v5.pdf

08:50 Studies of heavy quark dynamics using B mesons with the CMS experiment

Heavy quarks are one of the most powerful probes to study the properties of quark-gluon plasma. We present new results on nuclear modification factors of $\mathrm{B}_\mathrm{s}^{0}$ and $\mathrm{B}^{+}$ mesons, using proton-proton (pp) and lead-lead (PbPb) data recorded with the CMS detector in 2017 and 2018, respectively. The measured B meson nuclear modification factors over an extended transverse momentum range provide important information about the diffusion of beauty quarks and the flavor dependence of in-medium energy loss. In addition, understanding the hadronization mechanism is crucial for extracting the transport properties of the QGP. The $\mathrm{B}_\mathrm{s}^{0}/\mathrm{B}^{+}$ yield ratio in pp and PbPb can thus shed 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 $\mathrm{B}_\mathrm{c}^{+}$ meson in PbPb collisions. Given the low production cross-section in pp collisions, its production could be significantly enhanced by the recombination of beauty with charm quarks present in the hypothesized medium, providing additional insights into the recombination mechanism.

Speaker: Tzu-An Sheng (Massachusetts Institute of Technology)

qm2023_ta.pdf

09:10 Probe parton propagation in heavy-ion collisions with ALICE heavy-flavour measurements (remote)

Heavy quarks (charm and beauty) are valuable probes for investigating the properties of the quark-gluon plasma (QGP) formed in ultra-relativistic heavy-ion collisions, as they are mainly produced through hard-scattering processes prior to the formation of the QGP, and their number is conserved during the subsequent QGP evolution. Measurements of the nuclear modification factor $R_{\rm AA}$ of charm and beauty hadrons allow the characterisation of the in-medium energy loss of heavy quarks while traversing the QGP. Information on their diffusion and degree of participation in the medium collective motion can be obtained by measuring the elliptic-flow coefficient $v_2$ of heavy-flavour particles. Complementary insights into heavy-quark fragmentation and energy redistribution can be obtained by measuring angular correlations involving heavy-flavour particles.
In this contribution, the newly published results on the non-prompt $v_2$ coefficient of D$^0$ mesons in Pb--Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV will be shown and compared to measurements of prompt D-meson $v_2$ in the same system. These will be supplemented by recent results of the $v_2$ of heavy-flavour decay muons in p--Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV, providing new insights into possible collective effects in smaller systems. The recent final results of the heavy-flavour decay electron $R_{\rm AA}$ in Pb--Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV will also be reported, together with measurements of prompt and non-prompt D mesons and $\Lambda_{\rm c}^{+}$ baryons. New Pb-Pb results of angular correlations of heavy-flavour decay electrons with charged particles in the same collision system will also be discussed. In view of a better understanding of the in-medium heavy-quark dynamics, the reported ALICE measurements will be compared to predictions from models including different implementations of heavy-quark interaction and hadronisation with the QGP constituents.

Speaker: Ravindra Singh (Indian Institute of Technology Indore (IN))

Heavy_Flavour_Physics_ALICE.pdf

09:30 Measurements of charm quark production and hadronization at CMS

The study of charm quark hadrons is an important probe to the processes of hadronization of heavy quarks. More specifically, we present results on the production of $\Lambda_\mathrm{c}$ baryon, the nuclear modification factors ($R_\mathrm{AA}$), and the $\Lambda_\mathrm{c}/\mathrm{D}^{0}$ yield ratios at $\sqrt{s_{_{\mathrm{NN}}}} = 5.02$~TeV in proton-proton (pp) collisions and in different centrality regions in lead-lead (PbPb) collisions, using data recorded with the CMS detector in 2017 and 2018, respectively. The reported $R_\mathrm{AA}$ for $\Lambda_\mathrm{c}$ provides useful information regarding the energy loss mechanism of charm quark in the quark-gluon plasma. Its $p_\mathrm{T}$-dependence is similar to that of other charm and beauty hadrons but with its minimum shifted towards higher $p_\mathrm{T}$. Comparing the $\Lambda_\mathrm{c}/\mathrm{D}^{0}$ production ratio in pp and PbPb collisions suggests that coalescence as an hadronization process is not significant for $p_\mathrm{T} > 10$~GeV/c. The ratio becomes comparable to the measurements in $\mathrm{e^{+}e^{-}}$ collisions for $p_\mathrm{T} > 30$~GeV/c. We also present results of the $\Lambda_\mathrm{c}$ baryon and $\mathrm{D}^{0}$ meson production and their ratios in proton-lead (Pb) collisions at $\sqrt{s_{_{\mathrm{NN}}}} = 8.16$~TeV as a function of $p_\mathrm{T}$ and final-state multiplicity using the data recorded by the CMS experiment in 2016. We do not observe any significant multiplicity dependence for the baryon over meson ratio for charm hadrons. The difference between the results from charm quarks and that from light quarks, based on a previous study, suggests coalescence processes of heavy quarks saturate earlier than those of light quarks.

Speaker: Soumik Chandra (Purdue University (US))

Soumik_Chandra_Measurement_of_charm_quark_QM2023.pdf

09:50 Heavy quark momentum diffusion coefficient during hydrodynamization via effective kinetic theory

We compute the heavy quark momentum diffusion coefficient $\kappa$ using QCD effective kinetic theory for a system going through bottom-up isotropization until approximate hydrodynamization. This transport coefficient describes heavy quark momentum diffusion in the quark-gluon plasma and is used in many phenomenological frameworks, e.g. in the open quantum systems approach. Our extracted nonthermal diffusion coefficient matches the thermal one for the same energy density within 30%. At large occupation numbers in the earliest stage, the transverse diffusion coefficient dominates, while the longitudinal diffusion coefficient is larger for the underoccupied system in the later stage of hydrodynamization.

Speaker: Jarkko Peuron (University of Jyväskylä)

QM23_Jarkko_Peuron.pdf

10:10 Bottom hadro-chemistry in $pp$ and PbPb collisions at the LHC (remote)

The hadro-chemistry of bottom quarks produced in hadronic collisions encodes valuable information on the mechanism of color-neutralization in these reactions. We first compute the chemistry of bottom-hadrons in high-energy $pp$ collisions employing statistical hadronization with a largely augmented set of states beyond the currently measured spectrum. This enables a comprehensive prediction of fragmentation fractions of weakly decaying bottom hadrons for the first time and a satisfactory explanation of the existing measurements in $pp$ collisions at the LHC. Utilizing the bottom hadro-chemistry thus obtained as the baseline, we then perform transport simulations of bottom quarks in the hot QCD matter created in PbPb collisions at the LHC energy and calculate the pertinent bottom-hadron observables. We highlight the transverse momentum ($p_T$) dependent enhancement of the ratios (relative to their $pp$ counterparts) between different species of bottom hadrons ($\bar{B}_s^0/B^-$, $\Lambda_b^0/B^-$ and $\Xi_b^{0-}/B^-$) as a result of bottom quark diffusion and hadronization in the Quark-Gluon Plasma (QGP).

Reference: Min He and Ralf Rapp, arXiv: 2209.13419

Speaker: Min He (Nanjing University of Science & Technology)

M.He_QM23.pdf

08:30 → 10:30 Jets: (1)

Convener: Mateusz Ploskon (Lawrence Berkeley National Lab. (US))

08:30 Identifying jet observables which can see the short-length structure of QGP

Quark-gluon plasma, which is a strongly coupled liquid at its natural length scales, must at the same time feature weakly coupled quark and gluon quasiparticles that appear only in hard processes that can resolve its short-length structure. In particular, high-energy partons in a jet shower can scatter off, and kick, the quark and gluon quasiparticles within a droplet of QGP when these Moliere scattering processes occur with a large enough momentum transfer. Here, we implement this physics within the hybrid strong/weak coupling model for jets in heavy ion collisions.

Throughout its evolution within the expanding cooling droplet of QGP, the shower of jet and recoil partons inject energy and momentum into the QGP, producing wakes. The large impact of the wakes generated by the hydrodynamic response of the medium on jet observables makes finding distinctive signatures of scattering off QGP quasiparticles challenging.

The hybrid model is particularly valuable for identifying observables that are more/less sensitive to consequences of scattering off quasiparticles and less/more sensitive to consequences of wakes in the QGP because when we turn Moliere scattering off the model contains no effects of scattering — energy loss in the model arises from strongly coupled physics, not from scattering.

We show that jet shapes and fragmentation functions are more sensitive to the contribution of the wake to the reconstructed, and identify various groomed jet observables (eg soft drop splitting angle, leading $k_T$, and girth) that are insensitive to this contribution and that show reasonable sensitivity to scattering off quasiparticles, with those in gamma-jet events of particular interest. We also investigate Z-hadron correlation observables and Z-jet acoplanarity observables constructed with the winner-take-all definition of the jet direction. We construct several promising observables from inclusive subjets within jets, and show that Moliere scattering increases the number of subjets and yields subjets which are more widely distributed and more widely separated. These observables are unaffected by the wake; they are directly sensitive to “sprouting a new subjet”, the intrinsic feature of Moliere scattering which makes its effects different from those of the wake.

Speaker: Prof. Krishna Rajagopal (Massachusetts Inst. of Technology (US))

Rajagopal_QM23_Sept_5_2023.pdf

Rajagopal_QM23_Sept_5_2023.pdf

Rajagopal_QM23_Sept_5_2023.pdf

08:50 Scanning the initial jet production points with dijet tomography in heavy-ion collisions

Jet energy loss and transverse momentum broadening are controlled by the jet transport coefficient $\hat{q}$ in the QGP medium. Specifically, jet energy loss correlates with jet propagation length, while transverse momentum asymmetry caused by the gradient of $\hat{q}$ depends on the initial transverse coordinates. We study both the longitudinal and transverse jet tomography in dijet events by triggering the leading jet propagating along the direction of the event plane in heavy-ion collisions. Simulations are performed using the linear Boltzmann transport model with event-by-event 3+1D viscous hydrodynamic backgrounds. We find that the initial jet production positions in the transverse plane can be simultaneously located by combining the dijet transverse momentum imbalance $x_{J} = p^\mathrm{subleading}_{T} / p^\mathrm{leading}_{T}$ and jet transverse momentum asymmetry perpendicular to the initial jet directions for different leading jet $p_{T}$ regions. The jet tomography can be used to scan the initial jet production positions and to study jet quenching observables in detail, such as the medium-modified jet shape and jet fragmentation functions.

Speaker: Dr Yayun He (South China Normal University)

Dijet_Tomography_YayunHe.pdf

09:10 Looking for the dead-cone in heavy-ion collisions with energy correlators (remote)

In this talk we use the recently introduced energy correlator framework for jet substructure in heavy-ion collisions to show how the radiation pattern of heavy quarks is modified by the presence of the QGP. We present an analytical calculation of the medium-modified 2-point energy correlator of a heavy quark jet determining how the dead-cone is populated by medium-induced radiation. We identify two regimes: the near-massless limit where the deadcone is not affected by the QGP, and the large-mass limit where the in-medium radiation begins to fill the deadcone. This study provides the first illustration of the ability of energy correlators to disentangle complicated competing jet dynamics.

Speaker: Ian James Moult

09:30 ATLAS measurements of $b$-jet suppression and heavy-flavor azimuthal correlations in 5.02 TeV Pb+Pb collisions

The suppression of jets in heavy-ion collisions can provide detailed information about 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. For light partons, energy loss via gluon bremsstrahlung is expected to dominate, while for heavy-quark-initiated jets, collisional energy loss may play a more important role. This energy loss mechanism can be studied by measuring differences in the suppression of $b$-tagged and inclusive jets in $pp$ and Pb+Pb collisions. Besides the $b$-tagged jet measurements, an alternative method for probing the interactions of heavy quarks with the plasma is the study of the correlations between heavy-quark pairs, which is sensitive to the relative importance of collisional versus radiative scattering processes. In this talk, we report new ATLAS measurements of $b$-tagged and inclusive jet production as well as the measurement of the yield of correlated muon pairs from heavy-flavor decays in Pb+Pb and $pp$ collisions at $\sqrt{s_\textrm{NN}}~=~5.02$~TeV. For $b$-tagged and inclusive jet, the transverse momentum distributions in Pb+Pb and $pp$ collisions, as well as the nuclear modification factors, $R_{AA}$, in Pb+Pb collisions, are presented together with comparisons to theoretical calculations. The measurement of correlated muon pairs from heavy-flavor decays includes per-event yields, scaled by the nuclear thickness function, $T_{AA} $ will be discussed. Detailed studies of how the shape of the correlation in azimuthal-angle separation between the two muons changes from peripheral to central Pb+Pb collisions and comparison to the corresponding measurements in $pp$ collisions are also presented.

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

sickles_090523.pdf

09:50 Revealing the medium-recoil effect with high-$p_\mathrm{T}$ Z boson tagged underlying event distribution in PbPb collisions at CMS (remote)

Extensive studies of dijet momentum balance, inclusive jet shapes, and photon-tagged jet fragmentation functions have revealed a significant contribution of low transverse momentum ($p_\mathrm{T}$) particles to the energy momentum balance of dijet and photon-jets. Effects such as medium-induced radiation and medium response could contribute to the enhancement of low-$p_\mathrm{T}$ particles. In this presentation, we utilize the Z boson reconstructed within the dimuon channel, which does not interact with the quark-gluon plasma (QGP) throughout the decay chain before interacting with the detector. Moreover, Z bosons are high precision probes, and their reconstruction does not introduce bias into the underlying event distribution near them, unlike the isolation requirement of photons. This feature enables the selection of a single quark-enriched high-$p_\mathrm{T}$ parton and study the modification of the underlying events associated with this probe. We present the first measurement of the Z boson-tagged underlying event spectra over a large acceptance with respect to the Z boson, using lead-lead data recorded by the CMS detector at 5.02 TeV. This new result can provide an unambiguous signal of the medium-recoil effect, and it could be sensitive to the equation of state and the speed of sound of the QGP.

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

pinchun_QM23.pdf

10:10 Measurements of the jet axis decorrelation and the groomed jet radius with photon-jet events in PbPb and pp collisions at the CMS experiment

Previous analyses have shown a narrowing effect in the inclusive jet substructure. While this narrowing effect could be a result of jet quenching, it could also be caused due to a selection bias by which very quenched and broader jets are filtered out from the considered jet transverse momentum window. Photon-tagged jets, which correspond to a quark-enriched sample, can significantly reduce this potential selection bias and the effect coming from the change in the quark versus gluon fraction. They also allow for a selection on the degree of quenching. In this presentation, we show new photon-tagged jet results using proton-proton and lead-lead collisions at $\sqrt{s_{_{\mathrm{NN}}}} = 5.02$~TeV recorded with the CMS detector in 2017 and 2018, respectively. We present the decorrelation of jet axes calculated with energy-weighted and winner-take-all recombination schemes and compare the results between photon-tagged jets and inclusive jets. We also explore the modification of the groomed jet radius and angularity in PbPb collisions relative to pp collisions for jets that have lost up to 60\% of their initial energy in the medium. The findings of these studies will contribute to a better understanding of the quark-gluon plasma and its properties.

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

QM2023-Molly-Park.pdf

10:30 → 11:00 Coffee Break

11:00 → 13:20 Collective Dynamics: (2)

Convener: James Lawrence Nagle (University of Colorado Boulder)

11:00 Establishing the Range of Applicability of Hydrodynamics in High-Energy Collisions

We simulate the space-time dynamics of high-energy collisions based on a microscopic kinetic description, in order to determine the range of applicability of an effective description in relativistic viscous hydrodynamics [1,2]. We find that hydrodynamics provides a quantitatively accurate description of collective flow when the average inverse Reynolds number $\mathrm{Re}^{−1}$ is sufficiently small and the early pre-equilibrium stage is properly accounted for. By determining the breakdown of hydrodynamics as a function of system size and energy, we find that it is quantitatively accurate in central lead-lead collisions at LHC energies, but should not be used in typical proton-lead or proton-proton collisions, where the development of collective flow can not accurately be described within hydrodynamics.

[1] V.E. Ambruș, S. Schlichting, C. Werthmann. To appear in Phys.Rev.D, arXiv: 2211.14379 [hep-ph]
[2] V.E. Ambruș, S. Schlichting, C. Werthmann. Phys.Rev.Lett. 130 (2023) 152301, arXiv: 2211.14356 [hep-ph]

Speaker: Clemens Werthmann (University of Wroclaw)

QM2023-Werthmann.pdf

11:20 Elliptic and triangular flow of light (anti-)nuclei in Au+Au collisions in the BES-II energies using the STAR detector (remote)

The formation of light nuclei in heavy-ion collisions can be explained by two models: the thermal model and the coalescence model. The thermal model proposes that light nuclei originate from a thermal source where they are in equilibrium with other particles in the fireball. However, due to their low binding energies, the formed nuclei are unlikely to survive the high-temperature conditions of the fireball. In contrast, the coalescence model suggests that light nuclei are formed later in time by the coalescence of protons and neutrons near the kinetic freeze-out surface. The final-stage coalescence of nucleons would lead to the mass number scaling, where the anisotropic flow of light nuclei scaled by their mass numbers follows closely the anisotropic flow of nucleons. Therefore, comparing the anisotropic flow of light nuclei with protons will help us experimentally test the coalescence model hypothesis. Moreover, compared to elliptic flow ($v_2$), triangular flow ($v_3$) of light nuclei has a better sensitivity to the fluctuating initial conditions as well as the properties of the created systems. This information will provide us with tighter constraints on the theoretical models that describe the production mechanism of light nuclei.

In this talk, we will present the transverse momentum ($p_T$) and centrality dependence of $v_2$ and $v_3$ of $d$, $t$, and $^3$He, as well as their corresponding antinuclei, in Au+Au collisions at energies of $\sqrt{s_{NN}} = 7.7$ -- 54.4 GeV from the Beam Energy Scan phase II (BES-II) program at RHIC-STAR. We will discuss the mass number scaling study of $v_2$ and $v_3$ of light nuclei in the BES-II energies. Additionally, we will compare the experimental results with model calculations that use specific initial conditions and/or nucleon coalescence.

Speaker: Rishabh Sharma (Indian Institute of Science Education and Research (IISER) Tirupati)

qm23_rishabh.pdf

11:40 Measuring flow harmonics up to order 10 and net-charge fluctuations in PbPb collisions with the CMS experiment

This talk presents a measurement of higher order flow harmonics with order number up to 10 in lead-lead (PbPb) collisions at $\sqrt{s_{_{\mathrm{NN}}}} = 5.02$~TeV, using data collected by the CMS experiment. Higher order flow harmonics probe the initial geometry of heavy ion collisions as well as the viscous damping of flow coefficients during the evolution of the quark-gluon plasma (QGP). By extending the study of flow harmonics to higher orders, we can access information about the QGP's transport properties that is complementary to existing measurements. In this talk, we will present the centrality dependence of flow harmonics up to order 10 and compare them to theory calculations and previous measurements at lower orders. Additionally, we will report the net-charge fluctuations with a pseudorapidity separation up to $\Delta\eta$ = 4.8 in PbPb collisions. All the results presented here provide new precision in probing the sensitivity of initial-state fluctuations and viscosity of the QGP, and deepen our understanding of the collective behavior of the strongly interacting matter.

Speaker: Shengquan Tuo (Vanderbilt University (US))

QM2023_Tuo_Final.pdf

12:00 What carries baryon number? Simulations of baryon and electric charge stopping in isobar collisions.

It is a fundamental question to understand what is the effective carrier of conserved quantum charges inside a proton at high energy. The net baryon and electric charge rapidity distributions in relativistic heavy-ion collisions can elucidate how different
conserved charges are transported along the longitudinal direction during the collision. Recent preliminary measurements in isobar collisions at the Relativistic Heavy Ion Collider (RHIC) show that the scaled net-baryon to net-electric charge number ratio at midrapidity ($B/\Delta Q * \Delta Z/A$) is between 1.2 and 2, in line with predictions from the string junction model. This measurement is compatible with the picture where the baryon number is carried by gluon junctions. In this work, we develop a comprehensive (3+1)D relativistic hydrodynamic framework with multiple conserved charge currents. We employ the 3D MC-Glauber model for the initial conditions, which allows for modeling baryon stopping separately from electric charge stopping within the string junction picture. Simulating the coupled propagation of net baryon and electric charge currents including the charge-dependent lattice-QCD-based equation of state, we study how net baryon and electric charges are evolved during different stages of heavy-ion collisions. We make predictions of net baryon and net electric charge rapidity distributions for Ru+Ru and Zr+Zr collisions at $\sqrt{s_\mathrm{NN}}=200$ GeV, which can be compared with STAR measurements.

Speaker: Gregoire Pihan

PIHAN_QM2023_3.pdf

12:20 Thermalization of QGP through transverse momentum fluctuation in ultra-central Pb+Pb collision

We report the first direct evidence of thermalization of the Quark-Gluon Plasma (QGP) formed in ultra-relativistic heavy-ion collision, by studying the fluctuation of mean transverse momentum per particle ($\langle p_t \rangle$) in ultra-central Pb+Pb collision. The recent experimental data from the ATLAS collaboration at the Large Hadron Collider (LHC), provides measurement of variance of $\langle p_t \rangle$ at fixed multiplicity ($N_{ch}$) and a steep fall of the variance is observed over a narrow range of $N_{ch}$, for most of the central collision events (Fig. 14 and 15, \href{https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2021-01/}{ATLAS : HION-2021-01}). Such a behaviour cannot be reproduced by previously existing models, such as HIJING which treats Pb+Pb collisions as a superposition of independent nucleon-nucleon collisions. However, our model results can accurately reproduce the peculiar pattern in the variance of $\langle p_t \rangle$ that is observed by ATLAS. To explain such a novel phenomenon, we argue that at a given multiplicity, the impact parameter ($b$) fluctuation plays an important role; the transverse momentum per particle increases with the increasing impact parameter. A larger $b$ corresponds to a smaller collision volume resulting in a higher density. In relativistic thermodyanimcs, a higher density corresponds to a higher initial temperature which implies a larger energy per particle leading to a larger $\langle p_t \rangle$. Thus at a fixed $N_{ch}$, a higher $\langle p_t \rangle$ at a larger b is the effect of the thermalization of the system at a higher temperature. To illustrate this point further, we provide results for Pb+Pb collision from hydrodynamic simulation with TRENTO + MUSIC at b=0 and compare with corresponding HIJING results. From the hydro results, we find a very strong correlation between $\langle p_t \rangle$ and $N_{ch}$ at fixed impact parameter, which is not observed in HIJING where there is no thermalization. The strong correlation is the consequence of the thermalization that is assumed in the hydro simulation.
( R. Samanta, S. Bhatta, J. Jia, M. Luzum and J-Y Ollitrault, \href{https://arxiv.org/pdf/2303.15323.pdf}{arXiv: 2303.15323} )

Speaker: Rupam Samanta (AGH University of Science and Technology, Krakow, Poland and Institute of Theoretical Physics, CEA, Paris-Saclay University, Gif-sur-Yvette, France)

QM2023_Rupam.pdf

12:40 Longitudinal Decorrelation Measurements from pp to A+A with the ATLAS detector

This talk presents a measurement of longitudinal decorrelation in $pp$ collisions with ATLAS. The deposited energy in the transverse $(x,y)$ plane is expected to vary, 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 $4.0<|\eta_\mathrm{ref}|<4.9$. 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 (Columbia University (US))

BSeidlitz_Decor_QM23_v1.pdf

13:00 Chasing the onset of QCD thermalisation with ALICE

Deciphering the process of hadronization has long been a formidable challenge, in part due to its non-perturbative nature. Over the years, various phenomenological models have emerged, all attempting to unravel the complexity of hadron production. Despite their different theoretical foundations, many of these models successfully account for the average yield of hadrons. This has spurred the scientific community to search for innovative observables capable of discerning the fundamental principles governing these models. In pursuit of this goal, the ALICE Collaboration has studied an extensive array of event-by-event Pearson correlations between hadrons with distinct quantum numbers. Conducting a system size scan of these measurements unveils a powerful means to identify and analyze emerging QCD phenomena in small collision systems. In this presentation, ALICE will show the latest findings on antiproton--antideuteron and net-kaon--net-Xi correlations in various collision systems (pp, p--Pb, and Pb--Pb). These observables offer the advantage of being unaffected by resonance or weak decays. The measurements will be compared to various hadronization models, delving into the intriguing topic of the onset of thermalization in QCD matter. The measured correlations are used to estimate the correlation volume between hadrons stemming from the conservation of baryon and strange quantum numbers.

Speaker: Mario Ciacco (Politecnico di Torino and INFN Torino (IT))

QM23_strangeness_fluctuations_v5.pdf

11:00 → 13:20 Heavy Flavor: (2)

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

11:00 Heavy Flavor and Quarkonia results from the PHENIX experiment

The PHENIX experiment at RHIC has a unique large rapidity coverage (1.2$<|\eta|<$2.2) for heavy flavor studies in heavy ion collisions. This kinematic region has a smaller particle density and may undergo different nuclear effects before and after the hard process when compared to mid-rapidity production. The latest PHENIX runs contains a large data set which allows, for the first time, the study of heavy flavor and J/$\psi$ flow at the large rapidity region in Au+Au collisions at $\sqrt{s_{NN}}=$200 GeV. This measurement has the potential to reveal a medium evolution distinct from the one known at the mid-rapidity. This presentation will also report on the analysis status of non-prompt J/$\psi$ coming from B-meson decays at mid-rapidity in $pp$ collisions. This data can reach very low $p_{\rm T}$ B-mesons yields which is typically challenging to be described by pQCD calculations.

Speaker: Krista Lizbeth Smith (Los Alamos National Laboratory (US))

QM_2023_PHENIX_v4.pdf

11:20 Measurements of Charm Quark Interaction with the QGP in Heavy-Ion Collisions at STAR

Heavy flavor quarks (charm and bottom), produced in the early stages of heavy-ion collisions, serve as excellent probes to study the properties of the Quark-Gluon Plasma (QGP). When traversing the medium, charm quarks suffer from `jet quenching' thanks to the interactions with the QGP. It can manifest as degradation of charm quark energy and modifications to the fragmentation pattern, both of which are predicted to depend on parton flavor and quark mass. The energy loss can be quantified by comparing yields of charmed mesons or tagged charm jets in heavy-ion collisions to those in $p$+$p$ collisions. On the other hand, medium-induced modifications to the jet shower can be studied using the jet fragmentation function, i.e., the transverse momentum ($p_{\rm T}$) fraction of the jet carried by hadrons along the jet axis ($z = \vec{p}_{\rm T, hadron}\textbf{.}\hat{p}_{\rm T, jet}/|\vec{p}_{\rm T, jet}|$).

In this contribution, we report the first measurement of the $\rm D^{0}$ meson production yield at mid-rapidity ($|y| < 1$) in isobar collisions (Ru+Ru and Zr+Zr) at $\sqrt{s_{\text{NN}}} = 200 \text{ GeV}$, with the STAR experiment at RHIC. We present nuclear modification factors as a function of $p_{\rm T}$ for different centrality classes, and compare them to similar measurements in Au+Au collisions at $\sqrt{s_{\text{NN}}} = 200 \text{ GeV}$. We complement the $\rm D^{0}$ meson studies with measurements of $\rm D^{0}$ meson tagged jets in Au+Au collisions at $\sqrt{s_{\text{NN}}} = 200 \text{ GeV}$. For the first time, we show measurements of charm jet fragmentation function in heavy-ion collisions at RHIC, and the nuclear modification factor as a function of $z$. Additionally, we report the yield modifications of $\rm D^{0}$-tagged jets as a function of $p_{\rm T}$ and the radial profile of the $\rm D^{0}$ mesons in these tagged jets. These reported measurements can help constrain theoretical calculations of parton flavor, parton mass and system size dependencies of parton interactions with the QGP.

Speaker: Yuan Su (University of Science and Technology of China)

QM_09052023_YuanSu.pdf

11:40 Beam energy dependence of heavy flavor production in Au+Au collisions at STAR

Quarkonia and open heavy-flavor hadrons are important probes to study the properties of the quark-gluon plasma (QGP) created in heavy-ion collisions. Heavy quarks (charm and bottom) are primarily generated at initial hard platonic scatterings and undergo the whole QGP evolution. Therefore, they are excellent probes of the QGP properties.Production of quarkonia depends on the dissociation and regeneration processes in the QGP, and also on the cold nuclear matter effect. To disentangle these effects and infer QGP properties, it is important to carry out differential precision measurements for various quarkonium states at different collision energies and system sizes. The STAR experiment offers opportunity to study the energy and colliding system size dependence of heavy-flavor production through large statistics samples of isobaric collisions ($^{96}_{44}{\rm Ru}+^{96}_{44} \rm Ru$ and $^{96}_{40}{\rm Zr}+^{96}_{40}{\rm Zr}$) at $\sqrt{s_\mathrm{NN}}$ = 200 GeV, as well as Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 14.6, 19.6, 27 GeV and 54 GeV collected in the phase II of Beam Energy Scan program.

In this talk, the first measurements of $\psi(2\rm{S})$ and $J/\psi$ polarization in heavy-ion collisions at RHIC, performed in isobaric collisions, will be presented. Centrality and transverse momentum dependence of the ratio of $\psi(2\rm{S})$ yield over that of $J/\psi$ will be shown. These results together with measurements of the $J/\psi$ and $\Upsilon$ states yield suppression allow a comprehensive study of binding energy dependent modifications to the quarkonium production in the medium. $J/\psi$ polarization measurement provides a new angle for studying QGP properties and the $J/\psi$ production mechanism. New measurments of inclusive $J\psi$ production in Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 14.6, 19.6 and 27 GeV will be also presented. Furthermore, measurements of central-to-peripheral nuclear modification factors (R$_{\rm CP}$) and elliptic flow ($v_2$) of HFE in Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 54.4GeV will be shown.

Speaker: Yan Wang (University of Science and Technology of China)

QM_2023_Yan_final.pdf

12:00 Quarkonia as probes of initial and final states in small systems with ALICE (remote)

Measurements in pp and p--Pb collisions, so-called small systems, besides serving as baseline for studying vacuum production and cold-nuclear matter effects, respectively, have recently shown intriguing features. In particular, measurements in high-multiplicity events have revealed striking similarities with heavy-ion collisions, where the formation of a quark-gluon plasma is expected. One of the possible scenarios proposed for describing these findings, which include among others collective effects, is the presence of multiple parton-parton interactions (MPIs). At LHC energies, MPIs affect both the soft component of the event, as well as the hard scales responsible for heavy-quark production. Quarkonium associated production, such as double J/$\psi$ production in the same event, provides a direct way to study MPIs. Conversely, quarkonium measurements which correlate soft and hard components of the event, such as multiplicity dependent production or azimuthal correlations between quarkonia and hadrons produced in the same event, represent an indirect method to investigate MPIs. In addition, these studies can reveal any other potential underlying mechanisms taking place in the final state, such as possible dissociation effects for loosely bound excited quarkonia. In case of charmonia, the corresponding measurements for the non-prompt component, originating from beauty hadron decays, allows for extending such correlations studies to the open beauty hadron sector.

In this talk, new published measurements of double J/$\psi$ production at forward rapidity, as well as new preliminary multiplicity dependent measurements of non-prompt J/$\psi$ fractions at midrapidity, in pp collisions at $\sqrt{s}$ = 13 TeV, will be shown. Recent multiplicity dependent measurements of $\psi$(2S) and $\Upsilon$($n$S) states ($n$ = 1,2,3), along with excited-to-ground state ratios, carried out at forward rapidity in pp and p--Pb collisions at $\sqrt{s}$ = 13 TeV and $\sqrt{s_{\rm NN}}$ = 8.16 TeV, will be presented. Furthermore, recently published prompt and non-prompt J/$\psi$ production at midrapidity in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 8.16, will be discussed. The status of ongoing analyses on J/$\psi$ production as a function of multiplicity or spherocity at central and forward rapidity, in pp and p--Pb collisions, will also be shown. Results will be compared to available model calculations.

Speaker: Subikash Choudhury (Department of Atomic Energy (IN))

QM-2023-presentation-subikash-v6.pdf

12:20 Modification of heavy quark hadronization in high multiplicity collisions at LHCb (remote)

The differences in hadron chemistry observed at e+e- machines versus hadron
colliders may indicate that the mechanisms by which partons evolve into visi-
ble matter are not universal. In particular, the presence of many other quarks
produced in the underlying event may affect the hadronization process. With
full particle ID, precision vertexing, and a high rate DAQ, the LHCb detector
is uniquely well suited to study the hadronization of heavy quarks. This con-
tribution will present LHCb data on hadronization of heavy charm and bottom
quarks, including the first results on the b baryon-to-meson production ratio
versus charged particle multiplicity.

Speaker: Chenxi Gu (Centre National de la Recherche Scientifique (FR))

QM2023_ChenxiGu.pdf

12:40 New LHCb results on quarkonia production in pp and pPb collisions

Modifications of quarkonia production in hadronic collisions provide an im-
portant experimental observable that sheds light on the heavy quark interaction
with the nuclear medium. In small collision systems, quarkonia can suffer from
a combination of initial and final state effects such as shadowing and comover
breakup, and possible effects from a deconfined medium. The excited ψ(2S)
state, with a relatively low binding energy, is especially sensitive to these ef-
fects. In this contribution, we will present new LHCb results on J/ψ and ψ(2S)
production in high-multiplicity pp and in pPb collisions, along with comparisons
to the latest theoretical models.

Speaker: Cesar Luiz Da Silva (Los Alamos National Laboratory (US))

quarkonia-LHCb-QM23.pdf

quarkonia-LHCb-QM23.pptx

13:00 Heavy Flavor machine learning algorithms for Fast Data Processing in sPHENIX

Major high-energy nuclear and particle experiments are challenged by the processing of large volumes of high precision data generated by sophisticated detectors in high-rate collisions, e.g., experiments at RHIC and LHC. To address this challenge, state-of-the-art real-time AI technology is being developed using modern deep neural networks and AI-centric hardware innovations. Supported by the DOE Office of Science Nuclear Physics AI-Machine Learning initiative program, this project aims to process extremely high-rate data streams from the tracking detectors of the upcoming sPHENIX experiment at RHIC by integrating real-time readouts and the intelligent control system that accelerates AI inference with FPGA hardware. This design allows us to collect rare heavy-flavor events with high efficiency in the high rate p+p collisions of O(10) MHz with much limited DAQ bandwidth at 15kHz. The developed approach includes high efficiency heavy-flavor trigger algorithms in the Graph Neural Network framework trained by full sPHENIX p+p collision simulation data, the optimized conversion of AI models into Firmware using the hls4ml package developed by the HEP community, and the deployment of real-time AI technologies on the powerful FELIX-711(712) boards with the Xilinx Kintex Ultrascale FPGA. The successful deployment of AI-based real-time data streaming and reduction at sPHENIX will have significant and immediate impacts: minimizing the computation resources and accelerating the end-to-end pipeline from experiments to physics discovery. Our project delivers a demonstrator that brings essential benefits to a key science driver of the sPHENIX experiment and enables comprehensive studies of heavy-flavor production in p+p and p+Au collisions. Furthermore, this technique and experience can be applied in other fields where high throughput data streams and real-time detector control are required, including the future EIC experiments. This talk presents the progress of the design and implementation of the AI-intelligent heavy-flavor triggering system for sPHENIX, showcasing the potential of AI and FPGA technologies in revolutionizing real-time data processing pipelines for high-energy nuclear and particle experiments.

Speaker: Cameron Dean (Massachusetts Inst. of Technology (US))

HF_SPHENIX_CDean_20230905.pdf

11:00 → 13:20 Jets: (2)

Convener: Dr Xin-Nian Wang (Lawrence Berkeley National Lab. (US))

11:00 Parton cascades at DLA: the role of the evolution variable

While experimental studies on jet quenching have achieved a large sophistication, the theoretical description of this phenomenon still misses some important points. One of them is the interplay of vacuum-like emissions, usually formulated in momentum space, with the medium induced ones that demand an interface with a space-time picture of the medium and thus must be formulated in position space. A unified description of both vacuum and medium-induced emissions is therefore lacking.
In this work, we build a toy Monte-Carlo parton shower ordered in formation time, virtual mass, and opening angle, representing equivalent formulations at leading logarithmic accuracy. Aiming at a link with jet substructure, we compute the Lund Plane distributions and trajectories for each ordering prescription. We also compute the distributions in number of splittings and final partons, with the goal of clarifying the differences in shower evolution to be expected from the different ordering variables. Further, we investigate the sensitivity of ordering prescriptions to medium effects by counting the number of events obeying a decoherence condition.

Speaker: André Cordeiro

QM2023 André Cordeiro.pdf

11:20 Exploring medium properties and evolution with ALICE using correlated, groomed, and reclustered jet substructure

The study of jet substructure in heavy-ion collisions provides multiple tools for incisive exploration of jet-medium interactions and the mechanisms underlying jet quenching. Some results, however, remain disjoint: the jet mass and jet angularities, including girth and thrust, are strongly-correlated observables that have given seemingly conflicted answers on the angular quenching of jets traversing the QGP. ALICE has carried out new systematic measurements of these and other perturbatively-calculable angularities using consistent definitions for the first time, resolving the long-standing girth-mass problem, and revealing quenching effects at broad angles. Concurrently, applying soft drop grooming isolates the narrowing in the core of quenched jets. Grooming can also be employed to resolve medium scattering centers, with varying methods to focus on regions of the splitting phase space.
We present the first application of dynamical grooming in heavy-ion collisions to search for excess $k_{\mathrm{T,g}}$ emissions as a signature of point-like scatters, providing new constraints on searches for in-medium Molière scattering. We also present a new approach for studying jet-medium opacity, based on a time-like rather than angular perspective. By employing a new time reclustering strategy, we potentially enable a time-dependent study of jet substructure observables. We compare all results to assorted jet quenching models, providing new critical information on medium evolution as a function of angular, momentum, and time structure.

Speaker: Hannah Bossi (Massachusetts Inst. of Technology (US))

HBossi_QuarkMatter_2023.pdf

11:40 New measurements of inclusive jet $R_{\rm AA}$ with mixing technique and jet $v_2$ properties with ALICE

This talk presents new measurements of inclusive jet yield suppression and correlation with event-plane orientation to elucidate the kinematic and path-length dependence of jet energy loss due to quenching. We report measurements of the inclusive charged-particle jet yield in central Pb--Pb collisions, with the large uncorrelated background mitigated using a novel event mixing technique. This approach extends the jet $R_{\rm AA}$ to lower jet $p_{\mathrm T}$ than previously achievable, providing significant kinematic overlap with RHIC jet measurements.
In addition to explorations of the low-$p_{\rm T}$ frontier, we report the inclusive charged-particle jet $v_2$ in semi-central Pb--Pb collisions, thereby quantifying the yield dependence relative to the event-plane orientation and probing the pathlength dependence of jet energy loss. We also report more differential measurements of this azimuthal dependence by using event-shape engineering to select specific event topologies, and the jet substructure observable $R_{\rm g}$ to select specific jet topologies. Such measurements improve our understanding of how jet suppression depends on both medium and jet properties.
These results are compared to theoretical calculations, thus providing new insights into jet-quenching phenomenology and its underlying mechanisms.

Speaker: Nadine Alice Gruenwald (Heidelberg University (DE))

QM2023_NadineGruenwald.pdf

12:00 Readiness of the sPHENIX experiment for jet physics

sPHENIX is a new collider detector at RHIC designed for pioneering studies of the Quark-Gluon Plasma with high-p$_T$ jet and heavy flavor probes. The jet physics program particularly relies on the sPHENIX calorimeter system, which consists of large-acceptance, hermetic electromagnetic and hadronic sections designed for high-resolution measurements of photons, electrons, hadrons, and jets. sPHENIX will begin commissioning with Au+Au collisions at 200 GeV in Spring 2023, with a large expected luminosity for measurements of jet production, structure, and correlations from the first year of data-taking. This talk will first give a technical report of the sPHENIX sub-systems relevant for jet physics and then present the status of the first physics measurements.

Speaker: Timothy Thomas Rinn (Brookhaven National Laboratory)

trinn_QM_2023.pdf

12:20 Photon-triggered jets as probes of multi-stage jet modification

Prompt photons are created in the early stages of heavy ion collisions and traverse the QGP medium without any interaction. Therefore, photon-triggered jets can be used to study the jet quenching in the QGP medium. In this work, photon-triggered jets are studied through different jet and jet substructure observables for different collision systems and energies using the JETSCAPE framework. Since the multistage evolution used in the JETSCAPE framework is adequate to describe a wide range of experimental observables simultaneously using the same parameter tune, we use the same parameters tuned for jet and leading hadron studies. The same isolation criteria used in the experimental analysis are used to identify prompt photons for better comparison. For the first time, high-accuracy JETSCAPE results are compared with multi-energy LHC and RHIC measurements to better understand the deviations observed in prior studies. These JETSCAPE results are used to predict upcoming sPHENIX results. This study highlights the importance of multistage evolution for the simultaneous description of experimental observables through different collision systems and energies using a single parameter tune.

Speaker: Chathuranga Sirimanna

PhotonTriggeredJets_v2.pdf

12:40 Quantum to classical parton evolution in the QGP

We study the time evolution of the density matrix of a high energy quark in the presence of a dense QCD background that is modeled as a stochastic Gaussian color field. At late times, we find that only the color singlet component of the quark’s reduced density matrix survives the in-medium evolution and that the density matrix becomes asymptotically diagonal in both transverse position and momentum spaces. In addition, we observe an accelerated entropy growth due to the larger phase space being explored by the quark and that the quantum and classical quark entropies converge at late times. We further observe that the quark state loses all memory of the initial condition. Combined with the fact that the reduced density matrix satisfies Boltzmann-diffusion transport, we conclude that the quark reduced density matrix can be interpreted as a classical phase space distribution. Finally, we comment on how this approach can offer a generic way to study parton evolution in the QGP and establish a strong connection to initial stage physics.

Speaker: João Barata

Barata_QM23.pdf

13:00 Isolating final state effects in high $p_T$ $\pi^0$ production using direct photons in small system collisions with PHENIX

PHENIX observed a 20\% suppression in the production of high $p_T$ neutral pions
in the most central (0-5\%) $d+$Au collisions at 200 GeV. Through the simultaneous measurement of high $p_T$ direct photons ($\gamma^{dir}$) and $\pi^0$ production for event samples selected by event activity, the final state effects could be disentangled from cold-nuclear-matter effects and event-selection biases that are inherent in using the standard Glauber model. This isolation of final state effects is achieved by approximating the nuclear modification factor by the double ratio $R_{xA}=(\gamma^{dir}/\pi^{0})_{pp}/(\gamma^{dir}/\pi^{0})_{xA}$. While the cold-nuclear-matter effects in $x+$A collisions cancel in the ($\gamma^{dir}/\pi^{0})_{xA}$ ratio, the effective number of binary collisions is given by $N_{\mathrm{coll}}^{\mathrm{exp}} = \gamma^{dir}_{xAu}/\gamma^{dir}_{pp}$, which eliminates the dependence on the Glauber model. In addition, many systematic uncertainties cancel in the double ratio. To shed light on the origin of the observed final state suppression and to test if it is consistent with energy loss in droplets of QGP, the results from $d+$Au collisions are compared to preliminary data from smaller ($p+$Au) and larger ($^3$He$+$Au) collision systems.

Speaker: Daniel Firak

QM talk_DanielFirak_version2_3.pdf

11:00 → 13:20 Light Flavor: (1)

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

11:00 Strangeness production in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 14.6, 19.6, and 200 GeV with the STAR experiment

One main motivation of the Beam Energy Scan (BES) program at RHIC is to search for the QCD critical point and the onset of deconfinement. Strangeness production has been suggested as a sensitive probe to the early dynamics of the deconfined matter created in heavy-ion collisions. Ratios of particle yields involving strange particles are often utilized to study various properties of the nuclear matter, such as the strangeness and baryon chemical potentials at the chemical freeze-out temperature ($\mu_S/T_{\mathrm{ch}}$ and $\mu_B/T_{\mathrm{ch}}$).

Measurements from the first phase of the BES program have indicated potential changes in the medium properties with decreasing collision energy. However, the precision of those measurements is not sufficient to draw definitive conclusions. During BES phase-II (BES-II), STAR has accumulated high statistics data in Au+Au collisions at various energies, which can help reduce the uncertainties in the strange hadron measurements, in particular for the multi-strange hadrons. Benefiting from the iTPC upgrade, the strangeness measurements are now extended from mid-rapidity (|y|<0.5) to a larger rapidity range (|y|<1.0) as well. In this talk, we will present new STAR measurements of strange hadron ($K_s^0$, $\Lambda$, $\bar{\Lambda}$, $\Xi$, $\bar{\Xi}$, $\Omega$, $\bar{\Omega}$) production in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 14.6, 19.6 GeV from BES-II and $\Omega$($\bar{\Omega}$) production in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV, including transverse-momentum and rapidity spectra, nuclear modification factors, baryon-to-meson and antibaryon-to-baryon ratios. New insights on the collision dynamics will be discussed.

Speaker: Yi Fang

QM2023_fangyiv8.pdf

11:20 Particle production and collective flow measurements with CMS Run 3 PbPb data (remote)

The pseudorapidity distributions and anisotropic flow coefficients of charged particles produced in heavy ion collisions are key observables that characterize the initial conditions and subsequent hydrodynamic evolution of the quark-gluon plasma. Recent LHC Run 3 lead-lead (PbPb) data collected at a center-of-mass per nucleon pair of $\sqrt{s_{_{\mathrm{NN}}}} = 5.36$~TeV allow the study of these effects at a record collision energy. We present the first measurements of the midrapidity charged particle $\mathrm{d}N/\mathrm{d}\eta$ as a function of collision centrality, as well as the Fourier harmonics, $v_{2}$ and $v_{3}$, with two- and four-particle correlations in PbPb collisions recorded at $\sqrt{s_{_{\mathrm{NN}}}} = 5.36$~TeV with the CMS experiment. Taken together, these measurements constrain models of the collision-energy and centrality-dependence of charged particle production, and also shed light on the initial collision geometry and importance of event-by-event fluctuations. These data are compared to similar measurements at different energies, including PbPb collisions at $\sqrt{s_{_{\mathrm{NN}}}} = 5.02$ and xenon-xenon collisions at $\sqrt{s_{_{\mathrm{NN}}}} = 5.44$~TeV.

Speaker: Jing Wang (CERN)

20230905_QM_dNdeta_JingWang.pdf

11:40 Exploring the internal structure of exotic resonances with ALICE

The investigation of the quark content of hadrons has been a major goal of non-perturbative strong interaction physics. In the last decade, several resonances in the mass range 1000-2000 MeV/$c^2$ have emerged that cannot be explained by the quark model. The internal structure of exotic resonances such as $\rm f_0$, $\rm f_1$, and $\rm f_2$ is currently unknown. Different scenarios are possible ranging from two-quark, four-quark, molecule, a hybrid state, or glueballs. A modification of the measured yields of these exotic hadrons in A--A and p--A collisions as compared to pp collisions has been proposed as a tool to investigate their internal structure.

The excellent particle identification capabilities of the ALICE detector along with the large data sample collected in pp and p--Pb collisions provide an opportunity for multi-differential studies of such high-mass resonances. In this presentation, the first-ever measurement of $\rm f_1$ production in pp collisions and measurements of $\rm f_0$ and $\rm f_2$ production both in pp and p--Pb collisions will be presented. The measurements of their mass, width, and yields will be presented and their sensitivity to the internal structure of these exotic resonances will be discussed. These results will pave the way for future experimental investigations on the internal structure of other exotic hadrons.

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

Exotic_Resonances_Sonali.pdf

12:00 Anomalous kaon correlations measured in Pb-Pb collisions at the LHC as evidence for the melting and refreezing of the QCD vacuum

Measurements of the dynamical correlations between neutral and charged kaons in central Pb-Pb collisions at $\sqrt{s_{NN}} = 2.76$ TeV by the ALICE Collaboration display anomalous behavior relative to conventional heavy-ion collision simulators. We consider other conventional statistical models, none of which can reproduce the magnitude and centrality dependence of the correlations. The data can be reproduced by coherent emission from domains which grow in number and volume with increasing centrality. We study the dynamical evolution of the strange quark condensate and show that the energy released during the expansion and cooling of the system may be sufficient to explain the anomaly.

Speaker: Joseph Kapusta

Kapusta_QM2023.pdf

12:20 Exploring the hadron gas phase of relativistic heavy-ion collisions with ALICE (remote)

Hadronic resonances have typical lifetimes that are comparable to that of the hadron gas phase created in the late stages of high-energy nuclear collisions. Therefore, a significant fraction of resonances decays inside a high-density medium and their decay daughters may rescatter with other hadrons destroying their initial kinematic correlations. A competing effect is resonance regeneration via pseudo-elastic interactions of hadrons. The interplay between these effects, which may modify the measured yields and transverse-momentum spectra of hadronic resonances, can be studied by measuring the yield ratio of resonances to the corresponding long-lived particle as a function of the hadronic lifetime, i.e. charged-particle multiplicity. In addition, measurements of the differential yields of resonances with different masses, quark content, and quantum numbers help in understanding particle production mechanisms, strangeness production, and parton energy loss.

In this presentation, recent measurements of hadronic resonances in Pb--Pb and Xe--Xe collisions as a function of multiplicity will be presented. Collisions between Xe nuclei provide the ultimate test for validating the picture of the smooth evolution of hadronic rescattering across different collision systems by filling the gap between p--Pb and Pb--Pb multiplicities. Furthermore, the measured resonance yields in Xe--Xe and Pb--Pb collisions are used as an experimental input in a partial chemical equilibrium-based thermal model to constrain the kinetic freeze-out temperature. This is a novel procedure that is independent of assumptions on the flow velocity profile and the freeze-out hypersurface.

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

[05062023]NAgrawal_QM_Resonance_ALICE_v4.pdf

12:40 Shedding light on light flavour particle production in small systems at the LHC with ALICE

Measurements of light flavour particle production in small collision systems at the LHC energies have shown the onset of features (e.g. radial flow) that resemble what is typically observed in nucleus-nucleus collisions and attributed to the formation of a strongly interacting medium.
By performing more differential studies and analysing smaller fractions of the visible cross section the processes behind these unexpected phenomena can be more effectively studied and potentially understood.
In this talk, new results on light flavour particle production measured in high-multiplicity triggered events will be shown and compared with the particle production measured as a function of the underlying event activity.
In addition, thanks to its detector upgrade during LS2, from the beginning of the LHC Run 3 campaign ALICE has collected unprecedented high statistics of pp collisions from the lowest collision energy of $\sqrt{s}$ = 900 GeV to the highest collision energy ever achieved in the laboratory of $\sqrt{s}$ = 13.6 TeV. This mole of data, newly presented in this contribution, is used to complete the scan in multiplicity and collision energy of the light flavour particle production studies extending these measurements to the lowest collision energy available at the LHC.

Speaker: Francesca Ercolessi (Universita e INFN, Bologna (IT))

FErcolessi_QM2023.pdf

13:00 Bulk flow and correlation measurements at LHCb

Particle correlations are a powerful tool to study the properties of the bulk nu-
clear matter produced in relativistic heavy ion collisions. The momentum cor-
relations between identical particles originating from the same particle-emitting
source, referred to as the Bose-Einstein correlations, measure scales that are
related to the geometrical size of the source. The two-particle azimuthal angu-
lar correlations measure the spatial anisotropy of produced particles, providing
information on collective phenomena arising in the dense nuclear medium. This
contribution will discuss new LHCb measurements of Bose-Einstein correlations
and, for the first time, the collective flow coefficients in the far forward rapidity
region

Speaker: Cheuk Ping Wong (Brookhaven National Laboratory)

QM_LHCb_flow_CheukPingWong_v2.1.pdf

11:00 → 13:20 New Theory: (1)

Convener: Krishna Rajagopal (Massachusetts Inst. of Technology (US))

11:00 Testing Eigenstate Thermalization Hypothesis for Non-Abelian Gauge Theories

We report on progress in understanding thermalization in QCD at the full quantum level. Previous studies of thermalization of highly excited states in QCD, as they arise in heavy ion collisions, have either involved the (semi-)classical evolution of highly occupied gluon states or kinetic theory. Both approaches omit or approximate essential properties of quantum mechanical systems including coherence and entanglement. An alternative paradigm of understanding thermalization of an isolated quantum system is the eigenstate thermalization hypothesis (ETH), which states that matrix elements of local observables in the energy eigenstate basis are equal to the corresponding microcanonical ensemble values, up to random corrections that decrease exponentially with the system size. In this talk, we will show results of testing this hypothesis for the 2+1 dimensional SU(2) non-Abelian gauge theory on a lattice. The results indicate a subset of physical states in QCD also satisfy the ETH. We will then discuss physical implications of these results. Finally, the simplifications of the Hamiltonian formulation used in this work will be useful for future quantum simulations of non-Abelian lattice gauge theories.

Speaker: Xiaojun Yao (University of Washington)

qm23_ETH.pdf

11:20 Far-from-equilibrium slow modes and momentum anisotropy in expanding plasma

We discuss the evolution of initial momentum anisotropy in the early-stage quark-gluon plasma. We use kinetic theory to study the far-from-equilibrium evolution of an expanding plasma with an anisotropic momentum-space distribution. We identify slow and fast degrees of freedom in the far-from-equilibrium plasma from the evolution of moments of this distribution. At late times, the slow modes correspond to hydrodynamic degrees of freedom and are naturally gapped from the fast modes by the inverse of the relaxation time. At early times, however, there are an infinite number of slow modes. From the evolution of the slow modes we generalize the paradigm of the far-from-equilibrium attractor to vector and tensor components of the energy-momentum tensor, and even to higher moments of the distribution function that are not part of the hydrodynamic evolution. We predict that initial-state momentum anisotropy decays slowly in the far-from-equilibrium phase and may persist until the relaxation time.

Speaker: Jasmine Therese Brewer (CERN)

JasmineBrewer-QM2023.pdf

JasmineBrewer-QM2023.pdf

JasmineBrewer-QM2023.pptx

11:40 Non-Hydrodynamic Modes from Linear Response in Kinetic Theory

Viscous hydrodynamics serves as a successful mesoscopic description of the QGP produced in relativistic heavy-ion collisions. In order to investigate, how such an effective description emerges from the underlying microscopic dynamics we calculate the non-hydrodynamic and hydrodynamic modes of linear response in the sound channel from a first-principle calculation in kinetic theory. We do this with a new approach wherein we linearize and discretize the collision kernel to calculate eigenvalues directly. This allows us to study the Green's functions at any point in time or frequency space. Our study focuses on scalar theory with quartic interaction and we find that the analytic structure of Green's functions in the complex plane is far more complicated than just poles or cuts which is the first step towards an equivalent study in QCD kinetic theory.

Speaker: Stephan Ochsenfeld (Bielefeld University)

NonHydroModesOchsenfeld.pdf

12:00 Exploring the freeze-out hypersurface with a rapidity-dependent thermal model

The success of thermal models in extracting freeze-out parameters from particle yields near midrapidity is well known. However, it is essential to investigate their performance with rapidity-dependent measurements at low collision energies, where boost-invariance is expected to be strongly violated. In this study, we calibrate a (3+1)-dimensional multistage hydrodynamic framework using rapidity distributions of charged particles and net protons for Au+Au collisions at $\sqrt{s_{NN}}=7.7–200$ GeV. We observe significant rapidity dependences in thermodynamic properties at the hadronization process near the chemical freeze-out. The effects on the rapidity dependence of particle production due to longitudinal flow and system size are also highlighted. A rapidity-dependent thermal model is developed, incorporating the dynamical features of the multistage framework. We evaluate the performance of different thermal model scenarios in extracting the freeze-out profiles, using the rapidity-dependent yields of the multistage framework and comparing them to the hydrodynamic freeze-out hypersurface as a closure test [1]. Bayesian analysis is applied to constrain the longitudinal flow, system size in rapidity space, and thermodynamic properties for nuclear matter created at low beam energies. Our Bayesian model selection analysis reveals a longitudinal flow stronger than Bjorken in the experimental measurements as beam energy decreases. Our study provides a simple numerical approach for extracting rapidity-dependent thermodynamic parameters at freeze-out for low-beam energy collisions. Furthermore, analyzing freeze-out profiles through data-driven methods using this model offers quantitative guidance to computationally-demanding hybrid approaches [2].

[1] Lipei Du, Han Gao, Sangyong Jeon, and Charles Gale, “Rapidity scan with multistage hydrodynamic and statistical thermal models,” arXiv: 2302.13852.
[2] Han Gao, Lipei Du, Sangyong Jeon, and Charles Gale, “Constraining longitudinal dynamics and freeze-out thermodynamics with Bayesian Analysis in a hydrodynamics-inspired thermal model,” in preparation.

Speaker: Han Gao

hgao_qm2023.pdf

12:20 A solvable quantum field theory with asymptotic freedom in 3+1 dimensions

Wouldn't it be nice to solve large N QCD analytically? While QCD is hard, it is fairly easy to solve scalar field theories with many components, such as the O(N) model in the large N limit. Traditional wisdom has it that such theories are ill defined because they have the wrong beta function, possess a Landau pole, and are quantum trivial for N=1. In this talk, I throw out conventional wisdom, and critically re-examine scalar field theories in 4d, borrowing heavily from PT-symmetric field theory results. It's a solvable wonderland with asymptotic freedom, bound states in the infrared and a phase transition in between.

Speaker: Paul Romatschke

Paul_Romatschke_QM23.pdf

12:40 Non-Gaussian fluctuation dynamics in relativistic fluid near a critical point

We consider non-equilibrium evolution of non-Gaussian fluctuations crucial for the QCD critical point search in heavy-ion collision experiments. We rely on the hierarchy of relaxation time scales, which emerges in the hydrodynamic regime near the critical point. We focus on the slowest modes which are responsible for observable signatures of the critical point. We derive evolution equations for the non-Gaussian correlators of these modes applicable for an arbitrary relativistic hydrodynamic flow.
[1] X. An, G. Basar, M. Stephanov and H.-U. Yee, arxiv/2212.14029
[2] X. An, G. Basar, M. Stephanov and H.-U. Yee, work in progress

Speaker: Xin An (National Center for Nuclear Research)

XinAn_QM23.pdf

13:00 Excited Hadron Channels in Hadronization

The proper treatment of hadronic resonances plays an important role for many aspects of heavy ion collisions. We expect this to be the case also for hadronization, due to the large degeneracies of excited states, and the abundant production of hadrons from their decays. We show how a comprehensive treatment of excited meson states can be incorporated into quark recombination, and in extension, into Hybrid Hadronization. We discuss in detail the quantum mechanics of forming excited states, utilizing the Wigner distribution functions of angular momentum eigenstates of isotropic 3-D harmonic oscillators. We describe how resonance decays can be handled, based on a set of minimal assumptions, by creating an extension of hadron decays in PYTHIA 8. Finally, we present a study of hadron production by jets using PYTHIA and Hybrid Hadronization with excited mesons up to orbital angular momentum L=4. We find that states up to L=2 are produced profusely by quark recombination.

Speaker: Rainer Fries (Texas A&M University)

QM2023_RJFries.pdf

13:20 → 14:50 Lunch

14:50 → 17:10 EM Probes: (1)

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

14:50 Coherent J/$\psi$ photoproduction and polarization in peripheral Pb-Pb collisions with ALICE

Photonuclear reactions are induced by the strong electromagnetic field generated by ultrarelativistic heavy-ion collisions. These processes have been extensively studied in ultraperipheral collisions, in which the impact parameter is larger than twice the nuclear radius. In recent years, the observation of coherent J/$\psi$ photoproduction has been claimed in nucleus--nucleus (A--A) collisions with nuclear overlap, based on the measurement of an excess (with respect to hadroproduction expectations) in the very low transverse momentum ($p_{\rm{T}}$) J/$\psi$ yield. Such quarkonium measurements can help constraining the nuclear gluon distribution at low Bjorken-x and high energy. In addition, they can shed light on the theory behind photon induced reactions in A--A collisions with nuclear overlap, including possible interactions of the measured probes with the formed and fast expanding quark-gluon plasma. In order to confirm the photoproduction origin of the very low-$p_{\rm{T}}$ J/$\psi$ yield excess, polarization measurement is a golden observable. It is indeed expected that the produced quarkonium would keep the polarization of the incoming photon due to s-channel helicity conservation. ALICE can measure inclusive and exclusive quarkonium production down to zero transverse momentum, at forward rapidity (2.5 <$\it{y}$< 4) and midrapidity (|$\it{y}$|< 0.9). In this contribution, we will report on the new preliminary measurement of the $\it{y}$-differential cross section and the new first polarization analysis at LHC of coherently photoproduced J/$\psi$ in peripheral Pb--Pb collisions. Both measurements are conducted at forward rapidity in the dimuon decay channel. These results will be discussed together with the recent results on coherent J/$\psi$ photoproduction as a function of centrality at both mid and forward rapidities. Comparison with models will be shown when available.

Speaker: Afnan Shatat (Université Paris-Saclay (FR))

Afnan_Shatat_QMproceeding_LatestVersion.pdf

15:10 Thermal dilepton production in heavy-ion collisions at Beam Energy Scan (BES) energies

Dileptons are an invaluable tool for mapping out the phase diagram of QCD because they grant observational access to the entire space-time history of heavy-ion collisions. We calculate thermal dilepton yields from Au+Au collisions at BES energies -- $\sqrt{s_{NN}}$=7.7, 19.6, 27, 54.4, 62.4, 130, and 200 GeV -- using a realistic (3+1)-dimensional multistage dynamical framework. The underlying emission rates, which include baryon chemical potential dependence for the first time, are implemented from perturbation theory in a manner which smoothly interpolates between the strict next-to-leading order and the Landau-Pomeranchuk-Migdal regimes. By comparing the slope of the invariant mass spectrum with the average temperature of the fluid (at different evolution times), we assess the efficacy of this observable as a thermometer of the quark-gluon plasma (QGP). Furthermore, we are able to explore the capability of dileptons as a QGP `baryometer' via their sensitivity to the dynamical evolution and dissipation of baryon charge included in the simulations. We also investigate the correlation between the medium lifetime and the integrated dilepton yields in central and peripheral Au+Au collisions across the different beam energies. Finally, we compare the thermal dielectron invariant mass spectra with those from hadronic cocktail contributions and available STAR measurements. Our results provide a quantitative baseline for dilepton yields at BES energies and highlight the importance of this observable in probing features of QCD thermodynamics.

Speaker: Prof. Charles Gale

Gale__QM2023.pdf

15:30 Measurement of low $p_T$ direct photons with PHENIX

Photons provide snapshots of the evolution of relativistic heavy-ion collisions as they are emitted at all stages and do not interact with the medium strongly. Measurements of low momentum direct photons at PHENIX across different systems, from $p+p$, $p/d/^3$He$+$Au to Au$+$Au have been made possible due to the versatility of RHIC. An excess of direct photons, above prompt photon production from hard scattering processes and consistent with thermal photon emission is observed. The integrated yields scale as $(dN_{ch}/d\eta)^\alpha$, with $\alpha=1.12$, above multiplicities of 20-30. However, for systems with lower multiplicities, a gradual increase from $p+p$-like to $A+A$-like behavior is observed. In addition to the results for direct photon spectra for small and large collision systems, in this talk, azimuthal anisotropies of direct photons in Au$+$Au collisions at 200 GeV will also be presented, thereby, shedding light on the long-standing direct photon puzzle.

Speaker: Vassu Doomra (Stony Brook University)

Quark Matter 2023.pdf

15:50 Direct photon production and correlations in Pb--Pb collisions with ALICE

Measurements of direct photons provide valuable information on the properties of the quark-gluon plasma (QGP) because they are colour-neutral and created during all phases of the collision. Sources of photons include initial hard scatterings, Bremsstrahlung and the fragmentation process, jet-medium interactions, and radiation from the medium.

Direct thermal photons, produced by the plasma, are sensitive to the collective flow at photon production time. Their exponential spectral shape gives access experimentally to an effective medium temperature.
Furthermore, Bose-Einstein correlations can be used to study the space-time evolution of the medium created in heavy-ion collisions with Hanbury Brown and Twiss interferometry. The correlation function is sensitive to the source size and the direct photon fraction.

Direct prompt photons produced in hadronic collisions through annihilation and Compton processes have minimal event activity from the hard process, allowing the isolation method to suppress background photons from parton fragmentation and neutral meson electromagnetic decays.
Isolated photon measurements in pp and p--Pb collisions can constrain NLO pQCD predictions. Hadrons correlated with isolated photons are a promising channel to study the energy loss in heavy-ion collisions and to constrain the $Q^{2}$ of the initial hard scattering, obtaining information on the amount of energy lost by the parton recoiling off the photon.

The ALICE experiment reconstructs photons from conversion photons using its excellent tracking capabilities and directly in calorimeters. Combining these methods, ALICE can measure direct photons at mid-rapidity with transverse momentum from 0.4 GeV/$c$, where direct thermal photons should dominate until few GeV, then direct prompt photons take over and can be measured until about 100 GeV/$c$.
This talk presents ALICE measurements of direct-photon distributions using statistical (decay-photon subtraction, thermal photons) and isolation (prompt photons) methods in different collision systems and energies and their correlations.

Speaker: Carolina Arata (Centre National de la Recherche Scientifique (FR))

2023-06-27-16-55-Direct_Iso_PhotonV3.txt

QM23DirectPhotons_CarolinaArata.pdf

16:10 Electromagnetic radiation in pp and Pb--Pb collisions with dielectrons in ALICE

Electromagnetic probes such as photons and dielectrons (e$^{+}$e$^{-}$ pairs) 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 at all stages of the collision with negligible final-state interactions. At intermediate dielectron invariant mass ($m_{\rm ee} > 1$ GeV/$c^{2}$), thermal radiation from the quark-gluon plasma carries information about the early temperature of the medium. At LHC energies, it is however dominated by a large background from correlated heavy-flavour hadron decays. At smaller $m_{\rm ee}$, thermal radiation from the hot hadronic phase contributes to the dielectron spectrum via decays of $\rho$ mesons, whose spectral function is sensitive to chiral-symmetry restoration. Finally, at vanishing $m_{\rm ee}$, the real direct photon fraction can be extracted from the dielectron data. In pp collisions, such measurement in minimum bias events serves as a baseline and a fundamental test for perturbative QCD calculations, while studies in high charged-particle multiplicity events allow one to search for thermal radiation in small colliding systems. The latter show surprising phenomena similar to those observed in heavy-ion collisions.
In this talk, final ALICE results, using the full data sample collected during the LHC Run 2, will be presented. They include measurements of the dielectron and direct-photon production in central Pb--Pb at the centre-of-mass energy per nucleon pairs, $\sqrt{s_{\rm NN}}$, of 5.02 TeV, as well as of direct photons in minimum bias and high-multiplicity pp collisions at $\sqrt{s} = 13$ TeV. Finally, first results with the Run 3 pp data at $\sqrt{s} = 13.6$ TeV, using the upgraded ALICE detector to disentangle the different dielectron sources, will be reported.

Speaker: Daiki Sekihata (University of Tokyo (JP))

20230905_qm2023_sekihata_v9.pdf

16:30 Thermal dielectron measurements in Au+Au collisions at $\sqrt{s_{NN}}=$ 7.7, 14.6, and 19.6 GeV with the STAR experiment

Dielectrons emitted during the evolution of the hot and dense QCD medium created in relativistic heavy-ion collisions offer an effective way to probe the medium properties, as they do not interact via the strong force. The rate of the dielectron emission is proportional to the medium's electromagnetic spectral function. In the dielectron mass range from $400$ MeV/$c^{2}$ to $800$ MeV/$c^{2}$, the spectral function probes the in-medium $\rho$ meson propagator which is sensitive to the medium’s properties including the total baryon density and the temperature. Meanwhile, the low energy range of the spectral function provides information about the medium’s electrical conductivity. Therefore, by measuring thermal dielectron production, we can study the microscopic interactions between the electromagnetic current and the medium.

The STAR experiment has recorded large datasets of Au+Au collisions during the Beam Energy Scan Phase-II (BES-II) program, spanning center-of-mass energies ($\sqrt{s_{NN}}$) from 3.0 to 19.6 GeV with detector upgrades that benefit the dielectron measurement via extended transverse momentum and rapidity coverages as well as enhanced particle identification capability. In this talk, we will report on the measurements of thermal dielectrons produced in Au+Au collisions at $\sqrt{s_{\text{NN}}}=$ 7.7, 14.6, and 19.6 GeV using the STAR experiment.

Speaker: Yiding Han (Rice University)

QM2023_Yiding_v12.pdf

16:50 Measurement of dilepton and diphoton production from photon fusion processes in UPC in Pb+Pb collisions with the ATLAS detector

Relativistic heavy-ion beams at the LHC are accompanied by a large flux of equivalent photons, leading to multiple photon-induced processes. This talk presents a series of measurements of dilepton production from photon fusion performed by the ATLAS Collaboration. Recent measurements of exclusive dielectron production in ultra-peripheral collisions (UPC) are presented. These processes provide strong constraints on the nuclear photon flux and its dependence on the impact parameter and photon energy. Comparisons of the measured cross-sections to QED predictions from the Starlight and SuperChic models are also presented. Tau-pair production measurements can constrain the tau lepton's anomalous magnetic dipole moment (g-2), and a recent ATLAS measurement using muonic decays of tau leptons in association with electrons and tracks provides one of the most stringent limits available to date. Similarly, light-by-light scattering proceeds via loop diagrams, which can contain particles not yet directly observed. Thus, high statistics measurements of light-by-light scattering shown in this talk provide a precise and unique opportunity to investigate extensions of the Standard Model, such as the presence of axion-like particles.

Speaker: Peter Alan Steinberg (Brookhaven National Laboratory (US))

Steinberg_QM2023_v1.pdf

14:50 → 17:10 Initial State: (1)

Convener: Raju Venugopalan

14:50 Investigating the early magnetic field of QGP via heavy-flavour polarisation studies with ALICE

Heavy quarks, i.e. charm and beauty, are produced at the initial stage of heavy-ion collisions, on a time scale shorter than the medium formation time, and are sensitive to the large initial magnetic field produced perpendicular to the reaction plane (defined by the impact parameter direction and beam direction) in non-central heavy-ion collisions. In the presence of a large initial magnetic field, the charm quark can be polarised. The quark polarisation is expected to be transferred to the hadron in the hadronisation process. Experimentally, the heavy-flavour polarisation can be probed by measuring the spin density matrix element of spin 1 hadrons (as the $\rm{D}^{*+}$ meson). Any deviation of ρ00 parameter from ⅓ can be attributed to the spin alignment of $\rm{D}^{*+}$ meson.
We will present the first measurement of the $\rho_{00}$ parameter of $\rm{D}^{*+}$ meson in Pb–Pb collisions at $\sqrt{s_\mathrm{NN}}=5.02~$TeV, exploiting the large data sample collected by the ALICE Collaboration during the LHC Run 2 in 2018. A comparison with the $J/\psi$ polarisation measurement will also be reported to investigate the effect of the magnetic field. In this study, one of the main background sources is represented by the feed-down contribution from B-meson decays, as vector mesons which decay from scalar B mesons are expected to be longitudinally polarized due to the helicity conservation in weak decays. In this context, the final measurement of the spin alignment of prompt and non-prompt $\rm{D}^{*+}$ mesons in pp collisions at $\sqrt{s}= 13~$TeV, used to quantify the effect of the feed-down in the Pb–Pb measurements, will be presented.

Speaker: Luca Micheletti (CERN)

vector_meson_polarization_Luca_Micheletti_new.pdf

15:10 Limiting attractors in heavy-ion collisions --- the interplay between bottom-up and hydrodynamical attractors

We study the hydrodynamization process in the aftermath of ultrarelativistic heavy-ion collisions using effective kinetic theory simulations and different observables. For the pressure ratio $P_T/P_L$, we observe that its late-time evolution becomes universal in units of the kinetic relaxation time for sufficiently large couplings signaling the onset of a hydrodynamical attractor. In contrast, at weak couplings, it converges earlier to a bottom-up attractor in terms of the thermalization time scale $\tau_{\text{BMSS}} = \alpha_s^{-13/5}/Q_s$. We interpret these as two limiting attractors. The dynamics of the occupancy of hard modes, the heavy-quark diffusion coefficient, and the jet quenching parameter are better described by a bottom-up limiting attractor even for moderate couplings. Therefore, the previous conjecture that the hydrodynamical attractor governs the late-time approach toward hydrodynamization is not complete. Our results rather indicate that a weak coupling attractor emerges additionally in the coupling regime relevant for heavy-ion collisions for certain observables.

Speaker: Florian Lindenbauer (TU Wien)

qm2023_lindenbauer.pdf

15:30 First study of the initial gluonic fluctuations using UPCs with ALICE

Incoherent J/$\psi$ photoproduction is sensitive to fluctuations of the gluonic structure of the target. Thus, the measurement of $\rm{J/\psi}$ photoproduction off the colliding hadron sheds light on the initial state of QCD and provides important constraints on the initial conditions used in hydrodynamical models of heavy ion collisions. In this talk, we present the first measurement of the transverse momentum dependence of both coherent and incoherent $\rm{J/\psi}$ photoproduction in ultra-peripheral Pb-Pb collisions at mid-rapidity. These new results provide, for the first time, a clear indication of subnucleonic fluctuations of the lead target.

Speaker: Adam Matyja (Polish Academy of Sciences (PL))

QM_matyja_final1.pdf

15:50 Physics opportunities from nuclear structure studies with high-energy nuclear collisions

Hydrodynamic simulations of the quark-gluon plasma (QGP) permit us not only to gauge the transport properties of hot QCD matter from data, but also to constrain the conditions that set the stage for the formation of such matter. Recent measurements from RHIC and LHC demonstrate that the QGP initial condition is impacted by the shape and radial structure of the colliding nuclei. Based on a recent community white paper [1], we discuss physics opportunities for nuclear structure and QGP studies offered by high-energy nuclear collisions, with an emphasis on i) \textit{isobar collisions}, offering clean access to the structural properties of the colliding ions, as well as ii) collisions of bowling-pin-shaped 20Ne isotopes as a means to complement and broaden the hot QCD program envisaged via 16O+16O collisions. We argue that future experiments involving selected ion species will open new exciting directions of interdisciplinary research in nuclear science. Recent updates from the INT program [2] dedicated to this topic will also be covered.

[1] B. Bally \textit{et al.} ``Imaging the initial condition of heavy-ion collisions and nuclear structure across the nuclide chart,'' [arXiv:2209.11042 [nucl-ex]].

[2] "Intersection of nuclear structure and high‐energy nuclear collisions", 01/23/2023-02/24/2023, https://www.int.washington.edu/programs-and-workshops/23-1a

Speaker: Jiangyong Jia (Stony Brook University (US))

JiangyongJia_QM2023_v3.pdf

16:10 Adiabatic Hydrodynamization: a Natural Framework to Find and Describe Prehydrodynamic Attractors

One of the main challenges in the theory of heavy ion collisions is understanding how an initial state of two highly Lorentz-contracted nuclei acquires the features of a hydrodynamic plasma in a characteristic time of 1 fm/c. Arguably, the most successful descriptions of this out-of-equilibrium stage have been established by finding so-called “attractor” solutions in the various (simplified) theories that attempt to capture out-of-equilibrium dynamics of QCD. These attractors are characterized by a loss of sensitivity to the initial conditions, which is achieved because the kinetic theory is dynamically driven to a preferred “attractor surface” in the phase space of the theory, often well before hydrodynamization in weakly coupled kinetic theory.

In this context, the adiabatic hydrodynamization framework [1,2] is a promising candidate to describe and characterize attractors in a model-independent formulation. In principle, all that needs to be done is to establish the dominance of an effective ground state in the dynamics of the system. This was done analytically in [2] for the first stage of the bottom-up thermalization scenario [3], demonstrating a dynamical reduction in the number of active degrees of freedom much earlier than the hydrodynamic regime. A key observation made in [2] was that such effective ground states may require a time-dependent change of coordinates for their dominance to be manifest. Ultimately, such a change of coordinates is one of the defining characteristics of the sought attractor solution, and therefore it becomes imperative to define a procedure to find the “optimal” coordinate transformation for a given theory. In this talk, we will lay out a candidate for such a procedure and will consider the example of collision-driven dynamics in the Bjorken-expanding kinetic theory of a dilute gluon gas to demonstrate the effectiveness of this method to describe attractor solutions. We will then lay out the path to explore more realistic descriptions of the expanding QGP, including the later stages of bottom-up thermalization, and the transverse expansion of the medium.

[1] Brewer, Yan, Yin, arxiv:1910.00021
[2] Brewer, Scheihing-Hitschfeld, Yin, arXiv:2203.02427
[3] Baier, Mueller, Schiff, Son, arXiv:hep-ph/0009237

Speaker: Rachel Steinhorst (Massachusetts Institute of Technology)

QM2023Steinhorst.pdf

16:30 Constraining the low x structure of nuclei with LHCb

The LHCb detector’s forward geometry provides unprecedented access to
the very low regions of Bjorken x inside the nucleon. With full particle ID and
a fast DAQ, LHCb is able to fully reconstruct plentiful charged particles and
neutral mesons, as well as relatively rare probes such as heavy quarks, providing
a unique set of constraints on nucleon structure functions. This contribution will
discuss recent LHCb measurements sensitive to the low-x structure of nucleons,
and discuss the impact of recent LHCb measurements that dramatically reduce
nPDF uncertainties.

Speaker: Thomas Boettcher (University of Cincinnati (US))

boettcher_QM2023.pdf

16:50 Using new methods for systematic study of nuclear structure in high-energy collisions to probe the effect of short-range correlations

There is increasing interest in using high-energy collisions to probe the structure of nuclei, in particular with the high-precision data made possible by collisions performed with pairs of isobaric species. A systematic study requires a variation of parameters representing nuclear properties such as radius, skin thickness, angular deformation, and short-range correlations, to determine the sensitivity of the various observables on each of these properties. In this work we propose a method for efficiently carrying out such study, based on the shifting of positions of nucleons in Monte-Carlo samples. We show that by using this method, statistical demands can be dramatically reduced --- potentially reducing the required number of simulated events by orders of magnitude --- paving the way for systematic study of nuclear structure in high-energy collisions.

As an application, we perform a systematic study of short-range nucleon-nucleon correlations and their effects on heavy-ion observables. Using our methods these effects, though small, can be precisely studied without the need for large numbers of simulations. In particular, we illustrate the limitations of a simple exclusion radius as a proxy for realistic nucleon-nucleon correlation functions.

Reference: arXiv:2302.14026

Speaker: Prof. Matthew William Luzum (University of São Paulo)

LuzumQuarkMatter_v1.pdf.

14:50 → 17:10 New Theory: (2)

Convener: Ulrich Heinz

14:50 A new approach to stochastic relativistic fluid dynamics from information flow

The study of thermal fluctuations in relativistic hydrodynamics is essential for understanding physics near the expected critical endpoint in the QCD phase diagram. Furthermore, the incorporation of stochastic fluctuations may be important for the modeling of hydrodynamics in small systems such as proton-proton and proton-nucleus collisions. We present a new general formalism for introducing thermal fluctuations in relativistic hydrodynamics which incorporates the recent developments on the causality and stability of relativistic hydrodynamic theories. Our approach is based on the recently introduced information current [1], which measures the net amount of information carried by perturbations around equilibrium in a relativistic many-body system. The resulting noise correlators are guaranteed to be observer-independent for thermodynamically stable models, which differs from previous approaches employed in the literature. We obtain a Martin-Siggia-Rose [2] action principle within our formalism and compare it to previous proposals for hydrodynamic effective actions. Finally, we present a few applications, which include the Israel-Stewart theory in a general hydrodynamic frame [3]. We find the adoption of a general hydrodynamic frame introduces new independent structures to the two-point function of the energy-momentum tensor which are not present in previous calculations done in the Landau or Eckart hydrodynamic frames.

[1] L. Gavassino, M. Antonelli, and B. Haskell, “Thermodynamic stability implies causality,” Physical Review Letters 128 (2022)

[2] P. C. Martin, E. D. Siggia, and H. A. Rose, “Statistical Dynamics of Classical Systems,” Phys. Rev. A 8, 423–437 (1973).

[3] Jorge Noronha, Michal Spali ́nski, and Enrico Speranza, “Transient relativistic fluid dynamics in a general hydrodynamic frame,” Physical Review Letters 128 (2022)

Speaker: Nicki Mullins

Mullins_QM2023_v3.pdf

15:10 Azimuthal anisotropies at high $p_T$ from transverse momentum dependent (TMD) parton distribution and fragmentation functions

Unpolarized protons can generate transversely polarized quarks or linearly polarized gluons through a distribution known as the Boer-Mulders' function. The fragmentation of similarly polarized partons to unpolarized hadrons is called the Collins' function. Both of these functions include correlations between the spin or polarization and the relative transverse momentum of the incoming parton or outgoing hadron, with respect to the parent particle.

We explore the effect of including these and other TMDs on the production of high-$p_T$ (unpolarized) hadron production from (unpolarized) proton-proton scattering. The resulting initial state anisotropies, coupled with similar final state effects, may account for the observed azimuthal anisotropy of the produced high transverse momentum hadrons, without modification to the angle integrated spectra ($R_{AA} \simeq 1$). This may be an explanation for the existence of a $v_2$ in high-$p_T$ hadron spectra in $p$-$A$ collisions without any observable nuclear modification of the spectra.

Speaker: Dr ismail soudi (Wayne State University)

Anisotropy_highpT_Ismail_Soudi.pdf

15:30 Transverse-momentum-dependent (TMD) factorization in reactions with nuclei: from Drell-Yan to hadron production

We study cold nuclear matter effects on Drell-Yan production at small and moderate $p_T$ in proton/pion-nucleus collisions using a new transverse-momentum dependent (TMD) factorization framework. Both collisional broadening and medium-induced radiative corrections in the initial state are considered in the soft-collinear effective theory with Glauber gluons (SCET$_{G}$) approach. We demonstrate that in-medium bremsstrahlung exhibits rapidity divergences as $x\rightarrow 1$ and collinear divergences at the endpoints $x=0,1$ of the emission spectra. We further show that the rapidity divergences lead to Balitsky-Fadin-Kuraev-Lipatov (BFKL) evolution of the collision kernel and can be resummed into the transverse momentum broadening of particle production. In turn, the endpoints divergences of in-medium radiation can be resummed through the collinear evolution of parton densities in nuclear matter. The TMD factorization framework is applied to understand the transverse-momentum spectra of Drell-Yan pair production in $pA$ and $\pi A$ collisions and provides calculations with improved accuracy for hadron production in cold QCD processes at RHIC and LHC.

Speaker: Dr Weiyao Ke (Los Alamos National Laboratory)

WeiyaoKe-QM23-09052023.pdf

15:50 Applicability of higher-order hydrodynamics in heavy-ion collisions

We study the boost-invariant non-conformal Boltzmann equation in the relaxation-time approximation using special moments of the distribution function and investigate how hydrodynamical behavior emerges as the plasma transits from the far-off-equilibrium free-streaming regime to the hydrodynamic regime. The infinite hierarchy of moments can be truncated by keeping only the three lowest moments that correspond to the three independent components of the energy-momentum tensor. By comparing the moment equations with the Israel-Stewart hydrodynamic equations, we demonstrate that the latter are able to capture the early-time, collisionless dynamics, albeit approximately, due to their relaxation-type structure [1]. We also derive second-order non-conformal hydrodynamics from the three-moment truncation and find that there are ambiguities in the definition of some second-order transport coefficients. In order to understand the nature of these ambiguities, we derive the full second-order non-conformal hydrodynamics by employing Chapman-Enskog expansion and also from a novel entropy approach and show that such ambiguities are inherent when defining some of the second-order transport coefficients [2]. We show that these ambiguities affect the ability of the Israel-Stewart hydrodynamics to reproduce the results of kinetic theory. The implications of these results in the context of heavy-ion collisions will be discussed.

[1] From moments of the distribution function to hydrodynamics: The nonconformal case, S. Jaiswal, J. P. Blaizot, R. S. Bhalerao, Z. Chen, A. Jaiswal and L. Yan, Phys. Rev. C 106, 044912 (2022)

[2] Shear-bulk coupling in second-order viscous hydrodynamics, S. Jaiswal, J. P. Blaizot (in preparation)

Speaker: Sunil Jaiswal (Tata Institute of Fundamental Research)

QM2023_SJaiswal.pdf

16:10 Sound of rigidly moving fluids: on linear waves in inhomogeneous equilibrium configurations (remote)

We propose a method to find local plane wave solutions to linearized equations of motion of relativistic hydrodynamics in inhomogeneous backgrounds, i.e., when fluid is rigidly moving with nonzero thermal vorticity in equilibrium. Our method is based on extending the conserved currents to the tangent bundle, using Wigner transforms. The Wigner-transformed conserved currents can then be Fourier transformed into the cotangent bundle to obtain the dispersion relations for space-time-dependent eigenfrequency. We show that the connection between the stability of hydrodynamics and the evolution of plane waves is not as straightforward as in the homogeneous case and is restricted to the equilibrium-preserving subspace of the cotangent bundle, which is determined by thermal vorticity. We apply this method to MIS theory and show that the interplay between the bulk viscous pressure and the shear stress tensor with acceleration and rotation leads to novel modes, as well as modifications of the already known ones.

Speaker: Masoud Shokri (Goethe University, ITP)

stability_talk.pdf

16:30 Mapping the critical equation of state by resummations

Determining the existence and the location of the QCD critical point remains a major goal in the heavy-ion collision experiments. A crucial theoretical input for achieving this goal is mapping the QCD equation of state in the presence of baryon chemical potential (mu) which at the moment is limited to small values of mu, away from the critical point. I present a new framework for reconstructing the equation of state from a truncated Taylor series expansion for small mu by using novel resummation techniques. I show how this resummation method can be used to (i) determine the location of the critical point and (ii) constrain the form of the critical contribution to the QCD equation of state which has a direct impact on the shape of the experimental signatures of the critical point.

Speaker: Prof. Gokce Basar (University of North Carolina, Chapel Hill)

lee-yang QM23.pdf

16:50 Far-from-equilibrium attractors for massive kinetic theory in the relaxation time approximation

We investigate whether early and late time attractors for non-conformal kinetic theories exist by computing the time-evolution of a large set of moments of the one-particle distribution function. For this purpose we make use of a previously obtained exact solution of the 0+1D boost-invariant massive Boltzmann equation in relaxation time approximation. We extend prior attractor studies of non-conformal systems by using a realistic mass- and temperature-dependent relaxation time and explicitly computing the effect of varying both the initial momentum-space anisotropy and initialization time on the time evolution of a large set of integral moments. Our findings are consistent with prior studies, which found that there is an attractor for the scaled longitudinal pressure, but not for the shear and bulk viscous corrections separately. We further present evidence that both late- and early-time attractors exist for all moments of the one-particle distribution function that contain greater than one power of the longitudinal momentum squared.

Speaker: Huda Alalawi

Huda_Alalawi_QM23.pdf

14:50 → 17:10 QCD at finite T and density: (1)

Convener: Berndt Mueller

14:50 High order fluctuations of conserved charges in the continuum limit

Sixth and higher order fluctuations of the baryon number are linked
to signals of criticality in heavy ion collisions. The grand canonical
result for these can be obtained from lattice simulations. The
extrapolation to the continuum limit is essential for phenomenologically
relevant results. In fact, higher order coefficients of the Taylor
expansion of the QCD free energy appear to be more sensitive to
discretization effects than lower orders. We meet the challenge in a
modest volume using the new 4HEX fermion action and calculate
the sixth order cumulants in a continuum extrapolation.

Speaker: Szabolcs Istvan Borsanyi

qm23_borsanyi.pdf

15:10 QCD based equation of state at finite density with a critical point from an alternative expansion scheme

Our study presents a family of Equations of State (EoS) that enable hydrodynamical simulations at unprecedentedly large baryon chemical potential ($\mu_B$) and finite temperature ($T$), thus helping to constrain the critical point's location by comparing it to experimental data from the Second Beam Energy Scan.
In Ref. [1], a family of equations of state was constructed by combining Taylor expansion QCD lattice results with 3D Ising model critical behavior. However, the applicability of this family was limited to the range of $ 0 \leq \mu_B \leq 450$ MeV. In recent work, [2,3], a resummation scheme was proposed that extrapolates lattice QCD results to the range of chemical potentials $\frac{\mu_B}{T} = 3.5 $.
In this work, we combine these approaches to obtain equations of state in the range $0 \leq \mu_B \leq 700$ MeV and 5 MeV $\leq T \leq 800$ MeV, which match lattice QCD results at low density and contain a 3D Ising model critical point. We impose stability and causality constraints and discuss the possible ranges of free parameter choices arising from the 3D Ising model to QCD mapping. We present thermodynamic observables, including baryon density, pressure, entropy, energy density, susceptibility, and speed of sound that cover a wide range in the QCD phase diagram.

[1] P. Parotto, M. Bluhm, D. Mroczek, M. Nahrgang, J. Noronha-Hostler,
K. Rajagopal, C. Ratti, T. Sch ̈afer, and M. Stephanov, “Qcd equation of
state matched to lattice data and exhibiting a critical point singularity,”
Physical Review C, vol. 101, no. 3, p. 034901, 2020. 1

[2] S. Bors ́anyi, J. N. Guenther, R. Kara, Z. Fodor, P. Parotto, A. P ́asztor,
C. Ratti, and K. Szab ́o, “Resummed lattice qcd equation of state at finite
baryon density: Strangeness neutrality and beyond,” Physical Review D,
vol. 105, no. 11, p. 114504, 2022. 1

[3] S. Bors ́anyi, Z. Fodor, J. Guenther, R. Kara, S. Katz, P. Parotto, A. P ́asztor,
C. Ratti, and K. Szab ́o, “Lattice qcd equation of state at finite chemical
potential from an alternative expansion scheme,” Physical review letters,
vol. 126, no. 23, p. 232001, 2021. 1
2

Speaker: Micheal Kahangirwe

Micheal_Kahangirwe.pdf

15:30 Bayesian Inference of QGP Properties and 3D Dynamics in Heavy-Ion Collisions in the RHIC Beam Energy Scan Program

This talk will present the Bayesian inference approach for quantitatively characterizing the 3D dynamics of heavy-ion collisions and the Quark-Gluon Plasma (QGP) properties in the RHIC Beam Energy Scan (BES) program. To model the dynamics of the collisions from 7.7 to 200 GeV, we employ a (3+1)D dynamical initialization model coupled with the relativistic viscous hydrodynamics + hadronic cascade hybrid framework [1]. To account for shear and bulk viscous effects at RHIC BES energies, we derive the out-of-equilibrium corrections to particle distributions with multiple conserved charge currents using Grad's moment and Chapman-Enskog methods. A fast model emulator is then trained in a 22-dimensional parameter space to accurately predict identified particle yields, average transverse momenta, and charged hadron anisotropic flow coefficients. By carrying out a joint Bayesian analysis of the RHIC BES phase I measurements for Au+Au collisions at 7.7, 19.6, and 200 GeV, we set robust constraints on initial-state baryon stopping and the $\mu_B$ and $T$ dependence of the QGP shear and bulk viscosity. Our results show that the Bayesian inference approach with our full (3+1)D hybrid framework effectively extracts the QGP properties and the 3D dynamics of the collision events from the RHIC BES measurements and provides quantitative insights into the QCD matter in a baryon-rich environment.

[1] C. Shen and B. Schenke, "Longitudinal dynamics and particle production in relativistic nuclear collisions," Phys. Rev. C105, no.6, 064905 (2022)

Speaker: Chun Shen (Wayne State University)

BESBayesian_Shen.pdf

15:50 Particle production in Au+Au collisions at Beam Energy Scan II energies 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 the QCD matter, the Relativistic Heavy Ion Collider (RHIC) started the first phase of the Beam Energy Scan (BES-I) program in 2010, delivering Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7 to 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. Au+Au collisions at $\sqrt{s_{\text{NN}}}$= $7.7-54.4$ $\text{GeV}$ were collected during $2017-2021$, covering a large area of the QCD phase diagram in temperature and baryon chemical potential by varying the collision energy, centrality, and rapidity. In particular, the installed Event Plane Detector (EPD) enables the measurement of charged particle production at far-backward pseudorapidity.

In this talk, we present pseudorapidity distributions of charged particles in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7 to 27 GeV with the EPD ($2.15 < |\eta| < 5.09$). We will also present the transverse momentum spectra of identified hadrons ($\pi^{\pm}$, $K^{\pm}$, $p$ and $\bar{p}$) in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7 to 54.4 GeV within mid-rapidity ($|y| < 1$). The mid-rapidity yields of identified hadrons show the expected signatures of large baryon stopping at lower energies and the dominance of pair production at higher energies. The centrality dependence of integrated yields (dN/dy and dN/d$\eta$), average transverse momenta ($\langle p_{T} \rangle$), particle ratios, chemical and kinetic freeze-out parameters will also be presented. These results will be compared to published results at other collision energies and the new insights to the QCD phase diagram will be discussed.

Speaker: Matthew Harasty (University of California, Davis)

Harasty_Matthew_QM23_v5.pdf

16:10 Equation of state of a hot-and-dense quark gluon plasma: lattice simulations at real $\mu_B$ vs. extrapolations

The equation of state of the quark gluon plasma is a key ingredient of heavy ion phenomenology. In addition to the traditional Taylor method, several novel approximation schemes have been proposed with the aim of calculating it at finite baryon density. In order to gain a pragmatic understanding of the limits of these schemes, we compare them to direct results at $\mu >0$, using reweighting techniques free from an overlap problem. We use 2-stout improved staggered fermions with 8 time-slices and cover the entire RHIC BES range in the baryochemical potential, up to $\mu_B/T=3$.

Speaker: Dr Chik Him Wong

presentation.pdf

16:30 QCD equation of state with improved precision from lattice simulations

The equation of state of Quantum Chromodynamics has been in recent
years the focus of intense effort from first principle methods,
mostly lattice simulations, with particular interest to the finite
baryon density regime. Because of the sign problem, various
extrapolation methods have been used to reconstruct bulk properties
of the theory up to as far as $\mu_B/T \simeq 3.5$. However, said
efforts rely on the equation of state at vanishing baryon density
as an integration constant, which up to $\mu_B/T \simeq 2 - 2.5$
proves to be the dominant source of uncertainty at the level of
precision currently available. In this work we present the update of
our equation of state at zero net baryon density from 2014, performing
a continuum limit from lattices with $N_\tau=8,10,12,16$. We show
how the improved precision is translated in a lower uncertainty on
the extrapolated equation of state at finite chemical potential.

Speaker: Paolo Parotto

Parotto_QM23.pdf

16:50 Heavy quark diffusion from 2+1 flavor lattice QCD

Heavy quarks are produced in the early stages of the ultra-relativistic heavy-ion collisions and probe the produced hot medium created in these collisions through its entire evolution. The kinetic thermalization of heavy quarks can be characterized by the heavy quark diffusion coefficient. In this talk we report the first determination of the heavy diffusion coefficient in 2+1 flavor lattice QCD in temperature range 195 <T< 352 MeV using the heavy quark effective theory approach combined with novel gradient flow technique. We found that our full QCD determinations are significantly smaller than the quenched lattice QCD determinations and recent phenomenological estimates, implying a very fast kinetic thermalization the heavy quarks. Within this approach we also estimate the first mass suppressed correction to the diffusion coefficient for the first time in 2+1 flavor QCD for the above temperature range.

Speaker: Hai-Tao Shu

qm23.pdf

14:50 → 17:10 Small Systems: (1)

Convener: William Zajc (Columbia University)

14:50 Small-system properties as measured with jets and high-$p_\mathrm{T}$ azimuthal anisotropy by the CMS experiment

High-energy jets are produced by the fragmentation of partons (quarks and gluons) that underwent hard scattering in the early stages of a collision. For quite a number of years, jets have been successfully used to probe the properties of the special form of matter, the quark gluon plasma (QGP), formed in high-energy heavy ion collisions. One of the most recognized signatures of the QGP, the jet quenching phenomenon, has been evidenced by a wide range of LHC measurements from lead-lead collisions. More recently, experimental results through multiparticle correlation techniques provided some evidence of possible QGP formation in the smaller colliding systems, such as high-multiplicity proton-proton and proton-lead collisions, but confirmation of the jet quenching expected for QGP remains elusive for such collisions. In this talk, systematic measurements of jet properties are presented for proton-lead collisions data collected by the CMS experiment to search for hot medium production or effects of cold nuclear matter in small systems. Using the subevent cumulant method, multiparticle correlations are also measured for particles with high transverse momentum.

Speaker: Dener De Souza Lemos (University of Illinois at Chicago (US))

QM23_jetsmall_DSLemos-finalv2.pdf

15:10 Pinning down the origin of collectivity in small systems with ALICE (remote)

While the formation of the quark--gluon plasma (QGP) in heavy-ion collisions has been confirmed by characteristic patterns of flow measurements, it remains unclear what is the smallest possible collision system that can generate a similar medium exhibiting partonic collectivity. In this talk, we will present the new preliminary results of anisotropic flow in pp, p--Pb, and Pb--Pb collisions that, for the first time, encompass all the data collected by ALICE. The highlights include the flow of charged and identified particles ($\pi^{\pm}$, K$^{\pm}$, p ($\overline{\rm {p}}$), K$^0_S$, $\Lambda$ ($\overline \Lambda$), $\varphi$), correlations and fluctuations of flow vectors and correlations between the mean transverse momentum and flow coefficients, $\rho(v_n^2,[p_\mathrm{T}])$. Multiparticle cumulants with the subevent method, ultra-long-range azimuthal correlations with the template fit method, and a novel jet veto approach have been implemented to effectively suppress short-range non-flow contamination. We compare our results to state-of-the-art theoretical models, which will allow us to study contributions from initial momentum anisotropies to final anisotropic flow, and to understand how anisotropic flow in small collision systems developed from the initial geometry through the dynamic evolution including the understanding of the role of mass and constituent-quark numbers.

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

slides_QM_v6.pdf

15:30 Recent results from 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, intermediate to previous fixed-target experiments and the top
RHIC energy for AA collisions, and allow systems of different size to be stud-
ied. Here we present new results on open charm, J/ψ, and ψ(2S) production
from pNe and PbNe fixed-target collisions at LHCb. Comparisons with various
theoretical models of particle production and transport through the nucleus will
be discussed

Speaker: Kara Mattioli (Centre National de la Recherche Scientifique (FR))

Recent results from LHCb Fixed Target QM 2023.pdf

15:50 Measuring jet quenching with a Bayesian Inference analysis of hadron and jet data by JETSCAPE

The JETSCAPE Collaboration reports new studies of jet transport in the QGP using Bayesian Inference, incorporating both hadron and jet inclusive yield suppression data, and jet substructure data. This analysis extends the previously published JETSCAPE Bayesian determination of $\hat{q}$, which was based solely on inclusive hadron suppression data.

JETSCAPE is a modular framework for multi-stage modeling of in-medium jet evolution and medium response, with rigorous data-model comparison using a Bayesian formalism. The theoretical model in the current study utilizes virtuality-dependent in-medium partonic energy loss coupled to a detailed dynamical model of QGP evolution.

The $\hat{q}$ analysis presented in this talk includes, for the first time, all reported hadron and jet inclusive yield suppression measurements at RHIC and the LHC. The uncertainty covariance of the data is estimated, where not reported. We explore the tension in this determination of $\hat{q}$ between the hadron and the various jet measurements, and between different kinematic regions. In addition we examine the additional information that jet substructure observables provide beyond that contained in inclusive jet and hadron suppression observables. These studies provide new insight into the mechanisms of jet interactions in matter, and point to next steps in the field for comprehensive understanding of jet quenching as a probe of the QGP.

Speaker: Raymond Ehlers (University of California Berkeley (US))

2023-09-05.rehlers.jetscape_bayesian_hard_sector.v4.pdf

16:10 Correlation between $\Upsilon$(nS) meson and underlying event in $pp$ collision

We will present the final measurement studying the relationship between the production of hard and soft particles through the correlation of Upsilon meson states (including $\Upsilon$(1S), $\Upsilon$(2S), and $\Upsilon$(3S)) with the inclusive-charged particle yields. The analysis is performed using the full-luminosity ATLAS Run-2 13 TeV $pp$ collision data. A description of the technical challenges and solutions associated with a heavy-ion style analysis in high-pileup $pp$ data will be shown. Per-event charged particle multiplicity is found to be smaller in association with excited $\Upsilon$ states compared to that with a ground state at low $\Upsilon$ transverse momentum. The physics implications will be discussed.

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

ATLAS_upsilon_qm_flat.pdf

16:30 Flowing to the future: Simulating the tiniest fluids in 3+1 dimensions

Employing a dynamical initial state model coupled to (3+1)D viscous relativistic hydrodynamics, we explore the rapidity dependence of anisotropic flow in the Relativistic Heavy-Ion Collider (RHIC) small system scan at 200 GeV center of mass energy. We demonstrate that approximately 50% of the pT-differential triangular flow difference between the measurements by the STAR and PHENIX Collaborations can be explained by the use of reference flow vectors from different rapidity regions. This emphasizes the importance of longitudinal flow decorrelation for anisotropic flow measurements in asymmetric nuclear collisions, and the need for (3+1)D simulations. We further present results for the beam energy scan of d+Au collisions and compare to PHENIX data. The same framework is used to describe p+Pb collisions and photo-nuclear events in ultra-peripheral Pb+Pb collisions at the Large Hadron Collider (LHC). We compare to experimental data on momentum anisotropies from the ATLAS Collaboration and find good agreement with the measured elliptic flow. Again, the importance of longitudinal flow decorrelations is highlighted, as they dominate the elliptic flow hierarchy between p+Pb and γ+Pb collisions. Our results imply that QCD fluids can be created at the future Electron Ion Collider, where they could be studied in great detail.

References:

3D structure of anisotropic flow in small collision systems at energies available at the BNL Relativistic Heavy Ion Collider
Wenbin Zhao, Sangwook Ryu, Chun Shen, Björn Schenke
e-Print: 2211.16376 [nucl-th] DOI: 10.1103/PhysRevC.107.014904
Published in: Phys.Rev.C 107 (2023) 1, 014904

Collectivity in Ultraperipheral Pb+Pb Collisions at the Large Hadron Collider
Wenbin Zhao, Chun Shen, Björn Schenke
e-Print: 2203.06094 [nucl-th] DOI: 10.1103/PhysRevLett.129.252302
Published in: Phys.Rev.Lett. 129 (2022) 25, 252302

Speaker: Bjoern Schenke (Brookhaven National Lab)

QM_Schenke.pdf

16:50 Measurements of azimuthal anisotropies in $^{16}$O+$^{16}$O and $\gamma$+Au collisions from STAR

Collectivity in small systems is a crucial area of study in high-energy nuclear physics, as it provides valuable insights into initial conditions and pre-equilibrium stages in heavy-ion collisions. The small system collision scan at RHIC, including both symmetric and asymmetric small systems (O+O $>$ $^{3}$He$+$Au $>$ $d$$+$Au $>$ $p$$+$Au $>$ $\gamma+$Au), provides a better understanding of how collectivity emerges and evolves with system size.

We analyze a large sample of minimum bias and central triggered $^{16}$O+$^{16}$O collisions at $\sqrt{s_{NN}}$ = 200 GeV and inclusive $\gamma$+Au processes (center-of-mass energy around 40 GeV) by triggering ultra-peripheral events in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV. Using two- and four-particle correlation methods, we present the first measurements of azimuthal anisotropies, $v_2$ and $v_3$, in $^{16}$O+$^{16}$O and $\gamma$+Au collisions as a function of $p_{\mathrm{T}}$ and multiplicity. We compare our measurements with STAR measurements of $v_n$ in $p/d/^3$He+Au collisions and hydrodynamic model calculations.

New $v_{n}$ measurements in $^{16}$O+$^{16}$O collisions provide insight into the impact of system symmetry on initial condition and pre-equilibrium dynamics, compared to the previously studied asymmetric systems $p/d/^3$He+Au. We also investigate the ratio $v_2\{4\}/v_2\{2\}$ and correlations between $v_n$ and mean $p_{\mathrm{T}}$ as a function of multiplicity, which are sensitive to initial momentum anisotropy, subnucleon fluctuations, and clustering in the $^{16}$O nucleus. In addition, $v_{n}$ measurements in $\gamma$+Au processes play an important role in understanding the origin of collectivity and lay the foundation for searching for many-body systems exhibiting collective behavior in photon-induced processes at the EIC.

Speaker: Shengli Huang

OO-ShengliHuang-QM2023-17.pdf

17:10 → 17:30 Wine & Cheese for the poster session

17:30 → 19:40 Poster Session

17:30 $\mathrm{K^{0}_S}$ and $\Lambda$ ($\bar{\Lambda}$) two-particle femtoscopic correlations in PbPb collisions with the CMS experiment

Two-particle correlations are presented for $\mathrm{K^{0}_S}$, $\Lambda$, and $\bar{\Lambda}$ strange hadrons as a function of relative momentum in lead-lead (PbPb) collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV with data samples collected by the CMS experiment. These correlations are sensitive to quantum statistics and to final-state interactions between particles. The $\Lambda\Lambda$ femtoscopic correlation is measured for the first time in PbPb collisions. It is seen that the shape of the correlation distributions varies largely for different particle pair species, revealing the effect of the strong final-state interaction in each case. The source size extracted from the $\mathrm{K^{0}_S}\mathrm{K^{0}_S}$ correlations is found to decrease from 4 to 1 fm in going from central to peripheral collisions. Strong interaction scattering parameters (i.e. scattering length and effective range) are determined from the $\Lambda\mathrm{K^{0}_S}$ and $\Lambda\Lambda$ (including their charge conjugates) correlations using the Lednicky--Lyuboshitz model and are compared to theoretical and other experimental results.

Speaker: Michael Murray (The University of Kansas (US))

17:30 $\Omega_{\rm c}^{0}$ production in pp collisions at $\sqrt s$ = 13 TeV with ALICE

Recent measurements of the production of charm hadrons at midrapidity in pp collisions at $\sqrt s$ = 5.02 and 13 TeV showed that the baryon-to-meson yield ratios are significantly larger than those measured in $\rm e^{+}e^{-}$ collisions for different charm-baryon species. These observations suggest that the charm fragmentation fractions are not universal and that the baryon-to-meson ratios depend on the collision systems.

In this poster, the new measurement of the inclusive $p_{\rm T}$-differential cross section of the charm-strange baryon $\Omega_{\rm c}^{0}$ multiplied by the branching ratio of the $\Omega_{\rm c}^{0} \rightarrow \rm \Omega^{-}\pi^{+}$ decay channel in pp collisions at $\sqrt s$ = 13 TeV will be reported, and compared with theoretical calculations.

However, the lack of absolute measurements of the $\Omega_{\rm c}^{0}$ branching ratios makes it difficult to draw conclusions about the effective $\Omega_{\rm c}^{0}$ enhancement. To address this, a new analysis of the $\Omega_{\rm c}^{0}$ reconstructed from the $\rm e^{+}\Omega^{-}\nu_{e}$ decay channel is being performed, and its status and developments will be also discussed.

Speaker: Tiantian Cheng (CCNU - Central China Normal University(CN), GSI - Helmholtzzentrum fur Schwerionenforschung GmbH(DE))

QM2023_TiantianCheng_Final_HF117.pdf

17:30 $K^{+}K^{+}$ correlation functions in Au+Au collisions at 3.0 - 3.9 GeV

Two-particle correlations are used to extract the space-time and dynamical information of the particle-emitting source created in heavy-ion collisions. The source radii extracted from these correlations characterize the system at the kinetic freeze-out, i.e., the last stage of particle interactions. Kaons can provide a more direct view of the particle-emitting source than pions as they have smaller hadronic cross section and less contribution from long lifetime resonances.

In this poster, the measurements of $K^{+}K^{+}$ correlation functions in Au+Au collisions at $\sqrt{s_{NN}}$ = 3.0, 3.2, 3.5, and 3.9 GeV recorded by the STAR experiment will be presented. One-dimensional source size $(R_{inv})$ and correlation strength parameter ($\lambda$) of the system are extracted from the correlation functions using the Bowler-Sinyukov formula. The comparison of the measured radii with the predictions from UrQMD+CRAB will be discussed.

Speaker: Bijun Fan (Central China Normal University)

QM2023_poster_BijunFan_v4.pdf

17:30 $K_{1}/K^{*}$ enhancement as a signature of chiral symmetry restoration in heavy ion collisions

Based on the fact that the mass difference between the chiral partners is an order parameter of chiral phase transition and that the chiral order parameter reduces substantially at the chemical freeze-out point in ultra-relativistic heavy ion collisions, we argue that the production ratio of K1 over K∗ in such collisions should be substantially larger than that predicted in the statistical hadronization model. We further show that while the enhancement effect might be contaminated by the relatively larger decrease of K1 meson than K∗ meson during the hadronic phase, the signal will be visible through a systematic study on centrality as the kinetic freeze-out temperature is higher and the hadronic life time shorter in peripheral collisions than in central collisions.

Speaker: Haesom Sung

2023QM_Haesom Sung3.pdf

17:30 3D structure of jet-induced Mach cone in an expanding QGP

Jet-induced medium response is in the form of Mach-cone-like excitation. Diffusion wake accompanying this Mach-cone provides a unique probe of the properties of quark-gluon plasma in high-energy heavy-ion collisions. It can be characterized by a depletion of soft hadrons in the opposite direction of the propagating jet. We explore the 3D structure of the diffusion wake induced by $\gamma$-triggered jets in Pb+Pb collisions at the LHC energy within the coupled linear Boltzmann transport and hydro model. We identify a valley structure caused by the diffusion wake on top of a ridge from the initial multiple parton interaction (MPI) in jet-hadron correlation as a function of rapidity and azimuthal angle. This leads to a double-peak structure in the rapidity distribution of soft hadrons in the opposite direction of the jets as an unambiguous signal of the diffusion wake. Using a two-Gaussian fit, we extract the diffusion wake and MPI contributions to the double peak. The diffusion wake valley is found to increase with the azimuthal angle away from the jet. It is also found to deepen with the jet energy loss as characterized by the $\gamma$-jet asymmetry. Its sensitivity to medium properties such as the shear viscosity and equation of state is also studied.

Speaker: Zhong Yang (CCNU)

17:30 A Longitudinally Segmented Hadronic Calorimeter for the Forward Region of the Future ePIC Detector at the Electron-Ion-Collider

The Electron-Ion Collider (EIC) at Brookhaven National Laboratory will be an experimental facility to explore gluons in nucleons and nuclei, shedding light on their structure and the interactions within. The ePIC detector will be the first experiment at the EIC dedicated to detailed studies of nuclear structure in electron-proton and electron-ion collisions.

The ambitious physics program of the EIC requires a high performance hadronic calorimetry system in the hadron-going “forward” region. Accurate jet measurements are crucial to reconstruct the full 3D nucleon tomography and to study the gluon saturation region. The main goal of the Longitudinally segmented Forward HCal (lf-HCal) is measuring the energies of jets and distinguishing between overlapping jet depositions to high accuracy in the jet energy range up to 120 GeV.

lf-HCal is designed as a plastic scintillator-steel sandwich calorimeter. The plastic scintillator is transversely segmented into $5\times5$,cm${}^2$ tiles. Each tile is directly coupled to a silicon photomultiplier. The electrical signals of all photomultipliers are routed out of the lf-HCal to be digitized by external readout electronics.

This poster will present the current status as well as ongoing and future R&D of the lf-HCal for the ePIC experiment.

Speaker: Iris Ponce (Yale University)

QM2023_lfHCAL_Poster_Ponce_final.pdf

17:30 A modular perspective to the jet quenching from a small to large radius in very high transverse momentum jets

In this contribution, we extend the scope of the JETSCAPE framework to cover the jet radius ($R$) dependence of the jet nuclear modification factor, ${R_{AA}}$, for broader area jet cones, going all the way up to $R$ = 1.0. The primary focus of this work has been the in-depth analysis of the high-${p_{T}}$ inclusive jets and the quenching effects observed in the quark-gluon plasma formed in the Pb-Pb collisions at ${\sqrt{\rm s_{NN}}}$= 5.02 TeV for the most-central (0-10%) collisions. The nuclear modification factor is calculated for inclusive jets to compare with the experimental data from the ATLAS and CMS detectors in the jet transverse momentum (${p_{T}}$) ranging from 100 GeV up to 1 TeV. The results predicted by the JETSCAPE are consistent in the high ${p_{T}}$ range as well as for extreme jet cone sizes within 10-20\%. We also calculate the double ratio (${R^{\mathrm{R}}_{\mathrm{AA}}/R^{\mathrm{R=small}}_{\mathrm{AA}}}$) as a function of jet radius and jet-${p_{T}}$, where the observations are well described by the JETSCAPE framework which is based on the hydrodynamic multi-stage evolution of the parton shower. The calculations are then performed for low-virtuality-based evolution models like the MARTINI and the AdS/CFT, followed by a rigorous comparison between the former model's predictions and the CMS experiment's measurements.

Speaker: Prabhakar Palni (IIT Mandi)

17:30 A New Horizon - Dielectron measurements with ALICE 3

Electromagnetic radiation is emitted throughout the whole evolution of high-energy heavy-ion collisions. Due to their penetrating nature, real and virtual photons reach the detector unimpeded. Their measurement makes it possible to shed light on the different stages of the extreme states of matter created in such collisions.

In this poster, we will discuss dielectron measurements that will only be possible with a new generation's experiment at the LHC and the features of the ALICE 3 detector that will enable them. In particular, the rejection of dielectrons from correlated semi-leptonic decays of heavy-flavour hadrons will be evaluated. We will present the expected performance of differential measurements of the thermal emission of dielectrons and the derived early-time temperature of the medium. The unique possibility to probe the pre-hydrodynamic phase of the medium with $\rm e^{+}e^{-}$ pairs will be discussed. In addition, the capability for detailed studies of chiral symmetry restoration mechanisms with a precise measurement of the rho spectral function will be addressed.

Speaker: Horst Sebastian Scheid (Goethe University Frankfurt (DE))

QM_scheid_final.pdf

17:30 A unified picture for dilute-dense dynamics in nuclear medium

We elucidate the relationship between Color Glass Condensate (CGC) and Higher-twist (HT) formalisms at the level of physical observables by studying the direct photon production in proton-nucleus collisions. The CGC effective theory and the HT factorization theorem are two established formalisms that describe multiple scatterings of quarks and gluons in nuclear media within Quantum Chromodynamics (QCD). These formalisms have distinct domains of validity in kinematic regions. Going beyond the shock wave approximation and considering the Landau-Pomeranchuk-Migdal effect, which arises from the interference of initial- and final-state scatterings, we show for the first time that CGC and HT formalisms can be unified to describe the same physics in the transition region where they overlap. This unified picture provides a framework for understanding the QCD dynamics in the transition from dilute to dense nuclear matter, paving the way for mapping out the QCD evolution phase diagram of nuclear medium from dilute to dense region. This study highlights the importance of sub-eikonal phases in accurately describing multiple scatterings in nuclear media and sheds new light on the interplay between HT and CGC formalisms.

Speaker: Yu Fu (Duke university)

QM2023_YuFu.pdf

17:30 Adiabatic hydrodynamization in the bottom-up thermalization scenario

We demonstrate that the early stages of the bottom-up thermalization scenario [1] are well described by the adiabatic hydrodynamization framework, thus providing novel analytic results on the thermalization process of QCD in a heavy ion collision. These results provide an intuitive explanation of why a gas of quarks and gluons can relax so quickly towards equilibrium, and provide a starting point for a systematic exploration of pre-hydrodynamic attractors in QCD. All of the qualitative features exhibited in QCD effective kinetic theory (EKT) simulations at weak coupling [2] are captured by the emergence of an effective low-energy instantaneous ground state for the 1-particle gluon distribution function, which defines the early-time kinetic theory attractor. This ground state may be pulled back to arbitrarily early times, where it represents a free-streaming solution, and at later times it integrally describes the BMSS fixed point, including the recently observed deviations from the original predictions for the scaling exponents [2].

To find this instantaneous ground state it is necessary to elucidate the deep connections between scaling and adiabaticity in expanding gluon plasmas [3]. We first solve the Boltzmann equation for gluons in the small-angle scattering approximation numerically and find that it features time-dependent scaling, reproducing the QCD EKT scaling of hard gluons [2]. By studying this equation analytically, we find that an appropriate momentum rescaling allows the scaling distribution to be identified as the instantaneous ground state of the operator describing the evolution of the distribution function, and the approach to the scaling function is described by the decay of the excited states. That is to say, the system evolves adiabatically, and the instantaneous ground state describes the early-time kinetic theory attractor. We obtain this ground state analytically. Corrections to the BMSS fixed point exponents agree quantitatively with those found previously in QCD EKT.

---

[1] Baier, Mueller, Schiff, Son, arXiv:hep-ph/0009237
[2] Mazeliauskas, Berges, arXiv:1810.10554
[3] Brewer, Scheihing-Hitschfeld, Yin, arXiv:2203.02427

Speaker: Bruno Sebastian Scheihing Hitschfeld (Massachusetts Institute of Technology)

QM2023_poster.pdf

17:30 Advanced coalescence model based on the Wigner function formalism

The production of deuterons in pp collisions at $\sqrt{s}=$ 13 TeV is simulated on an event-by-event basis using a coalescence afterburner based on a state-of-the-art Wigner-function formalism, and EPOS 3 and PYTHIA 8.3 as event generators. The space-momentum correlations of the nucleon pairs provided by the event generators are preserved, while the nucleon-emitting source is modelled such to reproduce the $m_{\rm T}$-dependence of the source size measured by ALICE. For the first time, the results of this model show that using a realistic wavefunction for deuterons, namely Argonne $v_{18}$, it is possible to reproduce the measured deuteron spectra with no free parameters.

Speaker: Chiara Pinto (Technische Universitaet Muenchen (DE))

QM Poster-5.pdf

17:30 ALICE as an (anti)hypernuclei factory

Hypernuclei are bound states of nucleons and hyperons. The study of their properties, such as their lifetimes and binding energies, provide information on the hadronic interaction between hyperons and nucleons which are complementary to those obtained from correlation measurements. Precise modeling of this interaction is a fundamental input for the calculation of the equation of state of high-density nuclear matter inside neutron stars. Moreover, measurements of their production rate in different collision systems are important to constrain (hyper)nuclei production models, such as the statistical hadronization model and baryon coalescence.

In this presentation, the first-ever observations of the (anti)hyperhydrogen-4 and (anti)hyperhelium-4 in Pb--Pb collisions at 5.02 TeV will be presented. These measurements pave the way for detailed investigations of the large charge symmetry breaking implied by the Λ binding energy difference in these hypernuclei. Moreover, differential measurements of their productions yields will contribute to a better understanding of their production models. Recent results on the hypertriton production, high-precision measurements of its lifetime and binding energy in Pb--Pb collisions will also be shown and discussed in the context of the state-of-the-art theoretical models.

Speaker: Janik Ditzel (Goethe University Frankfurt (DE))

Poster_QM2023_JD.pdf

17:30 Alignment from spin-1 hydrodynamics

The spin alignment of vector mesons emitted in heavy-ion collisions has recently been measured by the ALICE and STAR collaborations over a wide range of energies [1, 2]. The alignment is part of the so-called tensor polarization, which is a property that is exclusive to particles of spin 1 and higher. Even though there have been substantial theoretical efforts, a definite explanation for the tensions between theory and experiments does not yet exist.

In this work [3], we derive an expression for the tensor polarization of a system of massive spin-1 particles in a hydrodynamic framework. Starting from quantum kinetic theory based on the Wigner-function formalism, we employ a modified method of moments which also takes into account all spin degrees of freedom. We find that the tensor polarization is independent of the nonlocal part of the collision term and sourced by the usual dissipative quantities of the fluid, i.e., the bulk-viscous pressure, the particle-diffusion current, and the shear-stress tensor. As an example, we compute the relevant transport coefficient in the case of an uncharged fluid, where, neglecting bulk effects, the tensor polarization is determined solely by the shear-stress tensor. In order to quantify this polarization effect, we provide a formula which can be used for numerical calculations of vector-meson spin alignment in relativistic heavy-ion collisions.

[1] S. Acharya et al. (ALICE), Phys. Rev. Lett. 125, 012301 (2020), 1910.14408.
[2] M. Abdallah et al. (STAR), Nature 614, 7947 (2023), 2204.02302.
[3] D. Wagner, N. Weickgenannt, E. Speranza, Phys. Rev. Res. 5, 013187 (2023), 2207.01111.

Speaker: David Wagner (Goethe University Frankfurt)

QM_poster_David_Wagner_050923.pdf

17:30 Alignment of the sPHENIX Tracking Detectors

The tracking system of the sPHENIX detector at RHIC consists of three layers of MAPS based silicon pixel detectors for precise vertex determination, two layers of silicon strip detectors for pattern recognition and beam crossing determination, a TPC for precise momentum measurement, and a partial coverage micromegas detector to assist with calibration of space charge distortions in the TPC. The physics program of sPHENIX imposes stringent requirements on the precision of both the displaced vertex measurement and the momentum resolution. Meeting those requirements demands precise alignment of the four tracking subsystems. This poster describes the alignment process for the sPHENIX tracking system. The sPHENIX detector is taking data for the first time during the 2023 RHIC run, and the status of the alignment at the time of the conference will be presented.

Speaker: Reese Boucher

Boucher-poster-qm23-sphenix.pdf

17:30 An Augmented QCD Phase Portrait: Mapping Quark-Hadron Deconfinement for Hot, Dense, Rotating Matter under Magnetic Field

The quark-hadron transition that happens in ultra-relativistic heavy-ion collisions is expected to be influenced by the effects of rotation and magnetic field, both present due to the geometry of a generic non-head-on impact. We augment the conventional $ T$--$\mu_B$ planar phase diagram for QCD matter by extending it to a multi-dimensional domain spanned by temperature $T$, baryon chemical potential $\mu_B$, external magnetic field $B$ and angular velocity $\omega$. Using two independent approaches, one from a rapid rise in entropy density and another dealing with a dip in the speed of sound, we identify deconfinement in the framework of a modified statistical hadronization model. We find that the deconfinement temperature $T_C(\mu_B,\omega,eB)$ decreases nearly monotonically with increasing $ \mu_B, \omega $ and $ eB $ with the most prominent drop (by nearly $40$ to $50$ MeV) in $T_C$ occurring when all the three quasi-control (collision energy and impact parameter dependent) parameters are simultaneously tuned to finite values that are typically achievable in present and upcoming heavy-ion colliders.

Speaker: Gaurav Mukherjee (Bhabha Atomic Research Centre, Homi Bhabha National Institute)

Poster_QM23_aug_QCD_finale.pdf

Poster_QM23_aug_QCD.pdf

17:30 An efficient numerical solver for relativistic hydrodynamics with an implicit Runge-Kutta method

We develop an implicit numerical method for solving relativistic hydrodynamics that can be more efficient than conventional explicit methods. While implicit Runge-Kutta methods have nice properties such as their stability, they are not used usually since they are generally considered to be computationally expensive. In the present study, we solve this problem by introducing a fixed-point solver for the implicit Runge-Kutta methods with several optimizations. The Kurganov-Tadmor scheme is employed for the space discretization. The accuracy and computational cost of our new method are compared with those of explicit ones with the same space scheme in the case of ideal hydrodynamics for the initial conditions of the Riemann problem and the Gubser flow, as well as the event-by-event initial conditions for heavy-ion collisions generated by TRENTo. We demonstrate that the solver converges with only one iteration in most cases, and as a result, contrary to the general expectation, the implicit method requires smaller computational cost than the explicit one at the same accuracy in these cases.

Speaker: Masakiyo Kitazawa

230905QM_hydro.pdf

17:30 An innovative approach to control volume fluctuations for studies of critical phenomena in nuclear collisions

We present an innovative procedure to account for unavoidable contributions from volume (or system size) fluctuations to experimentally measured cumulants of particle multiplicity distributions produced in relativistic nuclear collisions. For the first time we extract participant fluctuations directly from the data used for the fluctuation analysis, i.e., without involving model calculations [1]. To achieve this we exploit a dedicated event-mixing algorithm. Participant fluctuations are extracted by constructing cumulants of multiplicity distributions for different particle species and covariances between all possible pairs of particles. A detailed procedure for evaluating the precision of the method for different experiments, such as STAR at RHIC/BNL and HADES GSI/SIS18 will be discussed. The proposed method is essential for analyzing fluctuation signals at low collision energy, but can be applied at LHC energy as well.

[1] A. Rustamov, R. Holzmann, J. Stroth Nucl.Phys. A 1034 (2023) 122641

Speaker: Anar Rustamov (GSI Helmholtzzentrum für Schwerionenforschung GmbH)

QM23_AR_RH_JS_White.pdf

17:30 Analysis of the critical fluctuations in the light-nuclei production

We investigate the critical fluctuations in light-nuclei production in heavy-ion collisions based on the coalescence model, where we introduce corrections to the distribution function from critical correlators from the Ising model.

The measurement of the yield ratio of light nuclei, $N_tN_p/N^2_d$ (with $N_t$, $N_p$, and $N_d$ being triton, proton, and deuteron numbers, respectively), in STAR collaboration [1], has shown a non-monotonic behavior as a function of collision energy in a heavy-ion collision. Based on the analyses with idealized setups, it was also suggested that the yield ratio is one of the observables for a possible signal of the QCD critical point [2]. However, it is non-trivial how the yield ratio is affected by the other contributions in realistic setups of heavy-ion collisions. In our previous study, we expanded the distribution function of nucleons in terms of phase-space cumulants [3] and found that the effect of cumulants cancels in the yield ratio up to the second order, which also includes the effect of radial expansions.

In the first part of this talk, we further investigate the effect of non-trivial phase-space distributions [3] by example distributions including the Woods-Saxon distribution, two Gaussian forms, and the blast-wave-type anisotropic flows. We find that the spatial structure decreases the ratio while the momentum anisotropy increases it. In the second part, we extend our analysis by evaluating the critical effect in the generalized light-nuclei ratio $N_p^{B-A}N_B^{A-1}/N_A^{B-1}$ [4,5] with $N_A$ being the nuclei yield of mass number A. We introduce the critical correction to the phase-space distribution by employing the critical fluctuations from the Ising model. We find that the overall non-monotonic behavior of the yield ratio arises from the increasing correlation length near the critical point. In addition, if the strength of the critical fluctuation is sufficiently significant, the collision energy dependence of the ratio exhibits double peaks by the interplay between the two- and three-point critical corrections.

[1] STAR Collaboration, arXiv:2209.08058 (2022).
[2] K.J.Sun, L.W.Chen, C.M.Ko and Z.Xu, Phys. Lett. B 774, 103-107.
[3] S. Wu, K. Murase, S. Tang and H. Song, Phys. Rev. C 106, 034905 (2022).
[4] S. Wu, K. Murase and H. Song, PoS (LHCP2022) 240.
[5] S. Wu, K. Murase, S. Zhao and H. Song, in preparation.

Speaker: Shanjin Wu

2023_Shanjin_QM.pdf

17:30 Analytic and Semi-Analytic Calculations for Color Glass in the Weak Field Limit

The classical field approximation to Color Glass Condensate for two colliding nuclei has been solved in the literature using numerical methods and recursive analytic solution. In the weak field limit, analytic solutions in transverse momentum space have also been known for some time. Based on the latter, we derive expressions for the space-time dependence of classical gluon 2-point functions $\langle F_{\mu\nu}(x_{\alpha}) F_{\kappa\lambda}(y_{\beta}) \rangle$ in the weak-field limit. For the McLerran-Venugopalan (MV) model, in many cases these expressions are shown to lead to solutions in closed analytic forms valid at all times. We also propose an alternative model which maintains UV-regularity by accounting for local correlations between color charges in the transverse plane, and softens the dependence on the IR-regulator by properly enforcing global color neutrality. The new model allows for a straight forward calculation of the time dependence of the gluon energy momentum tensor in early nuclear collisions in the weak field limit. We also discuss the initial motion of the nuclei after the collision and the momentum broadening coefficient at early times.

Speaker: Stephen Robicheaux

Robicheaux_Poster.pdf

Robicheaux_Poster.pptx

17:30 Anisotropic flow measurements of strange and multi-strange hadrons in isobar collisions at RHIC-STAR

Isobar collisions, $^{96}_{44}$Ru+$^{96}_{44}$Ru and $^{96}_{40}$Zr+$^{96}_{40}$Zr, at $\sqrt{s_{\mathrm {NN}}}$ = 200 GeV have been performed at RHIC. These collisions are considered to be an effective way to minimize the flow-driven background contribution to search for the possibly small CME signal. Anisotropic flow is an important tool to understand properties of the QGP medium. Elliptic flow ($v_{2}$) is the second-order coefficient in the Fourier expansion of the azimuthal angle distribution of produced particles with respect to the reaction plane. Elliptic flow of charged hadrons has been measured in the isobar collisions at $\sqrt{s_{\mathrm {NN}}}$ = 200 GeV. The magnitude of $v_{2}$ shows difference between the two isobar collisions despite the same nucleon number. This indicates a difference in nuclear structure and deformation between these nuclei. The $v_{2}$ measurements of the strange and multi-strange hadrons are excellent probes for understanding these initial state anisotropies of the medium produced in these collisions, owing to their smaller hadronic cross-section compared to light hadrons. The collected datasets include approximately two billion events per isobaric species, offering a unique opportunity for making this statistically hungry measurement.
In this poster, we will report measurements of the elliptic flow of $K_{s}^{0}$, $\Lambda$, $\overline{\Lambda}$, $\phi$, $\Xi^{-}$, $\overline{\Xi}^{+}$, and $\Omega^{-}$+ $\overline{\Omega}^{\ +}$ at mid-rapidity for Ru+Ru and Zr+Zr collisions at $\sqrt{s_{\mathrm {NN}}}$ = 200 GeV. The transverse momentum ($p_{T}$) dependence of $v_{2}$ for minimum bias collisions and various centrality intervals will be shown. The $p_{T}$-integrated $v_{2}$ of these strange and multi-strange hadrons will also be shown. System size dependence of $v_{2}$ will be investigated by comparing the results in isobar collisions with those from Cu+Cu, Au+Au, and U+U collisions. The number of constituent quark (NCQ) scaling for these strange hadrons will also be tested. Experimental data will be compared with transport model calculations to provide insight into the nuclear structure of the isobars.

Speaker: Sonia Kabana (Instituto De Alta Investigación, Universidad de Tarapacá (CL))

17:30 Anomalous kaon correlations in Pb--Pb collisions at the LHC with ALICE

Two-particle correlation functions provide critical information about the medium quark--gluon plasma (QGP) created in heavy-ion collisions. Recent ALICE measurements have demonstrated large dynamical correlations between produced neutral and charged kaons in Pb--Pb collisions at $\sqrt{s_{\rm{NN}}} = 2.76 $ TeV~\cite{ALICE:2021fpb}. These integrated correlations cannot be described by conventional heavy-ion models, such as EPOS and AMPT. So far, the ALICE measurements can only be described by invoking the presence of condensates ~\cite{Kapusta:2022ovq}. A candidate for such a condensate is the Disoriented Chiral Condensate (DCC)~\cite{Mohanty:2005mv}. DCC arises from chiral symmetry restoration in the QGP, which breaks during the phase transition to form a condensate which coherently emits hadrons. Therefore, the discovery of DCC would indicate that chiral symmetry is restored in the QGP, a major prediction of QGP formation that has yet to be confirmed experimentally.

To investigate these anomalous kaon correlations further, a differential analysis of two-particle angular correlation functions of charged and neutral kaons as a function of $\Delta \varphi$ and $\Delta \eta$ in Pb--Pb collisions at $\sqrt{s_{\rm{NN}}} = 5.02 $ TeV is intended. The variables, $\varphi$ and $\eta$ are azimuthal angle and pseudorapidity respectively. The results from a simulation study using HIJING model, as a guide to the future exploration using heavy in data will be presented.

Speaker: Anjaly Menon

QM23_Poster_Anjaly.pdf

17:30 Antiproton production cross sections for dark matter search at the AMBER experiment @CERN

Multiple evidence reveals that the vast majority of the matter content of the universe is non baryonic and electrically neutral. This component is usually called Dark Matter (DM), for its lack of electromagnetic interactions, and is measured to constitute about 25% of the energy density of the Universe. The most common hypothesis is that it consists of weakly interacting massive particles, supposed to be cold thermal relics of the Big-Bang.
The indirect detection of DM is based on the search of the products of DM annihilation or decay. They should appear as distortions in the gamma ray spectra or in anomalies in the rare Cosmic Ray (CR) components. In particular, antimatter components, like antiprotons, antideuterons and positrons, promise to provide sensitivity to DM annihilation on top of the standard astrophysical production.
The interpretation of galactic CR data requires the correct modeling of their source terms and the turbulence spectrum of the galactic magnetic field, in addition to the knowledge of the cross sections that regulate the production of CR interacting with the interstellar medium.
After PAMELA detector results, the antiprotons flux has been measured with an accuracy of a few percent by AMS-02 over an energy range from below 1 GeV up to a few hundreds of GeV. However, the only currently measured production cross section is the proton-proton one, while all the reactions involving helium have no laboratory data in the phase space covered by AMS-02 (only LHCb, but with incident proton energy of 6.5 TeV). This requires a scaling of the pp channel to pA interaction through approximation and modeling.
The AMBER fixed target experiment at the M2 beam line at CERN will contribute to this fundamental DM search, performing a unique and complementary measurement of the double differential antiprotons production cross-section with a proton beam ranging from 60 to 250 GeV/c impinging on a liquid He target.
The data taking for the experimental determination of the cross-section in p+4He scattering is scheduled for May-June 2023. This result from AMBER will directly pin down the production of anti-protons in the relevant kinematical region covered by AMS-02.

Speaker: Mr Davide Giordano (Università degli Studi di Torino / INFN Torino (IT))

Poster_GIORDANO_QM2023.pdf

17:30 Applying the multiplicity-dependent Momentum Kick Model to the pp collisions at $\sqrt{s}=13$ TeV at the LHC

The long-range ($|\Delta\eta| \gt 2$) near-side ($\Delta\phi\approx0$) ridge structure in a two-particle correlation analysis has been observed in heavy ion collision, which was well-explained by the hydrodynamic models based on the quark-gluon plasma (QGP) effect. However, even though small systems such as pp and pPb collisions cannot have enough density and temperature to create the QGP matter, the ridge phenomenon appeared in high multiplicity events of small systems, which is controversial in the hydrodynamic models. Among numerous models to explain this phenomenon in small systems, the Momentum Kick Model (MKM) can give a description of it via a kinematic process where the high-momentum jet particles transfer their momentum to the medium partons called a ``kick" process, leading to collective motion which becomes the ridge phenomenon in the MKM. The MKM has been applied to various experimental data, such as the STAR and the PHENIX, and has shown good agreement. Furthermore, since the ridge yields are dependent on multiplicity in high-energy collision experiments, C. Y. Wong built a multiplicity dependence on the MKM through an impact parameter and applied it to the CMS data for pp collisions at $\sqrt{s}=7$ TeV.
Recently, the CMS Collaboration measured the ridge yields along the different $p_T$ and multiplicity ranges for pp collisions at $\sqrt{s}=13$ TeV. To verify the MKM with multiplicity dependence, we expand the model analysis at 7 TeV to those at 13 TeV and provide the theoretical basis on two questions raised by the CMS Collaboration; the linearity of the ridge yield with multiplicity and the prominence at the middle $p_T$ range. Moreover, the CMS Collaboration suggested that the ridge structure does not have the collision energy dependence for pp collisions by comparing the ridge yields at 7 TeV with those at 13 TeV. From this surmise, we predict the future ridge behavior of the LHC Run3 at $\sqrt{s}=5.3$ and $8.5$ TeV.

Speaker: Jeongseok Yoon (Inha University (KR))

QM2023_JS_ver4.pdf

17:30 Azimuthal correlations of heavy-flavor decay electrons and charged particles with the ALICE detector

Heavy-flavor (charm and beauty) quarks are generated primarily via hard scattering processes in high-energy hadronic collisions, and then undergo parton shower (fragmentation) and hadronization. Two-particle azimuthal correlations of heavy-flavor particles is a differential measurement which allows for the study of the fragmentation of heavy quarks. By measuring the azimuthal correlation in different transverse momentum ($p_T$) regions, one can study the details of the structure and particle momentum distribution of jets produced by the heavy-quark fragmentation process. The azimuthal correlations between electrons from heavy-flavor decays (trigger) and charged particles (associated) are studied in different trigger and associate particle $p_T$ regions. A distinguishing feature of heavy-ion collisions is the production of a hot and deconfined state of nuclear matter, called Quark Gluon Plasma (QGP). By comparing the heavy-flavor and charged particle azimuthal correlations in Pb-Pb collisions to measurements in smaller collision systems, we can determine how the heavy-quark fragmentation is modified by interactions with the QGP medium. In this poster, ALICE results on the modifications of the azimuthal distribution in Pb-Pb collisions with respect to pp collisions will be presented. The results in pp and p-Pb collision systems will also be shown and compared to predictions from Monte Carlo simulations.

Speaker: Amanda Nicole Flores (University of Texas at Austin (US))

QM_Poster_2023_AFlores_Draft6.pdf

17:30 b-hadron v$_2$ and R$_{AA}$ with sPHENIX

The beauty quark is a unique probe to study the properties of quark-gluon plasma thanks to its large mass and relatively long thermal relaxation time compared with lighter partons. Traditional experimental observables such as elliptic flow v$_2$ and nuclear modification factor R$_{AA}$ of fully reconstructed beauty hadrons have been measured at the LHC. Moreover, indirect measurements on non-prompt D-mesons and heavy flavor decayed leptons have been carried out extensively. The sPHENIX experiment at RHIC is a state-of-the-art heavy flavor and jet detector. sPHENIX will begin commissioning with Au+Au collisions in Spring 2023. The Monolithic-Active-Pixel-Sensor (MAPS) based VerTeX detector (MVTX) is a high precision silicon pixel detector. The MVTX provides excellent position resolution and capability of operating in continuous streaming readout mode, allowing precise vertex determination and recording a large data sample, both of which are particularly crucial for b-hadron measurements. In this poster, we will discuss projections of inclusive b-hadron v$_2$ and R$_{AA}$ measurements and discuss the expected constraints on theoretical models. We will also report on the status of b-physics analysis.

Speaker: Dr Zhaozhong Shi (Los Alamos National Laboratory)

Quark Matter 2023 Final Draft.pdf

17:30 b-jet tagging at sPHENIX

Beauty quarks are produced in hard-parton scatterings in the early stages of the partonic collisions. They are the ideal probe to investigate the properties of Quark-Gluon Plasma (QGP) produced in ultra-relativistic heavy-ion collisions as they experience the whole QGP evolution. Due to their large mass, their production can be calculated using perturbative Quantum Chromodynamics (pQCD), thus they can be used to test pQCD based models. Moreover, measurements in p+p collisions provide the necessary reference for the interpretation of heavy-ion collision results. Experimentally, tagging a jet by its flavor content gives direct access to the initial parton kinematics and can provide information on how the energy is dissipated in the QGP medium. The possible studies include the flavor and mass dependence of jet quenching, the collisional energy loss, the dead-cone effect, and the modification of the fragmentation and jet structure in the medium.
The sPHENIX detector will begin commissioning with Au + Au collisions in Spring 2023. It provides an excellent vertex resolution using 3 layers of Monolithic Active Pixel Sensors (MAPS) and Intermediate Silicon Tracker (INTT) detectors. The expected spatial resolution is <6μm and the track vertex distance of closest approach (DCA) <30 $\mu$m for p$_T$>1 GeV/c. In addition, a full azimuthal coverage of electromagnetic and hadronic calorimeters provides an excellent tool to study jet physics. In this poster, we will focus on the prospects of beauty-jet-tagging of full jets at sPHENIX. Several methods are studied in simulation, including tagging via the large DCA track and secondary vertex mass.

Speaker: Jakub Kvapil (Los Alamos National Laboratory (US))

QM2023_bjets_JK_A0_final.pdf

17:30 Baryon stopping from the bremsstrahlung photon spectrum

In ultra-relativistic heavy-ion collisions, the colliding nuclei are decelerated and kinetic energy is converted into new particles. This energy loss is referred to as baryon stopping. A fundamental question one can ask in the study of high energy heavy-ion collisions is how much baryon stopping there is. This can be quantified by measuring the net proton rapidity distributions. Previous measurements at RHIC and in fixed target experiments have shown that the amount of stopping decreases with increasing collision energy. At LHC energies, there are no experimental constraints beyond the central rapidity region, where there are no net protons.

In order to investigate the net proton distribution at LHC energies beyond mid-rapidity, we propose using the bremsstrahlung photons emitted from the nuclei as they slow down. In our recent study [1], we investigated stopping scenarios which are based on model calculations or phenomenology and consistent with existing data. Furthermore, we performed a detailed estimate of the background from hadronically produced photons, using the PYTHIA 8.3 event generator, aiming to investigate in which areas of phase space the bremsstrahlung photons constitute a viable observable for baryon stopping. The bremsstrahlung spectra are highly sensitive to the amount of nuclear stopping, and depending on the scenario, a significant signal over background is obtained for pseudorapidities η>∼4−5 and for photon energies ω<∼300−500MeV.

Here, we expand our investigation to include the baryon stopping predicted by the EPOS4 event generator for PbPb collisions at sqrt(sNN)=5.02TeV. EPOS4 gives zero net protons at mid-rapidity, making the bremsstrahlung spectrum from this stopping scenario plausible.

Furthermore, we discuss the bremsstrahlung spectrum coming from proton-proton collisions, which gives insight into the charge dependence of the signal to background ratio of bremsstrahlung photons in hadron collisions.

[1] S. Nese and J. Nystrand, Eur. Phys. J. C 83 (2013) 14. arXiv:2210.16200.

Speaker: Sigurd Nese (University of Oslo (NO))

portrait.pdf

17:30 Baryon-Strangeness Correlations in $\sqrt{s_{NN}}$ = 3 GeV Au+Au Collisions from RHIC-STAR Fixed-Target Experiment

Fluctuations of conserved quantities are proposed as a powerful observable to search for the QCD critical point. Recently, proton cumulants from central Au+Au $\sqrt{s_{NN}}$ = 3 GeV collisions were reported, which implies that hadronic interactions are dominant at 3 GeV and the QCD critical point could exist at the collision energies higher than 3 GeV. The baryon-strangeness correlation is expected to deviate from the QGP expectation for the hadronic gas at high baryon-chemical potential region, which can be used to confirm the turning-off signal of the QGP. Previously, the STAR measurement of baryon-strangeness correlation using (anti)protons and $\rm K^{\pm}$ shows no strong signal compared with theoretical prediction. So it is suggested to include hyperons in the measurement to study QCD phase transition.

In this poster, we will report the second-order baryon-strangeness correlation using proton, $\rm K^{\pm}$, and $\Lambda$ in Au+Au collisions at $\sqrt{s_{NN}}$ = 3 GeV from the fixed-target program at the STAR experiment. Protons and $\rm K^{\pm}$ are identified using TPC and TOF detectors, while $\Lambda$ is reconstructed by the invariant mass method. Physics implications of the results, as well as comparisons with model calculations, will be discussed.

Speaker: Dr Yu Zhang (Central China Normal University)

QM2023_poster_YuZhang.pdf

17:30 Baseline fluctuation studies for the sPHENIX TPC readout

The sPHENIX TPC readout will use an array of quadruple-stacked gas electron multiplier (GEM) modules to amplify signals from the chamber in order to perform precise tracking measurements. The performance of the system may be affected by a shift in the readout baseline due to event-by-event fluctuations. These fluctuations are a result of the common-mode noise generated in the induction gap of the readout as well as the ion tails on the signals caused by capacitive coupling between the bottom GEM and pad plane of each module. Understanding and accounting for this baseline shift is necessary to avoid degradation in the tracking performance of the TPC. We will present studies done to investigate the baseline shift of the sPHENIX TPC readout along with the methods used to correct for it.

Speaker: Luke Legnosky (Stony Brook University)

Baseline Shift Analysis Poster.pdf

17:30 Bulk Viscosity of Hadronic Matter from a Microscopic Transport Model

Ultra-relativistic heavy-ion collisions at RHIC are thought to have created a Quark-Gluon-Plasma (QGP) with a very low shear viscosity in the deconfined phase. However, as the QGP hadronizes it will evolve through a hadronic phase with rapidly increasing shear viscosity. In order to fully characterize the QGP state, one has to separately determine the viscosity of the hadronic phase. Although many approaches have been used to determine the shear viscosity coefficient and the associated shear viscosity to entropy density ratio ($\frac{\eta}{s}$) in the hadronic phase, much is unknown regarding the bulk viscosity to shear viscosity coefficient ($\frac{\zeta}{s})$ in the hadronic phase. We present preliminary results of a calculation of the bulk viscosity $\zeta$ and the bulk viscosity to entropy density ratio $\frac{\zeta}{s}$ for hot hadronic matter. The Ultrarelativistic Quantum Molecular Dynamics (UrQMD) model is used to simulate the hadronic medium and periodic boundary conditions are used to simulate infinite hot equilibriated hadronic matter. The Green-Kubo formalism is employed and a comparison is made with the results of the bulk viscosity calculation from the Simulating Many Accelerated Strongly Interacting Hadrons (SMASH) model from [1].
[1] J.B Rose et al 2021 J. Phys. G: Nucl. Part. Phys. 48 015005

Speaker: Nasser Demir (Kuwait University (KW))

Poster_QM2023_Demir.pdf

17:30 Calibrated Cosmic Muon simulations for the sPHENIX Hadronic Calorimeters

The sPHENIX detector at Brookhaven National Laboratory’s (BNL) Relativistic Heavy Ion Collider (RHIC) is scheduled to begin data acquisition in 2023. Its primary objective is to investigate the microscopic properties of the Quark-Gluon Plasma (QGP) through high-precision measurements of jets and heavy flavor observables. A key feature of the sPHENIX detector is the inclusion of hadronic calorimeters (HCals) at mid-rapidity, which are essential for the jet physics program. Accurate jet reconstruction demands properly calibrated sPHENIX calorimeter systems during the entire data collection process. This study aims to build on previous cosmic testing efforts, which were conducted using individual HCal sectors in test benches, by investigating the potential for cosmic calibration with the complete sPHENIX apparatus in its data-taking position. In this poster, we will present a GEANT4-based study that employs a cosmic muon generator with a realistic zenith angle and energy distribution to examine the possibility of calibrating the HCals to the Minimum Ionizing Particle (MIP) scale using cosmic muon events. The muon rate predictions and observations will be utilized to plan routine cosmic running, ensuring the maintenance of the calibration for the lifetime of the sPHENIX experiment.

Speaker: Shuhang Li

sli_QM23poster_final.pdf

17:30 Calorimeter Calibrations Methods from RHIC to EIC

With the advent of the Electron Ion Collider, which will involve many diverse calorimeter systems, and the switch to SiPM readouts which has been occuring over the past ~decade, new techniques in calorimeter calibrations are needed. These should address for example, gain tracing vs time, where siPM's can be more sensitive to temperature fluctuations, and also position dependencies in response, due to siPM light collection being less uniform than with traditional PMT's. We review several calibrations methods used for calibrating both hadronic and electromagnetic calorimeters at RHIC, LHC, and elsewhere, and also explore some possibilities for use at the upcoming EIC Facility. This includes several novel techniques developed for use at RHIC by our group. We will discuss calorimeter systems being planned for the ePIC experiment and specifically how the various methods, including ours, can be used there.

Speaker: Justin Edward Frantz

17:30 Characterising collectivity with virtual photons at HADES

Electromagnetic probes have been established as promising tools to study early times in the collision system of maximum temperature and density.

In this contribution, a focus is set on the investigation of collective observables. Namely, the directed flow $v_1$, elliptic flow $v_2$ as well as the radial flow of virtual photons are measured. After the isolation of the thermal contribution, a systematic study as a function of the invariant mass may allow unique insights into the time evolution of the systems collectivity.

The analysis is based on Ag+Ag collisions collected at the High-Acceptance-DiElectron-Spectrometer (HADES) at $\sqrt{s_{NN}}=2.55$ GeV and $\sqrt{s_{NN}}=2.42$ GeV. Therefore, the created matter is characterised by high baryon densities and moderate temperatures, similar to neutron star mergers, and serves as an important reference to deliver constraints to the equation of state.

Speaker: Niklas Schild

Poster_QuarkMatter2023_NiklasSchild.pdf

17:30 Characterising the initial conditions and probing the nuclear structure with multiparticle correlations techniques at ALICE

High-energy heavy-ion collisions offer a unique and precise way to probe nuclear structures by providing a snapshot of the nuclear distribution at the time of the collision, which is complementary to low-energy nuclear physics experiments.

In this talk, we present a comprehensive scan of flow observables, including anisotropic flow coefficients, nonlinear flow modes, and normalized symmetric cumulants, in Pb--Pb and Xe--Xe collisions measured with ALICE at $\sqrt{s_\mathrm{NN}} =$ 5.02 and 5.44 TeV, respectively. These measurements can probe distinctive nuclear structures (i.e., quadrupole deformation) in central collisions and the size of the $^{208}$Pb neutron skin in midcentral to peripheral collisions. The measurements of multiparticle cumulants of mean transverse momentum, $[p_\mathrm{T}]$, allow us to probe the size and its fluctuations in the initial state. Furthermore, we present the first measurements of newly proposed multiparticle cumulants between anisotropic flow $v_{\rm n}^{\rm m}$ (m = 2,4) and mean transverse momentum correlations $[p_\mathrm{T}^{(k)}]$ (k $\leq$ 4), in both Pb--Pb and Xe--Xe collisions. The presented measurements and comparisons to the state-of-the-art theoretical model calculations show unambiguous evidence of a deformed and triaxial structure for $^{129}$Xe, and in Pb--Pb collisions further provide tight constraints to the nucleon width $w$, which was poorly controlled before. These studies enormously improve our understanding of the initial conditions of heavy-ion collisions and allow us to explore LHC's full potential as a robust nuclear physics machine.

Speaker: Emil Gorm Nielsen (University of Copenhagen (DK))

poster_QM23_egnielsen.pdf

17:30 Characterization of Static Distortions in the sPHENIX TPC with a Steerable Laser System

The sPHENIX Time Projection Chamber (TPC) is a gaseous drift detector
designed to measure charged particle tracks. It is filled with Argon/CF4 and uses
Gaseous Electron Multiplier (GEM) foils at readout for electron amplification
and ion back-flow suppression. The electrons at readout are measured, converted
to digital current, and their signal waveforms are processed to reconstruct the track.
At this stage, the positions of hits and clusters along the track can be measured.
A successful measurement of these hits and clusters must correct for
distortion effects present in the TPC. There are three primary sources of distortion: static
distortions from E and B fields, average distortion from space charge, and event-by-event distortions due to fluctuations in space charge. This poster focuses on
a novel technique to measure the static distortions using a system of steerable
ionizing lasers. These provide straight tracks at many different angles with
an ability to sample the entire TPC volume between periods when beam is
present. These laser induced tracks are used measure the distortions from non-uniform
and slightly misaligned drift electric fields and solenoidal magnet fields in single
voxels of the TPC. From these measurements, one can determine the static
distortion correction. This poster presents the methodology by which the TPC
volume is sampled by steering the laser and how the distortions are measured
from reconstructed laser data.

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

Charles_QM_23_Poster_v5.pdf

17:30 Characterization of Time Dependent Distortions in the sPHENIX TPC using the Central Membrane

The Time Projection Chamber (TPC) is the main tracking detector in sPHENIX. Charged particles which pass through the TPC ionize the gas, with the transverse position being given by the readout pad and the time for the ionization electrons to drift to the endcaps defining the z position. The ionization electrons are clustered together in order to track particles and determine their momenta. In order to accurately track particles, calibrations must be performed and the performance of the TPC must be understood. As part of normal operation, space charge builds up within the TPC, leading to tracking distortions. These distortions must be accurately characterized over time such that they can be corrected as they evolve. Several calibration systems are used for this, including a set of diffuse lasers which illuminate the Central Membrane of the TPC. Aluminum stripes, deposited on the Central Membrane at well-surveyed positions, emit photoelectrons when struck by the diffuse laser. The resulting pattern can be reconstructed and used to characterize the 3-dimensional distortions at the position of the Central Membrane. These distortions are then extrapolated to the endcaps of the TPC in order to provide corrections throughout its entire volume. This poster will discuss the design, the algorithm, and the performance of the time dependent distortion corrections in the sPHENIX TPC and identify how this effort fits into the broader sPHENIX TPC calibration scheme.

Speaker: Benjamin Kimelman (Vanderbilt University)

Kimelman_QM2023_Poster_v6.pdf

17:30 Characterizing Time-Averaged Distortions in the sPHENIX TPC with the TPC Outer Tracker

The sPHENIX Time Projection Chamber (TPC) serves as the main tracking detector of the sPHENIX experiment, which began operating at the Relativistic Heavy Ion Collider at Brookhaven National Lab this year. It operates with a quadruple-GEM avalanche stage which provides gain while restricting the flow of ions back into the chamber sufficiently to operate in streaming mode, without any additional gating. However, in order to reach its design performance, the time-varying distortions due to the fields of the remaining ion backflow and primary ionization must be monitored and corrected. The slowly varying component of the distortions is monitored by the TPC Outer Tracker (TPOT), a micromegas-based detector which provides an additional spacepoint for tracks within a limited azimuthal range. This spacepoint enables a data-driven extraction of the distortion vectors within the detector, which can then be extrapolated to the entire chamber. This poster presents the design of the TPOT and methods used to extract the appropriate corrections to these moderate-timescale distortions

Speaker: Bade Saykı (Los Alamos National Laboratory)

17:30 Charged kaon and pion femtoscopy in the RHIC Beam Energy Scan at the STAR experiment

The RHIC Beam Energy Scan (BES) program aims to study the properties of strongly interacting matter in relativistic heavy-ion collisions at various energy densities and temperatures. Correlation femtoscopy technique is a useful tool to study systems undergoing QCD phase transitions, and can extract valuable information about the size, shape, and lifetime of the particle-emitting source in heavy-ion collisions.

This study presents the first comprehensive femtoscopic analysis of identical kaons and pions produced in Au+Au collisions at $\sqrt{s_{NN}}$ = 14.6 - 200 GeV from the RHIC Beam Energy Scan phases I and II, focusing on charge, transverse momentum, and centrality-dependent properties. The charge-dependent analysis reveals differences at the level of correlation functions for both kaons and pions for the first time at these energies. This observation is consistent with Coulomb field effect due to residual charge after the collision and hadronic final state effects, as implemented in UrQMD. The three-dimensional femtoscopic analysis reveals that the extracted radii, assuming Gaussian distribution for emission source, increase with collision energy, decrease with transverse mass, and are generally larger for kaons compared to pions under the same conditions. The study compares experimental data with different model scenarios and discusses the implications of the trend of the extracted size and lifetime of the particle source with the change of collision energy.

An analysis of one-dimensional two-pion and two-kaon correlations in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV, utilizing Levy-stable distributions for the source shapes, is also presented. The current analysis status of the extracted Levy source parameters, including their dependence on average transverse mass and centrality, is reported. A comparison of the pion and kaon Levy exponent is presented, potentially shedding light on the deviation from the Gaussian approximation of the emission source. The obtained results are compared to UrQMD and EPOS model calculations.

Speaker: Eugenia Khyzhniak

KhyzhniakPosterQMVer5.pdf

17:30 Charged particle multiplicity distribution in Pb-Pb collisions at $\sqrt{s_\mathrm{NN}}$ = 5.36 TeV with ALICE

The multiplicity distribution measures the probability of obtaining a certain number of particles in a given collision and is one of the first observables measured in data at each new collision type and center of mass energy. It is relevant since is one of the fundamental observables to describe the global properties of the interactions and is sensitive to non-linear QCD evolution in the initial state. We will present the multiplicity distribution, P(N_\mathrm{ch}), for Pb-Pb collisions at \sqrt{s_\mathrm{NN}} = 5.36 TeV. The analysis relies on tracks reconstructed with ALICE's upgraded Inner Tracking System (ITS) using new LHC data from Run3 pilot Pb-Pb run. A detailed comparison with predictions from the PYTHIA 8 and EPOS LHC event generators is also presented.

Speaker: Hyungjun Lee (Sungkyunkwan University (KR))

17:30 Charged particle multiplicity distribution in pp collisions at $\sqrt{s}$ = 13.6 TeV with ALICE

Multiplicity distributions of primary charged particles are sensitive to non-linear QCD evolution in the initial state. We present the distributions in various pseudorapidity ranges in proton-proton collisions at $\sqrt{s}$ = 13.6 TeV. Charged particles are reconstructed using the Inner Tracking System that has been upgraded for Run3 at LHC and is operation starting in 2022. The data are compared to models with recent PYTHIA 8, EPOS-LHC, and EPOS 3.

Speaker: Mr Joonsuk Bae (Sungkyunkwan University (KR))

QM2023_poster_JBae_LeeHY_6.pdf

17:30 Charged-particle multiplicity measurement in Au+Au collisions at $\sqrt{s_{\rm{NN}}}$ = 200 GeV with sPHENIX at RHIC

sPHENIX, the first detector to be built at the Relativistic Heavy-Ion Collider (RHIC) in over two decades, will bring unprecedented measurement capabilities at RHIC energies. One of the initial physics measurements to be performed by sPHENIX concerns the charged-particle multiplicity, which utilizes the tracklet analysis method with the cluster information from the Monolithic-Active-Pixel-Sensor-based Vertex detector (MVTX). This measurement serves to directly demonstrate, based on real collision data, that the MVTX readout and clustering are operational. Additionally, this analysis technique provides an alternative diagnostic tool for detector alignment and vertex finding, both of which are critical components of the tracking system that will enable the entire physics program of sPHENIX. The projected performance of the measurement will be presented, and the status of the analysis on 2023 Au+Au data will be discussed.

Speaker: Hao-Ren Jheng (Massachusetts Inst. of Technology (US))

QM2023-HaoRenJheng-v4.pdf

17:30 Charm production in various scenarios of the QGP evolution

We study the production of charm quarks in hot QCD medium described by quasiparticle excitations of quarks and gluons. The effective masses are adjusted through the coupling to satisfy the entropy density obtained on the lattice [1]. The evolution of the QGP is described by hydrodynamic simulations in (2+1) dimensions with temperature-dependent shear viscosity taken into account [1,2]. The temperature and time evolution of the charm quark number obtained in the above-described scenario is further juxtaposed to the results acquired from ideal QGP obeying Bjorken flow. We observe a suppression of charm quark production in the absence of shear viscosity and transverse expansion [3]. Moreover, we compute the charm quark fugacity by solving the rate equation and find that it exhibits a global attracting solution, specific to the differential equations [4].

[1] V. Mykhaylova, M. Bluhm, C. Sasaki, K. Redlich, Phys.Rev.D 100 (2019).
[2] J.Auvinen, K. J. Eskola, P. Huovinen, H. Niemi, H.Paatelainen, Phys.Rev.C 102 (2020).
[3] V. Mykhaylova, Transport Properties of Hot QCD Matter in the Quasiparticle Approach (PhD Thesis, 2023).
[4] V. Mykhaylova, EPJ Web Conf. 274 (2022) 05006.

Speaker: Valeriya Mykhaylova (University of Wrocław)

17:30 Charmonium production measurement at midrapidity using TRD-triggered data in ALICE

Quarkonium production is considered one of the golden probes of the quark-gluon plasma (QGP) formation in heavy-ion collisions.
Due to their large mass, the production of heavy-quarks is governed by hard scales of QCD, while the formation of the bound quarkonium state involves soft QCD scales.
The regeneration process of J/$\psi$ in the QGP or at the phase boundary is crucial for describing the observed centrality, rapidity, and $p_{\mathrm T}$ dependence of J/$\psi$ nuclear modification factor at the LHC.
Quarkonium production in more dilute systems is essential to provide a baseline for Pb--Pb results.
They are also useful for investigating the production mechanisms for pp collisions and studying the cold nuclear matter effect for p--Pb collisions.
The $\psi$(2S) production relative to J/$\psi$ is observable with strong discriminating power between the two regeneration scenarios in Pb--Pb collisions, as well as among quarkonium production models in pp and p--Pb systems.
Thanks to the ALICE online single-electron triggers from the Transition Radiation Detector (TRD), the $\psi$(2S) signal can be extracted at midrapidity in the dielectron channel.

In this contribution, the first studies on J/$\psi$ and $\psi$(2S) productions at midrapidity with the TRD-triggered data measured in ALICE in pp collisions at $\sqrt{s} = 13$ TeV will be shown for the first time, along with recently published  J/$\psi$ results based on TRD-triggered data in p--Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 8.16$ TeV.

Speaker: Jinjoo Seo (Inha University (KR))

QM2023_poster_jj_v7.pdf

17:30 Chiral critical point via scalar-dilaton coupling in soft-wall AdS/QCD

The AdS/CFT correspondence, which connects strongly coupled conformal field theories in $N$ dimensions to gravity in $N+1$ dimensional Anti-de Sitter space, has provided valuable insights into the non-perturbative aspects of QCD. Soft-wall AdS/QCD is a phenomenological model that uses a dilaton field to introduce confinement, while a scalar field is dual to the chiral condensate. The thermodynamics of the deconfined state are introduced using an asymptotically AdS Reissner-Nordström black hole, which includes both temperature and baryon chemical potential. Minimal models of this type yield a chiral phase transition that is not affected by the chemical potential, and thus lack a critical point.

In this work, we investigate the chiral phase transition in an AdS/QCD action that includes a coupling between the scalar and dilaton fields. Our results reveal that the scalar-dilaton coupling produces a rich phase structure, with the emergence of a critical point at finite temperature and density. The location and presence of the critical point is found to be highly sensitive to the strength of the scalar-dilaton coupling. We present results for both 3-flavor symmetric and 2+1 flavor cases. This work provides a foundation for future phenomenological applications, as well as dynamical models, which solve the scalar and dilaton fields using the gravitational equations of motion.

Speaker: Sean Bartz (Indiana State University)

17:30 Clocking the particle production and tracking radial flow effects at top LHC Run 3 energy with ALICE

Balance functions have been extensively used to elucidate the time evolution of quark production in heavy-ion collisions. Early models predicted two stages in the quark production, one for light quarks and one for the slightly heavier strange quark, separated by a period of isentropic expansion. This led to the notion of clocking the particle production and tracking radial flow effects. The evolution of the azimuthal widths of the Balance functions has been later associated to the diffusivity of light quarks.

In this contribution, Balance functions in different multiplicity classes of pp Run 3 collisions at $\sqrt{s} = 13.6\;\text{TeV}$ recorded by ALICE are reported and compared with ALICE published results on pp collisions at $\sqrt{s} = 7\;\text{TeV}$. Results not only allow to validate the new data-taking machinery and analysis framework but also shed light on the evolution of Balance functions, their widths, and integral, with the collision energy. with the collision energy.

Speaker: Brian Gerald Hanley (Wayne State University (US))

QM2023PosterDraft19.pdf

17:30 Clustering hits of Time Projection Chamber by using machine learning and neural networks at sPHENIX

The Time Projection Chamber (TPC) at sPHENIX provides particle tracking over pseudorapidity $|\eta| <$ 1.1, and plays a key role in the planned jet and heavy-flavor measurements. The electrons created through ionization of the TPC gas by charged particles produce hits on the TPC readout plane, from which clusters for track reconstruction need to be formed. The traditional method of grouping connected hits into clusters, known as connected component analysis (CCA), becomes less effective in high-multiplicity events, such as Au+Au collisions with event pileup from multiple beam crossings, due to effects from $\delta$-electrons and the high occupancy. A neural network (NN) clustering method, which uses an NN to predict the cluster position based on the distribution of hits, is supposed to improve the clustering performance. We simulate high-multiplicity events and the sPHENIX detector response and train the NN to predict the associated truth cluster position based on the distribution of the reconstructed hits. We will show the implementation of NN clustering at sPHENIX and our plans to enhance its performance by improving truth-information association and fine-tuning the parameters of the NN.

Speaker: Dr ZHONGLING JI (UCLA)

sphenix-tpc.pdf

17:30 Coalescence production of charmonium states in heavy ion collisions

We study charmonium states, J/ψ, ψ(2S), and χc1(1P) mesons in heavy ion collisions by focusing on their production from charm and anti-charm quarks in a quark-gluon plasma by coalescence. Starting from the investigation on the difference in their internal structures, or different wave functions of charmonium states we calculate the yield and transverse momentum distributions of charmonium states produced in heavy ion collisions. We show that the wave function distribution plays a significant role, especially, in the production of charmonium states, leading to the transverse momentum distribution of the ψ(2S) meson as large as that of the J/ψ meson. We also discuss the anisotropic flow, or elliptic and triangular flow of charmonium states using the transverse momentum distribution of charmonium states. We find that the internal structure differences as well as feed-down contributions of charmonium states are averaged out for elliptic and triangular flow, resulting in similar elliptic and triangular flow for all charmonium states. Based on our evaluation of elliptic and triangular flow of charmonium states we also discuss the quark number scaling of elliptic and triangular flow for charmonium states in heavy ion collisions.

Speaker: Sungtae Cho

QM2023_Poster_SCHO.pdf

17:30 Collision event plane determination in sPHENIX at RHIC

Many physics observables of interest in heavy-ion collisions require knowledge of the collision geometry. Geometric fluctuations lead to different symmetry planes of the initial geometry for each harmonic number, called participant planes. As the produced medium evolves, pressure gradients transform the initial state spatial anisotropy into final state momentum anisotropy. The angular distribution of particles can be described via Fourier coefficients $v_n$. The participant planes can be approximated via event planes, $\psi_n$, which are determined from measured azimuthal distribution of particles produced in the collision. This poster reports the methods used for event plane determination in sPHENIX as well as the performance using a variety of sPHENIX subsystems based on simulation using a realistic GEANT description of the experiment. Initial results from the first data run will also be discussed..

Speaker: Ejiro Naomi Umaka (Brookhaven National Laboratory (US))

EjiroUQMposterv2_1.pdf

17:30 Color-superconductivity of asymptotically conformal quark matter as a portal between astrophysics and heavy ions collisions

We present a relativistic density functional approach to color superconducting quark matter that mimics quark confinement by a fast growth of the quasiparticle self-energy in the confining region [1]. The approach is shown to be equivalent to a chiral model of quark matter with medium dependent couplings. The approach to the conformal limit at asymptotically high densities is provided by a medium dependence of the vector-isoscalar, vector-isovector and diquark couplings motivated by non-perturbative gluon exchange [2]. While the (pseudo)scalar, vector-isoscalar and vector-isovector sectors of the model are fitted to the mesonic mass spectrum and vacuum phenomenology of QCD, the strength of interaction in the diquark channel is varied in order to obtain the best agreement with the observational constraints from measurements of mass, radius and tidal deformability of neutron stars. These constraints favor an early onset of deconfinement and color superconductivity in neutron stars with masses below one solar mass. We also discuss a new two-zone interpolation scheme for the construction of the hadron-to-quark matter transition [3] that allows to test different structures of the QCD phase diagram with one, two or no critical endpoints in simulations of supernova explosions, neutron star mergers and heavy-ion collisions. We argue that the formation of color-superconducting quark matter drives the trajectories of its evolution in supernovae and neutron star mergers towards the regimes reached in terrestrial experiments with relativistic heavy ion collisions.

[1] O. Ivanytskyi and D. Blaschke, Phys. Rev. D 105, 114042 (2022)
[2] O. Ivanytskyi and D. Blaschke, Particles 5, 514 (2022)
[3] O. Ivanytskyi and D. Blaschke, Eur. Phys. J A. 58, 152 (2022)

Speaker: Oleksii Ivanytskyi (University of Wroclaw)

17:30 Combined Streaming and Triggered data taking with the sPHENIX Detector

The new sPHENIX detector at RHIC will begin commissioning with Au+Au collisions at 200 GeV in Spring 2023, followed by p+p and p+Au data taking in 2024. The experiment combines triggered readout of the calorimeter system with streaming readout of the tracking detectors in a hybrid readout scheme. The hybrid readout scheme enables a large increase in the collected statistics in particular for p+p and p+Pb collisions at RHIC, leading to an enhancement in integrated luminosity for low p$_T$ heavy-flavor measurements by more than two orders of magnitude.

We will present an overview of the detectors and their readout, the design and functioning of the DAQ system, and its performance. We will explain how sPHENIX has implemented the streaming readout, which is the planned readout mode for future experiments like, e.g., ePIC, for the participating detector systems. The operational and performance experience in the first data taking run will be discussed, and the event statistics collected for key physics channels will be presented.

Speaker: Martin Lothar Purschke (Brookhaven National Laboratory (US))

17:30 Conserved number fluctuations under global rotation in a hadron resonance gas model

Net-charge, net-strangeness and net-baryon number fluctuations measured in ultra-relativistic heavy-ion collisions may reveal details and insights into the quark-hadron transition, hadro-chemical freeze-out and possibly aid in the search of the QCD critical point. By controlling the collision energy, some current and upcoming heavy-ion facilities aim to study high energy nucleus-nucleus collisions in the finite net-baryon density regime where the effects of rapid global rotation are also expected to be strong for the peripheral collisions. We discuss the ratios of conserved number susceptibilities that are experimentally measurable via products of the moments of the corresponding distributions and compute the relevant theoretical results in the framework of a rotating hadron resonance gas (rHRG) model.

Speaker: Gaurav Mukherjee (Bhabha Atomic Research Centre, Homi Bhabha National Institute)

Poster_QM23_fluc.pdf

17:30 Construction of the sPHENIX Event Plane Detector

Constructed at Lehigh University between 2021 and 2023, the sPHENIX Event Plane Detector (sEPD) will measure charged particle multiplicity at forward rapidity from the collision of hadrons. This detector consists of 24 triangular sectors, each of which is divided into 31 optically isolated tiles of plastic scintillating material, such that light can be collected from a discrete area of the detector then converted later to an electronic signal. A wavelength shifting fiber is glued into each tile using an optical epoxy with an index of refraction matching that of the scintillator. The tiles cover 16 segments in $\eta$ and 24 in $\phi$. The sectors were installed into two disks covering a pseudorapidity of 2.1 < |$\eta$| < 4.9. To build the detector, scintillating plastic was milled into a triangular shape to create 24 sectors. Grooves for the optical fibers were then machined into the sectors, in addition to channels to divide each sector into 31 tiles. Optical fibers were then glued into the grooves, and the channels were filled with a reflective epoxy to achieve optical isolation between tiles. An overview of this construction process will be given in detail, including the machining of the sectors, the installation of the fibers in the tiles, and the creation of two types of bundles of fiber optic assemblies.

This material is based upon work supported by the National Science Foundation under Grant No. 2117773.

Speaker: Valerie Wolfe (Lehigh University)

VWOLFE_QM_2023.pdf

17:30 Correlation of flow coefficients measured in Au+Au collisions at 1.23 AGeV with HADES

HADES has a large acceptance as well as excellent particle identification capabilities and therefore allows the study of dielectron, hadron, and light nuclei production in heavy-ion collisions with great precision. The harmonic flow coefficients $v_n$ of the order $n = 1 − 6$ are measured with HADES as a function of centrality, transverse momentum, and rapidity in Au+Au collisions at 1.23 AGeV. Combining them allows to construct for the first time a complete, multi-differential picture of the emission pattern as a function of rapidity and transverse momentum.

The predictions of ideal hydrodynamic simulations, confirmed by transport model calculations, suggest a scaling between various flow coefficients. For protons at mid-rapidity the ratio $v_{4}/(v_{2})^{2}$ is found to be close to 0.5. The correlations of flow coefficients are investigated based on an event-by-event selection of the mid-rapidity final state elliptic flow of protons. The correlations are compared to the results of transport models and to eccentricity calculations within the Glauber Monte Carlo approach.

This work is supported by the Helmholtz Forschungsakademie HFHF.

Speaker: Christoph Blume (Goethe University Frankfurt (DE))

QM2023_Poster_HADES_Flow_2023_09_kardan_03_PDFX3.pdf

17:30 Correlations of conserved charges at finite density

Correlations involving the seven conserved quantities, $\{E,\vec{p},Q,S,B\}$, were modeled for heay-ion collisions at finite baryon density. The evolution of correlations as a function of relative rapidity was treated as a linear response to local thermodynamic fluctuations of on the Bjorken-model background. The entire 7x7 matrix of correlations was found to be significant, sensetive to the EoS, viscosity and diffusivity. Oportunities for experimental observation will be presented.

Speaker: Mr Oleh Savchuk (Bogolyubov Institute for Theoretical Physics and Facility for Rare Isotope Beams)

Savchuk_QM23.pdf

17:30 Correlations of net-charge, net-kaon and net-proton in Pb-Pb at $\sqrt{s_\mathrm{NN}}$ = 5.02 TeV with ALICE

Correlations between net-conserved quantities such as net-baryon, net-charge and net-strangeness are essential probes of QCD phase structure and are related to the ratios of thermodynamic susceptibilities in lattice QCD calculations. The study of these correlations can probe thermal conditions in a medium and help to elucidate the nature of the strongly interacting matter formed in high-energy nuclear collisions. Recent lattice QCD results suggest that the presence of a magnetic field has a significant impact on the ratios of thermodynamic susceptibilities. Therefore, correlations between net-conserved charges could be used to study the magnetic field produced in peripheral heavy-ion collisions.

We present the new results on the first-order correlations of net-proton, net-charge, and net-kaon, where net-proton and net net-koan act as a proxy of net-baryon and net-strangeness, respectively. The measurements are performed as a function of centrality in Pb--Pb collisions at $\sqrt{s_\mathrm{NN}} = 5.02$ TeV using the data recorded by the ALICE detector. The results are compared with corresponding results at lower collision energies from the STAR experiment at RHIC and with theoretical predictions from lattice QCD, the Hadron Resonance Gas model, and the HIJING event generator.

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

PPT_QM_v2_6.pdf

17:30 D and B meson Energy loss and Azimuthal Anisotropy in a Strongly Coupled Plasma in pA collisions at $\sqrt{s_{NN}}=200$ GeV

We present energy loss predictions of B and D-mesons at $\sqrt{s}=200$ GeV in pA collision systems. We assume that the medium produced in these collisions is strongly coupled, and show the centrality and momentum dependence of the nuclear modification factor at midrapidity. We also quantify the systematic theoretical uncertainties in these predictions that are a result of the mapping of parameters in $\mathcal{N}=4$ SYM theory to QCD, as well as the momentum dependence of the diffusion coefficient in AdS/CFT. We then present results of the corresponding $v_2(p_T)$ for B and D-mesons describing this azimuthal anisotropy for central, semi-central and peripheral collisions.

Speaker: Mr Blessed Arthur Ngwenya

17:30 Dense matter in a constituent quark model

In this work, we investigate the color-spin interaction of a quark, a diquark and a baryon with their surrounding baryons and/or quark matter. This is accomplished by classifying all possible flavor and spin states of the resulting multiquark configuration in both the flavor SU(2) and SU(3) symmetric cases. We also discuss the three-body confinement potential and show that this does not contribute to the outcome. Furthermore, we find that a quark becomes more stable than a baryon when the number of surrounding baryons is three or more. Finally, when we consider the internal color-spin factor of a probe, our results show that the effects of the color-spin interaction of a multiquark configuration is consistent with the so-called diquarkyonic configuration.

Speaker: Aaron Park

17:30 Determination of total charm production cross-section in pp collisions at 5.02 TeV with the HonexComb project

Studies of charm production in proton-proton ($pp$) collisions are essential to understand some of the most fundamental aspects of Quantum Chromodynamics. They also provide the baseline for interpretation of charm data from larger colliding systems. Over the last decade, the measurement of the production cross-sections of charm mesons and baryons in $pp$ collisions has been at the centre of a wide experimental effort at the Large Hadron Collider (LHC). These cross-sections were measured over a wide transverse momentum and rapidity coverage, thanks to the complementary kinematic acceptance of the different LHC experiments. In this study, the measurements of the charm hadrons $D^0$, $D^+$, $D_s^+$, $\Lambda_c^+$ and $\Xi_c^0$ performed by the ALICE, CMS and LHCb collaborations in $pp$ collisions at the centre-of-mass energy $\sqrt{s}=\rm 5.02$ TeV are combined in transverse momentum and rapidity, and, using the most recent theoretical calculations, are extrapolated to the full phase space to determine the total charm-quark production cross section $\sigma_{c\bar{c}}$. We will discuss the final result, which increases the existing tension between experimental data and fixed order calculations, together with comparisons to PYTHIA predictions.

Speaker: Jiayin Sun (Universita e INFN, Cagliari)

17:30 Development of unfolding techniques for dijet measurements in sPHENIX

The quark-gluon plasma (QGP) is a liquid created in high-energy heavy-ion collisions where quarks and gluons become deconfined. This state allows us to examine the emergent properties of quantum chromodynamics (QCD) under extreme conditions. sPHENIX, a new experiment at RHIC, studies the QGP created in Au-Au collisions and started taking data in 2023. Collimated sprays of particles, called jets, may be created in these collisions, typically in back-to-back (dijet) configurations. These dijets are produced prior to the formation of the QGP and interact with it during their development, losing energy ins a process called “jet quenching” which probes the nature of the QGP. When these dijets do not pass through the same path-length of QGP, the energy loss will be asymmetric. The dijet momentum imbalance (x$_J$) is defined as the ratio between the sub-leading (second highest energy) jet’s energy and the leading (highest energy) jet’s energy, and is a useful measure of energy loss. However, dijet measurements are sensitive to the underlying event and detector resolution. To correct for these effects we examine the development and application of Bayesian unfolding techniques on PYTHIA jets embedded into HIJING Au+Au background. Future uses will include implementation on measured dijet distributions in sPHENIX.

Speaker: Micah Meskowitz

QM Poster Dijet Unfolding.pdf

17:30 Dielectron Continuum in p+p Collisions

In this poster, PHENIX presents a proof of principle study for the measurement of prompt and non-prompt $e^{+}e^{-}$ pair production in the intermediate mass range ($m_{\phi}$ $<$ $m_{ee}$ $<$ $m_{J/\psi}$) using $p$+$p$ data at 200 GeV taken in 2015. PHENIX plans to extend the measurement to the high statistics Au+Au data-set recorded in 2014 and 2016, with the goal to isolate the expected prompt thermal contribution in the intermediate mass region from non-prompt pairs from heavy flavor decays. In $p$+$p$ collisions the main physics signal in this mass region originates from semileptonic decays of charm and bottom $q\bar{q}$ pairs. The $e^+$ and $e^-$ origin from decays many micron away from the interaction point. This non-prompt component is identified statistically by measuring the distance of closest approach (DCA) with the PHENIX silicon vertex detector (VTX). The VTX has four layers with a total radiation length of about 15\%, thus electrons from photon conversions cause a significant combinatorial background for the measurement, even in $p$+$p$ collisions. We have developed rejection techniques that effectively eliminate this background, improving the signal-to-background ratio by orders of magnitude. We will present the $e^{+}e^{-}$ pair spectra from $p$+$p$ collisions and its non-prompt contributions.

Speaker: Dr Roli Esha (Center for Frontiers in Nuclear Science, Stony Brook University)

qm2023_poster.pdf

17:30 Differential studies of multi-harmonic $v_n$ correlations in heavy-ion collisions with ALICE

Results from heavy-ion collisions confirmed the scenario in which the deconfined state of nuclear matter, dubbed the quark--gluon plasma (QGP), undergoes a collective expansion. Collective anisotropic flow, quantified with Fourier harmonics of azimuthal distribution of particles, $v_n$, is one of the most sensitive experimental probes to constrain QGP properties. Recently developed multi-harmonic flow observables, Symmetric Cumulants (SC) and Asymmetric Cumulants (AC) of $v_n$ amplitudes, provide new and independent information from their correlations and fluctuations, since they satisfy all fundamental properties of multivariate cumulants in a strict mathematical sense.

In this contribution, the first differential measurements of SC and AC observables in Pb--Pb collisions measured with ALICE as a function of kinematic variables are presented. The analysis is performed in parallel using the legacy code and the newly deployed O2 framework for Run 3 analyses in ALICE.

Speaker: Ante Bilandzic (Technische Universitaet Muenchen (DE))

Bilandzic_ALICE_QM23-v4.pdf

17:30 Dilepton anisotropic flow from hadronic transport

We present the first results for dielectron anisotropic flow computed directly from hadronic transport in different systems, and explore the different calculation methods. Because leptons are insensitive to the strong interaction, they are mostly undisturbed by the hadronic medium created after a heavy-ion collision, and therefore serve as direct probes for it. In particular, the HADES experiment at GSI measures flow of dielectrons using the reaction plane method, which can lead to large systematic uncertainties. At the low beam energies of GSI, the evolution is mainly off-equilibrium, and hadronic transport provides an appropriate description and gives access to the full phase space, as well as knowledge on the dilepton origin, being a useful tool in studying the mechanisms behind flow generation from this off-equilibrium hadron resonance gas.

Speaker: Renan Hirayama (FIAS)

Poster_HirayamaRenan.pdf

17:30 Dilepton measurements with HADES in $Ag+Ag$ and $p+p$ collisions at $1.58 \, GeV$ beam energy

In this contribution we present results on the dielectron production in $Ag+Ag$ collisions (0-40% centrality) and $p+p$ interactions at $1.58 \, AGeV$ beam energy measured with the High Acceptance DiElectron Spectrometer (HADES). The HADES RICH detector has been upgraded with a new photon detection camera which strongly enhances the electron efficiency and conversion pair rejection. With this upgrade, a signal-to-background ratio of about 1 is achieved in the dielectron spectrum around $500 \, MeV/c^2$, even in $Ag+Ag$ collisions. $5\,$billion $Ag+Ag$ collisions have been analyzed showing a signal up to the $\phi$ meson mass region. A clear excess of dileptons is seen above the contributions from initial state processes and late meson decays which serves as messenger of the dense medium created in heavy-ion collisions. This excess reveals the thermal properties and the lifetime of the medium but also gives insight into meson properties at high densities.

To disentangle the various contributions to the measured dielectron yield it is important to precisely understand the dielectron production in elementary reactions. Therefore, HADES has recently measured $0.5\,$billion $p+p$ collisions at the same energy, where preliminary results will be presented in addition. These serve as baseline for the understanding and interpretation of the $Ag+Ag$ data.

Speaker: Karina Scharmann (Justus-Liebig-Universitaet Gießen)

PosterQM23_KarinaScharmann.pdf

17:30 Directed and triangular flow of identified hadrons and light nuclei from fixed-target energies at RHIC-STAR

The anisotropic flow parameters $(v_{n})$ offer insights into collective hydrodynamic expansion and transport properties of the produced medium at higher collision energies, while they are sensitive to the compressibility of the nuclear matter and nuclear equation of state at lower collision energies. Among them directed flow ($v_1$) describes the collective sideward motion of produced particles in heavy-ion collisions. It is an important probe to study the in-medium dynamics as it is sensitive to the equation of state (EoS) of the produced medium. Minimum in the slope of directed flow ($dv_1/dy$) as a function of collision energy has been proposed as a signature of the first-order phase transition between hadronic matter and quark-gluon plasma. The triangular flow $(v_3)$ typically arises from the initial condition fluctuations and is expected to be uncorrelated to the reaction plane. However, recent measurements at lower collision energies show a correlation between $v_3$ and the first-order event plane angle ($\Psi_{1}$).
In this poster, we will report measurements of $v_1$ and $v_3$ for $\pi$, $K$, $p$, $d$, and $t$ in Au+Au collisions at $\sqrt{s_{NN}}$ = 3.2, 3.5, 3.9, 4.5, 6.2, 7.2, and 7.7 GeV in fixed-target mode from the second phase of beam energy scan (BES-II) program at RHIC-STAR. The rapidity, centrality, and collision energy dependence of $v_1$ and $v_3$ will be shown and their physics implications will be discussed.

Speaker: SHARANG RAV SHARMA (IISER Tirupati)

17:30 Directed Flow of $\Lambda$, $^{3}_{\Lambda}{\rm H}$, and $^{4}_{\Lambda}{\rm H}$ in Au+Au collisions at $\sqrt{s_{NN}}$ = 3.2, 3.5, and 3.9 GeV at RHIC

Studying hyper-nuclei production and their collectivity can shed light on their production mechanism as well as the hyperon-nucleon interactions under finite pressure. This is a unique opportunity for heavy-ion collisions at high baryon density region where hypernuclei production rate increases.

In this poster, we will present $v_{1}$ of the hyper-nuclei ($\Lambda$, $^{3}_{\Lambda}{\rm H}$, $^{4}_{\Lambda}{\rm H}$) from mid-central Au+Au collisions at $\sqrt{s_{NN}}$ = 3.2, 3.5, and 3.9 GeV, collected by the STAR experiment with the fixed-target mode during the second phase of the RHIC beam energy scan program. The rapidity dependence of the hyper-nuclei directed flow ($v_{1}$) is studied in mid-central collisions. The extracted $v_{1}$ slopes of the hyper-nuclei are positive and decrease gradually as the collision energy increases. The results will be compared with models using the framework of hadronic transport and a coalescence after-burner.

Speaker: Junyi Han (Central China Normal University)

QM2023_poster_JunyiHan_v3.pdf

17:30 Directed flow of charm and light flavor with initial vorticity in non-central Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV from a multiphase transport model

With the extreme temperatures and energy densities generated by ultra-relativistic heavy-ion collisions, a new state of matter with surprising fluid properties will be created. Non-central heavy-ion collisions can generate a large initial angular momentum, resulting a strong vortical of $\omega \approx (9 \pm 1)× 10^{-21} s^{−1}$ in the fluid, estimated from the global $\Lambda$ hyperon polarization measurements in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV. This vortical structure may change the azimuthal distribution of the particle produced in the fluid.

We study the directed flow ($v_{1}$) of charm hadrons and light flavor hadrons in relativistic heavy-ion collisions based on a multiphase transport model (AMPT) framework with an initial vortical pattern in the partonic interaction phase. We find that the $dv_{1}/dy$ as a function of rapidity for pion and kaon are reversed compared to the default AMPT setting and are comparable to the measured value at RHIC energy. And the $dv_{1}/dy$ slope of $D^0$ meson increased by more than 2 times with the vorticity and also compared to the $D^0$ $v_{1}$ measurements from RHIC.

Speaker: Xinyue Ju

17:30 Directed Flow of Protons and Anti-Protons in RHIC Beam Energy Scan II

Directed flow of particles is an important feature seen in heavy-ion collisions and is a sensitive probe to the equation of state (EoS) of the matter produced in the collisions. Model calculations have also predicted that directed flow could be sensitive to the softening of EoS associated with a first order phase transition. Directed flow of protons and anti-protons are also of interest as they offer sensitivity to both the contributions from the transported quarks and the component generated by medium interactions at the later stage. Measurements of proton and net proton directed flow from BES-I have shown that there is a non-monotonous dependence on collision energy.
In this poster, We will present measurements of the directed flow of protons and antiprotons from 19.6, 14.5, 11.5, 9.2, and 7.7 GeV Au+Au collisions, using high statistics BES-II data from STAR. We will also present a decomposition of proton directed flow into a medium interaction generated component and a component (v1excess) attributed to transported protons. The v1excess component is found to show a simple scaling between collision energies of 200 GeV to ~10 GeV, but to break the scaling at energies below that. The new results have significantly reduced uncertainties and also allow differential measurements in centrality and transverse momentum. Results will be compared to different model calculations and implications to the understanding of the QCD phase structure and EoS of the medium will be discussed.

Speaker: Emilie Duckworth (Kent State University)

QM2023_poster_final.pdf

17:30 Distortions in the sPHENIX TPC using Digital Current with Machine Learning

The Time Projection Chamber (TPC) to be used for tracking and particle identification in the sPHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) is expected to experience significant distortions from build-up of backflowing ions created by the combination of high collision rates and amplification from Gas Electron Multiplier (GEM). By integrating the digitized readout from the detector, one produces a 'digital current' which serves as a proxy for the ion backflow current. The digital current can then be used to reconstruct the ion space charge density to calculate the electric and magnetic field distortions in the chamber, but at significant computational cost. Machine learning methods provide a mechanism to reduce this computational cost while also reducing errors by training and validating with experimental data. We will present methods and results using machine learning techniques to predict and correct for space-charge induced distortions in the sPHENIX TPC.

Speaker: Dhanush Anil Hangal (Lawrence Livermore Nat. Laboratory (US))

TPCDistortion_ML_Poster_QM23_Aug31_RC.pdf

17:30 Drell-Yan process at sPHENIX: a golden probe to study Cold Nuclear Matter effects

The nuclear modification factor related to the Drell-Yan (DY) production cross-section is an excellent probe of the cold nuclear matter (CNM) properties. The acceptance of the sPHENIX detector allows detection of DY events in the dielectron channel for p$_\perp$ ≳ M, where p$_\perp$ is the dilepton transverse momentum and M its invariant mass. In this kinematic region, the DY cross-section is dominated by NLO gluon Compton scattering allowing access to the gluon density of the nucleus, xG(x). The DY events extraction requires a precise knowledge of the QCD background contributing to the dilepton invariant mass spectrum. A fit to the latter one is carried out including opencharm (OC), open-bottom (OB), charmonium ($\psi$) and bottomonium ($\Upsilon$) simulations. The CNM effects are investigated via the rapidity and p$_\perp$ distributions of the DY lepton pair, and the possible impact of sPHENIX DY data on the xG(x) extraction is discussed. In addition, energy loss and broadening calculations based on Landau-Pomeranchuk-Migdal (LPM) model are shown.

Speaker: Mr Charles-Joseph Naïm (Université Paris-Saclay (FR))

17:30 Dynamics of QCD chiral transition with real-time functional renormalization group

In the chiral limit the complicated many-body dynamics around the second-order chiral phase transition of two-flavour QCD can be understood by appealing to universality. We present a novel formulation of real-time functional renormalization group that describes the stochastic hydrodynamic equations of motion for systems in the same dynamic universality class, which correspond to Model G in the Halperin-Hohenberg classification, and preserves all the relevant symmetries of such systems with reversible mode couplings. We show that the calculations indeed produce the non-trivial value z=d/2 for the dynamic critical exponent, where d is the number of spatial dimensions. We also extract the critical momentum dependence of the charge diffusion coefficient. We keep the degrees of freedom of the order parameters general and show that for N=3 we recover standard Model G dynamics and for N=2 we recover Model E dynamics.

Speaker: Prof. Soeren Schlichting (Universität Bielefeld)

17:30 Effect of hydrodynamic fluctuations on mixed harmonic cumulants at the LHC

We analyze the effect of hydrodynamic fluctuations on normalized mixed harmonic cumulants ($nMHC$) [1,2] for the first time based on event-by-event simulations of high-energy heavy-ion collisions using an integrated model of an initial state model, stochastic causal fluctuating hydrodynamics, and a hadronic afterburner.

For the quantitative constraints on the transport properties of quark-gluon plasma (QGP) and the initial-state models, it is important to compare various flow correlations from dynamical models to data. Recently, $nMHC$ was shown to be useful in constraining theoretical models [3]. Meanwhile, we have shown that hydrodynamic fluctuations affect the longitudinal factorization ratio $r_n(\eta_a,\eta_b)$ [4] and can reproduce the experimental centrality dependence with initial longitudinal fluctuations [5]. However, it is non-trivial how the hydrodynamic fluctuations affect the constraints on the QGP properties through various flows and correlations.

In this talk, we investigate the effect of hydrodynamic fluctuations on $nMHC$ in $\sqrt{s_\mathrm{NN}}$=2.76 TeV Pb+Pb collisions. We combine the $\mathtt{TRENTo}$ initial conditions and the $\mathtt{UrQMD}$ afterburner used in Refs. [3,6] with relativistic fluctuating hydrodynamics $\mathtt{rfh}$ [6]. We first compare the results with and without hydrodynamic fluctuations and see the effect. We next consider different temperature dependencies of viscosity. We find that the hydrodynamic fluctuations tend to decrease $nMHC$, which is because they de-correlate initial correlations. In particular, $nMHC(v_2^2,v_3^2)$ is sensitive to the hydrodynamic fluctuations but almost insensitive to the viscosity. We also discuss the effect of the rapidity gap. We argue that $nMHC$ is useful for identifying the effect of hydrodynamic fluctuations and is a key to properly constraining the theoretical models.

[1] Zuzana Moravcova, Kristjan Gulbrandsen, You Zhou, Phys. Rev. C 103, 024913 (2021).
[2] S. Acharya et al. (ALICE), Phys. Lett. B 818, 136354 (2021).
[3] M. Li, Y. Zhou, W. Zhao, B. Fu, Y. Mou, and H. Song, Phys. Rev. C 104, 024903 (2021).
[4] Azumi Sakai, Koichi Murase, Tetsufumi Hirano, Phys. Rev. C 102, 064903 (2020).
[5] Azumi Sakai, Koichi Murase, Tetsufumi Hirano, Phys. Lett. B 829, 137053 (2022).
[6] Kazuhisa Okamoto and Chiho Nonaka, Phys. Rev. C 98, no.5, 054906 (2018).
[7] Koichi Murase, Ph. D. thesis (University of Tokyo), (2015).

Speaker: Koichi Murase (Yukawa Institute for Theoretical Physics, Kyoto University)

QM2023-nMHC-and-hydro-fluctuations.pdf

17:30 Effect of Nuclear Shape Parameters On Initial State Observables In Heavy Ion Collisions

In heavy ion collisions, the initial state geometry plays a crucial role in determining final state observables such as elliptic flow $v_2$ and radial flow reflected by event-wise average transverse momentum $[p_{\rm T}]$. The initial state geometry is influenced by several nuclear shape parameters, including quadrupole deformation (β), triaxiality (γ) [1], nuclear radius (r), and skin depth (a) [2]. It is known from low-energy physics that many atomic nuclei exhibit a quadrupole shape that fluctuates around an average profile. This talk investigates the impact of nuclear shape fluctuations on initial state geometry in heavy ion collisions, focusing on eccentricity ($\epsilon_2$) and inverse transverse size ($d_⊥$), which are linearly related to fluctuations of flow, i.e. $v_2 \propto \epsilon_2$ and $\delta [p_T]\propto \delta d_{\perp}$, and comparing them across different system sizes. Our aim is to quantify the effects of these parameters on initial state observables in a coherent manner. We show that overall quadrupole deformation fluctuations enhance the cumulants of $\epsilon_2$ and $d_⊥$, while triaxiality fluctuations reduce the differences between prolate and oblate nuclei. Our results suggest that, in the large fluctuation limit, the initial state observables' values approach those obtained in collisions of rigid triaxial nuclei.

[1] Impact of nuclear shape fluctuations in high-energy heavy ion collisions
[2] Scaling approach to nuclear structure in high-energy heavy-ion collisions

Speaker: Aman Dimri (Stony Brook University (US))

Aman_Poster_8_Final.pdf

17:30 Effects of hadronic reinteraction on jet fragmentation from small to large systems

The effect of the hadronic phase on jet quenching in nuclear collisions is largely an open question, although there are tantalizing hints from previous studies that the effects might be sizable. We have implemented a hadronic afterburner phase for jet fragmentation hadrons in the JETSCAPE framework using SMASH. We have applied the new setup to $e^++e^-$, $p+p$ and $A+A$ systems in order to study the effects of hadronic rescattering. For a quantitative analysis we compare simulations, with and without rescatterings of shower hadrons during the afterburner phase. We report here effects on hadron spectra and jet observables as a function of collision system, collision energy and multiplicity.

Speaker: Mr Hendrik Roch (FIAS)

Poster_QM23_Hendrik_Roch.pdf

17:30 Elliptic flow measurement of $J/\psi$ in PHENIX Run14 Au+Au at $\sqrt{s_{NN}}=200$ GeV

The Quark Gluon Plasma (QGP) produced in relativistic heavy ion collisions exhibits a nearly perfect fluid behavior. This behavior is observed as strong azimuthal correlations between the produced particles. Measurement of $J/\psi$ azimuthal correlations can provide key information about the charm quark dynamics in the QGP. Strong elliptic flow of $J/\psi$ has been observed in Pb+Pb collisions at the LHC and attributed to $J/\psi$ production through coalescence of charm quarks that flow with the medium. At RHIC, the $J/\psi$ flow measurements at mid-rapidity are presently inconclusive, while measurements of the nuclear modification factors at mid- and forward rapidity hint that coalescence may play a role in central collisions. The PHENIX experiment at RHIC has a unique coverage at forward rapidity $(1.2\leq|\eta|\leq2.2)$ and a large sample of $J/\psi\rightarrow\mu^++\mu^-$ decays collected in 2014 in Au+Au collisions at 200 GeV. We will present a statistically improved measurement of $J/\psi$ elliptic flow at RHIC at forward rapidity.

Speaker: Luis Bichon III

QM_Poster_Bichon.pdf

17:30 Elliptic flow splittings in the Polyakov–Nambu–Jona-Lasinio transport model

To incorporate the effect of gluons on the evolution dynamics of the quark matter produced in relativistic heavy-ion collisions, we extend the three-flavor Nambu–Jona-Lasinio (NJL) transport model to include the contribution from the Polyakov loops. Imbedding the resulting pNJL partonic transport model in an extended multiphase transport (extended AMPT) model, we then study the elliptic flow splittings between particles and their antiparticles in relativistic heavy-ion collisions at beam energy scan energies. We find that a weak quark vector interaction in the partonic phase is able to describe the elliptic flow splitting between protons and antiprotons in heavy-ion collisions at √sNN = 7.7 to 39 GeV. Knowledge of the quark vector interaction is useful for understanding the equation of state of quark matter at large baryon chemical potentials and thus the location of the critical point in the QCD phase diagram.

Speaker: Wen-Hao Zhou (复旦大学)

17:30 Empirical Characteristics of Light and Heavy Flavor Parton Energy Loss Dynamics at the LHC and RHIC

Nuclear modification factors ($R_{AA}$) of leading particles provide valuable information about the flavor dependent magnitude and characteristics of parton energy loss in $A+A$ collisions. Experimental measurements of $R_{AA}$ exhibit a distinct different dependence on transverse momentum ($p_{T}$) at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). Previous analyses of RHIC data treated the difference in the $p_{T}$ spectrum between $p+p$ and $A+A$ collisions as a leading parton $p_{T}$ loss and empirically concluded that the flat $p_{T}$ dependence of $R_{AA}$ corresponds to a constant fractional $p_{T}$ loss ($\Delta p_{T}/p_{T}$) [1]. This feature of $\Delta p_{T}$ proportional to $p_{T}$ can be understood via elastic collisions in classical dynamics. We analyze LHC measurements of the strong $p_{T}$ dependence of $R_{AA}$ for light and heavy flavor leading particles. Our analyses indicate that LHC data for a variety of leading particle species are consistent with $\Delta p_{T}$ proportional to $\sqrt{p_{T}}$, in contrast to proportional to $p_{T}$ at RHIC. In addition, Charm hadrons exhibit differing behavior compared to the other species studied, revealing possible unique heavy flavor dynamics. These distinct features are consistent with the scenario of increased contributions from radiative energy loss at LHC energies compared with stronger collisional energy loss dominance at RHIC energies. Moreover, linear trends between fractional energy loss and initial parton density at varying $p_{T}$ magnitudes indicate that the amount of parton energy loss does not depend strongly on the traversing geometrical path length of the parton during collision evolutions, which is in agreement with previous empirical findings at RHIC despite significant different initial parton densities formed at LHC and RHIC. We will also discuss further implications of the observed proportionality in LHC data and differences in fractional energy loss at varying $p_{T}$ scales.
[1] Wang, G. and Huang, H. Phys. Lett. B 672, 30 (2009).

Speaker: THOMAS MARSHALL

EnergyLossPosterQM23.pdf

EnergyLossPosterQM23.pptx

17:30 Energy dependence of J/$\psi$ production in Au+Au collisions at $\sqrt{\mathrm{s_{NN}}}$ = 14.6, 19.6 and 27 GeV at STAR

Measurements of heavy quarkonia in heavy-ion collisions play a crucial role in studying the properties of the quark-gluon plasma (QGP). The dissociation of J/$\psi$, caused by the color screening effect, was proposed as a direct signature of the QGP formation. However, recombination of deconfined charm-anticharm (c$\bar{c}$) pairs complicates the interpretation of the observed J/$\psi$ suppression in heavy-ion collisions, and its contribution is expected to be smaller at lower collision energies. Therefore, measuring the beam energy dependence of J/$\psi$ production will help disentangle different effects.
In this poster, we report the measurements of inclusive J/$\psi$ production in Au+Au collisions at $\sqrt{\mathrm{s_{NN}}}$ = 14.6, 19.6 and 27 GeV using the Beam Energy Scan Phase II (BES-II) data recorded by the STAR experiment. The J/$\psi$ invariant yields and nuclear modification factors ($R_{AA}$) are presented as a function of centrality and transverse momentum. Beam energy dependence of J/$\psi$ $R_{AA}$ is discussed together with model comparisons.

Speaker: Wei Zhang

17:30 Energy flow in jets in pp and Pb--Pb collisions with ALICE

Jets are excellent probes for studying the deconfined matter formed in heavy ion collisions. However, competing energy-loss effects, such as the dependence on the opening angle of the shower, radiative emissions to large angles, and the medium response to the jet, can obscure interpretation. This talk presents two new observables aimed at disentangling these effects. First, we introduce a new infrared and collinear safe measurement of the jet energy flow within jets reconstructed with different resolution parameters $R$. Changing the jet $R$ varies the relative contribution of competing energy-loss effects. Additionally, we utilize the excellent ALICE PID capabilities in new measurements of jet-hadron correlations with identified hadrons and identified hadron ratios in jets in pp and Pb-Pb collisions at $\sqrt{s_{\rm{NN}}} = 5.02~\mathrm{TeV}$. The final state jet hadrochemical composition can differ from the vacuum due to medium-induced modifications to jet fragmentation or the medium response. Finally, the ALICE PID capabilities can also be exploited to study gluon jet fragmentation with the new LHC data in pp collisions at $\sqrt{s} = 13.6~\mathrm{TeV}$.

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

Jet_Energy_Flow_QM23_poster_v3.pdf

17:30 Energy loss and chiral magnetic effect

Chiral media, such as quark-gluon plasma, possess a number of unique properties originating from the quantum phenomenon of the chiral anomaly. These properties can be measured by observing the propagation of fast charged particles moving through the medium and the radiation produced in the process. We show how the chiral anomaly confers distinctive features onto the particle energy loss and its radiation spectrum. We argue then that this makes quantum tomography a powerful and versatile tool to investigate the properties of chiral systems ranging from the Weyl semimetals to the quark-gluon plasma to the axion stars.

Based on Hansen and Tuchin, Phys. Rev. C 104, no.3, 034903 (2021) and Phys. Rev. D 105, no.11, 116008 (2022).

Speaker: Jeremy Hansen (Iowa State University)

qm_poster.pdf

17:30 Energy-energy correlator measurements for D$^{0}$-tagged jets in pp collisions at 13 TeV with ALICE.

Energy-energy correlators (EEC) offer a novel way to study the structure of jets. Defined as the energy-weighted cross section of particle pairs inside jets, the correlation strength as a function of the pair opening angle allows a distinct separation of the perturbative and non-perturbative regimes. The evolution of parton dynamics in jets to their confinement into hadrons can be studied. Measurements of jets initiated by heavy quarks play an important role in the testing of pQCD calculations and represent a critical component of the studies of quark-gluon plasma (QGP) created in heavy-ion collisions. We present the first measurements of the EECs for D$^0$-tagged jets in pp collisions at 13 TeV with the ALICE experiment at the LHC. By comparing our results with EEC’s in inclusive (gluon-dominated) jets, we can search for modifications in the radiation pattern of jets due to mass effects such as the dead cone. We also compare with perturbative QCD predictions to measure the onset of non-perturbative physics. These measurements will also serve as a baseline for future studies in heavy-ion collisions, allowing for disentanglement of the dynamics of the dead cone from interactions with the quark-gluon plasma.

Speaker: Beatrice Liang-Gilman (University of California Berkeley (US))

Beatrice_Liang-Gilman_EEC_D0_Poster_QM_v3.pdf

17:30 Energy-energy correlator measurements in pp and pPb collisions at 5.02 TeV with ALICE

Energy-energy correlators (EEC) have been proposed to study the structure of energy flow within jets. These functions are defined as the energy-weighted cross-section of particle pairs inside jets. The correlation as a function of pair distance and jet transverse momentum offers a clear separation between the perturbative and non-perturbative regimes, where one can probe the dynamics of quarks and gluons and their confinement into hadrons. In this work, using data from the ALICE experiment, we present measurements of 2-point EECs in p-Pb collisions at 5.02 TeV. By comparing these results to a p-p baseline, we can study the changes to jet dynamics caused by interactions between color charges and a cold nuclear medium. In particular, we can look into how the presence of cold nuclear matter modifies the hadronization mechanism.

Speaker: Anjali Nambrath (University of California Berkeley (US))

p-Pb_EEC_Poster_QM.pdf

17:30 Entanglement entropy measurements from p-p collisions at LHC energies

In an effort to better understand the thermal-like behavior and particle yields seen in p-p collisions we recast the problem employing the principles of quantum states and their entanglement in the produced system. We seek to show that this entanglement in the initial state has a measurable effect on the evolution of the system and is the driving mechanism behind the thermal-like behavior and particle yields observed. Recent studies have demonstrated that entanglement in the initial state could endure the evolution of a strongly coupled system. Consequently, we attempt to show equivalence in a calculation of the initial state entropy (calculated using PDF’s) and the final state entropy (calculated using multiplicity distributions). Multiplicity distributions used in this study are that of primary charged particles, measured using the ALICE detector at the LHC.

Speaker: Alek Hutson (University of Houston (US))

QM_Poster_AHutson2.pdf

17:30 Entropy and Multifractality in Hadron-Hadron Collisions at SPS and LHC Energies

Multiplicity data on $\rm\bar{p}$p/pp collisions at {\footnotesize SPS} and {\footnotesize LHC} energies (0.2-7 TeV) are used to study the entropy production, dimensions and other multifractal characteristics of multiplicity distributions of relativistic charged particles produced. It is observed that the entropy produced in smaller and(or) larger phase space bins, when normalized to maximum rapidity, exhibits a kind of scaling which is nicely supported by Monte Calro model, {\footnotesize PYTHIA-8} with color-reconnection({\footnotesize CR}) switched-$`$on'. Using the Renyi's order-q information entropy, multifractal characterisitcs of multiplicity distributions are studied in terms of generalized dimensions, $\rm D_q$. Nearly the same value of multifractal specific heat, $`$c' $\sim 0.1$, are observed which agrees fairly well with those reported earlier for hadron-hadron (hh) collsions at lower energies. These findings, therefore, suggest that the parameter $`$c' may be taken as the universal characterisitc of multiparticle production in hh collisions. {\footnotesize PYTHIA} model, however, predicts somewhat lower values of $`$c' as compared to those obtained with the data. The analysis is further extended to examine the spectrum of scaling indices, which might lead to make some useful conclusions on the energy dependence of degree of multifractality and smoothness of the rapidity distributions.

Speaker: Ms Bushra Ali (Aligarh Muslim University (IN))

17:30 Evaluation of a baseline for the study of azimuthal correlations of charmed mesons in heavy-ion collisions at RHIC using PYTHIA and Herwig++

Measurements of azimuthal correlations of charmed mesons in high-energy heavy-ion collisions can shed light on the transport properties of the Qaurk-Gluon Plasma. The STAR experiment at the Relativistic Heavy Ion Collider (RHIC) collected in 2014 and 2016 a large sample of Au+Au reactions at $\sqrt{s_{NN}}$ = 200 GeV making such a study possible. The sPHENIX experiment will also offer a similar opportunity in the next few years. However, such a measurement in $p$+$p$ collisions at the same energy has not been feasible so far.

To provide a baseline for the heavy-ion measurements, we report studies of the azimuthal correlations between charmed mesons in $p$+$p$ reactions using two Monte Carlo event generators, PYTHIA 8 and Herwig++. We validate the models against the available data from the STAR and CDF experiments, and compare their predictions to deliver a reliable $p$+$p$ baseline for heavy-ion collision studies. Finally, we discuss prospects for performing such measurements in $p$+$p$ collisions at RHIC.

Speaker: Katarzyna Gwizdziel (Warsaw University of Technology (PL))

QM2023_poster_Gwizdziel_baseline_angCorr.pdf

17:30 Event-by-event comparison of initial state models with momentum space information in a hybrid approach

The initial state of heavy-ion collisions has a short lifetime and cannot be directly measured. As a result, various initial condition models exist. Although averaged event observables with different initial condition models give comparable results, event by event analysis can help to identify systematic differences. To determine the initial conditions is crucial to assess systematic uncertainties of Bayesian analysis, that aim at the extraction of transport coefficients from experimental data. The qualitative impact of the choice of initial conditions in hydrodynamical simulations is studied on an event-by-event basis in the hybrid approach SMASH-vHLLE-Hybrid\textsuperscript{1}, composed of the hadronic transport approach SMASH\textsuperscript{2} and the (3+1)d viscous hydrodynamic code vHLLE\textsuperscript{3,4}. Event-by-event correlations are studied for SMASH IC as well as for IP-Glasma and TRENTO, with and without early time out-of-equilibrium dynamics, for Au-Au collisions at $\sqrt{s_{NN}}=200$ GeV in different centrality classes.
We observe that the initial state eccentricities $\epsilon_2$ and $\epsilon_3$ are, depending on the setup and the model, not independent and show correlations which also result due to the assumed linear response of flow to eccentricity\textsuperscript{5} in correlations between the elliptic and triangular flow. Additionally, we also study initial momentum space information present in the SMASH and IP-Glasma initial condition models. We find that for very spherical events, the initial state momentum anisotropy significantly contributes to the final state momentum anisotropy, which means that the description of such events is especially sensitive to the choice of the initial state model.

References:
[1] https://github.com/smash-transport/smash-vhlle-hybrid
[2] https://github.com/smash-transport/smash
[3] https://github.com/yukarpenko/vhlle
[4] I. Karpenko, P. Huovinen, M. Bleicher, Comput. Phys. Commun. 185 (2014).
[5] J. Noronha-Hostler et al., Phys. Rev. C 93.1 (2016).

Speaker: Niklas Götz

Poster_QM.pdf

17:30 Event-by-event local multiplicity fluctuations in charged particle production at the LHC energies with ALICE

A hot and dense system formed in heavy-ion collisions can be characterized by studying the scaling behavior of the spatial distributions of the produced particles. In this contribution, we present intermittency analysis of the normalized factorial moments ($F\rm{_{q}}$) of the multiplicity distributions of the charged particles produced in Pb--Pb collisions as a function of phase-space resolution. The spatial configurations of the charged particles in two-dimensional ($\eta,\varphi$) phase space are investigated. For a system with scale-invariant dynamical fluctuations due to the characteristic critical behavior near the phase transition, the $F\rm{_{q}}$ exhibits power-law growth with increasing phase-space resolution, which is a signature of self-similar fluctuations and the fractal structure of the system. The dependence of the fractal dimension $D_{q}$ on the order parameter $q$ is indicative of the multifractal nature of the system. By relating the $q^{\rm{th}}$-order $F\rm{_{q}}$ to the normalized second-order factorial moment ($F\rm{_{2}}$), we extract the scaling exponent ($\nu$), which provides information about the order of the phase transition in the framework of the Ginzburg-Landau theory. The first results of the intermittency analysis show the presence of scale-invariant fluctuations, the multifractal nature of the system, and that $\nu$ is independent of $p\rm{_{T}}$ in the soft $p\rm{_{T}}$ region. The measurements are also compared with the corresponding results from the AMPT and HIJING models.

Speaker: Ramni Gupta (University of Jammu (IN))

ALICE_Intermittency@JU_Poster.pdf

17:30 Event-shape engineering of charged hadron spectra in heavy-ion collisions at $\sqrt{s_{\mathrm{NN}}}=200$ GeV at STAR

Partonic scatterings with high momentum transfer occur before the formation of the quark-gluon plasma (QGP) in heavy-ion collisions and result in collimated collections of hadrons, called jets. The modification of the high-virtuality parton shower in the QGP compared to that in proton-proton collisions offers insight into the nature of the medium's interactions with colored probes. To study the path-length dependence of hard partons traveling through the QGP, we apply a technique known as event-shape engineering to data from heavy-ion collisions at $\sqrt{s_{\mathrm{NN}}}=200\ \mathrm{GeV}$ at STAR. Within a given eccentricity and centrality class, charged hadrons traveling in the event plane direction (having shorter path length) are compared to those traveling perpendicular to it (having longer path length). By fixing the centrality, we can control for the energy density. We then report a comparison of the ratios of in-and out-of-plane charged hadron spectra between two eccentricity classes, which accesses the dependence of energy loss on the collision geometry.

Speaker: Isaac Mooney

QM23Poster_Mooney.pdf

17:30 Exploring hadronic resonances through EPOS4 model: A study of particle interactions and spectra

Hadronic resonances are interesting candidates to study the properties of the hadronic phase, which is the time span between the chemical and kinetic freeze-outs, formed during the evolution of relativistic heavy-ion collisions. Due to their short lifetimes, comparable to the lifetime of hadronic phase ($\sim$10 $-$ 12 fm/$c$), they decay in the hadronic phase and their decay products undergo rescattering or regeneration within the hadronic gas. Thus, the yields of the hadronic resonances alter than what was originally produced before the chemical freeze-out. This change in their yield, which is extensively studied to understand the properties of the hadronic phase, depends upon the lifeime of the decaying resonance, the interaction cross-sections of its decay daughters, and the lifetime of the hadronic phase. \
In this study, we explore the production yields of hadronic resonances by simulating pp, p$-$Pb and Pb$-$Pb collisions at various centre of mass energies using the latest EPOS4 model. The EPOS4 model employs a comprehensive scheme for simulating high-energy particle collisions, which includes primary interactions based on S-Matrix theory, secondary interactions using a core-corona separation approach, hydrodynamic evolution, micro-canonical hadronization, and a final hadronic afterburner using UrQMD. This scheme allows for the simulation of parallel scatterings and accurately models the complex dynamics of high-energy particle collisions, thus providing some new understanding of a deep connection between four basic concepts in pp and AA collisions: parallel scattering, energy conservation, factorization, and saturation. We measure the transverse momentum spectra ( $p_{\rm{T}}$ ), energy dependence of resonance production, ratio of yield of resonance particles to their corresponding stable particles, nuclear modification factor ( $R_{\rm{pA}}$ and $R_{\rm{AA}}$) for various hadronic resonances of different lifetimes and compare the results with the data available from the ALICE experiment at CERN.

Speaker: Vikash Sumberia (University of Jammu (IN))

17:30 Exploring heat conductivity at RHIC Beam Energy Scan

Exploring the transport coefficients of the QGP is one of the main goals in relativistic heavy ion collisions. By employing the Bayesian analysis method, the temperature dependent shear and bulk viscosity of QGP medium has been extracted. However, the heat conductivity of the QGP has not been fully explored. Using single-shoot MUSIC hydrodynamics with smooth initial condition, ref.[1] found that turning on the heat conductivity of the QGP tends to transport net baryon number towards mid-rapidity.

In this talk [2], we study the heat conductivity using event-by-event hydrodynamic simulations (iEBE-MUSIC) with the dynamical initial conditions. We will show that some of the three-particle flow correlations are sensitive to the heat conductivity of QGP, which can be used to constrain the heat conductivity at RHIC Beam Energy Scan.

[1]Gabriel S. Denicol, Charles Gale, Sangyong Jeon, Akihiko Monnai, Björn Schenke, and Chun Shen, Phys. Rev. C 98, 034916 (2018).

[2]Shujun Zhao, Chun Shen, Huichao Song, paper in preparation.

Speaker: Shujun Zhao

17:30 Exploring light hadrons in UPCs with ALICE

The investigation of light hadrons in UPCs is of great interest for QCD studies. ALICE is a superb detector for studying these processes because of its excellent particle identification and tracking capabilities. The measured cross section of coherent $\rho^{0}$ mesons in photon-lead interactions has been found to be about 40% smaller than what is predicted by the Glauber model, and expectations from photon-proton interactions, indicating the importance of high-mass intermediate states in the process of $\rho^{0}$ scattering off nuclei. In this talk, we will review the status of the coherent $\rho^{0}$ meson analysis, and present the first study of the photoproduction of the two-kaon final state channel in UPCs, which could originate from the decay of the $\phi$ meson or from direct production. ALICE can also study four-prong states which are interesting for spectroscopy and excited resonance searches. In this talk, we will discuss new results on exclusive four-pion states.

Speaker: Alexander Bylinkin (ITEP)

17:30 Exploring neutron stars with three conserved charges in a newly optimized C++ Chiral Mean Field code

The Chiral Mean Field model (CMF) has been successful in describing the equation of state at large baryon densities, such as those found in neutron stars, neutron star mergers, and heavy-ion collisions. The MUSES collaboration has rewritten the zero-temperature CMF model from Fortran 77 into a parallelized modern C++20 using OpenMP, which has resulted in at least an order of magnitude improvement in runtime. We obtained equations of state across $\mu_B$, $\mu_S$, and $\mu_Q$, and within the metastable regime around the quark deconfinement phase transition. The improved numerical resolution allows for the accurate computation of higher-order derivatives such as susceptibilities. Finally, we computed neutron star observables like quadrupole moment, Love number, moment of inertia, and mass-radius curve.

Speaker: Mr Nikolás Cruz Camacho (University of Illinois at Urbana-Champaign)

QM_2023_Nikolas_Cruz.pdf

17:30 Exploring the equilibration time of the QGP with jet quenching

Heavy-ion collisions produce a quark-gluon plasma that undergoes rapid expansion and cooling, which presents a challenge for calculating jet quenching observables. Current approaches rely on analytical results for static cases, introducing theoretical uncertainties and biases in our understanding of the pre-equilibrated medium. To address this issue, we employ analytical re-summation schemes to incorporate multiple scattering in a class of expanding backgrounds. By introducing a new length scale related to the equilibration time of the QGP, we investigate the range of validity of Bethe-Heitler emissions, LPM interference effects, and higher-twist contributions to the emitted gluon spectrum. We also discuss methods to mitigate the non-local nature of the emission spectrum. Our analysis shows that strong jet quenching is only possible when the equilibration time of the medium is longer than its mean free path, highlighting the importance of medium modifications of jets in the earliest stages of heavy-ion collisions. By accounting for the expansion of the medium, our approach reduces the uncertainties in model predictions for jet quenching observables, providing insights into the nature of the pre-equilibrated medium. This work lays the foundation for further investigations into the dynamics of the QGP and the interplay between jets and the expanding medium.

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

17:30 Exploring the Feasibility of Imaging Atomic Nuclei at the Electron-Ion Collider with the ePIC Experiment

Studying atomic nuclei's deformation and substructure, including quadruple, triaxial, and octupole shapes, is crucial to understanding nuclear structure comprehensively. The cluster structures depend on variables such as excitation energy, core clusters, and excess neutrons. Although clusters are tightly bound in low-lying states, the correlation between clusters and their formation is not fully understood. Our ongoing feasibility studies, utilizing different energy and number correlations and momentum correlation function measures, show promising results. We used the proposed EPIC detector at the Electron-Ion Collider and the BeAGLE model to simulate collisions between e+Be, e+C, e+O, e+Pb, and e+U, which will be presented and discussed. Our findings indicate that using the EIC's mid- and forward-rapidity ePIC detectors could provide new insights into alpha clustering and nuclear deformation in atomic nuclei.

Speaker: Roy Lacey

QM2023_Clust_Poster_b.pdf

17:30 Exploring the origin of $[p_\mathrm{T}]$ fluctuations in ultra-central heavy ion collisions: Higher order $[p_\mathrm{T}]$ correlations in ATLAS

The thermal fluctuations in the QGP medium formed in heavy ion collisions present themselves as event-wise $[p_\mathrm{T}]$ fluctuations in the final state. Recent studies have shown that the average and higher-order fluctuations of $[p_\mathrm{T}]$ in ultra-central collisions are sensitive to radial flow, random thermal motion, and nuclear deformation, and can provide constraints on the extent of thermalization of the QGP droplet. This talk presents new precise measurements of $[p_\mathrm{T}]$ cumulants up to 3rd order in $^{129}$Xe+$^{129}$Xe and $^{208}$Pb+$^{208}$Pb collisions. The multiplicity dependence of $[p_\mathrm{T}]$ cumulants show deviations from expected power-law behavior. The average $\left\langle[p_\mathrm{T}]\right\rangle$ shows a non-trivial rise in the ultra-central collisions, whereas the variance shows a clear and sharp drop in ultra-central collisions. The skewness, expected to be more sensitive towards higher $p_\mathrm{T}$ particles, also shows a non-trivial increase in ultra-central collisions. All observables also show a clear dependence on the $p_\mathrm{T}$ ranges in consideration and the centrality estimator used in the analysis. These results have strong implications for understanding the impacts of the initial condition, medium thermalization, and medium properties on final state $[p_\mathrm{T}]$ fluctuations.

Speaker: Somadutta Bhatta (Stony Brook University (US))

QM2023_Poster_ATLAS_Somadutta.pdf

17:30 Exploring the strangeness enhancement and collective-like effects in small collision systems with ALICE at LHC

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, such as near-side long-range correlations, mass-dependent hardening of ${p}_{\mathrm T}$ spectra, strangeness enhancement etc. Therefore, one of the key challenges today is understanding the origin of strangeness enhancement in small collision systems at very high energies, i.e. the increase of (multi-)strange hadron yields relative to non-strange hadron yields with increasing charged-particle multiplicity ($\mathrm{d} N_{\mathrm{ch}}/\mathrm{d}\eta_{~\left | \eta \right |~<~0.5} ~<$ 100) and saturation for high multiplicities.

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. The ratio of baryon to meson yields and the nuclear modification factor will also be included. These observables are used to study the hadronization process in small collision systems. 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 including the latest version EPOS4 and Pythia8 will be discussed.

Speaker: Anju Bhasin (University of Jammu (IN))

QM_23_MSharma_v3.pdf

17:30 Exploring thermoelectric Figure of Merit in QCD medium with conserved charges

Exploring thermoelectric Figure of Merit in QCD medium with conserved charges

It is the goal of the RHIC BES program and the future FAIR, NICA facilities to produce baryon-rich matter. In these low-energy HIC experiments, diffusion processes of conserved charges play a vital role in dynamic evolution of dense QCD matter. Recently, thermoelectric effects such as Seebeck effect, which have been extensively studied in condensed matter materials, have also captured the attention of high-density HIC physics. Thermoelectric Figure of Merit (ZT), which reflect strong couplings among electrical conductivity, thermal conductivity, Seebeck coefficient and temperature, can be used as a common benchmark to quantify the effeciency of meterial at heat-to-electricity conversion.

We focus on the ZT in hadronic phase, where the themoelectric transports of mutiple conserved charges (the baryon number, strangeness and electric charge) are fully considered. The different transport coefficients matrices are estimated using the Boltzmann kinetic theory in Hardron Resonance Gas model with and without repulsive mean field effect. We also study the effect of magnetic field on ZT. Different to zero magnetic field, additional transverse ZT can appear at finite magnetic field, and we for the first time distinguish the calculation results of themoelectric coefficients in QCD medium under the adiabatic and isothermal condition. Finally, we establish the relations between ZT and $\sqrt{s_{NN}}$ to better exhibit the thermoelectric properties of QCD medium at different collision energies.

Speaker: He-Xia Zhang

17:30 Exploring transverse momentum broadening in expanding medium-induced cascades

We investigate the characteristics of gluonic cascades in static and expanding media by numerically solving the complete BDIM (Blaizot-Dominguez-Iancu-Mehtar-Tani) evolution equations in longitudinal and transverse momentum using the Monte Carlo event generator MINCAS. In this analysis, we compare angular distributions of in-cone radiation across various medium profiles with effective scaling laws. Our findings indicate that the out-of-cone loss of energy occurs through the radiative break-up of hard fragments, which is followed by an angular broadening of soft fragments. Although the broadening of the leading fragments is substantially impacted by the dilution of the medium caused by expansion, we find that in the low-x range, which is accountable for the majority of gluon multiplicity in the cascade, the angular distributions are almost identical when comparing different medium profiles. This similarity is primarily because multiple splittings play a dominant role in broadening within this range. Lastly, we examine how our findings influence the phenomenological explanation of jet quenching and out-of-cone radiation.

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

QM23_poster_souvik.pdf

17:30 Extending the fluid dynamic description of heavy-ions collisions to times before the collision

It is well established that the late states of a high energy nuclear collision can be described in terms of relativistic fluid dynamics. An open problem in this context is how the actual collision and the early time dynamics directly after it can be described. Phenomenological models are currently employed here and they have several parameters that need to be fitted to experimental data.
Using relativistic fluid dynamics of second order we develop a new approach which addresses the entire collision event, and which gets initialized in fact already before the collision. This is based on the droplet model for the incoming nuclei and a state-the-art equation of state including the first-order liquid-gas phase transition. The physics picture we propose assumes that the soft features of a high energy nuclear collision can be fully described through the dynamics of the energy-momentum tensor and other conserved currents.

This work is part of and supported by the DFG Collaborative Research Centre "SFB 1225 (ISOQUANT)".

Speaker: Andreas Kirchner (ITP Heidelberg)

QM_2023_poster.pdf

17:30 Far Forward Calorimetery for the EIC

The Electron Ion Collider offers unprecedented opportunities to image the proton and nuclei. The Far Forward detectors serve to classify the nature of the electron-proton or electron-nucleus interaction by identifying forward proton, neutrons and photons. This talk will review progress in developing an imaging Zero Degree Calorimeter for the EIC. The detector is designed to meet the stringent performance requirements of the EIC for energy and angular resolution for both neutrons and photons over a very large energy range. The fine granularity of the detector opens up the possibility to use machine learning techniques for shower reconstruction. The current status of the design and simulated preformance will be shown.

Speaker: Yuji Goto (Riken)

17:30 Feasibility of Spin Interference Gluon Tomography at the EIC with EPIC

One of the primary goals of the EIC is to deepen our understanding the multidimensional structure and distribution of gluons within nucleons and nuclei. The recent discovery of entanglement enabled spin interference in photonuclear heavy-ion collisions offers a powerful new avenue for exploring gluon distributions at high energy with RHIC and the LHC in the years leading up to the EIC. Most importantly, these novel polarization dependent observables provide direct access to information for constraining gluon transverse spatial distribution inside large nuclei. This poster discusses calculations of polarization dependent diffractive $J/\psi$ production at RHIC and LHC energies using the color glass condensate effective theory. The predictions have been extended to EIC energies and conditions, showing that strong azimuthal modulations are expected due to the initial photon polarization in diffractive photonuclear production at the EIC. In this poster, we assess the practicality and feasibility of these measurements considering the design characteristics of the EPIC experiment detector. As a final note, we comment on the complementary physics insights that can be gained from similar measurements via other vector meson production channels at existing experiments and at the future EIC.

Speaker: Sam Corey

SCorey_QM23_Poster_v3.pdf

17:30 Feasibility study of chiral symmetry restoration with ALICE

The origin of hadron masses cannot be attributed to the Higgs mechanism alone. On top of that, the spontaneous breaking of chiral symmetry potentially restored at extremely high temperatures, plays an important role. Low-mass vector mesons (ρ, ω, φ) are highly sensitive to chiral symmetry restoration effects, and their electromagnetic spectral function is expected to be modified in Pb-Pb collisions as compared to the “vacuum” spectral function measured in pp collisions. Chiral symmetry restoration can manifest itself in two different ways: a pole-mass shift or a broadening of the spectral function.
In this poster, the feasibility study for measuring ω meson in the dimuon channel using the ALICE forward muon tracker is presented. Results obtained using Run 2 data are used as a reference for studying the expected performance in Run 3 using the upgraded forward tracker. The measurement will be performed using the data that will be collected this year during the heavy-ion run.

Speaker: Keisuke Tomohiro (Hiroshima University (JP))

tomohiro_poster_QM23.pdf

17:30 Femtoscopy with Lévy sources

Exploring the space-time extent of particle production is 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, femtoscopic (momentum) correlations are utilized to gain information about the space-time geometry of the particle emitting source. Various experiments from SPS through RHIC to LHC measure Bose-Einstein quantum-statistical correlations. While early on the Gaussian assumption worked well when extracting source parameters, with precise data of today more advanced assumptions have to be used. This strongly affects our understanding of the collision energy dependence of source parameters, and relatedly the equation of state: a non-monotonic behavior in source widths may be overshadowed (or, to the contrary, caused) by the mixing of change in shape and in size. In this talk we review recent measurements, present several possible physical explanations (including critical behavior, anomalous diffusion and resonances) and their implications on various stages of evolution as well as the search for the critical endpoint of QCD.

Speaker: Mate Csanad (Eotvos University, Budapest)

csanad_QM2023_levy_poster.pdf

17:30 Finite volume effects on the chiral magnetic effect

In Heavy-Ion Collisions (HIC), the high temperature nuclear matter is expected to be produced with a chiral imbalance. The presence of a chiral imbalance can be detected in HIC by looking at observables related to the Chiral Magnetic Effect (CME). In off-central collisions,the nuclear matter also posses a very large vorticity. In order to preserve causality, a rotating system can not extend to infinity but must be confined in a finite region, for instance by means of a boundary condition.

We study a free gas of massless fermions confined in a finite cylinder in the presence of a constant magnetic field and with chiral imbalance. We impose the boundary condition using the MIT bag model and we compute the CME. We find that in a cylinder with fixed radius the CME current is decreasing for magnetic fields below a critical value that depend on the radius. Estimates and consequences in HIC are discussed.

Speaker: Matteo Buzzegoli

PosterCME_cylinder.pdf

17:30 First D$^0$-tagged jet axes difference measurement in pp collisions at $\sqrt{s} = 5.02$ TeV with ALICE

Measurements of heavy-flavor hadron production play an important role in the testing of pQCD calculations, and represent a critical component in studies of the quark-gluon plasma (QGP) created in heavy-ion collisions. We study three different D0-tagged jet axes, with varying degrees of sensitivity to wide-angle radiation: Standard, Soft Drop groomed, and Winner-Take-All (WTA). By considering the angles between different axes, we can study the radiation pattern inside the reconstructed jets, thus providing insight into the associated fragmentation and hadronization processes. In this poster, we present the first D$^0$-tagged jet axes difference studies carried out in pp collision at 5.02 TeV with the ALICE experiment at the LHC, with jets of transverse momentum $p_{\mathrm{T,jet}} > 5 \: \mathrm{GeV}/c$ and D$^0$-mesons with $p_{\mathrm{T,D^0}} > 2 \: \mathrm{GeV}/c$. The measurements include the radial distributions of D$^0$ mesons with respect to the jet axis, $\Delta R_{\mathrm{D,jet}}$, as well as a study of the opening angle, $\Delta R_{\mathrm{axis}}$, between various definitions for the axis of a D$^0$-tagged jet. We compare these results with those obtained from the inclusive, gluon-dominated, sample of jets. These measurements, at relatively low jet momentum, are sensitive to heavy-flavor production mechanisms and will serve as important groundwork for an in-depth understanding of charm-quark diffusion in the QGP.

Speaker: Emma Yeats

Emma_Jet_Axis_STD_D_Poster_QM.pdf

17:30 First Deuteron Production Measurement in Proton-Proton Interactions at SPS energies by NA61/SHINE

NA61/SHINE has measured the first deuteron production in proton-proton interactions at 158 GeV/c (sqrt(s) = 17.3 GeV). These measurements will be presented and compared to different nuclear formation models. The two most prevalent formation models—the thermal and coalescence models—are based on different underlying physics. A better understanding of (anti)nuclei production mechanisms is needed, which drives the effort to analyze high-statistics data sets from fixed-target experiments. Additionally, new updated measurements of proton, antiproton, π±, and K± spectra will be showcased, along with unique measurements of Omega and K0s production in p+p interactions.

Deuteron production measurements are important for understanding cosmic-ray antinuclei. The detection of cosmic antinuclei holds the potential to be a breakthrough approach for identifying dark matter signatures. The main source of cosmic antinuclei background are interactions between cosmic-ray protons and interstellar hydrogen gas. Gaining a deeper insight into deuteron production in p+p interactions is an essential first step in modelling these astrophysical processes. Furthermore, modeling of light antinuclei production typically requires antiproton production cross sections as input. Precise antiproton measurements are crucial. The updated hadron spectra exhibit significantly reduced statistical uncertainties and extend the phase space coverage in rapidity and transverse momentum compared to earlier measurements. These advancements can be employed to refine our understanding of proton-proton interactions.

Speaker: Anirvan Shukla (University of Hawai'i at Manoa (US))

230823_QM2023_draft_v1_shukla.pdf

17:30 First feasibility study for Asymmetric Cumulants of flow amplitudes in CBM at FAIR

Besides the traditional flow studies of individual flow amplitudes $v_n$, independent information about all stages in heavy-ion evolution can be extracted from multi-harmonic correlations of flow amplitudes. The simplest realization is Symmetric Cumulants (SC), which correlate the same-order moments of two or more flow amplitudes. In recent studies, it was demonstrated that SC can reveal the details of the differential temperature dependence of specific shear viscosity ($\eta/s$) of quark--gluon plasma, while individual $v_n$ amplitudes are sensitive only to the average values $\langle\eta/s\rangle$.

The generalization of SC to correlations involving different-order moments of flow amplitudes is not trivial, and it was accomplished only recently. These generalized flow observables are dubbed Asymmetric Cumulants (AC), and they by definition extract new and independent information in flow analyses that is not accessible either to $v_n$, nor to SC observables.

In this contribution, the first feasibility study for centrality dependence of AC is presented for data-taking conditions in CBM experiment at FAIR.

Speaker: Ante Bilandzic (Technische Universitaet Muenchen (DE))

Bilandzic_CBM_QM23-v5.pdf

17:30 First measurement of femtoscopic correlation function between $D^0$ mesons and charged hadrons in Au+Au collisions at ${\sqrt{s_{NN}}}$ = 200 GeV at STAR

Heavy quarks are produced in hard partonic scatterings at the very early stage of heavy-ion collisions and they experience the whole evolution of the Quark-Gluon Plasma medium. Femtoscopic correlations, i.e. two-particle correlations at low relative momentum, are sensitive to the final-state interactions as well as to the extent of the region from which the correlated particles are emitted. A study of such correlations between charmed mesons and identified charged hadrons could shed light on their interactions in the hadronic phase and the interaction of charm quarks with the medium.

In this poster, we will present the first measurement of femtoscopic correlations between $D^0-{\pi}$, $D^0-K$, and $D^0-proton$ pairs at mid-rapidity in Au+Au collisions at ${\sqrt{s_{NN}}}$ = 200 GeV using the data taken in the year 2014 and 2016 by the STAR experiment. $D^0$ mesons are reconstructed via the $K^{-}-{\pi}^{+}$ decay channel using topological criteria enabled by the Heavy Flavor Tracker with excellent track pointing resolution. We will present the femtoscopic correlation function for $D^0$ transverse momentum above 1 GeV/c in the $0-80\%$ centrality. We will also compare the experimental results with available theoretical models and discuss physical implications.

Speaker: Priyanka Roy Chowdhury

QM2023_poster_FINAL_Priyanka.pdf

17:30 First measurement of properties of strong interaction between deuterons and light hadrons in Pb--Pb collisions with ALICE

Accurate knowledge of the strong interaction between charged kaons and (anti)deuteron is a missing piece of information in the field of the low-energy (anti)kaon-nucleon interactions for more than 40 years. The interaction between charged kaons and (anti)deuterons is a complex subject at both experimental and theoretical levels. From the experimental point of view, so far scattering cross sections at intermediate momenta were performed. Specific information on the strong interaction can be accessed also via kaonic deuterium X-ray spectroscopy but such measurements are challenging due to the available detection efficiency. One of the missing information on $\mathrm{K^{-} d}$ and $\mathrm{K}^{+} \mathrm{d}$ interactions is their scattering lengths. Due to the lack of direct experimental measurements, theoretical predictions for $\mathrm{K}^{-} \mathrm{d}$ have been made based on input from kaonic hydrogen measurements. There are no published theoretical predictions for the scattering length of $\mathrm{K^{+} d}$. The first femtoscopic measurement of $\mathrm{K}^{+} \mathrm{d} \oplus \mathrm{K}^{-}\overline{\mathrm{d}}$ and $\mathrm{K}^{-} \mathrm{d} \oplus \mathrm{K}^{+} \overline{\mathrm{d}}$ in Pb--Pb collisions at $\sqrt{s_{\rm NN}}=5.02\ \mathrm{TeV}$ are presented. In this study, the scattering lengths of $\mathrm{K}^{+} \mathrm{d}$ and $\mathrm{K}^{-} \mathrm{d}$ pairs associated with strong final-state interactions, as well as the source radii of the kaon-deuteron pairs were determined using the Lednický-Lyuboshitz model. The interaction parameters obtained for $\mathrm{K}^{+} \mathrm{d} \oplus \mathrm{K}^{-} \overline{\mathrm{d}}$ and $\mathrm{K}^{-} \mathrm{d} \oplus \mathrm{K}^{+} \overline{ \mathrm{d}}$ are compared with the values available in the literature to discriminate between the different theoretical approaches.

Speaker: Wioleta Rzesa (Warsaw University of Technology (PL))

posterQM_2023_wrzesa.pdf

17:30 First Performance results of the sPHENIX Event Plane Detector

The sPHENIX detector is designed to study fundamental properties of the quark-gluon plasma created in heavy ion collisions at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory. The sPHENIX Event Plane Detector (sEPD) is constructed both in the forward and backward rapidity region with the coverage of 2.1 $<|\eta|< $4.9. The essential role of the sEPD is to provide event plane determination with high resolution as well as centrality determination in Au+Au collisions. This poster will discuss the first performance results of the sEPD, covering cosmic tests of the sectors and calibration results from the first sPHENIX run. Implications for potential physics measurements will be discussed.

Speaker: Jaebeom Park

QM2023_SEPD_JBP_v4.pdf

17:30 First results on spectra of identified hadrons in central Xe+La collisions from NA61/SHINE at CERN SPS

The first results on identified hadron spectra produced in central Xe+La collisions at SPS will be presented. The kinematic distributions and measured multiplicities of identified hadrons will be compared with previously released by NA61/SHINE results on p+p, Be+Be, Ar+Sc and NA49 Pb+Pb results, as well as with available world data.

Obtained results, and in particular ratio of positively charged kaons to pions, are crucial for the understanding of the phenomena of the onset of deconfinement and the onset of fireball, which are one of the main studies in the strong interactions program of the NA61/SHINE experiment.

Speaker: Piotr Podlaski (University of Warsaw (PL))

Panova_poster_QM.pdf

17:30 Flavor equilibration of the quark-gluon plasma

During the early hydrodynamic phase, the chemical composition of the quark-gluon plasma (QGP) is still largely unknown. Here we study the effects of quark chemical equilibration on the QGP using a novel model of viscous hydrodynamic evolution in partial chemical equilibrium. In this model, we initialize the QGP in a completely gluon dominated state, as motivated by the success of gluon saturated initial condition models. Local light and strange quark production during the hydrodynamic phase is simulated through the evolution of time-dependent fugacities for each quark flavor, with the timescales set as free parameters to compare different rates of equilibration. This impacts the system through the equation of state, which we have constructed to depend on the quark flavor content throughout the QGP.

Using this model, implemented in the MUSIC hydrodynamic code and iS3D particlization code, we have simulated ensembles of Pb+Pb and Au+Au collision events with varying quark chemical equilibration times. We discuss the observed dependence of hadronic and electromagnetic observables on the equilibration time. We also examine the impact of quark chemical equilibration on the transport properties of the QGP, and show preliminary results for a Bayesian model-to-data comparison that will simultaneously constrain the equilibration times and transport coefficients of the QGP.

Speaker: Andrew Gordeev

QM2023_Gordeev_Andrew.pdf

17:30 Flow harmonic measurements up to order 10 in PbPb collisions with CMS

Higher order flow harmonics provide a powerful probe of the initial geometry of heavy ion collisions, as well as the properties of the quark-gluon plasma produced in these collisions, including the transport coefficients and the degree of collective behavior. This poster presents higher order flow harmonics measurements in PbPb collisions at $\sqrt{s_{_{\mathrm{NN}}}} = 5.02$~TeV using data from the CMS experiment. We will discuss the centrality dependence of flow harmonics up to order 10 and compare them to theory calculations and lower order measurements.

Speaker: Andi Mankolli (Vanderbilt University (US))

17:30 Forward Physics with light vector mesons and $\pi^0$ from the PHENIX Experiment

Forward and backward rapidity regions are rich laboratories to explore several effects which happens to a probe before and after its hard scattering. The large rapidity region may also experiment a different dynamics for strangeness enhancement seen in heavy ion collisions at RHIC and LHC. The PHENIX experiment has a long history of large rapidity measurements with the muon spectrometers covering 1.2$<|\eta|<$2.2 and a forward calorimeter (MPC) covering 3.1$<|\eta|<$3.8. The addition of a pre-shower detector, the MPC-ex in front of the MPC, allows the identification of $\pi^0$ in a broad momentum range covering a Bjorken-x region between $10^{-3}-10^{-2}$. This presentation will report two measurements: i)$\phi$ meson nuclear modification using the muon spectrometer in $d$+Au, Cu+Au and Au+Au which can explore how strangeness are affected by initial and final state effects and its behavior in QGP at large rapidity; ii) $\pi^0$ nuclear modification factor in $d$+Au collisions which are sensitive to parton shadowing and gluon saturation.

Speaker: Uttam Acharya (Georgia State University)

QM_poster_draft_UA_updated.pdf

17:30 Generation of magnetic field in relativistic heavy-ion collisions

Various interesting phenomena have been predicted to occur in a quark-gluon plasma produced in relativistic heavy-ion collisions due to a strong magnetic field which is also generated in these collisions. However, none of these predictions has been convincingly confirmed experimentally yet. So, the question is why? Our aim is to systematically discuss the problem of magnetic field generation. In particular, we argue that the currents induced in the plasma, which have been expected to sustain the magnetic field throughout the plasma lifetime, are much smaller than expected. This happens because the quark-gluon plasma is initially mostly composed of gluons while electrically charged quarks appear with a delay.

Speaker: Patrycja Słoń (National Centre for Nuclear Research)

17:30 Heavy flavor hadrons inside jets at sPHENIX

The sPHENIX experiment at RHIC will begin commissioning with Au+Au data in Spring 2023. The Monolithic Active Pixel Sensor (MAPS) based Vertex Detector (MVTX), the Intermediate Silicon Tracker (INTT) and the Time Projection Chamber (TPC) at sPHENIX can provide high precision primary/displaced vertex and track reconstruction in the pseudorapidity region of $|\eta| \le 1.1$. The sPHENIX ElectroMagnetic Calorimeter (EMCal) and Hadronic Calorimeter (HCal), used for the first time at RHIC, will provide good energy measurements for full jet reconstruction. sPHENIX will enable an unprecedented series of high precision heavy flavor hadron and jet measurements at sPHENIX in 200 GeV p+p, p+Au and Au+Au collisions. In particular, the heavy flavor hadron inside jet production can provide vital information about the heavy quark hadronization process and how such process gets modified in a nuclear medium. Less recombination contribution to the hadron production is expected at RHIC compared to the Large Hadron Collider (LHC) measurements, which makes these measurements an unique approach to explore the universality of heavy quark fragmentation functions in different nuclear environments. We will present the performance projection of the D-meson inside jet reconstruction, the hadron-jet relative kinematic variable distributions, and projections in 200 GeV p+p and Au+Au simulations with realistic sPHENIX detector performance. We will also report on the status of the heavy flavor physics analyses.

Speaker: Antonio Carlos Oliveira Da Silva (Iowa State University)

QM2023_DJets_final.pdf

17:30 Heavy flavor phenomenology in Pb+Pb collision with IP-Glasma initial state and Bayesian calibrated hydrodynamics

Heavy quarks serve as effective probes of relativistic heavy-ion collisions as they are created in the initial stages of the collision event and exist at all stages. We study the dynamics of heavy flavors using a hybrid framework that incorporates the MARTINI event generator, pythia8.1 for the initial production of heavy quarks, and Langevin dynamics to describe the evolution of heavy quarks in a 3+1-D expanding QGP medium. We include the interactions of heavy quarks with the medium constituents through the heavy quark transport coefficients. The space-time expansion of the QGP medium is described using the hydrodynamical approach MUSIC with IP-Glasma initial state and Bayesian-quantified viscous coefficients of the strongly-interacting matter. The properties of the QGP medium are probed by analyzing the heavy meson nuclear modification factor and flow coefficient for Pb+Pb collision. In this work utilizing for the first time IP-Glasma fluctuating initial states and hydrodynamics tuned to a global Bayesian analysis, we show that the observables associated with D-mesons are strongly influenced by the IP-Glasma initial state and bulk evolution. Additionally, we provide new insights into the interaction strength of charm quarks in the expanding medium, including elastic collisional processes with medium constituents, gluon emission processes, and non-perturbative interactions.

Speaker: Dr Manu Kurian (McGill University)

QM Poster_Manu portrait.pdf

17:30 Heavy Flavor Physics with MVTX Detectors in sPHENIX

The sPHENIX experiment will begin commissioning in Spring 2023 at the Relativistic Heavy Ion Collider (RHIC) at BNL, presenting a unique opportunity to study QGP properties using jets and heavy quarks with unprecedented precision. The successful construction and deployment of the three-layer Monolithic-Active-Pixel-Sensor (MAPS) based VerTeX detector (MVTX) for the sPHENIX experiment in 2023 enables precise measurements of heavy bottom quark jets (b-jets) and B-hadrons produced in high-energy heavy-ion Au+Au and p+p collisions at RHIC. These measurements offer a unique set of observables given the large bottom quark mass. These measurements will span an unexplored kinematic regime, particularly at low p$_T$ where mass-dependence effects in QGP are expected to be significant, while the underlying backgrounds are also expected to be high.
The MVTX detectors serve as the innermost tracking system of the sPHENIX experiment, covering 2.5-4.0 cm radially and a pseudorapidity range of $|\eta|$ < 2. With its very fine 27 $\mu$m x 29 $\mu$m pixels, the MVTX detector can identify heavy hadron decay secondary vertices and heavy flavor jets in heavy ion collisions with high efficiency and purity. In this poster, we will highlight the impact of the MVTX detector on future heavy flavor measurements, including b-hadrons and b-jets in heavy ion collisions and will present the status of the MVTX detector commissioning.

Speaker: Dr Yasser Corrales Morales (Los Alamos National Laboratory (US))

YCM_2023QM_Poster_final.pdf

17:30 Heavy quarks dynamics in the early stage of high energy nuclear collisions

The early stage of high-energy nuclear collisions is dominated by strong gluon fields called the evolving Glasma. This stage can be probed by heavy quarks (HQs), charm and beauty, since they are produced almost immediately by hard scatterings. We study the propagation of HQs in the evolving Glasma fields, by solving the relativistic kinetic equations that couple the HQs to the fields themselves. We analyze the impacts of this (so far) neglected dynamics on observables, namely the nuclear modification factor and the elliptic flow. We find that both these quantities are affected in a substantial way by the propagation in the early gluon fields.

Speaker: Prof. Marco Ruggieri (University of Catania)

17:30 Heavy-ion perspectives and prospects for LHCb upgrades

Owing to its spectrometer acceptance, which is complementary to the other
LHC experiments, LHCb is collecting several fixed-target and ion collision sam-
ples, providing unique inputs to theoretical models in poorly explored kinematic
regions. In this contribution, the impact of the ongoing and foreseen upgrades
of the LHCb experiment on the ions and fixed-target physics programme are
discussed, notably including the installation of tracking station inside the mag-
net and the replacement of some tracker detectors to avoid saturation in central
lead-lead collisions.

Speaker: Imanol Corredoira (Universidade de Santiago de Compostela (ES))

LHCb_QM23_HI_upgrade_icorredo.pdf

17:30 Helical vortical effect and matter/anti-matter polarization asymmetry

It is well-known that vorticity induces polarization in quantum plasmas via chiral vortical effect (CVE). Besides the CVE-induced axial current, vorticity gives rise in the presence of a net baryon charge also to a helicity current via the novel helical vortical effect (HVE) [1], which is the focus of the present talk. The HVE and CVE applied together naturally explain the matter/anti-matter polarization asymmetry seen in the experimental data for hyperons reported by STAR [2].

[1]: Victor E. Ambrus, M. N. Chernodub, Eur. Phys. J. C 83 (2023) 111. DOI: 10.1140/epjc/s10052-023-11244-0.
[2]: Victor E. Aambrus, M. N. Chernodub, Eur. Phys. J. C 82 (2022) 61. DOI: 10.1140/epjc/s10052-022-10002-y.

Speaker: Victor Ambrus

Ambrus_QM2023_poster_custom.pdf

17:30 Helicity polarization and vorticity contribution to the spin alignment in hydrodynamic approaches

We investigate the hydrodynamic helicity polarization of Λ hyperons, defined as the projection of the spin polarization vector along the directions of particle momenta, at RHIC-BES energies by utilizing the relativistic (3+1)D CLVisc hydrodynamics framework with SMASH initial conditions. As opposed to local spin polarization at high energy collisions, our hydrodynamic simulations demonstrate that the helicity polarization induced by the kinetic vorticity dominates over other contributions at intermediate and low collision energies. Our findings provide an opportunity to probe the fine structure of local kinetic vorticity as a function of azimuthal angle at intermediate and low collision energies by mapping our predictions to the future measurements in experiments. In addition, we also study the vorticity contribution to 00 component of the spin density matrix for final $\phi$ mesons $\overline{\rho}_{00}^{\phi}$.

Speaker: Cong Yi

17:30 Hybrid Hadronization of Jet Showers in Vacuum with JETSCAPE

In this talk we review the hadronization of jets in various vacuum collision systems using the JETSCAPE event generator and Hybrid Hadronization. Hybrid Hadronization combines quark recombination, applicable when distances between partons in phase space are small, and string fragmentation appropriate for dilute parton systems. It can therefore smoothly describe the transition from very dilute parton systems like to full AA collisions. We test this picture by using JETSCAPE to generate jets in various systems. Comparison to experimental data for several observables at multiple energies allows for a precise calibration of vacuum baseline parameters in JETSCAPE and Hybrid Hadronization. We use charged hadron, identified hadron and jet spectra in a Bayesian calibration to find the best parameter tune. The inclusion of further observables in p+p and e+e- in the future is discussed.

Speaker: Cameron Parker

QM2023.pdf

17:30 Hydrodynamic initial conditions from non-linear causality

Relativistic hydrodynamics has been successful in describing space-time evolution of matter created in high-energy nuclear collisions. It is conventionally supposed that the created matter starts to behave as fluids all at once at a certain initial time. It is, however, not at all trivial from which stage after the collision the fluid picture can be applied to the system. According to the hydrodynamization theory [1], any solutions of hydrodynamic equations converge to an attractor. Thus, hydrodynamic description might be justified anyway even starting from the system far away from local equilibrium. Do we really describe space-time evolution of the system using hydrodynamics even when the system is far away from local equilibrium? In this study, we address this issue from a point of view of causality.
A recent study shows necessary and sufficient conditions for the solutions to be causal in non-linear relativistic hydrodynamic equations [2]. When they are applied to numerical hydrodynamic simulations, it turns out that causality tends to be violated at the early time and/or in peripheral regions [3]. This indicates that violation of causality has something to do with how far the system is away from local equilibrium. Motivated by these observations, we scrutinize a one-dimensionally expanding conformal system from a view point of causality and constrain the initial conditions whose solutions by no means violate the causality. We first define the degree of non-equilibrium and then describe its time evolution solving the Muller-Israel-Stewart type constitutive equation in one-dimensionally expanding system. We find that it is acausal in fact when the system is far away from local equilibrium. Using these solutions, we quantify a range of the inverse Reynolds number in which hydrodynamic description is justified from a view point of causality. This sheds light on the understanding of initial stages in high-energy nuclear collisions.

References:
[1] M.P. Heller and M. Spalinski, Phys. Rev. Lett. 115, 072501 (2015).
[2] F.S. Bemfica et al., Phys. Rev. Lett. 126, 222301 (2021).
[3] C. Plumberg et al., Phys. Rev. C 105, L061901 (2022).

Speaker: Tau Hoshino (Sophia University)

QM2023(Hoshino).pdf

17:30 Hydrodynamic theories for a system of classical weakly self-interacting ultra-relativistic scalar particles

Relativistic hydrodynamics has been widely employed in high energy nuclear physics, with applications in heavy-ion collisions, neutron star mergers and coalescing matter in black holes [1]. Due to the acausality and instability of relativistic Navier-Stokes (NS) theory [2], one usually employs Israel-Stewart-like (IS) formulations of fluid dynamics [3] in which the constitutive relations for the dissipative currents are replaced by relaxation type equations. This comes at the expense of a more complex structure of the partial differential equations being solved, which renders the assessment of features of solutions in the non-linear regime very intricate. More recently, the Bemfica-Disconzi-Noronha-Kovtun (BDNK) theory has emerged [4], where theorems for causality, linear stability and existence of solutions can be rigorously established, but unconventional matching conditions are required. For all of the aforementioned theories, transport coefficients play a fundamental role. However, their computation is usually a very non-trivial task, even in the context of Kinetic Theory. We show that this difficulty can be circumvented for a system composed of classical ultra-relativistic scalar particles weakly interacting via a quartic potential. Then, the specific form of the cross-section [5] allows for the computation of transport coefficients without approximations beyond the power-counting scheme of the corresponding hydrodynamic theory. In this contribution, we calculate all transport coefficients of NS, BDNK and IS theories and demonstrate, in a Bjorken flow scenario, that NS and BDNK theories are pathological for large gradients and thus cannot be used to describe the early stages of heavy ion collisions. For BDNK and IS theories, attractor solutions are also analyzed.

[1] W. Florkowski. Lect.Not. Phys. 999, 63-85, 2022; M. Chabanov et al.. Mon. Not. Roy. Astron. Soc., 505(4):5910–5940, 2021

[2] G. Pichon. Ann. de l’IHP Phys. th., vol. 2, p. 21–85, 1965;
W. A. Hiscock and L. Lindblom. Ann. of Phys., 151(2):466–496, 1983;

[3] W. Israel and J. M. Stewart. Ann. Phys., 118:341–372, 1979; G. S. Denicol et al. Phys. Rev. D, 85:114047, 2012. [Erratum: Phys.Rev.D 91, 039902 (2015)];

[4] F.S. Bemfica et al. Phys. Rev. X, 12(2):021044, 2022; P. Kovtun. JHEP, 10:034, 2019

[5] G. S. Denicol and J. Noronha. arXiV:2209.10370

Speaker: Gabriel Soares Rocha

Poster_QM23_Gabriel-Soares-Rocha.pdf

17:30 Hypernuclei studies in heavy-ion collisions with the CBM experiment at FAIR

Under the extreme conditions of relativistic heavy-ion-collisions hypernuclei are created with large abundancies. Hypernuclei measurements provide insights into the equation-of-state of hadronic matter at high net-baryon densities, as well as into hyperon-nucleon and hyperon-hyperon-interactions. The Compressed Baryonic Matter (CBM) experiment at the future Facility for Anti-Proton and Ion Research (FAIR) in Darmstadt offers the perfect conditions to explore the production of hypernuclei. The excitation function of hypernucleus production exhibits its maximum in the FAIR energy range. In combination with the foreseen high interaction rates of up to 10 MHz, an exceptionally high amount of hypernuclei such as e.g. $^{4}_{\Lambda}$H and $^{5}_{\Lambda}$He will be created, and even very rare double hypernuclei like ${}^{6}_{\Lambda\Lambda}$He are expected with sizeable statistics.
The reconstruction of the hypernuclei-3-body-decay was implemented into the CBM reconstruction software and optimized with respect to important performance indicators. In addition, the reconstruction was performed with a neural network. Expected efficiencies and signal-to-background-ratios were calculated with both approaches for a reliable estimation of the number of reconstructable hypernuclei. Systematical uncertainties were estimated based on simulations with different transport models (e.g. PHQMD), taking into account the signal extrapolation to the full rapidity and transverse momentum range. The experimental sensitivity to properties of hypernuclei, such as their lifetime, was evaluated. Results for $^{3}_{\Lambda}$H will be discussed in detail. Reconstructed mass spectra for $^{4}_{\Lambda}$H, $^{4}_{\Lambda}$He and $^{5}_{\Lambda}$He will be shown in addition. (Work supported by DFG-grant BL 982/3-1)

Speaker: Susanne Glaessel

230831_PosterQM_Hypernuclei_CBM_SG_747.pdf

17:30 Hyperon Polarization in Isobar Collisions and Correlation of Global Polarization with Directed Flow from STAR

The observation of hyperon polarization has revealed the existence of large vorticities in the medium created by heavy-ion collisions. Global polarization indicates vorticities perpendicular to the reaction plane due to the system's orbital angular momentum, while local polarization indicates vorticities along the beam direction due to anisotropic transverse expansion of the medium. With the high-statistics data collected by the STAR experiment for isobar Ru+Ru and Zr+Zr collisions at $\sqrt{s_{\mathrm{NN}}} = 200$ GeV, we present the measurements of global polarization for $\Lambda$, $\bar{\Lambda}$, and $\Xi^{\pm}$ as a function of centrality, transverse momentum, pseudorapidity, and azimuthal angle relative to the event plane. These measurements allow us to study possible magnetic field driven effects through the polarization difference between Ru+Ru and Zr+Zr, owing to a larger magnetic field expected in the former.

Furthermore, the first measurements of $\Lambda$ hyperon local polarization along the beam direction relative to the second and third-order event planes in isobar collisions will be presented. Comparisons with previous measurements in Au+Au and Pb+Pb collisions at RHIC and the LHC will be performed to gain important insights into the collision system size and energy dependence of the vorticities in heavy-ion collisions.

Previous measurements have shown a similar trend in the energy dependence between the global polarization and the slope of directed flow, suggesting a strong correlation between the initial tilt of the system and the vorticity [1]. For the first time, this correlation is investigated, and the dependence of the $\Lambda$ global polarization as well as directed flow on the first-order flow vector ($q_1$) is presented in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}} = 19.6$ GeV.

[1] S. A. Voloshin, EPJ Web Conf. 171 (2018) 07002.

Speaker: Kosuke Okubo

QM2023poster_KosukeOkubo_ver4.pdf

17:30 Hyperon reconstruction method with machine learning in Pb-Pb collisions at ALICE

Reconstructing hyperons with high purity and high reconstruction efficiency is essential for measurements of hyperon-hyperon correlation and searches for exotic strange hadrons, which are both presently discussed topics in the QCD community. Hyperons can be abundantly produced in Pb-Pb collisions at LHC. However, achieving high purity of reconstructed hyperons with high efficiency is particularly challenging in high charged-particle multiplicity environments.
The conventional reconstruction method of ALICE rejects many hyperon candidates by using topological cuts. To improve the detector performance, we studied the reconstruction of all hyperon candidates based on their decay vertex using the Kalman Filter (KF) technique. Furthermore, a Boosted Decision Tree (BDT) algorithm is applied to the LHC Run 2 Pb-Pb collision data based on the training by the combinatorial background and Monte Carlo simulation. By inputting many parameters for decay vertex reconstruction, we can make finer adjustments than would be possible by simply applying topological cuts manually. Therefore, BDT may help optimize cuts to better separate signal and background. This poster will report the current status of the reconstruction of Λ, Ξ, and Ω with the KF approach, discussing its performance and prospects for the future. These developments are important for the high-luminosity Pb-Pb data-taking campaign foreseen at the end of 2023.

Speaker: Ryoka Tokumoto (Hiroshima University (JP))

QM_ryoka.pdf

17:30 Hypertriton Production in Au+Au Collisions from $\sqrt{s_{NN}}=7.7$ to $27$ GeV from STAR

Hypernuclei, bound states of nucleons and hyperons, serve as a natural laboratory to investigate the hyperon-nucleon ($Y$-$N$) interaction, which is an important ingredient for the nuclear equation-of-state. Furthermore, precise measurements of their production yields in heavy-ion collisions are crucial for understanding their production mechanisms. In addition, the strangeness population factor, $S_{\rm 3}=(^{3}_{\Lambda}\mathrm{H}/^{3}\mathrm{He})/(\Lambda/p)$, is of particular interest as it has been suggested to be sensitive to baryon-strangeness correlations and the onset of deconfinement.

The STAR Beam Energy Scan II program provides a unique opportunity to investigate the collision energy and system size dependence of hypernuclei production. In this poster, we present new measurements on the transverse momentum and centrality dependence of $\rm ^{3}_{\Lambda}H$ yields in Au+Au collisions from $\sqrt{s_{NN}}=7.7$ to $27$ GeV. The $\rm ^{3}_{\Lambda}H/\Lambda$ ratio and $S_{3}$ will be presented as functions of collision energy and centrality. These results are compared to model calculations, and their physics implications will be discussed.

Speaker: Yue Hang Leung (University of Heidelberg)

qm2023_poster_v2.pdf

17:30 Identifying nuclei with time-of-flight at LHCb

Antimatter in cosmic rays is a powerful probe for Dark Matter indirect de-
tection. To constrain the background from secondary antiparticles, produced
during cosmic ray propagation through the interstellar medium, the related cross
sections need to be precisely determined at accelerator facilities. In particular,
being their secondary production suppressed at low energies with respect to
DM signal predictions, light anti-nuclei like anti-deuterium and anti-helium are
smoking guns for exotic sources. The LHCb experiment currently offers a unique
fixed-target facility exploiting the beam energy provided by LHC and can re-
produce cosmic collisions between protons at the TeV scale and gas targets of
helium. In this poster, we will present the implementation of a new particle identification technique optimized for heavy particles like light nuclei, based on
a time-of-flight measurement in the LHCb Outer Tracker detector, with a fo-
cus on the first performance results obtained on data. Applications in future
analyses will also be discussed

Speaker: Chiara Lucarelli (Universita e INFN, Firenze (IT))

QM23_poster.pdf

17:30 Identifying quenched jets in heavy ion collisions with machine learning

Measurements of jet substructure in ultra-relativistic heavy ion collisions suggest that the jet showering process is modified by the interaction with quark gluon plasma. Modifications of the hard substructure of jets can be explored with modern data-driven techniques. In this study, we use a machine learning approach to identify jet quenching amounts. Jet showering processes, with and without the quenching effect, are simulated with the JEWEL model, and are embedded with thermal backgrounds. Sequential substructure variables are extracted from the jet clustering history following an angular-ordered sequence, and are used in the training of a neural network built on top of a long short-term memory network. We measure the jet shape and jet fragmentation functions for jets classified with the neural network outputs, and quantify their in-medium modifications. The results support that the machine learning approach successfully identifies the quenching effect in the presence of the large uncorrelated background of soft particles created in heavy ion collisions.

Speaker: Yilun Wu (Vanderbilt University)

YilunWu_MachineLearning_Jets.pdf

17:30 Imaging the shape of atomic nuclei in high-energy nuclear collisions from STAR

The collective properties of nuclear structure, such as radii and deformations, leave distinct signatures in the initial and consequently final stages of relativistic heavy-ion collisions. Collisions of deformed nuclear enhance the fluctuations of harmonic flow coefficients $v_n$ and event-wise mean transverse momentum $[p_T]$, therefore offering a viable approach to establish clear correspondences between the structure of colliding nuclei and the final state observables.

We present measurements of $v_n$, $[p_T]$ fluctuations as well as $v_n$-$[p_T]$ correlations from the STAR experiment. Significant differences are observed for [$p_T$] fluctuations and $v_n$-$[p_T]$ correlations between $^{197}$Au+$^{197}$Au and $^{238}$U+$^{238}$U collisions, which can be quantitatively explained by the large prolate deformation of $^{238}$U with $\beta_{2, \mathrm{U}} \sim 0.28$ and $\gamma_{\mathrm{U}} \sim 0$. Striking differences are also observed in isobar collisions of $^{96}$Ru+$^{96}$Ru and $^{96}$Zr+$^{96}$Zr, where ratios of many observables show significant deviations from unity and exhibit rich patterns as a function of centrality. A comparison with hydrodynamic model simulations suggests a large quadrupole deformation in Ru nucleus with $\beta_{2, \mathrm{Ru}} \sim 0.16$ and a large octupole deformation in $^{96}$Zr nucleus with $\beta_{3, \mathrm{Zr}} \sim 0.2$. The non-monotonic dependence of ratios of multiplicity distribution, $v_2$, and $[p_T]$ fluctuations in the mid-central collisions also requires a difference in the surface diffuseness between $^{96}$Ru and $^{96}$Zr in the model
calculations. Combining all these observables, we can precisely constrain the parameters associated with various nuclear deformations in isobar nuclei. Building on our pioneering demonstration of nuclear structure effects, we present a more precise quantitative extraction of the quadrupole and octupole deformation parameters in $^{96}$Ru and $^{96}$Zr nuclei using heavy-ion collisions.

Speaker: Chunjian Zhang (Stony Brook University)

QM2023_poster_CZhang.pdf

17:30 In-Situ Calibration of the sPHENIX Hadronic Calorimeter using Isolated Single Hadrons

A first goal from early running of the sPHENIX detector, which has begun data-taking this year, is to ensure an accurate calibration of its calorimeters and a complete understanding of the uncertainties associated with these calibrations. Both of these steps are necessary for successfully achieving the physics goals of sPHENIX, especially in conducting various high-precision jet measurements with sPHENIX having the first hadronic calorimeter at mid rapidity at RHIC. This study explores measurements of the calorimetric response to single hadrons in the sPHENIX calorimeter system, which is comprised of an electro magnetic calorimeter, followed by an inner and outer hadronic calorimeter made of aluminum and steel absorber, respectively. In this study, the momentum p of isolated tracks, those separated by a minimum distance from the nearest other tracks, are found utilizing the sPHENIX charged-particle tracking systems and are matched to calorimeter energy deposits with energy E; E/p distributions are then constructed for use in precise data-to-MC comparisons. The methodology regarding the minimization of background energy from neutral particles within the track isolation area will also be presented. These measurements can be used to understand the hadronic response and quantify the uncertainty in the calorimeter hadronic response between data and MC.

Speaker: Emma McLaughlin

QM_2023_Emma_McLaughlin.pdf

17:30 Influence of the latest hadronic resonances from the particle data group on thermal models, lattice QCD comparisons, and SMASH

The number of hadron resonances used in heavy-ion collisions simulations affects both the final observables and parameters (e.g., transport coefficients) extracted from numerical simulations. This list of resonances is typically taken from the Particle Data Group (PDG) that releases a new list on approximately a yearly basis. Here we update our hadron resonance list to the PDG 2021 including all $*~–****~$ states and make direct comparisons to lattice QCD susceptibilities and partial pressures where an improvement is seen since recently-observed particles have been included in the strange baryonic sector. Additionally, we reanalyze thermal models with this new list and extract the freeze-out temperatures. A next crucial step is to reformat our list to be compatible with SMASH such that hydrodynamic simulations can use the latest PDG list as well [1]. Before this change, SMASH has approximately half of the resonances included in the PDG 2021 list. To include these new states in SMASH we have rewritten the list that contains $1\to3$ and $1\to4$ body decays to include only $1\to2$ body decays and study this change on the particle spectra and mean transverse momentum. Finally, we find that the additional states improve the SMASH cross-sections, although some rescaling is required.

[1] Preliminary results: Salinas San Martin et al., Rev. Mex. Fis. Suppl. 3 (2022) 4, 040921.

Speaker: Jordi Salinas San Martin

Jordi_Salinas_San_Martin-QuarkMatter2023_Poster.pdf

17:30 Insights on small collision systems in terms of hydrodynamics, pre-hydrodynamics, decorrelations, and non-flow

The study of small collision systems at RHIC (pp, pA, dA, $^{3}$HeA, OO) and the LHC (pp, pPb, OO) provide crucial insights into the limits of quark-gluon plasma formation. Recently, we have analyzed new experimental results in terms of hydrodynamics, pre-hydrodynamics, decorrelations, and non-flow (Phys.Rev.C 105 (2022) 2, 024906). We extend these studies to include ultra-peripheral collisions and additional collision geometries. Disentangling these effects is important for understanding the role of the earliest stages of pre-hydrodynamics and any potential role for initial state correlations. Specifically the role of intrinsic versus fluctuation geometries will be detailed.

Speaker: James Lawrence Nagle (University of Colorado Boulder)

17:30 Interpretable Machine Learning applications to Jet Background Subtraction

Previous applications of machine learning to jet background subtraction have shown improvements over the traditional background subtraction methods, especially at low jet momentum. While machine learning applications generally lead to improvements, care must be taken to ensure they are not at the cost of interpretability and bias from models used for training. We present a novel application of symbolic regression to extract a functional representation of a deep neural network trained to subtract background for measurements of jets. With this functional representation we show that the relationship learned by a neural network is approximately the same as a new background subtraction method using the particle multiplicity in a jet. This multiplicity method uses measured features, rather than learned weights, to achieve most of the improvements demonstrated by the deep neural network. Additionally, we show the algorithmic complexity of the deep neural network can be decreased by reducing it to a shallower representation while still achieving similar performance. Our study demonstrates that interpretable machine learning methods can provide insights into underlying physical processes and achieve the performance of black-box machine learning without the opaqueness and model bias.

Speaker: Tanner Mengel (University of Tennessee)

QM_poster_tmengel.pdf

17:30 Investigating charm quark production in and outside of jets using the ALICE detector at the LHC

Heavy-quark hadrons are used to study the properties of the partonic stages of a heavy-ion collision, where a quark-gluon plasma medium is created. We are investigating charm quark production in and outside of jets via angular correlations of trigger hadrons and associated electrons from heavy-flavor hadron decays. As a first step, we are investigating the 5.02 TeV p-Pb collisions, where in a previous analysis a difference of the strangeness production in jets compared to the underlying event for increasing collision system size was observed. With this new analysis, we aim at investigating the flavor-dependence of particle production in jets and the underlying event. In this contribution, the different analysis steps will be described, including the strategy of particle identification and rejection of background, such as electrons from photon conversions and Dalitz decays, in p-Pb collisions. The Time Projection Chamber (TPC) is used to identify electron candidates via differential energy loss (d$E$/d$x$) in the low momentum region.

Speaker: Josephina Rae Wright (University of Texas at Austin (US))

QuarkMatterPosterPDF.pdf

17:30 Investigating collective effects in small collision systems using PYTHIA8 and EPOS4 simulations

Studies have yielded strong evidence that a deconfined state of quarks and gluons, the quark--gluon plasma, is created in heavy-ion collisions. This hot and dense matter exhibits almost zero friction and a strong collective behavior. An unexpected collective behavior has also been observed in small collision systems. In this talk, the origin of collectivity in small collision systems is addressed by confronting PYTHIA8 and EPOS4 models using measurements of azimuthal correlations for inclusive and identified particles. In particular, anisotropic flow coefficients measured using two- and four-particle correlations with various pseudorapidity gaps, per-trigger yields, and balance functions are reported in pp collisions at $\sqrt{s}=13.6$ TeV and p--Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV. The results are compared with the available experimental data.

Speaker: Andrea Danu (Institute of Space Science (RO))

17:30 Investigating the $R$-Dependence of Jet Suppression

Jet quenching measurements in heavy-ion collisions, such as the suppression of the jet yield compared to pp collisions, aim to elucidate the various mechanisms of parton energy loss. Differential measurements of the dependence of the inclusive jet nuclear modification factor ($R_{\rm AA}$) on the jet resolution parameter ($R$) may help disentangle energy loss mechanisms and discriminate between different jet quenching models. One recent $R$-dependence measurement by the ALICE collaboration hints that large-$R$ jets lose more energy. This result is inconsistent with the expectation that jets with larger radii will recover more of the energy redistributed to larger angles via jet-medium interactions. However, many models can describe the trend despite including different implementations of physics effects, making it difficult to isolate the impact of a single energy loss mechanism. In this work, we utilize PYTHIA simulations coupled with phenomenologically-derived quenching to better understand the contribution of single effects to this observed $R$-dependence. These effects include the $R$-dependence of the vacuum jet spectrum, differences in energy loss of quark- and gluon-initiated jets, and the impact of wide-angle radiation recovered at large $R$. This work is carried out across RHIC and LHC $p_{\rm T}$-scales, detector acceptances, and center-of-mass energies and compared to experimental data to help interpret experimental results.

Speaker: Ms Zihui Zhang (Colby College)

QM23_Zihui_Zhang.pdf

17:30 Investigation of initial state effects in p+Pb collisions at ATLAS via measurement of centrality dependence of dijet yields

In this poster, we present the ATLAS measurement of the centrality dependence of the dijet per-event yield at center-of-mass energy 8.16 TeV in $p$+Pb collisions. The per-event yield of unfolded dijet pairs is presented in terms of kinematic variables that allow for full characterization of the partonic scattering system, i.e. the average $p_{\mathrm{T}}$ of the dijet, $p_{\mathrm{T,Avg}} = (p_{\mathrm{T,1}} + p_{\mathrm{T,2}})/2$, the boost of the dijet system, $y^{b} = (y^{\mathrm{CM}}_{1} + y^{\mathrm{CN}}_{2})/2$, and the half rapidity separation between the jets, $y^{\ast} = |y^{\mathrm{CM}}_{1} - y^{\mathrm{CM}}_{2}|/2$. Initial state effects are investigated by constructing central-to-peripheral ratios of dijet yields, $R_{\mathrm{CP}}$. We present $R_\mathrm{CP}$ results comparing central collisions with peripheral ones rescaled by the nuclear thickness function $T_{AB}$, in order to equalize the two based on pure geometrical expectations. The $R_\mathrm{CP}$ shows a clear dependence on the Bjorken-$x$ of the parton extracted from the proton in the hard-scattering, $x_\mathrm{p}$, while no clear trend is observed while displaying the results as a function $x_\mathrm{Pb}$. These results will help in understanding the implications introduced by the initial state kinematics in $p$+Pb collisions.

Speaker: Riccardo Longo (Univ. Illinois at Urbana Champaign (US))

QM2023_Poster_Final_Upload.pdf

17:30 Investigation of the Inner Structure of Glueball Candidate Scalar Mesons with the ALICE Detector

High-energy nucleus-nucleus collision experiments have played a crucial role in exploring high-temperature quark matter, such as the quark-gluon plasma (QGP). The study of various hadrons, characterized by diverse internal structures, constituent quark numbers, and quark species, has been essential for understanding QGP properties. It has become increasingly evident that hadron yields in nucleus-nucleus and proton-nucleus collisions exhibit modifications compared to proton-proton collisions, which can be attributed to their internal structures. Therefore, analyzing the yields of hadrons with unidentified internal structures in such collisions can give valuable insights into their composition. Numerous hadrons with unknown internal structures, such as ${\rm f_0}$ mesons (e.g., ${\rm f_0}$(1500) and ${\rm f_0}$(1710), leading glueball candidates), have been observed in the mass range of 1-2 GeV/c$^2$
With its advanced particle identification capabilities, precise secondary vertex determination, and extensive data sample, the ALICE experiment is ideally suited for this study. These features are crucial as these mesons decay into hadrons with relatively long lifetimes, such as the ${\rm K^0_s K^0_s}$ pair. This presentation will showcase the cross-section of hadron production in proton-proton collisions at $\sqrt{s} = 5.02$ TeV and proton-lead collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02$ TeV. The nuclear modification factor, R$_\mathrm{pA}$, will be employed to provide insights into the internal structure of primary glueball candidate hadrons. The findings of this investigation have the potential to open up a new research domain utilizing the QGP, deepening our understanding of the internal structures of exotic hadrons and their roles in high-energy collisions.

Speaker: Satoshi Yano (Hiroshima University (JP))

0905_syano_QM_v4.pdf

17:30 Jet Calibration for Year 1 Data in sPHENIX

The sPHENIX detector at the Relativistic Heavy Ion Collider (RHIC) is designed to study the small scale structure of the quark-gluon plasma (QGP) created in collisions of heavy ions. Jets, produced in hard scatterings early in the collisions, provide an ideal probe for the full evolution of the QGP. sPHENIX is the first detector at RHIC with full coverage electromagnetic and hadronic calorimetry at mid-rapidity up to $|\eta|$ = 1.1, allowing for precise measurements of jet kinematics and physics effects such as jet energy loss. The sPHENIX calorimeter system consists of three sampling calorimeters: a tungsten and scintillating fiber electromagnetic calorimeter, and an aluminum (steel) and scintillating tile inner (outer) hadronic calorimeter. These calorimeters must be calibrated to reconstruct the full electromagnetic and hadronic energy deposited by jets. The jet level calibration combines Monte Carlo-based corrections and data-driven techniques to provide fully calibrated calorimeter jets for measurements of jet quenching in sPHENIX. This poster will present the status and plans for jet calibration using Au+Au data at 200 GeV measured in sPHENIX in 2023.

Speaker: Virginia Bailey (Georgia State University)

VBailey-JetCalibration-qm23-sphenix_v6.pdf

17:30 Jet momentum broadening during initial stages in kinetic theory

The jet quenching parameter $\hat q$ encodes jet medium interactions during the entire quark-gluon plasma evolution in heavy-ion collisions. For a long time, the impact of pre-equilibrium stages has not been properly treated in jet quenching calculations, although recent studies find large values for $\hat q$ in the earliest (glasma) stage. For the first time, we show that QCD kinetic theory smoothly connects these values to the later hydrodynamic ones, providing the missing link for a consistent $\hat q$ evolution. We find that its evolution during the bottom-up kinetic scenario shows little sensitivity to the initial conditions, jet energies and models of the transverse momentum cutoff. We also observe that, similarly to the glasma case, the jet quenching parameter is enhanced along the beam axis as compared to the transverse direction during most of the kinetic evolution. With our results, jet quenching can thus become a promising experimental probe to gain insight into the nonequilibrium properties of the quark-gluon plasma.

Speaker: Florian Lindenbauer (TU Wien)

Poster_quarkmatter2023_lindenbauer.pdf

17:30 Jet Substructure from Calorimeter Towers for Early sPHENIX Measurements

The new sPHENIX detector at Brookhaven’s National Laboratory’s Relativistic Heavy Ion Collider (RHIC) was designed to significantly further the study of the nature of hot nuclear matter. The use of jets as a probe in p+A and A+A collisions allows access to the interaction of the hard-scattered partons with the nuclear environment and is sensitive to a wide range of scales. sPHENIX will use energy deposits in the electromagnetic calorimeter and in the hadronic calorimeter, the first of its kind used for mid-rapidity measurements at RHIC, to reconstruct jets. Measurements of the sub-structure of these jets can be used to study the properties of the Quark Gluon Plasma (QGP) produced during heavy ion collisions. This poster will outline the method used to construct purely calorimetric jets from underlying-event-subtracted calorimeter towers, by first clustering calorimeter towers into anti-k$_T$ R = 0.2 “sub-jets” and then clustering the sub-jets into larger R jets. We will show the status towards jet substructure measurements using this technique in the first year of Au+Au data-taking with sPHENIX.

Speaker: Noah Applegate (Iowa State University)

Jet Substructure from Calorimeter Towers for Early sPHENIX Measurements

17:30 Light Nuclei Production in Au+Au Collisions at √sNN = 14.6 and 19.6 GeV from RHIC BES-II

In high-energy nuclear collisions, the light nuclei production is sensitive to the temperature and density of the system at freeze-out. It is also predicted to be sensitive to local baryon density fluctuations and can be used to probe the QCD phase transition. The second phase of Beam Energy Scan (BES-II) program at RHIC was completed in 2021. The high-statistics data recorded by the STAR experiment provide a unique opportunity to carry out high-precision measurements on the light nuclei production.
In this poster, we will report the results of the centrality and transverse momentum dependence of proton($\mathrm{p}$), deuteron($\mathrm{d}$) and $^{3}\mathrm{He}$ production in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 14.6 and 19.6 GeV measured by the STAR experiment. We will also present the centrality dependence of coalescence parameters ($\mathrm{B_2(d)}$ and $\mathrm{B_{3}(^{3}He)}$) and particle ratios ($\mathrm{N_{d}/N_{p}}$ and $\mathrm{N_{^{3}\mathrm{He}}/N_{p}}$), and discuss their physics implications.

Speaker: Yixuan Jin (Central China Normal University)

QM2023_poster_yxjin_v7.pdf

17:30 MC-EKRT event generator for initializing 3+1 D hydrodynamics

We present a Monte-Carlo implementation of the EKRT initial-state model (MC-EKRT) [1]. Our new MC-EKRT event generator is based on collinearly factorized, dynamically fluctuating pQCD minijet production, supplemented with a saturation conjecture that controls the low-$p_T$ particle production. Previously, the EKRT model has been very successful in describing low-$p_T$ observables at mid-rapidity in heavy-ion collisions at RHIC and LHC energies [2,3]. As novel features, our new MC implementation gives a full 3-dimensional initial state event-by-event, and includes dynamical fluctuations in the saturation and particle production. As a proof of principle study, we average a large set of event-by-event MC-EKRT initial conditions and compute the rapidity and centrality dependence of the charged hadron multiplicities and elliptic flow for the LHC Pb+Pb collisions using 3+1 D viscous fluid dynamical evolution. In particular, we show that global energy conservation and spatial dependence of the nuclear PDFs are essential features to reach a good agreement with the measurements.

[1] M. Kuha, J. Auvinen, K. J. Eskola, H. Hirvonen, Y. Kanakubo, H. Niemi, in preparation
[2] H. Niemi, K. J. Eskola and R. Paatelainen, Phys. Rev. C 93, no.2, 024907 (2016)
[3] H. Hirvonen, K. J. Eskola and H. Niemi, Phys. Rev. C 106, no.4, 044913 (2022)

Speaker: Mikko Kuha (University of Jyväskylä)

QM23_poster_Mikko_Kuha.pdf

17:30 Mean $p_{\rm{T}}$ fluctuations in 3.0 GeV fixed-target collisions from the STAR experiment

The mean $p_{\rm{T}}$ fluctuations in heavy-ion collisions can be related to temperature fluctuations which quantify the specific heat of the system. Any deviations from the Hadron Resonance Gas model as a function of the incident energy can be interpreted as a possible signal of criticality. In this poster we present the first efficiency corrected charged particle event-by-event mean $p_{\rm{T}}$ fluctuations from central Au+Au collisions at $\sqrt{s_{\rm{NN}}}$ = 3 GeV in the STAR experiment. Mean $p_{\rm{T}}$ fluctuations are calculated for different acceptance windows in pseudorapidity and compared with the previous BES-I results at $\sqrt{s_{\rm{NN}}}$ = 19.6, 62.4, 130, and 200 GeV, as well as the results from transport model a t$\sqrt{s_{\rm{NN}}}$ = 3 GeV. We also discuss the effects of primordial protons on the mean pT fluctuations.

Speaker: Rutik Manikandhan (University of Houston)

QM23Posterprint.pdf

17:30 Measurement of $\Xi_{\rm c}^0$ production as a function of multiplicity via hadron decay in pp collisions at $\mathbf{\sqrt{\textit s}}$ = 13 TeV with ALICE

Measurements of the production of heavy-flavour hadrons in proton–proton (pp) collisions provide an important test of quantum chromodynamics (QCD).The heavy-flavour production cross section can be calculated using the factorisation approach as a convolution of three factors: the parton distribution functions, the partonic cross section, calculated with perturbative QCD calculations, and the fragmentation functions. Recent measurements of the baryon-to-meson (${\Lambda^+_{\rm{c}}/\rm{D}^0}$, ${{\Sigma^{0,++}_{\rm{c}}}/\rm{D}^0}$, ${\Xi^{0,+}_{\rm{c}}/\rm{D}^0}$ and ${\rm{BR\times\Omega^0_c/{D}^0}}$) ${p_{\rm{T}}}$-differential yield ratios in pp collisions are inconsistent with corresponding measurements in $\rm{e^+e^-}$ collision, indicating that the hadronisation of charm quarks is not a universal process among different collision systems. From measurements of the ${p_{\rm{T}}}$-differential ${\rm{\Lambda^+_c/D^0}}$ yield ratio as a function of the event multiplicity in pp collisions, the modificaion of the hadronisation mechanism is found to be multiplicity dependent. The measurement of the multiplicity dependence of the ${\rm{\Xi^0_c/\rm{D}^0}}$ yield ratio can provide further constraints on the study of charm hadronisation.

In this contribution, the production cross section of ${\rm{\Xi^0_c}}$ baryon reconstructed from the hadronic decay channel $\rm{\Xi_{c}^{0}}\rightarrow{\Xi^{-}\pi^{+}}$ and the baryon-to-meson yield ratio $\rm{\Xi^0_c/\rm{D}^0}$ as a function of charged-particle multiplicity in pp collisions at ${\sqrt{\textit s}}$ = 13 TeV at midrapidity with the ALICE detector at the LHC will be discussed.

Speaker: Tao Fang (Central China Normal University CCNU (CN))

2023-08-31-Poster_20230831_V10.pdf

17:30 Measurement of $\mathrm{\Lambda_c^+/D^0}$ as a function of event multiplicity in pp and p–Pb collisions $\sqrt{s_{\rm NN}}=5.02\ \mathrm{TeV}$ with the ALICE experiment

Measurements of charm baryon and meson production in pp and p–Pb minimum bias collisions and as a function of multiplicity, help to investigate hadronization processes and to study their modification across the collision systems from pp to Pb–Pb, and from low to high multiplicities.
Recent measurements of the fragmentation fractions of charm hadrons in pp and p–Pb challenge the universality of fragmentation in the presence of a hadronic medium. In addition, the ratio of $p_\mathrm{T}$ spectra of $\mathrm{\Lambda_c^+/D^0}$ in pp collisions, shows a separation between the highest and the lowest multiplicity classes within $5.3\sigma$, with the maximum discrepancy occurring for $2\ \mathrm{GeV}/c

Speaker: Oveis Sheibani (University of Houston (US))

17:30 Measurement of $\mathrm{D^0-{\bar{D}} ^{0}}$ azimuthal correlations and femtoscopic correlations of D mesons with identified hadrons in Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV at STAR

Heavy quarks are produced at the very early stage of heavy-ion collisions, and they experience the whole evolution of the Quark-Gluon Plasma (QGP) created in these collisions. Measurements of the elliptic flow and nuclear modification factor of charmed mesons in heavy-ion collisions at RHIC and the LHC provide ample evidence of strong interactions between charm quarks and the QGP. However, a complete understanding of the nature of the charm-medium interaction is yet to be achieved. Thus, new observables are needed to constrain theoretical models and the charm quark diffusion coefficient in the QGP.

Measurements of azimuthal and femtoscopic correlations involving charmed mesons can provide such new insights. Azimuthal correlations of charmed mesons can help to pin down the relative role of radiative and collisional energy losses for charm quarks. On the other hand, femtoscopic correlations, i.e., two-particle correlations at the low relative momentum, are sensitive to the final-state interactions and the extent of the region from which correlated particles are emitted. Therefore, a study of femtoscopic correlations between charmed mesons and identified charged hadrons could shed light on their interactions in the hadronic phase and the interaction of charm quarks with the bulk partons.

We will present the azimuthal correlations of $\mathrm{D^0-{\bar{D}} ^{0}}$ pairs and femtoscopic correlations of charmed mesons with identified hadrons measured by the STAR experiment at mid-rapidity in Au+Au collisions at $\mathrm{\sqrt{s_{NN}} = 200}$ GeV using high-statistics data collected in 2014 and 2016. We will compare the experimental results with available theoretical model predictions and discuss their physics implications.

Speaker: Katarzyna Gwizdziel (Warsaw University of Technology (PL))

17:30 Measurement of $\omega$ meson production in pp and p--Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02~$TeV with ALICE

By comparing the particle production in pp and p--Pb collisions, nuclear initial state effects can be studied. Measurements of the $\omega$ meson $p_\text{T}$-spectra in pp and p--Pb collisions not only allow for a determination of the nuclear modification factor $R_\text{pA}$, but also provide insight into the fragmentation process and serve as vital input for direct-photon cocktail simulations.

The $\omega$ mesons can be reconstructed in ALICE via their primary decay channel into three pions ($\omega\rightarrow\pi^+\pi^-\pi^0$). While the two charged pions are being directly identified with the tracking detectors, i.e. the Time Projection Chamber and the Inner Tracking System, the $\pi^0$ is reconstructed from its two decay photons. These photons can either be detected in the calorimeters or via tracks in case they convert to an electron-positron pair in the detector material.

In this poster, measurements of the $\omega$ meson production in pp and p--Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02~$TeV will be presented. This includes the signal extraction and various corrections of the $\omega$ meson yields, leading to their production cross sections and the first measured nuclear modification factor $R_\text{pA}$ ($2.2\leq p_\text{T}<16~$GeV/$c$) of the $\omega$ meson at LHC energies.

Speaker: Nicolas Strangmann (Goethe University Frankfurt (DE))

Poster_5TeVOmega_QM.pdf

17:30 Measurement of $\rm D^{0}$ Meson Tagged Jets in Au+Au Collisions at $\sqrt{s_{\rm NN}} = 200$ GeV at STAR

The properties of the Quark-Gluon Plasma (QGP) produced in heavy-ion collisions can be studied using jets generated in hard scattering processes at the early stages of the collision. These jets lose energy and have their shower structures modified relative to that in the vacuum due to jet-medium interaction — known as `jet quenching'.

The transverse momentum ($p_{\rm T}$) fraction of the jet carried by hadrons along the jet axis ($z = \vec{p}_{\rm T, hadron}\textbf{.}\hat{p}_{\rm T, jet}/|\vec{p}_{\rm T, jet}|$) is related to the jet fragmentation function, and connects the production of quarks and gluons in the perturbative regime with the hadronized final-state particles in the non-perturbative regime. In the QGP medium, modifications to the fragmentation function compared to that in a vacuum can provide insights into the underlying mechanism of jet quenching. A study of the fragmentation function for charm meson tagged jets can reveal further details about the flavor dependence of the medium-induced parton energy loss.

In this poster, we report measurements of $\rm D^{0}$ meson tagged jets in Au+Au collisions at $\sqrt{s_{\text{NN}}} = 200 \text{ GeV}$, collected by the STAR experiment at RHIC. We show the nuclear modification factors as a function of $p_{\rm T, jet}$ and $z$ for $\rm D^{0}$ jets. Additionally, we report the radial profile of the $\rm D^{0}$ mesons in these tagged jets. Such flavor tagged measurements can help to discriminate between different models of jet quenching in the medium and study the properties of the QGP.

Speaker: Mr Diptanil Roy (Rutgers University)

QM2023_Poster_Diptanil_Roy.pdf

17:30 Measurement of $\Xi_{c}^{0}$ via semileptonic decay in collisions of pp at 13 TeV and p-Pb at 5.02 TeV with ALICE

Compared to $\rm{e^+e^-}$ and ep collisions, the charm baryon production in pp collisions shows a substantial enhancement. This evidence is currently interpreted in terms of a modification of the hadronization mechanisms in hadronic collisions. Therefore, valuable information on how the charm quarks hadronize can be studied by measuring charm baryon production. In addition, by sorting out the produced baryons by the multiplicity of the event, further information such as the multiplicity dependence of the hadronization process can be assessed. In this study, we report the status of the analysis of the $\Xi_{\rm c}^{0}$ $\rightarrow$ $\Xi^{-} e^{+} \nu_{e}$ (and its charge conjugate) baryon by using the LHC Run 2 data collected with ALICE detectors. The measurement of baryon-to-meson ($\Xi_{\rm c}^{0}$/${\rm{D}^{0}}$) yield ratio as a function of the event multiplicity in pp collisions at $\sqrt{s}=13~\mathrm{TeV}$ and the nuclear modification factor ($R_{\rm pPb}$) in p--Pb collisions at $\sqrt{s_{\rm NN}}= 5.02$ TeV, respectively, will be shown.

Speaker: Chong Kim (Pusan National University (KR))

Xic0_QM23_v4.pdf

17:30 Measurement of $J/\psi$ polarization in Ru+Ru and Zr+Zr collisions at $\sqrt{s_{NN}} = 200$ GeV at STAR

$J/\psi$ serves as an important probe to study the properties of the quark-gluon plasma (QGP) created in heavy-ion collisions. In Ru+Ru and Zr+Zr collisions at $\sqrt{s_{NN}} = 200$ GeV, it has been observed that the $J/\psi$ yield is strongly suppressed and its elliptic flow ($v_{2}$) is consistent with zero, indicating $J/\psi$'s strong coupling with the medium and its potentially small regeneration contribution. Besides those measurements, the $J/\psi$ polarization can shed new light on the QGP properties and the $J/\psi$ production mechanism in heavy-ion collisions. For example, it has been hypothesized that $J/\psi$ can be polarized due to the spin-orbit coupling between $J/\psi$ and QGP's large angular momentum in non-central heavy-ion collisions. The early production of $J/\psi$ also makes its polarization potentially sensitive to the strong magnetic field at the early stage.
In this poster, we will present the first measurement of $J/\psi$ polarization in heavy-ion collisions at RHIC. The $J/\psi$ polarization in the Helicity frame and Collins-Soper frame, as well as with respect to the event-plane, in Ru+Ru and Zr+Zr collisions at $\sqrt{s_{NN}} = 200$ GeV will be presented, and its physics implications will be discussed.

Speaker: Dandan Shen (Shandong University)

QuarkMatter_225_Dandan.pdf

17:30 Measurement of $K_{s}^{0}-K_{s}^{0}$ correlation function in Au+Au collisions at the high baryon density region

Two-particle correlation analyses are often used to study the spatial and temporal extension of particle-emitting source in high-energy nuclear collisions. Precise information on the final state interactions amongst the particles under study can also be extracted from the measurement. It is particularly interesting to study the energy dependence of the extracted source size at the moment of freeze-out. Two-kaon correlations are an important supplement to those of pions, as they are less affected by resonance decays and they have smaller hadronic cross-section.

In this poster, the measurements of $K_{s}^{0}-K_{s}^{0}$ correlations in Au+Au collisions with the fixed-target mode at $\sqrt{s_{NN}}$ = 3.0, 3.2, 3.5, and 3.9 GeV, by the STAR experiment will be presented. This presents the first measurements of the systematic study on femtoscopic correlations involving strangeness at the high baryon density region. The energy dependence of particle-emitting source parameters will be compared with transport model calculations.

Speaker: Mr Li'Ang Zhang (Central ChinaNormal University (CCNU))

QM2023_poster_LiAngZhang_v5.pdf

17:30 Measurement of directed flow of inclusive jets in heavy-ion collisions at RHIC

Jets are collimated sprays of hadrons fragmented by highly virtual partons produced in the early stage of heavy-ion collisions via hard scatterings. Different observables of the jet-medium interaction probe the properties of the Quark-Gluon Plasma and its dynamics. The bulk medium produced in non-central heavy-ion collisions is expected to be tilted with respect to the beam axis, while the hard scatterings are symmetric along the rapidity. This asymmetry between hard and soft processes coupled with in-medium interactions can induce a large rapidity-odd directed flow ($v_1$) for jets. In fact, it has been observed that the $D^0$ mesons show a significantly larger $v_1$ signal as a function of rapidity compared to charged hadrons at the top-RHIC energy, reflecting the interplay between soft and hard processes.

In this poster, we report the first measurement of inclusive jets $v_{1}$ in isobar (Ru+Ru and Zr+Zr) and Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 200 GeV. Inclusive jets are reconstructed using the anti-$k_{T}$ algorithm with a hard-core selection to suppress the combinatorial background. The jet $v_1$ is presented as a function of rapidity and transverse momentum in these collision systems. Finally, we discuss the implications of these results on the jet-medium interaction in a tilted bulk medium.

Speaker: Dr Subhash Singha (Institute of Modern Physics CAS)

17:30 Measurement of heavy-flavor electron production in Au+Au collisions at $\sqrt{s_{NN}}$ = 54.4 GeV at STAR

Studying heavy flavor can enhance our comprehension of parton interactions with the Quark-Gluon Plasma (QGP). Due to their significant mass, heavy quarks (charm and bottom) are mainly generated during the initial phase of high-energy heavy-ion collisions when hard scatterings are prevalent, and experience the entire evolution of the QGP. One way to study the production of heavy quarks is through the measurement of Heavy Flavor Electrons (HFE) - electrons emitted from the semi-leptonic decays of heavy-flavor hadrons.

In this contribution, we will present measurements of HFE at low transverse momentum ($p_{\rm{T}}$) in Au+Au collisions at $\sqrt{s_{NN}}$ = 54.4 GeV using data taken in 2017 by the STAR experiment. We will show the yields and central-to-peripheral nuclear modification factors as functions of $p_{\rm{T}}$ and centrality.

Speaker: Mrs Veronika Prozorova (Czech Technical University in Prague)

PosterQM23_Prozorova_final.pdf

17:30 Measurement of light neutral meson production inside jets in pp collisions at $\sqrt{s}$ = 13 TeV with ALICE

Particle production in ultra-relativistic pp collisions can be factorized into the parton density function (PDF), the partonic cross-section and the fragmentation function (FF). FFs need to be constrained by experimental data for each particle species. Measurements of the momentum fraction $z$ of a particle species contained in a high energetic jet give direct access to the FF of the species.

In this poster, the first measurement of the $p_{\rm T}$ spectra of $\pi^{0}$ and $\eta$ mesons inside jets, as well as the measurement of the meson momentum fraction $z$ for different jet momenta up to $p_{\rm T}$ = 200 GeV/$c$ in pp collisions at $\sqrt{s}$ = 13 TeV with ALICE will be presented. The measurement combines results from several partially independent meson reconstruction techniques available in ALICE, including calorimeter based photon detection as well as utilizing photon conversions in the central tracking detectors. The combined meson spectra cover nearly the entire $z$ range for a large span of jet momenta. Particle jets are reconstructed using charged tracks in the central tracking detectors and neutral clusters reconstructed with the electromagnetic calorimeter. The results will be compared to model predictions.

Speaker: Joshua Leon Konig (Goethe University Frankfurt (DE))

Poster_NeutralMesons_QM_2023_JoshuaKoenig.pdf

17:30 Measurement of non-prompt D-mesons production in pp collisions at √s = 13 TeV using Machine Learning (ML) techniques with ALICE

The production of hadrons containing charm or beauty quarks in pp collisions provides an important test for quantum chromodynamics calculations. These measurements also serve as reference for more complex systems such as Pb--Pb collisions, helping to characterize the various in-medium partonic energy loss mechanisms and their dependence on the quark mass.
The excellent particle identification, track and decay-vertex reconstruction capabilities of the ALICE experiment, together with machine-learning techniques for multi-class classification, are exploited to separate the non-prompt D mesons from the prompt ones. The precise measurements of non-prompt D-mesons production, in particular, allow us to investigate the production of beauty quarks in pp collisions. In this contribution, the latest results of the ALICE Collaboration on the measurement of non-prompt D mesons with Machine-Learning techniques will be presented. The results will also be compared with various theoretical models.

Speaker: Renu Bala (University of Jammu (IN))

2023-08-31-QM_2023_Renu_new.pdf

17:30 Measurement of the $\Upsilon$ production in heavy-ion collisions at $\sqrt{s_{\rm NN}}$ = 200 GeV with the STAR detector

Quarkonia play a unique role in probing the properties of the quark-gluon plasma (QGP). The dissociation of quarkonia due to the color screening was proposed as a direct signature of the QGP formation. On top of that, different states of quarkonium are expected to dissociate at different temperatures depending on their binding energies. Therefore, measurement of the expected sequential suppression for the three $\Upsilon$ states in heavy-ion collisions can be used to study the modification of the QCD force in the medium and the QGP’s thermodynamic properties.

This poster presents the $\Upsilon$ measurements in Au+Au and isobar (Ru+Ru and Zr+Zr) collisions at $\sqrt{s_{\rm NN}}$ = 200 GeV with the STAR experiment at RHIC. The nuclear modification factors are presented as functions of centrality and transverse momentum. In addition, these results are compared to those at the LHC and theoretical calculations. The physics implications are discussed as well.

Speaker: Shuai Yang (South China Normal University)

17:30 Measurement of the mass spectrum of vector mesons in nuclei at J-PARC

The mass spectrum of hadrons in finite-density QCD matter is believed to reveal the effects of partial chiral symmetry restoration. However, despite the importance of understanding QCD at finite density, decisive evidence linking the mass spectrum and chiral symmetry is still lacking.
The J-PARC E16 experiment aims to fill this gap with high-statistics measurements of vector mesons ($\rho$, $\omega$, $\phi$) in nuclei. The experiment will measure the momenta of electron-positron pairs from vector meson decays and reconstruct their invariant mass.

To obtain large statistics,
we use a new beamline at J-PARC that provides $30\,\rm{GeV}$-proton beams with an intensity of $1 \times 10^{10}$ protons/spill.
The maximum hit rate reaches $15\,\rm{kHz/mm^2}$ and $5\,\rm{kHz/mm^2}$ at two innermost detectors, necessitating an innovative spectrometer for high-rate environments.

Since the experiment commenced in 2020, three commissioning runs have been conducted
with a limited number of detectors.
Partial results were reported at QM2022.
The next run, scheduled for June 2023, aims to improve beam microstructures
detected in the last run.
Eight modules of detectors will be operated, as proposed for the first physics run.
In the commissioning runs so far,
our detectors were successfully operated under the high-counting environment.
Tracking is performed using a layer of the Silicon Strip Detector and three layers of thin gas chambers with different sizes, all employing the Gas Electron Multiplier (GEM).
Calibration is ongoing, but the current tracking resolution is sufficient to observe changes in the mass spectrum of vector mesons.
For the $\phi$ mesons, we anticipate a mass resolution of $5.8\,\rm{MeV/c^2}$, while a mass change of $35\,\rm{MeV/c^2}$ was observed in the preceding experiment, KEK-PS E325.
Electron identification is carried out using the Hadron Blind Detector and the Lead Glass Calorimeter installed outside the trackers.
We achieved electron efficiency and pion rejection power consistent with the design values, at $57\%$ and $99.97\%$ , respectively.

In this presentation, we will report the result of the run in June, including the detector performance
and improvement of the beam microstructure, and discuss
the anticipated outcomes for the physics run planned in 2024.
In the physics run, we aim to collect 15000 phi mesons, representing six-fold
improvement compared to the KEK-PS E325 experiment.

Speaker: Tomoki Murakami

QM23_poster_vf.pdf

17:30 Measurement of the multiplicity dependence of $\Upsilon$ meson production in $p$+$p$ collisions at $\sqrt{s}$ = 510 GeV

Measurements of $\Upsilon$ meson production in heavy-ion collisions allow the study of the properties of the quark-gluon plasma, such as in-medium modifications to the QCD force and the medium's thermodynamic properties. However, the quarkonium production mechanism is not completely understood even in vacuum, which is of great interest on its own and could also have significant consequences for interpreting $\Upsilon$ measurements in heavy-ion collisions.

In this poster, we present the latest measurements of $\Upsilon$ meson production via the dielectron channel in $p$+$p$ collisions at $\sqrt{s}$ = 510 GeV recorded by the STAR experiment in 2017. The transverse momentum and rapidity spectra of three $\Upsilon$ states combined will be shown. We will also measure the dependence of self-normalised $\Upsilon$ meson yield on self-normalised charged particle multiplicity to probe the interplay between soft and hard processes. The presented analysis utilises a data sample with a significant increase in statistics compared to previous measurements, which results in improved precision and extended multiplicity reach.

Speaker: Jakub Ceska

QM23_poster_552_Ceska.pdf

17:30 Measurement of the transverse momentum($j_\mathrm{T}$) distributions of charged-particle jet fragments in pp collisions at $\sqrt{s}$ = 5.02 TeV with ALICE

Measurement of the jet substructure and the distribution of final state hadrons within a jet provide a detailed look into both the partonic shower and hadronisation process. These processes can be studied using the transverse momentum ($j_\mathrm{T}$) and longitudinal momentum fraction ($z$) of constituent particles. ALICE has recently measured the transverse momentum distributions of the jet fragments in proton-proton and proton-lead collisions at $\sqrt{s_{NN}}$ = 5.02 TeV with ALICE. Various parton-shower models were shown to reasonably describe the pp results. We now extend this analysis to more detailed measurements of the $j_\mathrm{T}$ distributions for charged-particle jets in pp collisions, in several $z$ ranges. The $z$-dependent $j_\mathrm{T}$ distributions are compared with the theoretical predictions to test our current understanding of jet fragmentation.

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

QMPoster_Jet_JRyu_v3.pdf

17:30 Measurements of $\Omega$ and $\bar{\Omega}$ production in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV with the STAR experiment

$\Omega$($\bar{\Omega}$), composed of three strange quarks, serves as a sensitive probe into the characteristics of the quark-gluon plasma (QGP). Measurement of its production can be used to extract the temperature and baryon chemical potential at the chemical freeze-out with the statistical hadronization model, providing information on the QCD phase diagram. Also, the $\Omega$/$\phi$ ratio as a function of transverse momentum ($p_T$) can be utilized to test hadronization model predictions and to possibly extract the strange quark $p_T$ distribution at hadronization.

In this poster, we will present $p_T$ spectra and yields of $\Omega$($\bar{\Omega}$) in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV. The data analyzed were collected by STAR in 2019, when the iTPC was in operation. The iTPC extends the rapidity coverage and enhances the particle identification capability compared to previous results.

Speaker: Xiongxiong Xu

17:30 Measurements of $\pi$, K, and p in jets in Pb--Pb collisions at $\sqrt{s_{\rm{NN}}} = 5.02$ TeV with ALICE

Energetic partons lose energy in the quark-gluon plasma (QGP) and then fragment and hadronize into showers of particles called jets. Measurements of the internal structure of these jets can constrain how energetic partons interact with the QGP. Though species-independent jet substructure measurements have made much progress recently, a complete understanding of the identified particle composition of the jet and its energy loss remains elusive. It has been predicted that the jet hadrochemical composition may be modified in Pb--Pb collisions due to jet-medium interactions and modified particle composition in the jet wake. Measurements of identified particles in jets can help discriminate between these potential parton-QGP interactions. In this poster, we will present progress towards extracting momentum-dependent $\pi$, K, and p ratios within jets and in the underlying event in Pb--Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 5.02 TeV using $\rm{d}E/\rm{d}x$ measurements from the ALICE Time Projection Chamber. This study aims at disentangling the potential effects of modified jet fragmentation in the medium from bulk effects.

Speaker: Sierra Lisa Weyhmiller (Yale University (US))

Weyhmiller_QM2023_Poster_FINAL.pdf

17:30 Measurements of (anti)nuclei in pp collision at √s = 13.6 TeV

The ALICE detector at the CERN LHC is particularly suited to study light (anti)nuclei produced in high-energy collisions between hadrons. The formation mechanism of (anti)nuclei in these collisions is still one fundamental open question that is being addressed both theoretically and experimentally. This mechanism is investigated by comparing experimental data with phenomenological models such as statistical hadronization and coalescence. The latest has important applications, especially in cosmic antinuclei studies for indirect dark matter searches.

The ALICE apparatus underwent a series of major upgrades during the LHC long shutdown 2 to benefit from the luminosity increase of LHC Run 3. These upgrades allow the measurement of (anti)nuclei, such as (anti)deuterons and (anti)He-3, with unprecedented precision.

In this poster the first analysis on (anti)nuclei production at mid-rapidity (|𝜂|<0.8) in √s = 13.6 TeV pp collisions collected during the 2022 data taking campaign with the upgraded detector will be presented.

Speaker: Giovanni Malfattore (University of Bologna and INFN, Bologna (IT))

[POSTER] QM - Malfattore - Final.pdf

17:30 Measurements of azimuthal anisotropy of charged particles in Pb+Pb collisions with the ATLAS detector

The initial QGP geometry of the quark-gluon plasma (QGP) is manifested as azimuthal anisotropy in final state particles of a nuclear collision in the plane transverse to the beam direction. This study measures the Fourier coefficients $v_{2}$ and higher order harmonics of charged particle distribution in Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV with 2018 data collected by the ATLAS experiment. The measurements utilize the scalar product method and multiparticle cumulants method to probe momentum dependence of response to initial-state fluctuations. With improved statistics, the 2018 data provides an opportunity to explore higher momentum regimes and higher order harmonics than current measurements and a deeper understanding of the role of fluctuations. The results are compared with existing measurements for charged particles and jets and will provide new information about the path length dependence of jet quenching.

Speaker: Xiaoning Wang (Univ. Illinois at Urbana Champaign (US))

QM23 (4)-2.pdf

17:30 Measurements of baryon-antibaryon and meson-antimeson pairs from QED vacuum excitation in Au+Au ultra-peripheral collisions at $\sqrt{s_{\rm{NN}}} = $ 200 GeV from STAR

Relativistic heavy-ion collisions generate extremely strong electromagnetic fields, providing an ideal environment to study the electromagnetic excitation of the vacuum. Furthermore, the electromagnetic fields are sensitive to the charge distributions of the colliding nuclei which can be used to study the nuclear structure. The Breit-Wheeler process, the lowest-order decay mode of the QED vacuum excitation into electron-positron pairs, has been experimentally verified by the STAR collaboration, stimulating further investigations of higher-order decay modes, such as baryon-antibaryon and meson-antimeson pairs.

This presentation reports on the new measurements of baryon-antibaryon and meson-antimeson pairs from QED vacuum excitation in Au+Au ultra-peripheral collisions at $\sqrt{s_{\rm{NN}}} = $ 200 GeV by the STAR experiment. The invariant mass and $p_\rm{T}$ distributions for the pair production will be shown, and the azimuthal angular modulation caused by the polarization of the electromagnetic field will be discussed. These measurements will shed new lights on the understanding of the QED vacuum and nuclear structure.

Speaker: Xin Wu (University of Science and Technology of China)

17:30 Measurements of harmonic flow and their fluctuations in $^{16}$O+$^{16}$O collisions at $\sqrt{s_{_{\mathrm{NN}}}}=200$ GeV from STAR

The study of the Quark-Gluon Plasma (QGP) properties is a fundamental aspect of high-energy nuclear physics. However, the understanding of QGP formation and evolution is still limited by various uncertainties in the initial stages of the collision. One approach to gain more insights into the initial stages is to study small-sized systems, which, due to their reduced system size and lifetime, may provide a better understanding of the possible formation and evolution of QGP. The recently reconstructed data from minimum bias and central triggered $^{16}$O+$^{16}$O collisions at 200 GeV from STAR provide an exciting opportunity to investigate the initial stages of the small system and gain more insights into the formation and evolution of the QGP. In this poster, we present the measurement of $v_n$ and its fluctuations as a function of $p_{\mathrm{T}}$, multiplicity, and rapidity in O+O collisions. The results are compared with hydrodynamic and transport model calculations to discuss the physics implications in terms of the initial condition and the emergence of collectivity in small systems.

Speaker: Zhengxi Yan

QM2023_poster_oo_flow_zhengxi_yan_v9.pdf

17:30 Measurements of Hypernuclei Production and Their Properties in Heavy-Ion Collisions at STAR

Hypernuclei, bound states of nuclei with one or more hyperons, serve as a natural laboratory to investigate the hyperon-nucleon ($Y$-$N$) interaction, an important ingredient for the equation-of-state (EoS) of nuclear matter. Precise measurements of hypernuclei properties and their production yields in heavy-ion collisions are crucial for the understanding of their production mechanisms and the strength of the $Y$-$N$ interaction. The strangeness population factor, $S_{\rm A}=(^{A}_{\Lambda}\mathrm{H}/^{A}\mathrm{He})/(\Lambda/p)$ (A=3,4), is of particular interest as it directly relates to the ratio of light nuclei and hypernuclei coalescence parameters $B_{A}$. Moreover, it is suggested that $S_{A}$ might be sensitive to the onset of deconfinement. The STAR Beam Energy Scan II program and isobar collisions offer a great opportunity to investigate energy and system size dependence of hypernuclei production.

In this talk, we present new measurements on transverse momentum ($p_T$), rapidity\,($y$), and centrality dependence of $\rm ^{3}_{\Lambda}H$, $\rm ^{4}_{\Lambda}H$, and $\rm ^{4}_{\Lambda}He$ production yields in Au+Au collisions from $\sqrt{s_{\rm NN}}=$ 3 to 27 GeV, as well as in Ru+Ru and Zr+Zr collisions at $\sqrt{s_{\rm NN}}=200$ GeV. Strangeness population factors $S_{3,4}$ as functions of collision energy, centrality, $p_T$, and $y$ are also reported. In addition, we present new measurements on $\rm {}^{4}_{\Lambda}He$ and $\rm {}^{5}_{\Lambda}He$ lifetimes. These results are compared with phenomenological model calculations, and the physics implications on the hypernuclei production mechanism and properties of $Y$-$N$ interaction will be discussed.

Speaker: Xiujun Li (USTC)

QM2023_posterv4.pdf

17:30 Measurements of inclusive J/$\psi$ and $\psi$(2S) production at midrapidity in pp collisions at $\sqrt{s}$ = 13.6 TeV with ALICE

Quarkonium production in high-energy proton-proton (pp) collisions is an important tool for studying perturbative and non-perturbative aspects of quantum chromodynamics (QCD) calculations. Charmonia are bound states of charm and anti-charm quark pairs. Their production process can be factorized into two stages: the heavy quark production and the formation of the bound state. The former happens within initial hard parton-parton scatterings with large momentum transfers, and can be well described by perturbative QCD. The second one, which involves long distances and soft momentum scales, is a typical non-perturbative process. Measurements of J/$\psi$ and $\psi$(2S) cross section in pp collisions are crucial for studying charmonium production mechanisms and testing different QCD-based model calculations. They can also provide a reference for investigating the quark-gluon plasma formed in nucleus-nucleus collisions and the cold nuclear matter effects present in proton-nucleus collisions.

In this poster, we will present the performance and the analysis status of inclusive J/$\psi$ and $\psi$(2S) production at midrapidity ($|y|<0.9$) in pp collisions at the center-of-mass energy of $\sqrt{s}$ = 13.6 TeV. The analysis is based on the data collected in 2022 by the upgraded ALICE detector during the Run 3 of LHC, which offers significantly higher statistics compared to previous runs. The $p_{\rm T}$-differential production of inclusive J/$\psi$ and $\psi$(2S), as well as the $\psi$(2S)-to-J/$\psi$ ratio, might be reported. Results will be shown along with similar existing measurements based on data collected during the Run 2 of LHC.

Speaker: Yuan Zhang (University of Science and Technology of China (CN))

2023-09-02-QMposter_2023_v7.pdf

17:30 Measurements of jet $v_{2}$ in medium-sized systems at STAR

Hard partonic scatterings, occurring at the early stages of heavy-ion collisions, produce jets, which experience the full evolution of the quark-gluon plasma (QGP). As they traverse through the QGP, jets lose energy through collisional and radiative processes, collectively known as the jet quenching. In semi-central heavy-ion events, the QGP takes an approximately elliptical shape in the transverse plane whose mean in-plane and out-of-plane distances differ. This fact can be used to vary the average path length for jets traversing the QGP, and those traveling in-plane should experience less quenching effects than those traveling out-of-plane. This differential quenching manifests as a suppression of jet yield out-of-plane relative to in-plane, quantified by jet $v_2$, the second order Fourier coefficient. In this poster, jet $v_2$ will be presented from Ru+Ru, Zr+Zr, and O+O collisions at $\sqrt{s_{\rm{NN}}}=200\hbox{ GeV}$ with multiple jet resolution parameters. Studying jet $v_{2}$ in collision systems of varying sizes may help disentangle path-length dependent quenching effects and other effects which could give rise to anisotropies in systems even smaller than O+O collisions.

Speaker: Tristan Protzman (Lehigh University)

Protzman_QM23_Poster_Final.pdf

17:30 Measurements of long-range two-particle correlation over a wide pseudorapidity range in p--Pb collisions at 5.02 TeV

Measurements of long-range angular correlations are one of the important tools to evaluate the interplay between the initial- and final-state effects in small collision systems in view of understanding the evidence of collectivity.
The charged-particle multiplicity distribution as a function of pseudorapidity ($\eta$) is asymmetric in p--Pb collisions. Since the mean free path depends on multiplicity, the $v_{n}(\eta)$ reflects the dynamics of collectivity in p--Pb collisions. The measurement of $v_{n}(\eta)$ in p--Pb collisions is an important study of how charged-particle multiplicity and anisotropic flow relate to the longitudinal evolution of the system. In this poster, we present new final results of $v_{2}(\eta)$ extracted from long-range two-particle azimuthal correlations in p--Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV measured with ALICE. These measurements utilize the Forward Multiplicity Detector, which allows for unprecedented pseudorapidity ranges to be explored (up to $\Delta\eta\sim$ 8) and allow to measure the $\eta$ dependence of $v_{2}$ over a wide pseudorapidity range (−3.1 $< \eta<$ 4.8). Results are compared with the AMPT and hydrodynamical calculations.

Speaker: Yuko Sekiguchi (University of Tokyo (JP))

QM23_yuko_final.pdf

17:30 Measurements of neutral pions and direct photons in 3He+Au collisions

As a part of the studies of the small systems ($p$, $d$, and $^3\text{He}+\text{Au}$), in this poster we present the preliminary yields of $\pi^0$ and direct $\gamma$ for the $\sqrt{s_{NN}}=200$ GeV $^3\text{He}+\text{Au}$ PHENIX data, as well preliminary nuclear modification factor ($R_{xA}$) for this system. We will discuss the unfolding procedure to obtain such yields from raw data in a way to account for $p_T$ migration as well as correct for detector acceptance and efficiency. For the nuclear modification factor, we employ the double ratio $R_{xA}=(\gamma^{dir}/\pi^0)_{pp}/(\gamma^{dir}/\pi^0)_{xA}$ which can be shown to be analytically equivalent to the regular expression for $R_{xA}$, but using an experimentally determined metric for the number of binary collisions ($N_{coll}^{exp}=\gamma_{xA}^{dir}/\gamma_{pp}^{dir}$). As we will show, using this ratio has the advantage of canceling systematic uncertainties that are present in both $p+p$ and $^3\text{He}+\text{Au}$ collisions (such as the reduced production of high $p_T$ pions and $\gamma^{dir}$ due to cold nuclear matter effects and uncertainties due to the $p+p$ cross section), as well as detaching the nuclear modification factor from the Glauber model, thus minimizing biases on centrality determination which are particularly relevant for the studies of small systems.

Speaker: Daniel Firak

17:30 Measurements of proton-$\Lambda$ and proton-$\Xi^-$ Correlation Functions in Au+Au Collisions from STAR Fixed-Target Experiment

Two-particle correlation analyses are often used to study the spatial and temporal extents of the particle-emitting source in high-energy nuclear collisions. Information on the final state interactions amongst the particles under study can also be extracted from the measurement. For example, from the p-$\Lambda$ and p-$\Xi^-$ correlation functions, one could study the hyperon-nucleon (Y-N) interactions in such collisions. It is particularly interesting to study the dependence on the collision energy of the source size at the moment of freeze-out. The STAR fixed-target program from $\sqrt{s_{\rm NN}}=3.0$ to 7.7 GeV has enabled us to investigate the high baryon density region from $\mu_{\rm B}$ = 420 to 750 MeV.

In this poster, the first measurements of p-$\Lambda$ and p-$\Xi^-$ correlation functions in Au + Au collisions at $\sqrt{s_{\rm NN}}=3.2$, 3.5, and 3.9 GeV with the fixed-target mode from STAR will be presented. The results will be compared with the data from $\sqrt{s_{\rm NN}}=3$ GeV Au + Au collisions ($\mu_{\rm B}$ = 750 MeV) and the data from higher energies [1, 2], where $\mu_{\rm B}$ is close to 0, along with model calculations generated via the UrQMD hadronic transport model and CRAB afterburner.

References

[1] STAR, Phys. Rev. C 74, 064001 (2006)

[2] ALICE, Nature 588, 232–238 (2020)

Speaker: Jing An (Central China Normal University)

17:30 Measurements of two-pion femtoscopy in Au+Au Collisions at $\sqrt{s_{\mathrm{NN}}}$ = 3.0, 3.2, 3.5, and 3.9 GeV from RHIC-STAR

Femtoscopic measurements are sensitive to the spatial and temporal characteristics of the particle emitting-source, allowing us to probe the properties of the matter created in heavy-ion collisions. If QCD transition takes place, the time scale for pion emission is expected to increase significantly. Therefore, it will help us understand the properties of the QGP and the nature of the QCD phase transition.

In this poster, we report the results on two-pion femtoscopy measurements in Au+Au collisions at $\sqrt{s_\mathrm{NN}}$ = 3.0, 3.2, 3.5, and 3.9 GeV measured by the STAR experiment. The extracted correlation strength ($\lambda$) and HBT radii ($R_{\mathrm{out}}, R_{\mathrm{side}}, R_{\mathrm{long}}$) from the 3D correlation functions will be presented as a function of collision energy, centrality, rapidity, and pair transverse mass. We will compare the measurements with the results from transport model calculations. Finally, the implications on the properties of QCD matter at high baryon density will be discussed.

Speaker: Youquan Qi

QM2023_poster_qyq_v5.pdf

17:30 Measurements of π, K, p spectra in fixed target collisions with STAR

One of the main physics goals of the Beam Energy Scan (BES) at RHIC is to study the phase diagram of the QCD matter, which separates a phase of quark-gluon plasma (QGP) from a phase of hadronic gas. The first phase of BES studied Au+Au collisions from center-of-mass energy ($\sqrt{s_{_{\rm{NN}}}} $) of 7.7 to 62.4 GeV. The BES Phase-II extended these measurements in several important ways, one of which was the addition of a fixed target program that pushed the energy reach down to a $\sqrt{s_{_{\rm{NN}}}} $ of 3.0 GeV (or $\mu_{\rm{B}}$ up to 720 MeV). Fixed target collisions at STAR allow for a more extensive scanning of the QCD phase diagram to an important region where the QCD critical point may lie, and to a region dominated by dense baryonic matter. Light-flavor hadron prouduction can constrain theoretical models of QCD dynamics, thus providing a method of identifying the transition from a hadronic gas to the QGP. In this poster, preliminary results on the yields of light-flavor hadrons [$\pi,\ \rm{K},\ \rm{p}$] from fixed target Au+Au collisions at STAR will be presented.

Speaker: Mathias Labonte

QM poster_Mathias_Labonte.pdf

17:30 Measurements of φ production in Au+Au collisions at √sNN = 27 , 19.6 , 14.6 and 7.7 GeV with STAR

$\quad$The $\phi$ vector meson is the lightest bound state of hidden strangeness, consisting of a ($s\bar{s}$) quark-antiquark pair. It has a long lifetime (46 fm/c) and relatively small hadronic interaction cross section. Therefore, it is less susceptible to final-state effects and can be used to study the early evolution of the system. In addition, coalescence model calculations indicate that the $\Omega/\phi$ yield ratio is sensitive to strange quark thermodynamic properties, and its dependence on collision energy can potentially be used to probe the onset of deconfinement.
$\quad$In this poster, we will present new measurements on transverse momentum ($p_T$), rapidity ($y$), and centrality dependence of $\phi$ meson yields in Au+Au collisions at $\sqrt{s_{NN}}$ = 27, 19.6, 14.6 and 7.7 GeV using data taken during Beam Energy Scan (BES) II by the STAR experiment. Resonance to non-resonance yield ratios ($\phi/K$) will be shown as a function of centrality for various collision energies. The nuclear modification factor using the peripheral Au+Au collision as a reference for $\phi$ at $\sqrt{s_{NN}}$ = 7.7-27 GeV will also be presented and the physics implications will be discussed.

Speaker: Weiguang Yuan (清华大学)

17:30 Measuring the Global Spin Alignment of Vector Mesons in Heavy Ion Collisions by STAR

In non-central Heavy-Ion collisions, a large orbital angular momentum is produced. A part of the orbital angular momentum can polarize the quarks and anti-quarks, hence the vector mesons, inside the medium. Recently, STAR measured the global spin alignment of φ(1020) mesons in Au+Au collisions from the first phase of the RHIC Beam Energy Scan I (BES I) program [1].

The global spin alignment, quantified by the 00th coefficient of the spin density matrix ρ00, is measured by a fit to the acceptance and efficiency corrected φ meson yield versus polar angle (θ∗) between the daughter kaon in the parent’s rest frame and the orbital angular momentum direction.

In this poster, we present an alternative approach to extract ρ00 by utilizing the ⟨cos2 θ∗⟩ as a function of pair-invariant mass instead of analyzing the φ meson yields in cos θ∗ bins. The acceptance and efficiency effects are taken into account by using the combinatorial background. This method only uses the signal to background ratio and is insensitive to few percent variations in the yield vs. θ∗. We report preliminary results from this method and compare with previous measurements by STAR.

[1] M. Abdallah et al. (STAR Collaboration), Nature 614, 244–248 (2022).

Speaker: C.W. Robertson (Purdue University)

17:30 Measurment of Two-Point Energy Correlator Within Jets in $pp$ Collisions at $\sqrt{s}$ = 200 GeV

Hard-scattered partons ejected from high-energy collisions undergo fragmentation and hadronization, resulting in collimated sprays of particles that are clustered into jets. The Energy-Energy correlator (EEC) is a jet substructure observable used to study the time evolution of the parton shower. This observable re-contextualizes jet substructure study by using the distribution of angular distance of all combinations of two final state particles within a jet weighted by the product of the fractions of jet energy carried by each constituent. With this definition, the perturbative and non-perturbative QCD effects can be separated without the need for re-clustering or rejection of soft constituents. The EEC distribution cleanly reveals the separation between these two regimes: i) from the free hadrons phase at small opening angles, and ii) from the perturbative fragmentation of quarks and gluons at large opening angles.

In this poster, the first measurement of the corrected EEC distribution at RHIC is presented using $pp$ collision data at $\sqrt{s}$ = 200 GeV collected by the STAR experiment. The EEC is shown differentially in jet transverse momentum and compared to predictions from the Monte-Carlo event generator PYTHIA-8 and next-to-leading-logarithmic pQCD calculation. Furthermore, this work will serve as the baseline for future measurements of the EEC in heavy-ion systems which will provide information about how the quark-gluon plasma interacts with jets across different angular and time scales.

Speaker: Andrew Tamis (Yale University)

Tamis_QM2023_Poster.pdf

17:30 Medium response made efficient: a linearized hydro approach

When a jet injects energy and momentum into a droplet of QGP, it generates a wake that, after the QGP hadronizes, results in the creation of soft and semi-hard particles correlated with the jet direction. This medium response phenomenon plays a crucial role in describing various jet observables, as demonstrated by many jet quenching studies. However, the computational complexity of current techniques used to describe these wakes has hindered a thorough understanding of their phenomenological consequences. In this talk we will describe a computationally efficient approach to determine the properties of hadrons generated by QGP wakes on an event-by-event, jet-by-jet basis. Using a library of template solutions obtained within linearized hydrodynamics on a Bjorken flow, and employing the appropriate set of scalings, translations, rotations, and boosts to build the wake of any jet via superposition of templates, we achieve results similar to those obtained through 3+1D hydrodynamics, but with a computational cost that is orders of magnitude smaller.

Speaker: Xiaojun Yao (University of Washington)

qm23.pdf

17:30 Model study on bottomonia modification in small collision systems

Quarkonia have been long considered as key features in heavy ion collision to study the properties of the quark-gluon plasma. One of the key signatures is the sequential yield suppression for different quarkonium states in nucleus-nucleus (A+A) collisions compared to p+p collisions following the ordering of their binding energies. Moreover, sequential yield modification has also been observed in small collision systems such p+Au and p+Pb collisions. Theoretical models consider dissociation and regeneration effects to describe these experimental results, whereas the additional suppression of excited states in small systems is considered to be beyond initial-state effects which is premature to claim for any hot medium effect. To quantitatively test and disentangle such hot medium effects, a model study is performed in various small collision systems such as p+p, p+Pb, p+O, and O+O collisions for $\Upsilon(nS)$ production. In this model, we incorporate a theoretical calculation of hot in-medium effects for $\Upsilon(nS)$ states into a Monte Carlo simulation to more realistically probe the medium produced in heavy ion collisions with event-by-event initial collision geometry and hydrodynamical evolution. The theory calculation considers gluo-dissociation and inelastic parton scattering for dissociation and their inverse reaction for regeneration and reasonably describes the modification of $\Upsilon(1S)$ in Pb+Pb collisions. In this work (Phys. Rev. C 107, 054905 (2023)), we quantify the nuclear modification factor of $\Upsilon(nS)$ as a function of charged particle multiplicity ($dN_{ch}/d\eta$) and transverse momentum. We also calculate the elliptic flow of $\Upsilon(nS)$ in small collision systems. The results are compared with existing experimental results and discussed in terms of prospects for the upcoming LHC oxygen ion run.

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

SHINCHON_QM23_v2.pdf

17:30 Molecular dynamics analysis of particle number fluctuations of a first-order phase transition

We study the critical point effects on particle number fluctuations both in the crossover ($T > T_{\rm c}$) and mixed phase ($T < T_{\rm c}$) regions by means of molecular dynamics simulations of a Lennard-Jones fluid, motivated by the ongoing search for the QCD critical point in heavy-ion collisions.

In the crossover region, we find large fluctuations associated with the critical point in coordinate space, but in the absence of collective flow and expansion, they are essentially washed out when momentum cuts are imposed instead.

In the mixed phase region, the behavior depends on whether the system is in a metastable nucleation or cavitation region, or in the spinodal decomposition region, and can be interpreted in terms of simplified analytic models. For the case of nucleation, we find that fluctuations are qualitatively described by a non-interacting cluster model.
The spinodal decomposition, on the other hand, leads to large fluctuations in coordinate space, which can be understood to arise due to the interplay between the size of the acceptance region and that of the liquid phase.

Speaker: Mr Volodymyr Kuznietsov (Bogolyubov Institute for Theoretical Physics of the National Academy of Sciences of Ukraine)

PosterQM23.pdf

17:30 Momentum shell and rapid stiffening in Quarkyonic matter from explicit duality

Large-$N_c$ QCD implies a duality between confined baryons and deconfined quarks at high baryon densities; it is called Quarkyonic matter. We present a model of Quarkyonic matter that is explicitly dual between quarks and baryons. The duality means that the free energy of the matter is expressed in two ways: One is as a functional of the quark distribution function in the momentum space, $f_Q$, and the other as a functional of the baryon distribution function, $f_B$. We then posit the duality relation between $f_Q$ and $f_B$, which describes the binding of quarks into baryons.
We explicitly construct an analytic solution of this model and show that the theory has two distinct regimes: An ordinary nuclear matter regime at low density and a Quarkyonic regime at relatively high density. In the Quarkyonic regime, $f_B$ is underoccupied at low momentum and has an enhanced occupation at high momentum, which can be interpreted as that baryons sit on a shell in momentum space on top of a quark Fermi sea. Baryons and quarks do not interact except for the duality relation and the constraint that $f_Q$ and $f_B$ must satisfy $0 \le f_Q \le 1$ and $0 \le f_B \le 1$. Such a theory describes a rapid transition from a soft nuclear equation of state to a stiff Quarkyonic equation of state. At this transition, there is a rapid increase in the sound velocity.

Speaker: Yuki Fujimoto (University of Washington)

QM2023_Fujimoto_submit.pdf

17:30 Momentum transport coefficients with chiral dependent quark masses in thermal QCD medium

We have studied the momentum transport coefficients, viz. shear and
bulk viscosity, in a weakly magnetized ($eB << T^2$) deconfined thermal
QCD medium at finite quark chemical potential ($\mu$). The magnetic
field generates anisotropy in the medium, causing the previously
isotropic scalar transport coefficients to become anisotropic and separate into several components. Depending upon the direction of the magnetic field and current, we can have three possible components, namely, longitudinal, transverse, and Hall. We have obtained five shear ($\eta_0, \eta_1, \eta_2, \eta_3$ and $\eta_4$) and two bulk viscous components ($\zeta_0$ and $\zeta_1$) using relativistic Boltzmann transport equation under relaxation time approximation. Interaction among partons is incorporated through the quasiparticle mass of quarks and gluons (T, $\mu$, B dependent), calculated using oneloop perturbative thermal QCD.
It is observed that the magnetic field acts differently on left (L) and
right (R)-handed chiral modes of quark. This leads to the lifting of degeneracy in mass of those modes, in contrast to the strong magnetic field case ($eB >> T^2$), where these modes are degenerate. The magnetic field dependence of L and R modes of $\eta_0$, $\eta_1$ and $\eta_3$ is opposite in nature, viz. the L mode magnitude decreases whereas the R mode magnitude increases, with the magnetic field. This is in contrast to $\eta_2$ and $\eta_4$, for which, both the L and R mode magnitudes
increase with the magnetic field. The bulk viscous coefficients, $\zeta_0$ and $\zeta_1$ increase with magnetic field for both L and R mode. Also, these shear and bulk viscosities get amplified with quark chemical potential for both modes. Shear viscosity to entropy density ratios are found to be greater than $1/(4\pi)$ for $\eta_0, \eta_1$ and $\eta_3$, but less than $1/(4\pi)$ for $\eta_2$ and $\eta_4$. The ratio of bulk viscosity to entropy density for $\zeta_0$ and $\zeta_1$ exhibits a non-monotonic behaviour with temperature, showing minima or maxima around $T\sim$ 200 MeV. Furthermore, the Reynolds number for L mode is found to be greater than
that for R mode due to a difference in mass densities.

Speaker: Ms Pushpa Panday

17:30 Multi-differential Studies of Strangeness Production with the CBM at FAIR using Machine Learning Techniques

The Compressed Baryonic Matter (CBM) experiment at FAIR will investigate the QCD phase diagram at high net-baryon densities ($μ_B$ > 500 MeV) with heavy-ion collisions in the energy range $\sqrt{s_{NN}} = 2.9−4.9$ GeV. Precise determination of dense baryonic matter properties requires multi-differential measurements of strange hadron yields and their collective flow, both for the most copiously produced $K_s^0$ and Λ as well as for rare (multi-)strange hyperons and their antiparticles.

In CBM strange hadrons Λ, $K_s^0$ and $Ξ^-$ are reconstructed by their weak decays using a Kalman Filter algorithm. A machine learning model based on boosted decision trees (XGBoost) is used to make a non-linear multi-parameter selection according to the topology of the decay with high purity and high background rejection. For the rare $Ξ^-$ baryon a special selection using two consecutive XGBoost models is used. The yield of the strange hadrons is extracted multi-differentially using a multi-step fitting routine, where each $p_T$-$y$-interval has its separately trained machine learning model.

The CBM performance for multi-differential analysis of yields and collective flow of strange hadrons Λ, $K_s^0$ and $Ξ^-$ will be presented together with an estimation of systematic uncertainties. Also, statistical error projections for flow measurements with rarely produced strange hyperons at the high rate data taking expected at CBM will be shown.

Speaker: Axel Puntke (WWU Münster)

QM2023-Poster-CBM-ML-v2.pdf

17:30 Multi-parton interactions in pp collisions using charged-particle flattenicity with ALICE

Event classifiers based either on the charged-particle multiplicity or on event topologies, such as spherocity and Underlying Event, have been extensively used in proton-proton (pp) collisions by the ALICE Collaboration at the LHC. These event classifiers became very useful tools since the observation of fluid-like behavior in high multiplicity pp collisions, for example radial and anisotropic flow. Furthermore, the study as a function of the charged-particle multiplicity in the forward V0 ALICE detector allowed for the discovery of strangeness enhancement in high-multiplicity pp collisions. However, one drawback of the multiplicity-based event classifiers is that, requiring a high charged-particle multiplicity, biases the sample towards hard processes like multijet final states. These biases blur the effects of multi-parton (MPI) interactions and make it difficult to pin down the origins of fluid-like effects.

This contribution explores the use of a new event classifier, the charged-particle flattenicity, defined in ALICE using the charged-particle multiplicity estimated in 2.8 < η < 5.1 and −3.7 < η < −1.7 intervals. New final results on the production of pions, kaons, protons, and unidentified charged particles at midrapidity (|η| < 0.8) as a function of flattenicity in pp collisions at √s = 13 TeV will be discussed. It will be shown how flattenicity can be used to select events more sensitive to MPI and less sensitive to final state hard processes. All the results are compared with predictions from QCD-inspired Monte Carlo event generators such as PYTHIA and EPOS. Finally, a preliminary study using the flattenicity estimator using Run 3 data will be shown.

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

poster.pdf

17:30 Multiplicity dependence of $\Upsilon$ and $J/\psi$ production in $p$+$p$ collisions at $\sqrt{s}$ = 510 GeV

Studying quarkonium production allows us to probe the properties of strongly interacting matter, such as the quark-gluon plasma and the gluonic matter in heavy nuclei. While such a probe is widely used, a complete understanding of the quarkonium production mechanism is not yet achieved, even for $p$+$p$ collisions. Therefore, quarkonium studies in $p$+$p$ collisions are essential for advancing the field. Measuring the dependence of self-normalised quarkonium yield on self-normalised charged particle multiplicity can elucidate the interplay of involved soft- and hard-QCD processes. While proposed explanatory mechanisms, including multi-parton interactions, string screening, and gluon radiation, converge at low values of self-normalised multiplicity, their divergence at higher values emphasises the potential for new insights by extending experimental reach in multiplicity.

Herein we present measurements of $\Upsilon$(1S+2S+3S) and $J/\psi$ production, reconstructed through the dielectron decay channel, in $p$+$p$ collisions at $\sqrt{s}$ = 510 GeV recorded by the STAR detector in 2017. Observables include transverse momentum and rapidity distributions, as well as the self-normalised $\Upsilon$ and $J/\psi$ yields as a function of self-normalised charged particle multiplicity. The presented analysis utilises a large sample of quarkonia with up to a factor of 10 increase in statistics compared to previous STAR measurements, therefore both improving precision and extending the reach into higher multiplicity.

Speaker: Prof. Anders Garritt Knospe (Lehigh University)

17:30 Multiplicity dependence of $\Xi_\mathrm{c}^{+}$ baryon production in pp collisions at $\sqrt{s}$ = 13 TeV with ALICE

Recent measurements of the baryon-to-meson production yield ratios between charm baryons ($\Lambda_\mathrm{c}^{+}$, $\Sigma_\mathrm{c}^{0,++}$, $\Xi_\mathrm{c}^{0,+}$, $\Omega_\mathrm{c}^{0}$) and $\mathrm{D}$ mesons ($\mathrm{D}^0$) in small collision systems show a significant enhancement with respect to the measurements performed in $e^{+}e^{-}$ collisions. These results were compared with various models implementing a modified hadronization of charm quarks in hadronic collisions, which enhance the production of baryons.
The models can describe the measurements of $\Lambda_\mathrm{c}^{+}$ and $\Sigma_\mathrm{c}^{0,++}$, that don't contain a strange quark.
However, the models cannot provide an accurate description for the $\Xi_\mathrm{c}^{0,+}$ and $\Omega_\mathrm{c}^{0}$ measurements, which contain both charm and strange quarks, even though the models which include hadronization via both coalescence and fragmentation show the similar trends in baryon-to-meson production yield ratios obtained from the data.
Therefore, further investigation are needed to unveil the hadronization of charm quarks.

The ALICE Collaboration also measured the $\Lambda_\mathrm{c}^{+}$ baryons as a function of charged particles multiplicity in pp collisions at $\sqrt{s}$ = 13 TeV. In this measurement, the production yield ratios between $\Lambda_\mathrm{c}^{+}$ and $\mathrm{D}^0$ show a remarkable dependence on multiplicity.
Similar measurements of $\Xi_\mathrm{c}^{0,+}$ as a function of the charged particles multiplicity are expected to provide additional constraints for modeling the hadronization mechanism of charm quarks.

In this poster, the measurement of $\Xi_\mathrm{c}^{+}$ for several charged particles multiplicity classes, reconstructed via the hadronic decay channel $\Xi_\mathrm{c}^{+} \rightarrow \Xi^{-} \pi^{+} \pi^{+}$ at midrapidity in pp collisions, will be shown. The results were obtained for pp collisions at $\sqrt{s}$ = 13 TeV, using minimum bias and high-multiplicity triggered data recorded by the ALICE detector.

Speaker: Jaeyoon Cho (Inha University (KR))

JaeYoon_XicMult_QM2023_Final.pdf

17:30 Multiplicity dependent $\pi$, k, p production in pp collisions at 13.6 TeV using ALICE TPC and TOF detectors

In nucleus-nucleus collisions at LHC energies, a deconfined state of matter, the quark-gluon plasma (QGP), is formed. Generally, proton-proton (pp) collisions are used as a reference to study their fundamental properties. However, at the highest energy reached in LHC Run 2, pp collisions at high multiplicity seemed to exhibit signatures of collective phenomena similar to those observed in heavy-ion collisions. The study of the multiplicity-dependent light-flavour particle yields in high-multiplicity pp collisions confronted with those of pions shows a gap between small to large systems, at intermediate multiplicities. LHC Run 3 high luminosity pp collisions represent an essential bridge to reach multiplicities similar to those in peripheral nucleus-nucleus collisions. This contribution will discuss the first new results on $\pi$, k, and p production measured with ALICE in Run 3 pp collisions at $\sqrt{s}=13.6$ TeV. They have been obtained within the newly developed ALICE analysis framework (online and offline system) for Run 3. Particle ratios as a function of multiplicity will also be shown.

Speaker: Banajit Barman (Gauhati University (IN))

17:30 Neutral Pion and Eta Meson Reconstruction with the sPHENIX Detector

sPHENIX is a new detector at the Relativistic Heavy-Ion Collider (RHIC) designed to make precision jet and upsilon measurements in 200 GeV p + p, p + Au, and Au + Au collisions and will begin taking data in 2023. In addition to having the first hadronic calorimeter (HCal) at mid-rapidity at RHIC, sPHENIX also contains a tungsten-scintillator based Electromagnetic Calorimeter (EMCal) for measuring the energy of photons and electrons. Before physics analyses can take place using the EMCal, however, it must be calibrated to the electromagnetic energy scale, and this will be done by calibrating the EMCal’s response relative the neutral pion’s ($\pi^0$) invariant mass. $\pi^0$’s are reconstructed from pairs of EMCal clusters that were produced by decay photons from $\pi^0$’s. However, due to cluster merging effects, this procedure is not practical at high momentum. Thus, as a high-energy cross-check on the energy scale calibration, the calorimeter’s response relative to $\eta$ mesons, whose heavier mass allows for reconstruction without merging to much higher momenta, will also be measured. The EMCal’s successful calibration will enable measurements with the $\pi^0$ and $\eta$ mesons, which will take advantage of both sPHENIX’s large acceptance and the high luminosity 200 GeV Au + Au data set currently being recorded. This poster will show the status of the sPHENIX EMCal’s energy scale calibration and the status of sPHENIX’s first neutral meson analyses

Speaker: Anthony Hodges

hodgesNeutralMesonQM2023.pdf

17:30 Neutral pion and η meson production at midrapidity in Au+Au collisions at √sN N = 200 GeV

Direct photons are useful probes to study the properties of QGP and the dynamic evolution of collision systems. Estimating and subtracting direct photons from hadron decays that contribute to the bulk of the measured photons is crucial and challenging. Although the most abundant source, $\pi^{0}$ $\rightarrow$ $\gamma$$\gamma$ is well studied and constrained. $\eta$ $\rightarrow$ $\gamma$$\gamma$ is less constrained and the related study is scarce below $p_{T}$ $<$ 2 $GeV/c$. The ratio,$\eta/\pi^{0}$ exhibits universal behavior regardless of collision system, energy, and centrality in high $p_{T}$ from the analysis of world data. However, associated measurements have been inconclusive in low $p_{T}$. Possible deviations from the universal behavior could be owing to the rapid radial hydrodynamic expansion of the $A+A$ collision system. PHENIX presents measurements of the centrality dependence of $p_{T}$ spectra of $\pi^0$ and $\eta$ and their ratio in Au$+$Au collisions at $\sqrt{s_{NN}} = 200$ GeV with large statistics data taken in the year 2014. Thanks to the large Au$+$Au data sample taken at $\sqrt{s_{NN}} = 200$ GeV in the year 2014 and improved analysis methods, PHENIX is capable of studying the $p_T$ spectra of $\pi^0$ and $\eta$ down to 1 GeV/c and exploring the effect of radial flow on $\eta/\pi^0$ as a function of centrality.

Speaker: Dading Chen

poster_DC.pdf

17:30 New constraints on 3D initial state and transport parameters of QGP using the Beam Energy Scan phase II data of STAR

Constraining the three-dimensional structure of the initial state and transport properties of the Quark-Gluon Plasma (QGP) at different temperatures ($T$) and baryon chemical potentials ($\mu_B$) is a critical objective of heavy-ion programs at RHIC and the LHC. This work presents comprehensive measurements on both topics for various event-shape and centrality selections of Au+Au collisions at RHIC BES-I (e.g. 11.5, 19.5, and 39~GeV), BES-II (14.6, 27, and 54.4~GeV), and 200~GeV. We present new measurements of the beam energy dependence of higher-order flow-angular de-correlations ($r_n(\eta_a,\eta_b)$) that are sensitive to the three-dimensional initial state. We also study new observables which are selectively sensitive to the viscous attenuation in the final state, such as the transverse momentum correlator $G_{2}(\Delta\eta, \Delta\varphi)$. We observe a non-monotonic behavior in the longitudinal width of $G_{2}(\Delta\eta, \Delta\varphi)$ with the collision energy, which is expected to be proportional to $\eta/s$ according to the ansatz proposed by S. Gavin et. al. [1]. In addition, we further explore the higher-order flow-angular correlation $\langle\cos(a_{1}n_{1}\Psi_{n1}+\cdots+a_{k}n_{k}\Psi_{nk})\rangle$ and the higher-order flow-magnitude correlations $SC(n,m)\{4\}$ and $SC(n,m)\{6\}$ using the $2$- through $6$-particle correlation method. The higher-order flow-angular (magnitude) correlations are predicted to be sensitive to both initial and final state effects. We compare our findings with similar studies conducted at the LHC and with viscous hydrodynamic calculations. Our analyses aim to disentangle the initial and final-state effects and extract the QGP transport properties.

[1] S. Gavin and M. Abdel-Aziz, Phys. Rev. Lett. 97, 162302 (2006)

Speaker: Dr Niseem Magdy Abdelrahman (Stony Brook University)

QM2023_Niseem_Poster.pdf

17:30 New Insights to the Weak Interaction and Quark Model

A quark is a subatomic particle, composed of the mass, electric charge, and color charge, the three fundamental elements found in the nature. Among these three fundamental elements, there are four fundamental interactions, which are the gravitational force between masses, the electromagnetic force between electric charges, the strong force between color charges, and the weak force between electric and color charges. Inside a quark, the weak force or interaction between electric and color charges influences and excites the quark, which relaxes and transits from one state to another by emitting a quark-antiquark pair, in analogy to the emission of a photon by an excited electron in an atom. A quark and an antiquark with either the same or different flavors and states combine to form a meson when they couple together via mainly the strong interaction, a charged lepton when they annihilate their color charges and combine their electric charges and masses, a neutrino when they annihilate both their color and electric charges and combine their masses, and a photon or gamma ray when they entirely annihilate all their mass, electric, and color charges. The decay of a particle (e.g. the beta decay of a neutron) with formation of leptons involves one or more quark-antiquark pair emissions and annihilations. This multi-pair quark and antiquark emission and annihilation process establishes a fine structure of the Feynman diagram for the quark decay with lepton formation and indicates the formed leptons as products rather than participants of the weak interaction. This study attempts to fully explain and describe how various possible particles (far more than the discovered so far) are formed, generated, decayed, and interacted via quark excitations, degenerations, pair productions and annihilations. We aim at advancing and developing the standard model of particle physics and quantum chromodynamics in terms of innovatively theorizing the weak interaction as an interaction between electric and color charges and creatively modelling quarks with two flavors and multiple excitations. This quantum science study is partially supported by the IBM-HBCU Quantum Center.

Speaker: Dr. Tianxi Zhang

Zhang 2023 36x48 a portrait format.pdf

17:30 New measurements of jet $v_2$ properties with ALICE

To be added by ALICE

Speaker: Takuya Kumaoka (University of Tsukuba (JP))

KumaokaPoster20230901_v3.pdf

17:30 Non-Identicle particle femtoscopy in Au+Au collisions at 200 GeV using UrQMD modeled with CRAB

Two particle femtoscopy provide a powerful tool for studying the space–time dynamics of the hot and dense matter (QGP) created in these collisions such as the size, shape, and lifetime as well as advancing our understanding of the behavior of matter at extreme conditions by measuring the relative momentum correlations between pairs of particles emitted in the same direction from the collision. These correlations arise due to quantum statistics, Coulomb and strong final state interactions. From the non-identical particle correlation study, particularly the hyperon-nucleon correlations, one can obtain information about the equation of state (EoS) of neutron stars and the existence of various exotic hadrons (H-dibaryons).We report the calculations of femtoscopic correlations between proton and lambda pairs in Au+Au events simulated using the Ultra-Relativistic Quantum Molecular Dynamics (UrQMD) model at $\sqrt{s_{NN}}$ = 200 GeV via CRAB (Correlation After Burner) to account for the Final State Interaction among the emitted particles. The Correlation Analysis Tool using the Schrödinger equation (CATS) package is used to analyze the p$-\Lambda$ correlation functions obtained from these simulations and extract the source radii and to investigate the interaction potential for p$-\Lambda$ pairs which do not have well determined scattering parameters. However, the calculated femtoscopic radii were compared to STAR experimental data. The study of source radii in heavy-ion collisions at different collision energies can provide information about the phase transition from hadronic matter to quark-gluon plasma and can help to distinguish between different models of the initial state and particle production mechanisms. Furthermore having the source fixed at both high and low energies allows for a direct comparison of the interaction at different energies.

Speaker: MAHIMA SHARMA (University of Jammu)

17:30 Non-interdependent Collective Motions in Heavy-ion Collisions

The widely used Fourier expansion for studying collective motions in heavy-ion collisions implies that different modes of collectivity could be non-interdependent, driven by factorized actions in the created nuclear medium. Following this line of thought, we assume each non-dependent collective motion modulates the probability of particle emission with a single-harmonic Fourier expansion, and then express the final-state particle azimuthal distribution as the product of these expansions,
$\frac{2\pi}{N^\pm}\frac{dN^\pm}{d\varphi} = \prod_{n=1}^{\infty}(1+2\tilde{a}_n^\pm\sin n\Delta \varphi) \prod_{n=1}^{\infty} (1+ 2\tilde{v}_n^\pm\cos n\Delta \varphi)$, instead of a long linear Fourier series. Here, $\Delta\varphi$ is the particle azimuthal angle with respect to the reaction plane. This scheme may better capture the genuine strength of each collectivity mode ($\tilde{a_n}$ and $\tilde{v_n}$), and results in non-leading cross terms between collectivity modes, with significant impacts on experimental observables. We explore the possibility that the chiral magnetic effect (CME) [1] and elliptic flow can evolve separately, thereby their convolution affecting not only the observable that is sensitive to the CME, but also that to the shear-induced CME [2]. We employ the event-by-event anomalous-viscous fluid dynamics model to showcase the implications of this scenario on searches for the CME. In addition, we also propose practical experimental tests using conventional flow harmonics and exploit a multiphase transport model to demonstrate the emergence of non-leading cross terms, such as the rapidity-odd component of triangular flow. The universality of the assumption regarding factorized actions can be investigated by analyzing real data collected from RHIC and the LHC, which will enhance our understanding of the collective motions.

[1] D. E. Kharzeev, L. D. McLerran and H. J. Warringa, Nucl. Phys. A 803, 227 (2008).

[2] M. Buzzegoli, D. E. Kharzeev, Y.-C. Liu, S. Shi, S. A. Voloshin, H.-U. Yee, Phys. Rev. C 10, L051902 (2022).

Speaker: Gang Wang (UCLA)

QM2023_poster_async_v3.pdf

17:30 Non-perturbative Quarkonium Dissociation Rates in the QGP

We perform a non-perturbative calculation of quarkonium dissociation rates in the quark-gluon plasma (QGP) within a thermodynamic T-matrix approach. The latter resums an infinite series of ladder diagrams for heavy-light interactions appropriate for a strongly coupled QGP which are implemented via half-off-shell amplitudes accounting for recoil corrections and interference effects (related to the imaginary part of the Q-Qbar potential). In particular, the T-matrix approach accounts for non-trivial thermal-parton spectral functions in the QGP with an equation of state that agrees with lattice-QCD results, thus ensuring consistency between the heavy- and light-parton sectors. We compare these rates to perturbative ones as previously employed in semiclassical transport calculations and to those utilized in currently employed quantum transport approaches.

[1] S. Y. F. Liu and R. Rapp, Phys. Rev. C 97, 034918 (2018)

Speaker: Biaogang Wu (Texas A&M University)

QM23_Poster_Biaogang_Wu.pdf

17:30 Non-prompt ${\rm J/\psi}$ production as a function of multiplicity in pp collisions at √s = 13 TeV with ALICE

The study of the production of non-prompt ${\rm J/\psi}$ originating from the decay of beauty hadrons, besides allowing to isolate the prompt ${\rm J/\psi}$ cross section from the inclusive ${\rm J/\psi}$ cross section, can be used to estimate open beauty-hadron production. Heavy-flavour particle production in pp collisions as a function of charged-particle multiplicity could provide insight into the processes occuring in the collision at the partonic level, as well as the interplay between the hard and soft mechanisms in particle production.

In this contribution, measurements of the non-prompt ${\rm J/\psi}$ fraction as a function of charged-particle pseudorapidity density (${\rm d}N_{\rm ch}/{\rm d}\eta$) in pp collisions at $\sqrt{s}=13$ TeV with ALICE are reported. ${\rm J/\psi}$ mesons are reconstructed at midrapidity ($|\textit{y}|<0.9$) in the dielectron decay channel. Events are classified based on the charged-particle multiplicity at midrapidity ($|\eta| < 1$). The multiplicity reach is seven times larger than the average charged particle multiplicity of inelastic collisions, thanks to the usage of high-multiplicity triggered events. The measurement of the fraction of non-prompt ${\rm J/\psi}$ is performed via unbinned maximum likelihood fit down to $p_{\rm T} = 1\ {\rm GeV}/c$. The status of the prompt and non-prompt ${\rm J/\psi}$ yield extraction as a function of ${\rm d}N_{\rm ch}/{\rm d}\eta$, both normalized to the corresponding multiplicity integrated quantities, will also be shown.

Speaker: Wenda Guo (Central China Normal University CCNU (CN))

QM2023_poster_WendaGuo_v4.pdf

17:30 Observation of $\pi^+\pi^-\pi^+\pi^-$ photoproduction in ultraperipheral heavy-ion collisions at $\sqrt{s_{NN}} = 200$ GeV at the STAR detector

One of the most pressing questions in both hot and cold QCD communities is what the physics mechanism responsible for modified parton densities in heavy nuclei is. One promising channel to address this question is the photoproduction of vector mesons, which is considered a clean probe to the nuclear parton structures.
We present a measurement of $\pi^+\pi^-\pi^+\pi^-$ photonuclear production in ultraperipheral Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV. The data were collected in 2014 by the STAR experiment. The $\pi^+\pi^-\pi^+\pi^-$ final states, accompanied by mutual excitation of projectile and target, are observed to be greatly enhanced at low transverse momentum, which is consistent with coherent photoproduction. The $\pi^+\pi^-\pi^+\pi^-$ invariant mass spectrum in coherent events exhibits a two-resonance structure around $\sim 1370$ and $\sim 1610$ MeV/$c^2$ with widths of 200 and 330 MeV/$c^2$, likely corresponding to $\rho(1450)$ and $\rho(1700)$. Furthermore, a peak corresponding to $\rho(2150)$ is observed. We also observe corresponding peaks to $\rho(1450)$ and $\rho(1700)$ in the $\pi^+\pi^-$ final state and report the ratio of the branching fractions of the $\rho(1450)$, $\rho(1700)$ to $\pi^+\pi^-$ and $\pi^+\pi^-\pi^+\pi^-$. We further present the ratios of $\rho(1450)$, $\rho(1700)$, and $\rho(2150)$ to $\rho_0(770)$ coherent production cross sections.

Speaker: Dr David Tlusty (Creighton University)

17:30 Observation of a mesoscopic fluid of 10 strongly-interacting fermions

Collective flow is observed in high-energy proton-proton and proton-nucleus collisions where particle multiplicities are small and a quark-gluon plasma description is hard to justify. Here, we address the origin of such observations from a new angle, by performing an experimental investigation of the emergence of hydrodynamics in two-dimensional ultra-cold Fermi gases with with controllable interactions and in the regime of small particle numbers. We study the inversion of the aspect ratio (akin to elliptic flow) in the expansion of samples of atoms initially prepared in elliptical traps. To overcome the finiteness of the samples, a statistical measure of the elliptic anisotropy is devised in full analogy with the methods employed in the analysis of high-energy collisions.

With ten or more fermions, we observe the emergence of elliptic flow due to inter-particle interactions, which justifies a hydrodynamic interpretation. We show that ideal hydrodynamic predictions using the equation of state of 2D Fermi gases in the many-body limit underestimate the measured elliptic anisotropy. Hence, we witness the breakdown of ideal hydrodynamics due to quantum corrections beyond standard dissipative ones but rather induced by the mesoscopic nature of our samples. We discuss how hydrodynamic equations could be generalized to account for these effects, and give an outlook on further possibilities with our experimental setup to advance our understanding of collective phenomena in few-particle systems.

Based on:

• Floerchinger et al., "Qualifying collective behavior in expanding ultracold gases as a function of particle number", Phys. Rev. C 105, 044908 (2022)
• Brandstetter et al., "A mesoscopic fluid of 10 fermions", arXiv:2305.XXXXX

Speaker: Giuliano Giacalone (Universität Heidelberg)

17:30 Observation of the $\gamma\gamma\to\tau\tau$ production in PbPb collisions with the CMS experiment

Ultraperipheral nucleus-nucleus collisions produce very large photon fluxes such that fundamental quantum-mechanical processes can be observed and studied in a novel way. In this presentation, an observation of the $\tau$ lepton photoproduction at LHC is reported, using ultraperipheral lead-lead collision data collected by CMS. This measurement paves the way for a precise determination of the $\tau$ lepton anomalous magnetic moment which, contrary to the electron and muon counterparts, is poorly constrained.

Speaker: Matthew Nickel (The University of Kansas (US))

QM 2023 Poster MN.pdf

17:30 On the gravitational wave emission in the magnetic field of a heavy-ion collision

On the gravitational wave emission in the magnetic field
of a heavy-ion collision

In the classic 1961 paper of Gertsenshtein [1] he demonstrated that an electromagnetic wave can be transformed into a gravitational wave when propagating through an external, transverse magnetic field. Later in 1973, Zel’dovich calculated the fraction of energy of the electromagnetic wave transformed into the energy of the gravitational wave in such a process in astrophysical situations [2].
In the following, we investigate a possibility of a transition of an electromagnetic wave into a gravitational wave in the high magnetic field expected to be formed in heavy-ion collisions.

Electromagnetic radiation, emitted in all stages of a heavy-ion collision, reflects the evolution of the latter and encodes the information on the properties of the created medium, such as fireball lifetime, temperature, acceleration, and polarization. This information can be decoded by studying di-lepton spectra by means of their invariant mass reconstruction. The slope of the di-lepton excess spectrum measured in the intermediate-mass region provides information on the temperature of the emitting medium.

In the poster, we discuss the modification of a slope value due to the excitation of a gravitational wave by light emitted from the medium in the magnetic field generated in a non-central heavy-ion collision. Based on several simplifications, we estimate the possible redshift and conclude the effect is not detectable with heavy-ion experiments planned in the foreseeable future. However, with this contribution, we also want to trigger a discussion on the emerging field of ultra-high-frequency gravitational waves physics and its possible relation to high-energy heavy-ion collision physics.

References:
[1] M. E. Gertsenshstein, J. Exptl. Theoret. Phys. (U.S.S.R.) 41, 113-114 (July 1961)
[2] Ya. B. Zel'dovich, Zh. Eksp. Teor. Fiz. 65, 1311-1315 (October 1973)

Speaker: Piotr Gasik (GSI - Helmholtzzentrum fur Schwerionenforschung GmbH (DE))

QM23_PGasik_Poster.pdf

17:30 Particle Identification with the ePIC detector at the EIC

The ePIC detector is being designed as a hermetic, general-purpose detector for the Electron-Ion Collider (EIC). One of the key performance drivers for the physics programme at the EIC are the particle identification (PID) system, which enable the separation of pions, kaons, and protons in high multiplicity events over a wide phase space, with significant pion/electron suppression. To address this challenge, ePIC plans to utilize multiple independent particle identification sub-detector systems.

The talk will cover the PID subsystems of the ePIC detector, which comprise a of time-of-flight (TOF) detector for low-momentum PID and several high-momentum particle-identification systems that use DIRC and RICH techniques to exploit Cherenkov light emission from charged particles. R&D activities are underway to develop the AC-LGAD technology selected for the TOF, evaluate the use of SiPMs as photosensors for RICH detectors, explore the capabilities of novel LAPPD detectors and assess the compatibility of commercial MCP-PMT with the experiment's magnetic field conditions. The presentation will also include a discussion of the projected performance of the PID detector system, which has been studied in detail using Geant4 simulations, as well as potential future upgrades.

Speaker: Oskar Hartbrich (Oak Ridge National Lab)

17:30 Particle multiplicity dependent Charmonia production in $p+p$ collisions by the PHENIX experiment

The simple picture of a hard scattering per $p+p$ collision has been challenged by several measurements performed at LHC and RHIC, revealing a more complex dynamics of multiple parton interactions (MPI) which are essential to fully understanding particle production in hadronic collisions. Hard probe measurements at different particle multiplicity regimes in $p+p$ collisions provide a clean method to study (MPI). The PHENIX experiment has a unique capability to simultaneously measure particle production at forward (1.2$<\eta<$2.2), mid- ($|\eta|<0.25$) and backward (-2.2$<|\eta|<$-1.2) rapidities. This presentation will report on the results of J/$\psi$ production in $p+p$ collisions at $\sqrt{s}=$200 GeV when the particle multiplicity is measured at different rapidity regions. The gap between the J/$\psi$ and the particle multiplicity measurement allows us to explore how the particles involved in the J/$\psi$ production itself can affect the multiplicity dependent measurements.

Speaker: JongHo Oh (Pusan National University)

17:30 Partonic Critical Opalescence and Its Impact on the Jet Quenching Parameter $\hat{q}$}

Jet quenching parameter $\hat{q}$ is essential for characterizing the interaction strength between jet partons and nuclear matter. Based on the quark-meson (QM) model, we develop a new framework for calculating $\hat{q}$ at finite chemical potentials, in which $\hat{q}$ is related to the spectral function of the chiral order parameter. A perturbative calculation up to the one-loop order indicates that the momentum broadening of jets is enhanced at both the high temperature and high chemical potential, and approximately proportional to the parton number density in the partonic phase. We further investigate the behavior of $\hat{q}$ in the vicinity of the critical endpoint (CEP) by coupling our calculation with a recently developed equation of state that includes a CEP in the universality class of the Ising model, from which we discover the partonic critical opalescence (PCO) -- a prominent enhancement of the momentum broadening of jets near CEP, contributed by the scatterings via the $\sigma$ exchange process. Hence, for the first time, jet quenching is connected with the search of CEP.

Speaker: Jing Wu (lanzhou university)

17:30 Performance study of the exclusively reconstructed $B^\pm$ meson in the $J/\psi$ decay channel with ALICE

The $B^\pm$ meson is produced more frequently than any other meson containing beauty quarks in pp collisions at the LHC. Measuring its production cross-section is important for two reasons. Firstly, it allows for testing perturbative quantum chromodynamics calculations. Secondly, it provides an essential reference for measurements of its nuclear modification factor ($R_{\rm A \rm A}$) in heavy-ion collisions. The $B^\pm$ meson $R_{\rm A \rm A}$ measurement can provide new constraints on the partonic energy loss mechanism in the medium formed in heavy-ion collisions. Since the radiative energy loss depends heavily on the quark mass, the beauty quark, being the heaviest readily observable flavor, is a particularly valuable probe for investigating the mass dependence of the in-medium energy loss mechanisms. Due to its design, ALICE is unique in accessing beauty production in the low $p_{\rm T}$-region at midrapidity ($|y|<0.9$).

This poster shows a performance study of the exclusive reconstruction of the $B^\pm$ meson at midrapidity through the decay channel $B^\pm \rightarrow J/\psi + K^\pm$, with the $J/\psi$ reconstructed in its dielectron decay channel. Exclusive reconstruction of beauty mesons will be done for the first time in ALICE during LHC Run 3. In previous LHC runs, inclusive beauty hadron measurements were carried out via non-prompt $J/\psi$ using the displacement of the secondary vertices with respect to the primary vertex. This study, however, relies on full reconstruction of the $B^\pm$ meson candidate, taking advantage of the improved vertex resolution provided by the upgraded Inner Tracking System of ALICE, fully operational during the LHC Run 3. The poster will show the status of the $B^\pm$ meson reconstruction and expected performance in pp collisions at  $\sqrt{s_{\rm N \rm N}} =$ 13.6 TeV at midrapidity.

Speaker: Ida Storehaug (University of Oslo (NO))

QMposter_v8.pdf

17:30 PHENIX measurements of identified charged hadron production in $p$+Al, $p$+Au, and Cu+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV

Identified hadrons have proven to be useful in elucidating the final state effects of heavy ion collisions. This includes in particular the important role that hadronization plays on a variety of final state observables. System size is known to influence various observables, and the overlap in system size between different collision systems has helped establish the commonality between them, thereby demonstrating consistent properties of the quark-gluon plasma. In this talk, we will present recently finalized measurements of identified charged hadrons in $p$+Al, $p$+Au, and Cu+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV. We will also compare these to similar results in other collision systems, and discuss the implications for QGP formation and collective flow in small and large systems.

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

QM2023_poster_PHENIX_shLim.pdf

17:30 Photon radiation by rotating systems in magnetic field.

Experimental observations indicate that quark-gluon plasma produced in heavy-ion collisions has high vorticity and is subject to an intense magnetic field. We present a study of the photon radiation by a charged fermion rotating with the plasma in a constant magnetic field B. The angular velocity of rotation is assumed to be much smaller than the inverse magnetic length, which allows us to ignore the effects of the causal boundary. Using the exact solution of the Dirac equation, we calculated the spectrum and intensity of electromagnetic radiation. The rotation significantly impacts the radiation intensity and is relevant to the relativistic heavy-ion phenomenology. The presentation is partially based on Phys.Rev.D 107 (2023) 5, L051901.

Speaker: Nandagopal Vijayakumar

Quark_Matter_2023_Poster_Final_Nandagopal.pdf

17:30 Photoproduction of e$^{+}$e$^{-}$ in peripheral isobar collisions

We investigate the photoproduction of di-electrons in peripheral collisions of $^{96}_{44}$Ru+$^{96}_{44}$Ru and $^{96}_{40}$Zr +$^{96}_{40}$Zr at 200 GeV. With the charge and mass density distributions given by the calculation of the density functional theory, we calculate the spectra of transverse momentum, invariant mass and azimuthal angle for di-electrons at 40-80% centrality. The ratios of these spectra in Ru+Ru collisions over to Zr+Zr collisions are shown to be smaller than (44/40)$^4$ (the ratio of Z$^4$ for Ru and Zr) at low transverse momentum. The deviation arises from the different mass and charge density distributions in Ru and Zr. So the photoproduction of di-leptons in isobar collisions may provide a new way to probe the nuclear structure.

Speaker: Shuo Lin

17:30 Physics prospects of central exclusive production in pp collisions with ALICE Run 3 data

Central exclusive production (CEP) is a diffractive process in which the colliding particles remain intact. Three different processes are involved: photon-photon exchange, photon-pomeron exchange and double-pomeron exchange. Each process produces distinguishable states with specific sets of quantum numbers, making CEP measurements a unique tool for searching for exotic resonances. Furthermore, measurements of well-known states in CEP can provide a clean probe of the structure of matter. For example, the photoproduction of the J/𝜓 (via photon-pomeron exchange) can be used for probing the low-𝑥 gluon content of protons.

In ALICE, events of the CEP can be identified by its signature of double-gap in pseudorapidity. Relying on the tracking and particle identification capabilities in the central barrel of ALICE, various final state two particle systems can be measured including 𝜋+𝜋− and 𝐾+𝐾−. In addition, heavy vector mesons such as J/𝜓 can be studied via their decay into 𝑒+𝑒− pair.

In this contribution, we will present the performance of the ALICE Run 3 detector for measurements of double-gap events in pp collisions at √s = 13.6 TeV. In addition, we will discuss physics prospects of central exclusive production in pp collisions with ALICE detector.

Speaker: Minjung Kim (University of California Berkeley (US))

QM2023_DGevent_mjkim_v4.pdf

17:30 PNJL equation of state with off-shell mesonic excitations

We study the contribution to the equation of state from mesonic correlations in the Polyakov-loop Nambu--Jona-Lasinio model within the Beth-Uhlenbeck approach, with a focus on the spacelike region of the spectral function. We show that the inclusion of such excitations leads to a significant increase of the pressure of the model near the pseudocritical temperature of the chiral phase transition and a significant meson momentum cut-off dependence in the mesonic pressure and the QCD trace anomaly. By means of the Feynman-Hellmann theorem, we show that the off-shell meson contribution to the chiral condensate can lead to a lowering of the chiral pseudocritical temperature, which may be essential to reduce the tension between PNJL mean field and lattice QCD results.

Based on K. Maslov and D. Blaschke, Phys. Rev. D 107, 094010. Research supported by Polish National Science Centre (NCN) under grant No. 2019/33/B/ST9/03059.

Speaker: Konstantin Maslov (University of Houston)

Maslov_QM23.pdf

17:30 Polarization of vector mesons in non-equilibrium hydrodynamics with spin

We argue that spin alignment of hadrons of spin 1 and higher provide a unique window into the study of hydrodynamics with spin, because it is capable to probe non-equilibrium between spin density and vorticity.
This happens because most of the full 3X3 density matrix is in principle accessible experimentally, and non-zero off-diagonal matrix elements can be directly linked to such non-equilibrium.
We illustrate this using a coalescence model for light vector mesons [1] as well as a potential model for quarkonia, and compare our calculations to experimental data [2].

[1] Kayman J. Gonçalves, Giorgio Torrieri
Phys.Rev.C 105 (2022) 3, 034913 • e-Print: 2104.12941
[2] Paulo de Moura, Kayman J. Gonçalves, Giorgio Torrieri 2305.02428

Speaker: Kayman Gonçalves

Poster Quark Matter 2023_Kayman.pdf

17:30 Precision jet substructure studies for the Relativistic Heavy Ion Collider with the sPHENIX detector

With the newly upgraded sPHENIX detector capable of performing high precision jet substructure measurements, we present a comprehensive and systematic jet substructure study at the Relativistic Heavy Ion Collider. The study includes a variety of key jet substructure variables such as jet angularities with and without soft-drop or collinear-drop grooming, as well as recoil-free di-jet and photon+jet azimuthal angle decorrelation using the Winner-Take-All (WTA) recombination scheme to define the jet directions. We employ various event generators in the study, including Pythia, Herwig and Sherpa for the proton-proton collision baseline. The Caeser framework is used to perform semi-numerical calculations for these observables. With the well-defined perturbative precision, non-perturbative contributions can be robustly extracted. For the medium jet substructure study, we investigate different Monte Carlo implementations of quenching models such as JETSCAPE, Jewel and QPythia. The jet observables have different sensitivities to physics ranging from parton shower to soft radiation, allowing us to quantify model differences and thereby point to modification patterns through which future experimental data may shed light on the nature of jet-medium interaction.

Speaker: Oleh Fedkevych (Georgia State University)

QM_Oleh_Fedkevych.pdf

17:30 Probing particle production and transport at top LHC Run 3 energy with ALICE

Two-particle number and transverse momentum correlations are sensitive probes of particle production and transport in AA collisions. Their shape and strength are sensitive to the interplay of all production processes, and are further influenced by transport mechanisms, including longitudinal, radial, and anisotropic flow. However, the correlations are also sensitive to instrumental effects, including distortions associated with space-charge effects in the Time Projection Chamber (TPC), to technical issues related to pile up rejection, suppression of contamination, and corrections for particle losses. It is thus a fundamental quality control for the ALICE data-taking machinery to perform analyses already completed and compare the results obtained with the new GEM readout, the new data-collecting machinery, and the new software framework, with those obtained with the prior TPC readout technology and overall scenario.

In this contribution, two-particle number and transverse momentum correlations in different multiplicity classes of pp collisions at $\sqrt{s} = 13.6\;\text{TeV}$ recorded by ALICE during the Run 3 at the LHC are reported. The very large datasets obtained in Run 3 will provide for a significant reduction of statistical and systematic uncertainties and enable more differential analyses of these correlations based on more varied and selective kinematic criteria. Results will be compared with previous results from Run 1 and Run 2 which, apart from validating the new data-taking machinery, will shed light on the evolution of these correlators with collision energies.

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

ParticleProductionRun3_20230901.pdf

17:30 Probing parton shower and hadronization with novel jet substructure measurements at STAR

Jets are collimated sprays of final-state particles produced from initial high-momentum-transfer partonic scatterings in particle collisions. Since jets are multi-scale objects that connect asymptotically free partons to confined hadrons, jet substructure measurements in vacuum can provide insight into the parton evolution and the ensuing hadronization processes. With $\sqrt{s} = 200$ GeV $pp$ collision data recorded by the STAR experiment, we reconstruct full jets to measure CollinearDrop$-$SoftDrop jet correlation and the charge correlation ratio ($r_c$) with hadrons in jets, which probe the dynamics of the parton shower and hadronization, respectively.

The interplay between different stages of the parton shower can be explored with the correlation between SoftDrop and CollinearDrop groomed jet observables, the latter of which have an enhanced sensitivity to the soft radiation within jets. We present the first measurements of CollinearDrop jet mass and its correlation with SoftDrop groomed jet observables, such as the opening angle $R_{\mathrm{g}}$ and the shared momentum fraction $z_{\mathrm{g}}$. They are fully corrected for detector effects with a novel machine learning method, MultiFold, which preserves the correlations in the multi-dimensional observable phase space.

Precision measurements sensitive to the hadronization process are crucial for testing phenomenological models and furthering our understanding of non-perturbative QCD. The observable $r_c$ characterizes the fraction of string-like fragmentation by distinguishing the charge signs of leading and subleading charged particles within jets. We present the first measurement of $r_c$ in hadronic collisions and compare it to event generator predictions.

Speaker: Youqi Song

qm_poster_090123.pdf

17:30 Probing the effect of the nonextensivity on the transport properties of hot QCD medium at finite magnetic field and chemical potential

We have probed the effect of the nonextensivity on the transport properties related to the charge and heat in hot QCD medium at finite magnetic field and chemical potential. The coefficients associated with the charge and heat transport, such as the electrical conductivity, Hall conductivity, thermal conductivity and Hall-type thermal conductivity are determined using the nonextensive Tsallis framework within the relaxation time approximation of kinetic theory. The Tsallis distribution function encodes the effect of the nonextensivity, where the deviation of parameter $q$ from unity signifies the extent of the nonextensivity. The matter produced in heavy ion collisions may not be exactly in the locally equilibrated state, and for understanding the properties of such matter to a greater degree, the nonextensive Tsallis framework is a relevant approach to follow. Our observation shows that the electrical and thermal conductivities as well as their Hall components increase with the nonextensivity and this implies an increased deviation of both charge and heat transports from their counterparts at $q=1$. It is observed that the deviations of the abovementioned transport coefficients from their respective equilibrated values get further increased at finite magnetic field, whereas these deviations become decreased at finite chemical potential. Furthermore, the effects of the nonextensivity on the flow characteristics through the Knudsen number, specific heat and elliptic flow have been explored.

Speaker: Shubhalaxmi Rath (Indian Institute of Technology Bombay)

17:30 Probing the QGP to Hadron-Gas Phase Transition with Charge, Strange, and Baryon Balance Functions

Charge balance functions (BFs) were introduced at the beginning of the RHIC era as a tool to investigate the evolution of particle production in heavy-ion collisions and identify the presence of delayed hadronization as an indicator of the formation of long lived isentropic expanding quark gluon plasma in high-energy nucleus-nucleus (A--A) collisions. It later emerged that BFs are rather sensitive to the radial expansion dynamics of the matter formed in these collisions and can, in principle, be used to probe hadron production mechanisms such as the formation of clusters. Later still, it was found that the azimuthal dependence of hadrons BFs, particularly heavier hadrons, is sensitive to the diffusivity of light quarks. In this work, we show how the conservation of quantum numbers can be properly accounted for and how cross-species BF can be exploited to determine the relative strengths of distinct species pairs from heavy hadron decay feeddowns, long range correlations arising at the onset of collisions, and contributions from baryon stopping. We addtionally examine the possibility of probing the degree of equilibration achieved in A--A collisions (at both RHIC and LHC energies) as well as the evaluation of QGP susceptibilities by means of measurements of charge, strange, and baryon BFs. We show that baryon BFs, in particular, may enable a detailed assessment of baryon stopping. This work is based on Monte Carlo simulations performed in a variety of models and provides a road map for future studies at the LHC based on detector upgrades such ALICE 3.

Speaker: Prof. Claude Andre Pruneau (Wayne State University (US))

PruneauPosterVesrion1.pdf

17:30 Probing the QGP to hadron-gas phase transition with mean transverse momentum fluctuations with ALICE

The study of event-by-event fluctuations of the mean transverse momentum, $\langle p_{\rm{T} }\rangle$, could probe the nature of the phase transition and seek evidence for temperature fluctuations. In this talk, event-by-event $\langle p_{\rm{T} }\rangle$ and higher order fluctuations of charged particles produced in pp collisions at $\sqrt{s}=5.02$ TeV, Xe--Xe collisions at $\sqrt{s_{\rm{NN}}}=5.44$ TeV, and Pb--Pb collisions at $\sqrt{s_{\rm{NN}}}=5.02$ TeV are reported as a function of charged-particle multiplicity using the ALICE detector at the LHC.

Non-statistical fluctuations are observed in all collision systems, indicating correlated particle emission. The central Pb--Pb collisions show a significant reduction in the fluctuation compared to the peripheral collisions and are in qualitative agreement with previous measurements in Pb--Pb collisions at $\sqrt{s_{\rm{NN}}}=2.76$ TeV. This effect is discussed in view of radial flow effects and/or the presence of mini-jets. The positive skewness of the $\langle p_{\rm{T} }\rangle$ fluctuation, which has been proposed as an essential consequence of the hydrodynamic evolution of the produced fireball in heavy-ion collisions, is observed. The kurtosis is found to decrease with increasing system size and saturates at the Gaussian expectation for most central Pb--Pb collisions. To investigate the impact of jets in the measurement of the $\langle p_{\rm{T} }\rangle$ fluctuations, a transverse spherocity study was performed and found that jetty events show higher fluctuations compared to isotropic events. The results are compared with widely used Monte Carlo event generators.

Speaker: Ms Bushra Ali (Aligarh Muslim University (IN))

ProbingQGP_MpTFluc_PosterVer2.pdf

17:30 Probing viscous effects with identified particles in pp, p—Pb and Pb—Pb collisions

Two-particle transverse momentum correlator $G_{2}$ was measured based on data collected from Pb--Pb collisions at $\sqrt{s_{\rm NN}} = 2.76\;\text{TeV}$. The evolution of the longitudinal width of the $G_{2}$ correlator vs. collision centrality nominally provides information about the specific shear viscosity, $\eta/s$, of the medium formed in the collisions. The $G_{2}$ correlator was also measured in pp and p--Pb collisions at $\sqrt{s} = 7\;\text{TeV}$ and $\sqrt{s_{\rm NN}} = 5.02\;\text{TeV}$, respectively, to investigate the presence of viscous effects in these smaller systems. No longitudinal broadening was observed. These smaller systems are either too small or too short-lived to manifest viscous effects based on the $G_{2}$ observable.

In this contribution, identified charged particles $G_{2}$ in pp, p--Pb, and Pb--Pb collisions at the same nucleon--nucleon collision energy ($\sqrt{s_{\rm NN}} =$ 5.02 TeV) in different multiplicity classes measured with the ALICE detector are presented. The results shed light on potential mass-ordering effects and system size dependence, leaving aside collision energy dependent effects.

Speaker: Sumit Basu (Lund University (SE))

17:30 Production of $\Sigma$ baryons as a function of multiplicity in pp collisions at the LHC with ALICE

The strangeness content of the final state in ultrarelativistic heavy ion collisions has been studied through measurements of kaons, Λ, Ξ and Ω baryons in pp, pA and AA collisions. $\Sigma$ baryons contain a single strange quark and form a triplet, with the charge (+, 0, -) depending on the light quark content. In a thermal model scenario, these states are abundant enough to carry a significant fraction of the strangeness produced in the collision. However, the experimental measurement is challenging, and to date only $\Sigma^{0}$ in 7 TeV pp collisions have been measured by ALICE, while few other experiments have measured the charged states at lower pp($\rm p \bar{p}$) collision energies.
A number of methods to identify charged Σ have developed during the LHC Run 2. The decay $\Sigma^{+}$ -> p $\pi^{0}$ can be reconstructed via the direct detection of the proton and the two gammas from the $\pi^{0}$ decay, either through them both converting to $\rm e^{+}e^{-}$ pairs or through one converting and the other being reconstructed in the Photon Spectrometer (PHOS). Additionally, a method to detect anti-neutrons in the PHOS has been developed. This allows the (anti-$\Sigma$)$^{\pm}$ -> anti-n + $\pi^{\pm}$ decays to be reconstructed. We present the transverse momentum spectra of $\Sigma^{+}$ and its charge conjugate anti-particle, in both minimum bias and high-multiplicity triggered pp collisions at $\sqrt{s} = 13$ TeV. These are then compared to the latest MC simulations, including the tunes of PYTHIA, which best reproduce the existing hyperon data.
With the advent of Run 3, ALICE has improved the capability of the Inner Tracker, allowing the detection of the charged $\Sigma$ particle with the reconstruction of its decay after traversing several detector layers. The performance of this novel reconstruction method is discussed. In addition, the prospects for measurements of the interaction between $\Sigma$ and other baryon species will be discussed together with the implications for constraining the neutron star equation of state.

Speaker: Benedict Heybeck (Goethe University Frankfurt (DE))

Poster_QM23_Heybeck.pdf

17:30 Production of light flavor particles as a function of the Underlying Event activity in small and large collision systems with ALICE

Measurements of high-multiplicity pp and pA collisions at LHC energies have revealed that these small collision systems exhibit some quark-gluon plasma-like features, such as collective behaviour and strangeness enhancement, formerly thought to be achievable only in nucleus-nucleus collisions. A proposed method to narrow down the origin of these phenomena is to study the effect of MultiParton Interactions (MPIs). Although the MPIs cannot be measured directly, the event observable RT, quantifying the magnitude of the underlying event (UE), has been suggested as an experimental proxy.

New final results of the charged particle production as a function of RT 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, relative to the hard scattering. The energy dependence of RT distributions in pp collisions at √s = 2.76, 5.02, 7 and 13 TeV is reported, exploring the Koba-Nielsen-Olesen (KNO) scaling properties of the multiplicity distributions of the UE. In addition, new results on the production of identified hadrons (π, K, p) as a function of RT in pp collisions at √s = 13 TeV are presented to explore the particle species dependence. All the above results are compared with predictions from QCD-inspired Monte Carlo event generators such as PYTHIA and EPOS-LHC.

Speaker: Omar Vazquez Rueda (University of Houston (US))

QM23_poster.pdf

17:30 Production of pion, kaon, proton in high multiplicity pp collisions at 13 TeV at ALICE experiment

Light-flavor hadrons constitute the bulk of the particles produced in high energy hadronic collisions at LHC. Recent studies show that in high multiplicity pp and p—Pb collisions at LHC energies, particle production exhibits features that mimic the behaviors observed in AA collisions (e.g., mass-dependent pT hardening and strangeness enhancement). These features are a typical sign of the formation of a deconfined state of matter (the quark—gluon plasma). Measuring the light-flavor hadron transverse momentum spectra, integrated yields, and relative abundances in different collision systems provides crucial information on the collective evolution and hadronization process of the system.
This poster will present the new ALICE results on the pion, kaon, and proton production in high multiplicity event class in pp collisions at $\sqrt(s)$=13 TeV.

Speaker: Rajendra Nath Patra (University of Jammu (IN))

ID377_ALICE_HMpp13TeV_spectra_QM_2023.pdf

17:30 Projected 3-point Energy Correlator measurements in jets in p-p at $\sqrt{s_{NN}}$ = 13TeV with ALICE

The sequential clustering of particles into jets offers an algorithmic connection of hadrons to the partons of the radiation shower. Jet substructure allows us to access the radiation history of a jet thereby providing a useful avenue to probe QCD through different energy scales. The N-point Energy Correlator (ENC) is a recently proposed observable that highlights this feature of jets as a multi-scale object. The evolution of jets from the perturbative (partonic) to non-perturbative (hadronic) regimes is imprinted in the slopes of the ENC. Experimentally, the ENC is defined as the energy-weighted cross-section of N particles in a jet as a function of their angular separation. This makes the ALICE detector suitable for these measurements due to its excellent momentum and track resolution. Theoretical calculations have shown excellent agreement with the recent measurement of the two-point energy correlator (EEC) in jets at ALICE $\sqrt{s_{NN}}$ = 5.02 TeV in p-p as well as in jets at STAR $\sqrt{s_{NN}}$ = 200 GeV in p-p. Extending the EEC to the three-point correlator (EEEC) is the first step in extending the scaling information of the energy flow to a shape dependence. An intermediate step to achieving this goal is measuring the projected EEEC (E3C) which retains information about the largest angular scale of the correlation. The motivation to study the E3C is two-fold i) It has been shown theoretically that the projected E3C operators encode the same scaling information as the full E3C, a highly non-trivial property of this observable. ii) Taking ratios of the projected E3C with the EEC may enable us to better access perturbative QCD since it is known that the EECs are not immune to hadronization effects. Moreover, these ratios may offer precision tests of the coupling strength of the strong force, $\alpha_S$. In this poster, we will show the progress towards the first preliminary measurements of the projected E3C with ALICE at $\sqrt{s_{NN}}$ = 13 TeV in p-p. We will also present simulation studies that extend these measurements to heavy-ion collisions. Specifically, we will show the sensitivity of ENCs in jets to the heavy-ion background to motivate further measurements in the quark-gluon plasma.

Speaker: Ananya Rai (Yale University (US))

ARai_posterQM2023f.pdf

17:30 Prospects for light (anti)nuclei measurements in jets in Run 3 with ALICE

The production of light (anti)nuclei in high-energy hadronic collisions has been studied in depth with the ALICE experiment at the LHC. Despite this, the production mechanism of light (anti)nuclei is still not well understood and remains a highly-discussed topic in the scientific community. One of the phenomenological models typically used to describe the hadronization process is the coalescence model. In this model, if the nucleons at kinetic freezeout are close in phase space and match their spin state they can bind and form a nucleus. More advanced coalescence model uses the Wigner formalism for the bound state. A prediction of this model is an enhanced coalescence probability of nuclei in jets with respect to the underlying event in small collision systems. To test this prediction, ALICE has published a work where the (anti)deuteron coalescence parameter in and out of jets is measured in pp collisions, and the same study has been performed in p-Pb collisions, observing in both cases such enhancement. In this poster, the prospects for light (anti)nuclei measurements in jets and in underlying event during the Run 3 will be presented, considering the developments along this research line and the expected precision obtained thanks to the integrated luminosity that will be collected.

Speaker: Marika Rasa (University and INFN Catania)

Poster_QM_Rasa.pdf

17:30 Prospects for open heavy-flavour and quarkonium measurements with NA60+

The NA60+ experiment, proposed for data taking in the next years, aims to investigate the high baryochemical potential region of the QCD phase space diagram, exploiting the large intensity of CERN SPS beams.

NA60+ will have the possibility to access the high $\mu_{B}$ region of the QCD phase diagram, by studying rare probes via a beam-energy scan with PbPb and p-A collisions in the interval 6.3 < $\sqrt{s_{NN}}$ < 17.3 GeV.

In this talk, we will focus on the prospects for measurements of hidden and open charm. Open charms will be measured in their decays into charged hadrons, reconstructed from tracks in the silicon detectors of the vertex telescope.
High-precision measurements of the yield of $D^{0}$, $D^{+}$ and $D^{+}_{s}$ mesons, and of $\Lambda^{+}_{c}$ baryons, will allow us to constrain the transport properties of the QGP and the charm-quark hadronisation.

Charmonium states will be accessed from their dimuon decay, reconstructed by matching muon tracks in the vertex telescope and in the muon spectrometer. The $J/\psi$ and $\psi(2S)$ measurements at various collision energies will allow us to identify the onset of charmonium suppression in a deconfined medium, correlating this observation with the temperature of the system, as measured, always by NA60+, via thermal dimuons.

The competitiveness and complementarity of NA60+ in the landscape of the experiments foreseen at other facilities in the next decade will also be discussed.

Speaker: Roberta Arnaldi (Universita e INFN Torino (IT))

QM23_Poster_Roberta.pdf

17:30 Proton-Endcap Electromagnetic Calorimeter of the ePIC Experiment at Electron-Ion Collider

The proton-endcap Electromagnetic Calorimeter (pECal) of the ePIC experiment at the future Electron-Ion Collider (EIC) will cover the pseudorapidity range of 1.3 $< \eta <$ 4 in the hadron-going direction. In semi-inclusive deep inelastic scattering, the pECal is essential for measuring jets and heavy quarks in the hadron-going direction. These physics measurements require the pECal to have a moderate energy resolution, fine granularity, and a compact structure. We will present the current design of the pECal, a sampling calorimeter with a W-powder/ScFiber (W/ScFi) structure initially developed at UCLA. The W/ScFi detector design has unique features, such as a close-to-one e/h ratio suitable for hadron compensation, which is required for jet measurements. The simulated pECal performances match the requirements of the EIC scientific program very well. This design has been adopted by the current EIC detector plan (ePIC) and implemented in the ePIC software frameworks. I will discuss the design, advantages, and performances of the W/ScFi pECal detector based on the results of GEANT4 simulations. I will present the performances of the pECal in terms of separation of high-energy $\pi^0$ decay photons, identification of electrons, and measurements of jets and heavy-flavor jets.

Speaker: Dr ZHONGLING JI (UCLA)

epic-pecal.pdf

17:30 Proton-proton femstoscopy in Au+Au collisions at $\sqrt{s_{NN}}$ = 3.2 GeV

Correlation function of baryons has been used in heavy-ion collisions to study the space-time structure, the dynamical evolution of the particle-emitting source, and final state interactions.

In this poster, we will present correlation functions of protons in Au+Au collisions at $\sqrt{s_{NN}}$ = 3.2 GeV from the second phase of the beam energy scan (BES-II) at STAR. The Lednicky-Lyuboshitz model is used to fit the proton correlation function. The scattering length and effective range of the strong interaction and the source size are extracted and their physics implications will be discussed. We will also discuss the energy dependence of the source size by comparing with the published results of 200 GeV.

Speaker: Yu Zeng (Central China Normal University)

Yu_Zeng_QM2023_poster_v4.pdf

17:30 Pseudorapidity densities of charged particles with transverse momentum thresholds in pp collisions at $\sqrt{s}$ = 5.02 and 13 TeV with ALICE

The pseudorapidity density of charged particles with different values of minimum transverse momentum ($p_\mathrm{T}$) thresholds of 0.15, 0.5, 1, and 2 GeV/c is measured in pp collisions at $\sqrt{s} =$ 5.02 and 13 TeV with the ALICE Run 2 set-up. The study is carried out for inelastic collisions with at least one primary charged particle having a pseudorapidity ($\eta$) within ±0.8 and $p_\mathrm{T}$ larger than the corresponding threshold. Implementing $p_\mathrm{T}$ thresholds provides the unique possibility to compare to results published from other LHC experiments, such as ATLAS and CMS. The measurements are also compared to PYTHIA 8, EPOS-LHC and EPOS 3 event generators.

Speaker: Jeongsu Bok (Pusan National University (KR))

QM23_Poster_JeongsuBok_draft3.pdf

17:30 QCD mesonic screening masses using Gribov quantization

Chiral symmetry is lost at low temperatures, and pions are massless in the chiral limit; there is no longer any screening mass. The screening mass of mesons approaches the standard value of $2 \pi T$ at high temperatures. The screening masses of mesons provide a gauge invariant and definite order parameter of chiral symmetry restoration. Different mesonic correlation lengths for flavor non-singlets, at least up to NLO, are well-defined gauge invariant physical quantities calculated earlier using the perturbative resummation techniques. It was found that these NLO corrections are small and come with a positive sign. The lattice simulation results match the existing perturbative results only in the high-temperature regime. There needs to be more clarity between the lattice results and the theoretical calculations at low temperatures, as the perturbative expansion fails at low temperatures. One of the ways to probe the low-temperature region is by using the non-perturbative Gribov resummation. We have studied the spatial correlation lengths $\zeta$ of various mesonic observables using the Gribov action in quenched QCD and for $(2+1)$ flavor QCD. In particular, we have calculated the non-perturbative NLO correction to the meson screening mass using the Gribov propagator. This correction has been calculated by following the analogies with the NRQCD effective theory, a well-known theory for studying heavy quarkonia at zero temperature.

Speaker: Mr SUMIT N/A (IIT Roorkee)

17:30 Quantifying the underlying event for jet measurements with sPHENIX

The sPHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) is designed to study the properties of quark-gluon plasma (QGP) created in heavy-ion collisions. sPHENIX is equipped with tracking detectors and calorimetry, which allow for precise measurements of particles produced in the collision. In particular, the electromagnetic and hadronic calorimeters are crucial for reconstructing and determining the energy of jets. High-energy jets produced by hard scatterings in heavy-ion collisions provide valuable insight into how partons interact and lose energy in the QGP. In sPHENIX, jets are reconstructed by clustering energy from all three layers of the calorimeter. However, the presence of the underlying event (UE), which refers to all particles produced from sources other than the hard-scattering process, can lead to the overestimation of jet energy and distortion of jet properties. Therefore, it is crucial to have an accurate quantification and subtraction of UE in jet measurements. This poster will present the status of sPHENIX event-by-event estimation of the UE as a function of event activity throughout the 2023 data-taking period and plans for extracting measurements with underlying event-subtracted reconstructed jets.

Speaker: MUHAMMAD Shumail Khan

Poster_1030GeV_V11 2.pdf

17:30 Quantum Regeneration of Bottomonia in Heavy Ion Collisions

For decades, heavy quarks and their bound states have served as ideal experimental and theoretical probes of the medium formed in heavy ion collisions. Specifically, suppression of heavy-heavy bound states in heavy ion relative to proton-proton collisions was postulated as a strong signal of the formation of a deconfined quark gluon plasma. More recently, the use of effective field theories (EFTs) and the formalism of open quantum systems (OQS) has allowed for great advances in first principles descriptions of in-medium heavy-heavy bound states. Using EFTs, one can systematically exploit the hierarchies of scale of the combined system to arrive at an effective description valid in a particular regime while the OQS formalism enables a quantum description of a system evolving coupled to and out of equilibrium with an environment. In this talk, we present recent results obtained by solving the Lindblad equation derived using the EFT potential nonrelativistic QCD and the OQS formalism describing the in-medium evolution and suppression of the Υ(1S), Υ(2S) and Υ(3S) states. We emphasize our good agreement with experimental data from the ALICE, ATLAS and CMS collaborations and the necessity of quantum regeneration to accurately describe the suppression of the excited states and double ratios thereof.

Speaker: Peter Vander Griend

vander_griend_poster.pdf

17:30 Quarkonia measurements in heavy ion collisions with the sPHENIX experiment

Quarkonia measurements in heavy-ion collisions are important for understanding both initial-state effects on heavy-quark production and final-state interactions between heavy quarks and the hot and dense nuclear matter created in high-energy heavy-ion collisions.

The sPHENIX experiment at RHIC will begin its commissioning and first Au+Au data-taking run in 2023, and plans to measure the production of $\Upsilon$'s and high pT J/$\psi$'s in the di-electron channel in this dataset as well as in future p+p, p+Au and Au+Au running. The status of the relevant detectors and their performance for di-electron measurements will be presented and compared to what is expected from a Monte Carlo simulations. Analysis prospects and future plans will also be discussed.

Speaker: Alexandre Lebedev (Iowa State University (US))

Quarkonia measurements QM-2023 poster v2.pdf

17:30 Quarkonium polarization in a vortical medium

We examine in detail the mass, lifetime and spin structure of quarkonium in a rotating vortical medium, where the quark spin is not necessarily aligned with the vortex.
After justifying this set-up in terms of spin hydrodynamics, and outlining the expected dependence of spin and vorticity, we examine the mass, lifetime and spin density matrix of quarkonium.
Our analysis implies a novel distillation-based mechanism for spin-alignment generation (which could also apply to the phi if one considers it a quarkonium state) as well as experimental probes of spin-vorticity non equilibrium.

Based on arXiv:2305.02985

Speaker: Paulo De Moura (University of Campinas)

Paulo_DE_MOURA_QM2023.pdf

17:30 Quarkonium production and polarization in pp collisions with ALICE

Quarkonium production in high-energy hadronic collisions is sensitive to both perturbative and non-perturbative aspects of quantum chromodynamics (QCD) calculations. Indeed, the production of the heavy-quark pair is described by perturbative QCD while the formation of the bound state is a non-perturbative process, treated in different ways by available theoretical models. Quarkonium polarization measurements provide also stringent tests of theoretical approaches, as this observable strongly depends on the quarkonium production mechanism at play. Another way to provide constraints on quarkonium production mechanisms is by looking at the production of J/$\psi$ inside jets. For instance, quarkonium production in a parton shower predicts that J/$\psi$ mesons are rarely produced in isolation, contrary to expectations from direct quarkonium production via parton-parton scattering. The measurement of quarkonium production and polarization in pp collisions can also provide a reference for investigating the fate of charmonium in the quark-gluon plasma formed in nucleus-nucleus collisions. ALICE can measure inclusive quarkonium production down to zero transverse momentum ($p_{\rm{T}}$), at forward rapidity (2.5 <$\it{y}$< 4) and midrapidity (|$\it{y}$|< 0.9). Prompt and non-prompt charmonium separation is performed at midrapidity down to low $p_{\rm{T}}$. In this contribution, we will report on recent quarkonium results in pp collisions at $\sqrt{s}$ = 13 TeV, including Υ(nS) cross section measurements and Υ(1S) polarization at forward rapidity, as well as the prompt and non-prompt J/$\psi$ production in jets at midrapidity. The status of new J/$\psi$ and $\psi$(2S) polarization analyzes at $\sqrt{s}$ = 13 TeV and forward rapidity will be shown. Finally, the status of new ongoing quarkonium production analyses using the Run 3 data at $\sqrt{s}$ = 13.6 TeV will be shown both at mid and forward rapidities. Results will be compared with available models.

Speaker: Deekshit Kumar (Department of Atomic Energy (IN))

17:30 Reconstructing Jet History with Machine Learning

In this study, we investigate if machine learning can be used to reconstruct aspects of jet history. The space-time evolution of a jet shower is directly linked to local properties of the surrounding medium. Extracting the evolution poses a challenge, since experimentally we only have access to the final state hadron momenta. On the other hand, Monte Carlo simulations model the jet history in great detail. Here, we explore if the known history in simulations can be reconstructed by looking only at final state particles using machine learning. We consider jets in vacuum, generated by the JETSCAPE framework. We work with output data for both final state partons and final state hadrons. We use these datasets to train neural networks to predict the maximum opening angle $\theta_{\max}$ and the jet splitting function $z_G$ -- related to transverse and longitudinal jet structure respectively -- in the simulation. We compare the predictive powers of the parton data and the hadron data, to understand if and how information is lost during hadronization. Finally, we investigate ways to quantify and reduce information loss due to hadronization.

Speaker: Arjun Sengupta

QM_2023_Poster_2023-09-07.pdf

17:30 Repulsive $\Lambda$ potential at high densities examined from heavy-ion collision and hypernuclear data

We investigate the validity of the repulsive $\Lambda$ potential at high densities which suppresses $\Lambda$ in dense neutron star matter by investigating whether it reproduces the heavy-ion collision and the hypernuclear data.

In the 20th cenury, $\Lambda$ baryon was predicted to appear in neutron star matter at $2$-$4\rho_0$ from the hypernuclear spectroscopy and the phenomenology of dense neutron star matter. However, most of the hyperonic matter equations of state cannot support the observed massive neutron stars (hyperon puzzle). One of the proposed scenarios is that the $\Lambda$NN three-body force generates enough repulsion to suppress $\Lambda$s in the dense nuclear matter. From chiral effective field theory, a $\Lambda$ potential that satisfies this scenario has been obtained (Gerstung et al. (2020)). However, the density dependence of this potential has not been verified using experimental data.

In this talk, we will report that the above $\Lambda$ potential reproduces the experimental data of heavy-ion collisions and $\Lambda$ hypernuclei. We have found that the repulsive $\Lambda$ potential explains both data on the $\Lambda$ directed flow of heavy-ion collisions at $\sqrt{s_{NN}}=3.0$−$20~{\rm GeV}$ within a relativistic quantum molecular dynamics implemented in JAM2 (Nara et al. (2022)), and the $\Lambda$ binding energy of hypernuclei by the Skyrme-Hartree-Fock method with spherical symmetry (Jinno et al. in prep.). We conclude that the repulsive $\Lambda$ potential with two- and three-body force can be a solution for the hyperon puzzle.

On the other hand, it is found that more attractive potential can also explain the both heavy-ion collision and hypernuclear data. To discriminate the repulsive $\Lambda$ potentials to attractive ones, we will also examine ${}^3_\Lambda {\rm H}$ directed flow of heavy-ion collisions, which is recently measured by the STAR collaboration (STAR, arXiv:2211.16981) and is overestimated by the old version of JAM.

Speaker: Asanosuke Jinno

QM2023_AJ.pdf

17:30 Results on Breit-Wheeler Process in Heavy-Ion Collisions and its Application to Nuclear Charge Radius Measurements

In ultra-relativistic heavy-ion collisions, strong electromagnetic fields arising from the Lorentz-contracted, highly charged nuclei can be approximated as a large flux of high-energy quasi-real photons that can interact via the Breit-Wheeler process to produce $e^{+}e^{-}$ pairs. The collision energy dependence of the cross section and the transverse momentum distribution of dielectrons from the Breit-Wheeler process in heavy-ion collisions are calculated with lowest-order EPA-QED. Within a given experimental kinematic acceptance, the cross section is found to increase while the pair transverse momentum decreases with increasing beam energy. The corresponding results are also compared with STAR measurements, which are consistent with each other and found to be sensitive to the nuclear charge distribution and the infrared-divergence of the ultra-Lorentz boosted Coulomb field. Following this approach we demonstrate that the experimental measurements of the Breit-Wheeler process in ultra-relativistic heavy-ion collisions can be used to quantitatively constrain the nuclear charge radius. The extracted parameters show sensitivity to the impact parameter dependence, and can be used to study the initial-state and final-state effects in hadronic interactions.

Speaker: Xiaofeng Wang (Shandong University)

poster_QM2023_XiaofengWang.pdf

17:30 Revisiting Initial Condition Modeling of Heavy Ion Collisions with Bayesian Parameter Estimation Using the latest RHIC and LHC data

The transport properties of the quark-gluon plasma, which is produced in heavy-ion collisions, provide crucial information about quantum chromodynamics (QCD). Bayesian analysis has been highly effective in constraining QCD matter properties [1, 2]. When combined with additional flow observables, LHC Pb-Pb data at 5.02 and 2.76 TeV have significantly reduced the uncertainties [2]. However, our latest studies have revealed shortcomings in the current modeling of initial conditions and difficulties in describing RHIC Au-Au collision data. In this talk, we will discuss our findings and new results aimed at improving the modeling of initial conditions in heavy-ion collisions.

[1] Nature Physics 10.1038/s41567-019- 0611-8 (2019)

[2] Phys.Rev.C 104 (2021) 5, 054904

[3] Phys.Lett.B 835 (2022) 137485

Speaker: Maxim Virta (University of Jyväskylä)

17:30 Search for medium-induced jet quenching effects in high-multiplicity pp collisions with ALICE

Collisions of small systems show signatures suggestive of collective flow associated with QGP formation in heavy-ion collisions. Jet quenching is also a consequence of QGP formation, but no significant evidence of it in small systems has been found to date. Measuring or constraining the magnitude of jet quenching in small systems is essential to determine the limits of QGP formation. The ALICE collaboration presents a broad search for jet quenching in high multiplicity (HM) pp collisions at $\sqrt{s} = 13$ TeV, based on several observables: the semi-inclusive acoplanarity distribution of jets recoiling from a high-$p_{\text{T}}$ hadron (h+jet); di-hadron correlations; and intra-jet measurements. Marked broadening of the h+jet acoplanarity distribution is observed in HM compared to minimum-bias (MB) events, which could arise from jet quenching. Both data and PYTHIA simulations suggest that this broadening arises from a generic bias of the HM selection towards multi-jet final states. In contrast, the di-hadron correlations between low-momentum particles exhibit azimuthal narrowing in HM relative to MB events, which are described by PYTHIA simulations and might arise from a similar HM bias. We also report the average charged-particle multiplicity and jet fragmentation functions in HM and MB-selected populations, whose differences are qualitatively described by PYTHIA. We discuss the implications of these results for the understanding of collective effects and jet quenching in small systems.

Speaker: Dong Jo Kim (University of Jyvaskyla (FI))

QM23_jetsinsmallsystem_ALICE_djkim.pdf

QM23_v6_djkim.pdf

17:30 Search for the Chiral Magnetic Effect by Event Shape Engineering as a Function of Invariant Mass in Au+Au Collisions at $\sqrt{s_{NN}}$ = 200 GeV from STAR

Chiral Magnetic Effect (CME) is a phenomenon in which electric charge is separated by a strong magnetic field from local domains of chirality imbalance and parity violation in quantum chromodynamics (QCD). The CME-sensitive observable, charge-dependent three-point azimuthal correlator $\Delta\gamma$, is contaminated by a major physics background proportional to the particle elliptic anisotropy ($v_{2}$). In this contribution, we report a fresh investigation of charge separation in Au+Au collisions at $\sqrt{s_{\rm NN}}=200$ GeV with the STAR detector using the Event Shape Engineering (ESE) approach [1]. Our approach has several novel aspects, such as using three subevents to identify dynamical fluctuations of $v_2$ by using subevent different from particles of interest for the ESE selection. Since the CME is a low-$p_{\mathrm{T}}$ phenomenon, we further apply the ESE differentially to the $\Delta\gamma$ as a function of the pair invariant mass ($m_{inv}$), particularly at lower $m_{inv}$, which is dominated by a larger fraction of low-$p_{\mathrm{T}}$ pions. We extract the signal as the intercept by projecting $\Delta \gamma$ to zero $v_{2}$, both integrated over inclusive mass and at low mass. Our results suggest non-zero intercept with an approximately 2$\sigma$ significance, which we compare to the published results from the spectator/participant measurement [2]. The extracted signals, highly sensitive to the CME, may still be contaminated by residual flow as well as nonflow contributions
in the $v_{2}$ measurement and in the three-particle correlator [3]. We investigate these contaminations in the ESE measurement, and also report measurement using the zero-degree calorimeter (ZDC) that largely supresses the nonflow contamination. We discuss the implications of our results and perspectives with the expected 10-fold increase in statistics from the RHIC runs in the years 2023 and 2025.

[1] J. Schukraft, A. Timmins, and S.A. Voloshin, Phys. Lett. B719 (2013) 394.
[2] M.S. Abdallah et al. (STAR Collaboration), Phys. Rev. Lett. 128, 092301.
[3] Y. Feng, J. Zhao, H. Li, H.-j. Xu, and F. Wang, Phys. Rev. C105 (2022) 024913.

Speaker: Han-Sheng Li

poster_han_sheng_li_v5.pdf

17:30 Self-consistent spectral properties of quarks and mesons in a chiral quark model

We present a study of the spectral properties of the quark and meson excitations within the Nambu--Jona-Lasinio model. The pertinent spectral functions are obtained by solving self-consistently the Dyson equation for the quark propagator at the one-loop level and the Bethe-Salpeter equation for the quark-antiquark T-matrix, which describes mesons as dynamically generated bound states. The self-consistent solutions are used to calculate the thermodynamic potential and the chiral condensate dependence on the temperature, which shows that the mesonic thermal excitations govern the chiral condensate melting at low temperatures.

Speaker: Hitansh Shah

QM_Poster_v1.pdf

17:30 Shear Viscosity at High Chemical Potentials

Transport coefficients, such as viscosity, can be calculated theoretically in weakly coupled quantum field theory, and present interesting information about hydrodynamic models of heavy-ion collisions. We present results for shear viscosity calculations at almost leading order in weakly coupled QCD in a regime of high baryon density, where the chemical potentials are greater than the temperature. In previous work, we have shown that shear viscosity at leading log order in this regime is dominated by quark scattering.

Speaker: Ms Isabella Danhoni

posterQM.pdf

17:30 Simulation studies of the pair spectrometer luminosity detector for the ePIC experiment at the EIC

A crucial component to the Electron Ion Collider (EIC) program is the collider luminosity, with a target absolute (relative) uncertainty of less than 1% (exceeding 10⁻⁴ in precision). The luminosity determination will be achieved employing two complementary approaches, one by direct detection of bremsstrahlung photons and another using a Pair Spectrometer (PS) which utilizes e+e- conversions of the bremsstrahlung photons. The anticipated higher luminosity at the EIC than HERA, which achieved a precision of ≈ 2%, presents several new challenges that necessitate major improvements to the PS baseline design. More specifically, the novel design now includes a thin converter foil, sweeper and analyzer magnet, a helium/vacuum chamber, tracking layers, and modern EM calorimeters. We resent estimates to the luminosity uncertainties for the electron Proton-Ion Collider (ePIC) experiment at the EIC through dedicated simulations using the PS.

Speaker: Aranya Giri (University of Houston)

AranyaGiri_Poster_QM23_UHID_2077644.pdf

17:30 sPHENIX DAQ and Trigger

The new sPHENIX detector at RHIC will begin commissioning with Au+Au collisions at 200 GeV in Spring 2023. The sPHENIX trigger system is paramount to the success of the sPHENIX physics program. A system of custom digital Local Level-1 electronics (LL1) will enable trigger primitive generation related to interaction selection, jets, photons, hadrons, and Upsilons to pass to the Global Trigger (GL1). A single LL1 board compresses primitives from up to 1536 detector readout channels and produces a digest of event classifications that will be passed to the GL1. The Minimum Bias Detector (MBD) trigger will provide the primary selection criterion of vertex determination, triggering on hits in the high-rapidity region covered by the MBD. This will be pivotal in synchronizing the data-acquisition of separate detectors to collisions at RHIC. Next, the jet, photon, and hadron trigger will search for windows of high energy deposition in the electromagnetic (EMCAL) and the hadronic calorimeter (HCAL), seeking out collisions with jet production. For this trigger an additional set of LL1 electronics are used to collect information from the entire calorimeter system. Finally the electron pair trigger is designed to capture decayed Upsilons and will invoke a peak-finding algorithm to find pair electrons deposited into the EMCAL. This poster overviews the design and strategy of the LL1 trigger and will discuss the performance of the trigger and data acquisition systems and the status of trigger efficiency studies based on year-1 data, compared to emulated data from sPHENIX simulations.

Speaker: Daniel Lis

17:30 sPHENIX Hadronic Calorimeter Cosmic Muon Calibration

The sPHENIX experiment is comprised of two layers of hadronic calorimeters (HCal). The outer HCal is the outermost layer located outside the solenoid coil, and the inner HCal is positioned between the solenoid magnet and the Electromagnetic Calorimeter. The sPHENIX program, aimed at achieving precise jet measurements and analyzing the microscopic properties of the strongly interacting quark-gluon plasma, requires a well-calibrated energy scale for the calorimeters. This poster will present the advancements made in calibrating both the inner and outer HCals utilizing cosmic ray muons. Energy deposited by muons traversing the sectors is recorded, and events in which muons pass through all scintillator tiles in a tower are selected for analysis. The primary diagnostic is the Most Probable Value (MPV) of the ADC distributions associated with these events. Subsequently, MPVs undergo corrections to account for temperature variations and the tower tiles’ response to LED signals. These corrected MPVs determine the gain of each tower. A Monte Carlo study, based on Geant4 simulations, will establish a reference for the relative calibration of the gains on a tower-by-tower basis. The bias voltage applied to the silicon photomultipliers (SiPM) will be adjusted to fine-tune the gain and eliminate the outliers, resulting in a more accurate calibration of the HCals. This calibration process is essential for understanding the calorimeter response and contributes broadly to the sPHENIX experiment’s goals resulting in a more accurate calibration of the HCals. This calibration process is essential for understanding the calorimeter response and contributes broadly to the sPHENIX experiment’s goals.

Speaker: Hanpu Jiang (Columbia University)

Calibrating_the_sPHENIX_Hadronic_Calorimeter_with_Cosmic_Ray_Muons_Hanpu Jiang.pdf

17:30 sPHENIX MVTX Pixel Detector Internal Alignment with AI-ML Approach

The sPHENIX experiment has achieved a major milestone with the construction and installation of the cutting-edge three-layer Monolithic-Active-Pixel-Sensor (MAPS) based VerTeX detector (MVTX) in April 2023, in preparation for first beam in Spring 2023. The MVTX is the innermost tracking detector, boasting a spatial resolution of 5 $\mu$m and covering 2.5-4.0 cm radially, and a pseudorapidity range of $|\eta|$ <2. With 432 ALPIDE sensors, each containing approximately 0.5M 27 $\mu$m x 29 $\mu$m pixels in an area of 1.5cm x 3.0cm, determining the position of each pixel in the sPHENIX global coordinate system presents a significant challenge. Our first step is to establish the relative position of each sensor in the local MVTX coordinates with an accuracy of better than 5 $\mu$m. To this end, we have developed an AI-ML-based approach to determine the deviations of each sensor's position and orientation from the ideal geometry (dx, dy, dz) in translation and (d$\alpha$, d$\beta$, d$\gamma$) in rotation. In this presentation, we will showcase the status of the MVTX detector's internal alignment based on first-year commissioning data, and discuss its impact on heavy flavor measurements

Speaker: Jaehyun Kim (Yonsei University (KR))

sPHENIX_MVTX_Pixel_Detector_Internal_Alignment_with_AI-ML_Approach_JHKim_QM23poster_20230901.pdf

17:30 Spin alignment of vector mesons by glasma fields

We explain how spin alignment of vector mesons can be induced by background color fields. Our study is based on the quantum kinetic theory of spinning quarks and antiquarks and incorporates the relaxation of the dynamically generated spin polarization. The spin density matrix of vector mesons is obtained by quark coalescence via the Wigner function and kinetic equation. Our approach predicts a local spin correlation that is distinct from the non-local expressions previously obtained in phenomenological derivations. We estimate the magnitude of such local correlations in the glasma model of the preequilibrium phase of relativistic heavy ion collisions. It is found that the resulting spin alignment could be greatly enhanced and may be comparable to the experimental measurement in order of magnitude. We further propose new phenomenological scenarios to qualitatively explain the transverse-momentum and centrality dependence of spin alignment in a self-consistent framework.

Speaker: Di-Lun Yang (Institute of Physics, Academia Sinica)

QM_2023_spin.pdf

17:30 Spontaneous Transverse Λ and Λ Hyperon Polarization Measurements at LHC

Transverse Λ polarization observed over four decades ago contradicted expec-
tations from early leading-order perturbative QCD calculations. Measurements
of Λ polarization from unpolarized pp and pA collisions have been previously
observed to increase as a function of xF and pT up to a few GeV range and
approximately independent of beam energy. Recent studies have linked polar-
ization to the process of hadronization, which describes how particular hadrons
are formed from scattered quarks and gluons. The high energy of the LHC
and the coverage and precision measurement possibilities from LHCb forward
geometry are ideal for studying hyperon polarization as a function of both pT
and xF . The status and prospects of Λ and Λ polarization measurements in pp,
pPb, Pbp, and fixed-target pNe collisions at LHCb are presented

Speaker: Cynthia Nunez (University of Michigan (US))

QM23_Poster_CNunez.pdf

17:30 Statistical Hadronization Model Calculations of Heavy Flavor Hadron Production in Relativistic Heavy-Ion Collisions at RHIC and the LHC

The validity of the Statistical Hadronization Model (SHM) has been successfully tested to adequately reproduce hadronic particle abundances over nine orders of magnitude in high energy collisions of heavy ions. Assuming a thermally equilibrated system, experimental particle yields at RHIC and the LHC serve as an anchor for the determination of common freeze-out parameters in the QCD phase diagram -- namely, the baryon chemical potential ($\mu_{\mathrm{B}}$) and the chemical freeze-out temperature ($T_{\mathrm{ch}}$) -- via thermal fits in the SHM framework. Heavy flavor particle production is of particular interest in heavy ion phenomenology by virtue of the large difference between the mass of the bare heavy quarks and the calculated pseudocritical hadronization temperature. Due to their large masses, heavy quarks are produced in the initial hard partonic scattering of heavy ion collisions. The produced charm and beauty quarks then interact with other constituents of the collision fireball and then potentially thermalize. These heavy quarks can then recombine with the surplus of deconfined light flavor quarks in the Quark-Gluon Plasma generated in a heavy ion collision; where the total number of constituent heavy quarks is assumed to stay constant until hadronization is reached. This thermal-like behavior of final state heavy flavor hadron yields allows for their production to be modeled in the context of the SHM using an additional fugacity parameter. In this contribution, we will show recent thermal fits to single charm hadrons measured in ALICE Pb+Pb Collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV and STAR Au+Au Collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV utilizing the same PDG2016+ hadronic spectrum as our previous work and a modified version of the most recent PDG2022 list. We will additionally show thermal model predictions of heavy quarkonia, and beauty and multi-charm hadron yields as a function of $\sqrt{s_{\mathrm{NN}}}$ and test their sensitivity to different values of $T_{\mathrm{ch}}$ and $\mu_{\mathrm{B}}$.

Speaker: Fernando Flor (Yale University)

SM_FAF_QM2023_Poster.pdf

17:30 Status of the Analyses for the Proton Higher-Order Fluctuations in the STAR Fixed-Target Program from $\sqrt{s_{NN}}=$ 3.2 to 7.7 GeV

Higher-order fluctuations of the net-proton number distributions in heavy-ion collisions are expected to be sensitive to a QCD critical point. These fluctuations can be obtained by measuring various order of cumulants, $C_n$, of the net-proton multiplicity distributions. The collision energy dependence of net-proton $C_4/C_2$ from Beam Energy Scan I hints at a possible enhancement from $\sqrt{s_{NN}}=$ 19.6 GeV to 7.7 GeV across the baseline, while the proton $C_4/C_2$ value at 3~GeV from the Fixed-Target program (FXT) returns to the baseline. These results indicate the importance of filling the gap between 3.0 GeV and 7.7 GeV. The analyses of the remaining FXT data sets are ongoing to fill the gap and to see whether any critical behaviour is observed in the region between 3.2 and 7.7 GeV, although limited acceptance at the top FXT energies complicates these analyses. A status report on the challenges, methods, and statistical significance of these analyses will be presented.

Speaker: Zachary Sweger (University of California, Davis)

Sweger.pdf

17:30 Strange hadron production in d+Au collisions at √sNN = 200 GeV using the STAR detector

Strangeness production has been suggested as a sensitive probe to the dynamics of the deconfined matter created in heavy-ion collisions. Ratios of particle yields involving strange particles are often utilized to study properties of the nuclear matter at freeze-out, such as the strangeness chemical potential and the chemical freeze-out temperature. The $d$+Au collisions bridge the multiplicity gap between $p$+$p$ and Au+Au collisions and can provide insight to the role of event multiplicity in strange hadron production. The study of strange hadrons in $d$+Au collisions can also help to understand their cold nuclear matter effects, a necessary ingredient for interpreting similar measurements in heavy-ion collisions.

In this poster, we will present new measurements on the production of strange hadrons ($K{_S}{^0}$, $\Lambda$) for different rapidity intervals in $d$+Au collisions at $\sqrt{s_{\rm{NN}}} =$ 200 GeV, recorded by the STAR experiment in 2016. We will report transverse momentum ($p_{\rm{T}}$) spectra, $p_{\rm{T}}$ integrated yield dN/dy, average transverse momentum, yield ratios, nuclear modification factors, and rapidity asymmetry ($Y_{\rm{Asym}}$) for these strange hadrons. The physics implications of these measurements on the collision dynamics will be discussed.

Speaker: Ishu Aggarwal

17:30 Strange hadron production in pp collisions with Run 3 data

The ratio between (multi-)strange and non-strange hadron yields increases with the multiplicity of charged particles produced in hadronic collisions, revealing a smooth transition from low multiplicity pp collisions to central Pb-Pb collisions. The microscopic origin of this behaviour, known as strangeness enhancement, has yet to be understood. The data collected by the ALICE experiment during Run 3 provide a unique opportunity to further investigate this phenomenon in high-multiplicity pp collisions, thanks to the unprecedented number of recorded events and to dedicated software filters developed for selecting and storing pp collisions containing strange hadron candidates. This poster presents the first measurement of strange hadron production in pp collisions at $\sqrt{s} = 13.6$ TeV collected by the ALICE experiment in 2022.

Speaker: Chiara De Martin (Universita e INFN Trieste (IT))

QMPoster2023_DeMartin.pdf

17:30 Strangeness production in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 14.6 and 19.6 GeV with the STAR experiment

One main motivation of the Beam Energy Scan (BES) program at RHIC is to search for the QCD critical point and the onset of deconfinement. Strangeness production has been suggested as a sensitive probe to the early dynamics of the deconfined matter created in heavy-ion collisions. Ratios of particle yields involving strange particles are often utilized to study various properties of the nuclear matter, such as the strangeness and baryon chemical potentials at the chemical freeze-out temperature ($\mu_S/T_{\mathrm{ch}}$ and $\mu_B/T_{\mathrm{ch}}$).

Measurements from the first phase of the BES program have indicated potential changes in the medium properties with decreasing collision energy. However, the precision of those measurements is not sufficient to draw definitive conclusions. During BES phase-II (BES-II), STAR has accumulated high statistics data in Au+Au collisions at various energies, which can help reduce the uncertainties in the strange hadron measurements, in particular for the multi-strange hadrons. Benefiting from the iTPC upgrade, the strangeness measurements are now extended from mid-rapidity (|y|<0.5) to a larger rapidity range (|y|<1.0) as well. In this poster, we will present new STAR measurements of strange hadron ($K_s^0$, $\Lambda$, $\bar{\Lambda}$, $\Xi$, $\bar{\Xi}$, $\Omega$, $\bar{\Omega}$) production in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 14.6, 19.6 GeV from BES-II, including transverse-momentum and rapidity spectra, nuclear modification factors, baryon-to-meson and antibaryon-to-baryon ratios. New insights on the collision dynamics will be discussed.

Speaker: Yi Fang

17:30 Strangeness production in Au+Au collisions at √sNN = 14.6 GeV using AMPT and UrQMD model

The production of strange quarks and antiquarks in high-energy collisions of
heavy ions is a significant indicator for the creation of a state of matter known
as Quark-Gluon Plasma (QGP). The QGP is characterized by the liberation of
quarks and gluons from their confinement inside hadrons. Due to their prompt
decay via weak interactions, strange quarks and antiquarks are not present in
normal matter and can only be produced via strong interactions within the
QGP. As the mass of strange quarks and antiquarks is close to the temperature
at which protons, neutrons, and other hadrons dissolve into quarks, they serve
as sensitive probes for studying the conditions, structure, and evolution of the
deconfined state of matter.
The current work will compare the properties of different strange particles,
including Λ, Ξ, and Ω in heavy-ion collisions at varying centralities, using two
models for simulating these collisions: the AMPT and UrQMD models, by com-
paring the yield and the baryon-to- antibaryon ratio of these particles at different
centralities at √sN N = 14.6 GeV from the two models, we can better under-
stand the properties of the QGP medium and gain insight into the differences
and similarities between the two simulation models. The better understanding,
we can better understand the properties of the QGP medium and gain insight
into the differences and similarities between the two simulation models. The
ultimate goal of this analysis is to provide a more comprehensive understanding
of the production of strange particles in heavy-ion collisions and its implications
for the formation and properties of the QGP medium.

Speaker: Ms Pratibha Bhagat (University of Jammu)

17:30 Strangeness Production in Fixed-Target Au+Au collisions at $\sqrt{s_{\rm{NN}}}$ = 7.2 GeV from STAR

Strangeness production is considered a sensitive probe to the properties of the medium created in heavy-ion collisions. The RHIC Beam Energy Scan Program (BES) is designed to investigate the QCD phase diagram and search for a potential QCD critical point. The BES-program covers a wide energy range from $\sqrt{s_{\rm{NN}}}$ = 3 to 54.4 GeV. Of particular interest is the high baryon density region which can be explored through production of strange hadrons ($K^{0}_{s}$, $ \Lambda$) at lower energies from the fixed target program. Such studies can also help understand their production mechanism in high baryon density medium.

In this poster, we will report measurements of strange particle ($K^{0}_{s}$, $ \Lambda$) production in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.2 GeV. The data were taken in 2018 by the STAR experiment with the fixed target configuration. After correcting for detector acceptance and tracking efficiency, invariant yields and rapidity density distributions of $K^{0}_{s}$ and $ \Lambda$ will be presented. The physics implications on the collision dynamics will also be discussed.

Speaker: Ashish Jalotra (University of Jammu)

poster_QM23_v6.pdf

17:30 Structure in the speed of sound: from neutron stars to heavy-ion collisions

Neutron star equations of state that can sustain heavy neutron stars over 2 Msun necessitate a large, rapid rise in the speed of sound.  The family of equations of states, which assume electric neutrality along beta equilibrium and vanishing temperatures, with large bumps in the speed of sound have been suggested to be incompatible with the equation of state extracted from heavy-ion collisions. If it is true that heavy-ions exclude large bumps in the speed of sound up to values close to the causal limit, then this in turn excludes the possibility of ultra-massive neutron stars (i.e. up to 2.5 Msun).
In our studies, we convert equations of state with a bump in the speed of sound that are compatible with massive neutron stars to nearly symmetric nuclear matter using the nuclear symmetry energy expansion with 4 coefficients. With a range of different coefficients, we are able to obtain upper and lower bounds for converted symmetric nuclear matter with causality and stability constraints. We compare our converted equation of state with heavy-ion collision data by the hadronic transport method SMASH with the mean-field potential.

Speaker: Nanxi Yao (University of Illinois, Urbana-Champaign)

qmposter.pdf

17:30 Study for the high-density matter at J-PARC Heavy-Ion Project

Heavy ion collisions at $\sqrt{s_{NN}}$ ~ several GeV seem to be the only method to generate ultra-high-density matter comparable to those inside neutron stars experimentally.
In such ultra-high-density matter, many phenomena are expected, such as the transition to the non-confined phase. Among those, a few things are well understood about high-density matter, both theoretically and experimentally, and these are currently being actively studied.

J-PARC Heavy Ion Project (J-PARC-HI) is an experimental project to generate and study ultra-high-density matter using 1-12A GeV heavy ion beams. Although the current J-PARC is a 30GeV proton accelerator, it has successfully supplied a high-intensity beam of about 60kW even in slow extraction. Therefore, the J-PARC-HI case will expect high-flux beams with excellent performance. In other words, only the injector must be newly constructed, and the acceleration afterwards will use the current acceleration scheme as much as possible. The design of the injector and the acceleration scheme is being studied in detail by the J-PARC accelerator group.

We have the staging plan of the project into two stages. In the first stage, a booster ring will reuse the KEK-PS. Even in this stage, we expect to achieve an intensity of $10^{8}$Hz. In the second stage, a new booster ring will be constructed where the highest intensity heavy ion beam of $10^{11}$Hz is expected. We consider the primary goal of the first stage as the confirmation of non-confined phases in high-density regions. The purpose of the second stage is to be precise measurements of the high-density matter. Applications such as producing various hyper-nuclei and studying the internal structure of hadrons are also conceivable. In this talk, we would like to discuss these rich physics opportunities and the concept of detector design.

Speaker: Dr Yuhei Morino (KEK)

qm2023_ymorino_v2.pdf

17:30 Study of $K_{1}$ meson production in $pp$ collisions with ALICE

$K_{1}$ and $K^{*}$ mesons are chiral partners whose vacuum widths are smaller than 100 MeV. This makes these mesons ideal to study possible effects of chiral symmetry restoration in heavy-ion collisions. In a recent theoretical study, the $K_{1}/K^{*}$ ratio in heavy-ion collisions is expected to be substantially larger than the statistical hadronisation model predictions. The study of the $K_{1}/K^{*}$ ratio as a function of multiplicity in different collision systems ranging from $pp$ to central heavy-ion collisions can provide crucial information on effects of the chiral symmetry restoration. The ALICE detector has an excellent capability of particle identification, so the $K_{1}$ meson can be measured via its hadronic decay channels such as $K_{1}^{-}\to \rho^{0}K^{-}$ and $K_{1}^{-}\to \pi^{-}\bar{K}^{*0}$. In this poster, the feasibility study of the $K_{1}$ measurement in $pp$ collisions with ALICE is presented.

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

QM2023_SJI_v3_A0.pdf

17:30 Study of baryon fragmentation in charged-particle jets in pp collisions with ALICE

Studies of gluon fragmentation at LEP have shown hints that gluon-initiated jets produce more baryons than quark-initiated jets. Our current knowledge of fragmentation functions is almost exclusively based on fits to data from $e^+ e^-$ collisions and semi-inclusive deep inelastic scattering processes, both of which are mainly sensitive to quark fragmentation, leaving gluon fragmentation functions poorly constrained. Hadronic collisions at the LHC, however, produce data rich in gluon-initiated final states and offer excellent opportunities to study gluon fragmentation directly. In this poster, we present the potential for ALICE to investigate gluon fragmentation with unprecedented precision by measuring fragmentation into baryons and mesons in pp collisions at $\sqrt{s} = 13.6$~TeV.

Speaker: Gijs Van Weelden (Nikhef National institute for subatomic physics (NL))

2023-08-30-Poster.pdf

17:30 Study of Baryon Number Transport via $\Omega$-hadron Correlations

In nuclear collisions at low RHIC energies, although $s$ and $\bar{s}$ quarks are produced in pairs, there is a significant excess of $\Omega^{-}$ over ${\bar{\Omega}}^{+}$ which suggests that $\Omega^{-}$ carries a net baryon number. Such an excess of net baryon number at mid-rapidity in Au+Au collisions manifests effective mechanisms of baryon number transport over a large rapidity gap. Gluon junction has been proposed as a possible structure allowing for baryon number transport over large rapidity gaps. We also argue that the net $\Omega^{-}$ production on the proton-going side of $p$+Au collisions may provide a sensitive probe of the gluon junction mechanism. We will present AMPT model simulations of $\Omega$-$K$, $\Omega$-$\Xi$, and $\Omega$-$\Lambda$ correlations in Au+Au collisions at $\sqrt{s_{NN}}$ = 14.6 GeV and 7.7 GeV as well as $p$+Au collisions at 62 GeV. These correlations reflect the effects of strangeness conservation and baryon number transport in nuclear collisions. In particular, the $\Omega$-hadron correlations in AMPT show distinct dependence on baryon densities indicating quantitative sensitivity to details of the baryon number transport dynamics. Results from the default and string-melting versions of the AMPT calculations are used to examine the imprints on such correlations left by the hadronization schemes of string fragmentation and quark coalescence, respectively. AMPT calculations predict very significant differences in the correlations at 7.7 GeV between these hadronization schemes, which can be used experimentally to investigate the extent of roles played by partonic degrees of freedom in Au+Au collisions at this energy. Implications on the experimental program to measure these correlations with the STAR experiment at RHIC will also be discussed.

Speaker: XIATONG WU (Department of Physics and Astronomy, University of California, Los Angeles, CA 90095, USA)

Xiatong_QM2023_3.pdf

17:30 Study of multiplicity-dependent ρ0(770) production in pp collisions with ALICE

Short-lived resonances are ideal probes to study the properties of the hadron gas phase created in heavy-ion collisions in the post-hadronization phase. Since the resonance lifetime is comparable to that of the hadron gas phase, their yields are affected by the competing rescattering and regeneration effects. These can be studied experimentally by measuring the yield ratio of resonances to the corresponding long-lived hadron as a function of the charged-particle multiplicity, which is directly connected to the lifetime of the hadron gas phase. In this context, the $\rho^{0}(770)$ resonance is particularly interesting due to its very short lifetime of about 1.3 fm/$c$. The measurement of the $\rho^{0}(770)$ production yield in low-multiplicity collisions, corresponding to a very short duration of the hadron gas phase, serves as a fundamental reference for measurements in heavy-ion collisions.

In this poster, recent ALICE measurements of the $\rho^{0}(770)$ production in pp collisions as a function of multiplicity are presented. The results are discussed together with existing measurements in other collision systems in the context of the state-of-the-art phenomenological models used to describe particle production at LHC energy.

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

23.09.05_QM2023_HJLim.pdf

17:30 Study of strangeness and baryon production through angular correlations between Xi baryons and identified hadrons in pp collisions with ALICE

Two-particle correlation functions give insight into the microscopic details of the production and transport mechanisms of conserved quantum numbers. In this contribution, new final measurements by the ALICE Collaboration of $\Xi-\pi$, $\Xi-$K, $\Xi-$p, $\Xi-\Lambda$, and $\Xi-\Xi$ correlation functions are presented to study how charge, strangeness, and baryon numbers are balanced in proton-proton collisions at $\sqrt{s}$ = 13 TeV. Furthermore, the multiplicity dependence of the charge balancing is investigated to give insight into the surprising strangeness enhancement observed in small collision systems. The results are compared with Monte Carlo predictions in order to distinguish between different string topologies implemented in PYTHIA 8 (e.g. ropes and junctions), as well as Herwig 7 (a string-based approach with cluster hadronisation), and EPOS-LHC (a core-corona-based model).

Speaker: Peter Christiansen (Lund University (SE))

qm_poster_christiansen_lund_final.pdf

17:30 Study of the three-body dynamics at short range via deuteron-hadron correlations by ALICE

We present a new experimental method to study three-body nuclear systems by measuring correlations in the momentum space of deuteron-hadron pairs produced in proton-proton collisions at the LHC. The study of three- and many-body dynamics has been a long-standing goal in nuclear physics, particularly for understanding the structure of light nuclei and describing neutron-rich and dense nuclear matter.

The ALICE Collaboration has performed measurements of the K$^+$--d and p--d correlations analyzing high-multiplicity proton-proton collisions at $\sqrt{s}$ = 13 TeV. The correlation functions are compared with effective two-body calculations anchored to results from K$^+$--d and p--d scattering experiments that provide an excellent description of the measured $\mathrm{K}^+$–d correlation but fail to describe the p--d system. This discrepancy can only be resolved by performing a full three-body calculation that accounts for the underlying three-nucleon dynamics. The analysis demonstrates that nucleons are the explicit degrees of freedom also in the correlations among light nuclei produced at short distances in hadronic collisions and opens the possibility of investigating the effect of genuine many-body nuclear interactions at the LHC in the future.

Speaker: Oton Vazquez Doce (INFN e Laboratori Nazionali di Frascati (IT))

QM23_ALICE_ThreeBodyDynamics_OtonVD.pdf

17:30 Studying magnetic fields in heavy-ion collisions using net-proton fluctuations with ALICE

Fluctuations of conserved charges, such as baryon number, electric charge, and strangeness, are a unique tool for studying the phase diagram of strongly interacting matter. The cumulants of the distributions of the conserved charges in heavy-ion collisions can be related to the equation of state in lattice QCD (LQCD), making first-principles calculations accessible in the experiment. Recent results from LQCD suggest that the thermodynamic susceptibilities, which are related to the experimentally measurable cumulants of the conserved charges, are significantly affected by strong magnetic fields.

In this talk, measurements of the second-order cumulants of the (anti-)proton and net-proton numbers in Pb--Pb collisions with the ALICE detector at the LHC are presented. The moments of the net-proton number, used as a proxy for the baryon number, are calculated using the Identity Method to avoid the problem of misidentification. The new results cover a large momentum acceptance and the centrality range. The ratios of the cumulants in peripheral to central events give insight into the magnetic fields produced in the heavy-ion collisions.

Speaker: Ilya Fokin (Heidelberg University (DE))

QM2023_net_proton_fluct.pdf

17:30 Studying the nucleus via angular correlations in UPCs with ALICE

Angular correlations and polarization studies provide valuable insights into the vector meson production mechanism, including interference effects as well as information on the nuclear geometry of the target. In this talk, we present two new results. We will report the first measurement of the polarization of both coherent and incoherent J/psi photoproduction in ultra-peripheral Pb--Pb collisions at $\sqrt{s_{NN}}=5.02$~TeV. In addition, we will present the first measurement of azimuthal anisotropies of coherent $\rho^{0}$ photoproduction in ultra-peripheral Pb--Pb collisions. These are the first measurements of this kind at the LHC.

Speaker: Andrea Giovanni Riffero (University and INFN Torino (IT))

Poster_QM2023_Riffero.pdf

17:30 SUBA-Jet: a new coherent jet energy loss model for heavy-ion collisions

We present a new model for jet quenching via coherent gluon radiation and elastic scatterings off medium partons. The jet energy loss is simulated as a perturbative final-state vacuum parton shower followed by a medium-induced shower originating from elastic and radiative collisions with the medium constituents. Coherency is achieved by starting with trial gluons that act as field dressing of the initial jet parton. These are formed according to a Gunion-Bertsch seed. The QCD version of the LPM effect is attained by increasing the phase of the trial gluons through elastic scatterings with the medium. Above a phase threshold, the trial gluons will be formed and can produce coherent radiation themselves.

The model has been implemented in a Monte Carlo code and has been validated by successfully reproducing the BDMPS-Z prediction for the energy spectrum of radiated gluons in a static medium. The realistic case with minimal assumptions is also produced and shown. In particular, we show the influence of various parameters on the energy spectrum and transverse momentum distribution, such as the in-medium quark masses, the energy transfer in the recoil process, and the phase accumulation criteria, especially for low and intermediate energy gluons.

The model is constructed with realistic medium description and jet-medium coupling in mind. As such, we also show the first results when the parton shower is coupled to realistic expanding medium modelled usign vHLLE code. Finally, we use Pythia for jet hadronization and draw a basic comparison to RHIC and LHC data.

Reference: to be submitted soon to arXiv/journal

Speaker: Dr Iurii Karpenko (FNSPE CTU in Prague)

QM2023-poster-karpenko.pdf

17:30 Suppression and flavor correlation modification of leading di-hadron at RHIC and the LHC

The study of the suppression of the leading two hadrons within jets, by virtue of being robust against the underlying event background, provides an insight into the onset of quenching in the history of the evolution of relativistic heavy-ion collisions, which can help discriminate between different partonic energy loss mechanisms. The modification of their flavor correlations, on the other hand, probes hadronization in the last stage of jet evolution. Using a variety of Monte Carlo simulations, in this talk, we will present first phenomenological studies of di-hadron observables and their dependence on quark and gluon jet origins, thereby motivating future leading di-hadron measurements at RHIC and the LHC.

Speaker: Dr Yang-Ting Chien (Georgia State University)

17:30 Systematic study of energy loss in the QGP for various collision systems at PHENIX

In studies of QGP, it has been observed that at high-energy heavy-ion (A$+$A) collisions, high-momentum particles with light and heavy flavors receive significant suppression. This indicates that particles lose their energies in QGP. One of the most important topics is to quantify the energy loss and to investigate the energy loss mechanism.
PHENIX measured the fractional momentum loss, $S_{loss}$, by comparing the inclusive spectra in A$+$A and $p+p$ collisions. To study the path length dependence in more detail, we extend the $S_{loss}$ measurement by comparing the in-plane and out-of-plane spectra using the azimuthal anisotropy v_2. Using the PHENIX data, we extract the updated Sloss in Au+Au, Cu+Au, and Cu+Cu collisions and systematically compare them.
In this poster, we will present the systematic comparison of the updated Sloss from various collision systems and discuss the energy loss mechanism.

Speaker: Takashi Hachiya (Nara Women's University (JP))

QMposter_hachiya‗v2.pdf

17:30 Systematics of Hidden and Open Strangeness Production in Few GeV Heavy Ion Collisions

Investigating strangeness production and propagation in heavy-ion collisions in the few GeV energy regime is a sensitive tool for studying the microscopic structure of nuclear matter at high baryo-chemical potential.
In this contribution, we present preliminary results on the production of strange hadrons from a total of $3\times10^9$ most active Ag(1.58$A$ GeV)+Ag events recorded with HADES in 2019 and compare their spectra and extracted multiplicities with results obtained from statistical hadronization models with different parameterizations. Special attention is paid to the comparison between different canonical descriptions in the context of strangeness suppression.

With respect to this, the $\phi(1020)$/$\Xi^-$- and $\phi(1020)$/$K^-$-ratios are utilized to test the consistency of the corresponding models in describing their relative yields. The significant softening of the $K^-$ transverse spectra due to the $\phi(1020)$ feed-down is also discussed.

Furthermore, we discuss the centrality ($A_{part}$) dependence of strange-hadron multiplicities, which were found to follow a universal scaling for the collision system Au(1.23$A$ GeV)+Au.

Speaker: Marvin Kohls

MarvinKohls_HADES_Strangeness_QM2023.pdf

17:30 Target jet substructure and correlation

We discuss the reconstruction of target jet and the framework of quantifying its internal substructure. Due to momentum and charge conservation, target and current correlation can be exploited which significantly constrains the event-wide particle distributions. We demonstrate this method using Pythia simulations of electron-proton collisions in the context of determining the flavor and substructure of the struck quark jet. Extensions to electron-ion collisions and target tagging using BeAGLE simulations will be discussed. This study will provide novel physics cases for forward detector designs and promote the synergy with nuclear physics.

Speaker: Dr Yang-Ting Chien (Georgia State University)

QM_target_jet_poster.pdf

17:30 Testing inputs to hydro codes with factorization breaking

Data obtained at RHIC can be reproduced with relativistic viscous hydrodynamic simulations by adjusting the viscosity and initial conditions but it is difficult to disentangle these quantities. It is therefore important to find orthogonal observables to constrain the initial conditions separately from the viscosity. New observables have been measured at the LHC and shown to be sensitive to initial conditions and less to medium properties, specifically factorization breaking ratios appears to be promising. Here we consider two initial condition models, NeXus and TRENTO. While both models yield similar results for the scaled flow harmonic distributions both at the LHC and RHIC, they lead to quantitatively much more different patterns for the factorization breaking ratios at RHIC than at LHC, due to the shorter lifetime. For the same reason, not only final state interactions but also initial free streaming matter in these predictions and differences between these are enhanced at RHIC compared to LHC. Therefore experimental factorization breaking ratios at RHIC top energy would be interesting to get.

This presentation is a follow up of arXiv:2105.12792

Speaker: Frederique Grassi

17:30 Testing new proxies of B,Q and S cumulants in Au-Au collisions at BES energies with EPOS 4

In the exploration of the nuclear matter phase diagram, the susceptibilities of conserved charges are useful theoretical tools to probe the existence of a $1^\text{st}$ order phase transition, and a possible critical endpoint. They can be related to the cumulants of the considered net-charges, for which STAR collaboration recently published experimental measurements of proxies, in Au-Au collisions at several energies of the Beam Energy Scan. Hence, the measured (co)variances of $\pi^\pm$, $p/\overline{p}$ and $K^\pm$ are used to build proxy ratios for the corresponding $2^\text{nd}$ order cumulant ratios of electric charge Q, baryonic number B and strangeness S.

It is nevertheless important to disentangle the different effects contributing to these net-multiplicity cumulants of hadronic species, in addition to the fluctuations which they are supposed to probe. For this reason, we studied the impact of hadronic cascades on these observables, thanks to complete simulations of Au-Au collisions performed with EPOS 4. The results are compared with cumulant ratios of exact conserved charges, and proposed enhanced proxy ratios based on a study of the hadronic breakdown contributions to the total susceptibilities with lQCD and HRG model calculations.

We show that the use of $\Lambda$ baryons variance, additionally to $\sigma^2_\pi$, $\sigma^2_p$ and $\sigma^2_K$ used by STAR, allow to build proxies that reconstruct quantitatively better the ratios of $B,Q$ and $S$ correlations. Moreover, even if hadronic cascades modify the signal amplitude for all (co)variances, they have little impact on most of their ratios.

Speaker: Dr Johannès Jahan (University of Houston - Department of Physics)

JJAHAN-Poster_QM23.pdf

17:30 The direct photon puzzle and the weak magnetic photon emission

In heavy ion collisions, the measured spectrum of direct photons at RHIC and the LHC has been found as azimuthally anisotropic as pions. In particular, a large elliptic flow of the direct photos has been observed, which strongly contradicts conventional theoretical predictions, leading to the well-known “direct photon puzzle”.

In this talk, instead of a strong magnetic field assumption which has been considered previously, we propose the effect of weak magnetic photon emission, originated from the interplay of a weak external magnetic field and the longitudinal dynamical evolution of the quark-gluon plasma. The weak magnetic photon emission results in an extra source of photon production from the quark-gluon plasma, with a large elliptic flow. In cases of Bjorken flow and more realistic 3+1D hydrodynamical evolution simulated via MUSIC, the effects of weak magnetic photon emission are justified. Given this novel effect, under realistic conditions with respect to heavy-ion collisions carried out at RHIC and the LHC, especially that a weak magnetic field satisfying $|eB|\ll m_\pi^2$, the experimentally measured direct photon elliptic flow can be well reproduced.

Accordingly, we found that the direct photon elliptic flow can be used as a magnetometer for the expanding QGP. For the top energy of RHIC collisions, through event-by-event hydrodynamic simulations with respect to Trento 3D initial conditions, the averaged magnetic field strength can be extracted to be a few percent of the pion mass square. Moreover, a significant increase in $v_3$ of direct photons is observed as well from the weak magnetic photon emission.

arxiv:2302.07696

Speakers: Jing-an Sun (Fudan University), Li Yan (Fudan University)

PosterQM2023.pdf

17:30 The effects of hydrodynamic causality conditions on Bayesian analysis

Despite the success of hydrodynamic models in describing heavy-ion collisions, there have long been questions about its regime of validity. Recently-derived conditions on the causality of the hydrodynamic equations [1] can give a concrete answer --- if evolution is acausal, it is not a faithful representation of the underlying QCD theory. It is now known that current simulation models reach acausal regimes, at least sometimes.

We study the phenomenological effects of this knowledge in the context of a comprehensive, multi-system model-to-data comparison that was originally performed by the JETSCAPE Collaboration [2]. Different ways are explored to include information about causality violation (and therefore the validity of the model) into the analysis, and its effects on the extracted physical properties. Specifically, when performing Bayesian inference we can include the information in the prior probability (quantifying our trust in the model based on the degree or frequency of causality violation), or in the model uncertainty (estimating an increased uncertainty when there is violation of causality). The resulting changes in the posterior give an indication of the uncertainty that is contributed by model (in)validity, and the importance of addressing these fundamental issues in our treatment of heavy-ion collisions.

As an additional study, we identify various causes of acausality in hydrodynamic simulations, and therefore the best targets for designing more realistic models.

References:
[1] Bemfica, Disconzi, Hoang, Noronha, Radosz, Phys.Rev.Lett. 126 (2021) 22, 222301
[2] JETSCAPE Collaboration, Phys.Rev.C 103 (2021) 5, 054904; Phys.Rev.Lett. 126 (2021) 24, 242301

Speaker: Thiago Siqueira Domingues (University of São Paulo)

QM2023_Poster_final.pdf

17:30 The effects of magnetic field and chemical potential on holographic jet quenching in heavy ion collisions

We employ the AdS/CFT correspondence to study the jet quenching effect in Quark-gluon plasma in heavy-ion collisions.The nuclear modification factor $R_{AA}$ and elliptic flow parameter $v_{2}$ are studied in different-centrality collisions at RHIC and LHC.Our numerical results agree with data.Magnetic field and chemical potential of the medium are also considered for the observable evaluations.It is found that magnetic field and chemical potential both enhance the jet energy loss.

Speaker: Mr Liqiang Zhu (Central China Normal University)

17:30 The elliptic flow of ${\pi}^{\pm}$, ${K}^{\pm}$, $p$ , and $\bar{p}$ in Au + Au collisions at $\sqrt{s_{NN}}$ = 7.7 and 9.2 GeV from STAR

The elliptic flow ($v_{2}$) is the second Fourier coefficient of azimuthal distributions of produced particles in heavy-ion collisions. Measurements of identified particle $v_{2}$ is one of the most informative ways in studying the properties of hot and dense nuclear matter created in heavy-ion collisions.

In this poster, elliptic flow of identified hadrons (${\pi}^{\pm}$, ${K}^{\pm}$, $p$ , and $\bar{p}$) in $\sqrt{s_{NN}}$ = 7.7 and 9.2 GeV Au+Au collisions, data collected by the STAR experiment in the second phase of the beam energy scan (BES-II), will be presented. We will show $v_{2}$ as a function of $p_{T}$ for these particles in 0-80$\%$, 0-10$\%$, 10-40$\%$, and 40-80$\%$ centrality bins and compare to those from other collision energies. In addition, the number of constituent quark (NCQ) scaling in $v_{2}$ will be studied, and the $v_{2}$ results will be compared to different model calculations.

Speaker: Xing Wu

QM2023_poster_xing_ver6.pdf

17:30 The elliptic flow of (multi-)strange hadrons in Au + Au collisions at $\sqrt{s_{NN}}$ = 7.7 and 9.2 GeV from STAR

The elliptic flow ($v_{2}$) is the second harmonic coefficient in a Fourier expansion of the azimuthal distribution of produced particles with respect to the reaction plane. Strange hadrons, especially the multi-strange hadrons, are regarded as good probes for the early stages of the collision, as they freeze-out earlier and have smaller hadronic cross sections than light hadrons. Thus, a comparative study of various strange and multi-strange hadrons can help us study the medium properties and better explore the QCD phase structure.

In this poster, with datasets of the second phase of the RHIC Beam Energy Scan (BES-II), we will present the measurements of $v_{2}$ for $K^{0}_{S}$, $\Lambda$, $\bar{\Lambda}$, $\Xi^-$, $\bar{\Xi}^+$, $\Omega^-$, $\bar{\Omega}^+$, and $\phi$ mesons in Au + Au collisions at $\sqrt{s_{NN}}$ = 7.7 and 9.2 GeV using the STAR detector. The $v_{2}$ results will be shown as a function of transverse momentum and collision centrality. The number of constituent quarks (NCQ) scaling will be tested from central to peripheral collisions. The inferred information related to the QCD phase structure will be discussed.

Speaker: Guoping Wang

gp_QM2023_poster6.pdf

17:30 The evolution of jets and high-pT probes in small collisions systems using a multistage framework

Understanding the modification of jets and high-p_T probes in small systems requires the integration of soft and hard physics. We present recent developments in extending the JETSCAPE framework to build an event generator, which includes correlations between soft and hard partons, to study jet observables in small systems. The multi-scale physics of the collision is separated into different stages. Hard scatterings are first sampled at binary collision positions provided by the Glauber geometry. They are then propagated backward in space-time following an initial-state shower to obtain the initiating partons' energies and momenta before the collision. These energies and momenta are then subtracted from the incoming colliding nucleons for soft-particle production, modeled by the 3D-Glauber + hydrodynamics + hadronic transport framework. This new hybrid approach includes non-trivial correlations between jet and soft particle productions in small systems. We calibrate this framework with the measured event activity distributions in p+p and p+Pb collisions at 5.02 TeV. We further compare our results for final state hadron's p_T-spectra from low to high p_T in p+p and p+Pb collisions with experimental results in p+Pb at the LHC. Lastly, we present results of additional observables such as the distributions of jet recoiling from a high-p_T hadron and the nuclear modification factor R_{pPb} as a function of event activity.

Speaker: Abhijit Majumder (Wayne State University)

Majumder_Poster.pdf

17:30 The freezeout procedure with the method of moments

The method of moments has been employed to derive relativistic fluid-dynamical theories from the Boltzmann equation for the past decades [1]. This approach consists in expanding the single-particle distribution function using a basis of irreducible momenta, where the expansion coefficients are the irreducible moments of the nonequilibrium distribution function [2]. Unlike the Chapman-Enskog method [3], it has the advantage of yielding formulations that might be causal and stable, provided the transport coefficients satisfy certain constraints [4]. However, so far, only the equations of motion for the hydrodynamic moments have been explicitly calculated, with the equations of motion for the moments of rank 3 and 4 being calculated recently, in Ref. [5]. In this contribution, we address this problem by systematically calculating the general equations of motion for all irreducible moments and show how they can be used to solve the Boltzmann equation itself. Since this method of solving the Boltzmann equation does not rely on resolving particle degrees of freedom, it can be used to provide a more consistent description of the freezeout process that does not require a particlization procedure. We investigate this prescription in a Bjorken flow scenario and investigate with detail the transition from a fluid description to a transport one.

References

[1] W. Israel and J. Stewart, Phys. Lett. A 58, 213 (1976).

[2] G. S. Denicol, H. Niemi, E. Moln ́ar, and D. H. Rischke, Phys. Rev. D 85, 114047 (2012).

[3] S. Chapman and T. G. Cowling, The mathematical theory of non-uniform gases (Cambridge University Press, Cambridge, 1970).

[4] W. A. Hiscock and L. Lindblom, Ann. Phys. 151, 466 (1983); T. S. Olson, Ann. Phys. 199, 18 (1990); G. S. Denicol, T. Kodama, T. Koide, and P. Mota, J Phys. G 35, 115102 (2008); S. Pu, T. Koide, and D. H. Rischke, Phys. Rev. D 81, 114039 (2010); C. V. Brito and G. S. Denicol, Phys. Rev. D 102, 116009 (2020); J. Sammet, M. Mayer, and D. H. Rischke, arXiv:2302.01070 [hep-th].

[5] C. V. P. de Brito and G. S. Denicol, arXiv:2302.09097 [nucl-th].

Speaker: Caio Brito (Universidade Federal Fluminense)

brito-poster-qm2023.pdf

17:30 The McDIPPER: A novel saturation-based 3+1D initial state model for Heavy Ion Collisions

We present a new 3+1D resolved model for the initial state of ultrarelativistic Heavy-Ion collisions, based on the $k_\perp$ factorized Color Glass Condensate hybrid approach [1-4]. This new model responds to the need for a rapidity-resolved initial-state Monte Carlo event generator which can deposit the relevant conserved charges (energy, charge and baryon densities) both in the midrapidity and forward/backward regions of the collision.
Based on the IP-Sat model this event-by-event generator computes the phase-space distributions, from where the relevant conserved charges can be computed as moments. In the present work we have included the leading order contributions to the light flavor parton densities. We present relevant observables, such as the eccentricities and flow decorrelation, as tests of this new approach.

References:
[1] O. Garcia-Montero, H. Elfner and S. Schlichting. In preparation.
[2]T. Lappi and S. Schlichting, Phys. Rev. D 97, 034034 (2018), arXiv:1708.08625 [hep-ph].
[3] T. Lappi and H. Mäntysaari, Phys. Rev. D 88, 114020 (2013), arXiv:1309.6963 [hep-ph]
[4] H. Mäntysaari, Scattering off the Color Glass Condensate, Ph.D. thesis, Jyvaskyla U. (2015), arXiv:1506.07313 [hep-ph].

Speaker: Oscar Garcia-Montero

QM_POSTER_OGM.pdf

17:30 The most vortical baryonic matter

The study of strongly interacting matter under external conditions (such as high temperatures and/or baryon densities) provides unique insights into its fundamental theory, Quantum Chromodynamics (QCD). A nonzero angular momentum imposed on a QCD system can bring rich and intriguing phenomena, with the proton spin structure being a perfect example. A much larger QCD system with substantial angular momentum, produced by non-central heavy ion collisions, has attracted a lot of interest recently. This angular momentum induces nontrivial vortical fluid patterns in the fireball formed by the collision and eventually leads to spin polarization of final state hadrons, as shown by experimental measurements from the STAR, ALICE and HADES Collaborations. A clear understanding of the angular momentum initial conditions for the fireball, such as the total amount and its rapidity distribution, is, however, still lacking. In this talk, we demonstrate how baryon stopping plays a key role for the deposition of angular momentum toward the mid-rapidity region. By calculating rapidity loss after multiple binary collisions for wounded nucleons, we quantify the angular momentum initial conditions for heavy ion collisions from GeV to TeV beam energies. This also allows us to explain the beam energy dependence of experimental data for spin polarization as well as to reveal a nontrivial correlation between net baryon number and initial angular momentum in the fireball. Finally we introduce the ratio of angular momentum to net baryon number as a measure for comparing “spinning-ness” and show that the most spinning baryonic matter, created in heavy ion collisions at energies of a few GeV, is about an order of magnitude higher than a proton in terms of this measure.

Speaker: Zachary Akridge (Indiana University)

17:30 The shear viscosity of parton matter under two-body scatterings

The shear viscosity (eta) of a quark-gluon plasma in equilibrium can be calculated numerically using the Green-Kubo relation or analytically using several methods, including the Israel-Stewart, Navier-Stokes, relaxation time approximation, and Chapman-Enskog methods. In this work [1], we first examine these analytical methods for isotropic as well as anisotropic two-body scatterings. We confirm that the Chapman-Enskog method is the most accurate while correcting the typos in an earlier work on this subject.

We then apply the Chapman-Enskog method to study the shear viscosity of the parton matter in the center cell of central and midcentral Au+Au collisions at 200AGeV and Pb+Pb collisions at 2.76ATeV from a multi-phase transport (AMPT) model. At the parton scattering cross section of 3 mb that enables the transport model to reproduce bulk observables including the elliptic flow, the average eta/s of the parton matter is found to be very small, between one to three times 1/(4pi). In addition, as a result of using a constant Debye mass or cross section for parton scatterings, the eta/s ratio from the AMPT model increases with time (as the effective temperature decreases), contrary to the pQCD results that use temperature-dependent Debye masses. This can be a direction for future model improvements.

[1] N. MacKay and Z.W. Lin. Eur. Phys. J. C 82, 918 (2022).

Speaker: Zi-Wei Lin (East Carolina University)

poster-eta-ZWLin.pdf

17:30 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 up to 700 charged particles per event produced in up to 10 MHz heavy-ion collision 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 is progressing on several fronts. Firstly, the mechanical design is being finalized and tested, while the cooling concept is being assessed through a thermal demonstrator. In addition, modules assembled during pre-series are undergoing characterization, and the final production phase has begun, with multiple quality control steps in place to ensure reliable module performance and high production yield. The implementation of these quality control steps has involved the development of necessary hardware and software. This work will provide an overview of the systematic testing of the STS modules and components towards series production, as well as highlighting the most significant achievements and challenges in detector mechanical assembly and integration.

Speaker: Adrian Rodriguez

17:30 The Silicon Vertex Tracker (SVT): a MAPS based tracker for the ePIC Detector at the Electron-Ion Collider

Experiments at the future Electron-Ion collider pose stringent requirements on the tracking system for the measurement of the scattered electron and charged particles produced in the collision, as well as the position of the collision point and any decay vertices of hadrons containing heavy quarks. Monolithic Active Pixel Sensors (MAPS) offer the possibility of high granularity in combination with low power consumption and low mass, making them ideally suited for these subsystems at the EIC. R&D is currently ongoing to ensure a well-integrated, large-acceptance, precision tracking and vertexing solution based on a new generation of MAPS in 65 nm CMOS imaging technology. This poster will cover the current design and some of the R&D efforts currently in progress for the Silicon Vertex Tracker (SVT) of the ePIC Detector using the new 65 nm MAPS technology.

Speaker: Nicole Apadula (Lawrence Berkeley National Lab. (US))

17:30 The sPHENIX fixed latency reconstruction system

The sPHENIX detector is the next generation experiment at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. Starting commissioning in May, it will collect high statistics data sets from ultra relativistic Au+Au, p+p and p+Au collisions in the next 3 years. The readout is a combination of triggered readout for calorimeters and streaming readout for the silicon pixel/strip detectors and the time projection chamber (TPC). sPHENIX does not employ high level triggers which would require building events in real-time except for a small subset that is assembled online for monitoring purposes. Events are assembled offline from multiple input streams only during the multi pass offline reconstruction which includes calibration and space charge distortion corrections for the TPC data. This reconstruction will run near real-time within a fixed latency of when the data was taken. To meet its physics requirements sPHENIX has developed state of the art reconstruction software based on the "A Common Tracking Software" (ACTS) package which was adapted to reconstruct the TPC data. The raw data will be processed at the Tier 0 for the RHIC experiments - the Scientific Data Computing Center (SDCC) at BNL. The Production and Distributed Analysis (PanDA) system was chosen as workload management system to handle the complexities of our workflow.

This poster will show the details of the data processing for the sPHENIX experiment.

Speaker: Christopher Pinkenburg (BNL)

17:30 The study of $v_{2}$ with a new double-differential event categorization using multiplicity and spectator neutrons in PHENIX

When studying the properties of the Quark-Gluon Plasma (QGP) formed in relativistic heavy ion collisions, it is necessary to classify the events based on the size and shape of the QGP. Typically, events are categorized by mapping the impact parameter, which cannot be measured directly, to a bulk observable that varies monotonically with it, such as soft particle production. In the mapping, fluctuations in the initial state nuclei and the nucleon-nucleon interactions are taken into account. Even a tight experimental centrality based solely on multiplicity includes events with quite different shapes due to these fluctuations. To select much more homogeneous sub-samples of events, adding a second, independent qualifier is helpful. A decade ago, event-shape engineering proposed the flow vector as a second qualifier, but it is influenced by final state interactions. Instead, we use spectator neutrons measured in the zero-degree calorimeter of PHENIX as the second dimension. This new approach provides a more precise way to categorize QGP events, which has important implications for understanding the underlying physics of heavy ion collisions. By using this novel 2D event characterization in Au$+$Au collisions at RHIC, we will demonstrate elliptic flow results with tighter constraints on the initial geometry. We will also discuss how this may be relevant in studying path-length dependent energy loss and possible multiple parton interactions (MPI).

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

QM2023poster_maya_v2with2Dcentrality_v3.pdf

17:30 The Tsallis-Thermometer as a QGP Indicator For Large And Small Collisional Systems

Recent experimental results present collectivity also in small systems with high-multiplicity. Today these phenomena are not completely understood: it is an important question whether the presence of the QGP is necessary for the observed collectivity or not. Moreover, the connection between the experimental observables and theories is not trivial. In our phenomenological study we introduce the ‘Tsallis-thermometer’ as an indicator of quark-gluon plasma, that aims to describe the smooth transition from small to large collisional systems.

The transverse momentum distribution of identified hadrons are analyzed within the thermodynamically consistent formulation of non-extensive statistics. A wide range of center-of-mass energies and average event multiplicities are studied for various hadron species. We demonstrate that the average event multiplicity is a key variable in the study of high-energy collisions. For this purpose the non-extensive statistical approach is more than appropriate.

References

[1] G. Bíró, G.G. Barnaföldi, T.S. Biró, J. Phys. G, 47.10 (2020), 105002.
[2] G. Bíró, G.G. Barnaföldi, K. Ürmössy, T.S. Biró, Á. Takács, Entropy, 19(3), (2017), 88
[3] G. Bíró, G.G. Barnaföldi, T.S. Biró, K. Shen, EPJ Web Conf., 171, (2018), 14008
[4] G. Bíró, G.G. Barnaföldi, G. Papp, T.S. Biró, Universe 5 (2019) no.6, 134

Speaker: Gergely Barnafoldi (Wigner RCP)

BarnafoldiGG_qM23_v2.pdf

17:30 The universality of energy-momentum response from kinetic theories & applicability of hydrodynamics

Universality is omnipresent when certain classes of microscopic theories are coarse-grained into effective macroscopic descriptions. Hydrodynamic theories are such macroscopic descriptions in long-wavelength, low-frequency limits of many quantum field theories. On the phenomenological side, hydrodynamics not only serves as a successful macroscopic description of the Quark-gluon plasma (QGP) in relativistic heavy-ion collisions (HICs) but also serves as the energy deposition bin of hard probes such as jets and heavy quarks. It is important to understand to what extent the propagation of the deposited energy can be described within hydrodynamics. We investigate the universality and validity of hydrodynamic theory by studying the propagation of energy-momentum perturbations in kinetic theories from microscopic to macroscopic scales. By comparing results for different microscopic theories, we find a remarkable degree of universality, where the evolution of energy-momentum perturbations of the QGP is rather well described by a pair of sound and nonhydrodynamic modes. We also discuss the future perspectives in hydrodynamic theories that one may explore based on these findings.

Speaker: Stephan Ochsenfeld (Bielefeld University)

UniversalityPoster.pdf

17:30 Thermal dielectron measurement in Au+Au collisions at $\sqrt{s_{\text{NN}}}$ $=7.7$ GeV with the STAR experiment

Due to the minimal interactions with the hot and dense QCD matter created in relativistic heavy-ion collisions, thermal dileptons emitted throughout the medium evolution are suggested as an excellent probe to study the medium properties. In the dilepton invariant mass range from 400 to 800 MeV/$c^{2}$, the mass distribution is proportional to the in-medium $\rho$ propagator, which is sensitive to medium's properties including total baryon density and temperature. The systematic measurement of in-medium $\rho$ propagators at different collision environments can be used to study the vector meson interactions with the hot and dense QCD medium.

During the Beam Energy Scan Phase-II (BES-II) program, the STAR experiment recorded large datasets at low center-of-mass energies ($\sqrt{s_{\rm NN}}$) from 3 to 19.6 GeV with detector upgrades. In this poster, we will report the first measurement of the thermal dielectron invariant mass distribution at $\sqrt{s_{\rm NN}}$ = 7.7 GeV. Machine learning techniques are used for suppressing background and increasing signal significance, which is critical for such measurements at low energies.

Speaker: Chenliang Jin

QM2023_poster_7p7GeV_ML_Chenliang_version4.pdf

17:30 Topological separation of dielectron signals using machine learning in Pb--Pb collisions with ALICE

Dielectrons are an exceptional tool to study the evolution of the medium created in heavy-ion collisions. In central collisions, the energy densities are sufficient to create a quark-gluon plasma (QGP). Thermal e$^{+}$e$^{-}$ pairs with invariant masses around 1.5 GeV/$c^{2}$ can be used to estimate the early average temperature of the QGP.

At LHC energies, the cross section of heavy-flavour (HF) production is large and correlated HF hadron decays dominate the dielectron yield for invariant masses above 1.1 GeV/$c^2$. Their contribution is modified in the medium compared to elementary collisions to an unknown extent, leading to large uncertainties in the subtraction of known hadronic sources. Alternatively, a topological separation based on the larger decay length of HF hadrons of the order of $c\tau \approx 100-500\;\mu$m, can be utilised to disentangle them from the contribution of thermal dielectrons originating from the primary vertex. To classify these pairs, machine learning (ML) algorithms can be applied to capture the complex multidimensional correlations in the tracking parameters.

In this poster, ML techniques to classify dielectron sources based on their decay topology with the ALICE detector will be presented for simulated Pb--Pb collisions at $\sqrt{s_{\text{NN}}}=5.02$ TeV. Their performance will be compared to the established analysis on the distance-of-closes approach (DCA) to the primary vertex. Finally, the way these ML techniques could be incorporated in future dielectron analysis will be discussed.

Speaker: Jerome Jung (Goethe University Frankfurt (DE))

POSTER_QM23_v7-paper.pdf

17:30 Topology and entanglement in the baryon structure at small x.

The question of identifying the baryon topological structure encoded in the baryon junctions has a long history and was recently addressed in the measurements of baryon stopping by the STAR collaboration. We suggest considering this question in a simple, exactly solvable model that allows us to clearly separate the topological junction structure from the valence quarks. We find that baryon number distribution peaks at small $x$ indicating the major role of topology. Furthermore, our model allows us to study the entanglement between valence quarks enabled by the junction and reveal the connection between topology and entanglement in the baryon structure.

Speaker: David Frenklakh (Stony Brook University)

QM4.pdf

17:30 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 focused on jets, their substructure, and open and closed heavy flavor production. To measure these observables, the sPHENIX tracking system is composed of a silicon vertex and strip detector, continuous-readout time projection chamber, and micromegas-based modules for calibration. Precise and efficient track reconstruction is required to achieve the sPHENIX science goals. The high luminosity provided by RHIC, large occupancies of heavy ion events, and streaming readout mode of the tracking system produce a challenging environment in which track reconstruction must take place. In this poster, we provide a general overview of the track reconstruction at sPHENIX and discuss its status utilizing the A Common Tracking Software package with the first data taking period of the sPHENIX experiment. Future track reconstruction plans as sPHENIX enters its primary data taking phase will also be discussed.

Speaker: Joe Osborn (Brookhaven National Laboratory)

TrackFittingPoster.pdf

17:30 Track Seeding in the sPHENIX Experiment

The tracking reconstruction procedure for the sPHENIX experiment combines data from its silicon pixel detector, silicon strip detector, time projection chamber, and micromegas-based outer tracker modules to produce tracks that trace a given particle's path through 57 total sensor layers. After clustering of the raw data is completed, the track seeding modules identify chains of clusters that correspond to valid tracks, lengthen these cluster chains by including additional clusters on the same path, and perform a preliminary fit that serves as an initial estimate for later modules. Two separate seeding modules are employed: a cellular-automaton seeding algorithm based on the ALICE time projection chamber seeding algorithm is used for the time projection chamber, while a seeding algorithm provided by the A Common Tracking Software package forms the basis of the silicon detector seeding module. In this poster, we describe the structure and performance status for the modules used in sPHENIX track seeding, based on data from the 2023 Au+Au data taking period.

Speaker: Michael Joseph Peters (Massachusetts Inst. of Technology (US))

peters_qm2023.pdf

17:30 Tracking the dynamics of system geometry using an hybrid-hydrodynamic simulation

In 2018, RHIC conducted isobar collisions of $^{96}_{44}$Ru and $^{96}_{40}$Zr nuclei in search for the chiral magnetic effect. As a byproduct, anisotropic flow data were taken, revealing differences between the two systems associated to the nuclear structure of the colliding nuclei. This observation offers an opportunity to bridge low-energy nuclear physics and high-energy collisions. Many recent works have concentrated on using the initial geometry to predict final flow data and see if nuclear shape differences would be visible. In this work, we build upon the results in [1] and actually run hydrodynamics and study how each phase (free streaming, Landau matching, expansion, hadronic transport) are related to the initial nuclear shapes seen in data. The simulations were performed using the public available X-SCAPE framework, which allows for the integration of different stages of the collision dynamics. We consider five different nuclear configurations, where we continuously change the nuclear shape from the $^{96}_{44}$Ru to $^{96}_{40}$Zr. We also include an additional case to study triaxility effects.

[1] W. M. Serenone, F. G. Gardim, A. V. Giannini, F. Grassi and K. P. Pala, "Nuclear geometry and pre-equilibrium phase effects on high-energy isobar collisions," [arXiv:2305.03703 [nucl-th]].

Speaker: Kevin Pala

tracking-the-dynamics-of-system-geometry-using-a-hybrid-hydrodynamic-simulation.pdf

17:30 Transport coefficients of heavy quarkonia comparing with heavy quark coefficients

We discuss the transport coefficients of heavy quarkonia moving in high temperature QCD plasmas. The thermal width and mass shift for quarkonia are closely related to the momentum diffusion coefficient and its dispersive counterpart for heavy quarks, respectively. For quarkonium at rest in plasmas, the longitudinal gluon part of the color-singlet self-energy diagram is sufficient to determine the leading-log thermal width, whereas the momentum dependence is obtained from the transverse gluon channel. Using the quarkonium-gluon effective vertex derived from the Bethe-Salpeter amplitude with the dipole interaction, we discuss the damping rate and mass shifts of slowly moving quarkonia and compare with the corresponding coefficients of heavy quarks.
[Phys.Lett.B 833 (2022) 137351]

Speaker: Juhee Hong (Yonsei University)

17:30 Two-particle azimuthal correlations in events with large rapidity gaps in pPb collisions recorded by CMS at 8.16 TeV

We present a new study of two-particle correlations as extracted with the CMS experiment in 8.16 TeV proton-lead (pPb) events with large rapidity gaps in the proton going region. Recent comparisons of the cross sections of such events measured in CMS as a function of the rapidity gaps (i.e., regions devoid of any particle activity) with several generators suggest that such events have contributions from electromagnetic, diffractive, and nondiffractive processes. Such interactions provide unique initial conditions with multiplicity lower than in proton-proton and pPb systems but comparable with $\gamma$-proton, electron-electron, and electron-proton systems. Two-particle and single-particle Fourier coefficients $V_{n\Delta}$ (n$=$2,3) and $v_{2} = \sqrt{V_{n\Delta}}$, respectively, of the azimuthal distributions of charged particles are presented. The Fourier coefficients are presented in ranges of event multiplicity and particle transverse momentum, and are compared to Monte-Carlo simulations.

Speaker: Moises David Leon Coello (Universidad de Sonora (MX))

17:30 Understanding effect of event-by-event fluctuations on light-nuclei yield ratio

We investigate how the event-by-event fluctuations of the final-state distribution function of nucleons physically affect the yield ratio of light nuclei based on the coalescence model.

The yield ratio of light nuclei, $N_tN_p/N_d^2$ (with $N_t$, $N_p$, and $N_d$ being triton, proton, and deuteron numbers, respectively) [1,2], is one of the observables suggested for a possible signal of the critical point of quantum chromodynamics (QCD). Based on the analyses with idealized setups, the yield ratio is known to be sensitive to the two-point neutron correlation and thus to the critical correlations. However, it is non-trivial how the yield ratio is affected by the other contributions in realistic setups of heavy-ion collisions, such as anisotropic flows [3] and the event-by-event fluctuations coming from the initial state.

In this talk, we establish a qualitative understanding of how event-by-event fluctuations affect the yield ratio [4]. We model the ``single-event'' distribution $f(x,p)$ by a superposition of $n$-Gaussian hot spots in phase space and randomize the positions and magnitudes of the hot spots from event to event. We obtain analytical formulae for the yields of light nuclei and related ratios under this setup. We investigate how each feature of the event-by-event distribution affects the yield ratio. We find that the event-by-event fluctuations increase the yield ratio, where the value takes maximum at a particular hot-spot number $n$ depending on the fireball size. We also discuss the scale separation between the critical correlations and short-range thermal fluctuations using two different sizes of hot spots. The scale of critical correlations is bounded by the finite spacetime size of the fireball. We find that the effect in the yield ratio becomes larger for larger separation of hot-spot sizes. These understandings of the yield ratio will be important in analyzing the results of future realistic analyses based on state-of-the-art dynamical models.

References
[1] K. J. Sun, L. W. Chen, C. M. Ko and Z. Xu, Phys. Lett. B 774 (2017), 103-107.
[2] STAR Collaboration, arXiv:2209.08058 (2022).
[3] S. Wu, K. Murase, S. Tang and H. Song, Phys. Rev. C 106 (2022), 034905.
[4] K. Murase and S. Wu, in preparation.

Speaker: Koichi Murase (Yukawa Institute for Theoretical Physics, Kyoto University)

20230831.murase-QM2023-Poster-LNYR-v2.pdf

17:30 Understanding Ridge behavior via kinematics between jets and medium

The Ridge behavior in high-multiplicity proton-proton collisions has been discussed a lot since it was first reported. However, small systems like proton-proton collisions are not enough to generate a medium called Quark-Gluon Plasma (QGP) in which the Ridge behavior is explained with high-order flows. In this work, we suggest the pure kinematic mechanism between jets and medium partons as tools for understanding the Ridge behavior; during jets passing through the medium, the momentum transferred from jets to medium partons makes the medium partons aligned along the direction of jets’ motion. It produces a collective motion of the medium, which is in charge of the Ridge behavior in small system collisions.

We adopt Parton Distribution from the hard scattering model (PDh) as a distribution function for initial medium partons’ momentum. The PDh is parameterized by a fallout parameter, $a$, a non-extensive parameter, $q$, and the temperature of the system, $T$; $a$ decides the shape of rapidity distribution and $q$ affects rapidity and transverse momentum distribution. And $T$ is related to scales of rapidity and transverse momentum distributions. We choose values of these free parameters by comparing PYTHIA8-string shoving simulation for pp collisions at $\sqrt{s} = 13 \rm{TeV}$ with high-multiplicity.

We set the initial conditions that jet particles with $10 \rm{GeV}$ lose their energy by $1 \rm{GeV}$ while interacting with medium partons through bremsstrahlung. Then, we calculate the cross-section with various outgoing angles of jet particles using PDh and derive the two-particle angular correlation from this. We find out that the Ridge like behaviors appear when the outgoing jets’ angle gets smaller. To integrate over the scattering angles, we calculate the cross-sections for several angles within the jet radius of 0.4 and sum them over with the weights, which are from the experimental data. We calculate the correlation and find that Ridge like behaviors exist in pp collision, compared to the experimental data. We also find $v_{2}$ within 0.025 ~ 0.045, consistent with the experimental result.

Speaker: Soyeon Cho (Inha University (KR))

QM2023_SoyeonCho.pdf

17:30 Universality of quark/gluon energy loss using Bayesian inference

Experimental data on a wide range of jet observables measured in heavy ion collisions provide a rich picture of the modification of jets as perturbative probes and of the properties of the quark-gluon plasma. However, their interpretation is often limited by the assumptions of specific quenching models, and it remains a challenge to establish model-independent statements about the universality of different jet quenching observables.

In this work, we address this issue by proposing a treatment that is agnostic to the details of the jet-medium interactions and relies only on the universality of quark and gluon quenching in different jet observables. We use Bayesian inference to constrain the parameterisation of the energy loss of quark- and gluon-initiated jets in a data-driven manner. This constraint is primarily performed using the inclusive jet pT spectrum, for which the quark/gluon fraction varies across rapidity. We then predict the observed jet asymmetry in di-jet and boson-jet measurements, providing evidence for the universality of quenching effects.

Furthermore, we examine the extracted Casimir scaling of jet quenching and the role of resolution effects in constraining the early, perturbative jet evolution using these data-driven methods. This study provides a new perspective on the universality of jet quenching in heavy ion collisions, free from the assumptions of specific models.

Speaker: Alexandre Falcão (University of Bergen)

QM2023_poster_AFalcao.pdf

17:30 Using multi-particle correlations to estimate fluctuations in jet and rare probe azimuthal anisotropies

Rare probes such as jets and heavy flavor hadrons provide unique opportunities to study the short-distance scale properties of the QGP created in heavy ion collisions. For example, recent measurements at the LHC and RHIC indicate that jet energy loss is correlated with the distance traveled through the QGP medium, and as a result, the initial geometry of the QGP. While estimates of differential azimuthal anisotropies, which we label $v^\prime_n$, have been experimentally measured for various rare probes, the fluctuations in $v^\prime_n$ have not been systematically studied.

We present a statistical formalism for the study of $v^\prime_n$ and its correlations with the integrated azimuthal anisotropies (reference flow), $v_n$, by constructing correlators of azimuthal angles from multiple rare probe objects. We then construct multivariate cumulants and moments using these correlators, which can measure fluctuations to arbitrary order in $v'_n$. The experimental methods and procedures for computing these quantities are also discussed.

To demonstrate how the measurements of the moments and cumulants can constrain the event by event distribution of $v'_n$, we propose a bivariate copula model to parametrize $v^\prime_n$ and $v_n$, and their correlations. We are able to constrain parameters in the marginal distributions for $v'_n$ by sampling the distribution and evaluating joint moments of $v^\prime_n$ and $v_n$.

Speaker: Abraham Holtermann (University of Illinois at Urbana Champaign)

Poster_2 (3).pdf

17:30 Vertex Determination in sPHENIX

The open heavy flavor program of the sPHENIX experiment at RHIC requires precise determination of the location of individual tracks in the region around the interaction vertex. Three layers of MAPS based pixels (the MVTX) surrounding the beam line are designed to provide a precision of about 10 ìm for higher momentum tracks. The tracking system also contains two layers of silicon strip detectors (the INTT) for pattern recognition, and a time-projection chamber (TPC) for momentum measurement. The corresponding beam crossing for each track is determined from the precise timing of the INTT detector. In addition to measuring the track momentum, the physics program requires determining the event vertex, finding the displacement of individual tracks from the event vertex, and locating and reconstructing decays of neutral particles that occur before the radius of the silicon pixel detectors. This poster describes the vertex determination process. The sPHENIX detector is taking data for the first time during the 2023 RHIC run, and the status of the vertex determination at the time of the conference will be discussed.

Speaker: Anthony Frawley

sPHENIX_vertexing_poster_QM23_final.pdf

Wednesday, 6 September

08:30 → 10:30 Collective Dynamics: (3)

Convener: Marco Van Leeuwen (Nikhef National institute for subatomic physics (NL))

08:30 First-Order Event Plane Correlated Directed and Triangular Flow in BES-II Au+Au Collisions at STAR

In heavy-ion collisions, the measurements of anisotropic flow coefficient ($v_n$) offer insights into collective hydrodynamic expansion and transport properties of the produced medium at higher collision energies, while they are sensitive to the compressibility of the nuclear matter and nuclear equation of state at lower collision energies. The second phase of the Beam Energy Scan program (BES-II) was carried out at RHIC to focus on the most crucial energy range from $\sqrt{s_{NN}} =7.7$ GeV to $27$ GeV in collider mode and $\sqrt{s_{NN}} =3 $ GeV to $7.7$ GeV in fixed-target mode, providing an ideal lever-arm to explore $v_n$. For such energies, the STAR BES-II upgrades enable us to measure $v_n$ in a wide pseudorapidity ($\eta$) range with high precision.

Directed flow ($v_1$) describes the collective sideward motion of produced particles and nuclear fragments in heavy-ion collisions, and it is sensitive to early non-equilibrium dynamics. The measurement of $v_1$ in a wide $\eta$ range allows us to test the phenomenon of limiting fragmentation and provides insights into the baryon-stopping mechanism. On the other hand, triangular flow ($v_3$) in nuclear collisions is often mentioned as being developed from event-by-event geometrical fluctuations in the participant region which has no correlation to the first-order event plane ($\Psi_{1}$). However, recent measurements at lower collision energies show a correlation between $v_3$ and $\Psi_1$.

In this contribution, we will show the measurement of charged particle $v_1$ over six units of $\eta$ in Au+Au collisions at $\sqrt{s_{NN}}=27$ and $19.6$ GeV and compare with transport and hydrodynamic model calculations. We will also show the results of $v_3$ in fixed-target mode for identified hadrons and light nuclei with respect to $\Psi_1$, comparing with theoretical models to identify the source of nonzero $v_3\{\Psi_1\}$ and to demonstrate its vital connection to the equation of state.

Speaker: Xiaoyu Liu

QM_Psi1_flow_ver15.pdf

08:50 Bayesian calibration of viscous anisotropic hydrodynamic simulations of heavy-ion collisions*

Due to large pressure gradients at early times, standard hydrodynamic model simulations of relativistic heavy-ion collisions do not become reliable until $O(1)$ fm/$c$ after the collision. To address this one often introduces a pre-hydrodynamic stage that models the early evolution microscopically, typically as a conformal, weakly interacting gas. In such an approach the transition from the pre-hydrodynamic to the hydrodynamic stage is discontinuous, introducing considerable theoretical model ambiguity. Alternatively, fluids with large anisotropic pressure gradients can be handled macroscopically using the recently developed Viscous Anisotropic Hydrodynamics (VAH). In high-energy heavy-ion collisions VAH is applicable already at very early times, and at later times transitions smoothly into conventional second-order viscous hydrodynamics (VH). We present a Bayesian calibration of a multi-stage dynamical evolution model built around a VAH fluid dynamic core with experimental data for $p_T$-integrated observables from Pb-Pb collisions at the LHC at $\sqrt{s_\mathrm{NN}}=2.76$ TeV. We find that the VAH model has the unique capability of constraining the specific viscosities of the QGP at higher temperatures than other previously used models [1]. We also find that the model has fewer tensions with the $p_T$-integrated input data than the previously calibrated JETSCAPE SIMS model [2]. Finally, we use the calibrated VAH and JETSCAPE SIMS models, with the four different particlization models studied in [2], to predict a number of $p_T$- differential observables, including $p_T$-spectra and anisotropic flow coefficients $v_{2,3,4}\{2\}(p_T)$ for several identified hadron hadron species. We find [3] that the $p_T$-dependence of the anisotropic flow coefficients is very sensitive to the choice of particlization model, and that the VAH predictions agree with available data much better than all available calibrated variants of the JETSCAPE SIMS model. We therefore propose the VAH approach as a superior framework for describing the dynamical evolution of heavy-ion collisions at LHC energies.
*Supported by the NSF CSSI program under grant OAC-2004601 (BAND Collaboration) and by the DOE Office of Science, Office for
Nuclear Physics under Award No. DE-SC0004286.
[1] D. Liyanage et al., arXiv:2302.14184 [nucl-th]
[2] D. Everett et al., PRL 126, 242301 (2021); and PRC 103, 054904 (2021).
[3] C. Gantenberg, research honors thesis, The Ohio State University, April 2023

Speaker: Ulrich Heinz

Heinz_QM23.pptx

09:10 Light- and Hyper-Nuclei Collectivity in Au+Au Collisions at RHIC-STAR (remote)

Studying the production and collectivity of light and hyper-nuclei in high-energy nuclear collisions in the high baryon density region can help us understand how they form and how hyperons interact with nucleons under finite pressure.

In this talk, we will present the first results on the energy dependence of directed flow $v_1$ of light and hyper-nuclei (p, d, $^3$He, and $\Lambda$, $^3_\Lambda$H, $^4_\Lambda$H) in mid-central Au+Au collisions at $\sqrt{s_{_{NN}}}$ = 3.0, 3.2, 3.5, and 3.9 GeV, along with new results on elliptic flow $v_2$ for light nuclei. All data have been collected by the STAR experiment in the fixed-target mode during the second phase of the RHIC beam energy scan program. The directed flow of hypernuclei shows a similar collision energy and mass dependence to light nuclei, as seen in the slope of $v_1$ at mid-rapidity $dv_1/dy|_{y=0}$. This suggests that the two types of nuclei are formed in a similar way. We also observe that the slope $dv_1/dy|_{y=0}$ decreases with increasing energy, with a stronger energy dependence for heavier nuclei. For light nuclei, the elliptic flow results indicate an out-of-plane expansion ($v_2 < 0$) at the lowest collision energy, whereas in-plane expansions ($v_2 > 0$) are evident at all other collision energies.

We will discuss these new results within the framework of a hadronic transport model in combination with coalescence after-burner calculations.

Speaker: Chengdong Han

ChengdongHan_QM2023_report_#666.pdf

09:30 Simulating collectivity in dense baryon matter with multiple fluids

We present a novel multi-fluid approach to simulate heavy-ion collisions in the region of RHIC Beam Energy Scan and FAIR experiments. This region of collision energies from few to few tens of GeV is particularly interesting for the exploration of dense baryon matter and search of the critical point of QCD. However, fluid-dynamical modelling here poses notable challenges. Contraction of the incoming nuclei is much weaker, which results in a long inter-penetration phase and a complex initial-state geometry. Conventional hydrodynamic models, where the fluid phase starts at a fixed proper time τ0, therefore miss the compression stage of the collision. Hence, they miss the key sensitivity to the EoS of the dense medium.
In our approach [1], we circumvent this issue by representing the incoming nuclei as two cold, baryon-rich fluids with appropriate energy and baryon densities. The newly produced matter is represented by a third baryon-free fluid, which is generated by the friction between the two colliding fluids. Our MUlti Fluid simulation for Fast IoN collisions (MUFFIN) model is implemented from scratch using a versatile 3+1 dimensional relativistic viscous hydrodynamic code vHLLE. We present benchmark calculations for Au-Au collisions at different RHIC BES energies and discuss the challenges in constructing the approach.

[1] Jakub Cimerman, Iurii Karpenko, Boris Tomášik, and Pasi Huovinen, Phys. Rev. C 107, 044902 (2023)

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

BorisTomasik_QM.pdf

09:50 Local and global polarization of $\Lambda$ hyperons across RHIC-BES energies: The roles of spin hall effect, initial condition, and baryon diffusion (remote)

We perform a systematic study on the local and global spin polarization of $\Lambda$ and $\overline{\Lambda}$ hyperons in relativistic heavy-ion collisions at beam energy scan energies via the (3+1)-dimensional CLVisc hydrodynamics model with AMPT and SMASH initial conditions. Following the quantum kinetic theory, we decompose the polarization vector as the parts induced by thermal vorticity, shear tensor and the spin Hall effect (SHE). We find that the polarization induced by SHE and the total polarization strongly depends on the initial conditions. At $7.7$GeV, SHE gives a sizeable contribution and even flips the sign of the local polarization along the beam direction for AMPT initial condition, which is not observed for SMASH initial condition. Meanwhile, the local polarization along the out-of-plane direction induced by SHE with AMPT initial condition does not always increase with decreasing collision energies. Next, we find that the polarization along the beam direction is sensitive to the baryon diffusion coefficient, but the local polarization along the out-of-plane direction is not. Our results for the global polarization of $\Lambda$ and $\overline{\Lambda}$ agree well with the STAR data. Interestingly, the global polarization of $\overline{\Lambda}$ is not always larger than that of $\Lambda$ due to various competing effects. Our findings are helpful for understanding the polarization phenomenon and the detailed structure of quark-gluon plasma in relativistic heavy-ion collisions.

Speaker: Xiang-Yu Wu (Central China Normal University)

QM2023_wxy_pol.pdf

10:10 Constraining the medium properties with the anisotropic flow and its correlations in Pb--Pb collisions at the highest energy with ALICE

Characterization of the quark--gluon plasma (QGP) created in ultrarelativistic heavy-ion collisions requires identifying observables sensitive to the different phases of the collision. Previous studies have shown that measurements of the azimuthal anisotropic flow and the complex interplay between its harmonics can provide valuable information on the QGP transport properties.

In this talk, we present the latest flow measurements done by ALICE in Pb--Pb collisions. We show the first results of the anisotropic flow coefficients of inclusive charged particles obtained at $\sqrt{s_{\rm NN}} = 5.36$ TeV, which is the highest centre-of-mass energy reached in the laboratory for heavy-ion collisions. Furthermore, the first measurements of the newly developed asymmetric cumulants at $\sqrt{s_{\rm NN}} = 5.02$ TeV indicate the existence of complex correlations between the different orders of the flow amplitudes. Finally, we highlight the first experimental results of the recent Gaussian Estimator, designed to measure correlations between symmetry planes more precisely. These results are compared with state-of-the-art hydrodynamic calculations.

Speaker: Dr Cindy Mordasini (University of Jyvaskyla (FI))

20230906_QM2023_Mordasini_Final.pdf

08:30 → 10:30 Heavy Flavor: (3)

Convener: Ralf Rapp

08:30 Probing parton formation times with $g\rightarrow c\bar{c}$ splitting

In vacuum, the spacetime location where a gluon splits into a quark-antiquark pair is not a well defined observable. In heavy-ion collisions, the `formation time’ of a splitting takes on meaning due to interactions with the medium and is a critical feature for the phenomenology of medium-modified parton showers. The $g\rightarrow c\bar{c}$ splitting is especially suited to study this formation time, as the $c\bar{c}$ virtuality is of the same order as medium effects and since the typical time is of the same order as the quark-gluon plasma lifetime. In this talk we demonstrate how to study this process from hadron distributions inside jets containing two D mesons. In particular, we show how the virtuality distribution of the original splitting depends characteristically on the formation time.

Speaker: Dr Wilke Van Der Schee (CERN)

Talk_QM2023.pdf

08:50 First energy-energy correlators measurements for inclusive and heavy-flavour tagged jets with ALICE

Many new jet substructure observables have been studied in recent years, with particular attention to those which can be calculated by perturbative QCD. N-point energy correlators are currently attracting both theoretical and experimental interest. To comprehensively study the perturbative and non-perturbative aspects of jet structure, we measured the energy-energy correlators (EEC) that emphasize the angular structure of the energy flow within jets. Defined as the energy-weighted cross section of particle pairs inside jets, the EECs as a function of pair distance show a distinct separation of the perturbative from the non-perturbative regime, revealing parton flavor dependent dynamics of jet formation as well as the confinement of the partons into hadrons. The projected 3-point correlator (E3C) is the first step in observing multi-particle correlations in jets. They encodes the shape dependence of energy flow in jets and supplement the EEC to cleanly access the pQCD region.
We present first measurements of the EECs for D0-tagged and inclusive (gluon-dominated) jets in pp and p--Pb collisions at 13 TeV and 5.02 TeV with the ALICE experiment at the LHC. By comparing our results with perturbative QCD predictions, we can measure the modification in the radiation pattern of jets due to mass effects and due to the presence of a cold nuclear medium. We also perform the first E3C measurement for inclusive jets in pp collisions at 13 TeV. This suite of measurements will serve as a baseline for future studies in heavy-ion collisions, allowing for disentanglement of the dynamics of the dead cone from interactions with the quark-gluon plasma.

Speaker: Wenqing Fan (Lawrence Berkeley National Lab. (US))

QM2023_wide_wenqing_main_Sep5.pdf

09:10 Microscopic Model for Quarkonia Production in Heavy-Ion collisions

Quarkonia are a very interesting probe for the study of thequark gluon plasma (QGP), created in ultrarelativisitc heavy-ion collisions. They can elucidate several features of the QGP, which are not accessible to other probes. These include the energy loss of color neutral states and open heavy flavour partons in the QGP, the possible recombination of heavy quarks during the expansion of the QGP and the influence of the potential between c(b) and $\bar c(\bar b)$, which is modified in the QGP environment, on the production of quarkonia.

We present the first microscopic approach for the study of quarkonia. It follows the heavy quarks from their initial production to the detection as a part of a quarkonium or as open heavy flavour hadron. After being produced in EPOS4 by (shadowing modified) initial collisions, the heavy quarks interact mutually by a potential, calculated on the lattice. When the temperature of the surrounding QGP environment falls below the dissociation temperature of the quarkonia species, a density matrix, based quantum approach of Remler [1], describes the formation and destruction of quarkonia due to its interaction with the QGP medium while the QGP medium expands.
The expanding QGP is described by the EPOS4 approach, which has shown to reproduce a multitude of experimental observables in the light hadron sector. At freeze out the free heavy quarks combine through hadronization to open heavy flavour partons, which are well reproduced in this approach. We compare the J/$\psi$ as well as the $\psi'$, produced in Remler approach with the available data on transverse momentum spectra, $R_{AA}$ and $v_2$ and analyse, including feed down corrections, how the above processes influence the production of quarkonia. First results of this approach have been published in [2].

[1] E.A.Remler, Annals Phys. 136, 293, 1981

[2] D. Villar, J. Zhao, J.Aichelin and P. Gossiaux, Pol Bernard, arXiv 2206.01308

Speaker: Joerg Aichelin (SUBATECH)

QM_aichelin.pdf

09:30 Event-by-event heavy-flavour dynamics: estimating the spatial diffusion coefficient $D_s$ from charm to the infinite mass limit

In the past years, a Quasi-Particle Model (QPM) has been developed to study charm quark dynamics in ultra-relativistic heavy-ion collisions supplying a satisfactory description of both the $R_{AA}(p_T)$ and $v_2(p_T)$ of D mesons and leading to a first evaluation of the spatial diffusion coefficient $D_s(T)$ from the phenomenology [1,2]. Within an event-by-event full Boltzmann transport approach followed by a hybrid hadronization via coalescence plus fragmentation, we will discuss for the first time $R_{AA}(p_T), v_2(p_T)$ and $v_3(p_T)$ predictions down to $p_T \rightarrow 0$ for D and B mesons as well as $\Lambda_c$ and $\Lambda_b$ at both RHIC-sPHENIX and LHC energies [3]. Furthermore the analysis is extended to higher order anisotropic flows $v_n$ of D mesons, also evaluated by using the Event-Shape-Engineering (ESE) technique [4]. We find that QPM approach is able to correctly predict not only the new observables related to charm quark sector, but also the first available data on $R_{AA}(p_T)$ and $v_2(p_T)$ of single-electron from B mesons decays measured by ALICE. The role of the large $\Lambda_c$ and $\Lambda_b$ production is relevant especially in the low $p_T$ region that is becoming accessible to sPHENIX and ALICE.
A significant breaking of the expected scaling of the thermalization time $\tau_{th}$ with $M_Q/T$ is found, studying the evolution with mass of $D_s(T)$ to better assess the comparison to lQCD calculations. Charm quark $D_s(T)$ is about $50\%$ larger than the asymptotic value for $M_Q\rightarrow \infty$, while bottom $D_s(T)$ is only $20\%$ higher. Such a behaviour entails for $M_Q\rightarrow \infty$, a $D_s(T)$ which is consistent within the current uncertainty to the most recent lattice QCD calculations with dynamical quarks and allows to envisage for bottom quark a thermalization time smaller than the one from $M_Q/T$ scaling.

[1] X. Dong and V. Greco, Prog. Part. Nucl. Phys. 104 (2019), 97-141.
[2] R. Rapp, P. B. Gossiaux, A. Andronic, R. Averbeck, S. Masciocchi, A. Beraudo, E. Bratkovskaya, P. Braun- Munzinger, S. Cao and A. Dainese, et al., Nucl. Phys. A 979, 21-86 (2018).
[3] M.L.Sambataro, V. Minissale, S. Plumari and V. Greco, e-Print: 2304.02953 (PLB submitted).
[4] M.L.Sambataro, Y, Sun, V. Minissale, S.Plumari and V.Greco, Eur.Phys.J.C 82 (2022) 9, 833 .

Speaker: Vincenzo Minissale

QM2023_MINISSALE.pdf

09:50 Heavy-flavor transport and hadronization in proton-proton collisions

Recent experimental results on the Λ+c/D0 ratio in proton-proton collisions – strongly enhanced compared to expectations relying on universal fragmentation fractions/functions in different colliding system, from e+e− to pp – led to speculations about possible medium effects affecting hadronization, previously considered a distinctive feature only of heavy-ion collisions. Here we show how the assumption of the formation of a small, deconfined and expanding fireball also in pp collisions, in which charm quarks can undergo rescattering and hadronization, allows one to qualitative reproduce unexpected experimental findings in the heavy-flavor particle ratios and distributions. For this purpose we apply to the proton-proton case the same in-medium hadronization mechanism previously developed to address heavy-ion collisions and based on local color-neutralization via recombination of charm quarks with nearby opposite color charges from the background fireball. In our model the presence of diquark excitations in the hot medium favors the formation of charmed baryons and the recombination process, involving quite collinear partons from the same fluid cell, turns out to be an efficient mechanism to transfer the collective flow of the system to the final charmed hadrons.
The model -- described in detail in EPJC 82 (2022) 7, 607 -- allowed us to provide a good description of the charmed-hadron ratios and momentum-distribution in nucleus-nucleus collision. Its extension to the proton-proton case provides a consistent explanation for the enhanced Λ+c/D0 ratio observed in these collisions and leads to other interesting results for the charmed-hadron momentum distributions -- entering into the definition of the R_AA, in which the pp result can no longer be considered as the no-final-state-effect benchmark -- and for their elliptic-flow coefficient, reflecting the initial deformation of the fireball.
Having validated our modelling of the initial state of the fireball and its hydrodynamic evolution against the measured soft-particle multiplicity in pp collisions, we believe our results are pretty robust and provide a unified picture of heavy-flavor production from pp to AA collisions.

Speaker: Andrea Beraudo (INFN, sezione di Torino (IT))

beraudo-QM.pdf

10:10 A fluid-dynamic approach to heavy-quark diffusion in the quark-gluon plasma

Heavy quarks (i.e. charm and beauty) are powerful tools to characterize the quark-gluon plasma (QGP) produced in heavy-ion collisions. Although they are initially produced out of kinetic equilibrium via hard partonic scattering processes, recent measurements of anisotropic flow of charmed hadrons pose the question regarding the possible thermalization of heavy quarks in the medium. Our recent work [1] has provided new insights on the level of thermalization of charm and beauty quarks in the QGP. In particular, exploiting a mapping between transport theory and fluid-dynamics, we have shown how a fluid-dynamic description of the dynamics of charm quarks in the QCD plasma is feasible. Inspired by recent lattice-QCD calculations [2], we will show how a partial thermalization within the lifetime of the QGP is expected also for beauty quarks.
We will present results for spectra of charmed hadrons obtained with a fluid-dynamic code (FluiduM [3]) coupled with the conservation of a heavy-quark - antiquark current in the QGP. We will also show preliminary calculations for beauty spectra. We compare our calculations with the most recent experimental data providing further constraints on the heavy-quark spatial diffusion coefficient [4].
This work is funded via the DFG ISOQUANT Collaborative Research Center (SFB 1225).

[1] Phys.Rev.D 106 3, 034021 (2022)
[2] e-Print: 2302.08501 [hep-lat]
[3] Phys. Rev. C 100, 014905 (2019)
[4] Capellino, Dubla, Floerchinger, Grossi, Kirchner, Masciocchi; in preparation

Speaker: Federica Capellino

Capellino_Federica_QM2023.pdf

08:30 → 10:30 Jets: (3)

Convener: John William Harris (Yale University (US))

08:30 Measurements of the substructure and radius dependence of jet quenching in PbPb collisions

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 comprehensive ATLAS measurements of jet suppression and substructure performed using various jet radii and grooming techniques. New measurements of inclusive jet suppression ($R_{AA}$) in heavy-ion collisions are presented for jets reconstructed with different radii ($R$=0.2, 0.3, 0.4, 0.6, 0.8 and 1.0) in Pb+Pb and $pp$ collisions at $\sqrt{s_{NN}} = 5.02$ TeV. We will also present new results of the jet substructure which use Soft-Drop grooming procedure to identify the hardest parton splitting in the jet. The measurements are performed using different jet constituents such as charged tracks, smaller R calorimeter jets, and novel objects reconstructed using tracker and calorimeter information. The jet suppression is characterized using RAA and presented as a function of its transverse momentum ($p_{\mathrm{T}}$), the angle of the hardest splitting ($r_{g}$), and the corresponding transverse momentum scale ($\sqrt{d_{12}}$). These new measurements, along with theory comparisons, will elucidate the mechanisms of jet suppression, medium effects, and energy recovery in the QCD medium.

Speaker: Dhanush Anil Hangal (Lawrence Livermore Nat. Laboratory (US))

DAH_QM23.pdf

08:50 Studies of jet quenching and medium response using photon+jet events with ATLAS

Partons traversing the hot and dense medium of deconfined color charges produced in collisions of heavy nuclei are expected to lose their energy primarily through medium-induced gluon bremsstrahlung. As a result, the amount of induced energy loss is expected to depend on the QCD color charge carried by the parton, i.e. depend on whether it is a quark- or a gluon-initiated jet. In this talk, photon+jet events taken with the ATLAS detector in Pb+Pb and pp are used to constrain the color-charge dependence of jet energy loss. First, ATLAS presents the finalized result on the nuclear modification factor RAA for photon-tagged jets. By comparing this measurement to the RAA for inclusive jets, one can exploit the known difference in the quark-/gluon-initiated jet fraction between these two samples and extract the QCD color-charge dependence. Second, ATLAS presents a new measurement of photon plus two jet production in Pb+Pb collisions as compared to $pp$, where the configuration of quark+gluon jet pair is expected to dominate. Measurements of the total jet-to-photon $p_{\mathrm{T}}$ ratio, the two-jet $p_{\mathrm{T}}$ asymmetry, and the jet opening angle are presented, providing novel information on the parton-QGP interaction. Finally, the study of photon+jet+hadron correlations in angular space, expected to be sensitive to medium response, is presented for the first time. All results are compared to a suite of theoretical calculations.

Speaker: Christopher Mc Ginn (Massachusetts Inst. of Technology (US))

qmATLASPhotonPlusJetsHI_CFM_20230906.pdf

09:10 Measurement of in-medium modification of energy-space structure of jets via $\gamma$ and $\pi^0$ triggered hadrons in Au+Au collisions at RHIC

Since the discovery of the jet quenching at RHIC, the in-medium interaction of hard scattered partons with the nuclear medium created by high-energy heavy-ion collisions has been an excellent tool to understand not only the transport properties of the medium but also its time evolution towards hadronization. The multi-differential measurement of the high momentum two-particle correlations can probe a particular space-time window as a function of energy transfer. Comparing the correlations with the prompt photon triggered hadron spectra, one can extract the property of the medium from various aspects and contribute to distinct models. The PHENIX experiment at RHIC has collected its highest statistics of the $\gamma$ and $\pi^0$ triggered hadron events in Au+Au collisions at $\sqrt{s_{NN}}$=200GeV in the RHIC Year-2014 run, and measured not only the inclusive spectra of the triggered hadrons but also the angle and energy dependent $I_{AA}$ and $D_{AA}$. We will discuss the in-medium modification of the energy-space structure of the jets at the RHIC energies with the results obtained.

Speaker: Megan Connors (Georgia State University)

Connors_QM2023v4.pdf

09:30 Enhancement of baryon-to-meson ratios around jets as a signature of medium response (remote)

We present a unique signal of jet-induced medium excitations: the enhancement of baryon-to-meson ratios around the quenched jets [1]. To illustrate this, we study jet-particle correlations and the distributions of jet-induced identified particles with respect to the jet direction in Pb+Pb collisions at the LHC via a multi-phase transport model. We find a strong enhancement of baryon-to-meson ratios for associated particles at intermediate transverse momentum around the triggered jets in Pb+Pb collisions relative to p+p collisions, due to the coalescence of jet-excited medium partons. Since the lost energy from jets can diffuse to large angles, such baryon-to-meson-ratio enhancement is more pronounced for larger relative distance from the jet axis. We argue that the experimental confirmation of the enhancement of jet-induced baryon-to-meson ratios around the jets will provide an unambiguous evidence for the medium response to jet quenching in heavy-ion collisions.
[1] A. Luo, Y. X. Mao, G. Y. Qin, E. K. Wang, H. Z. Zhang, Phys.Lett.B 837 (2023) 137638

Speaker: Guang-You Qin (Central China Normal University)

Qin_BM_MR_v1.pdf

09:50 Study of jet energy redistribution and broadening using acoplanarity and planar flow measurements in pp and Pb--Pb collisions with ALICE

The measurement of jets recoiling from a trigger hadron (hadron+jet) provides unique probes of medium-induced modification of jet production. Jet deflection via multiple soft scatterings with the medium constituents may broaden the azimuthal correlation between the trigger hadron and the recoiling jet. In addition, the tail of this azimuthal correlation may be sensitive to single-hard Moli`ere scatterings off quasi-particles in the medium. The R-dependence of recoil jet yield probes jet energy loss and intra-jet broadening. In inclusive jet populations, the principle axis of energy flow in the plane transverse to the jet axis examines the correlation of particles outside the jet cone with the energy of the jet. This and the hadron+jet results may be sensitive to wake effects due to jet-medium energy transfer at low $p_\mathrm{T}$.
This talk presents measurements of the semi-inclusive distribution of charged-particle jets recoiling from a trigger hadron in pp and Pb--Pb collisions. We observe that the jet yield at low $p_\mathrm{T}$ and at large azimuthal angle between the trigger hadron and jet is significantly enhanced in Pb--Pb collisions with respect to pp collisions, which we interpret through comparisons to model calculations. In addition, the first correlations of tracks with the principle direction of energy flow in the plane transverse to the jet will be presented.

Speaker: Jaime Norman (University of Liverpool (GB))

Jnorman_QM23_hJet_final.pdf

10:10 Probing the dynamics of color coherence with energy correlators

We present a novel approach to jet substructure in heavy-ion collisions formulated in terms of correlation functions of flux operators (energy correlators). This approach is based on the insight that the time scales in the jet’s evolution are imprinted into the angular scales of the correlator spectra. We study the two-point correlator of an in-medium massless quark jet, showing its sensitivity to the resolution scale of the QGP: the energy scale at which in-medium emissions start to be resolved by the medium (color coherence). Our calculation incorporates vacuum radiation resummed at next-to-leading log accuracy together with the leading order contribution in medium-induced splittings evaluated through either the BDMPS-Z multiple scattering or the GLV single scattering framework.

Speaker: Carlota Andres (Ecole Polytechnique, CPHT)

andrescQM2023.pdf

08:30 → 10:30 Light Flavor: (2)

Convener: Anju Bhasin (University of Jammu (IN))

08:30 Accessing strong interaction in three-hadron systems with ALICE

The ALICE Collaboration presents a new experimental approach to explore the interactions in three-hadron systems by analyzing femtoscopic correlation functions of deuteron-hadron pairs produced in high-multiplicity pp collisions at $\sqrt{s}$ = 13 TeV and in Pb--Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ $\mathrm{TeV}$ at the LHC. The measured p-d correlation function can only be explained if the three nucleons are considered as explicit degrees of freedom in the calculations, demonstrating the sensitivity of the correlation function to the full three-nucleon dynamics. Additionally, the measurement of $\mathrm{K}^{+}\mathrm{d}$K+d and $\mathrm{K}^{-}\mathrm{d}K$-d correlations in Pb--Pb collisions at different centralities has made it possible to extract for the first time the scattering lengths and the source radii of such pairs, which have been awaited for more than 40 years. Future plans for the study of three-body dynamics at the LHC will be discussed. In particular, the precise measurement of three-hadron correlations, such as p-p-p and p-p-$\Lambda$, requires the large data sample that will be collected during the Run 3. The p-p and p-$\Lambda$ pair correlations are currently under study as they provide the benchmark for measuring the p-p-p and p-p-$\Lambda$ triplets in pp collisions at $\sqrt{s}$ = 13.6 TeV.

Speaker: Bhawani Singh (Technische Universitaet Muenchen (DE))

QM_Bhawani2023.pdf

08:50 Measurements of (anti)(hyper)nuclei with ALICE

The investigation of the production mechanism of light (anti)(hyper)nuclei in ultrarelativistic hadronic collisions is one of the main topics in modern nuclear physics. The ALICE Collaboration has significantly contributed to this specific field of research with systematic measurements of the production of (anti)(hyper)nuclei in different collision systems and centre-of-mass energies provided by the Large Hadron Collider. Measurements of the properties of hypernuclei, such as their lifetimes and binding energies, provide information on the hadronic interaction between hyperons and nucleons, which is complementary to that obtained from correlation measurements.

In this contribution, recent results on the production of (anti)(hyper)nuclei measured with ALICE during the LHC Run 2 in different collision systems will be presented. These results will be discussed within the context of the statistical hadronization model and baryon coalescence. For the first time, the observations of the (anti)hyperhydrogen-4 and (anti)hyperhelium-4 in Pb--Pb collisions at 5.02 TeV will be shown. Moreover, new results on (anti)(hyper)nuclei measurements obtained using the LHC Run 3 data will also be presented.

Speaker: Ivan Vorobyev (CERN)

20230906_QM_antihypernuclei_IvanVorobyev.pdf

09:10 High-$p_t$ suppression in small systems

We present first results for light and heavy flavor high-$p_T$ hadron suppression from a short path length corrected energy loss model in $p+p$, $p+A$, and $A+A$ collisions at RHIC and the LHC. We find that the short path length corrections to final state radiative energy loss for light flavor hadrons predict nontrivial enhancement such that high multiplicity $R_{pA} > 1$, consistent with data. We further systematically check the consistency of the assumptions—such as collinearity, softness, and large formation time—made in the derivation of radiative energy loss, with the final numerical model. We find that the large formation time approximation breaks down at modest to high momenta $p_T \geq 30~\mathrm{GeV}$. Comparison to data at higher momenta thus requires a rederivation of GLV, DGLV, and short path length correction results; with the large formation time assumption relaxed. We also show that the usual elastic energy loss treatment vastly overpredicts the suppression in small systems; thus, small path length corrections to elastic energy loss are required for quantitative comparison to data in small systems.

Speaker: Cole Faraday

ColeFaradayQM23.pdf

09:30 Cluster formation near midrapidity - can the mechanism be identified experimentally?

Authors: G. Coci, S. Glässel, V. Kireyeu, J. Aichelin, C. Blume, V. Kolesnikov, V. Voronyuk and E. Bratkovskaya

The formation of weakly bound clusters and hypernuclei in the hot and dense environment at midrapidity is one of the surprising phenomena observed experimentally in heavy-ion collisions from low SIS to ultra-relativistic LHC energies. This is also known as the `ice in a fire' puzzle. Three approaches have been advanced to describe the formation of clusters: cluster formation during the entire heavy-ion collision by potential interactions between nucleons ('potential mechanism') and deuteron production by catalytic hadronic reactions ('kinetic mechanism') as well as by coalescence at kinetic freeze-out.

We present here results from PHQMD [1,2], a novel microscopic n-body transport model based on the QMD propagation of the baryonic degrees of freedom with density dependent 2-body potential interactions. The clusters, formed via 'potential' mechanism, are recognized by the Minimum Spanning Tree (MST) algorithm which is identifying bound clusters by correlations of baryons in coordinate space.
The PHQMD approach allows for studying in the same framework the two above mentioned mechanisms, to investigate how and when clusters are formed and finally for comparing the results with present data from GSI to RHIC energies.

We report on our recent findings, in particular that:

• The clusters produced via coalescence and potential mechanisms are created after the fast hadrons are escaped from the reaction zone, i.e. clusters remain in transverse direction closer to the center of the heavy-ion collision than free nucleons. Thus, since the 'fire' is not at the same place as the 'ice', cluster can survive which explains the ice in the fire puzzle. Our PHQMD results for deuteron production by potential mechanism agree quantitatively with results of UrQMD for coalescence deuterons, thus, this finding doesn't depend on the transport model involved.

• For the `kinetic' deuterons the PHQMD results agrees with those from SMASH - if one limits the catalytic hadronic reaction channels to those realized in SMASH, however, accounting for all isospin channels of the various $\pi NN\leftrightarrow \pi d$, $NNN\leftrightarrow N d$ reactions leads to an enhanced production of deuterons.

• On the other hand, we find that considering the quantum nature of the deuteron -- by taking into account the finite size properties of the deuteron by means of an excluded volume in coordinate space and by the projection onto the deuteron wave function in momentum space -- reduces substantially the kinetic deuteron production in a dense medium as encountered in heavy-ion collisions. This makes the 'kinetic' mechanism sub-dominant compared to the deuteron formation by potential interactions between nucleons.

• The sum of kinetic deuterons and that produced in by potential interactions reproduces well the experimental data from SIS to RHIC energies

• The coalescence deuterons and potential deuterons have only about 20\% of the nucleons in common. This leads to a different rapidity distribution and to a different $p_T$-distribution at low $p_T$. This difference can be used to identify experimentally the production mechanism which is realized in nature.

• Heavier clusters like $t$, $^3He$ and $^4He$ as well has hypernuclei are also well reproduced by the potential mechanism

Some of the presented result have been published in Refs. [3,4,5].

[1] J. Aichelin, E. Bratkovskaya, A. Le Fevre, V. Kireyeu, V. Kolesnikov, Y. Leifels, V. Voronyuk and G. Coci, Phys. Rev. C 101 (2020) 044905, [arXiv:1907.03860 [nucl-th]].
[2] S. Glässel, V. Kireyeu, V. Voronyuk, J. Aichelin, C. Blume, E. Bratkovskaya, G. Coci, V. Kolesnikov and M. Winn, Phys.Rev. C 105 (2022) 1, [arXiv:2106.14839 [nucl-th]].
[3] V. Kireyeu, J. Steinheimer, J. Aichelin, M. Bleicher and E. Bratkovskaya, Phys. Rev. C 105 (2022) 044909, [arXiv:2201.13374 [nucl-th]].
[4] G. Coci, S. Glässel, V. Kireyeu, J. Aichelin, C. Blume, E. Bratkovskaya, V. Kolesnikov and V. Voronyuk, [arXiv:2303.02279 [nucl-th]].
[5] V. Kireyeu, G. Coci, S. Glässel, J. Aichelin, C. Blume and E. Bratkovskaya, [arXiv:2304.12019 [nucl-th]].

Speaker: Elena Bratkovskaya (GSI, Darmstadt)

Elena_Bratkovskaya_QM2023.pdf

09:50 Large isospin symmetry violation in kaon production

The recent measurements of NA61/SHINE at the CERN SPS revealed a large violation of isospin symmetry. The ratio of charged to neutral kaons was measured to be 1.22 ± 0.06 in Ar+Sc collisions at 75A GeV/c. This contribution will present the experimental details of this intriguing result. It will also compare it to the world data on charged to neutral kaons ratio in nucleus-nucleus collisions. Finally, based on the recent theoretical work, it will quantitatively show that the observed isospin symmetry violation is large.

Speaker: Wojciech Brylinski (Warsaw University of Technology (PL))

Brylinski_QM2023.pdf

10:10 $\Sigma^0$ reconstruction in Ag+Ag collisions at 1.58 AGeV with the HADES experiment

In this contribution we will discuss the production of $\Sigma^0$ baryons in Ag+Ag collisions at 1.58 AGeV beam energy measured by HADES. Although, the High Acceptance DiElectron Spectrometer (HADES) at GSI was primarily designed to measure Di-Electrons, it also features a very rich program measuring hadronic probes in the region of moderate temperature and high-baryon density in the QCD phase diagram. Recently, the spectrometer was upgraded with a new RICH photon detector and an electromagnetic calorimeter. While the first allows for a strongly improved electron identification, the latter allows for photon measurements in HADES for the first time without involving the conversion process.

Those experimental upgrades allow for a clear reconstruction of the $\Sigma^0$ baryon in Ag+Ag collisions at 1.58 AGeV beam energy in the electromagnetic decay to Lambda and photon. This collision energy is right at threshold for Lambda production, however it's below for the Sigma0. In p+p collisions a rise of the $\Lambda/\Sigma^0$ ratio is measured, which, if also existent for A+A collisions, would have strong impact on the extraction of ($T,\mu_B$) values from thermal models as the $\Lambda/\Sigma^0$ is usually fixed following isospin symmetry. The analysis presented in this work allows for a $\Sigma^0$ signal with a significance of roughly 10 in the $\Lambda \gamma$ channel while no signal is observed in the $\Lambda e^{\pm}$ channel reconstructing conversion photons and, if existing, Dalitz decays. Full acceptance and efficiency studies allow for a fully corrected $\Sigma^0$ production yield, extracting a $(\Lambda+\Sigma^0)/\Sigma^0$ ratio. This value is compared to and used in thermal models applied to HADES data or GiBUU analyzing the influence of the NN threshold in Ag+Ag.

Speaker: Marten Becker

QuarkMatter23_Houston_MartenBecker.pdf

08:30 → 10:30 UPC: (1)

Convener: Prof. Daniel Tapia Takaki (University of Kansas)

08:30 Probing small-$x$ nuclear gluonic structure via coherent charmonium photoproduction in ultraperipheral PbPb collisions at CMS

Gluons are found to become increasingly dominant constituents of nuclear matter when being probed at higher energies or smaller Bjorken-$x$ values. This has led to the question of the ultimate fate of nuclear gluonic structure at extreme density. In ultraperipheral collisions (UPCs) of relativistic heavy ions, the coherent heavy-flavor vector meson production via photon-nuclear interactions is of particular interest, since its cross section is sensitive to the nuclear gluon density. However, in symmetric UPCs, a two-way ambiguity in determining the photon-emitter and the target prevents the extraction of contributions involving high- and low-energy photon-nucleus interactions. This limitation, therefore, had so far reduced our capability to probe the extremely small-$x$ regime. In this talk, we will present the first measurement of coherent charmonium photoproduction, where the two-way ambiguity is solved by implementing a forward neutron tagging technique using UPC lead-lead collisions recorded by the CMS experiment at 5.02 TeV. Results of coherent J/$\psi$ production and a new measurement of coherent $\psi\mathrm{(2S)}$ production will be presented. The new results on $\psi\mathrm{(2S)}$ provide a heavier mass scale thus complementing the results on J/$\psi$ toward smaller Bjorken-$x$ values. We will discuss the physics implications of these results, as well as exciting opportunities in future LHC heavy ion runs.

Speaker: Jiazhao Lin (Rice University (US))

20230906_QuarkMatter_v2.pdf

08:50 Exclusive $J/\psi$ Photoproduction and Entanglement-Enabled Spin Interference in Ultra-Peripheral Collisions at STAR

In ultra-peripheral collisions (UPCs), exclusive vector meson photoproduction, e.g., $\rho^{0}$ and $J/\psi$, has been considered one of the most sensitive probes to the gluon structure in heavy nuclei. Recently, it was discovered that the linear polarization of the photons involved in these processes can enable measurements of the nuclear geometry through the so-called entanglement-enabled spin interference with the $\rho^{0}$ meson. However, the possibility that the interference can happen at the level of vector mesons cannot be falsified using $\rho^{0}$ data. The longer lifetime and non-localized wave function of $J/\psi$ at the time of its decay would not result in an interference pattern similar to the $\rho^0$ unless the entanglement occurs between the photon and the Pomeron phases emitted from each nucleus, providing an opportunity to study the source of the entanglement.

In this talk, we will report first measurements of the differential cross sections of photoproduced $J/\psi$ as functions of rapidity $y$ and $p^{2}_{T} \approx -t$ (up to $2.25~\rm{(GeV/c)^2}$) in Au+Au UPCs at $\sqrt{s_{_\mathrm{NN}}}=200$ GeV recorded by STAR. The results will be presented for different combinations of neutron emission detected in zero degree calorimeters, which can be used to resolve the photon energy ambiguity. These data provide important constraints for nuclear parton distribution functions and sub-nucleonic shape fluctuations in heavy nuclei in the kinematic range $x_{\rm{parton}}\sim0.015-0.03$. We also present the first measurement of the interference pattern for those photoproduced $J/\psi$. The observation of a positive $\cos(2\Delta \phi)$ modulation in the angular separation between the $J/\psi$ and one of its decay daughters is predicted to be a signature of entanglement between the photon and Pomeron phases. Finally, we will provide an outlook for significantly improved measurements anticipated during the final RHIC runs in 2023-2025.

Speaker: Ashik Ikbal Sheikh

ashik_upc_slides_qm2023.pdf

09:10 First global study of super dense gluonic matter with UPCs by ALICE

ALICE has been the first experimental collaboration observing a moderate nuclear suppression down to low Bjorken x in lead nuclei using coherent J/$\psi$ photoproduction. In this talk, we present new results extending the studies of the photonuclear cross section by covering the Bjorken-x interval of $1.1 \cdot 10^{-5} < x < 3.3 \cdot 10^{-2}$, corresponding to the photon-nuclear energies $17 < W_{\gamma Pb} < 920$~GeV. This is achieved by using multiple methods to extract the energy dependence, including new results on the forward neutron emission accompanying the coherent photoproduction process. These new results, combined with ALICE measurements of J/$\psi$ off proton target, probe the gluonic structure of the lead nuclei at the lowest Bjorken-x possible with any current experiment, challenging both gluon saturation and shadowing models to describe the data.

Speaker: Simone Ragoni (Creighton University (US))

QM-ragoni.key

QM-ragoni.pdf

09:30 Looking for QGP signatures in ultraperipheral PbPb collisions

Ultraperipheral collisions of relativistic heavy ion beams lead to a diverse set of photon-nucleus (photonuclear) interactions. The measurements of particle production in photonuclear reactions can shed light on the QCD dynamics of the novel, extremely asymmetric colliding systems, with energies between those available at RHIC and the LHC. Previous studies by ATLAS indicate significant elliptic and triangular flow coefficients in these events. Thus, it is imperative to check these events for other potential QGP signatures including radial flow, strangeness enhancement, and enhanced baryon/meson production. This talk presents the measurement of charged hadron and identified particle yields ($K^0_S$, $\Lambda$, and $\Xi$) in photonuclear collisions using 5.02 TeV Pb+Pb data collected in 2018 by ATLAS. The charged hadron and identified particle yields are presented as a function of pseudorapidity and transverse momentum in different categories of event multiplicity. The results are compared with 5.02 TeV p+Pb data collected in 2016 by ATLAS at the same event multiplicities. The results are also compared with calculations from DPMJET and hydrodynamic-based models. These comparisons enable detailed characterizations of photonuclear collision properties, including the photon energy distribution and whether small QGP droplets may be formed.

Speaker: Sruthy Jyothi Das (University of Colorado Boulder (US))

QM23_090623_sruthydas.pdf

09:50 Quarkonia production in ultra-peripheral PbPb collisions at LHCb

Measurements of quarkonia production in peripheral and ultra-peripheral
heavy-ion collisions are sensitive to photon-photon and photon-nucleus interac-
tions, the partonic structure of nuclei, and to the mechanisms of vector-meson
production. LHCb has studied production of the J/ψ and ψ(2S) charmonium
states in peripheral and ultra-peripheral collisions using PbPb data at forward
rapidity, obtaining 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: Xiaolin Wang (South China Normal University (CN))

xiaolinw_QM2023_v2.pdf

10:10 Illuminating the impact-parameter dependence of UPC dijet photoproduction

In this talk, we present new NLO pQCD predictions for photoproduction of dijets in UPC PbPb collisions at 5.02 TeV with realistic photon flux and up-to-date nuclear parton distribution functions (nPDFs). We calculate nuclear form factor for the impact parameter-dependent flux using Woods-Saxon density profile and compare the result to a widely-used point-like approximation. We show that a significant portion of the measured dijets at large measurable $z_\gamma$ (correspondingly small $x_A$) originate from events with relatively small impact parameters of the order of few nuclear radii, and the cross section predictions therefore become sensitive to the modelling of the nuclear geometry and photon flux close to the source nucleus. We comment on the implications of these findings for the use of UPC dijets as a constraint of nPDFs.

Speaker: Petja Paakkinen

QM2023_Paakkinen_UPC_dijets.pdf

10:30 → 11:00 Coffee Break

11:00 → 13:00 Astrophysics: (1)

Convener: Prof. Jorge Noronha (University of Illinois at Urbana-Champaign)

11:00 Bayesian analysis of nontrivial features in the speed of sound inside neutron stars in light of astrophysical and pQCD constraints

Functional forms of the neutron star Equation of State (EoS) are required to extract the viable EoS band from neutron star observations. Realistic nuclear EoSs, containing deconfined quarks or hyperons, present nontrivial features in the speed of sound such as bumps, kinks, and plateaus. Using modified Gaussian processes to model EoSs with nontrivial features, we show in a fully Bayesian analysis incorporating measurements from X-ray sources, gravitational wave observations, and perturbative QCD results that these features are compatible with current constraints. We find nontrivial behavior in the EoS plays a role in understanding the possible phase structure of neutron stars at densities around 2 $n_{\rm sat}$ [1]. Lastly, we perform a large-scale systematic analysis of the impact of perturbative QCD constraints when they are applied beyond the maximal central densities realized in realistic neutron star EoSs.

[1] D. Mroczek et al, arXiv:2302.07978

Speaker: Débora Mroczek (University of Illinois at Urbana-Champaign)

Mroczek_QM_2023_v2.pdf

11:20 Far-from-equilibrium relativistic hydrodynamics in neutron-star mergers

In binary neutron-star mergers, violent changes in density drive the proton fraction out of equilibrium at timescales of milliseconds, comparable to those required by weak interactions to restore beta equilibrium. As a result, the pressure evolves out of phase with the density oscillations, giving rise to dissipative work that can be modeled as an effective bulk-viscous correction [1,2]. Near beta equilibrium, the correction to the pressure is known to follow an Israel-Stewart-like equation of motion, with transport coefficients determined by the equation of state outside beta equilibrium and weak-interaction rates [2]. However, it is not clear if that is the regime that actually occurs in neutron star mergers [3]. In this work, we shed new light on this problem in the following way. First, we show how this hydrodynamic description can be extended far from equilibrium, without approximations, allowing us to model neutron star matter that is arbitrarily far from beta equilibrium. We find that for realistic equations of state [4], the linear approximation in deviations from equilibrium commonly assumed in the field [1] has very limited applicability and, thus, realistic neutron star mergers are indeed in the far-from-beta equilibrium regime. We calculate the resulting far-from-equilibrium transport coefficients for equations of state that satisfy the latest constraints from multi-messenger observations from LIGO/VIRGO and NICER. Our results pave the way for novel systematic studies of viscous effects in numerical simulations of binary mergers [3].

[1] M. G. Alford, L. Bovard, M. Hanauske, L. Rezzolla and K. Schwenzer,``Viscous Dissipation and Heat Conduction in Binary Neutron-Star Mergers,'' Phys. Rev. Lett. 120, no.4, 041101 (2018).

[2] L. Gavassino, M. Antonelli and B. Haskell, ``Bulk viscosity in relativistic fluids: from thermodynamics to hydrodynamics,''
Class. Quant. Grav. 38, no.7, 075001 (2021).

[3] E. R. Most, A. Haber, S. P. Harris, Z. Zhang, M. G. Alford and J. Noronha, ``Emergence of microphysical viscosity in binary neutron star post-merger dynamics,''
[arXiv:2207.00442 [astro-ph.HE]].

[4] W. C. Chen and J. Piekarewicz, ``Building relativistic mean field models for finite nuclei and neutron stars,''
Phys. Rev. C 90, no.4, 044305 (2014).

Speaker: Yumu Yang

Yumu_Yang_QM2023.pdf

11:40 Reaching percolation and conformal limits in neutron stars

In this talk, I discuss the statistically determined equation of state of dense matter that fulfills the multimessenger constraints and determine the properties of dense matter found in neutron stars. I demonstrate that the speed of sound and trace anomaly are driven towards their conformal values at the center of maximally massive NSs. I argue that the local peak of the speed of sound is located at values of energy and particle densities consistent with deconfinement and percolation conditions in QCD matter. I also analyze fluctuations of the net-baryon number density in the context of possible remnants of critical behavior.

talk based is on:
M. Marczenko, L. McLerran, K. Redlich, C. Sasaki, Phys.Rev.C 107 (2023) 2, 025802

Speaker: Chihiro Sasaki

QM.pdf

12:00 Equations of state for neutron stars with phase transitions of different orders

In this contribution, we describe new chemically-equilibrated charge neutral hybrid equations of state for neutron stars. They present a phase transition to deconfined quark matter and are differentiated by the particle population considered and how these particles interact. While some equations of state contain just nucleons and up, down-quarks, others also contain hyperons, Delta baryons, and strange quarks. The hybrid equations of state, together with corresponding hadronic ones, are available on the CompOSE repository and can be used for different astrophysical applications. Besides studying first-order phase transitions, we also explore the possibility of higher-order phase transitions and investigate possible astrophysical implications, e.g., for neutron-star mergers.

[1]Equations of state for neutron stars with phase transitions of different orders
A. Clevinger, M. Albino, V. Dexheimer, P. Hammond, D. Radice, C. Providencia
In-preparation.

[2] Hybrid Equations of State for Neutron Stars with Hyperons and Deltas
A. Clevinger, J. Corkish, K. Aryal, V. Dexheimer
Eur. Phys. J. A 58 (2022) 5, 96, e-Print: 2205.00559 [astro-ph.HE]

Speaker: Alexander Clevinger

QM_Clevinger_2023 [Autosaved].pdf

12:20 Causal and Stable Magnetohydrodynamics

We derive the equations of motion of relativistic magnetohydrodynamics from the Boltzmann equation using the method of moments. We generalize the references [1, 2] and consider a fluid to be a locally neutral system composed of a particle with opposite charges, with vanishing dipole moment or spin, so that the fluid has vanishing magnetization and polarization.

We demonstrate that the magnetohydrodynamical equations of motion become dramatically different for this more realistic system. The shear stress tensor no longer obeys a single differential equation: it breaks into three non-degenerate components with respect to the magnetic field each evolving according to different dynamical equation. For large magnetic fields we further show that the solutions of this theory display oscillatory behaviour that can no longer be described by an Israel-Stewart-like theory. Finally, we investigate the derived equations in a Bjorken flow scenario.

---

[1] Denicol, Gabriel & Molnár, Etele & Niemi, Harri & Rischke, Dirk. (2019). Physical Review D. 99. 10.1103/PhysRevD.99.056017. DOI: 10.1103/PhysRevD.99.056017

[2] Denicol, Gabriel & Huang, Xu-Guang & Molnár, Etele & Monteiro, Gustavo & Niemi, Harri & Noronha, Jorge & Rischke, Dirk & Wang, Qun. (2018). Physical Review D. 98. 10.1103/PhysRevD.98.076009. DOI: 10.1103/PhysRevD.98.076009

Speaker: Ms Khwahish Kushwah (Universidade Federal Fluminense (UFF), Rio de Janeiro, Brazil)

Khwahish_kushwah_QM23.pdf

12:40 Constraining (anti)nuclei measurements relevant for astrophysics with ALICE

Antinuclei can be produced in space either by collisions of high-energy cosmic rays with the interstellar medium or from the annihilation of dark matter particles stemming into standard model particles. High-energy hadronic collisions at accelerators create a suitable environment for producing light (anti)nuclei. Hence, studying the production of antinuclei in pp collisions at the LHC can provide crucial insights into the production mechanisms of nuclear states in our Universe. Recent measurements of the production of antinuclei as a function of rapidity in pp collisions at $\sqrt{s}$ = 13 TeV have been carried out with ALICE to allow for the extrapolation of the nuclear production models at forward rapidity, region of interest for astrophysics.
Recent results on the cross-section of nuclei-antinuclei annihilation will also be discussed in this contribution. Such information is essential to study the different sources of antinuclei in our Universe and to interpret any future measurement of antinuclei in space.

Speaker: Chiara Pinto (Technische Universitaet Muenchen (DE))

QM23.pdf

11:00 → 13:00 Future Experiments: (1)

Convener: Norbert Herrmann (Ruprecht-Karls-Universitat Heidelberg)

11:00 New opportunities for understanding high-density QCD matter with CMS Phase II detector at the High-Luminosity LHC era

The intriguing phenomena emerging in the high-density quantum chromodynamics (QCD) matter are being widely studied in the heavy ion program at the LHC and will be understood more deeply during the high-luminosity LHC (HL-LHC) era. The CMS experiment is under the Phase II upgrade towards the HL-LHC era. A new timing detector is proposed with its timing resolution for minimum ionization particles (MIP) to be 30 ps. The MIP timing detector (MTD) will also provide the particle identification (PID) ability with a large pseudorapidity acceptance covering up to $|\eta|<3$ through time-of-flight (TOF). Combining MTD with the other new subdetectors, i.e., a tracker with acceptance $|\eta|<4$ and high-granularity calorimeters with acceptance $|\eta|<5$, will enable deeper studies of high-density QCD matters in ultrarelativistic heavy ion collisions. In this presentation, the performances of a broad range of measurements in the future CMS heavy ion programs will be discussed using TOF-PID. These include the (3+1)-dimensional evolution of heavy flavor quarks, QGP medium response to high transverse momentum parton energy loss at wide jet cone angles, collectivity in small systems, fluctuations and transport of initially conserved charges, and light nuclei physics.

Speaker: Zhenyu Ye (University of Illinois at Chicago (US))

yezhenyu_QM2023_v3.pdf

11:20 Novel silicon detectors in ALICE at the LHC: the ITS3 and ALICE 3 upgrades

The ALICE experiment is preparing for the ITS3 upgrade, which is set to take place during the LHC Long Shutdown 3. The aim of this upgrade is to replace the three innermost tracking layers with truly cylindrical wafer-scale Monolithic Active Pixel Sensors (MAPS). By adopting this innovative technology, ALICE will further reduce the material budget and the distance from the interaction point, thus significantly improving its tracking and vertexing capabilities. The R&D program for ITS3 includes several advancements, such as operability of bent MAPS, validation of the 65nm CMOS technology and employment of the stitching process to produce wafer-scale sensors.

In addition to the ITS3 upgrade, ALICE is designing a completely new apparatus, ALICE 3, planned for LHC Run 5 and 6. The detector consists of a large MAPS-based tracking system covering eight units of pseudorapidity, complemented by multiple systems for particle identification, including silicon time-of-flight layers, a ring-imaging Cherenkov detector, a muon identification system, and an electromagnetic calorimeter. The vertex detector will be based on an evolution of the ITS3 concept aiming at a track pointing resolution of better than 10 micron for $p_{\rm T}$>200 MeV/c through the integration of the tracking layers in a retractable structure inside the beam pipe. ALICE 3 will, on the one hand, enable novel studies of the quark-gluon plasma and, on the other hand, open up important physics opportunities in other areas of QCD and beyond.

The presentation will cover both the ITS3 upgrade and the plans for ALICE 3, highlighting the detector concept, the physics performance, and the status of novel sensor R&D. It will showcase the achievements already made and provide an outline of the future plans for advancing the detector technologies.

Speaker: Isabella Sanna (Technische Universitat Munchen (DE))

I_Sanna_QM23.pdf

11:40 ALICE Forward Calorimeter (FoCal): Physics program and performance

The FoCal is a high-granularity forward calorimeter to be installed as an ALICE upgrade subsystem during the LHC Long Shutdown 3 and take data during the LHC Run 4.
It will cover a pseudorapidity interval of $3.4 < \eta < 5.8$, allowing to explore QCD at unprecedented low Bjorken-$x$ of down to $\approx 10^{-6}$ -- a regime where non-linear QCD dynamics are expected to be sizable.
It consists of a compact silicon-tungsten sampling electromagnetic calorimeter (FoCal-E) with pad and pixel longitudinal and transverse segmented readout layers to achieve high spatial resolution for discriminating between isolated photons and decay photon pairs. Its hadronic component (FoCal-H) is constructed from copper capillary tubes filled with scintillator fibers and used for isolation energy measurement and jets.

The FoCal detector extends the ALICE physics program with the capability, unique at the LHC, to investigate gluon Parton Distribution Functions (PDFs) in the low-$x$ regime. This not only enables the study of non-linear QCD effects such as gluon saturation, but also allows to provide experimental constrains for (nuclear) PDFs in a region of phasespace where experimental data is scarce.The detector design allows carrying out these explorations using a multitude of probes, including direct photons, jets, as well as photo-production of vector mesons such as the J/$/psi$ in proton-Pb and Pb-Pb ultra-peripheral collisions.In addition, correlations of different probes can be studied, including gamma-jet, jet--jet and $\pi^0$--$\pi^{0}$ correlations.

In this presentation, we give an overview of the small-x physics program of the FoCal detector, as well as an overview of the expected performance of the detector for various observables. The latter is quantified using recent experimental results of ever-improving prototypes of the detector, which were operated at the Test Beam facilities of CERN in the years 2021--2023.
Furthermore, simulation studies are presented, which showcase the robustness of the detector design and its physics potential.

Speaker: Florian Jonas (Westfaelische Wilhelms-Universitaet Muenster (DE))

2023-09-05-QM_Talk_FoCal_2023.pdf

12:00 The status of the CBM experiment at FAIR

The Compressed Baryonic Matter (CBM) experiment is under construction at the Facility for Antiproton and Ion Research (FAIR). It aims to explore the phase structure of strongly interacting (QCD) matter at large net-baryon densities and moderate temperatures by means of heavy-ion collisions in the energy range sqrt(s_NN) = 2.9 - 4.9 GeV. A fixed-target experiment, CBM is equipped with fast and radiation hard detector systems and an advanced triggerless data acquisition scheme. The CBM will measure at the interaction rates of up to 10 MHz by performing online 4D (space-time) reconstruction and even selection, thus allowing measurements of rare probes not studied so far such as multi-strange hadrons and their antiparticles, double-strange hypernuclei and di-leptons.

This contribution will be an overview of the CBM physics goals among which are the equation-of-state of compressed nuclear matter, the possible phase transition from hadronic to partonic phase, and chiral symmetry restoration. The CBM physics performance in terms of (multi-)strange particle production, dilepton spectroscopy, femtoscopy, and collective phenomena will be discussed. In addition, the status of preparations towards CBM commissioning in 2027, including performance evaluation of the CBM components at FAIR Phase-0 experiments and the latest results of a CBM demonstrator test-setup operating with SIS18 beams (mCBM), will be presented.

Speaker: Claudia Hoehne

CBM_Hoehne_QM23_final.pdf

12:20 Commissioning and first collisions with the LHCb SMOG2 system

Within the recent LHCb upgrade program, notably including the replace-
ment of the whole tracking system and the removal of the hardware trigger
level, the gaseous target SMOG has been improved by the installation of a gas
storage cell upstream of the nominal LHCb interaction point. This is allowing
to increase the injected gas pressure by up to two orders of magnitude for the
same gas flow as Run2 and to also collect data for collisions of LHC beams on
non-noble gases, notably hydrogen. In this contribution, the commissioning of
the system, the first performance from the early analysis of 2022 data and the
physics prospects for Run3 will be presented.

Speaker: Saverio Mariani (CERN)

Mariani_QM_2023-2.pdf

12:40 Overview of the NA60+ experiment at the CERN SPS

NA60+ is a new proposed experiment designed to study the phase diagram of the strongly interacting matter at high baryochemical potential from 200 to 550 MeV at the CERN SPS. It is focused on precision studies of thermal dimuons, heavy quark and strangeness production in Pb--Pb collisions at center of mass energies ranging from 6 to 17 GeV.

The proposed experimental apparatus is composed of a vertex telescope located close to the target and a muon spectrometer located downstream of a hadron absorber. The vertex telescope will consist of several planes of ultra-thin, large area Monolithic Active Pixel sensors (MAPS) embedded in a dipole magnetic field. The muon spectrometer will utilize large area gaseous detectors for muon tracking and a toroidal magnet based on a new light-weight and general-purpose concept.

An ambitious physics program is foreseen, which includes the search for chiral symmetry restoration effects through the $\rho$-$a_{1}$ mixing, the study of the order of the phase transition at large baryochemical potential through the measurement of a caloric curve, the onset of the deconfinement through the measurement of $J/\psi$ suppression. Finally the measurement of the transport properties of the medium via open charm states and the study of hadrochemistry via detection of strange hadrons and hypernuclei is also part of the physics program.
A letter of intent was submitted at the end of 2022 and the goal is to start data taking in 2029.

This talk will focus on the experimental apparatus, including the technical aspects and the R&D status, as well as the physics program and its competitiveness and complementarity to other experiments.

Speaker: Giacomo Alocco (Universita e INFN, Cagliari (IT))

QM2023_NA60+.pdf

11:00 → 13:00 Jets: (4)

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

11:00 Thermalization of mini-jets in QCD kinetic theory

We study the equilibration of a high-momentum parton traveling through a Quark-Gluon Plasma using QCD kinetic theory. We show that the energy and particle number are first transported to the soft sector by collinear cascade and then isotropized by elastic scatterings. For a static thermal background, we find that the jet wake can be described by a thermal distribution function with angle-dependent temperature, i.e., thermalization in momentum happens before isotropization in angle. We also study the kinetic and chemical equilibration of mini-jets in an expanding QGP and determine the time scale for the mini-jet to become part of the non-equilibrium background.

Speaker: Dr Aleksas Mazeliauskas (Heidelberg University (DE))

QM2023_Mazeliauskas_v3.pdf

11:20 Resolving medium properties using high-$p_\mathrm{T}$ jets with jet and in-jet correlations in PbPb collisions at 5.02 TeV with the CMS detector

Even though the quark-gluon plasma produced in high-energy heavy ion collisions has been studied in detail for years, there are still properties that are not known to a good precision. One example of such property is the medium resolution length, which is related to the smallest angle of emission where the medium can still resolve the daughter particles as individual particles. This can be probed for example through the energy-energy correlator. The medium resolution length has implications to parton energy loss, since two particles will emit energy more vigorously compared to one. Also other details of the parton energy loss, like the path-length dependency, could use precision measurements to provide better discriminating power between available theoretical models. Jets are a good observable to experimentally tackle these questions. In this talk, we present recent, high-precision CMS jet measurements in lead-lead collisions at $\sqrt{s_{_{\mathrm{NN}}}} = 5.02$~TeV aimed to explore the properties of the quark-gluon plasma.

Speaker: Jussi Viinikainen (Vanderbilt University (US))

jussi_jetCorrelations_quarkMatter2023.pdf

11:40 Unveiling the Interplay of Multi-Partonic Structures and Strongly-Interacting Media via R-dependent Jet Modifications in Heavy-Ion Collisions (remote)

Jets provide a powerful tool to study the properties of hot nuclear matter and its effect on quantum processes. The degree of modification of jets by the medium depends on how well the medium can resolve the internal jet structure. In this work, we investigate the interplay between the multi-partonic structure of jets and their interaction with a strongly-interacting medium. Specifically, we focus on the R-dependence of the jet $v_2$ coefficients as a function of collision centrality, which provides a unique handle on coherence physics.
Using resummed quenching weights that incorporate both elastic and state-of-the-art radiative energy loss and embedding the system into a realistic heavy-ion environment, we compute the R-dependence of jet suppression at RHIC and the LHC. We observe a very mild R-dependence at RHIC kinematics, similar to what was found at the LHC. Our predictions are in excellent agreement with existing experimental data.
Finally, we present results for the jet azimuthal anisotropy $v_2$ as a function of R, which shows a sequential collapse of $v_2$ for moderate R jets towards the result for small R=0.1 as centrality is decreased. This behavior is due to the strong dependence of the decoherence angle $\theta_c$ on the in-medium traversed length, which affects the size of the resolved phase-space over which quenching weights are resummed. Our results highlight the sensitivity of $v_2(R)$ to the typical value of $\theta_c$ at a given centrality.

Speaker: Dr Yacine Mehtar-Tani (Brookhaven National Laboratory)

QM23-08:2023.pdf

12:00 Measurements of jet momentum profile and generalized angularities in Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV at STAR

Jets are produced in early stages of heavy-ion collisions and undergo modified showering in the quark-gluon plasma (QGP) medium relative to a vacuum case. These modifications can be measured using observables like jet momentum profile and generalized angularities to study the details of jet-medium interactions. Jet momentum profile ($\rho(r)$) encodes radially differential information about jet broadening and has shown migration of charged energy towards the jet-periphery in Pb+Pb collisions at the LHC. Measurements of generalized angularities (girth $g$ and momentum dispersion $p_T^D$) and LeSub (difference between leading and subleading constituents) from Pb+Pb collisions at the LHC show harder, or more quark-like jet fragmentation, in the presence of the medium. Measuring these distributions in heavy-ion collisions at RHIC will help us further characterize the jet-medium interactions in a phase-space region complimentary to that of the LHC.

In this talk, we present the first measurements of fully corrected $\rho(r)$, $g$, $p_T^D$ and LeSub observables using hard-core jets (jets constructed using constituents with $p_T > 2$ GeV/c to suppress the combinatorial background) in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV, collected by the STAR experiment at RHIC. Medium modifications are assessed by calculating nuclear modification factors relative to the $p+p$ baseline. Finally, data are compared with model calculations and the physics implications are discussed.

Speaker: Tanmay Pani

Tanmay_Pani_QM2023_v8.pdf

12:20 Jet-flow coupling in heavy-ion collisions and the jet-induced diffusion wake

Diffusion wake accompanying jet-induced Mach-cone is a unique feature of jet-medium interaction in high-energy heavy-ion collisions. We explore the 3D structure of the diffusion wake induced by triggered jets in Pb+Pb collisions at the LHC energy within the coupled linear Boltzmann transport and hydro model. We identify a valley structure caused by the diffusion wake on top of a ridge from the initial multiple parton interaction (MPI) in jet-hadron correlation as a function of rapidity and azimuthal angle. This leads to a double-peak structure in the rapidity distribution of soft hadrons in the opposite direction of the jets as an unambiguous signal of the diffusion wake. The interaction between the jet and QGP fluid will also deflect partons associated with the jet from their initial direction. Such deflection depends on the energy of the jet constitutes and the velocity of the flow, leading to an angular intra-jet asymmetry of particle distribution inside the jet. We also study the intra-jet asymmetry and its dependence on jet path length and fluid viscosity in both transverse and longitudinal directions. Our methods can be further used to localize the initial production position of the jet without specified requirements of the jet direction.

Speaker: Zhong Yang (CCNU)

QM2023_zy_total_v1.pdf

12:40 Exploring perturbative QCD splittings in heavy-ion collisions

We propose a novel approach to investigate the evolution of jets in heavy-ion collisions by employing a combination of jet substructure measurements. Our method focuses on isolating the perturbative regime of jet evolution. As a proof of concept, we analyze the distribution of the hardest splitting above a transverse momentum scale, $k_{t,cut}$, in high-$p_t$ jets. For a $k_{t, cut}$ that is significantly greater than any medium scale, the observable is determined by vacuum-like emissions. Therefore, it serves as a unique baseline independent of the medium modeling. Furthermore, a moderate $k_{t,cut}$ enhances the sensitivity to energy loss, specifically highlighting the presence of a critical resolution angle. Finally, at low $k_{t,cut}$, the observable becomes sensitive to induced emissions and medium response. We validate the generality of our findings using various heavy-ion event generators, including Hybrid, JetMed, Jewel, and Matter+LBT/MARTINI models. Consequently, these substructure measurements can serve as a valuable guideline for future model developments, effectively disentangling different medium contributions. Our study paves the way for the definition of jet observables that can be calculated from first principles, dominated by perturbative QCD, and within the experimental reach of Run3 at the LHC.

Speaker: Adam Takacs (University of Bergen)

AdamTakacs_QM2023.pdf

11:00 → 13:00 Small Systems: (2)

Convener: Victoria Greene (Vanderbilt University (US))

11:00 Particle production and entropy measurement in ALICE

One of the main goals in the study of hadronic interactions at LHC energies is the attempt to characterize the mechanisms involved in particle production in different regimes. The charged-particle multiplicity is one of the most interesting observables in these kind of studies. On the one hand, the pseudorapidity dependence of charged-particle production provides information on the partonic structure of the colliding hadrons and is sensitive to non-linear QCD evolution in the initial state. Measurements of charged-particle pseudorapidity densities in pp collisions at $\sqrt{s}$ = 13.6 TeV and in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$= 5.36 TeV will be presented, for the first time with the wider pseudorapidity coverage achieved by ALICE in Run 3 thanks to newly installed central and forward trackers. On the other hand to understand the thermal-like behavior and the particle yields in pp collisions, a possible approach is to address the principles of quantum states and their entanglement in the produced system. The entanglement in the initial state has a measurable effect on the evolution of the system and is the driving mechanism behind the thermal-like behavior and particle yields observed. We will show equivalence in a calculation of the initial state entropy (calculated using PDF’s) and the final state entropy (calculated using multiplicity distributions) studying primary charged particles produced in pp collisions at 13 TeV.

Speaker: Alek Hutson (University of Houston (US))

1_Hutson.pdf

11:20 Measurement of charged and full jet production and nuclear modification factor in pp and p−Pb collisions with ALICE

The study of jet production in small collision systems is essential for testing our understanding of perturbative and non perturbative QCD and cold nuclear matter effects. In addition, studies at high multiplicity in small collision systems exhibit signatures of collectivity, which is still not fully understood within a unified picture across system size. Jet quenching in small systems is not observed within current measurement precision, calling for more precise jet measurements.

This talk presents new results of charged and full jet production in pp and p--Pb collisions, and the corresponding nuclear modification factor $R_{\rm pPb}$ at $\sqrt{s_{\rm NN}} = 5.02$, $8$, and 13~TeV. These results are expected to be the most precise measurements of the $R_{\rm pPb}$ by ALICE to date. To investigate whether jet energy is redistributed in cold nuclear matter, the cross-section ratios for different jet resolution parameters ($R$) are compared between pp and p--Pb collisions, as well as within each collision system. Finally, comparisons between data and model predictions are discussed. This result extends to lower jet transverse momentum than previously measured at the LHC, constraining hard parton production and fragmentation mechanisms applied in model calculations, and the impact of the nuclear-modified parton distribution function on jet production. This measurement also provides new constraints on jet quenching in small collision systems.

Speaker: Austin Schmier (University of Tennessee (US))

QM2023_jets_RpA.pdf

11:40 Hot spots in a proton

We explore consequences of the existence of gluonic hot spots inside the proton for the initial eccentricities in a proton-nucleus collision [1], and the constraints on the parameters describing these hot spots from coherent and incoherent exclusive vector meson production cross sections in deep inelastic scattering [2].

The eccentricities are calculated by calculating correlation functions of the energy density field of the glasma immediately after the collision event at proper time t=0+. We separately consider the effects of color charge and geometrical hot spot fluctuations, analytically performing the averages over both in a dilute-dense limit. We show that geometric fluctuations of hot spots inside the proton are the dominant source of eccentricity whereas color charge fluctuations only give a negligible correction. The size and number of hot spots are the most important parameters characterizing the eccentricities.

By employing a nonrelativistic vector meson wave function and working in the dilute limit of the Color Glass Condensate framework we are able to analytically calculate cross sections for vector meson production in our hot spot model. We find that the coherent cross section is sensitive to both the size of the target and the structure of the probe. The incoherent cross section is dominated by color fluctuations at small transverse momentum transfer (t), by proton and hot spot sizes as well as the structure of the probe at medium t and again by color fluctuations at large t. While the t-dependence of the cross section is well reproduced in our model, the relative normalization between the coherent and the incoherent cross sections points to the need for additional fluctuations in the proton.

[1] S. Demirci, T. Lappi and S. Schlichting, "Hot spots and gluon field fluctuations as causes of eccentricity in small systems," Phys. Rev. D 103 (2021) no.9, 094025, [arXiv:2101.03791 [hep-ph]].

[2] S. Demirci, T. Lappi and S. Schlichting, "Proton hot spots and exclusive vector meson production," Phys. Rev. D 106 (2022) no.7, 074025, [arXiv:2206.05207 [hep-ph]].

Speaker: Tuomas Lappi

qm23.pdf

12:00 Search for longe-range QCD collective phenomena inside high-multiplicity jets in pp collisions with the CMS experiment

It has been postulated that nonperturbative quantum chromodynamics (QCD) evolution of a single parton in the vacuum can develop long-range collective effects of a multiparton system, reminiscent of those observed in high-energy nuclear interactions from the formation of a quark-gluon plasma. A search for such QCD collective effects is performed by the CMS experiment via correlation measurements of charged constituents inside jets produced in proton-proton collisions. The data set used at $\sqrt{s} = 13 $~TeV corresponds to the full LHC Run-2 sample, with an integrated luminosity of 138~fb$^{-1}$. For charged constituents within a reconstructed jet of cone radius 0.8, two-particle correlations as functions of relative azimuthal angle ($\Delta\phi*$) and pseudorapidity ($\Delta\eta*$) are performed in a novel ``jet frame'', where constituent kinematics are re-defined relative to the jet direction being the $z$ axis. The correlation functions are studied in classes of in-jet charged multiplicity up to nearly 100 for different ranges of transverse momentum in the jet frame. Anisotropy Fourier harmonics are extracted from long-range azimuthal correlation functions for $\left|\Delta\eta*\right|>2$. The long-range elliptic anisotropy harmonic in data is compared to Monte Carlo event generators without including any long-range collective effects such as PYTHIA8 and Sherpa.

Speaker: Parker Gardner (Rice University (US))

Gardner_Parker_QM.pdf

12:20 Initial-state and final-state effects on hadron production in small collision systems

Heavy meson production in reactions with nuclei is an active new frontier to understand QCD dynamics and the process of hadronization in nuclear matter. Measurements in various colliding systems at RHIC and LHC, including Pb-Pb, Xe-Xe, O-O, p-Pb, and p-O, enable precision tests of the medium-size, temperature, and mass dependencies of the in-medium parton propagation and shower formation. We employ a coupled DGLAP evolution framework that takes advantage of splitting functions recently obtained in soft-collinear effective theory with Glauber gluons (SCET$_{\rm G}$) and hard thermal loop (HTL) motivated collisional energy loss effects. With jet quenching effects constrained to the nuclear modification factor $R_{AA}$ of charged hadrons in Pb-Pb collisions at 5.02~TeV, we present predictions for light and heavy-meson $R_{AA}$ in Xe-Xe, O-O and p-Pb collisions at the LHC. We find that the nuclear modification scales non-trivially with the quark mass and medium properties. In particular, there can be sizeable collision-induced attenuation of heavy mesons in small systems such as oxygen-oxygen and high-multiplicity p-Pb events. Finally, we analyze the impact of different models of initial-state parton dynamics on the search for QGP signatures in small colliding systems.

Speaker: Dr Ivan Vitev

Vitev_QM23_newV3.pdf

12:40 AMY Lorentz invariant parton cascade

The observation of 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 fully exploit
the theory also for phenomenology we introduce ALPACA [2], a Lorentz invariant parton
cascade which is a representation of the AMY effective kinetic theory in the form of
a Monte Carlo event generator. It solves the Boltzmann equation with the full AMY
kernels (elastic scattering and splitting/merging processes) by explicitly simu-
lating the evolution of parton ensembles corresponding to single events. It is
constructed in a fully Lorentz invariant way by using a method pioneered in [3],
which also underlies the parton cascade PCPC [4]. 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 informa-
tion. We perform an extensive validation of the framework in thermal equilibrium
and present first results for out-of-equilibrium simulations for collisions of
light nuclei down to protons. Here we focus on harmonic flow response to initial
geometry deformations and the question to what extent such systems equilibrate.

[1] P. B. Arnold, G. D. Moore and L. G. Yaffe, JHEP 01 (2003), 030 [arXiv:hep-ph/0209353 [hep-ph]]
[2] A. Kurkela, R. Törnkvist and K. Zapp, [arXiv:2211.15454 [hep-ph]]
[3] G. Peter, D. Behrens and C. C. Noack, Phys. Rev. C 49 (1994), 3253-3265
[4] V. Borchers, J. Meyer, S. Gieseke, G. Martens and C. C. Noack, Phys. Rev. C 62 (2000), 064903
[arXiv:hep-ph/0006038 [hep-ph]]

Speaker: Korinna Zapp (Lund University)

qm23.pdf

11:00 → 13:00 Spin/EIC Physics: (1)

Convener: Kenneth Barish (UC Riverside)

11:00 Exploring the Spin Structure of the Nucleon at STAR

Understanding the internal spin structure of the nucleon remains a challenge in strong interaction physics. The unique capability of RHIC to provide both longitudinally and transversely polarized hadronic collisions at various energies opened new avenues in studying the internal structure of the proton with unprecedented depth and precision. Significant progress has been made in the last few years through various measurements at STAR.

The longitudinal spin measurements have contributed significantly to our understanding of the quark and gluon helicity distributions inside the proton. The longitudinal double-spin asymmetry, $A_{LL}$, from STAR inclusive jet and dijet measurements, provides the first evidence of a positive gluon polarization with partonic momentum fraction $x > 0.05$. The reconstruction of $W^{\pm}/Z$ in longitudinally polarized proton-proton collisions indicates that there is a flavor separation of the light sea quark helicity distributions. In transversely polarized proton collisions, $W^{\pm}/Z$-bosons provide the first constraint on the sea-quark Sivers function and contributes to the tests of the predicted sign change. The tilt of the dijet opening angle provides a direct access to the first Mellin momentum of the Sivers function and avoids the spin-correlated fragmentation contributions. The novel measurements of the azimuthal distributions of identified hadrons in jets and spin-dependent dihadron correlations directly probe the collinear quark transversity in the proton, with the former coupled to the transverse momentum dependent (TMD) Collins fragmentation function and the latter to the dihadron interference fragmentation function. These measurements shed lights on Sivers function, quark transversity and spin-dependent fragmentation functions in both collinear and TMD formalism. When combined with data from the future EIC, they will establish the validity and limits of factorization and universality, thus enabling a deeper understanding of fundamental QCD.

In this talk, an overview of recent results on both the longitudinal and transverse spin structure of the proton from STAR will be presented.

Speaker: Ting Lin

QM_Talk_TingLin_20230902.pdf

11:20 Harmonics of Parton Saturation in Lepton-Jet Correlations at the EIC

Parton saturation is one of the most intriguing phenomena in the high energy nuclear physics research frontier, especially in the upcoming era of the Electron-Ion Collider (EIC). The lepton-jet correlation in deep inelastic scattering provides us with a new gateway to the parton saturation at the EIC. In particular, we demonstrate that azimuthal angle anisotropies of the lepton-jet correlation are sensitive to the strength of the saturation momentum in the EIC kinematic region. In contrast to the predictions based on the collinear framework calculation, significant nuclear modification of the anisotropies is observed when we compare the saturation physics results in e + p and e + Au scatterings. By measuring these harmonic coefficients at the EIC, one can conduct quantitative analysis in different collisional systems and unveil compelling evidence for saturation effects.

Speaker: Yuan-Yuan Zhang (CUHK-SZ)

Harmonics_ZYY.pdf

11:40 Probing gluon saturation through two-particle correlations at STAR and the EIC

The gluon distribution function exhibits a rapid increase when the momentum fraction $x$ decreases. However, the total scattering cross section cannot grow beyond a certain limit due to unitarity constraints, which requires the increase of gluon density to be tamped. Gluon recombination under the color glass condensate (CGC) framework provides a possible solution. Therefore, discoveries of nonlinear effects and gluon saturation in QCD will significantly enhance our understanding of nucleon structure and nuclear interactions at high energies, which is a crucial aspect of the Cold QCD program at STAR and the future EIC.

Two-particle azimuthal correlation has been proposed to be one of the most direct and sensitive channels to access the underlying gluon dynamics. In this talk, we will present recent results of forward di-hadron correlations in $p$$+$$p$ and $p$$+$$A$ collisions at STAR, along with model studies for $e$$+$$p$ and $e$$+$$A$ collisions at the EIC. In 2024, STAR is planning to record high statistics $p$$+$$p$ and $p$$+$$Au$ data with the forward upgrade. New opportunities for studying the nonlinear effects in QCD using these new datasets will also be discussed.

Speaker: Xiaoxuan Chu

XChu_QM23.pdf

12:00 Calculation of the Polarized Bethe-Heitler Cross Section for the Electron Ion Collider

Luminosity is an essential quantity to measure the cross section of any process. At the Electron Ion Collider (EIC), it will be measured using the Bethe-Heitler process in which a real photon is radiated in the electron-ion (p or A) scattering: e + p(A) → e + p(A) + Ɣ. The cross section is very large with respect to DIS and can be precisely calculated in leading-order QED, as was done by Bethe and Heitler for unpolarized beams of particles. The EIC will operate with polarized electron and ion beams, thereby requiring a calculation of the spin-dependent modifications to the cross section. A calculation of the polarized Bethe-Heitler cross section is presented.

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

4_Gangadharan.pdf

12:20 Exploration of hadronization through heavy flavor production at the future Electron-Ion Collider

The proposed Electron-Ion Collider (EIC) will utilize high-luminosity high-energy electron+proton ($e+p$) and electron+nucleus ($e+A$) collisions to solve several fundamental questions including searching for gluon saturation and studying the proton/nuclear structure. Due to their high masses ($M_{c,b} > \Lambda_{QCD}$), heavy quarks do not transfer into other quarks or gluons once they are produced. This feature makes the heavy flavor product an ideal probe to explore how a heavy flavor hadron is formed from a heavy flavor quark, which is referred to as the heavy quark hadronization. A series of heavy flavor hadron and jet simulation studies have been carried out with the newly developed EIC project detector conceptual designs. We will present reconstructed heavy flavor hadron mass and heavy flavor jet transverse momentum spectrums, the projected nuclear modifications of heavy flavor hadrons inside jets, and heavy flavor jet substructure distributions in $e+p$ and $e+A$ collisions with the EIC project detector design and the projected integrated luminosities at the EIC. These proposed EIC heavy flavor measurements will provide a unique path to explore the flavor dependent fragmentation functions and reveal the heavy quark nuclear transport properties in cold nuclear medium. The expected results will provide great discriminating power in separating different theoretical calculations and help constraining initial and final state effects for heavy ion measurements at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC).

Speaker: Xuan Li (Los Alamos National Laboratory)

QM2023_EIC_XuanLi_v4.pdf

12:40 STAR Forward Detector Upgrade Status and Performance

An upgrade to the STAR detector system at forward rapidities has been completed before RHIC RUN 2022 and used for data collection. It consists of the Forward Tracking System (FTS) and the Forward Calorimeter System (FCS). The Forward Tracking System is composed of a Silicon Tracker and a small-strip Thin Gap Chamber Tracker. The Forward Calorimeter System contains an Electromagnetic Calorimeter and a Hadronic Calorimeter. The systems cover the pseudorapidity region of 2.5-4, providing detection capabilities for neutral pions, photons, electrons, jets, and charged hadrons. This enables the STAR experiment to study cold QCD physics in very high and low regions of Bjorken $x$ and to explore the longitudinal structure of the initial state in relativistic heavy-ion collisions, such as measuring the decorrelations in a large $\eta$. This talk will introduce the STAR forward upgrade, its current status, and its performance during the STAR Run22.

Speaker: Zhen Wang

Zhen_QM23_FWD_Upgrade_v4.pdf

13:00 → 14:20 Lunch

14:20 → 16:00 Chirality: (2)

Convener: huan huang

14:20 Exact Polarization of Particles of Any Spin at Global Equilibrium

The polarization of the $\Lambda$ particle offers the unique opportunity to study the hydrodynamic gradients in the Quark-Gluon Plasma formed in heavy-ion collisions. However, the theoretical formula commonly used to calculate polarization is only a linear order expansion in thermal vorticity and neglects higher-order terms. Here, we present an exact calculation at all orders in (constant) thermal vorticity at global equilibrium. We resum the series and obtain the analytic form of the spin density matrix and the polarization vector for massive and massless particles of any spin or helicity. Finally, we extend our results to local equilibrium, where we evaluate their impact by numerically calculating polarization in a 3+1 hydrodynamic simulation for different collision systems.

Speaker: Andrea Palermo

AndreaPalermo_QM23.pdf

14:40 Sphaleron damping and effects on normal and anomalous charge transport in high-temperature QCD plasmas

We modify the hydrodynamic equations of a relativistic chiral plasma to account for dissipative effects due to QCD sphaleron transitions. By analyzing the linearized hydrodynamic equations, we show that sphaleron transitions lead to nontrivial effects on vector and axial charge transport phenomena in the presence of a magnetic field. Notably, dissipative effects of sphaleron transitions lead to the emergence of a wavenumber threshold that characterizes the onset of Chiral Magnetic Waves. Sphaleron damping also significantly impacts the time evolution of both vector and axial charge perturbations in the presence of a magnetic field. We further investigate the dependence of charge separation on the rate of sphaleron transitions, which may have implications for the experimental search for the Chiral Magnetic Effect in heavy ion collisions.

Speaker: Lillian de Bruin

LilliandeBruin_QM23Tawk.pdf

15:00 Flow and hyperon polarization at RHIC BES from multi-fluid dynamics

We present a study of flow and hyperon polarization observables at RHIC BES energies in a MUlti Fluid simulation for Fast IoN collisions (MUFFIN) model. MUFFIN is based on a multi-fluid approach to relativistic heavy-ion collisions, and treats the initial stage of heavy-ion reaction as mutual inter-penetration of baryon-rich fluids. It is implemented from scratch with the use of a versatile 3+1 dimensional relativistic viscous hydrodynamic code vHLLE. The model is aimed at describing heavy-ion collision dynamics at lower RHIC BES energies, including the fixed-target mode, and energies of future FAIR facility.
Global angular momentum and directed flow have the same prerequisites, which are baryon stopping and finite impact parameter. Therefore we study them together. We discuss underlying vorticity development in multi-fluid approach, hyperon - anti-hyperon splitting, and compare our results to the recent data for hyperon polarization from HADES experiment at GSI, and a measurement from fixed-target program at RHIC, in addition to previous measurements within RHIC BES program. We examine directed flow observable at different collision energies, and show its equation-of-state dependence and the effects of final-state hadronic cascade, in a full-fledged dynamical model.

Speaker: Dr Iurii Karpenko (FNSPE CTU in Prague)

QM2023-karpenko.pdf

15:20 Impact of globally spin-aligned vector mesons on the search for the chiral magnetic effect in heavy-ion collisions

In high-energy heavy-ion collisions, the chiral magnetic effect (CME) is predicted to arise from the interplay between the chirality imbalance of quarks in the nuclear medium and the intense magnetic field, and will cause a charge separation along the magnetic field direction. While the search for the CME is still ongoing in experiments at Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC), the CME-sensitive observables need to be scrutinized to exclude the non-CME contributions. In this work, we examine the influence of globally spin-aligned $\rho$ mesons on the $\gamma_{112}$ correlator, the $R_{\Psi_2}(\Delta S)$ correlator, and the signed balance functions, via a toy model and a multiphase transport model (AMPT). The global spin alignment of vector mesons could originate from non-CME mechanisms in heavy-ion collisions, and is characterized by the 00-component of the spin density matrix, $\rho_{00}$. We find that the CME observables show similar dependence on $\rho_{00}$, and could receive a positive (negative) contribution from $\rho$-decay pions, if the $\rho_{00}$ of $\rho$ mesons is larger (smaller) than 1/3. Since pions are the most abundant particles in such collisions, the $\rho_{00}$ measurements for $\rho$ mesons become crucial to the interpretation of the CME data.

[1] D.Y. Shen, J.H. Chen, A.H. Tang and G. Wang, Impact of globally spin-aligned vector mesons on the search for the chiral magnetic effect in heavy-ion collisions, Phys. Lett. B 839 (2023) 137777

Speaker: Diyu Shen

QuarkMatter2023_v4.pdf

15:40 Post-blind Analysis of Isobar Collisions and Background-controlled Upper Limit on the Chiral Magnetic Effect from STAR

The STAR Collaboration has reported results from a blind analysis of isobar collisions (${^{96}_{44}\text{Ru}}+{^{96}_{44}\text{Ru}}$, ${^{96}_{40}\text{Zr}}+{^{96}_{40}\text{Zr}}$) at $\sqrt{s_{\mathrm{NN}}}=200$ GeV on the search for the chiral magnetic effect (CME). Significant differences were observed in the measured multiplicity ($N$) and elliptic anisotropy ($v_{2}$) between the two isobar systems [1]. The isobar ratio (Ru/Zr) of CME-sensitive observable, $v_2$-scaled charge separation ($\Delta\gamma/v_2$) is close to but systematically larger than the inverse multiplicity ($1/N$) ratio. This indicates the potential existence of a CME signal, as well as the presence of remaining background that is different between the isobars [2]. In this contribution, we present two post-blind analyses of the isobar data that address the remaining backgrounds and attempt to extract any possible CME signal. One of the analysises applies a weighting procedure such that the two isobar systems have identical distributions of $N$ and $v_{2}$, and then compares the CME-sensitive observables ($\Delta\gamma$ correlator and signed Balance Functions [3]) between two isobars with matched $N$ and $v_{2}$. The other analysis examines the two- and three-particle nonflow contributions to the isobar ratio of $\Delta\gamma / v_{2}$ using real data as well as HIJING simulation. This allows the estimation of a modified background baseline for the $\Delta\gamma/v_2$ ratio. The overall contribution of nonflow is found to be positive, resulting in a background baseline larger than the inverse multiplicity ratio and generally consistent with the isobar measurements. We extract an upper limit of the CME signal in isobar collisions.

[1] M. Abdallah $\textit{et al.}$ (STAR Collaboration), Phys. Rev. C $\textbf{105}$, 014901 (2022)
[2] D.E.Kharzeev, J.Liao and S.~Shi, Phys. Rev. C $\textbf{106}$, L051903 (2022)
[3] S. Choudhury $\textit{et al.}$, Chinese Phys. C $\textbf{46}$ 014101 (2022)

Speaker: Mr Yicheng Feng (Purdue University)

QM2023_IsobarCmeBkg_v16.pdf

14:20 → 16:00 Critical Point: (2)

Convener: Daniel Cebra (University of California, Davis)

14:20 Universal cumulants from fluctuating width of rapidity distributions

In relativistic heavy-ion collisions, the longitudinal fluctuations of the fireball density caused, e.g., by baryon stopping fluctuations result in event-by-event modifications of the proton rapidity density distribution. I will present the multiparticle rapidity correlation functions due to the varying distribution width of the proton rapidity density in central Au+Au collisions at low energies. Then, I will discuss the cumulant ratios in the context of the recent STAR Collaboration results. It is found that the cumulant ratios for small width fluctuations are universal and are of the same order as those measured by the STAR Collaboration. This effect might be important in the search for the predicted QCD critical point.

Speaker: Prof. Adam Bzdak (AGH University of Science and Technology)

qm23_adam_bzdak.pdf

14:40 Fluctuations near the liquid-gas and chiral phase transitions in hadronic matter

In this talk I discuss the fluctuations of the net-baryon number density in dense hadronic matter. Chiral dynamics is modeled via the parity doublet Lagrangian, and the mean-field approximation is employed to account for chiral criticality. I explain the qualitative properties and systematics of the second-order susceptibility of the net-baryon number density for individual positive- and negative-parity nucleons whose masses become degenerate at the chiral restoration. I argue that the second-order susceptibility of the positive-parity state can become negative when the chiral symmetry is restored, as a natural consequence of the unique relationship of the mass to the order parameter and are indicative of approaching the critical point on the chiral phase boundary. The results may have consequences for the interpretation of the experimental data on net-proton fluctuations in heavy-ion collisions.

Talk based on:
M. Marczenko, K. Redlich, C. Sasaki, Phys.Rev.D 107 (2023) 5, 054046

Speaker: Michał Marczenko (University of Wrocław)

QM_talk.pdf

15:00 Effects of first-order chiral phase transition in relativistic heavy-ion collisions

Using a relativistic transport model to describe the evolution of the quantum chromodynamic matter produced in Au+Au collisions at $\sqrt{s_{NN}}=3-200$ GeV, we study the effect of a first-order phase transition in the equation of state of this matter on the yield ratio $N_tN_p/ N_d^2$ ($tp/d^2$) of produced proton ($p$), deuteron ($d$), and triton ($t$). We find that the large density inhomogeneities generated by the spinodal instability during the first-order phase transition can survive the fast expansion of the subsequent hadronic matter and lead to enhanced $tp/d^2$ in central collisions at $\sqrt{s_{NN}}=3-5$~GeV as seen in the experiments by the STAR Collaboration and the E864 Collaboration. However, this enhancement subsides with increasing collision centrality, and the resulting almost flat centrality dependence of $tp/d^2$ at $\sqrt{s_{NN}}=3$ GeV can also be used as a signal for the first-order phase transition.

Speaker: Dr KaiJia Sun (Institute of Modern Physics, Fudan University, Shanghai, China)

QM2023_KaiJia Sun_v1.pdf

15:20 Exploring the Critical Points in QCD with Multi-Point Pade and Machine Learning Techniques in (2+1)-flavor QCD

Our ability to predict thermodynamic observables and determine the QCD critical point at real values of chemical potentials is severely limited by the infamous sign problem. To address this issue, there are two common approaches: expanding the QCD partition function in a Taylor series with respect to the charge chemical potentials ($\mu_{B,Q,S}$) or analytically continuing from imaginary chemical potentials. However, both methods have limitations, particularly for larger values of the baryon chemical potential. Recently, we proposed a multi-point Pade approach[1] based on a (2+1)-flavor Lattice QCD simulation that uses multiple imaginary chemical potentials with temporal extents of $N_{\tau}=4,6,8$. This method combines the benefits of the aforementioned approaches and is expected to provide more reliable quantitative predictions for small to intermediate values of the baryon chemical potential. Another, advantage we can use this method to estimate different critical points of QCD by examining the singularities of the Pade series.

In this presentation, we will focus on two critical points, well known Roberge-Weiss critical point, which arises when the baryon chemical potential is purely imaginary, and the QCD critical point, which will emerge at a real value of the baryon chemical potential. We use the multi-point Pade approach to locate the Lee-Yang edge singularities in the complex chemical potential plane, which are obtained from lattice QCD simulated data. Our results demonstrate that the scaling of these singularities corresponds to the expected scaling of the well-known Roberge-Weiss transition. The universal scaling of singularities in the vicinity of the QCD critical endpoint is also investigated. Lee-Yang edge singularities associated with the QCD critical point at the real chemical potential for various temperatures are calculated. As the temperature decreases, the imaginary part of the singularities becomes smaller, hinting at a possible existence of a critical point at low temperatures. A machine learning technique is used to model the probability density of the singularities and interpolate the real and imaginary parts of the singularities between different temperatures. By employing a suitable scaling ansatz, the singularities are extrapolated towards the real axis, and the possible location of the QCD critical point is estimated. Preliminary results of ($T_{CEP},\mu_B^{CEP}$) are consistent with model predictions and other lattice QCD calculations.
[1] P. Dimopoulos et al., Contribution to understanding the phase structure of strong interaction matter: Lee-Yang edge singularities from lattice QCD, Phys. Rev. D 105 (2022) 034513 [2110.15933]

Speaker: Jishnu Goswami (Bielefeld University)

Qmjishnu2023.pdf

15:40 Extracting the speed of sound in the strongly-interacting matter created in relativistic nuclear collisions with the CMS experiment

A hot and dense matter exhibiting collective flow behavior with almost no viscous dissipation has been discovered in ultrarelativistic nuclear collisions. To constrain the fundamental degrees of freedom and equation of state of this matter, this talk will present an extraction of its speed of sound using head-on lead-lead collision data collected by the CMS experiment at a center-of-mass energy per nucleon pair of 5.02 TeV. The measurement is based on an analysis of the observed charged multiplicity dependence of the average particle transverse momentum in ultracentral events (impact parameter of nearly zero), a variable which probes the system temperature as a function of entropy density at a fixed volume. Results are compared with hydrodynamic simulations and lattice QCD predictions of the equation of state at high temperatures and small chemical potential. Implications to search for QCD phase transition and the critical point are discussed.

Speaker: Cesar Bernardes (UNESP - Universidade Estadual Paulista (BR))

slides_speedOfSound_CMS_CesarABernardes_QM23.pdf

14:20 → 16:00 EM Probes: (2)

Convener: Raimond Snellings (Nikhef National institute for subatomic physics (NL))

14:20 Fate of the $\rho$ - $a_1$ mixing in dilepton production

In-medium modifications of vector spectral functions are anticipated to carry imprints of restoration of chiral symmetry at high temperature/baryon density. Strong modifications have been indeed measured via dimuon production at the CERN SPS, whereas it remains inconclusive how to quantify those changes as the direct consequence of chiral symmetry restoration. Given the difficulty that it is elusive to construct the axial-vector spectrum in heavy-ion experiments, the key phenomenon is that the vector meson mixes with the axial-vector meson in a medium via pion loops, known as chiral mixing. The chiral mixing effect can be quantified as a model-independent theorem at low temperature [1], whereas at the critical temperature the chiral symmetry restoration compels the vanishing chiral-mixing [2]. On-going experiments and recent development of hydrodynamic model bring us a unique opportunity to get insight into chiral symmetry restoration from investigation of the dilepton invariant mass spectra.
In this work, a case study is carried out by utilizing the following 3 scenarios: (A) chiral restoration absent, (B) chiral restoration present and (C) false chiral restoration. The scenario-B describes the in-medium spectral function of the rho meson from zero to the chiral crossover temperature [2]. The scenario-C is often argued to generate an increase of the dilepton yield, which is incorrect since the procedure does not capture the change of QCD ground state.
We combine the in-medium spectral function in the chiral effective field theory with state-of-the-art fluid dynamical simulations with temperature-dependent shear and bulk viscosities [3]. We find an increase of the yield at 1.2-1.4 GeV due to the degenerate $\rho$ and $a_1$ mesons, whereas the scenario of false restoration leads to a substantial overestimate at 1.2 GeV and this also causes an underestimate below and above the $\rho$ peak.

[1] M. Dey, V. L. Eletsky, and B. L. Ioffe, Phys. Lett. B 252, 620 (1990).
[2] M. Harada, C. Sasaki, and W. Weise, Phys. Rev. D 78, 114003 (2008).
[3] K. Okamoto and C. Nonaka, Phys. Rev. C 98, no.5, 054906 (2018); H. Fujii, K. Itakura, K. Miyachi and C. Nonaka, Phys. Rev. C 106, no.3, 034906 (2022).

Speaker: Azumi Sakai

QuarkMatter2023_slides_Sakai_v4.pdf

14:40 Pre-equilibrium Photon and Dilepton Production

We use QCD kinetic theory to compute photon and dilepton production in the chemically equilibrating out-of-equilibrium Quark-Gluon Plasma created in the early stages of high-energy heavy-ion collisions. We compare the non-equilibrium rates to the production in a thermal QGP and extract the dependence of pre-equilibrium photon and dilepton production on the kinetic and chemical equilibration time. By including realistic photon and dilepton production from the pre-equilibrium phase into state-of-the art calculations of the production during the later stages, we establish the significance of the pre-equilibrium phase  for the production  of electromagnetic probes  in heavy-ion collisions.

Speaker: Philip Plaschke (Bielefeld University)

QM23_Plaschke.pdf

15:00 Electromagnetic probes for critical fluctuations of phase transitions in dense QCD

We calculate how the critical fluctuations of the QCD critical point (CP) and the color superconducting (CSC) phase transition affect the dilepton production rate (DPR) and the associated transport coefficients, the electric conductivity and relaxation time. We examine the modification of the photon self-energy by the so-called Aslamazov-Larkin, Maki-Thompson, and Density of States terms on the basis of the two-flavor NJL model. In this presentation, it is shown that the DPR is significantly enhanced in the low invariant mass region around the QCD CP and CSC phase transition, which can be promising observables to reveal the existence of the respective phase transitions by heavy-ion collision experiments. In addition, we show that electric conductivity and relaxation time are divergent at the respective critical temperatures with different exponents and the physical origin of the difference is clarified in terms of the characteristics of the respective fluctuations.

Speaker: Toru Nishimura

QM2023_Nishimura.pdf

15:20 Inverse slope of the photon $p_T$ spectrum and the QGP temperature profile

Thermal photon emission from the QGP is visible in the $p_T$ spectrum of direct photons measured in heavy-ion collisions, producing a characteristic exponential dependence of the spectrum at low $p_T$. The ALICE, PHENIX and STAR Collaboration have quantified this inverse slope $T_{eff}$, measuring $\approx 200$-$400$ MeV, close to the range of QGP temperatures seen in hydrodynamic simulations of the plasma.

I will first present a simplified model of heavy-ion collisions in which a well-defined temperature profile of the plasma can be related to the inverse slope of the photon spectrum, providing a connection between the spectrum's inverse slope $T_{eff}$, the QGP's size and maximum temperature, as well as the range of $p_T$ used to determine $T_{eff}$ from the photon spectrum. I will compare these results with existing and new numerical simulations, discussing the role of the plasma's transverse expansion on $T_{eff}$, distinguishing between the initial transverse flow and the radial flow developed from the plasma's expansion.

Speaker: Jean-Francois Paquet (Vanderbilt University)

jfpaquet_qm2023_houston.pdf

15:40 Understanding the properties of the fireball with the polarization signature of thermal dileptons

As dileptons are radiated from the extreme states of matter created in heavy-ion collisions with negligible final-state interactions, they retain the information imprinted on them at the time of their creation. Multi-differential measurements of dilepton invariant mass, momentum, and angular distributions can therefore serve as a unique tool to characterize the properties of matter in the interior of the hot and dense fireball.

An important property of virtual photons is their spin polarization defined in the rest frame of the virtual photon with respect to a chosen quantization axis. Even an isotropic thermal medium can exhibit nontrivial anisotropies in the angular distributions of the produced lepton pairs. While the total yield and observable spectra are proportional to the sum of the longitudinal and transverse components of the spectral function, the polarization depends on their difference. As the processes that drive the medium effects in the spectral function change with invariant mass and momentum, this becomes a powerful tool to study the composition and degrees of freedom of the hot and dense medium.

In this contribution, we utilize a coarse-grained hadronic transport approach to model the space-time evolution of the fireball. We calculate the polarization observables of thermal virtual photons as a function of mass and momentum and compare the results to existing measurements from HADES and NA60. Finally, we discuss the prospects of using an excitation function of virtual photon polarization to disentangle the contributions to the thermal dilepton radiation of hadronic and partonic origin.

Speaker: Florian Seck

fseck_qm23.pdf

14:20 → 16:00 Initial State: (2)

Convener: Sangyong Jeon

14:20 Determination of the neutron skin of Pb-208 from ultrarelativistic nuclear collisions

In heavy nuclei the neutron distribution has a larger spatial extent than the proton distribution. This size difference represents the so-called neutron skin and is determined by the strong nuclear force in the same regime as that determining the masses and radii of neutron stars. The neutron skin of $^{208}$Pb, owing to its simple structure and large neutron excess, has been the target of many dedicated efforts. We present a state-of-the-art global analysis to fit a hydrodynamic model to soft sector measurements of ultrarelativistic $^{208}$Pb+$^{208}$Pb collisions performed at the LHC to achieve the first determination of the neutron skin of $^{208}$Pb in scattering processes mediated by gluons at high energy. Thanks to the high sensitivity of high-energy observables such as the total hadronic cross sections and elliptic flow to the overall size of the colliding $^{208}$Pb ions, we achieve an accurate determination of the skin: $\Delta r_{np}=0.217\pm0.058$ fm. This is consistent with state-of-the-art nuclear theory predictions, and competitive in precision with a recent extraction from polarized electron scattering by the PREX collaboration at JLab.

Speaker: Govert Nijs (Massachusetts Institute of Technology)

GovertNijsQM2023.pdf

14:40 Search for evidence of the baryon junction in photonuclear processes and heavy-ion collisions at STAR

Baryon number is a strictly conserved quantity in QCD and is conventionally assumed to be divided equally among the three valence quarks in baryonic matter. An alternative model is the baryon junction: a Y-shaped configuration of nonperturbative gluons that is connected to all three valence quarks and carries the baryon number. Neither of these theories has been experimentally verified. Because valence quarks carry the baryon's electric charge, we can test if they also carry the baryon number by comparing baryon stopping to charge stopping. This is done to high precision using the STAR isobar dataset of ${}^{96}_{44}\rm{Ru} + {}^{96}_{44}\rm{Ru}$ and ${}^{96}_{40}\rm{Zr} + {}^{96}_{40}\rm{Zr}$ collisions at $\sqrt{s_{NN}} = 200~\rm{GeV}$. Results show that at mid-rapidity the ratio of the net-baryon yield, $B$, to the difference in net-charge yield, $\Delta Q = Q(\rm{Ru}) - \textit{Q}(\rm{Zr})$, is roughly twice as large in central collisions as would be expected if the valence quarks carry the baryon number. Another observable that is sensitive to the carrier of the baryon number is the net-proton yield in semi-inclusive photonuclear collisions, a type of ultraperipheral heavy-ion collision where one nucleus emits a quasi-real photon interacting with the other colliding nucleus. We observe significant baryon stopping at low transverse momentum in photonuclear processes using $\rm{Au}+\rm{Au}$ collisions at $\sqrt{s_{NN}} = 54.4~\rm{GeV}$. Our combined results in isobar collisions and photonuclear processes indicate deviations from the picture of valence quarks as the baryon carrier and favor the baryon junction hypothesis.

Speaker: Chun Yuen Tsang (Kent State University)

QM_2023_v12.pdf

15:00 Measurement of dijet production in UPC with the ATLAS detector

In relativistic heavy ion collisions, the charged ions produce an intense flux of equivalent photons. Thus, photon-induced processes are the dominant interaction mechanism when the colliding nuclei have a transverse separation larger than the nuclear diameter. In these ultra-peripheral collisions (UPCs), the photon provides a clean, energetic probe of the partonic structure of the nucleus, analogous to deep inelastic scattering. This talk presents a measurement of jet production in UPCs performed with the ATLAS detector using high-statistics 2018 Pb+Pb data. Events are selected using requirements on jet production, rapidity gaps, and forward neutron emission to identify photo-nuclear hard-scattering processes. The precision of these measurements is augmented by studies of nuclear break-up effects, allowing for detailed comparisons with theoretical models in phase-space regions where significant nuclear PDF modifications are expected but not strongly constrained by existing data.

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

QM23_Talk_Gilbert.pdf

15:20 Thermalization and quark production in spatially homogeneous system of gluons

We first assemble a full set of the Boltzmann Equation in Diffusion Approximation (BEDA) for studying thermalization/hydrodynamization and quark production in out of equilibrium systems. In the BEDA, the time evolution of a generic system is characterized by four space-time dependent quantities: the jet quenching parameter $\hat q​​​​$, the effective temperature $T_*$ and two others that describe the conversion between gluons and quarks/antiquarks. Out of the latter two quantities, an effective baryon (net quark) chemical potential is defined, which equals the baryon chemical potential after thermal equilibration. We then study thermalization and the production of three flavors of massless quarks in spatially homogeneous systems initially filled only with gluons. A complete parametric understanding for thermalization and quark production is obtained for both initially very dense or dilute systems, which are confirmed by detailed numerical simulations. For initial distributions more relevant for heavy-ion collisions, the complete thermal equilibration is found to be significantly delayed by considering quark production due to Pauli blocking. The implications of such an observation for heavy-ion phenomenology will also be discussed.

Speaker: Sergio Barrera Cabodevila (Instituto Galego de Física de Altas Enerxías (IGFAE))

QM2023_BarreraCabodevila.pdf

15:40 Multi-scale Imaging of Nuclear and Proton Geometries

Determining the structure of protons and nuclei at high energy is one of central goals of the heavy-ion collisions and the future Electron-Ion Collider (EIC). We first use Bayesian inference within the color glass condensate framework to extract the proton shape fluctuations from HERA exclusive vector meson production data at $x = 10^{-3}$. With this input, we employ the JIMWLK evolution for the proton and nucleus geometry from HERA to LHC energies. We then do the hydrodynamic simulations to quantify the various hydrodynamic observables obtained using this setup with evolved geometry parameters with full JIMWLK evolution. We find the multiplicity distributions and $v_n-p_T$ correlations are sensitive to the JIMWLK evolution. These help us to understand the energy evolution of nuclear geometry in the future.
For electron+nucleus collisions, we find out that the nuclear geometric deformations and fluctuations affect diffractive vector meson productions, and that multi-pole deformations at different length scales manifest themselves at different regions of transverse momentum transfer. Further more, the JIMWLK evolution doesn’t wash out this effects. We systematically study the deformations effects of Uranium (U), Gold (Au), Oxygen-16 ($^{16}O$), and Neon ($^{20}Ne$) on the diffractive $J/\Psi$ productions. Our work demonstrate that the future EIC diffractive data can provide direct information on the nuclear structure at small $x$ and the complementary constraints for the nuclear geometric shape for the traditional hydrodynamic simulations in heavy-ion collisions.

Speaker: Wenbin Zhao (Wayne State University)

Wenbin_Zhao_QM2023.pdf

14:20 → 16:00 QCD at finite T and density: (2)

Convener: Szabolcs Istvan Borsanyi

14:20 Finite volume effects near the chiral crossover

The effect of a finite volume presents itself both in heavy ion
experiments as well as in recent model calculations. The magnitude is
sensitive to the proximity of a nearby critical point.
We calculate the finite volume effects at finite temperature in continuum
QCD using lattice simulations. We focus on the vicinity of the chiral
crossover.
We investigate the impact of finite volumes on the chiral order parameter
and fluctuations of conserved charges.

Speaker: Ruben Kara

Kara_QM23.pdf

14:40 QCD material parameters at zero and non-zero chemical potential from the lattice

Using an eighth-order Taylor expansion in baryon chemical potential, we recently obtained the (2+1)-flavor QCD equation of state (EoS) at non-zero conserved charge chemical potentials from the lattice. We focused on strangeness-neutral, isospin-symmetric QCD matter, which closely resembles the situation encountered in heavy-ion collision experiments. Using this EoS, we present here results on various QCD material parameters along lines of constant entropy per baryon number $s/n_B$. In particular we compute the specific heat, speed of sound, compressibility, and the thermal expansion coefficient along lines of constant $s/n_B$. We also present results at zero chemical potential for the isothermal speed of sound and isothermal compressibility. We show that in the vicinity of the crossover temperature, the speed of sound at fixed $s/n_B$ has a well localized minimum or "soft point" at large $s/n_B$, which appears to vanish as $s/n_B$ decreases. We show that this is consistent with hadron resonance gas model calculations at low temperature and reflects the increasing importance of the baryon sector at low temperature. A similar behavior is found for the isothermal speed of sound, which decreases monotonically at low temperature for all $s/n_B$. Furthermore, we show that in the entire range of $s/n_B$ relevant for the beam energy scan at RHIC, the specific heat, compressibility, and thermal expansion coefficient show no indication for an approach to critical behavior that one would expect close to a possibly existing critical endpoint.

Speaker: David Clarke

CLARKE@QM2023.pdf

15:00 Influence of baryon number, strangeness, and electric charge fluctuations on spectra and collective flow at the LHC

At LHC energies it is possible to generate BSQ (baryon, strangeness, and electric) charge density fluctuations from gluon splittings into quark anti-quark pairs, generated within the ICCING model. This creates an opportunity to implement and quantify the BSQ charge dynamics in the very well controlled regime of heavy ion collisions simulations. In this work, we implement BSQ charge dynamics in a fully integrated framework. We propagate these conserved charges within an upgraded version of the hydrodynamic model, v-USPhydro, that conserves the BSQ charge densities exactly. Our hydrodynamics simulation is informed by the full 4-D equation of state {T,μB,μS,μQ} from Lattice Quantum Chromodynamics and includes decays from the latest Particle Data Group 2016+. We find that we are able to reproduce both spectra and flow in our approach while also obtaining relatively large fluctuations in the chemical potentials {T,μB,μS,μQ} in local fluid cells at the freeze-out hypersurface even at LHC energies. We discuss possible new experimental observables which will be sensitive to these fluctuations of conserved charges.

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

QM2023_Almaalol_v2 (1).pdf

QM2023_Almaalol_v2 (1).pptx

15:20 Interferometry in a Moat Regime

The QCD phase diagram at large chemical potential is largely uncharted territory. Based on model studies, there are various phases that could occur in this regime. Among them are phases related to spatial modulations, such as inhomogeneous/crystalline phases, liquid crystals or a quantum pion liquid. A common feature of all these phases is that particles can have a moat dispersion, where the energy is minimized at nonzero momentum. This can directly affect particle production in heavy-ion collisions and leads to characteristic signatures in particle correlations. I will discuss the underlying physics and present a formalism to study particle spectra on general hypersurfaces in a medium. Using this formalism, I will show that the correlations generated by the Hanbury-Brown–Twiss effect are promising probes for a moat regime in heavy-ion collisions.

Speaker: Fabian Rennecke

QM2023_Rennecke.pdf

15:40 Global angular momentum generation in heavy-ion reactions within a hadronic transport approach

In 2017, the STAR collaboration at the Relativistic Heavy Ion Collider (RHIC) has measured finite global angular momentum in heavy-ion collisions through a spin polarization measurement of $\Lambda$ hyperons. This measurement revealed a high angular momentum of the heavy ions and provided experimental evidence for vorticity in the quark-gluon plasma (QGP) for the first time. In order to investigate the underlying mechanisms, a dynamic description of the transfer of angular momentum is required. In this work, the microscopic non-equilibrium transport approach SMASH (Simulating Many Accelerated Strongly-interacting Hadrons) is applied to study the generation of global angular momentum by the interaction of two nuclei. As SMASH provides access to the whole phase-space evolution of every particle at any given time, it allows to assess the fraction of angular momentum generated in the fireball by all participants. We confirm the previous modeling by Becattini \textit{et al} within a geometric Glauber model approach, which found that the angular momentum transfer reaches a unique maximum in mid-central collisions during time evolution [arXiv:2212.14385v1]. The corresponding impact parameter is around $b=4-6$ fm for all beam energies from $\sqrt{s_{\rm NN}}=2.41-200$ GeV.
Even though angular momentum is not conserved locally in the transport approach a priori, we identify the contributions to the conservation violation and propose optimal setups for different energy regimes that recover conservation, based upon the test particle method and the treatment of Fermi motion. Furthermore, the system size and centrality dependence are investigated.

Speaker: Nils Sass

Angular_Momentum.pdf

16:00 → 16:30 Coffee Break

16:30 → 18:10 Heavy Flavor: (4)

Convener: Elena Gonzalez Ferreiro

16:30 Measurements of prompt and nonprompt $\mathrm{D}^{0}$ mesons production and collective flow with CMS at 5.02 TeV

The interaction of heavy quarks with the quark-gluon plasma (QGP) affects their azimuthal distribution and transverse momentum ($p_\mathrm{T}$) spectrum, hence azimuthal anisotropy coefficients ($v_{n}$) and nuclear modification factors ($R_\mathrm{AA}$) of heavy flavor hadrons are important probes of the QGP. However, a simultaneous modeling of $v_{n}$ and $R_\mathrm{AA}$ is still challenging. This talk reports the first nonprompt $\mathrm{D}^{0}$ measurements of the azimuthal anisotropy elliptic ($v_{2}$) and triangular ($v_{3}$) coefficients in large systems, using lead-lead (PbPb) collisions at $\sqrt{s_{_{\mathrm{NN}}}} = 5.02$~TeV, collected with the CMS apparatus. The measurements are performed as a function of transverse momentum, spanning 1--30 GeV/c, in three centrality classes, from central to midcentral collisions. Compared to the prompt $\mathrm{D}^{0}$ results, the nonprompt $\mathrm{D}^{0}$ $v_{2}$ flow coefficients are systematically lower and show less dependence on particle $p_\mathrm{T}$ and centrality. An indication of nonzero $v_{3}$ coefficient of the nonprompt $\mathrm{D}^{0}$ is observed. The wide $p_\mathrm{T}$ range enables the study of various flow generation mechanisms, like diffusion at low $p_\mathrm{T}$ and path-dependent parton energy loss at low and high $p_\mathrm{T}$, respectively. In addition, measurements of both prompt and nonprompt $\mathrm{D}^{0}$ mesons cross sections in PbPb and proton-proton collisions, as well as $R_\mathrm{AA}$, will be shown. The results will be compared to theoretical predictions.

Speaker: Milan Stojanovic (Purdue University (US))

MilanStojanovic_D0_CMS_QM2023.pdf

16:50 Heavy-flavor jet substructure for probing the flavour dependences of QCD parton showers with ALICE

Properties of partonic fragmentation in QCD depend on parton flavours in $1\rightarrow2$ splitting processes in parton showers due to the different Casimir factors of quarks and gluons, and to the different masses of light- and heavy-flavour quarks. Heavy-flavour jets provide a unique experimental tool to probe these flavour dependencies, particularly at low and intermediate transverse momenta where mass effects are significant. The ALICE detector has excellent particle tracking and PID performance to tag jets with reconstructed heavy-flavour hadrons. These capabilities are essential for jet substructure studies as they remove significant contamination from heavy-flavour hadron decay products and allows us to trace the quark flavour through the splitting tree. We report a series of heavy-flavour jet substructure measurements tagged with a reconstructed $\rm{D}^{0}$ meson. These include first measurements of the jet axes differences between different recombination and grooming schemes and the jet angularities where the angular exponent can tune the sensitivity to mass and Casimir effects. Additionally, the groomed momentum fraction and opening angle of the first splitting are reported, which link to fundamental ingredients of the splitting functions. Comparisons with flavour-untagged jets probe flavour dependencies from the charm quark mass and the high purity quark nature of the $\rm{D}^{0}$-tagged jet sample. Further comparisons to different MC generators will assess the role of these flavour dependencies in other parton shower prescriptions.

Speaker: Nima Zardoshti (CERN)

QuarkMatter_2023_Nima_Zardoshti.pdf

17:10 Studies of the relative suppression of excited quarkonium states in pPb collisions with CMS

One of the most unexpected findings of the LHC heavy ion program is the observation of stronger suppressions of the excited quarkonium states compared to the ground states in proton-lead (pPb) collisions. Such differences imply dissociation effects occurring at late stages, after the evolution of heavy quark pairs into well-defined physical states. The variety of binding energies within the charmonium and bottomonium families offers an experimental tool to characterize the phenomena at play. Moreover, measuring the excited states is crucial as they represent significant feed-down contributions to the production of the ground states in proton-proton collisions and must be accounted for in the interpretation of proton-nucleus data. We report studies of the relative suppression of quarkonia in pPb collisions performed in CMS. Nuclear modification factors as well as excited-to-ground state cross section ratios are measured as a function of particle transverse momentum and rapidity, and event activity (number of reconstructed tracks). The results are compared with several model calculations incorporating initial- and final-state effects.

Speaker: Ota Kukral (University of California Davis (US))

Kukral_Ota_QM_2023.pdf

17:30 T-matrix Analysis of Static Wilson Line Correlators from Lattice QCD at Finite Temperature

We utilize a previously constructed thermodynamic T-matrix approach to the quark-gluon plasma (QGP) to calculate Wilson line correlator of a static quark antiquark pair and apply them to the results from realistic 2+1-flavor lattice-QCD (lQCD) computations. Earlier reconstructions of static quarkonium spectral functions from lQCD data have indicated an absence of screening of the heavy-quark (HQ) potential in the QGP, while previous T-matrix applications to the HQ free energies favor screening effects in combination with HQ mass shifts induced by in-medium selfenergies. The pertinent T-matrix results can semi-quantitatively describe the lQCD data for Wilson line correlators but refinements of the input parameters are necessary to improve the agreement, providing new insights. This renders the T-matrix a more accurate and reliable tool to make predictions for the spectral and transport properties of the QGP.

Speaker: Zhanduo Tang

QM2023_Tang.pdf

17:50 Quarkonium transport in weakly and strongly coupled plasmas

Suppression of open heavy flavors and quarkonia in heavy-ion collisions is among the most informative probes of the quark-gluon plasma (QGP). 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. Only in the past few years, systematic theoretical studies of quarkonium time evolution in the QGP have been carried out in the regime where the temperature of the QGP is much smaller than the inverse of quarkonium size.

Such calculations require the evaluation of a gauge-invariant correlator of chromoelectric fields dressed with Wilson lines, which is similar to, but different from, the correlation used to define the well-known [1] heavy quark diffusion coefficient. In this talk, we will describe its calculation at weak coupling in QCD up to next-to-leading order [2] and at strong coupling in N=4 Yang-Mills theory using the AdS/CFT correspondence [3]. While it resembles the open heavy quark case, it has some crucial differences that highlight the relevance of quantum color correlations. Crucial insights are obtained by studying them in temporal axial gauge, where these correlators would naively be equal [4]. Furthermore, we will discuss the necessary setup to evaluate the quarkonium transport coefficients from lattice QCD, which, at present, is the only tool we have to study QCD in the non-perturbative regime. Finally, we will discuss the phenomenological implications that can be extracted from this correlator, with emphasis on the implications of the novel N=4 SYM results at strong coupling.

---

[1] Casalderrey-Solana, Teaney, arXiv:hep-ph/0605199
[2] Binder, Mukaida, Scheihing-Hitschfeld, Yao, arXiv:2107.03945
[3] Nijs, Scheihing-Hitschfeld, Yao, arXiv:2304.03298
[4] Scheihing-Hitschfeld, Yao, arXiv:2205.04477

Speaker: Bruno Sebastian Scheihing Hitschfeld (Massachusetts Institute of Technology)

QMTalk-Scheihing.pdf

16:30 → 18:10 Initial State: (3)

Convener: Yen-Jie Lee (Massachusetts Inst. of Technology (US))

16:30 Event-by-event pre-equilibrium dynamics with conserved charges

We use QCD effective kinetic theory to calculate far-from-equilibrium dynamics in the presence of quarks on an event-by-event basis within the KoMPoST framework. We present non-equilibrium response functions and dynamical evolution pertinent to the early time dynamics of heavy-ion collisions at the highest energies. The KoMPoST framework with conserved baryon, strangeness, and electric charges can then be readily implemented into a multistage model allowing for the initialization of a non-equilibrium charge current in hydrodynamic simulations. In the precision era of high energy heavy-ion collisions, it is imperative for models to capture first principles physics as faithfully as possible. The work presented here opens the door for new charge related observables which can further our understanding of the plasma produced in heavy-ion collisions, from a first principles perspective.

Speaker: Dr Travis Dore (Universität Bielefeld)

QM23_travis_dore.pdf

16:50 Assessing the deformed nuclear structure at various energy scales

Many atomic nuclei have a deformed intrinsic shape that affects the initial-state geometry of the related collider experiments, and hence the flow coefficients observed in the final states. We use collisions of deformed nuclei to study the connection between nuclear structure at low energy and the effective theory of high energy QCD. Along with 16O, the clustered and deformed structure of 20Ne is studied across different collision energies via JIMWLK evolution equations to search for QCD-induced modifications to the nuclear geometry and their observable signatures. Our range of $\sqrt{s_{\rm NN}}$ varies from top LHC energy at $7$ TeV, down 70 GeV, corresponding to the center-of-mass energy available in fixed-target experiments performed in the SMOG system of the LHCb detector. In addition, we discuss ratios of observables in isobar collisions involving $\rm{Ru}^{96}$ and $\rm{Zr}^{96}$, which differs from unity because of the structural difference of these isotopes, and examine their energy evolution from RHIC to LHC.

Speaker: Pragya Singh

PSingh_QM2023.pdf

17:10 Exploring electromagnetic field effects and constraining transport parameters of QGP using STAR BES II data

Constraining the initial strong electromagnetic field effects, three-dimensional structure of the initial state, and the transport properties of the Quark-Gluon Plasma (QGP) at different temperatures ($T$), and baryon chemical potentials ($\mu_B$) are critical objectives of the heavy-ion program at RHIC. The dominance of Faraday+Coulomb effect during the initial stages of non-central heavy ion collisions is predicted to result in a negative $\Delta v_1$, defined by the difference in rapidity-odd directed flow ($v_1$) between positively and negatively charged particles. With the large dataset accumulated in the Beam Energy Scan (BES) phase II of STAR, we probe the beam energy dependence of $\Delta v_{1}$ for charged pions, kaons, and protons as a function of rapidity, transverse momentum ($p_T$), and centrality at midrapidity in Au+Au collisions at $\sqrt{s_{NN}}$ = 19.6 - 7.7 GeV. Our results support the notion of stronger $\Delta v_{1}$ at lower collision energies, expected due to the longer lifetime of the electromagnetic field and shorter lifetime of the fireball and a stronger effect with increasing $p_T$.

The flow angular decorrelations ($r_n(\eta)$) are sensitive to the 3D initial state, and new observables such as the transverse momentum correlator $G_{2}(\Delta\eta, \Delta\varphi)$ and flow-magnitude and flow angular correlations are sensitive to the %the viscous attenuation in the final state transport parameters of the evolution. We present new measurements of the beam energy dependence of higher-order flow-angular de-correlations $r_n(\eta)(n=2,3)$, the transverse momentum correlator $G_{2}(\Delta\eta, \Delta\varphi)$, higher-order flow-angular correlation $\langle\cos(a_{1}n_{1}\Psi_{n1}+\cdots+a_{k}n_{k}\Psi_{nk})\rangle$ and higher-order flow-magnitude correlations $SC(n,m)\{4\}$ and $SC(n,m)\{6\}$ for various event-shape and centrality selections of Au+Au collisions in different BES energies ( $\sqrt{s_{NN}}$ = 200 - 11.5 GeV) at RHIC. We observe a non-monotonic behavior in the longitudinal width of $G_{2}(\Delta\eta, \Delta\varphi)$ with the collision energy, which is expected to be proportional to $\eta/s$ according to the ansatz proposed by S. Gavin et. al.~[1]. Through these measurements we aim to gain insights into the role of electromagnetic fields and transport parameters of the QGP by disentangling the initial and final state effects.

[1] S. Gavin and M. Abdel-Aziz, Phys. Rev. Lett. 97, 162302 (2006)

Speaker: ADITYA PRASAD DASH (University of California Los Angeles)

QM2023_presentation_Aditya.pdf

17:30 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)

SY_QM2023.pdf

17:50 Probing initial state effects in nuclear collisions via jet and top quark measurements with the ATLAS detector

Proton-lead collisions at LHC energies offer a unique possibility to investigate initial state effects in nuclear collisions. Thanks to its wide acceptance, ATLAS can measure several probes that can help characterize these effects over a wide kinematic range. By analyzing the centrality dependence of dijet production, it is possible to investigate the suppression of dijet events in central events compared to peripheral ones and correlate it to the kinematic of the parton-parton scattering, accessible thanks to the measurement of both jets in the final state. In 2016, the ATLAS experiment collected 165 nb$^{-1}$ of proton-lead collisions at a centre-of-mass energy of 8.16 TeV per nucleon pair. In this talk, we will present a new measurement of the centrality dependence of dijet production obtained using this dataset. We will also present the first measurement of the inclusive cross-section for top-quark pair production in dilepton and lepton+jet decay modes. This process is sensitive to effects at high Bjorken-x values, which are hard to access experimentally using other available probes, and thus provides complementary information on the behavior of nuclear parton densities.

Speaker: Patrycja Anna Potepa (AGH University of Krakow (PL))

QM2023-Potepa.pdf

16:30 → 18:10 New Theory: (3)

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

16:30 Studying exotic hadrons in high energy nuclear collisions

For heavy ion collisions in the TeV beam energy region, the large number of initial hard scatterings create a richly "doped" hot quark-gluon plasma containing many charm quarks/anti-quarks, thus providing a uniquely "charming" environment for the massive production of heavy flavor exotic hadrons such as the $\chi_{c1}$ (also known as X(3872)), X(6900) and Tcc states. While such exotic states have been studied for decades in hadron physics, many questions about their basic properties and intrinsic structures (e.g. large hadron molecules versus compact tetraquarks) are not understood. High energy nuclear collisions show promise as a new test ground that has the potential to help resolve some of these challenges, with fresh experimental data from LHCb and CMS indicating nontrivial partonic medium effects on their production. As an example to demonstrate such opportunity, we report recent calculations of the yield of $\chi_{c1}$ state based on two popular models of its possible configurations: a loose hadronic molecule or a compact tetraquark. It turns out that the two different structures have rather different sensitivity to the fireball volume in heavy ion collisions. By scanning centrality and thus systematically tuning the fireball volume, our dynamical simulations have indeed found about 2-order-of-magnitude difference in the $\chi_{c1}$ yield and a markedly different centrality dependence between hadronic molecules and compact tetraquarks. This offers a novel approach for using fireball size as a “yardstick” to calibrate the size of exotic hadrons and thus distinguishing the two scenarios. Lastly, the talk will discuss the ongoing progress in the recently formed ExoHad Topical Collaboration to integrate hadronic physics inputs with medium environment and examine exotic hadron properties both in quark-gluon phase and in hot hadron gas, which would be crucial for a successful program of studying their production in heavy ion collisions.

Speaker: Jinfeng Liao

LIAO_QM23.pdf

16:50 Far-off-equilibrium early-stage dynamics in high-energy nuclear collisions

We explore the far-off-equilibrium aspects of the (1+1)-dimensional early-stage evolution of a weakly-coupled quark-gluon plasma using hydrodynamics and kinetic theory. For a large set of far-off-equilibrium initial conditions we observe that the macroscopic evolution appears to violate simple rules based on the second law of thermodynamics. We provide an in-depth microscopic understanding of this apparently anomalous macroscopic phenomenon in terms of the novel concept of viscous cooling and establish its thermodynamic consistency. We use Boltzmann's H-function to formulate 'maximum-entropy hydrodynamics', a far-off-equilibrium macroscopic theory that can describe both free-streaming and near-equilibrium regimes of quark-gluon plasma in a single framework. Unlike traditional hydrodynamic theories but conceptually similar to anisotropic hydrodynamics which it generalizes and with which we compare, this formulation incorporates contributions to all orders in shear and bulk inverse Reynolds numbers, allowing it to handle large dissipative fluxes that characterize the early evolution stage in heavy-ion collisions. By considering flow profiles relevant for nuclear collisions at very high energies, we demonstrate that 'maximum-entropy hydrodynamics' provides excellent agreement with underlying kinetic theory throughout the fluid's evolution, especially in out-of-equilibrium regimes where traditional hydrodynamics breaks down.

Speaker: Chandrodoy Chattopadhyay (North Carolina State University)

QM23_CC.pdf

17:10 Charge-dependent anisotropic flow in relativistic resistive magneto-hydrodynamic expansion

We have investigated the charge-dependent anisotropic flow in high-energy heavy-ion collisions, using relativistic resistive magneto-hydrodynamics (RRMHD). For the description of time evolution of the ultraintense electromagnetic fields produced just after the collisions, construction of the relativistic resistive magneto-hydrodynamics (RRMHD) is indispensable
We construct a relativistic resistive magneto-hydrodynamic (RRMHD) numerical simulation code for high-energy heavy-ion collisions as a first designed code in the Milne coordinates. Then we confirm that our code reproduces well the results of standard RRMHD tests in the Cartesian coordinates. Also, we verify the semi-analytic solutions of the accelerating longitudinal expansion of relativistic resistive magneto-hydrodynamics in high-energy heavy-ion collisions in a comparison with our numerical result.
Next, we apply our RRMHD code to analysis of the charge-dependent anisotropic flow in high-energy heavy-ion collisions. We consider the optical Glauber model as an initial model of the quark-gluon plasma (QGP) and the solution of the Maxwell equations with source term of the charged particles in two colliding nuclei as initial electromagnetic fields. The RRMHD simulation is performed with these initial conditions in Au-Au and Cu-Au collisions at $\sqrt{s_{NN}}$= 200 GeV. We have calculated the charge-odd contribution to the directed flow $\Delta v_1$ and elliptic flow $\Delta v_2$ in both collisions based on electric charge distributions as a consequence of RRMHD. Our results show that the directed and elliptic flows are approximately proportional to the electrical conductivity of the medium in both collisions. In the highly resistive case, our results of the charge-odd contribution to the directed flow are consistent with STAR data in Au-Au collisions. Furthermore, in Cu-Au collisions, the charge-odd contribution to the directed flow has a non-zero value at η = 0 which is also proportional to electrical conductivity of the medium. We conclude that the charge-dependent anisotropic flow is a good probe to extract the electrical conductivity of the QGP medium in high-energy heavy-ion experiments.
Nakamura, Miyoshi, Nonaka and Takahashi, Phys.Rev.C 107 (2023) 1, 014901.
Nakamura, Miyoshi, Nonaka and Takahashi, Eur.Phys. J.C 83 (2023) 3, 229.
Nakamura, Miyoshi, Nonaka and Takahashi, Phys.Rev.C 107 (2023) 3, 034912.

Speaker: Chiho Nonaka

qm2023_nonaka_v3.pdf

17:30 Isotropization of a longitudinally expanding plasma with the 2PI effective action

A central question in heavy-ion collisions is how the initial far-from-equilibrium medium evolves and thermalizes. In this work we use the two-particle irreducible (2PI) effective action for the first time to answer this question. This requires including the fast longitudinal expansion that characterizes heavy-ion collisions. Our framework, the 2PI effective action, is non-perturbative and derived directly from the underlying quantum-field theory. It encompasses existing descriptions of the initial stages of heavy-ion collisions, such as classical-statistical field theory and kinetic theory, in different limits, and therefore gives a unified, microscopic picture of the initial stages. In this talk we focus on (\phi^4) theory (which shares many features with QCD) in the 2PI framework truncated at three loops. We calculate the evolution of energy density and pressure anisotropy, as well as the momentum distribution of quasiparticles in the medium and their thermal mass. This allows us to see for the first time the onset of isotropization in quantum field theory in a geometric setup relevant for heavy-ion collisions. We address open questions in the field that the 2PI effective action can answer rigorously, such as how strong classical fields become quasiparticles, the role of vacuum fluctuations and the dynamics of soft modes throughout the initial stages.

Speaker: Sigtryggur Hauksson (IPhT - CEA)

QM2023_hauksson.pdf

17:50 The Black Hole CGC double copy: Computing gravitational radiation in close hyperbolic encounters of primordial Black Holes

A double copy between 2 > N QCD amplitudes and Gravity amplitudes at high energies was first discovered by Lipatov in 1981. In published work with G. Dvali[1], we showed how a double copy between Black Holes and the CGC arises, with both systems saturating the Bekenstein bound. We discuss how this dual picture points to some missing features of the CGC. Most importantly theoretical techniques developed for the CGC allows one to compute gravitational radiation [2] in so-called close hyperbolic encounters of primordial blackholes accessible at next-generation gravitational wave observatories.
[1] G. Dvali and R. Venugopalan, PRD105 (2022) 5, 056026
[2] H. Raj and R. Venugopalan, in preparation

Speaker: Dr Raju Venugopalan (Brookhaven National Laboratory)

QM2023_Venugopalan.pdf

16:30 → 18:10 QCD at finite T and density: (3)

Convener: Volker Koch

16:30 Two-particle femtoscopy at the HADES experiment

Over the past decades, the properties of dense matter have been widely concerned in connection with hypernuclei and hyperons. Their existence inside neutron stars softens the Equation of State (EoS), consequently limiting their masses to be lower than two solar masses (known as the "hyperon puzzle"). The limited number of experimental references in the region of high baryon chemical potential poses significant challenges for constructing an EoS. The matter under conditions similar to neutron star cores can be obtained with low-energy heavy-ion collisions. The strong interactions for hyperons and clusters can be studied with two-body systems, for example, nucleon-hyperon (e.g., $p-\Lambda$) or nucleon-cluster (e.g., $p-d$, $p-t$, or $p-{}^{3}He$) as their interaction is not fully understood. Studies of two-particle correlations with clusters enable one to search for ground state of  ${}^{4}Li$, or the excited state of ${}^{4}He$. Created hadrons and clusters carry information available after thermal freeze-out. Therefore, photons with a relatively long mean free path and being emitted through the whole system's evolution are considered for studying earlier collision stages.

Femtoscopy is a technique of measuring two-particle correlations in momentum space, proven to be a powerful tool for determining parameters of interactions and lifetimes in heavy-ion physics. It allows for the investigation of collision-generated system's spacetime features, having a lifespan of $10^{-23}$ seconds and a lifetime of femtometers ($10^{-15}$ m). One can study the two-body interactions, geometry, and dynamics by conducting such measurements experimentally.

The analysis uses the HADES detector at GSI/FAIR (Germany). Using detectors included in the spectrometer (among others, electromagnetic calorimeters, capable of detecting neutral particles) combined with specially created software, a dedicated framework, and reconstruction algorithm, one can identify $\gamma$ particles, $\Lambda$ hyperons, and clusters. The $p-\Lambda$, $p-d$, $p-t$, $p-{}^{3}He$, and $\gamma-\gamma$ correlation functions will be presented for the first time.

Speaker: Mateusz Grunwald (Warsaw Universty of Technology)

MateuszGrunwald_HadesFemtoscopy_QM2023_v3.pdf

16:50 Measurements of $\it p$-$\Lambda$ and $\it d$-$\Lambda$ correlations in Au+Au collisions from the fixed-target program at the STAR experiment

Heavy-ion collisions offer a new way to understand nucleon-hyperon (N-Y) interactions. The two-particle correlation, which reveals valuable information about the space-time evolution of the particle-emitting source and final state interactions involving hyperons, is the primary observable of interest. The measurements of $\it p$-$\Lambda$ and $\it d$-$\Lambda$ correlations can shed light on the N-Y two body and the N-N-Y three body interactions, which are important to understand the inner structure and equation of state of neutron stars. Further, the measurement of $\it d$-$\Lambda$ correlations provides insight into the internal structure and binding energy of light hypernuclei.

In this talk, we present the precise measurement of $\it p$-$\Lambda$ correlation using high statics data and the first measurement of $\it d$-$\Lambda$ correlation with $\sqrt{s_{_{\rm NN}}}=$ 3 GeV Au+Au collisions from the fixed-target program at the STAR experiment. The correlation functions are analyzed within the Lednicky-Lyuboshitz formalism in order to characterize the emission source size, the scattering length, and the effective range of $\it p$-$\Lambda$ and $\it d$-$\Lambda$ interactions. The extracted parameters will be compared to those from other baryon correlations ($\it p$-$\it p$, $\it d$-$\it d$, $\Lambda$-$\Lambda$) and various effective theory model calculations. Finally, physics implications on final state interactions involving hyperons and the hypertriton inner structure will be discussed.

Speaker: Yu Hu

QM23_20230906_YuHu_pL_dL.pdf

17:10 Microscopic encoding of macroscopic universality: How do the universal behaviors near the QCD transition arise from quarks and gluons?

The core goal of heavy-ion collision experiments is to shed light on how the phases and properties of strong-interaction matter arise from the fundamental constituents and interactions of Quantum chromodynamics (QCD). To this end, heavy-ion collision experiments are searching for universal signs of criticality in the QCD phase diagram by measuring various macroscopic quantities. When those signatures of criticality are observed the ultimate scientific question will still remain unanswered— how do these universal behaviors at the macroscale arise from the microscopic degrees of freedom, quarks and gluons? In this talk we will answer this question.

Macroscopic properties of the strong interaction near its chiral phase transition exhibit scaling behaviors, which are the same as those observed close to the magnetic transition in a 3-dimensional classical spin system with $O(4)$ symmetry. We show the universal scaling properties of the chiral phase transition in Quantum Chromodynamics (QCD) at the macroscale are, in fact, encoded within the microscopic energy levels of its fundamental constituents, the quarks. We first establish a connection between the cumulants of the chiral order parameter, i.e. the chiral condensate, and the correlations among the energy levels of quarks in the background of gluons, i.e. the eigenspectra of the massless QCD Dirac operator. This relation elucidates how the fluctuations of the chiral condensate arise from the correlations within the infrared part of the energy spectra of quarks, and naturally leads to generalizations of the Banks–Casher relation for the cumulants of the chiral condensate. Then, through (2+1)-flavor lattice QCD calculations with varying light quark masses near the QCD chiral transition, we demonstrate the correlations among the infrared part of the Dirac eigenvalue spectra exhibit same universal scaling behaviors as expected of the cumulants of the chiral condensate. We find that these universal scaling behaviors extend up to the physical values of the up and down quark masses. Our study reveals how the hidden scaling features at the microscale give rise to the macroscopic universal properties of QCD.

Speaker: Dr Peter Petreczky (BNL)

qm23_Peter_Petreczky.pdf

17:30 Equilibrium and Dynamical Properties of Hot and Dense Quark-Gluon matter from Holographic Black Holes

By using the 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, 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]. Moreover, we obtain 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 endpoint and the line of first-order phase transitions predicted by the model [2]. We also show how the time-dependent holographic jet quenching parameter, obtained from Bjorken flow, may impact jet energy loss modeling/phenomenology.

[1] Grefa, J., Noronha, J., Noronha-Hostler, J., Portillo, I., Ratti, C., Rougemont, R. PhysRevD.104.034002
[2] Grefa, J.,Hippert, M., Noronha, J., Noronha-Hostler, J., Portillo, I., Ratti, C., Rougemont, R. PhysRevD.106.034024

Speaker: Joaquin Grefa

4_Grefa_QM2023.pdf

17:50 Temperature and Strong Magnetic Field Effects in Dense Matter

We study consistently the effects of magnetic field on hot and dense matter. In particular, we look for differences that arise due to assumptions that reproduce the conditions produced in particle collisions or astrophysical scenarios, such as in the core of fully evolved neutron stars. We assume the magnetic field to be either constant or follow a profile extracted from general relativity calculations of magnetars and make use of two realistic models that can consistently describe chiral symmetry restoration and deconfinement to quark matter, the CMF and the PNJL models. We find that net isospin, strangeness, and weak chemical equilibrium with leptons can considerably change the effects of temperature and magnetic fields on particle content and deconfinement in dense matter. This could be important for detecting quark matter e.g. in neutron star mergers.

[1] Submitted to Phys. Rev. D, e-Print::2304.02454 [nucl-th]
[2] Phys. Rev. D 102 (2020) 7, 076016, e-Print: 2004.03039 [nucl-th]

Speaker: Prof. Veronica Dexheimer (Kent State Universtity)

DexheimerQM.pdf

16:30 → 18:10 Small Systems: (3)

Convener: Gunther Roland (Massachusetts Inst. of Technology (US))

16:30 Multiplicity Dependence of Strange Hadron Production in Small Systems using the STAR detector

Strangeness enhancement has long been considered a signature of the quark-gluon plasma formation in heavy-ion collisions. Recently, strangeness enhancement has also been observed in small systems at the LHC, but the underlying physics is not yet fully understood. This motivates studies of strange hadron production in small systems at RHIC, where the energy density of system is expected to be smaller than that at the LHC and therefore a hot and deconfined medium is less likely to be created. Investigating the multiplicity dependence of strange hadron production in small systems can naturally connect to peripheral heavy-ion collisions, and contribute to understanding the role of event multiplicity in strange hadron production. Furthermore, such studies will serve as a baseline for similar measurements in central heavy-ion collisions.

In this talk, we will present new measurements of (multi-)strange hadrons ($K{_S}{^0}$, $\Lambda$) in $d$+Au and ($K{_S}{^0}$, $\Lambda$, $\Xi$) in $p$+$p$ collisions at 200 GeV, collected by STAR in 2015 and 2016 respectively. We will analyze the multiplicity dependence of strange hadron transverse momentum ($p_{\rm{T}}$) spectra, $p_{\rm{T}}$-integrated yield dN/dy, average transverse momentum, and yield ratios with pions. We also present nuclear modification factors and rapidity asymmetry ($Y_{\rm{Asym}}$) for these particles in $d$+Au collisions. We will discuss implications of our measurements on the possible formation of a hot and deconfined medium
and the origin of strangeness enhancement in small systems.

Speaker: Ishu Aggarwal

QM_I_Aggarwal.pdf

16:50 Latest ALICE results on charm and beauty hadronization mechanisms in pp collisions (remote)

The study of heavy-flavour mesons and baryons in hadronic collisions provides unique access to the properties of heavy-quark hadronisation in the presence of large partonic densities, where new mechanisms of hadron formation beyond in-vacuum fragmentation can emerge. Performing these measurements in intervals of charged particle multiplicities provides sensitivity to understand whether different hadronisation mechanisms are at play in small and large hadronic colliding systems.

In this contribution, ALICE will present a selection of the latest charm and beauty production measurements in proton-proton (pp) collisions, which can shed light on the modification of the heavy-quark hadronisation mechanisms. New published results of the production of all prompt charm ground states in pp collisions at $\sqrt{s}$ = 13 TeV, which allowed us to measure the charm fragmentation fractions and the $\mathrm{c\bar{c}}$ production cross section at midrapidity, will be shown. The new final measurement of non-prompt $\Lambda_\mathrm{c}^+$ baryons in the same collision system will be discussed to provide a quantitative comparison between the hadronisation properties of beauty and charm hadrons.
New measurements of $\Xi_\mathrm{c}^{0,+}$ production as a function of multiplicity in pp collisions at $\sqrt{s}$ = 13 TeV, of $\Xi_\mathrm{c}^{0}$ production in p--Pb collisions at $\sqrt{s_\mathrm{NN}}$ = 5.02 TeV and the first measurement of $\Xi_\mathrm{c}^{0}$ production in Pb--Pb collisions at $\sqrt{s_\mathrm{NN}}$ = 5.02 TeV will be also presented, shedding further light on the hadronisation of charm-strange baryons in different colliding systems. Finally, the status and prospects for the reconstruction of charm mesons and baryons on LHC Run 3 data, using the upgraded ALICE apparatus, will be shown for the first time.

Speaker: Jianhui Zhu (INFN-Padova)

20230906_QuarkMatter_JianhuiZhu_v7.pdf

17:10 ATLAS measurement of mean momentum fluctuations and correlations with the flow in pp, Xe-Xe, and Pb-Pb

The thermal fluctuations in the QGP medium formed in heavy ion collisions present themselves as event-wise $[p_\mathrm{T}]$ fluctuations in the final state. Recent studies have shown that in ultra-central collisions, fluctuations are sensitive to radial flow, random thermal motion, and nuclear deformation. They can provide constraints on the extent of thermalization of the QGP droplet. Also of interest recently are correlations of $[p_\mathrm{T}]$ with $v_n$ which were found to be sensitive primarily to the initial state fluctuations. Correlations of $[p_\mathrm{T}]$ with $v_n$ recently came into the focus of discussion in the community and in pp collisions, they were suggested as a probe of saturation effects. This talk presents precise measurements of up to 3rd order $[p_\mathrm{T}]$ cumulants as a function of multiplicity, and centrality with an emphasis on ultra-central collisions. These results have strong implications for understanding the impacts of the initial condition, medium thermalization, and medium properties on final state $[p_\mathrm{T}]$ fluctuations.

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

2023-09-03-qm-talk-tbold-v1.pdf

17:30 Insights on strange quark hadronization measuring (multi)strange hadron production in small collision systems with ALICE

Among the most iconic results of Run 1 and Run 2 of the LHC is the observation of enhanced production of (multi-)strange to non-strange particles, gradually rising from low-multiplicity to high-multiplicity pp or p-Pb collisions and reaching values close to those measured in peripheral Pb-Pb collisions. More insightful information about the production mechanism could be provided by measuring the full Probability Density Function (PDF) for the production of each strange particle specie and investigating if any deviation from pure uncorrelated statistical behavior is observed. Using this novel method, we can determine whether strangeness enhancement is connected to the high-multiplicity tail of the PDF or to a progressive increase in the number of events with few strange particles produced. In this contribution, we present new results on the full PDF for the production of $K^{0}_{\rm S}$, $\Lambda$, $\Xi$, and $\Omega$ in pp collisions at $\sqrt s$ = 5.02 TeV as a function of the multiplicity as well as single and pair production of the $\phi$ meson in pp collisions at 13 TeV. In addition, we present new results on the transverse momentum spectra of Σ+ and its charge conjugate anti-particle, in both minimum bias and high-multiplicity triggered pp collisions at √s=13 TeV, including prospects and performance of the reconstruction of Σ baryons in Run 3. The results are compared to state-of-the-art phenomenological models implemented in commonly-used Monte Carlo event generators, drastically enhancing the sensitivity to the different processes implemented in each approach.

Speaker: Sara Pucillo (Universita e INFN Torino (IT))

QM2023_Pucillo.pdf

17:50 Measurement of the sensitivity of two-particle correlations in pp collisions to the presence of hard scatterings

A key open question in the study of multi-particle production in high-energy $pp$ collisions is the relationship between the "ridge" - observed azimuthal correlations between particles in the underlying event that extend over all rapidities and hard or semi-hard scattering processes. In particular, it is not known whether jets or their soft fragments are correlated with particles in the underlying event. This talk presents measurements of two-particle correlations in $pp$ collisions at $\sqrt{s}=13$ TeV with two different particle-pair selections. In the first case, charged particles associated with jets are excluded from the correlation analysis. This shows that excluding charged particles associated with jets does not affect the measured correlations. In the second case, correlations are measured between particles within jets and charged particles from the underlying event. Particles associated with jets do not exhibit any significant azimuthal correlations with the underlying event, ruling out hard processes contributing to the ridge.

Speaker: Soumya Mohapatra (Columbia University (US))

QMTalk_v2a.pdf

19:30 → 22:00 Houston Ballet Performance

Thursday, 7 September

08:30 → 10:30 Plenary Session

Convener: Giulia Manca (Universita` degli studi di Cagliari and INFN, Cagliari, IT)

08:30 The Physics of small systems (remote)

Speaker: Jiayin Sun (Universita e INFN, Cagliari)

smallsystem_qm23_v2.pdf

09:00 Collective Dynamics - experimental overview

Speaker: David Dobrigkeit Chinellato (University of Campinas UNICAMP (BR))

DDChinellato-QM2023-ExperimentalCollectivity-04.pdf

09:30 Collective Dynamics - theoretical overview

Speaker: Yuuka Kanakubo (University of Jyväskylä)

kanakubo_QM2023.pdf

kanakubo_QM2023.pptx

10:00 EPJ Featured Talk: Exotic Particle and Nuclei

Speaker: Francesca Bellini (Universita e INFN, Bologna (IT))

EPJLicenseAgreement_Bellini.pdf

QM23_FrancescaBellini_final.pdf

10:30 → 11:00 Coffee Break

11:00 → 12:30 Plenary Session

Convener: Tetyana Galatyuk

11:00 Search for the critical endpoint

Speaker: Ashish Pandav

QM23_PandavA_e4.pdf

11:30 QCD at finite temperature and density - Criticality

Speaker: Volodymyr Vovchenko (University of Houston)

Vovchenko-QM2023.pdf

12:00 QCD at finite temperature and density - Equation of State

Speaker: Jamie Karthein (MIT)

JMKarthein_QM23_EoS_plenary.pdf

12:30 → 13:00 Boxed Lunch

13:00 → 18:00 Excursion to NASA

Friday, 8 September

08:30 → 10:30 Plenary Session

Convener: Lijuan Ruan

08:30 Initial State Physics

Speaker: Heikki Mäntysaari (University of Jyvaskyla (FI))

qm_mantysaari.pdf

09:00 Approach to Equilibrium

Speaker: Soeren Schlichting (Universität Bielefeld)

QM23_Schlichting.pdf

09:30 New theoretical developments

Speaker: Jürgen Berges (Heidelberg University)

JurgenBerges.pdf

10:00 Electromagnetic Probes

Speaker: Raphaelle Bailhache (Goethe University Frankfurt (DE))

08_09_2023_RB_EM.pdf

10:30 → 11:00 Coffee Break

11:00 → 12:30 Plenary Session

Convener: Christina Markert (University of Texas at Austin (US))

11:00 Ultra-peripheral Collisions

Speaker: Daniel Brandenburg (Ohio State University)

QuarkMatter_UPC_Plenary_final.pdf

11:30 Chirality, Vorticity and Spin Polarization - experimental overview

Speaker: Aihong Tang (Brookhaven National Laboratory)

AihongTang_QM2023.pdf

12:00 Quantum Computing for Nuclear Physics

Speaker: Martin J. Savage

Savage_QuarkMatter_Sept2023_v1p1_pdf.pdf

12:30 → 14:00 Lunch

14:00 → 16:00 Plenary Session

Convener: Christine Nattrass (University of Tennessee (US))

14:00 Jet modifications - experimental overview

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

JetsinMedium_QuarkMatter2023_Havener.pdf

14:30 Medium response to jets - experimental overview

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

QM2023_jet_medium_response_yeonju_noAnimation.pdf

15:00 Jet modifications and medium response - theoretical overview

Speaker: Daniel Pablos (INFN Torino)

qm23_pablos.pdf

15:30 Open heavy flavor - experimental overview

Speaker: Fabrizio Grosa (CERN)

QM2023_openhf_fgrosa.pdf

16:00 → 16:30 Coffee Break

16:30 → 17:30 Plenary Session

Convener: Roberta Arnaldi (Universita e INFN Torino (IT))

16:30 Quarkonium - experimental overview

Speaker: Andre Govinda Stahl Leiton (CERN)

QM2023_talk.pdf

17:00 Open heavy flavor and quarkonium - theoretical overview

Speaker: Miguel Angel Escobedo Espinosa

qm2023.pdf

20:00 → 22:30 Banquet Dinner

Saturday, 9 September

08:30 → 10:15 Plenary Session

Convener: Haiyan Gao

08:30 The Physics of the EIC

Speaker: Anna Maria Stasto (Penn State)

Anna_Stasto_QM23.pdf

09:00 Future Facilities and Instrumentation

Speaker: Luciano Musa (CERN)

Musa_QM_SEP_2023.pdf

09:30 Conference Summary and Outlook

Speaker: Helen Caines (Yale University (US))

CainesQM2023.pdf

10:15 → 10:45 Coffee Break

10:45 → 11:45 Flash Talks

Convener: Claudia Ratti

10:45 Introduction

Speaker: Claudia Ratti

Awardees.pdf

10:46 Proton-cluster femtoscopy at the HADES experiment

The coherent description of nuclear matter properties at high baryon densities is of utmost importance. The limited number of experimental references in the region of the phase diagram corresponding to Neutron Stars (NS) and NS mergers poses major challenges for constructing a universal Equation of State. The matter created in heavy-ion collisions at the HADES experiment can be characterized by similar thermodynamic quantities as NS mergers, thus becoming an essential reference for the studies of these compact stellar objects [1]. Understanding the properties of the newly created matter , such as the strong interaction between hadrons or the presence of bound states, provides substantial insight for such investigation.

One of the methods applied in these studies is femtoscopic correlations (FC). It is a unique tool for the determination of the interactions between hadrons and searching for possible nuclear matter exotic states. Nonetheless, FC is found to be sensitive to variations of EoS, which makes it a valuable reference for its studies.
This poster will present the newest results on the proton-cluster (deuteron, triton, and He-3) FC at the HADES experiment showing the presence of unbound ground state Li-4 and excited states of He-4. The interactions between proton and clusters will be discussed as well. This research brings us closer to understanding the essential properties of nuclear matter at higher baryon densities.

[1] HADES Collaboration: Nature Physics volume 15, pages 1040–1045 (2019)

Speaker: Maria Stefaniak

MariaStefaniak_flashTalk.pdf

MStefaniak_poster_final.pdf

10:52 Deep learning for flow observables in ultrarelativistic heavy-ion collisions

We train a deep convolutional neural network to predict hydrodynamic results for flow coefficients, average $p_T$ and charged particle multiplicities in ultrarelativistic heavy-ion collisions from the initial energy density profiles event-by-event [1]. We show that the network can be trained accurately enough so that it can reliably predict the hydrodynamic results for the flow coefficients and, remarkably, also their correlations like normalized symmetric cumulants, mixed harmonic cumulants and flow-$p_T$ correlations. At the same time the required computational time decreases by several orders of magnitude. To demonstrate the effectiveness of the neural network, we train it using 5k hydro events, and validate it using 90k events per collision energy. The events are computed from the pQCD + saturation + hydrodynamics -based EKRT framework supplemented with a dynamical decoupling condition that improves the description of peripheral collisions [2]. We then generate 10M events using neural network and show that increasing the number of events from 90k to 10M can have significant effects on certain statistics-expensive flow correlations. Neural networks will therefore enable adding statistics-expensive flow correlations to the global Bayesian analysis with a fraction of computation time compared to the current state-of-the-art procedures [3].
$ $
[1] H. Hirvonen, K. J. Eskola and H. Niemi, arXiv:2303.04517 [hep-ph]
[2] H. Hirvonen, K. J. Eskola and H. Niemi, Phys. Rev. C 106, no.4, 044913 (2022)
[3] H. Hirvonen, J. Auvinen, K. J. Eskola and H. Niemi, in preparation

Speaker: Henry Hirvonen (University of Jyväskylä (FI))

QM2023_flash_talk_Hirvonen.pdf

QM2023_poster_Hirvonen.pdf

10:58 Measurement of Two-Particle Correlations and Flow Coefficients in High Multiplicity $e^+e^-$ Collisions using Archived ALEPH Data at 91-209 GeV

We present measurements of two-particle angular correlations of charged particles emitted in high-energy $e^+e^-$ collisions using data collected by the ALEPH detector at LEP between 1992 and 2000. The correlation functions are measured over a wide range of pseudorapidity and azimuthal angle as a function of charged particle multiplicity. Previous measurement with LEP1 data at $\sqrt{s}=91$ GeV shows no significant long-range correlations in either lab coordinate or thrust coordinate analyses, with associated yield distributions in agreement with predictions from the PYTHIA v6.1 event generator. The use of higher collision energy LEP2 data allows access to not only higher event multiplicitybut also to additional production channels beyond the $e^+e^- \to \gamma^\star/Z \to q\bar{q}$ process. Notably, the highest multiplicity bin ($N_{\rm trk} \ge 50$) suggests a tantalizing disagreement with MC and implies the potential to search for collective phenomena in small systems. This measurement is pushing the studies of long-range correlation to the smallest collision system limit and includes the first flow coefficient ($v_n$) measurement in $e^+e^-$ collisions, which uses a Fourier decomposition analysis to quantify the anisotropy in the azimuthal two-particle correlation as a function of charged particles' transverse momentum. This work supplements our understanding of small-system references to long-range correlations observed in proton-proton, proton-nucleus, and nucleus-nucleus collisions.

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

QM2023_AlEPHee2PC_draft_v1.pdf

QM2023_poster.pdf

11:04 Measurements of Hypertriton Production in Au+Au Collisions at 3 to 7.7 GeV

Hypernuclei are bound states of nuclei with one or more hyperons. Precise measurements of hypernuclei properties and their production yields in heavy-ion collisions are crucial for the understanding of their production mechanisms. The strangeness population factor, $S_{\rm A}=(^{A}_{\Lambda}\mathrm{H}/^{A}\mathrm{He})/(\Lambda/p)$ (A=3,4), is directly related to the ratio of light nuclei and hypernuclei coalescence parameters $B_{A}$. It eliminates canonical correction factors for strangeness and is independent of the chemical potential of the produced medium.
The STAR Beam Energy Scan II program offers us a great opportunity to investigate collision energy and system size dependence of hypernuclei production.

In this poster, we present new measurements on transverse momentum ($p_T$), rapidity\,($y$), and centrality dependence of $\rm ^{3}_{\Lambda}H$ production yields in Au+Au collisions from $\sqrt{s_{\rm NN}}=$ 3 to 7.7 GeV. Strangeness population factors $S_{3}$ and $S_{4}$ as functions of collision energy, centrality, $p_T$, and $y$ will be reported. These results are compared with phenomenological model calculations, and physics implications on the hypernuclei production mechanism will also be discussed.

Speaker: Yuanjing Ji (Lawrence Berkeley National Lab)

QM2023_poster_template_v6.pdf

talk_FXT_H3L_Sep08_v11.pdf

11:10 Dijet imbalance for jets of various radii in Pb+Pb and $pp$ collisions with the ATLAS detector

Measurements of dijets that traverse a quark-gluon plasma can provide insights into the jet energy loss in heavy ion collisions. Furthermore, considering jets of various sizes can help elucidate how the parton energy is transferred to the medium as well as the medium response. Measurements of the dijet momentum imbalance and nuclear modification factors for leading and subleading jet pairs were obtained using data from the ATLAS detector at the LHC. These measurements used 1.72 $nb^{-1}$ of Pb+Pb data collected in 2018, and 260 $pb^{-1}$ of $pp$ data collected in 2017, both at $\sqrt{s_{NN}} = 5.02$~TeV. Jets were reconstructed with the anti-$k_T$ algorithm using radii $R$=0.2, 0.3, 0.5, and 0.6, and were compared to previous results using $R$=0.4. The measurements were unfolded in the leading and subleading jet $p_\mathrm{T}$ to correct for the jet energy resolution. These measurements will improve the understanding of the jet energy loss process.

Speaker: Anabel Romero (Univ. Illinois at Urbana Champaign (US))

poster_qm23_aromero_v3.pdf

qm23_flashtalk_aromero_v3.pdf

11:16 Dynamics of causal hydrodynamic fluctuations in an expanding system

Nowadays, relativistic dissipative hydrodynamics including effects of finite viscosities is commonly used to extract transport properties of the quark gluon plasma (QGP), such as shear viscosity and bulk viscosity, from experimental data. However, according to the fluctuation-dissipation relation (FDR) in non-equilibrium statistical physics, fluctuations and dissipation are always accompanied with each other. Since phenomena induced by the hydrodynamic fluctuations, namely, thermal fluctuations associated with the viscosities, include the information of transport coefficients through FDR, these provide a multidimensional analysis of transport properties. Therefore, hydrodynamic fluctuations must be incorporated in the dynamical framework of relativistic heavy ion collisions. This could open up a new way of diagnosing the QGP properties precisely.

We derive equations of motion (EoM) of hydrodynamic fluctuations by considering the perturbative expansion of energy-momentum tensor around the Bjorken's boost invariant solution [1]. These EoMs are derived without any specific forms of constitutive equations contrary to a previous study in which constitutive equations from the first order dissipative hydrodynamics are assumed [2]. Therefore, this framework enables us to employ any kinds of constitutive equations at the second order dissipative hydrodynamics which satisfy the causality. This is the most precise framework in one-dimensional expanding system so far. With this framework, we describe the dynamics of (1+1)-dimensional causal hydrodynamic fluctuations and observe fluctuations of energy density are frozen in the early stage. It indicates that the distribution of energy density carries the information of the early stage of evolution. Furthermore, we analyze correlations of energy density fluctuations and find their behaviors are closely related with the properties of the medium such as relaxation time and sound velocity.

[1] J. D. Bjorken, Phys. Rev. D 27, 140 (1983).
[2] J. I. Kapusta, B. Muller, M. Stephanov, Phys. Rev. C 85, 054906 (2012).

Speaker: Shin-ei Fujii (Sophia Univ.)

Shin-eiFujii_FlashTalk.pdf

Shin-eiFujii.pdf

11:22 Strangeness enhancement at LHCb

Investigating particle production in small systems has become instrumental
in probing non-perturbative contributions to hadron structure and hadroniza-
tion mechanisms. The LHCb spectrometer unique geometry at the LHC along
with its particle identification and tracking capabilities allow for new studies
of the multiplicity-dependent enhancement of strange hadrons in the forward
region. Aggregating results of this kind will provide insight into how collective
effects modify hadronization, even in proton-proton collisions. In this contri-
bution, recent and upcoming measurements from the LHCb collaboration re-
garding the relative production rates of strange hadrons as well as how they are
modified by event activity will be discussed

Speaker: Desmond Mzamo Shangase (University of Michigan (US))

QM23 v2 (4).pdf

Strangeness enhancement at LHCb - QM2023 Final.pdf

11:28 Current status and future prospects of measuring hadronic interactions in pp collisions at 13.6 TeV with ALICE

Understanding the strong interaction between nucleons and hyperons is fundamental for the microscopic description of bound systems as well as for modeling the equation of the state of dense stellar objects, such as neutron stars. Conventional scattering and hypernuclei measurements are insufficient to support theoretical predictions about the interaction between hadrons containing strangeness. Recently, the ALICE Collaboration has shown that two-particle correlation measurements are a prominent tool for studying strong interaction in detail.

During the ongoing Run 3 data-taking period at the LHC, the upgraded ALICE detector will deliver an increased luminosity that will enable precision studies of interactions in hadronic systems with strangeness up to S=-3 and with charm quark content. Consequently, it will be possible to test lattice QCD calculations and chiral effective field theory models with unprecedented accuracy. This will require constraining the emission source using correlation measurements of particle pairs for which the final-state interaction is well known. For this, the p-p correlations were measured for the first time in Run 3 and will be presented in this talk. In addition, the p-$\Lambda$ correlation function was measured as a benchmark in the S=-1 sector. This is essential for the investigation of three-body nuclear forces, which are a vital missing element in the description of dense nuclear matter. The prospects for these future studies are discussed.

Speaker: Anton Albert Riedel (Technische Universitaet Muenchen (DE))

Anton_Riedel_FlashTalkQM2023-V2.pdf

PosterQM23_AntonRiedel.pdf

11:34 PHENIX Measurements of Azimuthal Anisotropy of Light and Heavy Flavor Hadrons in Au+Au Collisions at Forward Rapidity

One of the most prominent features of the quark gluon plasma is its near-perfect
fluid behavior. An important outstanding question is establishing the degree to which
heavy flavor particles flow with the bulk system. Measurements of the Fourier coefficient
v2 of light and heavy flavor hadrons can provide insight into the properties of the
medium. At low transverse momentum (pT) the mass dependence of v2
is associated
with the common flow velocity in the bulk system, whereas at higher pT path length and
mass dependencies in the energy loss play a role. We will present new results
measured with the PHENIX muon arms covering 1.2<|η|<2.2 using high statistics
Au+Au dataset collected in 2014. The v2 of light hadrons and muons from heavy flavor
decays are measured in the range 0.5<pT<5 GeV/c and the results are compared to
measurements at mid-rapidity. Forward rapidity samples different initial and final state
effects than mid-rapidity, and therefore the produced particles may be subject to
different pressure gradients. The measurements will be compared to theoretical
calculations.

Speaker: Brandon Blankenship

Bran_QM23_Flash_Talk.pdf

QM_poster_draft_final.pdf

11:40 The Intermediate Silicon Tracker of sPHENIX

The sPHENIX project is a new detector experiment at the Relativistic Heavy Ion Collider at BNL. Its aim is to study strongly interacting Quark-Gluon Plasma and cold-QCD by measuring photons, jets, jet correlations, and Upsilon family with high precision. To achieve these goals, a precise tracking system is necessary. The tracking system of the sPHENIX detector consists of the MVTX, TPC, TPOT, and the Intermediate Silicon Tracker (INTT). The INTT is a two-layer barrel silicon tracker that plays a unique role among the tracking detectors. It is capable of bridging the tracks of the MVTX and the TPC. In addition, its precise timing resolution enables the INTT to associate individual tracks and events to eliminate pile-up events. The INTT barrel installation and cabling were completed in March 2023. We have since commissioned and confirmed installation procedures and detector responses. The INTT status, performance evaluation by collision data, and calibration test results are presented in this poster.

Speaker: Cheng-Wei Shih (National Central University (TW))

INTT_QM2023_poster_LD_v5_new_revised.pdf

talk.pdf

11:45 → 12:00 Best Presentation Awards

TalkAwards.pdf

12:00 → 12:15 Zimanyi Medal Award

13_Zimany2023.pdf

12:15 → 12:35 QM 2025 Presentation

Speaker: Dirk Rischke (University Frankfurt)

12:35 → 12:55 Closing Remarks