Quark Matter 2018

13 May 2018, 09:00 → 19 May 2018, 13:10 Europe/Zurich

Venice, Italy

Federico Antinori (Universita e INFN, Padova (IT)), Paolo Giubellino (Universita e INFN Torino (IT))

Quark Matter 2018 is the XXVIIth International Conference on Ultra-relativistic Nucleus-Nucleus Collisions. This conference brings together theoretical and experimental physicists from around the world to discuss new developments in high energy heavy ion physics. The focus of the discussions is on the fundamental understanding of strongly-interacting matter at extreme conditions, as formed in ultra-relativistic nucleus-nucleus collisions, as well as on emergent QCD phenomena in high-multiplicity proton-proton and proton-nucleus collisions.

QM2018_Booklet_ForWeb.pdf

daily newsletters

• QM2018newsletter-Fri.pdf
• QM2018newsletter-Mon.pdf
• QM2018newsletter-Sat.pdf
• QM2018newsletter-Thu.pdf
• QM2018newsletter-Tue.pdf
• QM2018newsletter-Wed.pdf

Sunday, 13 May

Student Day

Timetable

1 Welcome and introduction

QM18Students_Welcome.pdf

2 The Quark-Gluon Plasma: a historical overview

Speaker: Reinhard Stock

Stock_Lecture_StudentDay_QM18.pdf

11:00 Coffee break

3 Open heavy flavours

Speaker: Andrea Rossi (Universita e INFN, Padova (IT))

Rossi_HF_v1.pdf

4 Quarkonia

Speaker: Alexander Rothkopf (Heidelberg University)

QM2018_QUARKONIUM_FINAL.pdf

5 The Masterclasses: a powerful outreach tool for secondary school students

Speaker: Yiota Foka (GSI - Helmholtzzentrum fur Schwerionenforschung GmbH (DE))

YF-IMCatQM-13may2018-asgiven.pdf

13:15 Lunch break

6 Modeling of jet quenching in heavy-ion collisions

Speaker: Korinna Christine Zapp (LIP Laboratorio de Instrumentacao e Fisica Experimental de Part)

JetQuenching_QM18.pdf

7 Small systems

Speaker: Livio Bianchi (University of Houston (US))

LivioBianchi_QM2018_SD.pdf

16:00 Coffee break

8 Hydro and Flow in nuclear collisions

Speaker: Jiangyong Jia (Stony brook Universty (US))

Jiangyong_QM2018_Lecture.pdf

9 The Modern View of Quark-Gluon Plasma

Speaker: William Zajc (Columbia University)

ZajcQM18.pdf

10 Discussion session

Registration

Monday, 14 May

Registration

11 Welcome and opening of the conference

• Welcome by chairpersons and steering committee
• Welcome by local authorities
• Welcome by INFN Padova and Physics and Astronomy Department directors

QM2018_opening.pdf

Plenary: I

Convener: Barbara Jacak (Lawrence Berkeley National Lab. (US))

12 Some considerations on the Quark-Gluon Plasma

Speaker: Prof. Giorgio Parisi (Università La Sapienza di Roma)

ParisiQuarkMatter.pdf

13 Highlights from the ALICE experiment

Speaker: Alexander Philipp Kalweit (CERN)

AliceOverviewVenice.pdf

10:30 Coffee Break

Plenary: II

Convener: John William Harris (Yale University (US))

14 Highlights from the ATLAS experiment

Speaker: Iwona Grabowska-Bold (AGH University of Science and Technology (PL))

QM18-AtlasHighlights-14052018-afterPreQM.pdf

15 Highlights from the CMS experiment

Speaker: Marta Verweij (Vanderbilt University (US))

180514_CMSOverview.pdf

16 Highlights from the LHCb experiment

Speaker: Michael Andreas Winn (Université Paris-Saclay (FR))

QM_talk_v2(2).pdf

17 Neutron stars and stellar mergers as a laboratory of dense QCD matter

Speaker: Aleksi Vuorinen

QM2018_pdf.pdf

QM2018.pptx

13:00 Lunch

Plenary: III

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

18 Highlights from the PHENIX experiment

Speaker: Dr Ron Belmont (University of Colorado Boulder)

phenix_qm18.pdf

19 Highlights from the STAR experiment

Speaker: Zhenyu Ye (University of Illinois at Chicago)

yezhenyu_QM2018.pdf

20 Collective effects: the viewpoint of HEP MC codes

Speaker: Torbjorn Sjostrand

sjostrand.pdf

16:00 Coffee Break

Collectivity in small systems: I

Convener: Urs Wiedemann (CERN)

21 Elliptic flow coefficients of identified hadrons in pp and p-Pb collisions measured with ALICE

Recent observations of long-range multi-particle azimuthal correlations in p-Pb and high multiplicity pp collisions provided new insights into collision dynamics and opened a possibility to study collective effects in these small systems.
In this talk, we present new measurements of $p_{\text{T}}$-differential elliptic flow coefficient $v_2$ for a variety of identified charged hadrons from pp and p-Pb collisions recorded by ALICE during the LHC Run 2 operation. The results for $v_2(p_{\text{T}})$ measured for $\pi^{\pm}$, $\text{K}^{\pm}$, $\text{K}^0_{\text{S}}$, p/$\bar{\text{p}}$, $\phi$ and $\Lambda/\bar{\Lambda}$ in p-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV are shown. Minimum-bias pp collisions are used to estimate and subtract the non-flow contribution in p-Pb measurements. Additionally, we present first measurements of $v_2$ of identified particles in pp collisions at $\sqrt{s}$ = 13 TeV.
The $p_{\text{T}}$ dependence, characteristic mass ordering and number of constituent quark scaling of $v_2$ allows us to test various theoretical models, constrain the initial conditions, and probe collective effects in small collision systems. Measurements of the $v_2$ of the $\phi$-meson, in particular, given it features a mass close to that of the proton, provide an opportunity to examine the particle production mechanism via quark recombination scenario.

Speaker: Vojtech Pacik (University of Copenhagen (DK))

QM18-Pacik-PIDv2pPb.pdf

22 A Quasiparticle Transport Explanation for Collectivity in the Smallest of Collision Systems ($p+p$ and $e^+e^-$)

Experimental evidence suggests that collectivity in asymmetric small systems ($p$, $d$, $^{3}$He+A) is directly related to the initial collision geometry. Therefore, a compelling question is whether the same argument can be extended to p+p, and even $e^+e^-$ collisions. We have modified A-Multiphase-Transport-Model (AMPT) to include the constituent quark structure of the proton. We find with very modest parton-parton cross sections a good description of the triangular and elliptic flow coefficients measured by ATLAS and CMS in p+p collisions, as a function of multiplicity and transverse momentum. We assess the non-flow separation techniques used by these experiments, by implementing their exact methods and comparing the result with the true flow relative to initial geometry in the model. The default AMPT model imposes formation times for partons which are much shorter than their respective de Broglie wavelength, at odds with a central assumption of semi-classical kinetic theory. This challenges the idea of modeling the QGP as well-defined quasi-particles undergoing Boltzmann evolution. We explore the impact on collectivity of enforcing a minimum de Broglie wavelength criterion, and find that it is significant for these smallest of systems. Lastly, we explore the minimal requirements for collectivity within this transport framework to determine whether the multiplicity and geometry of $e^+e^-$ collisions is sufficient to generate experimentally verifiable signals.

Speaker: James Lawrence Nagle (University of Colorado Boulder)

nagle_quarkmatter_quasiparticles_2018.pptx

23 Implications for small-system collectivity from a comprehensive set of soft physics measurements in a wide rapidity range in 200 GeV p$+$Au collisions by PHENIX

Proton-nucleus collisions play an important role as a control system for
interpreting hot nuclear matter effects in $A+A$ collisions. Yet, there is a large amount of data from both RHIC and the LHC that indicate that collective effects are also present in such small systems. Understanding the origin of these effects is still incomplete, since a variety of models with very different underlying physics have been shown to describe $p+A$ data.

We present a comprehensive set of measurements of soft-physics observables and
detailed comparisons with theoretical models. These measurements include
$v_2(p_T)$ and $v_3(p_T)$ for inclusive and identified particles at mid-rapidity, $v_2(p_T)$ for hadrons and heavy-flavor muons at forward rapidity, multi-particle correlations as a function of event multiplicity, the centrality dependence of $dN_{ch}/d\eta$, and identified particle spectra. The implications for the origin of collectivity in $p+Au$ collisions at RHIC will be discussed.

Speaker: Qiao Xu (Vanderbilt University (US))

QM2018-QiaoXu-final.key

QM2018-QiaoXu-final.pdf

24 Long-range azimuthal anisotropy of charm and strange hadrons in pPb collisions with the CMS detector

Measurements of long-range azimuthal correlations involving heavy-flavor quarks provide a powerful tool in unraveling the origin of collectivity observed in small collision systems. With data collected by the CMS experiment at the LHC in 2016, elliptic azimuthal anisotropy ($v_2$) of prompt $D^{0}$ meson at mid-rapidity in 8.16 TeV pPb collisions is presented from long-range two-particle correlations over a wide transverse momentum range. Results for light-flavor strange hadrons, including $K_{S}^{0}$, $\Lambda$, $\Xi^{-}$ and $\Omega^{-}$ are also presented in both pPb and PbPb collisions. Divided by the number of constituent quarks (NCQ), the NCQ scaling relation of $v_2$ among heavy and various light flavor species is tested. The result reveals key insights to heavy quark collectivity developed in high-multiplicity pPb systems.

Speaker: Wei Li (Rice University (US))

QM18-weili-smallsystem-05162018v4.pdf

25 Correlated gluonic hot spots meet symmetric cumulants data at LHC energies

The relevance of subnucleonic degrees of freedom and their fluctuations in the description of multiple experimental observations in small collision systems (flow harmonics, diffractive phenomena, hollowness effect...) has been recently established.
A representative example is the first measurement of symmetric cumulants, SC(n,m), performed by the CMS Collaboration in the three collision systems available at the LHC (p+p,p+Pb,Pb+Pb) [1]. In particular, SC(2,3), that provides a direct access to initial state fluctuations, shows a sign change with increasing centrality in p+p resembling the behavior of p+Pb and Pb+Pb interactions. This fact constitutes a powerful and stringent constraint on any realistic initial state model. We present a systematic study on the influence of spatial correlations between the proton constituents, in our case gluonic hot spots, their size and their number on SC(2,3) within a Monte Carlo Glauber framework [2]. When modeling the proton as composed by 3 gluonic hot spots, the most common assumption in the literature, we find that the inclusion of spatial correlations is indispensable to reproduce the negative sign of SC(2,3) in the highest centrality bins as dictated by data. Further, the subtle interplay between the different scales of the problem is discussed. To conclude, the possibility of feeding a 2+1D viscous hydrodynamic simulation with our entropy profiles and the theoretical uncertainties associated to this procedure are exposed.

[1] arXiv:1709.09189
[2] arXiv:1707.05592 (under review in PLB)

Speaker: Alba Soto Ontoso (UGR/FIAS)

qm18_ASO.pdf

26 Multiplicity dependence of strangeness and hadronic resonance production in pp and p-Pb collisions with ALICE at the LHC

One of the key results of the LHC Run 1 was the observation of an enhanced production of strange particles in high multiplicity pp and p-Pb collisions at 7 and 5.02 TeV, respectively. A smooth increase of strange particles relative to the non-strange ones with event multiplicity has been observed in such systems. Results from Run 2 at the top LHC energy are extended exploiting a dedicated high multiplicity trigger. This offers the unique opportunity to study, in elementary collisions, the multiplicity range covered by semi-peripheral Pb-Pb collisions.

We present the latest results on multiplicity-dependent strangeness production at LHC energies with ALICE. The strangeness enhancement is investigated by measuring the evolution with multiplicity of single-strange and multi-strange baryon production relative to non-strange particles. We also present recent measurements of mesonic and baryonic resonances in small collision systems. We investigate the system size dependence in pp and p-Pb collisions to study how hadronic scattering processes affect measured resonance yields, as well as the interplay between canonical suppression and strangeness enhancement. The measurement of the $\phi(1020)$ meson as a function of multiplicity provides crucial constraints in this context. Energy and system-type invariance are discussed and an extensive comparison with statistical hadronization and QCD-inspired models is presented.

Speaker: Ajay Kumar Dash (National Institute of Science Education and Research (IN))

AKDashQM2018Final.pdf

Correlations and fluctuations: I

Convener: Jacquelyn Noronha-Hostler (University of Houston)

27 Exploring chiral symmetry restoration in heavy-ion collisions with fluctuation observables

We study the critical properties of net-baryon-number fluctuations at the chiral restoration transition in a medium at finite temperature and net baryon density. The chiral dynamics of QCD is modeled by the Polykov-loop-extended Quark-Meson Lagrangian with the coupling of quarks to vector mesons. The Functional Renormalization Group is employed to properly account for the scaling properties of chiral observables at the phase boundary.

We focus on the properties of the net-baryon-number cumulants, $\chi_B^n$ for $n=1$ up to $n=8$, at and near the chiral phase boundary. We assess the influence of the location of the critical endpoint on the cumulant ratios and discuss the possibility to test non-equilibrium dynamics by comparing certain combination of baryon number susceptibilities.

The results are presented in the context of the recent experimental data of STAR and ALICE collaborations on fluctuation observables in heavy-ion collisions.

Speaker: Krzysztof Redlich (University of Wroclaw)

QM_REDLICH_2018.pdf

28 Investigating correlated fluctuations of conserved charges with cross-cumulants and net-lambda fluctuations in Pb-Pb collisions at ALICE

The fluctuations of conserved charges - such as electric charge, strangeness, or baryon number - in ultrarelativistic heavy-ion collisions provide insights into the properties of the hot and dense matter produced as well as the QCD phase diagram. They can be related to the moments of the multiplicity distributions of identified particles. We extend the previous and ongoing measurements of the cumulants of the net-pion, net-kaon, and net-proton distributions by investigating the correlated fluctuations of identified particles.
We present the first measurements with the ALICE detector of net-lambda fluctuations and of the off-diagonal cumulants between net-proton, net-pion and net-kaon distributions in Pb-Pb collisions. The results are obtained with the Identity Method, which, in particular, is applied in a novel way to account for the combinatoric background in the net-lambda analysis. The net-lambda fluctuations are compared with the corresponding net-proton and net-kaon results, previously measured by ALICE. Moreover, the off-diagonal cumulants are confronted with the lattice QCD predictions.

Speaker: Alice Ohlson (Ruprecht Karls Universitaet Heidelberg (DE))

aohlson_qm18_v5.pdf

29 Cross-correlations of conserved charges from the lattice

We present a lattice calculation on the cross-correlations of conserved charges
(baryon number, electric charge and strangeness) near the transition
temperature. We extrapolate to small baryo-chemical potentials, and thus we
cover typical STAR energies. We confront our finding to the latest STAR date
set on cross-correlations. In this work we use continuum lattice results with
resolution up to Nt=16.

Speaker: Jana Günther (University of Wuppertal)

talkGuentherArX.pdf

30 Fluctuations of conserved charges in the canonical ensemble: confronting experimental results with theory

We develop, within a canonical formulation of statistical mechanics, a systematic procedure to evaluate fluctuations of conserved quantities, such as baryon number, measured within an experimental acceptance. In nearly all experiments the baryon number fluctuations are approximated by the corresponding signals for net-proton measurements. We will discuss the validity and, in particular, the energy dependence of this approximation and provide quantitative estimates of differences between net-baryon number and net-proton fluctuations. Finally, we will compare our results up to the 4th cumulants with the corresponding measurements from the STAR and ALICE experiments.

Speaker: Anar Rustamov (National Nuclear Research Center (AZ))

Rustamov_QM_2018.pdf

31 Measuring the rate of isotropization of quark-gluon plasma using rapidity correlations

We propose that rapidity dependent momentum correlations can be used to extract the shear relaxation time $\tau_\pi$ of the medium formed in high energy nuclear collisions. The stress-energy tensor in an equilibrium quark-gluon plasma is isotropic, but in nuclear collisions it is likely very far from this state. The relaxation time $\tau_\pi$ characterizes the rate of isotropization and is a transport coefficient as fundamental as the shear viscosity. We show that fluctuations emerging from the initial anisotropy survive to freeze-out, in excess of thermal fluctuations, influencing rapidity correlation patterns. We show that these correlations can be used to extract $\tau_\pi$. In [1] we describe a method for calculating the rapidity dependence of two-particle momentum correlations with a second order, causal, diffusion equation that includes Langevin noise as a source of thermal fluctuations. The causality requirement introduces the relaxation time and we link the shape of the rapidity correlation pattern to its presence. Here we examine how different equations of state and temperature dependent transport coefficients in the presence of realistic hydrodynamic flow influence the estimate of $\tau_\pi$. In comparison to RHIC data, we find that the ratio $\tau_\pi/\nu \approx 5-6$ where $\nu=\eta/sT$ is the kinematic viscosity. We further make predictions for Pb-Pb collisions at the LHC.
[1] S. Gavin, G. Moschelli, C. Zin, Phys. Rev. C 94, 024921 (2016).

Speaker: Prof. George Moschelli (Lawrence Technological University)

Moschelli_QM2018.pdf

Moschelli_QM2018.pptx

32 Balance functions of identified hadrons in Pb-Pb, p-Pb and p-p collisions from ALICE

In ultrarelativistic heavy-ion collisions, correlations of particles with opposite quantum numbers provide insight into charge creation mechanisms, the time scales of quark production, collective motion of the QGP, and re-scattering in the hadronic phase. The longitudinal and azimuthal widths of general charge balance functions for pions, kaons, and protons are used to examine the two-wave quark production model recently proposed to explain quark-antiquark production within the QGP, which predicts a large increase in up and down quark pairs relative to strange quark pairs around the time of hadronization. Furthermore, the magnitudes of the balance functions for different particle pairs provide quantitative differential information on pair production channels. In addition, a detailed study of balance functions for different identified hadrons probes the fragmentation mechanism of strings into different quark flavors. Balance functions are also analysed in small collision systems such as p-Pb and pp to study fragmentation effects and possible collective effects in high-multiplicity events.

We present a comprehensive set of measurements of general charge balance functions for pions, kaons, protons, and unidentified particle pairs in Pb-Pb ($\sqrt{s_{\rm{NN}}}=$ 2.76 and 5.02 TeV), p-Pb ($\sqrt{s_{\rm{NN}}}=$ 5.02 TeV) and pp ($\sqrt{s}=$ 5.02 and 7 TeV) collisions in ALICE. Theoretical expectations and Monte Carlo models are then compared with the experimental data. In Pb-Pb collisions, we observe that the $\Delta y$ and $\Delta\varphi$ widths of the charged-pion balance function are narrower in central collisions compared to peripheral ones, while the widths of the charged-kaon balance functions do not show a centrality dependence. These results are consistent with expectations based on the two-wave scenario and radial flow.

Speaker: Jinjin Pan (Wayne State University (US))

JinjinPan_20180514_QM18_PID_BF_v11.pdf

Electromagnetic and weak probes: I

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

33 Direct photon production and flow at low transverse momenta in pp, p-Pb and Pb-Pb collisions

Direct photons are produced in various processes in pp, p-A and A-A collision and are sensitive to details of the space-time evolution the medium produced in heavy-ion collisions. The low $p_{\rm T}$ part of the direct photon spectrum is expected to be dominated by thermal direct photons - thermal radiation of hot matter, i.e., of the quark-gluon plasma and the hadron gas. At RHIC energies it is a challenge for hydrodynamical models to simultaneously describe the yield and the elliptic flow of direct photons in p-A and A-A collisions, which is often referred to as the direct-photon puzzle.

With ALICE, photons can be detected with either of the two electromagnetic calorimeters, EMCal and PHOS, and via reconstruction of $e^+e^-$ pairs from conversions in the ALICE detector material using the central tracking system. An additional hybrid method, combining the conversion information with that of the calorimeters has been developed. Where ever possible the results were combined to reflect our best estimate of the inclusive photon spectra and flow, $R_{\gamma}$, as well as the extraction of direct photon spectra or their upper limits and the flow.

In this talk, the first measurements on the direct photon production in pp collisions at $\sqrt{s} = 2.76$ and 8 TeV, as well as in p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV will be presented. Below 3 GeV/$c$, $R_\gamma$ was found to be consistent with unity in these collision systems. Furthermore, the direct photon spectra are in agreement with pQCD next-to-leading order calculations within the uncertainties. In addition, the final results on the direct photon elliptic flow ($v_{2}^{\gamma dir,SP}$) at $\sqrt{s_{\rm NN}} = 2.76$ TeV from the Pb-Pb run in 2010 in the $p_{\rm T}$ range of $0.9 < p_{\rm T} < 6.2$ GeV/$c$ will be presented in this talk. Comparisons to PHENIX results and to predictions of several theoretical models will be presented in order to shed light on the status of the direct photon puzzle at LHC energies.

Speaker: Friederike Bock (CERN)

QM2018_v2.pdf

34 PHENIX measurement of low momentum direct photon radiation from p$+$p and p$+$A collisions

In recent years data from small collision systems at LHC and RHIC have revealed
evidence for collective behavior of the produced hadrons. Collective behavior in
small systems clearly points towards a strongly coupled system being formed in
these collisions. If so, the matter formed must also radiate thermal or low
momentum direct photons. PHENIX is ideally positioned to search for any indications for thermal photon emission from small systems.

The versatility of RHIC allowed PHENIX to collect large data sets with a high
multiplicity trigger for p+p, p+A, d+Au and $^{3}$He$+$Au collisions at 200 GeV. These data sets are being analyzed with the methods already developed for the
measurement of low momentum direct photons from Au+Au collisions. Photons are measured through their conversions to electron-positron pairs in the material of the PHENIX vertex detector, and the fraction of direct photons is determined
after tagging photons from neutral pion decays. In this talk we will present
results from p+p and p+Au collisions.

Speaker: Vladimir Khachatryan (Stony Brook University)

QM2018_vkhachatryan.pdf

35 Direct photons in relativistic heavy-ion collisions: Tomography at multiple energy scales

In this talk, we present a systematic study of direct soft photon observables from the RHIC Beam Energy Scan (BES) to the LHC energies. We utilize the power of photons as clean and penetrating probes of the strongly-coupled nuclear matter created in relativistic heavy-ion collisions, together with the fact that the rapidly expanding Quark-Gluon Plasma (QGP) imprints its evolution on the photon spectrum and momentum anisotropies.

At higher energies, using the improved centrality selection in the recent hybrid approach [1], we first show that the tension in the direct photon elliptic flow between theory and experimental measurements is considerably reduced at both top RHIC and LHC energies. Then, predictions of the photon observables in Pb+Pb collisions at 5.02 TeV will be highlighted. At lower energies, a study of direct photon production in Au+Au collisions at 39 and 62.4 GeV will also be discussed. In particular, the role of finite baryon chemical potential in thermal photon emission will be quantified for the first time. The interplay between different collision energy scaling behavior for prompt and thermal photons in the final direct photon observables will be analyzed. This survey establishes photons as a powerful tool to elucidate the dynamics of QGP over a wide range of collision energies, to extract QCD transport coefficients, and to serve as a necessary complement to hadronic measurements.

[1] S. McDonald, C. Shen, F. Fillion-Gourdeau, S. Jeon and C. Gale, "Hydrodynamic predictions for Pb+Pb collisions at 5.02 TeV", Phys. Rev. C 95, no. 6, 064913 (2017)

Speaker: Jean-Francois Paquet (Duke University)

pres_jfpaquet_QM2018.pdf

36 Multi-differential pattern of low-mass e+e- excess from 2.42 GeV Au+Au collisions with HADES

The matter formed in central heavy-ion collisions at a few GeV per nucleon is commonly understood as resonance matter, a gas of nucleons and excited baryon states with a substantial contribution from mesonic, mostly pionic excitations. Yet, in the initial phase of the reaction the system is compressed to beyond nuclear ground state density and hence substantial modifications of the hadron properties are expected to occur.
The spectral distribution of virtual photons measured in Au+Au collisions at 2.42 GeV center of mass energy indicates strong medium effects beyond pure superposition of individual NN collisions. We present multi-differential distributions of low-mass electron pairs measured in Au+Au collisions at 2.42 GeV center of mass energy. The data is analyzed in terms of excess radiation above a conventional cocktail of contributions from meson decay after thermal freeze-out. This strong excess radiation is remarkably well described assuming emission from a thermalized system. To gain deeper understanding of the microscopic origin of the excess radiation, we extracted it centrality dependent true (not blue-shifted) temperature, its azimuthal distribution and polarization, as well as mass dependent effective slope parameter. Virtual photon spectra will be confronted with results of other experiments as well as with available model calculations.

Speaker: Szymon Harabasz

SzymonHarabasz_dileptons_QM2018_ver3.pptx

37 In-medium spectral functions of hadrons with the Functional Renormalization Group

We present an overview of recent results on in-medium spectral functions and transport coefficients of hadrons using the Functional Renormalization Group approach. Our method is based on a recently developed analytic continuation procedure that allows to calculate real-time quantities like spectral functions at finite temperature and chemical potential. Results for the quark, the sigma and the pion spectral function as well as for the shear viscosity over entropy density ratio are shown using the quark-meson model [1]. These quantities are studied in different regimes of the phase diagram, in particular near the chiral critical endpoint. Moreover, recent results for in-medium vector and axial-vector meson spectral functions are presented which are based on an extended linear-sigma model including quarks [2]. It is shown how the rho and the a1 spectral functions become degenerate at high temperatures and chemical potentials due to the restoration of chiral symmetry. Future applications of these recent developments are discussed, which include the calculation of dilepton spectra and the identification of experimental signatures of the chiral phase transition in the QCD phase diagram.

[1] R.-A. Tripolt, L. von Smekal, J. Wambach, Int. J. Mod. Phys. E26 (2017) 1740028
[2] C. Jung, F. Rennecke, R.-A. Tripolt, L. von Smekal, J. Wambach, Phys. Rev. D 95 (2017) 036020

Speaker: Dr Ralf-Arno Tripolt (ECT*)

Tripolt_Quark_Matter_2018.pdf

38 Low-mass dielectron measurements in pp, p-Pb and Pb-Pb collisions with ALICE at the LHC

The production of low-mass dielectrons is one of the most promising tools for the understanding of the chiral symmetry restoration and of the thermodynamical properties of the Quark-Gluon plasma (QGP) created in heavy-ion collisions. At low invariant mass, the dielectron production is sensitive to the properties of vector mesons in the medium and modifications related to the chiral symmetry restoration. In the intermediate mass region ($1.2 < m_{\rm ee} < 2.8$GeV/$c^2$) dielectrons are dominated by correlated electron pairs from heavy-flavour hadron decays, which carry information on the heavy-quark energy loss and collectivity. Thermal radiation from the medium contributes to the dielectron yield over a broad mass range and give insight into the temperature of the medium.

To single out the signal characteristics of the QGP, it is crucial to understand the primordial e$^{+}$e$^{-}$ pair production in vacuum, i.e. in minimum-bias proton-proton collisions, and to disentangle hot from cold-nuclear matter effects with p-Pb collisions. Moreover, observations of collective effects in high-multiplicity pp and p-Pb collisions show surprising similarities with those in heavy-ion collisions. The underlying physics processes in such events can be further studied with the measurements of correlated e$^{+}$e$^{-}$ pairs.

In this talk, we will give an overview of the latest measurements of e$^{+}$e$^{-}$ pair production in pp collisions at $\sqrt{s}$ = 7 TeV and 13 TeV, in p-Pb collisions at $\sqrt{s_{{\rm{NN}}}}$ = 5.02 TeV, and in Pb-Pb collisions at $\sqrt{s_{{\rm{NN}}}}$ = 2.76 TeV and 5.02 TeV with ALICE. Its implications for the production of heavy quarks and virtual photons will be presented, as well as the dependence of the dielectron spectra with the charged-particle multiplicity in the event, or the centrality of the collision. In Pb-Pb collisions, the comparison of the measured dielectron yield with the expectation from known hadronic sources will be discussed.

Speaker: Raphaelle Bailhache (Johann-Wolfgang-Goethe Univ. (DE))

rbailhache_QM2018.pdf

Initial state physics and approach to equilibrium: I

Convener: Bolek Wyslouch (Massachusetts Inst. of Technology (US))

39 Measurement of exclusive Upsilon photoproduction off protons in pPb collisions at sqrt(s_NN) = 5.02 TeV with CMS

Exclusive photoproduction of Upsilon(nS) meson states off protons is measured in ultraperipheral pPb collisions at a center-of-mass energy per nucleon pair of 5.02 TeV. The measurement is carried out in the $\Upsilon (nS)\to\mu^+\mu^-$ decay modes, with data collected by the CMS experiment corresponding to an integrated luminosity of $32.6$~nb$^{-1}$. Differential cross sections, as a function of the $\Upsilon$(nS) transverse momentum squared $p_{T}^2$, and rapidity $y$, are presented. The $\Upsilon$(1S) photoproduction cross section is extracted as a function of the photon-proton center-of-mass energy over the $91 < W_{\gamma p}<826$~GeV range. The data are compared to theoretical perturbative quantum chromodynamics predictions and to previous measurements.

Speaker: Ruchi Chudasama (Bhabha Atomic Research Centre (IN))

Ruchi_excl_upsilon_final_qm.pdf

40 Breaking Boost Invariance: IP-Glasma Phenomenology Beyond 2D

We present a novel formulation of the IP-Glasma initial state model in 3+1D, where the 2D boost invariant IP-Glasma is generalized to 3D through JIMWLK rapidity evolution of the pre-collision Wilson lines [1]. By breaking boost invariance, the 3D model no longer trivially satisfies Gauss' law at the initial time, and we now enforce it locally. We compare the time evolution of the chromo-electric and chromo-magnetic fields in the 3D case with the boost invariant result.

As the longitudinal dynamics of heavy ion collisions are measured to greater levels of precision, it is imperative that theoretical models describe the 3-dimensional nature of the Quark Gluon Plasma. We couple our 3D IP-Glasma model to MUSIC+UrQMD, for a fully 3-dimensional simulation of heavy ion collisions, and study the rapidity dependence of the second Fourier harmonic v2(η) and the charged hadron multiplicity dNch /dη.

[1]Bjoern Schenke and Soeren Schlichting. “3D glasma initial state for relativistic heavy ion collisions”. In: Phys. Rev. C94.4 (2016).

Speaker: Scott McDonald (McGill University)

McDonald_QM_18.pdf

McDonald_QM_18_updated.pdf

41 Nonequilibrium quark production in the expanding QCD plasma

In the high-energy limit of heavy-ion collisions, the system right after a collision is described as an over-occupied gluon plasma expanding in the beam direction. Its space-time evolution can be studied by means of real-time lattice gauge theory simulation techniques with dynamical quarks. To find observable consequences of such nonequilibrium evolution, the understanding of quark dynamics is crucial since they couple to electromagnetic probes. We present results for nonequilibrium quark production in the longitudinally expanding QCD plasma. We find that the quark number density per unit transverse area and rapidity shows almost linear growth in time, and its growth rate is consistent with a simple kinetic theory estimate involving only two-to-two scattering processes in small-angle approximation. We also show that the quark transverse momentum spectra for a wide range of quark masses exhibit an exponential shape that resembles a thermal Boltzmann distribution.

Reference: N. Tanji and J. Berges, arXiv:1711.03445

Speaker: Naoto Tanji (ECT*)

Tanji_QM2018.pdf

42 Charmonium production in ultra-peripheral heavy-ion collisions at LHCb

At the LHC, in ultra-peripheral heavy-ion collisions the highly boosted electromagnetic field of the Pb ions represents a source of quasi-real photon. Vector meson photo-production measurements in p-Pb (Pb-Pb) collisions are sensitive to the gluon parton distribution functions in the proton
(nucleus). LHCb results on charmonium production in ultra-peripheral p-Pb and Pb-Pb collisions will be presented.

Speaker: Albert Bursche (Universita e INFN, Cagliari (IT))

talk.pdf

43 Measurements of nuclear parton distribution functions using dijets, forward jets, and photo-nuclear jets at the CMS detector

Measurements of dijet production and photo-nuclear interactions in heavy-ion collisions probe several nuclear mechanisms. In particular, dijet measurements in pPb collisions have been shown to be one of the most important tools for constraining the gluon nuclear parton distribution functions (PDFs) at large Bjorken-x. Dijet production in pp and pPb collisions at a nucleon-nucleon centre-of- mass energy of 5.02 TeV is reported with the data samples collected with the Compact Muon Solenoid detector at the Large Hadron Collider. The dijet pseudorapidity distributions are measured as a function of dijet average transverse momentum in order to study the nuclear modifications of PDFs at various factorization scales. The final results from pp and pPb data samples are compared with next-to-leading- order perturbative QCD predictions obtained from both nucleon and nuclear PDFs. A significant modification of dijet pseudorapidity distributions in pPb collisions with respect to the measured pp reference is observed which indicates that the gluon PDF in lead ions is modified and the results are incompatible with predictions with DSSZ PDF without gluon EMC effects. Photo-nuclear jets are also measured in pp and pPb collision systems. The yield and angular correlation of low-pT jets at forward rapidity, $5.0<|\eta|<6.5$, are studied using the CASTOR calorimeter, which is sensitive to PDFs at low values of $x$ and $Q^2$. The prospects of future measurements of forward and ultra-peripheral jets in various collision systems as well as dijet production in pPb at 8.16 TeV and in Run III will be discussed.

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

DTT-QM 2018 14 May 2018 - v3.pdf

44 Charmonium photoproduction in ultraperipheral and peripheral Pb-Pb collisions with ALICE at the LHC

The electromagnetic field of relativistic heavy ions can be described by a flux of virtual photons. In ultraperipheral collisions (UPC), where the impact parameter is larger than the sum of nuclei radii, the interaction of these photons with the nucleus can provide insight into its structure and allow us to probe nuclear shadowing via photoproduction of charmonia.

Extensive efforts on this subject have been made by the ALICE collaboration and led to published measurements of J/Psi and Psi(2S) photoproduction in LHC Run 1 at forward (J/Psi) and at mid-rapidity. In addition, ALICE has reported a large excess of J/Psi at very low transverse momentum in peripheral Pb-Pb collisions, which is suggestive of coherent J/Psi photoproduction in collisions with nuclear overlap.

A substantially larger data set was recorded in LHC Run 2, allowing differential measurements in rapidity and in transverse momentum. In particular, the increased energy in Run 2 means that the Bjorken-x value probed in Pb-Pb UPC at midrapidity decreases from 10^-3 to 5*10^-4, and in collisions with nuclear overlap the measurement of the coherent J/Psi component becomes sensitive to its polarization and to the shape of its transverse momentum spectrum. At forward rapidity, the Run-2 dataset extends the measurement of photoproduced J/Psi beyond 50% in centrality, imposing strong constraints on initial-state models.

In this talk we will present the latest results on charmonium production in UPCs, final results on the J/Psi coherent photoproduction cross-section in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV with nuclear overlap at mid rapidity and new results at forward rapidity in the same system. The discussion will include comparisons to the ultraperipheral measurements and to theoretical model calculations. Perspectives for these measurements in LHC Run-3 and Run-4 will also be shown.

Speaker: Christoph Mayer (Polish Academy of Sciences (PL))

QM2018_DQ_UD_final.pdf

Quarkonia: I

Convener: Ralf Rapp (Texas A&M University)

45 Quarkonium measurements in nucleus-nucleus collisions with ALICE

Quarkonia, i.e. bound states of $b\bar{b}$ and $c\bar{c}$ quarks, are powerful observables to study the properties of nuclear matter under extreme conditions. The formation of a Quark-Gluon Plasma (QGP), which is predicted by lattice calculations at high temperatures as reached at LHC energies, has a strong influence on the production and behavior of quarkonia. A suppression, due to the color screening effect, with respect to the proton-proton results scaled by the number of binary collisions is expected. However, charmonium measurements from Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 and 5.02 TeV revealed a smaller suppression than what was observed at lower energies at the SPS and RHIC. Concurrently, the produced J/$\psi$ present a significant elliptic flow ($v_{2}$) in semi-central collisions. These measurements point to a competition between charmonium suppression and (re)generation at LHC energies, with a participation of the charm quarks to the collectivity of the medium. Thus quarkonium measurements offer great possibilities to gain further knowledge about the QGP.

In this presentation, latest ALICE results on the bottomonium and charmonium production in nucleus-nucleus collisions will be presented. This includes measurements of $\Upsilon$(1S) and $\Upsilon$(2S) nuclear modification factors ($R_{\rm AA}$) at forward rapidity and the charmonium $R_{\rm AA}$ and $v_{2}$ as a function of centrality, $p_{\rm T}$ and rapidity in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV. Also, first results from $J/\psi$ measurements in Xe-Xe collisions at $\sqrt{s_{\rm NN}}$ = 5.44 TeV will be presented. Further on, the experimental results will be compared to various calculations from theoretical models.

Speaker: Pascal Dillenseger (Johann-Wolfgang-Goethe Univ. (DE))

QM_pdillenseger_20180514.pdf

46 Quarkonia production in large and small systems measured by ATLAS

The experimentally observed dissociation and regeneration of bound quarkonium states in heavy-ion collisions provide a powerful tool to probe the dynamics of the hot, dense plasma. These measurements are sensitive to the effects of color screening, color recombination, or other, new suppression mechanisms. In the large-statistics Run 2 lead-lead and proton-lead collision data, these phenomena can be probed with unprecedented precision. Measurements of the ground and excited quarkonia states, as well as their separation into prompt and non-prompt components, provide further opportunities to study the dynamics of heavy parton energy loss in these large systems. In addition, quarkonium production rates, and their excited to ground states ratios, in small, asymmetric systems are an interesting probe of cold nuclear matter effects. In this talk, the latest ATLAS results on quarkonia production will be presented, including new, differential measurements of charmonium suppression and azimuthal modulation in lead-lead collisions, and a broad measurement of the production of five quarkonium states, differential in quarkonium kinematics, in proton-lead collisions.

Speaker: Jorge Andres Lopez Lopez (Federico Santa Maria Technical University (CL))

Lopez_QM2018_Talk.pdf

47 Quantum and Classical Dynamics of Heavy Quarks in a Quark-Gluon Plasma

Heavy quarkonium related observables are very useful to obtain information about the medium created in relativistic heavy ion collisions. In recent years the theoretical description of quarkonium in a medium has moved towards a more dynamical picture in which decay and recombination processes are very important. In this talk we will discuss the equations that describe the evolution of the heavy quarks reduced density matrix in different approximations, highlighting the color dynamics that is absent in the Abelian case, and we will study their semi-classical limit. This will allow us to obtain stochastic equations (similar to Langevin or Boltzmann equations) that can be useful to obtain phenomenological predictions. We will observe that the region of validity of the Langevin-like or Boltzmann-like equations in QCD is much smaller than in the corresponding QED case. The reason for this can be understood by studying how differently the free energy evolves in these two theories. This observation will allow us to propose an equation with a small computational cost that captures many of the essential features of quarkonium evolution in a QCD plasma.

These results are based on [1] and on work in preparation.

[1]-Quantum and Classical Dynamics of Heavy Quarks in a Quark-Gluon Plasma. ArXiv:1711.10812. J-P. Blaizot and M. A. Escobedo.

Speaker: Miguel Angel Escobedo Espinosa (University of Jyväskylä)

qm_escobedo.pdf

48 Quantum dynamical dissociation of quarkonia by wave function decoherence in quark-gluon plasma

In this study, we investigate the real-time evolution of quarkonium bound states
in a quark-gluon plasma in an improved QCD based stochastic potential model. This
model describes the quarkonium dynamics in terms of a Schrödinger equation with
an in-medium potential and two noise terms encoding the residual interaction
between the heavy quarks and the medium. The time evolution described by this
equation is unitary, since the effective potential term is real-valued. At a glance this is at odds with lattice results, but we explain why this it is
actually not the case.

We discuss the the time evolution of the existence probabilities of bound states in a static medium and in a boost-invariantly expanding quark-gluon plasma. We draw two conclusions from our results: One is that the outcome of the stochastic potential model is qualitatively consistent with the experimental data in relativistic heavy-ion collisions. The other is that the noise plays an important role in order to describe quarkonium dynamics in medium, in particular it causes decoherence of the quarkonium wave function. The effectiveness of decoherence is controlled by a new length scale, correlation length of the noise. Its effect has not been included in existing phenomenological studies, and we discuss its importance in detail.

Furthermore, if time allows, we also discuss strategies to take account of dissipation effects in addition to diffusion effects caused by the residual interactions between the heavy quarks and the medium.

[1] S. Kajimoto, Y. Akamatsu, M. Asakawa, and A. Rothkopf, arXiv:1705.03365, Phys. Rev. D in press.

[2] S. Kajimoto, Y. Akamatsu, M. Asakawa, and A. Rothkopf, in preparation.

Speaker: Shiori Kajimoto (Osaka University)

QM2018_kajimoto.pdf

49 Charmonium and bottomonium spectral functions from high precision lattice QCD computations

Understanding experimental results on nuclear modification factors of heavy quarkonia as well as open heavy mesons is complicated due to the interplay between the cold and hot medium effects. In order to disentangle these two effects it is crucial to have a good understanding of thermal behavior of quarkonia and heavy quarks in the hot medium. The quarkonium spectral function is of the most interest, as the deformation of its resonance peak structure relates to the dissociation temperatures of quarkonia and its slope at the vanishing frequency in the vector channel is connected to the heavy quark diffusion coefficient.

We will present our recent results on quarkonia spectral functions obtained from quenched lattice QCD simulations at $T\in [0.35, 2.25]T_c$. The simulations have been performed on very large and fine lattices where both charm and bottom quarks can be treated relativistically. Using multiple random sources we have computed charmonia and bottomonia correlators being 2 times more precise compared to our previous study[1,2]. In order to gain more robust information on the quark mass dependences of the thermal modifications we also computed the hadron correlators with additionally 4 different values of heavy quark masses ranging in between those of charm and bottom quarks.

We show reconstructed spectral functions from another two stochastic methods [3] besides the Maximum Entropy Method. This allows us to study systematic uncertainties of the dissociation of quarkonium states from temperature and quark mass dependence of the spectral functions. We also estimate heavy quark diffusion coefficients using the low-frequency behavior of vector spectral functions.


[1]H. Ohno, Quark Matter 2017
[2]H. Ohno, PoS LATTICE 2015 (2016) 175
[3]H.-T. Ding, O. Kaczmarek, S. Mukherjee, H. Ohno, H.-T. Shu, in preparation

Speaker: Mr Hai-Tao Shu (Central China Normal University)

Hai-Tao_Shu.pdf

50 Recent Quarkonia Studies from the PHENIX Experiment

Quarkonia breaking in nucleus-nucleus collisions is a powerful tool to probe
density and temperature of the medium created in heavy ion collisions. Forward rapidity measurements in $p(d)$+Au collisions are essential to understand how quarkonia states are affected by initial state effects, formation time, and local particle multiplicity. Earlier measurements in Au+Au collisions showed a stronger suppression of forward J/$\psi$s compared to mid-rapidity results, indicating the
possibility of a smaller contribution of regenerated quarkonia states at forward
rapidity.

This presentation will report on the latest quarkonia studies performed by the
PHENIX collaboration in the rapidity range 1.2$<|y|<$2.2, including (i) the
nucleus size dependence of the J/$\psi$ nuclear modification factor in $p$+Au, $p$+Al and $^3$He+Au collisions; (ii) the status of recent analyses of $\Upsilon$ states in $p$+$p$, $p$+Au, and in the large statistics 2014 Au+Au data set, the largest data set obtained by PHENIX.

Speaker: John Matthew Durham (Los Alamos National Laboratory)

Durham_QM18.pdf

Welcome Drink

Tuesday, 15 May

Chirality, vorticity and polarisation effects: I

Convener: Bedangadas Mohanty (National Institute of Science Education and Research (IN))

51 Global Polarization of Lambda Hyperons in Au+Au Collisions at 200 GeV from STAR

The matter created in non-central heavy-ion collisions is expected to possess a significant fraction of the initial angular momentum carried by the two colliding nuclei. This angular momentum can lead to vorticity of the system and be partially transferred to the spin of produced particles due to the spin-orbit coupling, leading to the phenomenon of global polarization. The STAR Collaboration observed finite signals in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7-39 GeV, indicating non-zero vorticity of the system, where the polarization decreases with increasing energy. The energy dependence can be understood by a shear flow structure in the initial state and/or the initial tilt of the source in combination with baryon transparency. Such a tilt and vorticity are closely related to the directed flow, elliptic flow, and the chiral anomalous phenomena. According to model calculations, the vorticity is expected to have a strong dependence on the hyperon emission angle relative to the reaction plane, but the models differ in their predictions. More precise and detailed experimental results are needed for further understanding of vorticity in heavy-ion collisions.

We present new results on the global polarization of Lambda hyperons in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV. Recent high-statistics data by a factor of hundred larger compared to previous results allow one to study differential dependencies of the polarization on the collision centrality, hyperon's transverse momentum, pseudorapidity, and emission angle relative to the reaction plane. The polarization dependence on the event-by-event charge asymmetry is presented and its possible relation to the axial current induced by the initial magnetic field is discussed. Furthermore, a possible local vortical structure along the beam direction caused by azimuthal anisotropic flow will be discussed.

Speaker: Takafumi Niida (Wayne State University)

QM18_talk_niida_v4.pdf

52 Spin alignment measurements using vector mesons with ALICE detector at the LHC

Large magnetic field and large angular momentum are expected to be present in the initial stages of high-energy heavy-ion collisions. One of the physics interests of the heavy-ion program using the ALICE detector at the LHC is to look for signatures of these effects. This can be achieved by studying the angular distributions of the decay daughters of hyperons and vector mesons.

We present new measurements related to spin alignment of K$^{*0}$ vector mesons at mid-rapidity for Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 and 5.02 TeV. The zeroth element of the spin density matrix element, $\rho_{00}$, is found to have values slightly below 1/3 at low transverse momentum ($p_{\mathrm{T}}$) for K$^{*0}$ mesons, while it is consistent with 1/3 (no spin alignment) at higher $p_{\mathrm{T}}$. No spin alignment is observed for K$^{*0}$ in pp collisions at $\sqrt{s}$ = 13 TeV and for the spin zero hadron K$^{0}_{S}$ in 20-40$\%$ Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV.
The $\rho_{00}$ values are not only sensitive to the angular momentum of the system but also to
the production mechanism of the vector meson. The centrality dependence of the $\rho_{00}$ results
with production plane and event plane in Pb--Pb collisions at LHC energies will be discussed in detail.

Speaker: Dr Ranbir Singh (NISER, Jatni, India)

KStarSpinAlignment_QM2018.pdf

53 Lambda polarization in heavy ion collisions: from RHIC BES to LHC energies

In hydrodynamic picture of heavy ion collisions, local thermal vorticity of the QGP fluid leads to polarization of nonzero spin hadrons produced out of it [1]. The nonzero polarization of $\Lambda$ hyperons has been recently discovered by STAR in non-central Au-Au collisions in RHIC Beam Energy Scan program [2].

We further study the predictions of the hydrodynamic model for different components of the $\Lambda$ polarization in the framework of 3-dimensional viscous hydrodynamic model with UrQMD initial state, and demonstrate that:

1. at RHIC Beam Energy Scan energies, the global polarization $P$ of produced Lambda is directed along the total angular momentum of the fireball (perpendicular to reaction plane). $P$ decreases with collision energy from 1.7 to 0.2% [3], in agreement with STAR results [2]. The global $\Lambda$ polarization further decreases towards LHC energies,

2. at full RHIC and LHC energies, the dominant component of polarization is the one in the beam direction. This component has a quadrupole structure in transverse momentum plane. Its amplitude $f_2$ shows a mild decrease with collision energy, and it is thus detectable at LHC enegries.

We show that different components of polarization are driven by different properties of the hydrodynamic expansion: whereas the global polarization $P$ is a result of initial shear flow in the reaction plane, $f_2$ is driven by anisotropy of the transverse expansion (which is also responsible for elliptic flow $v_2$). Polarization component in the beam direction is a generic effect present even in a simple 2-dimensional hydrodynamic calculation with longitudinal boost invariance [4].

[1] F. Becattini, V. Chandra, L. Del Zanna, E. Grossi, Ann. Phys. 338 (2013) 32.
[2] STAR collaboration, Nature 548 (2017), 62–65
[3] I. Karpenko, F. Becattini, Eur. Phys. J. C (2017) 77: 213.
[4] F. Becattini, Iu. Karpenko, arXiv:1707.07984, accepted to Phys.Rev.Lett.

Speaker: Dr Iurii Karpenko (SUBATECH Nantes)

QM2018.pdf

54 Global Lambda polarization in intermediate & high energy heavy ion collisions

Relativistic thermodynamics with spin provided the polarization 4-vector to characterize the spin alignment in rotating systems. Based on a Yang-Mills flux-tube initial state and a high-resolution, (3+1)D particle-in-cell relativistic (PICR) hydrodynamics simulation, we numerically obtain the polarization vector for $\Lambda$ hyperons at NICA and FAIR energies, and find that the $y$ component of the polarization vector is dominant, while $x$ and $z$ components are anti-symmetric in the transverse momentum space, implying a vanishing contribution to the global polarization (at collider frame). Besides, we analyze the dependence of $\Lambda$ polarization effect on centrality, energy and freeze-out time, in our model. The linear dependence of $\Lambda$ polarization on impact parameter reveals that the polarization stems from the initial orbital angular momentum; the polarization effect is found to decrease with increasing energy, which is in line with the recent results from RHIC BES program, and is attributed to the more intensive thermal motion of particles at higher energies. The time evolution of the $\Lambda$ polarization in our calculation agrees with the time evolution of vorticity predicted previously, and indicates the limit of applicability of hydrodynamic model at late stages of the expansion.
[1] Y.L. Xie, D.J. Wang, and L. P. Csernai, Phys. Rev. C 95, 031901(R) (2017).
[2] Y. L. Xie, M. Bleicher, H. Stöcker, D. J. Wang, and L. P. Csernai, Phys. Rev. C 94, 054907 (2016).

Speaker: Mr Yilong Xie (University of Bergen)

Global Lambda polarization in intermediate & high energy heavy ion collisions-Yilong Xie.pdf

Global Lambda polarization in intermediate & high energy heavy ion collisions-Yilong Xie.pptx

55 Relativistic hydrodynamics with spin

A new framework for relativistic hydrodynamics with spin is proposed. It is based on the conservation laws for charge, energy, momentum, and angular momentum. The conservation laws lead to hydrodynamic equations for the charge density, local temperature, and fluid velocity, as well as for the spin polarization tensor. The resulting set of differential equations extends the standard picture of perfect-fluid hydrodynamics, with a conserved entropy current, in a minimal way.

In addition, the properties of the relativistic spin density matrices for spin-1/2 particles, which have been used recently in works on the polarization of Lambda hyperons, are discussed. Their relations to the Pauli-Lubański four-vector and different forms of the spin tensor are elucidated.

The proposed framework forms a basis for hydrodynamic interpretation of polarization measurements in heavy-ion collisions.

Based on the recent work by WF, B. Friman, A. Jaiswal, and E. Speranza, "Relativistic fluid dynamics with spin", arXiv:1705.00587.

Speaker: Wojciech Florkowski (Institute of nuclear Physics, Krakow)

Florkowski-Venezia.pdf

Collective dynamics: I

Convener: Ulrich Heinz (The Ohio State University)

56 Measurements of anisotropic flow and flow fluctuations in Xe-Xe and Pb-Pb collisions with ALICE

Anisotropic flow is a key observable to characterize the system created in heavy-ion collisions, as it is sensitive to its initial state, transport properties, the equation of state and freeze-out conditions. In this presentation, we present the anisotropic flow coefficients of inclusive charged particles in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 and 5.02 TeV, and Xe-Xe collisions at $\sqrt{s_{NN}}$ = 5.44 TeV. The results are reported for a wide range of particle transverse momenta within the pseudo-rapidity range $|\eta| < 0.8$ at different collision centralities. The energy and system dependence are found to place strong constraints on the temperature dependence of $\eta/s$ and the modeling of the initial state respectively. We also present detailed studies of flow fluctuations in heavy-ion collisions, in order to precisely characterize the underlying flow probability distribution function. We find evidence of non-Bessel-Gaussian fluctuations and we discuss the origin of this observation.

Speaker: Jacopo Margutti (Utrecht University (NL))

jmargutti.pdf

57 System size dependence of flow observables in hydrodynamic simulations

Valuable information about the behavior of a heavy-ion collision system can be obtained by changing the species of colliding nuclei, and in particular using species of different size. This change in system size can probe characteristic behavior in a way that is not possible with a single collision system. Already, results of small collisions systems such as p-p, p-A, d-A, and $^3$He have received much attention. Recently, the LHC performed $^{129}$Xe-$^{129}$Xe collisions, a system with a size that is intermediate between small systems like p-p and large systems like Pb-Pb, at almost the same collision energy.

We perform hydrodynamic simulations of Xe-Xe and Pb-Pb collisions and argue that hydrodynamic behavior dictates definite relations between the results, regardless of the details of the simulations, due to scaling laws inherent to fluid dynamics. This can be used to test the hydrodynamic framework in general and search for a breakdown of hydrodynamics with decreasing system size.

Conversely, one can extract detailed information about system properties by studying carefully-selected observables. For example, the relative elliptic flow of the two systems in very central collisions is sensitive to the expected prolate deformation of the Xenon nucleus. Additionally, we describe a procedure to determine the average viscosity in a model-independent way by comparing selected ratios of flow coefficients in the two systems.

References: arXiv:1711.08499 and work in progress

Speaker: Matthew Luzum

LuzumQM2018.pdf

58 Elliptic and higher-order azimuthal anisotropies via multiparticle correlations in pPb and PbPb collisions with the CMS experiment

The elliptic and higher-order azimuthal anisotropy Fourier harmonics ($v_n$) are obtained for pPb collisions at $\sqrt{s_{NN}} = 8.16$ TeV over a wide range of event multiplicities based on multiparticle correlations. The data were collected by the CMS experiment during the 2016 LHC run. A sample of peripheral PbPb collisions at $\sqrt{s_{NN}} = 5.02$ TeV covering a similar range of event multiplicities to the pPb results is also analyzed for comparison. The ratios of different harmonic moments are obtained for both $v_2$ and $v_3$ with high precision, which allows a direct comparison to theoretical predictions assuming a hydrodynamic evolution of the created medium with initial-state density fluctuations, particularly probing the non-Gaussian nature of initial-state fluctuations in small collision systems. The presented results provide crucial insights into the origin of collective long-range correlations observed in small collision systems.

Speaker: Quan Wang (The University of Kansas (US))

QM2018.pdf

59 Phenomenology of the nonlinear coupling of flow harmonics in heavy-ion collisions

Precise measurements of higher-order coefficients of anisotropic flow ($v_n$, $n>3$) are now available in Pb+Pb data collected at the Large Hadron Collider. Higher-order coefficients are interesting because they do not simply originate as a response of the medium to its initial geometry, but rather from an intricate nonlinear coupling of harmonics of lower order. Hence, they serve as a powerful tool for the investigation of those properties of the quark-gluon plasma which are independent of the (so far very uncertain) initial conditions of the hydrodynamic evolution, such as its viscosity and freeze-out conditions.

I review the state-of-the-art framework describing higher-order harmonics, and I show that it is incomplete: It does not allow for a consistent characterization of flow coefficients defined with more than one nonlinear contribution, such as hexagonal flow, $v_6$. More specifically, I show that the present determinations of the nonlinear response coefficients of hexagonal flow, reported in both theoretical and experimental analyses, have been carried out under hidden underlying assumptions, which spoil the physical interpretation of the final results.

With the aim of curing these issues, I present an improved framework which encompasses the existing one, and allows for an exact characterization of any flow coefficient defined with an arbitrary number of nonlinear contributions. I perform an explicit application of the new framework to recent experimental data: I derive exact formulas for the nonlinear response coefficients of $v_6$, which I then extract from ALICE data. Doing so, I obtain the first experimental determination of the nonlinear coefficient coupling $v_6$ to $v_2$ and $v_4$. This quantity turns out to present a very specific centrality dependence, that is not captured by existing viscous hydrodynamic calculations. Promising applications of the presented formalism to upcoming high statistics Run2 data will be emphasized.

Speaker: Mr Giuliano Giacalone (Université Paris-Saclay)

pres_QM.pdf

60 Correlation between higher order flow harmonics and their non-linear modes for (un)identified charged hadrons in Pb-Pb collisions measured with ALICE

The recently proposed symmetric cumulants and non-linear flow mode coefficients provide new observational probes to study initial conditions and microscopic transport properties of the quark-qluon plasma (QGP) formed in heavy-ion collisions. Comparison of such measurements with viscous hydrodynamic calculations should, in particular, enable the study of the temperature dependence of the shear viscosity to entropy density ratio ($\eta/s$).
We present the measurements of symmetric cumulants and non-linear flow modes of charged hadrons up to the 8th harmonic in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$=5.02 TeV. The results will be compared to those at lower energies and to calculations from hydrodynamic models. Together they provide better constraints on the initial conditions, $\eta/s(T)$ and freeze-out conditions. In addition, we present the first results of $p_{\rm{T}}$-differential non-linear flow modes for charged pions, kaons and (anti-)protons measured in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$=5.02 TeV. These results cover a wide centrality range from ultra-central up to very peripheral collisions. These new results allow us to identify the contribution of the linear and non-linear terms to the observed mass ordering and particle-type grouping in different flow harmonics, thus providing increased discriminatory power in the study of initial conditions as well as a new stringent constraint to hydrodynamical calculations.

Speaker: Naghmeh Mohammadi (CERN)

QMtalk2018May15.pdf

Future facilities, upgrades and instrumentation: I

Convener: Harald Appelshaeuser (Johann-Wolfgang-Goethe Univ. (DE))

61 Future prospects for heavy ions at the LHC

Since its startup in 2009, the Large Hadron Collider at CERN has spent about 3 months of its operating time providing nucleus-nucleus (Pb-Pb) collisions. Peak Pb-Pb luminosity is now over 3 times design and integrated luminosity is expected to attain the initial design goal of 1 nb-1 in the 4th Pb-Pb run in late 2018. Following the demonstration of their feasibility in 2012, two one-month runs have been devoted to proton-nucleus (p-Pb) collisions in multiple conditions, with luminosity far beyond expectations. Recently, Xe-Xe collisions have also been demonstrated in a short run. All the LHC experiments now participate fully in the heavy-ion programme.

With this experience in hand, strategies to overcome physical performance limits established, and upgrades to the LHC and its injector chain in the pipeline, it is timely to take stock of the prospects and challenges for future performance of the LHC with nuclear beams.

Speaker: John Jowett (CERN)

QM2018 Jowett.pdf

62 Upgrade of the ALICE central barrel tracking detectors: ITS and TPC

The ALICE Collaboration will undertake a major upgrade of the detector apparatus during the second LHC long shutdown (LS2, 2019-20) in view of the Runs 3 and 4 (2021 to 2029). The objective of the upgrade is two-fold: i) an improvement of the tracking precision and efficiency, in particular in the low-momentum range; ii) an improvement of the readout capabilities of the experiment, in order to fully exploit the luminosity for heavy ions envisaged after LS2.
The first goal will be achieved by replacing the Inner Tracking System (ITS) with a new tracker, composed of seven layers of silicon pixel detectors. The ITS will be made up of about 25000 Monolithic Active Pixel Sensors with fast readout, resulting in a material thickness reduced to 0.3% (inner layers) – 1% (outer layers) of the radiation length and a granularity of $28\times28$ $\mu m^2$. The resolution of the track position will improve by about a factor of three in the direction transverse to beams and by a factor of five along the beams, reaching for example 20 $\mu m$ in both directions at a transverse momentum of 1 GeV/c.
The second goal will be achieved, among other measures, by replacing the readout chambers of the 90 $m^3$ Time Projection Chamber (TPC) with Micro Pattern Gas Detectors. In particular, the new readout chambers will consist of stacks of 4 Gas Electron Multiplier (GEM) foils combining different hole pitches. The upgraded detector will operate continuously without the use of a triggered gating grid. It will thus be able to record all Pb-Pb collisions at the anticipated LHC interaction rate of 50 kHz. New readout electronics will send the continuous data stream to a new online farm at a rate of 3 TByte/s.
The presentation will review the results of the extensive R&D programs, which are now concluded, the final technology and design choices, and the status of the production of the two detectors. Highlights of the physics programme with the upgraded ALICE central barrel will also be presented.

Speaker: Piotr Gasik (Technische Universitaet Muenchen (DE))

gasik_QM18_V6_Final.pdf

63 Muon physics at forward rapidity with the ALICE detector upgrade

ALICE is the experiment specifically designed for the study of the
Quark-Gluon Plasma in heavy-ion collisions at the CERN LHC. The ALICE detector
will be upgraded during the LHC Long Shutdown 2, planned for 2019-2020,
in order to cope with the maximum interaction rate of 50 kHz of Pb-Pb foreseen
for Runs 3 and 4.
The ambitious programme of high-precision measurements, expected for the
muon physics after 2020, requires an upgrade of the front-end and readout electronics
of the existing Muon Spectrometer. This concerns the Cathode Pad Chambers
(CPC) used for the tracking and the Resistive Plate Chambers (RPC) used
for triggering purposes and muon identification. The RPC will be operated with
amplification, contrary to what is currently done, with a new FEERIC front-end
chip. Regarding the CPC, a new all-in-one SAMPA chip will be used to equip the
1.1 million readout channels. For both systems the data transmission will use the
GBT chip, developed at CERN, and a Common Readout Unit (CRU) which will
send the data to the acquisition.
The Muon Forward Tracker (MFT), an internal tracker added in front of the
front absorber of the existing Muon Spectrometer, is also part of the ALICE detector
upgrade programme. It is based on an assembly of circular planes made
of Monolithic Active Pixel Sensors (MAPS), covering the pseudorapidity range
2.5 < $\eta$ < 3.6. The MFT will improve present measurements and enable new ones.
In particular, the precise measurement of the offset to the primary vertex for the
muon tracks will permit, for the first time in ALICE, the statistical separation of
open charm and beauty production at forward rapidity, rejecting at the same time
a large fraction of background muons coming from pion and kaon decays.
A selection of results from the physics performance studies will be presented,
together with an overview of the technical aspects of the upgrade project.

Speaker: Sabyasachi Siddhanta (Universita e INFN, Cagliari (IT))

Muon Physics with the Alice Upgrade_Siddhanta.pdf

64 The STAR BES II and Forward Rapidity Physics and Upgrades

The second phase of the Beam Energy Scan at RHIC, BES-II, is scheduled for 2019-2020 and will explore with precision measurements the high baryon density region of the QCD phase diagram. Some of the key measurements at center-of-mass energies at 19.6 GeV to 7.7 GeV in collider mode and 7.7 GeV to 3.0 GeV are: the kurtosis of net-protons that could pinpoint the position of a critical point, the directed flow of baryons vs. energy that might prove a softening of the equation of state, and the chiral restoration in the di-lepton channel. The measurements will be enhanced by the detector upgrades to extend STAR's experimental reach. The upgrades currently under way comprise: the replacement of the inner TPC sectors that increases the rapidity coverage of identified particles, the Event Plane Detector that improves the triggering and event plane resolution, and the end-cap TOF that extends the PID capabilities to larger rapidities in one hemisphere of STAR. Building on these upgrades STAR is planning to further enhance its detector capabilities by installing a Forward Calorimeter System integrating an electromagnetic and hadronic calorimeter and a Forward Tracking System combining 3 Silicon mini-strip disks and 4 Small-Strip Thin Gap Chamber (sTGC) wheels ala ATLAS. The upgrade is motivated by studying the initial state of nucleons and nuclei and the exploration of cold QCD physics in the very high and low regions of Bjorken $x$. The talk will highlight the physics opportunities enabled by these upgrades.

Speaker: Qian Yang (Shandong University)

QM2018_BESIIandForward_QianYang_final.pdf

65 Jet Physics with the Novel Calorimeter System for the sPHENIX Detector at RHIC

The sPHENIX experiment at RHIC will collect high statistics proton-proton, proton-nucleus and nucleus-nucleus data, starting in the early 2020's. The sPHENIX capabilities enable state-of-the-art studies of jet modification, upsilon suppression and open heavy flavor production to probe the microscopic nature of the strongly-coupled Quark Gluon Plasma, and will allow a broad range of cold QCD studies.

The sPHENIX detector will provide precision vertexing, tracking and electromagnetic and hadronic calorimetry in the central pseudorapidity region $|\eta| < 1.1$, with full azimuth coverage, at the full RHIC collision rate, delivering unprecedented data sets for hard probe tomography measurements at RHIC.
In this talk we will present a brief overview of the sPHENIX detector design with emphasis on calorimetry. The novel design of the sPHENIX calorimeters includes a tungsten/scintillating fiber electromagnetic calorimeter and two steel/scintillating tile hadronic calorimeter sections. The design is optimized for high jet energy resolution, while special attention to possible biases resulting from the combination of a relatively thin hadronic calorimeter and the large fluctuations in hadronic shower composition and shower development that usually limit calorimeter performance in large systems. The solution we have chosen – deep longitudinal segmentation with towers in each longitudinal section overlapping in azimuth and rapidity – was extensively simulated within the GEANT4 simulation framework and repeatedly tested in particle beams in the T1044 test beam facility at FNAL. Both simulation data and test beam data, and the resulting jet physics performance, will be presented in this talk.

Speaker: Yongsun Kim (Univ. Illinois at Urbana Champaign (US))

QM2018_sPHENIX_YongsunKim_v3.pdf

Jet modifications and high-pT hadrons: I

Convener: Xin-Nian Wang (Central China Normal University (China)) / Lawrence Berkeley Na)

66 Energy and system dependence of nuclear modification factors of inclusive charged particles and identified light hadrons measured in p-Pb, Xe-Xe and Pb-Pb collisions with ALICE

We report recent ALICE results on primary charged particle and neutral meson production in pp (2.76, 5.02, 7 and 8 TeV), p-Pb (5.02 TeV), Pb-Pb (2.76 and 5.02 TeV) and Xe-Xe (5.44 TeV) collisions. The transverse momentum ($p_{\rm T}$) spectra of charged hadrons used in the analysis were measured in the kinematic range of $0.15 < p_{\rm T} < 50$ GeV/$c$ and $ |\eta|< 0.8$. The charged hadron spectra from Pb-Pb and Xe-Xe collisions are divided in nine centrality intervals in the range of 0-80 %. As we achieved significantly smaller systematic uncertainties in the current analysis, the previously published results from p-Pb and Pb-Pb (2.76 TeV) collisions were reanalyzed.

Neutral mesons were reconstructed through their two-photons decays. The photons were measured via several complementary methods, using eighter the central tracking system identifying photons converted to $e^{+} e^{-}$ pairs in the material of the inner barrel detectors or the electromagnetic calorimeters. Thus we used the respective advantages of the detectors, i.e. the excellent momentum resolution of the conversion photons down to very low transverse momenta and the high reconstruction efficiency and triggering capability of calorimeters. This approach allowed to measure the neutral meson spectra in wide range of transverse momenta.

In this talk we will report a measurement of the nuclear modification factors of primary charged particles and of light neutral mesons in Pb--Pb (2.76 TeV and 5.02 TeV), in Xe-Xe (5.44 TeV) and in p-Pb (5.02 TeV) collisions with ALICE at the LHC. We compare the nuclear modification factors obtained for different collision systems as a function of transverse momentum, collision centrality as well as charged particle multiplicity (${\rm d}N_{{\rm ch}}/\rm{d}\eta$). We will present comparison to results from other experiments and to model calculations and review several scaling properties such as transverse mass scaling and $x_{\rm T}$ scaling in pp collisions.

Speaker: Daiki Sekihata (Hiroshima University (JP))

QM2018_GA_LF_v14.pdf

67 Charged particle nuclear modification factors in pPb, PbPb and XeXe collisions with the CMS experiment

The spectra of charged particles in XeXe and PbPb collisions at $\sqrt{s_{NN}} = 5.44$ TeV and $\sqrt{s_{NN}} = 5.02$ TeV, respectively, are presented in six ranges of collision centrality. The PbPb nuclear modification factor is constructed with a measured pp reference, and the XeXe nuclear modification factor is formed with an extrapolated pp reference. Both are found to be heavily suppressed in the most central collisions. The path-length and collision-energy dependence of parton energy loss are probed by comparing these two systems of differing size. The data are also compared to various theoretical models, as well as previous measurements at lower collision energies. The pPb nuclear modification factor is constructed using a measured pp reference and is seen to be slightly above unity for the highest transverse momentum probed by the measurement. This illustrates contributions due to initial-state effects, such as anti-shadowing in the nuclear parton distribution functions.

Speaker: Austin Alan Baty (Massachusetts Inst. of Technology (US))

Baty_XeXeRAA_QM2018_v8.pdf

68 Charged particle suppression in Pb+Pb, Xe+Xe, and $p$+Pb collisions measured with the ATLAS detector

The measurement of charge particle production in heavy ion collisions, when compared with $pp$ data, provides insight into the properties of the hot and dense quark-gluon plasma. The ATLAS detector at the LHC recorded 0.49 nb$^{-1}$ of Pb+Pb collisions, 25 nb$^{-1}$ of $p$+Pb collisions and 4.2 pb$^{-1}$ of $pp$ collisions, all at the center-of-mass energy $\sqrt{s_{NN}}=\sqrt{s}=5.02$ TeV. Recently, ATLAS also recorded 3 $\mu$b$^{-1}$ of Xe+Xe collisions at $\sqrt{s_{NN}}=5.44$ TeV, which offers a new opportunity to study the system size dependence of the parton energy loss. The large acceptance of the ATLAS detector allows measurements of charged hadron spectra in a wide range of both pseudorapidity and transverse momentum, differentially in collision centrality. The charged hadron spectra measured in Pb+Pb, Xe+Xe, and $p$+Pb collisions are compared to the analogous spectra measured in $pp$ collisions, and the resulting nuclear modification factors $R_\mathrm{AA}$ and $R_\mathrm{pPb}$ are studied.

Speaker: Petr Balek (Weizmann Institute of Science (IL))

PetrBalek_charged_hadrons.pdf

69 A simultaneous description of jet suppression and hadron suppression

Recent measurements of hadron and jet RAA at very high energies provide in combination crucial new input to our understanding of jet quenching. The increased precision of these observables has shown how hadrons and jets with comparable energies are suppressed differently. This is natural, since triggering on a high energy hadron constitutes selecting an unusual jet whose fragmentation pattern is unusually hard and unusually narrow in angle. By using the hybrid strong/weak coupling model including finite resolution, we study the various different physical effects that contribute to the observed results in data, and provide a simultaneous description of jet and hadron RAA data across the full kinematic range available in heavy ion collisions at the LHC. We also compare to hadron data from RHIC.

Speaker: Daniel Pablos (McGill)

pablos_qm18.pdf

70 Analysis of the apparent nuclear modification in peripheral 5.02 TeV Pb-Pb collisions with ALICE

We present charged particle spectra at midrapidity measured in lead-lead collisions at a center-of-mass energy per nucleon pair of 5.02 TeV with ALICE, in twenty centrality classes ranging from most central (0-5%) to very peripheral (95-100%) collisions. At high transverse momentum ($8 < p_{\rm T} <30$ GeV/$c$), the average nuclear modification factor ($R_{\rm AA}$) is found to increase from 0-5% central to 75-85% peripheral collisions, beyond which it strongly falls to very low values for the most peripheral collisions (95-100%). Our findings support the idea that peripheral collisions are affected by biases caused by the event selection and collision geometry, which can lead to an apparent nuclear modification in peripheral collisions even in the absence of jet quenching. The results in peripheral collisions are consistent with a PYTHIA-based model without nuclear modification. Our study provides an explanation of the observation that $R_{\rm AA}$ is lower than unity in peripheral Pb-Pb collisions, but equal to one in p-Pb collisions at similar charged particle multiplicity.

Speaker: Michael Linus Knichel (CERN)

MKNICHEL_RAAPERI_QM_2018-04-15.pdf

QCD at high temperature: I

Convener: Chihiro Sasaki

71 QCD equation of state at high temperatures

The equation of state (EoS) in $2+1$ flavor QCD has recently been established in the continuum limit at the physical quark masses in ab initio lattice QCD calculations. The HotQCD collaboration result provides the EoS in the temperature range from $130$ to $400$ MeV. We extend the HotQCD equation of state to higher temperatures. We utilize the Highly Improved Staggered Quarks (HISQ) action. We perform computations at the pion mass of about $300$ MeV since the effects of heavier than physical light quark masses are negligible above $400$ MeV. To control the cutoff effects and approach to the continuum limit, computations are done on the lattices with temporal extent $N_\tau=4$, $6$, $8$, $10$ and $12$. We provide a continuum estimate up to temperatures of 2 GeV.

Speaker: Alexei Bazavov (Michigan State University)

bazavov_qm18.pdf

72 Observation of approximate $SU(2)_{CS}$ and $SU(2*n_f)$ symmetries in high temperature lattice QCD

We study spatial isovector meson correlators in $n_f=2$ QCD with dynamical domain-wall fermions on $32^3\times 8$ lattices at temperatures $T=220-380$ MeV. We measure the correlators of all spin-one ($J=1$) isovector operators. We observe an approximate degeneracy of all considered correlators with increasing temperature. This approximate degeneracy suggests emergent $SU(2)_{CS}$ and $SU(2*n_f)$ symmetries at high temperatures, that mix left- and right-handed quarks.

Speaker: Christian Rohrhofer (Karl-Franzens Universität Graz)

qm18_rohrhofer.pdf

73 Chiral phase transition of (2+1)-flavor QCD

Understanding the properties of strong interaction matter with its physical
spectrum of light and strange quarks near the pseudo-critical temperature
of (2+1)-flavor QCD is one of the central goals of high energy nuclear
physics. It generally is expected that the analytic crossover transition in
QCD is sensitive to properties of the true chiral PHASE transition at
vanishing quark masses [1,2]. This sensitivity is increased in higher order
cumulants of net charge fluctuations which currently are being measured
by STAR and PHENIX at RHIC and by ALICE at the LHC.
In order to connect these experimental findings to predictions arising from
QCD in the chiral limit it is mandatory to establish the properties of QCD in
this limit. While there are many indications that the chiral PHASE
transition is a second order transition in the universality class of O(4)
sigma models [3], this is by no means established in lattice QCD
calculations as in none of these cases continuum extrapolated results
exist [4].
In this talk we will present the status of our calculations for (2+1)-flavor
QCD with the Highly Improved Staggered Quarks (HISQ) on three different
lattice sizes ($N_\tau = 6, 8, 12$) and with 5 values of light quark masses
that are up to a factor 6 smaller than in nature. This allows us to
systematically control the chiral and continuum limit of QCD. We show
that our results are consistent with O(N) scaling in the chiral limit,
supporting the existence of a second order phase transition. We will also
present first continuum extrapolated results for the PHASE transition
temperature in the chiral limit and discuss the relevance of corrections to
scaling that need to be controlled when extrapolating to QCD with its
physical quark mass spectrum.

[1] A. Bazavov et al., PRD 85 (2012) 054503
[2] A. Bazavov et al., PRD95 (2017) 074505
[3] S.-T. Li and H.-T. Ding, PoS LATTICE2016 (2017) 372
[4] H.-T. Ding, F. Karsch, and S. Mukherjee, IJMPE24 (2015) 1530007

Speaker: Anirban Lahiri (Bielefeld University)

al.pdf

74 Second-order transport coefficients at NLO in pQCD

In this talk we will study the relaxation coefficients $\tau_\pi$ and $\tau_J$ of the shear stress tensor $\pi^{\mu\nu}$ and the light quark current $J$ respectively. These are second-order transport coefficients which can be determined in perturbation theory. After reviewing the perturbative kinetic theory framework that has been recently used to determine their respective first-order coefficients $\eta$ and $D$ (shear viscosity and quark diffusion) at NLO in pQCD we will apply it to these second-order coefficients. While $\eta$ and $D$ get reduced by a factor of 5 at NLO for $\alpha_\mathrm{s}\sim0.3$, the dimensionless ratios $T \tau_\pi/(\eta/s)$ and $\tau_J/D$ show a mild increase ($<50\%$) at NLO. We further argue that, through the properties of the collision operator, lower bounds can be obtained in kinetic theory for these coefficients. After presenting the bounds, we compare our results with the strong-coupling AdS/CFT ones: we argue that, while (NLO) kinetic theory can yield first-order transport coefficients in the ballpark of the strong-coupling ones, the lower bounds imply widely different behaviours at second order.

Speaker: Jacopo Ghiglieri (CERN)

ghiglieri_QM18.pdf

75 T-Matrix Approach to Spectral and Transport Properties of the QGP

Understanding the microscopic properties of the hot and dense QCD matter produced at RHIC and the LHC is a critical task for heavy-ion physics. Toward this end, we have developed a non-perturbative microscopic approach to study the bulk, transport and spectral properties of the quark-gluon plasma (QGP) [1-2], treating light, heavy and static partons in a unified framework. Starting from a relativistic effective Hamiltonian with a universal color force, we employ a many-body T-matrix approach, solved self-consistently and constrained by lattice QCD (lQCD) data for the equation of state (EoS), heavy-quark (HQ) free energy and quarkonium correlator ratios. The predictive power resides in the emerging spectral functions and transport properties. In particular, we find a strongly coupled solution where the low-momentum low-temperature parton spectral functions dissolve due to collision widths in excess of 0.5 GeV and give a way to dynamically formed hadronic resonance/bound states which take over in the EoS. The calculations of the HQ diffusion coefficients and the shear viscosity to entropy density ratio yield values (and ratios) near the conjectured lower quantum bounds, corroborating the liquid-like structure of the QGP near Tc. An extension of the approach to finite baryon density and its implications for QCD phase structure will be discussed using benchmarks from various lQCD susceptibilities.
[1]SYF Liu, R Rapp, arXiv:1612.09138
[2]SYF Liu, R Rapp, arXiv:1711.03282

Speaker: Shuai Liu (Texas A&M University)

QM2018ShuaiLiu.pdf

QM2018ShuaiLiu.pptx

10:40 Coffee Break

Collective dynamics: II

Convener: Raimond Snellings (Nikhef National institute for subatomic physics (NL))

76 Fluid dynamics of out of equilibrium boost invariant plasmas

We establish a set of equations for moments of the distribution function. On the one hand, these equations generalize the fluid dynamics to the out-of-equilibrium evolution of boost invariant plasmas. On the other hand, they systematically generalize the theoretical framework of viscous hydrodynamics to arbitrary orders. These moments quantify details of the momentum anisotropies of out-of-eqilibrium phase space distributions. The evolution of these moments measures the evolution of systems towards thermalization to a finer level, beyond the commonly used ratio of longitudinal to transverse pressures. In the hydrodynamical regime, these moments are found to correspond to viscous corrections. In the relaxation time approximations, these moments obey a coupled set of equations that can be truncated order-by-order. Truncations at the lowest orders give rise to the exact form of the second order and third order viscous hydrodynamic equations of motion for the Bjorken flow. Solving the equations of the moments, we are able to identify an attractor solution that controls a transition from a free streaming fixed point to a hydrodynamic fixed point. In particular, this attractor solution provides a renormalization of the effective value of the shear viscosity to entropy density ratio, η/s, taking into account off-equilibrium effects.

[1] Jean-Paul Blaizot, Li Yan, JHEP 1711(2017) 161, arXiv:1703.10694
[2] Jean-Paul Blaizot, Li Yan, arXiv:1712.03856

Speaker: Li Yan (McGill University)

yan_talk.pdf

yan_talk_update.pdf

77 Measurement of the azimuthal anisotropy of charged particles in 5.02 TeV Pb+Pb and 5.44 TeV Xe+Xe collisions with ATLAS

The experimental data collected by the ATLAS experiment during the 2015 Pb+Pb and 2017 Xe+Xe LHC runs offer new opportunities to study charged particle azimuthal anisotropy. The high-statistics Pb+Pb sample allows for a detailed study of the azimuthal anisotropy of produced particles. This should improve the understanding of initial conditions of nuclear collisions, hydrodynamical behavior of quark-gluon plasma and parton energy loss. New ATLAS measurements of differential and global Fourier harmonics of charged particles ($v_n$) in 5.02 TeV Pb+Pb and 5.44 TeV Xe+Xe collisions in a wide range of transverse momenta, pseudorapidity ($|\eta|<2.5$) and collision centrality are presented. The higher order harmonics, sensitive to fluctuations in the initial state, are measured up to $n=7$ using the two-particle correlation, cumulant and scalar product methods. The dynamic properties of QGP are studied using a recently-proposed modified Pearson's correlation coefficient, $\rho(v_n^2,p_\mathrm{T})$, between the eventwise mean transverse momentum and the magnitude of the flow vector in 5.02 TeV Pb+Pb and $p$+Pb collisions. Several important observations are made. The elliptic and triangular flow harmonics show an interesting universal $p_\mathrm{T}$-scaling. A linear correlation between the $v_2$ and $v_3$ coefficients at low and high $p_\mathrm{T}$ ranges is observed and quantified. The Pearson's correlation coefficient $\rho(v_2^2)$ is found to be negative in peripheral and positive in central Pb+Pb collisions. The value of $\rho(v_3^2)$ is found to be much smaller than $\rho(v_2^2)$ and to have similar centrality behavior as $\rho(v_2^2)$.

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

2018-05-15-bold-quark-matter-atlas-flow.pdf

78 Kinetic transport is needed to reliably extract shear viscosity from pA and AA data

The azimuthal anisotropies of particle spectra measured in proton-nucleus (pA) and nucleus-nucleus (AA) collisions play a key role in constraining QCD matter properties like the shear viscosity over entropy density ratio eta/s. We compare calculations of v_n’s from viscous fluid dynamics and from kinetic transport which start both from the same initial conditions and which implement the same matter properties. We observe that both approaches lead to parametrically different eta/s-dependencies of the elliptic anisotropy v_2, and they may thus lead to quantitatively different results for the phenomenologically inferred value of eta/s. The parametric differences can be traced to the boost-invariant longitudinal expansion of pA and AA collisions which induces in fluid dynamic results of the eta/s-dependence of v2 a dominant sensitivity on the initial conditions. Transport theory is free of this problem and it accounts for the order of magnitude of experimentally observed signal strengths v_n with sizeable mean free path.

Speaker: Eero Aleksi Kurkela (CERN)

Kurkela_QM2018.pdf

79 Measurement of collective flow in XeXe collisions at 5.44 TeV with the CMS experiment

New measurements of collective flow in XeXe collisions at a center-of-mass energy of 5.44 TeV per nucleon pair, collected by the CMS experiment at the LHC, are presented. The $v_{2}$, $v_{3}$ and $v_{4}$ Fourier coefficients of the anisotropic azimuthal distribution are obtained employing three different analysis techniques: two-particle correlations, scalar product method and multiparticle cumulants, which have different sensitivities to non-flow and flow fluctuation effects. The results are shown as a function of transverse momentum ($p_{T}$) for various centrality selections, and compared with corresponding results from PbPb collisions. These new measurements in a smaller nucleus-nucleus system than PbPb provide additional insights into the system-size dependence of the collective flow induced by the dominant collision geometry and its fluctuations. In particular, these results, compared to theoretical predictions and Monte Carlo generators, will provide important details on the system size dependence of the medium response in heavy ion collisions and provide a unique opportunity to study the onset of flow from small to large systems.

Speaker: Milan Stojanovic (University of Belgrade (RS))

MStojanovic_QM2018_v3.pdf

80 SMASH - A new hadronic transport approach

Microscopic transport approaches are the tool to describe the non-equilibrium evolution in low energy collisions as well as in the late dilute stages of high energy collisions. In this talk, a newly developed hadronic transport approach, SMASH (Simulating Many Accelerated Strongly-interacting Hadrons) is introduced. After explaining all the components of this approach, e.g. initial conditions and resonance properties, the approach is validated by a comparison to an analytic solution of the Boltzmann equation. Light and strange particle production and collective flow are compared to experimental data from elementary and nucleus-nucleus collisions in the low energy regime accessible at GSI. The implications of this new approach for dilepton production are discussed including an outlook on the non-equilibrium hadronic production of electromagnetic probes at high beam energies at RHIC and LHC. In addition, the impact of resonance properties on transport coefficients of hadronic matter is pointed out. A detailed understanding of a hadron gas with vacuum properties is required to establish the baseline for the exploration of the transition to the quark-gluon plasma in heavy ion collisions at high net baryon densities.

References:
J. Weil et al, „Particle production and equilibrium properties within a new hadron transport approach for heavy-ion collisions“, Phys. Rev C 94 (2016) no. 5, 054905

J. Tindall et al, „Equilibration and freeze-out of an expanding gas in a transport approach in a Friedmann–Robertson–Walker metric“, Phys.Lett. B770 (2017) 532-538

Speaker: Hannah Petersen

Petersen_QM18.pdf

81 Measurement of Longitudinal Decorrelation of Anisotropic Flow $v_{2}$ and $v_{3}$ in 54 and 200 GeV Au+Au Collisions at STAR

The measurement of the decorrelation of flow harmonics, $v_n$, and event plane angles, $\Psi_n$, (or flow vector, $V_n\equiv v_ne^{in\Psi_n}$) in the longitudinal direction explores the non-boost-invariant nature of the initial collision geometry and final state collective dynamics. The decorrelations were first observed at the LHC, but are predicted by several (3+1)D hydrodynamic models to be stronger for lower $\sqrt{s_{NN}}$ at RHIC due to the smaller number of initial partons and shorter string length at lower $\sqrt{s_{NN}}$. We report the results from large minimum-bias Au+Au datasets at $\sqrt{s_{NN}}=$ 200 GeV (1.2 billion events) and 54 GeV (1 billion events) with the STAR detector. The factorization ratio, $r_n(\eta)=3D\langle V_n(-\eta)V_n^*(\eta_{\mathrm{ref}}) \rangle/\langle V_n(\eta)V_n^*(\eta_{\mathrm{ref}}) \rangle$, is used to measure the decorrelation between $\eta$ and $-\eta$ relative to a common reference $\eta_{\mathrm{ref}}$. Non-flow correlations are suppressed by a large rapidity gap between $\eta$ from the TPC ($|\eta|<1$) and the $\eta_{\mathrm{ref}}$ from the Forward Meson Spectrometer ($2.5<\eta_{\mathrm{ref}}<4$). The results are obtained for $v_2$ and $v_3$ as a function of transverse momentum and centrality for the two collision energies. They are compared with results from the LHC and calculations from different models. The decorrelations do not scale trivially with the beam rapidity $y_{beam}$, i.e. $r_n(\eta/y_{beam})$ from different beam energies do not overlap. Hydrodynamic models tuned to the Pb+Pb data at 2760 GeV fail to describe the strength of the decorrelation at 54 and 200 GeV. These results will help to constrain the initial condition along longitudinal direction and help to understand the longitudinal evolution of the fireball.

Speaker: Maowu Nie (Shanghai Institute of Applied Physics (SINAP))

QM2018_Maowu_final.pdf

Collectivity in small systems: II

Convener: James Lawrence Nagle (University of Colorado Boulder)

82 PHENIX Results on elliptic and triangular flow from the small-system geometry scan at 200 GeV

Using the extraordinary versatility of RHIC in selecting different colliding
species, the PHENIX experiment has collected data in p+Al, p+Au, d+Au, and $^{3}$He$+$Au at 200 GeV center-of-mass energy and conducted a comprehensive set of anisotropic flow measurements. These geometry-controlled experiments provide a unique testing ground for theoretical models that produce azimuthal particle correlations based on initial and/or final state effects.

New results that will be presented at this conference include a complete set of
triangular anisotropies of inclusive charged particles and final results on
identified pion, kaon and proton $v_2(p_T)$. The $v_3$ measurements are particularly sensitive to the initial-state fluctuations and the duration of the hot matter stage; the mass-ordered splitting in $v_2(p_T)$ provides information about the role of early-stage collective flow and late-stage hadronic rescattering. Detailed model comparisons with all observables will be discussed.

Speaker: Sylvia Irene Morrow (Vanderbilt University (US))

Morrow-PHENIX-SmallSystems-QM2018-may15.pdf

83 Long-range Collectivity in Small Collision Systems with Two- and Four-particle Correlations at STAR

Recently, near-side azimuthal angular correlations across a large pesudorapidity gap, commonly called as long-range ridge-like correlations, have been observed in small collision systems. It opens up opportunities to explore the multiparton dynamics of QCD and the limitation of fluid dynamics description of the matter created in these collisions. We report the STAR measurement of azimuthal harmonics $v_2$ and $v_3$ in the p+Au and d+Au data collected in various energies such as 19.6, 39, 62.4 and 200 GeV. The non-flow contributions, which are suppressed by requiring a large $\Delta\eta$ gap, are estimated in most peripheral collisions and subtracted. After non-flow subtraction at each beam energy, $v_2$ and $v_3$ are obtained as a function of centrality and transverse momentum. The $v_2$ signals are also extracted using four-particle azimuthal correlations, where the influence of non-flow is quantified by comparing to the standard cumulant method, as well as the two-subevent and three-subevent cumulant methods. It is found that both the influence of non-flow and the strength of the long-range $v_2$ and $v_3$ have a strong beam energy dependence. The results are compared to similar studies in peripheral Au+Au collisions and calculations from different models. This measurement provides new constraints on theoretical models of long-range collectivity and its energy dependence in small collision systems.

Speaker: Shengli Huang (Stony Brook University)

QM18-smallsystem-shengli-10.pdf

84 Measurement of four-particle cumulants and symmetric cumulants with subevent methods in small collision systems with the ATLAS detector

Measurements of four-particle flow cumulants $c_{n}\{4\}=\langle v_n^4\rangle -2\langle v_n^2\rangle^2$ for $n=2$ and 3, and symmetric cumulants $SC(n,m)=\langle v_n^2 v_m^2\rangle-\langle v_n^2\rangle\langle v_m^2\rangle$ for $(n,m)=(2,3)$ and $(2,4)$ are presented in $pp$, $p$+Pb and peripheral Pb+Pb collisions at various collision energies, aiming to probe the long-range collective nature of multi-particle production in small systems. Results are obtained using the standard cumulant method, as well as the two-subevent and three-subevent cumulant methods. Results from the standard method are found to be strongly biased by non-flow correlations as indicated by strong sensitivity to the chosen event class definition. A systematic reduction of non-flow effects is observed when using the two-subevent method and the results become independent of event class definition when the three-subevent method is used. The values of $v_n\{4\}=\sqrt[4]{-c_n\{4\}}$ are found to be constant over the range 40<$N_{ch}$<200 in $pp$ collisions, providing direct evidence that multi-particle collectivity persists to low multiplicity. The measured $SC(n,m)$ shows an anti-correlation between $v_2$ and $v_3$, and a positive correlation between $v_2$ and $v_4$. The magnitude of $SC(n,m)$ is constant with $N_{ch}$ in $pp$ collisions, but increases with $N_{ch}$ in $p$+Pb and Pb+Pb collisions. The normalized symmetric cumulants $SC(n,m)/\langle v_n^2\rangle\langle v_m^2\rangle$ are found to be independent of $p_\mathrm{T}$, suggesting $v_n$-$v_m$ correlations reflect the global properties of the event. These measurements provide further evidence for long-range multi-particle collectivity, and quantify the nature of its event-by-event fluctuations.

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

derendarz_ver10_wide.pdf

85 Long-range angular correlations of charged particles in high multiplicity e+e- collisions using archived data from the ALEPH detector at LEP

First results on two-particle angular correlations for charged particles emitted in $e^+e^-$ collisions using 730 $pb^{-1}$ of data collected between 91 and 209 GeV with the ALEPH detector at LEP are presented. With the archived data, the correlation functions are studied over a broad range of pseudorapidity $\eta$ (rapidity $y$) and azimuthal angle $\phi$ with respect to the electron-positron beam axis and the event thrust axis. Short-range correlations in $\Delta\eta$ ($\Delta y$), which are studied with $e^+e^-$ annihilations which reveal jet-like correlations. Long-range azimuthal correlations are studied differentially as a function of charged particle multiplicity. Those results are compared to event generators and are complementary to the studies of the ridge signals in high multiplicity pp, pA and AA collisions at the RHIC and the LHC.

Speaker: Yen-Jie Lee (Massachusetts Inst. of Technology (US))

20180515-ALEPH-TwoParticleCorrelation_yenjie_v6.pptx

86 Correlated azimuthal anisotropies with subevent cumulants in pp and pPb collisions with the CMS experiment

Multi-particle correlations in hadronic colliding systems at both RHIC and the LHC are under detailed investigation in recent years. A wealth of experimental evidence suggests the presence of collective phenomena and the formation of a quark-gluon plasma (QGP) also in high-multiplicity pp and pPb collisions. In particular, multi-particle cumulant analyses have established the collective nature of these correlations. Nevertheless, despite the fact that a common paradigm seems to emerge for all hadronic systems, the exact underlying mechanism still needs to be understood. In particular, the measurement of long-range collective azimuthal correlations down to low multiplicities is still challenging experimentally due to contamination from jet-like correlations. New methods of multiparticle correlations using subevents were developed to suppress jet-like correlations at low multiplicities. Based on data collected by CMS experiment in pp and pPb collisions, correlated azimuthal anisotropies ($v_n$) between different orders are studies using the symmetric cumulants without sub-event and also using N subevents (N = 2, 3 and 4). Furthermore, the subevent cumulant method is also applied to extract $v_n$ harmonics using six- and eight-particle correlations. These results provide crucial insights on the physical origin of observed long-range correlations in small colliding systems down to very low multiplicities.

Speaker: Dr Maxime Guilbaud (CERN)

QM2018_v2.pdf

87 ALICE measurements of flow coefficients and their inter-correlations in small (pp and p-Pb) and large (Xe-Xe and Pb-Pb) collision systems

Many observables which are used as a signature of collective effects in heavy-ion collisions when measured in high multiplicity pp and pA interactions reveal a very similar behaviour. We present first measurements of different order flow coefficients and their magnitude correlations using the Symmetric Cumulants for data collected by ALICE during the LHC Run 2 operation. The data sample includes pp collisions at $\sqrt{s}$ = 13 TeV, p-Pb at $\sqrt{s_{NN}}$ = 5.02 TeV, Xe-Xe at $\sqrt{s_{NN}}$ = 5.44 TeV and Pb-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV. Such a broad spectrum of colliding systems with different energies and wide range of multiplicity allow for detailed investigation of their collision dynamics. The measurements are based on the newly developed pseudorapidity-subevent technique, which was proven to be particularly important for studies in small systems. The results are compared to various theoretical models providing an important insight into initial conditions and the nature of collective phenomena in different collision systems.

Speaker: Katarina Gajdosova (University of Copenhagen (DK))

QM18_KG_v5.pdf

Initial state physics and approach to equilibrium: II

Convener: Kari J. Eskola (University of Jyvaskyla)

88 Prompt photon production in p-Pb collisions at $\sqrt{s_{NN}}=5$TeV

At very small fractional momentum of the nucleon, the increase of the gluon density is expected to saturate, but no experimental measurements have yet shown this saturation effect without ambiguity. Measurements of prompt photon production at forward rapidity in p-Pb collisions represent suitable tests for the onset of the gluon saturation.
The LHCb experiment is well suited for prompt photon measurement as it is equipped with tracking, particle identification and calorimetry detectors that cover the same pseudo-rapidity acceptance 2 < eta < 5. New results on prompt photon measurements in p-Pb collisions at $\sqrt{s_{NN}}=5$TeV will be presented.

Speaker: Thomas Julian Boettcher (Massachusetts Inst. of Technology (US))

Boettcher_QM_2018.pdf

89 Collision System Dependence of Anisotropic Flow, Flow Fluctuations and Mixed Harmonic Correlations at STAR Energies

We present new symmetric cumulant measurements, as well as two-, four- and six-particle $v_n$ measurements (and their ratios) for charged and particle identified hadrons. These measurements will be presented for a broad range of transverse momenta and centrality intervals in U+U collisions at $\sqrt{s_{NN}}$= 193 GeV and Au+Au, Cu+Au, Cu+Cu, d+Au and p+Au collisions at $\sqrt{s_{NN}}$=200 GeV. The measurements indicate the expected trends for hydrodynamic-like viscous attenuation in the medium produced in the different systems, the influence of initial-state fluctuations, system shape ($\varepsilon$), system-size and asymmetry, and the transport coefficients ($\eta/s$, $\zeta/s$, ... ) on the flow coefficients ($v_n$). The measurements are also compared to viscous hydrodynamic calculations to pin down the roles of initial-state fluctuations, mixed harmonic correlations and system size and shape ($\varepsilon$). The implication of these measurements for understanding the medium properties of these systems will be discussed.

Speaker: Niseem Abdelrahman"Magdy" (Stony Brook University)

QM_niseem_Fluctuations.pdf

90 Measurements of the photo-production of jets in ultra-peripheral heavy ion collisions with the ATLAS detector at the LHC

Ultra-peripheral heavy ion collisions occur when the nuclei have large impact parameter and interact through photon-induced reactions. These include processes in which an energetic photon emitted by one nucleus resolves the partonic structure of the other and stimulates jet production. Much like deep inelastic scattering, such processes provide a clean probe of the nuclear parton distributions. This is in contrast to other observables in ion-ion and proton-ion collisions which typically involve the convolution of parton distributions in both incident particles. Thus jet photo-production represents the most direct opportunity to study nuclear parton distributions until a future electron-ion collider is constructed. This talk presents new measurements of ultra-peripheral jet photo-production in Pb+Pb collisions with the ATLAS detector at the LHC. Events are selected using a combination of forward neutron and rapidity gap requirements. Final states with two or more jets are used to construct event level observables $H_{\mathrm{T}}$, $x_{\mathrm{A}}$ and $z_{\gamma}$, which characterize the hard scattering process. Measurements of differential cross sections in these three quantities, after unfolding for detector response, are presented. The results are compared with theoretical calculations using different nPDF parameterizatinos, which highlight the potential of this data in future global analysis for precision nPDF determination.

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

Steinberg_QM2018_final.pdf

91 Hadronic observables in small collisions systems from classical Yang-Mills dynamics + Lund string fragmentation

We present calculations of hadron production from gluon dominated non-equilibrium matter in various small collision systems using the IP-Glasma model combined with a state-of-the-art fragmentation prescription based on the Lund model. We study bulk observables such as particle spectra, nuclear modification factors (R_{pA}), proton-to-pion ratios and multi-particle azimuthal angular correlations. We demonstrate that characteristic features of hadronic observables such as the baryon to meson ratio, mass ordering of v2(pT) and <pT>, are naturally reproduced within the initial state framework [1]. We also present first results on a systematic comparison of such observables across different systems, including p+p and p+Pb collisions at the LHC as well as p/d/He3+Au at RHIC.

[1] B. Schenke, S. Schlichting, P. Tribedy, R. Venugopalan, Phys.Rev.Lett. 117 (2016) no.16, 162301

Speaker: Prithwish Tribedy (Brookhaven National Lab)

qm2018_tribedy.pdf

92 Isolated photon production in proton-nucleus collisions at forward rapidity

We calculate isolated photon production at forward rapidities in proton-nucleus collisions in the Color Glass Condensate framework [1]. Our calculation uses dipole cross sections solved from the running coupling Balitsky-Kovchegov equation with an initial condition fit to deep inelastic scattering data and extended to nuclei with an optical Glauber procedure that introduces no additional parameters beyond the basic nuclear geometry. We present predictions for future forward RHIC and LHC measurements. The predictions are also compared to updated results for the nuclear modification factors for pion production, Drell-Yan dileptons and J/Psi mesons in the same forward kinematics, consistently calculated in the same theoretical framework. We find that leading order, running coupling high energy evolution in the CGC picture leads to a significant nuclear suppression at forward rapidities. This nuclear suppression is stronger for photons than for pions. We also discuss how this might change with next-to-leading order high energy evolution.

[1] Isolated photon production in proton-nucleus collisions at forward rapidity, B. Ducloué, T. Lappi, H. Mäntysaari, arXiv:1710.02206 [hep-ph]

Speaker: Tuomas Lappi (University of Jyvaskyla)

qm18.pdf

93 Forward particle production in proton-nucleus collisions at next-to-leading order: solving the running-coupling puzzle

Reaching next-to-leading order (NLO) accuracy in perturbative calculations of particle production in QCD at high energy is essential for reliable phenomenological applications. In recent years, the Color Glass Condensate effective theory (the natural framework for such calculations) has indeed been promoted to NLO accuracy. However, the first NLO calculations met with unexpected difficulties, among which a huge scheme-dependence with respect to the scale choice in the running of the coupling. The NLO correction to the cross-section for single inclusive particle production in pA collisions at forward rapidities was found to vary by up to two orders of magnitude and also to change sign, when replacing the momentum-space prescription for the running of the coupling (as natural in the calculation of the NLO impact factor) by a coordinate-space prescription (as generally used when solving the Balitsky-Kovchegov equation).

Recently we have found out that the origin of this puzzle lies in the interplay between the Fourier transform from coordinate space to momentum space and the asymptotic freedom of QCD [1]. We present a new coordinate space prescription which avoids this problem and leads to results consistent with the momentum-space prescription ones. The NLO corrections are negative and reduce the LO result by 40% to 50%. We argue that the scheme-dependence could be further reduced by using the momentum-space representation throughout the whole NLO calculation, that is, for both the impact factor and the solution to the BK equation.

[1] "On the use of a running coupling in the NLO calculation of forward hadron production", to appear.

Speaker: Bertrand Ducloue (IPhT Saclay)

QM2018_Ducloue.pdf

Jet modifications and high-pT hadrons: II

Convener: Carlos Albert Salgado Lopez (Universidade de Santiago de Compostela (ES))

94 D-meson production in jets in pp and PbPb collisions with the CMS detector

The measurement of D-meson production in jets can provide important insights into the interactions of heavy-flavour quarks with the quark-gluon plasma created in heavy ion collisions. In particular, the role of gluon splitting processes in the production of heavy flavour, which is fundamental for a complete understanding of the quenching mechanisms for both light and heavy quarks, can be explored. Large datasets for proton-proton and PbPb collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV were collected with the CMS detector during the 2015 LHC run. These data enable measurements of D-meson production as a function of the radial distance between the jet axis and the D meson in different intervals of D-meson transverse momentum. The ratio of the results for PbPb and pp collisions will be compared to similar measurements of jet radial profiles using light particles from the CMS experiment at the same center-of-mass energy.

Speaker: Jing Wang (Massachusetts Inst. of Technology (US))

20180506_QM2018_JingWang_v5.pdf

95 Measurements of heavy-flavour correlations and jets with ALICE at the LHC

Heavy quarks (charm and beauty) are produced in hard parton scatterings in the early stages of hadronic collisions. Therefore, they are ideal probes to investigate the properties of the Quark-Gluon Plasma (QGP) produced in ultra-relativistic heavy-ion collisions. The study of angular correlations between heavy-flavour particles and charged particles allows us to characterize the heavy-quark fragmentation process and its possible modification in a hot and dense medium. The measurement of heavy-flavour jets gives more direct access to the initial parton kinematics and can provide further constraints for heavy-quark energy-loss models, in particular adding information on how the radiated energy is dissipated in the medium.

Studies in pp collisions are mandatory to characterize heavy-quark production and fragmentation in vacuum, constituting the necessary reference for interpreting heavy-ion collision results. Differences between results from pp and p-Pb collisions can reflect how the heavy-quark production and hadronization into jets is affected by cold nuclear matter effects.

This contribution will include the latest heavy-flavour correlation and jet measurements with the ALICE detector in pp, p-Pb and Pb-Pb collisions from the LHC Run-2 data. In particular, results on azimuthal correlations of D mesons with charged particles in p-Pb collisions at $\sqrt{{s}_{\rm{NN}}} = 5.02$ TeV will be presented. Measurements of multiplicity and centrality dependent azimuthal correlations of heavy-flavour hadron decay electrons with charged particles in p-Pb and Pb-Pb collisions at $\sqrt{{s}_{\rm{NN}}} = 5.02$ TeV will be shown. In addition, measurements of D-meson tagged and beauty tagged jet production in pp collisions at $\sqrt{s} = 7$ TeV and p-Pb collisions at $\sqrt{{s}_{\rm{NN}}} = 5.02$ TeV will be presented. The status of D-tagged jet measurements in Pb-Pb collisions at $\sqrt{{s}_{\rm{NN}}} = 5.02$ TeV will be discussed.

Speaker: Barbara Antonina Trzeciak (Utrecht University)

ALICEHFCorrJets_BTrzeciak_QM18_final.pdf

96 Probing jet splitting and energy loss via groomed jets in relativistic heavy-ion collisions

The nuclear modification of groomed jet splitting in relativistic heavy-ion collisions at RHIC and the LHC energies is studied [1] based on the higher twist formalism. Assuming coherent energy loss for the two splitted subjets, a non-monotonic jet energy dependence is found for the nuclear modification of jet splitting function: strongest modification at intermediate jet energies whereas weaker modification for larger or smaller jet energies. Combined with the smaller size and lower density of the QGP medium at RHIC than at the LHC, this helps to understand the groomed jet measurements from CMS and STAR Collaborations: strong modification of the momentum sharing $z_g$ distribution at the LHC whereas no obvious modification of the $z_g$ distribution at RHIC. In contrast, the observed nuclear modification pattern of the groomed jet $z_g$ distribution cannot be explained solely by independent energy loss of the two subjets. The dependence on the angular separation $\Delta R$ between two subjets is also studied; it is found that the nuclear modification of $z_g$ distribution decreases with decreasing $\Delta R$ but the maximal nuclear modification from CMS energies is always roughly twice of that for STAR energies. Our result may be tested in future groomed jets measurements with lower jet energies at the LHC and larger jet energies at RHIC, for different angular separations between the two subjets.

Reference:

[1] Ning-Bo Chang, Shanshan Cao, Guang-You Qin, arXiv:1707.03767 [hep-ph].

Speaker: Dr Ning-Bo Chang (Xinyang Normal University)

Changnb_jet-splitting.pdf

Changnb_jet-splitting.pptx

97 Studies of jet grooming and recursive splittings in pp and PbPb collisions with ALICE

Hard splittings in the evolution of a jet may be modified by the presence of a dense strongly interacting medium. Grooming procedures can be used to isolate such hard components of a jet and allows one to focus on the two subjets resulting from a sufficiently hard partonic splitting. The modification of these splittings in medium could highlight the role of jet induced medium response as well as potential single hard scatterings (higher-twist) and multiple soft medium induced radiation (BDMPS).
Measurements of the symmetry parameter ($z_g$) and angular separation of such subjets are reported as measured with the ALICE Detector in pp and PbPb collisions at $\sqrt{s} = 7$ TeV and $\sqrt{s_{NN}} = 2.76$ TeV respectively. Results are compared to predictions using Monte Carlo generators. The use of recursive splittings and their mappings to identify interesting regions of phase space will also be discussed with comparisons made between Monte Carlo generators and data in pp and PbPb collisions.

Speaker: Harry Arthur Andrews (University of Birmingham (GB))

HarryAndrews_QuarkMatter18Final.pdf

98 Identification of heavy quark antennae using groomed jet substructure

Nearly collinear pairs of partons are sensitive to potential novel coherence effects in the parton energy loss process, which can be observed through measurements of jet substructure. This analysis presents a new measurement of jets containing a gluon that splits into a heavy quark pair, i.e., a heavy-quark antenna. Such jets are identified by analyzing the groomed substructure of double b-tagged jets. The grooming procedure allows the identification of the hardest splitting process within the parton shower and is sensitive to the virtuality evolution of the parton. Results of the subjet transverse momentum balance and angular distance between the two subjets are shown in pp collisions at 5.02 TeV, which are the first jet substructure measurements of identified partons.

Speaker: Kurt Eduard Jung (University of Illinois at Chicago (US))

qm2018_kjung_doubleBTag_180515.pdf

99 Jet fragmentation and shapes for inclusive, b-tagged, and photon-tagged jets in pp and PbPb collisions with the CMS detector

Correlations of electroweak probes, jets, and charged particles are a powerful tool to study medium modifications of the parton shower. One can impose constraints on jet quenching mechanisms in heavy ion collisions by measuring jet substructure observables, such as fragmentation functions or jet momentum density profiles. Tagging jets with an associated photon helps to constrain the associated parton kinematics and flavor before quenching. Additionaly, parton flavor dependence of these observables can be explored by comparing the results for the inclusive jet sample, which is dominated by gluon-induced jets, to one with a b-tagged jet-selection. Measurements of photon-tagged jet fragmentation functions and the jet shapes for inclusive, b-tagged, and ,for the first time, photon-tagged jet sample in pp and PbPb collisions at sqrt(s_NN) = 5.02 TeV collision energy using data collected by CMS will be reported. Besides, the corresponding measurements for inclusive and b-tagged jets will be shown in context of parton flavor dependence.

Speaker: Kaya Tatar (Massachusetts Inst. of Technology (US))

180515_QM2018_KayaTatar.pdf

Quarkonia: II

Convener: Ramona Vogt (LLNL)

100 Upsilon Measurements in Au+Au Collisions at √sNN = 200 GeV with the STAR Experiment

Measurements of quarkonium production play an important role in understanding the properties of the Quark-Gluon Plasma (QGP) created in relativistic heavy-ion collisions. Quarkonium suppression in the medium due to the color screening effect has been proposed as a direct signature of the QGP formation. However, other effects, such as cold nuclear matter (CNM) effects and regeneration, add additional complications to the interpretation of the observed suppression. Compared to charmonia, bottomonia not only gain less contribution from regeneration due to the smaller b-quark production cross-section, but are also less affected by the CNM effects. Furthermore, different bottomonium states with different binding energies are expected to dissociate at different temperatures, thus measurement of this "sequential melting" can help constrain the thermodynamic properties of the medium.

In this talk, we will present the latest measurements of $\Upsilon$ production in Au+Au collisions at $\sqrt{s_{\scriptsize\mbox{NN}}}$ = 200 GeV via both di-muon and di-electron channels by the STAR experiment. With combination of the data sets taken in 2011, 2014 and 2016, the precision of $\Upsilon$ measurements will be significantly improved compared to previous preliminary results, especially for the excited $\Upsilon$ states. The nuclear modification factors for the ground and excited $\Upsilon$ states will be shown as a function of transverse momentum and centrality, and compared to those measured at the LHC as well as to theoretical calculations.

Speaker: Pengfei Wang (University of Science and Technology of China and Brookhaven National Laboratory)

Upsilon_draft_QM2018v13.pdf

101 Probing QCD deconfinement with sequential quarkonium suppression of three $\Upsilon(nS)$ states with the CMS detector

The production cross sections of the $\Upsilon(1S)$, $\Upsilon(2S)$, and $\Upsilon(3S)$ states were measured separately using the CMS experimental apparatus, in pp, pPb, and PbPb collisions at 5.02 TeV. New results on the production of the three upsilon states in pPb are reported, including cross sections as a function of transverse momentum (p$_T$) and rapidity ($y$). The data show a stronger suppression of the excited states (2S and 3S) as compared to the ground state (1S). The event activity dependence of the forward-backward ratio of all three upsilon states is also reported. Final results on the differential production cross section and nuclear modification factor of upsilon mesons in PbPb collisions at 5.02 TeV, as a function of centrality, p$_T$ and $y$, show similar suppression pattern, more pronounced than in pPb data. A strong suppression is observed in PbPb collisions, by up to a factor of 2 and 10 for the $\Upsilon(1S)$ and $\Upsilon(2S)$ respectively. The $\Upsilon(3S)$ was not observed in PbPb collisions, being suppressed by more than a factor 14 at the 95% confidence level.

Speaker: Ms Santona Tuli (University of California Davis (US))

QM18_SantonaTuli.pdf

102 Bottomonium suppression at RHIC and LHC

Bottomonium suppression has long been discussed as a probe for the quark-gluon plasma generated in ultra-relativistic heavy ion collisions. The use of a realistic hydrodynamic background which is anisotropic in momentum space has shown to reproduce experimental data for various windows across each experiment. We have recently expanded our model to incorporate a realistic lattice-vetted heavy-quark potential and have implemented a regeneration model. We present bottomonia suppression results for RHIC and CMS collisions with this new potential and regeneration model.

Speaker: Brandon Krouppa (Kent State University)

krouppa-QM2018.pdf

103 Quarkonium tomography of heavy ion collisions at the LHC

Quarkonium production in high-energy hadronic collisions provides a fundamental test of QCD. Its modification in a nuclear medium is a sensitive probe of the space-time temperature profile and transport properties of the QGP, yielding constraints complementary to the ones obtained form the quenching of light and heavy flavor. We will present new results for the suppression of high transverse momentum charmonium [$J/\psi, \psi(2S)$] and bottomonium [$\Upsilon(1S),\Upsilon(2S),\Upsilon(3S)$] states in Pb+Pb collisions at the Large Hadron Collider. Our theoretical formalism combines the collisional dissociation of quarkonia, as they propagate in the quark-gluon plasma, with the thermal wavefunction effects due to the screening of the $Q\bar{Q}$ attractive potential in the medium. We find that a good description of the relative suppression of the ground and higher excited quarkonium states, transverse momentum and centrality distributions is achieved, when comparison to measurements at a center-of-mass energy of 2.76 TeV is performed. Theoretical predictions for the highest Pb+Pb center-of-mass energy of 5.02 TeV at the LHC, where new experimental results are being finalized, will also presented. Finally, we will show the latest theoretical calculations at forward rapidity and in smaller systems, such as Xe+Xe.

Speaker: Dr Ivan Vitev (Los Alamos National Laboratory)

QM2018_Vitev.pdf

104 Realistic in-medium heavy-quark potential from high statistics lattice QCD simulations

The heavy-quark potential is a highly versatile theoretical tool. It allows one to summarize many aspects of the intricate interactions between a QQbar bound state and its surrounding medium in a single complex valued quantity. It is systematically defined from QCD [1,2] and at the same time provides an intuitive understanding of the physics of in-medium quarkonium modification. I.e. it offers the means to investigate from first principles how e.g. color screening and collisional excitations conspire to lead to quarkonium suppression in heavy-ion collisions [3,4].

Here we present the first direct computation of this potential from realistic lattice QCD simulations with near physical pion masses [5]. Current ensembles with $N_\tau=12$ from the TUMQCD collaboration offer unprecedented high statistics, those with $N_\tau=16$ unprecedented time resolution, making possible a robust extraction of its values from the spectral functions of Wilson line correlators. To this end we deploy a combination of Bayesian reconstruction methods (BR), as well as the Pade approximation, in turn diminishing individual method artifacts.

Re[V] shows a smooth transition from a confining to a Debye screened behavior. At all temperatures its values lie close to the color singlet free energies. Based on Re[V] we estimate the Debye mass. The modification of Im[V] at very high temperatures is compared to predictions of hard-thermal-loop perturbation theory.

Applications of the complex potential in the modeling of charmonium and bottomonium in heavy-ion collisions are briefly touched upon ([3,4,6]).

[1] N. Brambilla, J. Ghiglieri, A. Vario and P. Petreczky PRD78 (2008) 014017
[2] A.R., T. Hatsuda, S. Sasaki PRL 108 (2012) 162001
[3] Y. Burnier, O. Kaczmarek, A.R. JHEP 1512 (2015) 101
[4] N. Brambilla, M. Escobedo, J. Soto, A. Vairo PRD96 (2017) 034021
[5] A.R. & TUMQCD collaboration (in preparation)
[6] B. Krouppa, M. Strickland, A.R. arXiv:1710.02319

Speaker: Alexander Rothkopf (Heidelberg University)

QM2018_ROTHKOPF_EXPORT.pdf

105 Heavy Flavour production measurements in proton-lead and fixed target collisions at LHCb

New results on quarkonia production in proton-lead collisions at LHCb at 8.16 TeV nucleon-nucleon center-of-mass energy will be presented. Measurements include J/psi and psi', where the prompt and from-b-decay components can be disentangled, and the 1-- bottomonia states. The large data sample allows the determination of nuclear modification factors with high accuracy.
LHCb has the unique capability to study collisions of the LHC beams on fixed targets. Internal gas targets of helium, neon and argon have been used so far. Updated results and prospects on open and hidden charm productions will be presented, which can provide crucial constraints on cold nuclear matter effects and nPDF at large x. These measurements, together with production of antiprotons and other light hadrons, are of great interest to cosmic ray physics.

Speaker: Shanzhen Chen (Universita e INFN, Cagliari (IT))

Shanzhen_15_5_2018_QM.pdf

13:10 Lunch

Collectivity in small systems: III

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

106 Multiplicity dependence of azimuthal particle correlations as a probe of collectivity in deep inelastic electron-proton collisions at HERA

Recent observations at RHIC and the LHC of two- and multi-particle correlations
in high multiplicity relativistic proton-proton and proton-ion collisions and similarity of the results to those observed in central heavy-ion collisions are often interpreted as an evidence for collective particle production in small collision systems. These results motivate a study in even smaller systems, such as produced in relativistic electron-proton collisions.

A measurement is presented of two-particle correlations in collisions of electron beams at 27.5 GeV with beams of protons at 920 GeV, which corresponds to 318 GeV centre-of-mass energy. A sample of events equivalent to the integrated luminosity of 430 pb$^{-1}$ was recorded with the ZEUS experiment in 2003-2007. The correlations are measured for charged hadrons as a function of event multiplicity for the lab pseudorapidity range $-1.5<\eta_{\rm lab}<2$. To probe the possible contribution due to collective effects, the correlations are studied as a function of the particle's pair separation in pseudorapidity and the pair mean transverse momentum. The observed correlations are compared to available Monte Carlo models of deep inelastic electron-proton scattering. Observations based on the analysis of the ZEUS data put a limit on the possible collective effects in high multiplicity electron-proton collisions.

Speaker: Jacobus Onderwaater (Ruprecht Karls Universitaet Heidelberg (DE))

ZEUS.pdf

107 Importance of initial and final state effects for azimuthal correlations in p+Pb collisions

We investigate the relative importance of initial and final state effects on azimuthal correlations in low and high multiplicity p+Pb collisions at LHC energies. By matching the classical Yang-Mills dynamics of pre-equilibrium gluon fields (IP-GLASMA) to a perturbative QCD based parton cascade for the final state evolution (BAMPS) on an event-by-event basis, we find that signatures of both the initial state correlations and final state interactions are seen in azimuthal correlation observables, such as $v_2\{2P C\}(p_T)$, with their relative strength depending on the event multiplicity and transverse momentum. Initial state correlations dominate elliptic flow in low multiplicity events for transverse momenta $p_T > 2~\mathrm{GeV}$. While final state interactions are dominant in high multiplicity events and at low momenta, we find that initial state correlations strongly affect $v_2\{2P C\}(p_T)$ for $p_T>2$ GeV as well as the pT integrated $v_2\{2P C\}$. By carrying out a systematic multiplicity scan, we can also probe the dynamics on the border of initial state dominated to final state dominated - but not yet fully developed hydrodynamic – regime. We predict at which multiplicity and transverse momentum many-body QCD effects in the initial state can be experimentally unveiled.

Reference: Greif, Greiner, Schenke, Schlichting, Xu: Phys. Rev. D 96, 091504, 2017

Speaker: Moritz Greif (University of Frankfurt)

NO_VIDEO_PDF_QM2018_Moritz_Greif_Initial_and_Final_State.pdf

QM2018_Moritz_Greif_Initial_and_Final_State.pptx

108 Multi-particle correlations and collectivity in $pA$ collisions from an initial state parton model

We report on recent progress in understanding multi-particle correlations in $pA$ collisions from the initial state. We consider a proof of principle model of eikonal quarks from the projectile proton multiple-scattering off of a dense nuclear target. With this model, we find that many of the features observed in light-heavy ion collisions at RHIC and the LHC which are often ascribed to collectivity can be qualitatively reproduced in an initial state model. These include the ordering of the two-particle azimuthal angle n-th Fourier harmonics, $v_n\{2\}$; a negative four-particle second Fourier cumulant $c_2\{4\}$, giving rise to a real $v_2\{4\}$; the energy and transverse momentum dependence of $v_2\{4\}$; the similarity in multi-particle second Fourier harmonics $v_2\{4\} \approx v_2\{6\} \approx v_2\{8\}$; and the energy dependence of the four-particle symmetric cumulants. Finally, we consider the Glasma graph approximation of our model and find that many of these features cannot be reproduced, leading to the conclusion that multiple-scattering is a key ingredient for the observed multi-particle correlations from the initial state.

[1] K. Dusling, M. Mace, R. Venugopalan. Multiparticle collectivity from initial state correlations in high energy proton-nucleus collisions. arXiv:1705.00745 [hep-ph]
[2] K. Dusling, M. Mace, R. Venugopalan. Parton model description of multiparticle azimuthal correlations in pA collisions. arXiv:1706.06260 [hep-ph]

Speaker: Mark Mace (Stony Brook University)

QM_051518_MACE_16x9.pdf

109 Measurement of long-range correlations in $pp$ collisions characterized by presence of a Z boson with the ATLAS detector

Recent measurements of correlations between two particles separated in pseudorapidity and azimuthal angles have shown striking similarities between results obtained in $pp$, $p$+A and A+A collision systems. In the $pp$ collision system, unlike in $p$+A and A+A collisions, the strength of the correlations, quantified by the anisotropy parameter $v_2$, shows little dependence on the observed charged-particle multiplicity. Recent theoretical models suggest that this can result from an intrinsically weak correlation between the charged-particle multiplicity and the impact parameter of the $pp$ collision. An independent handle on the impact parameter can be obtained in principle by requiring the presence of a hard-scattering process in the collision. This talk presents the first measurement of two-particle correlations in $pp$ collisions with a presence of Z boson identified via its $\mu\mu$ decay channel. The analysis uses ATLAS data recorded with nominal $pp$ luminosity with high pileup. A new procedure is used to correct for the contribution of tracks arising from pileup vertices. The multiplicity and transverse momentum dependence of the inclusive charged-particle $v_2$ measured in Z-tagged events at $\sqrt{s}=8$ and 13 TeV is compared to the $v_2$ measured in minimum-bias collisions. They are found to be of a similar magnitude.

Speaker: Brian Cole (Columbia University (US))

RidgeZTaggedppQM2018_v3.pdf

110 Microscopic collectivity: The ridge and strangeness enhancement from string-string interactions in Pythia8

The observation of collective effects in small systems, such as strangeness enhancement and the appearance of a ridge, have posed a challenge to conventional models for multiparton interactions and hadronization underlying general purpose MC event generators.
In this talk I will present the microscopic model for collective effects recently implemented in the Pythia8 and DIPSY event generators. In this model collectivity is generated from interactions between Lund strings, referred to as “string shoving” and “rope hadronization”. Rope hadronization is shown to give a good description of strangeness enhancement across pp, pA and AA collisions systems, while string shoving qualitatively describes the ridge observed in pp collisions.
A defining feature of the microscopic model is that all effects are generated without assuming a deconfined plasma or thermalization. Ongoing efforts aim towards further extending the models to pA and AA.

Speaker: Christian Bierlich (Lund University (SE))

cbierlich.pdf

111 Estimating nucleon substructure properties in a unified hydrodynamic model of p+Pb and Pb+Pb collisions

Simulations of relativistic heavy-ion collisions based on viscous hydrodynamics provide an accurate description of the bulk observables measured at RHIC and LHC beam energies, including identified particle yields, mean $p_T$ and multiparticle correlations. The success of the hydrodynamic framework, however, is naturally expected to break down in the dilute limit where discrete particle degrees of freedom dominate.

It was thus surprising when the multiparticle correlations measured in high-multiplicity proton-lead collisions were found to be similar in magnitude to those observed in lead-lead collisions. The observation suggests that hydrodynamic behavior could be manifest in small droplets of quark-gluon plasma (QGP), and that flow might develop at length scales smaller than a proton.

In this work, we posit the existence of hydrodynamic flow in small collision systems and evaluate the likelihood of our assertion using Bayesian inference. Specifically, we model the dynamics of proton-lead and lead-lead collisions at $\sqrt{s_{NN}}=5.02$ TeV using QGP initial conditions with parametric nucleon substructure, a pre-equilibrium free-streaming stage, event-by-event viscous hydrodynamics, and a microscopic hadronic afterburner.

Bayesian parameter estimation is used to construct the posterior probability distribution for the model's input parameters, calibrated to fit the charged particle yields, meant $p_T$ and flow cumulants of both collision systems. We then sample preferred regions of parameter space and evaluate the performance of the model using optimally chosen parameter values. This semi-exhaustive model validation enables us to to comment on the implied viability of hydrodynamics in small collision systems subject to the approximations of the chosen framework. We conclude by presenting posterior constraints on the shape of the proton and temperature dependence of QGP transport coefficients, and discuss relevant implications for hot and dense nuclear matter.

Speaker: Scott Moreland (Duke University)

qm2018.pdf

qm2018_updated.pdf

112 Event-shape, multiplicity-, and energy-dependent production of (un)identified particles in pp collisions with ALICE at the LHC

The multiplicity dependent results of identified particle production allowed the discovery of collective-like behavior in pp collisions at the LHC. Good understanding of the effects attributed to well-understood physics, like multiple hard scatterings, is required to establish the origin of the new phenomena. Experimentally, those effects can be controlled using event shapes, like transverse spherocity or directivity, which allows the classification of the pp collisions either as jetty-like or isotropic events. The transverse momentum ($p_{\rm T}$) spectra of light-flavor hadrons in pp collisions measured over a broad $p_{\rm T}$ range provide important input to study particle production mechanisms in the soft and hard scattering regime of QCD. In this work, they are used to perform a comprehensive study as a function of the event multiplicity, collision energy, and event shapes.

We will present the inclusive charged particle transverse momentum distributions for pp collisions at different center-of-mass energies. The multiplicity and energy dependencies of the particle production at high transverse momentum are studied with the exponent of the power law function which describes the $p_{\rm{T}}$ spectra. For pp collisions at
$\sqrt{s} = 13$ TeV and for a fixed multiplicity interval, the parameters obtained from the blast wave analysis of the $p_{\rm T}$ spectra are used to characterize the evolution of the spectral shapes for different event topologies. The multiplicity and spherocity dependencies of the average transverse momenta and integrated yields as a function of charged-particle multiplicity are discussed. The proton-to-pion and kaon-to-pion particle ratios as a function of $p_{\rm T}$ are also reported. Comparisons between data and QCD-inspired models will be shown.

Speaker: Gyula Bencedi (Hungarian Academy of Sciences (HU))

Bencedi_QM18_15052018_v4.pdf

Correlations and fluctuations: II

Convener: Frederique Grassi

113 Hydrodynamic fluctuations in relativistic heavy-ion collisions

We present a novel approach to the treatment of thermal fluctuations in the (3+1)-D viscous hydrodynamic simulation MUSIC. We investigate the phenomenological impact of thermal fluctuations on hadronic and electromagnetic observables using the state-of-the-art IP-Glasma + hydrodynamics + hadronic cascade hybrid approach [1]. In particular, we show that these thermal fluctuations influence the result of elliptic and triangular flow measurements for ultra-central collisions, such as those presented by the CMS Collaboration [2]. Consequences on the extraction of QCD transport coefficients from heavy-ion collisions will also be discussed.

The anisotropic flow observed in heavy-ion collision experiments is mostly attributed to the hydrodynamic response to the event-by-event collision geometry and to the sub-nucleon quantum fluctuations. However, hydrodynamic fluctuations are present during the dynamical evolution of the Quark Gluon Plasma (QGP) and are quantified by the fluctuation-dissipation theorem [3]. They can leave their imprint on final-state observables.

By analyzing the thermal noise mode-by-mode, we provide a consistent scheme of treating these fluctuations as the source terms for hydrodynamic fields. These source terms are then evolved together with hydrodynamic equations of motion. Such a treatment captures the non-perturbative nature of the evolution for these thermal fluctuations.

[1] McDonald, S., Shen, C., Fillion-Gourdeau, F., Jeon, S. and Gale, C., Phys. Rev. C 95, 064913 (2017).

[2] The CMS collaboration, Chatrchyan, S., et al., JHEP (2014) 2014:88.

[3] Kapusta, J. I., Müller, B. and Stephanov, M., Phys. Rev. C 85, 054906 (2012).

Speaker: Mayank Singh (McGill University)

QuarkMatter_2018 _updated.pdf

114 Transverse and longitudinal event-by-event flow fluctuations of $v_1 - v_4$ in 2.76 and 5.02 TeV Pb+Pb collisions with the ATLAS detector

Multi-particle flow correlations in Pb+Pb collisions provide unique insight into the nature of event-by-event fluctuations of the initial eccentricity as well as final state dynamics in the transverse and longitudinal directions. This talk presents a detailed study of transverse flow fluctuations using 4 and 6-particle cumulants $v_n\{4\}$ and $v_n\{6\}$ for $n=1, 2, 3$, and 4. This includes several new results: the first measurement of a negative dipolar flow $v_{1}\{4\}$; a high-precision measurement of $v_{4}\{4\}$, changing sign around 20-25$\%$ centrality; observation of an intriguing sign-change pattern of $v_2\{4\}$ and $v_2\{6\}$ in ultra-central collisions; a detailed study of the cumulant ratio $v_n\{4\}/v_n\{6\}$ which shows significant deviation of $v_2$ and $v_3$ from both Bessel-Gaussian and elliptic-power distributions. The three-subevent cumulant method is used to show that these results are unlikely to be due to non-flow effects. The talk also presents a detailed study of the longitudinal dynamics of harmonic flow using various correlators involving two, four or six particles. The flow decorrelations for $v_n$ ($n=2, 3$, and 4), as well as their center-of-mass energy dependence are studied over broad range of pseudorapidity ($|\eta|<2.5$) and transverse momentum (0.5<$p_\mathrm{T}$<5 GeV). The decorrelation signals are decomposed into contributions from the forward-backward twist and asymmetry in the flow angle and magnitude, respectively. Furthermore, the decorrelation between $v_n$ and $v_m$ in different $\eta$ is measured to disentangle the longitudinal dependence of the initial-state linear effects and final-state non-linear mode-mixing effects. These results provide a wealth of differential information on event-by-event fluctuations of harmonic flow in both transverse and longitudinal directions, and they can be used to improve event-by-event 3+1D hydrodynamic models.

Speaker: Mingliang Zhou (Stony brook Universty (US))

ATLAS_cumulant_MingliangZhou_QM18.pdf

115 Longitudinal fluctuations of anisotropic flows and flow correlations

In relativistic heavy-ion collisions, event-by-event fluctuations in the transverse plane in the initial states of quark-gluon plasma (QGP) could lead to anisotropic flows of the final hardons, which has been successfully described by relativistic hydrodynamics simulation. On the other hand, the initial states fluctuations in the longitudinal direction could lead to the fluctuations and decorrelations (factorization breaking) of anisotropy flows in the pseudorapidity direction [See e.g., 1, 2]. Detailed study of initial state fluctuations and their manifestations in the final-state flows and flow correlations can provide insights into the initial states and dynamical evolution of the hot and dense QGP.

In this work [3], we perform a detailed analysis on initial-state longitudinal fluctuations, the pseudorapidity dependence of anisotropic flows and the longitudinal decorrelations of anisotropic flows in heavy-ion collisions at RHIC and the LHC. The dynamical evolution of the QGP is simulated via a (3+1)-dimensional hydrodynamics model [4]. To study the dependence on initial conditions, we utilize two initial condition models: the AMPT model and a Monte-Carlo Glauber based model with longitudinal fluctuations. For longitudinal fluctuations and decorrelations, the individual contributions from flow magnitudes and flow angles are investigated. The comparison to the ALICE, ATLAS and CMS data is also performed. We also study the correlations among anisotropic flows of different orders, such as flow angle correlations and symmetric cumulants. The pseudorapidity dependence of flow correlations is studied as well.

[1] Long-Gang Pang, Guang-You Qin, Victor Roy, Xin-Nian Wang, Guo-Liang Ma, Phys.Rev. C91 (2015) no.4, 044904.

[2] Long-Gang Pang, Hannah Petersen, Guang-You Qin, Victor Roy, Xin-Nian Wang, Eur.Phys.J. A52 (2016) no.4, 97.

[3] X.-Y. Wu, L.-G. Pang, G.-Y. Qin， X.-N. Wang, in preparation.

[4] Longgang Pang, Qun Wang, Xin-Nian Wang, Phys.Rev. C86 (2012) 024911.

Speaker: Xiang-Yu Wu (Central China Normal University.)

ld_qm2018.pdf

116 PHENIX Measurements of collectivity in $Au+Au$ collisions from higher order cumulants and flow unfolding

Detailed measurements of collectivity in Au+Au collisions at RHIC provide a key
connection between the initial geometry of the deposited energy and the
hydrodynamic evolution of the medium. Utilizing the PHENIX silicon detectors, we present new measurements of flow coefficients extending over a wide range in pseudorapidity $-3 < \eta < 3 $ and to higher $p_T$. Over a broad range in centrality, we present cumulant results $v_2\{2\}$ - $v_2\{8\}$ and $v_3\{2\}$ - $v_3\{6\}$ with different methods for isolating flow and non-flow contributions. Complementing these results, we present flow coefficient unfolded distributions and compare them directly with theoretical models with event-by-event fluctuations. We also present a first look at symmetric cumulants of different orders.

Speaker: Kurt Keys Hill (University of Colorado Boulder (US))

kurthill_qm2018_AuAuflow_20180519.pdf

117 New measures of longitudinal decorrelation of harmonic flow

Longitudinal harmonic flow decorrelation (the "torque" effect [1,2]) is a sensitive probe of the early dynamics of ultra-relativistic nuclear collisions. We propose new decorrelation measures of flow magnitude and event-plane angles and apply them to Pb+Pb collisions at the LHC, modeled via event-by-event hydrodynamic simulations. The basic purpose is to verify a generic feature, namely, that the events with a higher flow magnitude decorrelate significantly less in the event-plane angle, compared to the events with a lower flow magnitude. We find a hierarchy between various flow decorrelation measures and confirm specific factorization relations. The model results are in qualitative agreement with the experimental data from the ATLAS and CMS Collaborations. The proposed generalization of the flow decorrelation measures, with weights involving higher powers of the flow magnitude, can be directly tested in future experimental analyses.

[1] P. Bozek, W. Broniowski, J. Moreira, Phys.Rev. C83 (2011) 034911
[2] P. Bozek, W. Broniowski, arXiv:1711.03325 [nucl-th]

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

longcorr.pdf

118 Rapidity decorrelation from hydrodynamic fluctuations

Fluctuations have been playing an important role in understanding observables in high-energy nuclear collisions. Higher harmonics of azimuthal angle distributions, for example, can be attributed to initial fluctuations of transverse profile from event to event. In this presentation, we focus on thermal fluctuations during hydrodynamic evolution (a.k.a. hydrodynamic fluctuations) of the QGP fluids in the intermediate stage and investigate the effects of them on several observables in high-energy nuclear collisions.

We employ an integrated dynamical model [2,3] which combines full three-dimensional relativistic fluctuating hydrodynamics with Monte-Carlo version of the Glauber model for event-by-event initialization and the hadronic cascade model in the late rescattering stage. By using this model, we first adjust initial parameters and transport coefficients to reproduce $dN_{\mathrm {ch}}/d\eta$ and centrality dependence of integrated $v_{2}$ in Pb+Pb collisions at the LHC energy. We next analyze %$r_{n|n;1}(\eta)$ and observables for longitudinal flow correlations of the $n$-th order higher harmonics $R_{n;n|n;n}(\eta)$ [4] for separation of the flow magnitude fluctuations from the event-plane twist along the rapidity. From this analysis, we see how hydrodynamic fluctuations break up longitudinal correlations of the magnitude and the event-plane angle of anisotropic flow parameters.

References
[1] K.~Murase and T.~Hirano, Relativistic fluctuating hydrodynamics with memory functions and colored noises,'' arXiv:1304.3243 [nucl-th]. [2] Koichi Murase,Causal hydrodynamic fluctuations and their effects on high-energy nuclear collisions'', Ph.~D thesis, the University of Tokyo (2015).
[3] K.~Murase and T.~Hirano, Hydrodynamic fluctuations and dissipation in an integrated dynamical model'', arXiv: 1601.02260 [nucl-th]. [4] Jiangyong Jia \textit{et al.}, Observables for longitudinal flow correlations in heavy-ion collisions'', arXiv:1701.02183 [nucl-th].

Speaker: Azumi Sakai

QM 2018 slides.pdf

119 Event Plane Dependence of Di-hadron Correlations with Event Shape Engineering at the STAR Experiment

In relativistic high energy collisions, hard scattered partons can fragment into two back-to-back jets. These jets can be used as hard probes to study properties of the Quark Gluon Plasma created in nucleus-nucleus collisions. Di-hadron correlations with respect to high $p_T$ trigger particles are a useful tool to study the interactions between jets and the medium in high-energy heavy-ion collisions. The jet-medium interplay depends on the in-medium path length of initial partons and the system evolution.

Centrality dependence of the jet-like recoil peak magnitude opposite the trigger particle in di-hadron correlations has been widely interpreted as a signature of path-length dependence of jet modification. However, the path length differs between in-plane (the same direction as the event plane, the shorter axis of elliptic shape) and out-of-plane (the perpendicular direction to the event plane) trigger particles because of the almond-like shape of two overlapping nuclei. Therefore, one can exert a measure of control over the recoil jet's in-medium path length by selecting the trigger particle's azimuthal direction with respect to the event plane. Event shape engineering (ESE) has been proposed as a powerful tool to control the initial geometrical shape. ESE constrains the event-by-event flow fluctuations by selecting the magnitude of the flow vector $q_n$. A more detailed study for jet-medium interplay will be possible with ESE than previous event plane dependent di-hadron correlations at the STAR experiment. Here, we present di-hadron correlations in Au+Au collisions at $\sqrt{s_{NN}}=$200 GeV as a function of both the trigger azimuthal angle with respect to the event plane and various ESE selections. The result of this analysis will provide new insights on the geometry and path-length dependence of jet-medium interactions as well as the effect of collective medium expansion on jet modification.

Speaker: Ryo Aoyama (University of Tsukuba)

raoyama_QM2018_final.pdf

High baryon density and astrophysics: I

Convener: Dirk Rischke (University Frankfurt)

120 Neutron stars meet constrains from high and low energy nuclear physics

A novel equation of state with the surface tension induced by particles’ interactions was generalized to describe the properties of the neutron stars. In this equation the interaction between particles occurs via the hard core repulsion by taking into account the proper volumes of particles. Recently, this model was successfully applied to the description of the properties of nuclear and hadron matter created in collisions of nucleons.
The new approach is free of causality problems and is fully thermodynamically consistent, which enables us to use it for the investigation of the strongly interacting matter phase-diagram properties in a wide range of temperatures and baryon densities, including neutron stars. The considered model with a small number of parameters, fully determined according to the experimental constraints, reproduces very well all the known properties of normal nuclear matter, provides a high quality description of the proton flow constraints, hadron multiplicities created during the nuclear-nuclear collision experiments and equally is consistent with astrophysical data coming from neutron star observations. Accordingly, we found parameter values that are in good agreement with the same ones obtained from the nuclear–nuclear collision data analysis.

Speaker: Dr Violetta Sagun (Centro Multidisciplinar de Astrofisica/BITP)

Sagun_QM.pdf

121 Modeling hybrid stars and hot matter

The recent spectacular observation of neutron star mergers underlines the importance of developing strong interaction models that can cover the whole range of densities and temperatures, which can be reached in compact stars as well as heavy-ion collisions. As the temperatures in the merger might reach 80 MeV or more, these events connect conditions of compact star physics and of the fireball created in a heavy-ion collision.
To this end we present a newly developed unified flavour SU(3) description of the hadronic and quark matter based on the parity-doublet description of chiral symmetry breaking. We adjust the parameters to describe nuclear ground state isospin symmetric as well as asymmetric matter, and properties of finite nuclei. In addition, lattice results for thermodynamic quantities as well as susceptibilities at vanishing chemical potential are well reproduced. The QCD phase diagram exhibits a first-order liquid-gas as well as a deconfinement transition with a critical endpoint at large chemical potential. We will present the resulting neutron stars that agree with observed heavy neutron star masses and the deformability of the stars are in accordance with the gravitational wave signal from the merger. The compact stars have small radii and consist mainly of a mixed quark-hadron phase.
Furthermore, we will discuss consequences of the model for the matter created in a neutron star merger and how the properties of hot as well as dense matter are interconnected.

Speaker: Stefan Schramm

QM2018_SCHRAMM.pdf

122 The QCD equation of state at finite density, from the known to the unknown

The theory of quantum chromodynamics (QCD) is expected to have a rich phase structure at finite chemical potential and temperature. Its study is a central topic of high energy nuclear physics. Theoretical studies employing lattice QCD methods have already established that the transition from hadrons to quarks proceeds as a smooth crossover in the case of vanishing net baryon number density. At very large net baryon densities and low temperatures, astrophysical observations have become more important in constraining the QCD Equation of State. Nuclear matter ground-state properties as well as properties of compact stars and their violent mergers will serve to determine the equation of state at several times nuclear ground-state density.

In this talk I will present the first calculation
of the QCD phase strcuture and thermodynamics which is shown to be consistent with lattice QCD
results at small barychemical potential as well as nuclear matter properties
and known constraints from compact star observations[1,2].
In this context I will discuss the most relevant properties and constraints which should
be satisfied by any model which attempts to predict the QCD phase structure.
Furthermore, I will present results on the baryon number susceptibilities calculated with this
model and discuss how nuclear interactions may strongly influence the measured
baryon number fluctuations in nuclear collisions at low beam energies [1].
Finally, I will also address similarities and differences between the matter created in heavy ion collisions
and in mergers of compact stars and how both can be described in a unified framework [3].

[1] A.Mukherjee, JS and S.Schramm, Phys. Rev. C 96, no. 2, 025205 (2017)
[2] A.Mukherjee, S.Schramm, JS and V. Dexheimer, arXiv:1706.09191 [nucl-th].(accepted for pulication in Atronomy & Astrophysics)
[3] M.Hanauske, JS et al., J. Phys. Conf. Ser. 878, no. 1, 012031 (2017).

Speaker: Dr Jan Steinheimer

steinheimer_neu.pdf

123 Constraining production models with light (anti-)nuclei measurements in small systems with ALICE at the LHC

The large sample of high quality data taken in pp collisions at $\sqrt{s} = 7$ TeV and 13 TeV, together with smaller data sets at 900 GeV and 2.76 TeV, and in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV at the LHC with the ALICE detector allows for a systematic study of the light (anti-)nuclei production in these collision systems.

The excellent performance of the Inner Tracking System, the Time Projection Chamber and the Time-Of-Flight detector provide a clear identification and separation of primary produced light (anti-)nuclei from secondaries.

Additionally, the high energy deposit of Z=2 particles in the Transition Radiation Detector has been exploited to collect a hardware-triggered data sample in the high-interaction rate p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 8.16 TeV. First findings from this (anti-)nuclei enriched sample will be shown.

Recent results on deuteron production as a function of multiplicity in pp and p-Pb collisions will be presented, as well as the measurement of helium-3 in p-Pb collisions. The goal is to study production mechanisms such as coalescence in small systems, and to compare them to those in heavy-ion collisions. To achieve this, the coalescence parameter $B_{A}$ is studied as function of transverse momentum in the different systems and as a function of the event multiplicity. In addition to this, prospects for measuring (anti-)deuteron production in jets will be presented.

These investigations have direct connections to cosmological and astrophysical studies, in particular for the search of dark matter candidates where one possible signal is the increased flux of light anti-nuclei which has an interplay with the $B_{A}$ measurementes shown here.

Speaker: Manuel Colocci (Universita e INFN, Bologna (IT))

NucleiSmallSystemsLHCmcolocciQM18.pdf

NucleiSmallSystemsLHCmcolocciQM18.pptx

124 Recent Results from the STAR Fixed-Target Program

The data from RHIC Beam Energy Scan phase I (BES-I) have shown interesting results below $\sqrt{s_{NN}}<$ 19.6 GeV in identified hadron anisotropy ($v_1$, $v_2$, $v_3$), kaon over pion ratios, and net-proton higher moments. These interesting features continue to the lowest energy, $\sqrt{s_{NN}}$ = 7.7 GeV, and motivate the investigation to even lower energy collisions. The STAR fixed-target program extends the energy reach from $\sqrt{s_{NN}}$ =7.7 GeV to $\sqrt{s_{NN}}$ = 3.0 GeV, corresponding to baryon chemical potential 420 MeV to about 700 MeV range. The comparison of the asymmetric system (Al+Au) and symmetric system (Au+Au) at almost equal number of participating nucleons from most central to mid-central collisions provides useful information on nucleon stopping, which is key to understanding the baryon chemical potential.

We present results from Al (beam)+Au (target) collisions at $\sqrt{s_{NN}}$ = 4.9 GeV and Au+Au collisions at $\sqrt{s_{NN}}$ = 4.5 GeV from the STAR fixed-target program. We will report transverse mass spectra, rapidity density distributions, particle ratios, centrality dependence and directed flow of protons, $\pi^{\pm}$, $K_{s}$ and $\Lambda$, elliptic flow of protons, $\pi^{\pm}$ and K, and HBT homogeneity lengths of pions. Pion and proton elliptic flow show mass ordering. Number of constituent quark scaling tests will be presented. For the asymmetric Al+Au system, the peak of the rapidity density distributions is shifted from the nucleon-nucleon center-of-mass rapidity. The magnitude of this shift varies with centrality and is a measure of the nucleon stopping. These newly measured data will be compared with previously published results from the AGS and SPS. The implications of the results on future STAR fixed-target physics runs will be discussed.

Speaker: Yang Wu (Kent State University)

yangwu_qm_talk_final.pdf

125 High baryon densities achievable at RHIC and LHC

In high energy collisions nuclei are practically transparent to each other but produce very hot, nearly baryon-free, matter in the central rapidity region. Where do the baryons go? We calculate the energy loss of the nuclei using the color glass condensate model. Using a space-time picture of the collision we calculate the baryon and energy densities of the receding baryonic fireballs. For central collisions of large nuclei at RHIC and LHC we find baryon densities more than ten times that of atomic nuclei over a large volume which appear at high rapidities. These results can and are being used as initial conditions for subsequent hydrodynamic evolution and could test the equation of state of matter at very high baryon densities.

Speaker: Prof. Joseph Kapusta (University of Minnesota)

Kapusta_QM2018.pdf

126 Perspectives on strangeness physics with the CBM experiment at FAIR

The main goal of the CBM experiment at FAIR is to study the behavior of nuclear matter at very high baryonic density in which the transition to a deconfined and chirally restored phase is expected to happen. One of the promising signatures of this new states are the enhanced production of multi-strange particles. The CBM detector is designed to measure such rare diagnostic probes with unprecedented precision and statistics.
Important key observables are the production of hypernuclei and dibaryons. Theoretical models predict that single and double hypernuclei, and heavy multi-strange short-lived objects are produced via coalescence in heavy-ion collisions with the maximum yield in the region of SIS100 energies. The discovery and investigation of new hypernuclei and of hyper-matter will shed light on the hyperon-nucleon and hyperon-hyperon interactions.
Results of feasibility studies of these key CBM observables in the CBM experiment are discussed.

Speaker: Vassiliev Iouri (GSI)

QM2018_Vassiliev_Strangeness_CBM.pdf

Open heavy flavour: I

Convener: Magdalena Djordjevic (Institute of Physics Belgrade)

127 Measurements of D meson nuclear modification factors and of direct and elliptic flow of D0 mesons in pPb and PbPb collisions at 5.02 with CMS

the study of charm production in heavy-ion collisions is considered an excellent probe to study the properties of the hot and dense medium created in heavy-ion collisions. Measurements of D- meson nuclear modification, elliptic and triangular flow in PbPb collisions can provide strong constraints into the mechanisms of in-medium energy loss and charm flow in the medium. The measurement of charm flow and, in particular, of the direct flow coefficient is also expected to be sensitive to the extremely strong but short-lived magnetic field induced by the spectator protons in non- central collisions. This strong magnetic field is indeed expected to generate differences in rapidity-odd directed flow for charm and anti-charm mesons, which can be measured with high precision with the CMS apparatus. In this talk, the measurements of the $D^0$ nuclear modification factor, of the elliptic and triangular flow measured by CMS in PbPb collisions at 5.02 TeV will be presented together with the a new measurement of $D^0$ $R_{pPb}$ in pPb collisions at 5.02 TeV, which can provide more constrains into the relevance of cold nuclear matter effects at central rapidity down to very low tranverse momenta. The first measurement of the direct flow of charm and anti-charm in non-central collision will also be shown and compared to those for inclusive charged particles, previously measured by the CMS Collaboration.

Speaker: Zhaozhong Shi (Massachusetts Inst. of Technology (US))

Quark Matter 2018 Presentation Final Draft.pdf

128 Heavy-flavour decay lepton production in Pb-Pb and Xe-Xe collisions at the LHC with ALICE

Heavy quarks, i.e. charm and beauty, are formed on a shorter time scale with respect to the strongly-interacting Quark-Gluon Plasma (QGP) produced in high-energy heavy-ion collisions. Therefore, they are sensitive probes to study the mechanisms of parton energy loss, hadronisation in the hot and dense medium, the medium evolution and its transport coefficients. The heavy-flavour nuclear modification factor ($R_{\rm AA}$) and the elliptic flow ($v_2$) are two of the main experimental observables that allow us to investigate the interaction strength of heavy quarks with the constituents of the expanding medium. The comparison of the $R_{\rm AA}$ of charm, beauty and light-flavour hadrons provides information about the colour-charge and parton-mass dependence of parton energy loss. At low $p_{\rm T}$ the $v_2$ is expected to give insights into the degree of thermalisation of heavy quarks in the deconfined medium, and at high $p_{\rm T}$ it carries information on the path-length dependence of in-medium parton energy loss.

In this talk, measurements of $R_{\rm AA}$ and $v_2$ of open heavy-flavour hadrons via semi-leptonic decays to electrons at mid-rapidity and muons at forward rapidity in Pb-Pb collisions at LHC energies will be discussed. The progress on the analysis of the production and anisotropy of electrons from beauty-hadron decays will also be discussed. In addition, the $R_{\rm AA}$ of heavy-flavour hadron decay leptons in Xe-Xe collisions will be presented, along with the prospects for measuring the total charm cross section in this collision system. Comparisons with model calculations including the interaction of heavy quarks with the hot, dense, and deconfined medium will be also shown.

Speaker: Andrea Dubla (GSI)

HF_PbPb_QM18_ADubla169.pdf

129 Transport properties from Charm to Bottom: $p_T$ suppression, anisotropic flow $v_n$ and their correlations to the bulk dynamics

We study the propagation of charm and bottom quarks in the quark-gluon plasma (QGP) by means of a relativistic Boltzmann transport approach that in the large M/T limit recovers the standard Langevin dynamics. The non-perturbative interaction between heavy quarks and light quarks is described by means of a quasi-particle approach in which light partons are dressed with thermal masses. The last tuned to lattice QCD thermodynamics naturally induce a non-perturbative interaction that entails only a weak dependence on the temperature especially around the critical temperature $T_c$, which plays a fundamental role to describe simultaneously the experimental data for the nuclear suppression factor $R_{AA}$ and the elliptic flow $v_2(p_T)$ of D mesons from RHIC to LHC energies. In the same scheme we present predictions for B mesons at 5.02 ATeV that shows a quite significant suppression and allow a determination of the space-diffusion coefficient that is practically independent on the transport scheme for HQ (Boltzmann vs Langevin). The last is seem to largely deviate from from pQCD estimate but also to be still somewhat larger than AdS/CFT and quite close to lattice QCD calculations. Finally it will be discussed the relevance of initial state fluctuations that allows to extend the analysis to high order anisotropic flows $v_3(p_T)$ and $v_4(p_T)$ as well as to investigate the role of QCD interaction in developing correlations between the light and the heavy flavor anisotropic flows. These will provide novel and powerful constraints for the transport coefficients.

[1] F. Scardina, S. K. Das, V. Minissale, S. Plumari, V. Greco, Phys.Rev. C96 (2017) no.4, 044905.
[2] S. K. Das, F. Scardina, S. Plumari, V. Greco, Phys.Lett. B747 (2015) 260.
[3] F. Scardina, D. Perricone, S. Plumari, M. Ruggieri, V. Greco, Phys.Rev. C90 (2014) no.5, 054904.
[4] S. Plumari, G. L. Guardo, F. Scardina, V. Greco, Phys.Rev. C92 (2015) no.5, 054902.

Speaker: Salvatore Plumari (University of Catania (Italy))

PLUMARI_QM2018_VENICE.pdf

130 Measurements of Open Charm and Bottom Production in Au+Au Collisions at √sNN = 200 GeV with the STAR Experiment at RHIC

Heavy flavor quarks are unique tools for studying the properties of the Quark Gluon Plasma (QGP) produced in high-energy nuclear collisions. In this talk we will present measurements of various charm hadrons ($\Lambda^{\pm}_{c}$, $D^{\pm}_{s}$, $D^{*\pm}$, $D^{\pm}$ and $D^0$ ($\bar{D}^0$), as well as open bottom production through displaced decay daughters ($B\rightarrow J/\psi$, $D^0$, $e$), at mid-rapidity in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV, using the STAR Heavy Flavor Tracker. With the high statistics data collected in 2016 and the use of supervised machine learning methods for topological reconstruction of charm hadrons, the $\Lambda^{\pm}_{c}$ and $D^{\pm}_{s}$ signal significances are improved significantly. This allows us to study the $p_T$ and centrality dependences of their production. We will also report on $D^{*\pm}$, $D^{\pm}$ and $D^0$ spectra measured in various centralities and the total charm quark cross section extracted from these extensive measurements as well. In addition, we will present the nuclear modification factors for daughters from decays of bottom hadrons and compare them to those for charm hadrons as well as to theoretical calculations. Physics implications of these measurements for the mass dependences of parton interactions with the QGP, as well as the charm quark hadronization in the medium will be discussed.

Speaker: Sooraj Krishnan Radhakrishnan (Lawrence Berkeley National Laboratory)

QM18OpenHF_SRadhakrishnan.pdf

131 Nuclear modification factor of charm and bottom quark yields in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV by the PHENIX Experiment

Experimental results at RHIC and at the LHC show the same strong suppression for
light and heavy quark probes at high $p_T$, and a possible quark mass
dependence at low $p_T$. More high precision measurements of separated charm and bottom are needed to quantify the dependence of medium energy loss on the quark mass.

The PHENIX Experiment measures electrons from heavy flavor decays using displaced
vertex distributions at mid-rapidity $|y|<$0.35. The nuclear modification of
charm and bottom decays in the semi-electronic channel is obtained for
$1 < p_T < 8$ GeV/c from the new 2015 $p$+$p$ reference data and a much-improved analysis of the 2014 high statistics Au+Au data. PHENIX is also able to measure $B\rightarrow $J$/\psi$ decays in the rapidity range $1.2<|y|<2.2$ for $p_T>0$.

This presentation will report on the nuclear modification factor of separated
charm and bottom yields at mid-rapidity along with the status of the forward rapidity $B\rightarrow$J/$\psi$ analysis using the large statistics obtained during the 2014 Au+Au run.

Speaker: Takashi Hachiya (RIKEN)

QM2018_hfe_hachiya_v5.pdf

132 Measurements of strange and non strange beauty production in PbPb collisions at 5.02 TeV with the CMS detector

Beauty quark production in heavy-ion collisions is considered to be one of the key measurements to address the flavour-dependence of in-medium energy loss in heavy-ion collisions. On the other hand, the measurement of the production of strange beauty mesons can provide fundamental insights into the relevance of mechanisms of beauty recombination in the quark-gluon plasma. In this talk, we will present the state of the art of beauty measurements in PbPb collisions in CMS that includes the $R_{AA}$ measurement of fully reconstructed $B^{+}$ mesons and the latest measurements of non-prompt $D^0$ and $J/\psi$ from B decay over a wide transverse momentum range in the same colliding system. The first measurement of the $B_{s}$ $R_{AA}$ in PbPb collisions will also be presented as well as the ratio between the production yield of $B_{s}$ and $B^{+}$.

Speaker: Ta-Wei Wang (Massachusetts Inst. of Technology (US))

20180515_tawei_MIT_QM2018.pdf

133 Multi-stage jet evolution and mass hierarchy of heavy quark energy loss in heavy-ion collisions

Heavy quarks serve as valuable probes of the QGP properties as well as the mass hierarchy of parton energy loss. Experimental data at the LHC indicate significant nuclear modification of heavy flavor ($D$ & $B$) meson production that is comparable to light flavor hadrons, which seem contradictory to one’s earlier expectation of $\Delta E_g > \Delta E_q > \Delta E_c > \Delta E_b$. We extended the Linear Boltzmann Transport (LBT) model coupled to hydrodynamic medium to heavy quark jet evolution in the QGP including both elastic and inelastic scattering processes [1,2]. Within the LBT model, we obtain good descriptions of heavy flavor meson suppression, elliptic and triangular flow coefficients observed at the LHC and RHIC.

The time-ordered transport model is further combined with a virtuality-ordered parton shower scheme into a multi-stage evolution approach [3,4] that includes a rare-scattering multiple emission formalism at momentum large compared to heavy quark mass (sensitive only to the transverse diffusion coefficient), and a single scattering induced emission formalism at momentum comparable to mass (sensitive to the transverse diffusion as well as longitudinal drag and diffusion coefficients). This multi-stage approach reduces the difference of energy loss between $c$ and $b$ quarks and simultaneously describes $D$ and $B$ meson $R_\mathrm{AA}$. In addition, the mass (or velocity) dependence of jet-induced medium excitation is explored for the first time. Its effects on the mass hierarchy of parton energy loss and heavy-light hadron correlation functions are investigated.

[1] S. Cao, T. Luo, G.-Y. Qin, and X.-N. Wang, Phys. Rev. C94 (2016) 1, 014909.
[2] S. Cao, T. Luo, G.-Y. Qin, and X.-N. Wang, arXiv:1703.00822.
[3] S. Cao, A. Majumder, G.-Y. Qin, and C. Shen, arXiv:1711.09053.
[4] S. Cao, et al., Phys. Rev. C96 (2017) 2, 024909.

Speaker: Shanshan Cao (Wayne State University)

Shanshan - QM 2018.pdf

Shanshan - QM 2018.pptx

Thermodynamics and hadron chemistry: I

Convener: Boris Hippolyte (IPHC / USIAS (Strasbourg, FR))

134 Analysis of Kaon fluctuations from the Beam Energy Scan at RHIC

We analyze the recent STAR collaboration results on net-kaon fluctuations in the framework of the Hadron Resonance Gas (HRG) model and lattice QCD. In the latter, the kaon contribution is isolated using the Boltzmann approximation [1]. Our purpose is to extract the freeze-out temperature and chemical potential as functions of the collision energy. In our HRG model, we use the complete hadron spectrum from the latest PDG list. These results are compared to the freeze-out parameters obtained from a combined analysis of electric charge and net-proton fluctuations. Predictions for moment ratios of the net-Lambda multiplicity distribution are obtained along the kaon freeze-out line. They can be compared to forthcoming experimental results from RHIC Beam Energy Scan.

[1] J. Noronha-Hostler et al., arxiv: 1607.02527.

Speaker: Claudia Ratti (University of Houston)

talk_Venezia.pdf

135 Sub-threshold strangeness production measured with HADES

At energies below $\sqrt{s_{NN}}\approx2.55$ GeV, strange quarks can not be produced in binary nucleon-nucleon collisions because of the higher production threshold of the lightest hadrons carrying strangeness. Hence, the investigation of sub-threshold strangeness production in heavy-ion collision is one of the most promising probes, to access the properties of the created system, as the missing energy must be provided by the latter one.
For the first time, a nearly complete set of strange particles has been reconstructed in the 40% most central Au+Au collisions at 1.23A GeV. The data sample includes multi-differential representations of charged and neutral Kaons, Lambdas and Phi-mesons.
We observe a stronger than linear and universal scaling of all strange hadrons yields with increasing centrality, which does not reflect the different nucleon-nucleon thresholds of the various hadrons carrying strangeness. The data are confronted with various phenomenological approaches.

Speaker: Georgy Kornakov (TU Darmstadt)

QM18_HADES_strangeness_Kornakov.pdf

136 Shear viscosity and resonance lifetimes in the hadron gas

Previous calculations of the shear viscosity to entropy density ratio in the hadron gas have failed to reach a consensus, with $\eta/s$ predictions differing by almost an order of magnitude. This work addresses and solves this discrepancy by providing an independent extraction of this coefficient using the newly-developed SMASH (Simulating Many Accelerated Strongly interacting Hadrons) transport code and the Green-Kubo formalism. We compare the results from SMASH with numerical solutions of the Boltzmann equation for various systems using the Chapman-Enskog expansion as well as previous results in the literature. Substantial deviations of the coefficient are found between transport approaches mainly based on resonance propagation with finite lifetime (such as SMASH) and other (semi-analytical) approaches with energy-dependent cross-sections, where interactions do not introduce a timescale other than the inverse scattering rate. Our conclusion is that long-lived resonances strongly affect the transport properties of the system, resulting in significant differences in η/s with respect to other approaches where binary collisions dominate. We argue that the relaxation time of the system —which characterizes the shear viscosity— is determined by the interplay between the mean-free time and the lifetime of resonances. We finally show how an artificial shortening of the resonance lifetimes or the addition of a background elastic cross section nicely interpolate between the two discrepant results. To turn this around, we finally note that the temperature dependence of $\eta/s$ can be used to constrain the properties of the hadron gas.

Speaker: Mr Jean-Bernard Rose (Frankfurt Institute for Advanced Studies)

qm2018_talk.pdf

137 Precise measurement on hypertriton and anti-hypertriton masses and lifetimes with the Heavy Flavor Tracker and the production of triton in Au+Au collisions at STAR

The Hyperon-Nucleon (Y-N) interactions play an important role for understanding the strong interaction. It is suggested that alternative Y-N couplings can be a possible solution to the recent observations of neutron star exceeding two solar masses, the so-called "hyperon puzzle". A precise measurement of masses and lifetimes of hypertriton and anti-hypertriton can enrich our knowledge on Y-N interactions. In addition, the light nuclei distributions provide an excellent tool for understanding the freeze-out conditions of system created in high-energy nuclear collisions. For example, the yield ratio of triton, $N(t)$, deuteron, $N(d)$, and proton, $N(p)$, which is defined as $N(t)N(p)/N^2(d)$ may be utilized as an alternative variable in the search of the QCD critical point.

In this talk, we will present the first precise measurement of hypertriton and anti-hypertriton masses in heavy-ion collisions at STAR with the Heavy Flavor Tracker (HFT). Hypertritons and anti-hypertritons are reconstructed through both two-body decay channel ($^3He+\pi^-$) and three-body decay channel ($p+d+\pi^-$) using the high-statistics data collected in 2014 and 2016 Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV. The binding energies and lifetimes of the (anti-)hypertriton will be extracted from this precise measurement. We will also present the centrality dependence of the mid-rapidity $p_T$ spectra of triton ($t$) from Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, 200 GeV. The collision energy and centrality dependence of the yield ratio, $N(t)N(p)/N^2(d)$, and the coalescence parameters of $d$ ($A$ = 2) and $t$ ($A$ = 3) will be also presented. Physics implications of these measurements will be discussed.

Speaker: Peng Liu (SINAP&BNL)

QM2018_PengLiu.pdf

138 Addressing the hyper-triton lifetime puzzle with ALICE at the LHC

We present a measurement of the hyper-triton lifetime with the ALICE detector at the LHC, aiming at shedding light on the hyper-triton lifetime puzzle. During the LHC Run 2, the ALICE experiment recorded Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV that complement the Pb-Pb datasets acquired at $\sqrt{s_{\rm NN}}$ = 2.76 TeV from Run 1. These datasets allow for a systematic study of light (anti-)hypernuclei production in Pb-Pb collisions, in particular, for the hyper-triton lifetime determination.

The identification of the hyper-triton is based on the excellent performance in terms of energy loss measurement in the Time Projection Chamber. In addition, the Inner Tracking System is used to discriminate secondary vertices, originating from weak decays, from the primary vertex. This is of particular importance for the measurement of (anti-)(hyper-)triton that decays weakly with a decay length of several centimetres.

The study of (anti-)(hyper-)nuclei production at both energies will be discussed and compared to model predictions. Special emphasis will be put on new results of the hyper-triton lifetime determination in its 2- and 3-body decay modes. Indeed most calculations on the lifetime of hyper-triton give similar lifetimes, which are close to the lifetime of free $\Lambda$ decays. On the experimental side, all results in Au+Au collision at RHIC and in Li+C collisions at GSI show a significantly shorter lifetime in comparison with that of the free $\Lambda$ decay.

A detailed discussion of the experimental results and the effort needed on both the experimental and the theoretical side in this sector will be presented.

Speaker: Stefano Trogolo (Universita e INFN Torino (IT))

Trogolo_QM_2018_final.pdf

139 Entanglement and thermalization

In a quantum field theory, apparent thermalization can be a consequence of entanglement as opposed to scatterings. I will discuss how this can help to explain open puzzles such as the success of thermal models in electron-positron collisions. It turns out that an expanding relativistic string described by the Schwinger model (which also underlies the Lund model) has at early times an entanglement entropy that is extensive in rapidity. At these early times, the reduced density operator is of thermal form, with an entanglement temperature $T_\tau=\hbar/(2\pi k_B \tau)$, even in the absence of any scatterings.

Speaker: Stefan Floerchinger (Heidelberg University)

FloerchingerQMVenice2018.pdf

140 Hadronic resonances, strange and multi-strange particle production in Xe-Xe and Pb-Pb collisions with ALICE at the LHC

The measurement of strange and resonance particle production in relativistic heavy ions collisions is of great interest to investigate the properties of the hadronic matter under extreme conditions. The enhanced production of strange and multi-strange hadrons with respect to non-strange ones was
historically considered as one of the signatures of the formation of a partonic phase during the evolution of the system created in such collisions. Moreover, hadronic resonances are used to study the energy dependence of the hadronic interactions and jet quenching, giving us the possibility to constrain the lifetime of the hadronic phase.

In this talk, we present a comprehensive set of measurements on hadronic resonance, strange and multi-strange particle production in collisions of Xe-Xe and Pb-Pb at the center-of-mass energies of $\sqrt{s_{\rm NN}} = 5.44$ and 5.02 TeV, respectively, measured by the ALICE experiment at the LHC.
Transverse momentum spectra, integrated yields, mean transverse momenta and particle ratios are presented as a function of centrality for $K^{0}_{S}$, $\Lambda$, $\Xi^{-}$, $\bar{\Xi}^{+}$, $Omega^{-}$, $\bar{\Omega}^{+}$, $\rho(770)^{0}$, $K*(892)^{0}$, $\phi(1020)$, $\Sigma(1385)^{\pm}$,
$\Lambda(1520)$ and $\Xi(1530)^{0}$. Measurements of the nuclear modification factors are also shown for resonances. Our results are discussed and compared to statistical hadronisation models calculations and with predictions of QCD inspired event generators. Additionally, comparisons with lower energy measurements, including an improved re-analysis of the 2.76 TeV sample for the strangeness sector, are also presented.

Speaker: Danilo Silva De Albuquerque (University of Campinas UNICAMP (BR))

HadResStrMstrAA_QM18_v4.pdf

Poster Session

Instructions for presenters

ListOfPosters_BoardNumbers.pdf

141 Search for the d*(2380) in p-Pb collisions at 5 TeV with ALICE at the LHC

The ALICE Collaboration started to investigate the baryon-baryon interaction through the search for exotic bound states via invariant mass analyses of different possible decay channels.
In this poster the study of the $d^{*}(2380)$ production in p-Pb collisions at $\sqrt{s_{\rm NN}}$=5.02 TeV with the ALICE detector at the LHC will be presented.
This dibaryon was recently observed at WASA-at-COSY. A narrow resonance with I($J^{P}$) = 0($3^{+}$) - named now $d^{*}(2380)$ - has been observed in all relevant two-pion decay channels as well as in np-scattering. Quark model calculations predict this state to be a compact hexaquark structure of size 0.8 fm, whereas Faddeev calculations with hadronic interactions favour a molecular structure.
Thanks to the excellent tracking and particle identification capabilities of the ALICE apparatus, the reconstruction and identification of the products of the $d^{*}(2380)$\rightarrow$d+pi^{+}+pi^{-}$ decay over a large momentum range is possible with high efficiency. A detailed Monte Carlo study of the expected correlated and uncorrelated background sources in the $d^{*}(2380)$ relevant invariant mass region will be presented in order to have an estimation of the statistical significance of the measurement.
The confirmation of the existence of the $d^{*}(2380)$ state would provide a new candidate for an exotic degree of freedom in the nuclear equation of state at high densities (e.g. neutron stars) and will open the hunt for other possible non-trivial exotic states produced in heavy ion collisions.

Speaker: Pietro Fecchio (Universita e INFN Torino (IT))

QM_Poster.pdf

142 Energy dependence of particle production and $R_{\rm AA}$ in Pb--Pb collisions with ALICE

In late 2015 the ALICE collaboration recorded Pb--Pb and pp collisions at $\sqrt{s_{\rm NN}}$ ($\sqrt{s}$) = 5.02 TeV.
The availability of data at the highest energy ever achieved in laboratory for heavy-ion collisions together with a pp reference at the same energy opens up the possibility for a detailed study of the nuclear modification factors ($R_{\rm AA}$) of identified particles.

The excellent particle identification capabilities of the ALICE experiment allow to measure the production of pions, kaons and protons over a wide range of transverse-momenta ($p_{\rm T}$).
Particle ratios as a function of the collision centrality are compared to previous results at lower energy to investigate the dynamics of particle production.

In light of the new set of results, a discussion of the latest model predictions of light flavor particle production is presented.

Finally, to quantify the effect of the energy loss in the QCD medium created in the collision, the nuclear modification factors ($R_{\rm AA}$) are computed and compared with results obtained at lower energy.

Speaker: Nicolo Jacazio (Universita e INFN, Bologna (IT))

2018-may-13-conference_presentation-jacazio_poster_qm2018_v2.pdf

143 "Classicalization" of quarkonia in the quark-gluon plasma

Recently there has been rapid progress in understanding in-medium dynamics of a quarkonium based on the framework of open quantum system [1-5]. The stochastic potential model [5] introduces thermal fluctuations on Debye screened potential and hence incorporates wave function decoherence. This model however lacks quantum dissipation, which has so far limited its application to early times and has prevented comparison with experimental measurements. In this contribution, we present two strategies that overcome this limitation:

1. quantum-classical matching
   by investigating the localization properties of wave function and in turn of the reduced density matrix, we show, how, at intermediate time scales, one can switch from the quantum dynamics of the stochastic potential model to the classical dynamics of a Langevin equation. It involves matching the Wigner quasi-probability function of the former to the phase space distribution function of the latter. The validity of this matching procedure is discussed.

2. quantum state diffusion
   by directly implementing the quantum state diffusion formalism [6] for the Lindblad master equation [1] of a quarkonium, i.e. mapping the Lindblad master equation to a non-linear stochastic Schrödinger equation (NLSSE) for the wave function. This for the first time provides a direct link between QCD and phenomenological models based on non-linear Schrödinger equations. By numerically solving the corresponding NLSSE, we can capture quantum dissipation and thus the thermalization of quarkonia in a quantum mechanical manner. For simplicity, we discuss this formalism for a single heavy quark in the QGP.

[1] Akamatsu, Phys. Rev. D91 (2015) 056002.
[2] Blaizot et al., Nucl. Phys. A946 (2016) 49.
[3] De Boni, JHEP 08 (2017) 064.
[4] Brambilla et al., Phys. Rev. D96 (2017) 034021.
[5] Akamatsu and Rothkopf, Phys. Rev. D85 (2012) 105011; Kajimoto et al., arXiv: 1705.03365, PRD in press.
[6] Gisin et al., J. Phys. A: Math. Gen. 25 (1992) 5677.

Speaker: Shiori Kajimoto (Osaka University)

Quark matter 2018_kajimoto.pdf

144 $b\bar{b}$ dijet angular correlations in Pb+Pb collisions at $\sqrt{s}$= 8.8 TeV

Heavy flavoured jets are important in many of today's studies both as tests of QCD and as probes of hot and dense medium created shortly after the hard scattering. We notice that recently $b\bar{b}$ dijet correlations in proton-proton collisions have been measured by the CMS and ATLAS collaborations at the LHC, NLO+PS p+p baseline could give a rather perfect description of the experimental data than PYTHIA. Moreover detailed mechanisms of heavy flavoured jets propagation and energy loss in dense QCD matter are not yet fully investigated.
In this talk, we present the first predictions of the $b\bar{b}$ dijet angular correlations in Pb+Pb collision. In this work, a NLO+PS event generator SHERPA has been employed to give the p+p baseline and events, A Langevin evolution is used to describe the heavy quark evolution ,and the higher-twist approach is implemented to simulate the radiative energy loss of the gluon,heavy and light quarks simultaneously,and the hard-thermal-loop calculation is used to describe the collisional energy loss of light quarks and gluon. We predict the azimuthal angle $\Delta \phi$ , angular distance $\Delta R$ , and rapidity variables $y_B $ distributions of the normalized $b\bar{b}$ dijet production at the LHC 8.8 TeV. We find the energy loss of the $b\bar{b}$ dijet will suppress and broden the near side(small $\Delta \phi$)peak and also enhance and sharp the away side (near $\Delta \phi=\pi$ ) peak. We have also calculated the distribution of transverse momentum $p_T$ of $b\bar{b}$ dijet, the transverse momentum imbalance $X_j$ of back-to-back $b\bar{b}$ dijet pairs and the flavour asymmetry $A_b$ of mixed-flavour dijet pairs to gain new insight into heavy flavour dynamics in the quark-gluon plasma.

Speaker: Sa Wang (Central China Normal University)

poster-wangsa.pdf

145 A feasibility study of hypernuclei reconstruction at NICA/MPD

Presented is a feasibility study of hypernuclei mesurments for the upcoming NICA/MPD Project. The DCM-LAQGSM model was used as well as the full realistic MPD reconstruction chain. Presented here are invaraint mass spectra for three decay modes. A good resolution with 3 MeV/c$^{2}$ was achieved.

Speaker: Mariya Ilieva (JINR)

146 A Monte-Carlo Model Simulating an Evolving and Fluctuating Heavy Ion Collision Yield

The relativistic heavy ion collisions undergo extremely hot and dense phases, which are postulated to resemble parts of the cosmological early stages. This suggests that the collisions could provide a QCD laboratory, in which phenomena of strong interactions are studied. The investigations of colour interactions in the collisions are made in a Monte-Carlo computational model which implements dynamical interactions. The dynamics are in present work modelled as a superposition of parameterized hydrodynamics and a media-modulated hard state. In the simulations, observations are differentiated in terms of density, position, and production modes; in combination with a higher order analysis. The heavy ion yield appears to have been reproduced to great detail in present model. The reproduction of both elliptic-, and triangular flow speaks of a fluctuating-, and density-characterized first order geometric mode, in addition to higher order features. In the simulations, it seems that the particle fragmentation is density characterized, thus providing a channel for pressure differentiated observations. Therefore it is concluded that the present computational model is reproducing the heavy ion yield to higher orders, thus supporting observables which differentiates strong phenomena within the simulated evolving matter.

Speaker: Mr Bengt Henrik Brusheim Johansson (NFR, Norway)

QM2018Poster.pdf

147 A new correlator for the detection and characterization of the Chiral Magnetic Effect

A charge-sensitive in-event correlator ($R(\Delta S)$) is proposed and tested for its efficacy to detect and characterize charge separation associated with the Chiral Magnetic Effect (CME) in heavy ion collisions~[1]. For CME-driven charge separation, the correlator gives a concave response relative to the second-order event plane ($\Psi_2$), and a null response relative to the third-order plane ($\Psi_3$), consistent with the correlation (de-correlation) of the $\vec{B}$-field with the $\Psi_2$ ($\Psi_3$) plane. For non-CME background, the correlator gives responses, relative to $\Psi_2$ and $\Psi_3$, which allows a distinction between CME-driven charge separation and non-CME backgrounds. We discuss the $R(\Delta S)$ correlator and present results for its detailed response and sensitivity, to both signal and background, in several reaction models. They include (but are not limited to) a 3+1-dimensional hydrodynamic model [2], the Anomalous Viscous Fluid Dynamics (AVFD) model [3] and the Multi-Phase Transport model (AMPT) [4]. The implications for the use of the $R(\Delta S)$ correlator in the upcoming Isobar Run at RHIC will also be discussed.

[1] N. Magdy, S. Shi, J. Liao, N. Ajitanand, and R. A. Lacey, arXiv:1710.01717

[2] P. Bozek, arXiv:1711.02563

[3] S. Shi, Y. Jiang, E. Lilleskov, J. Liao, arXiv:1711.02496

[4] Lin Z W et al. Phys.Rev. C72 064901 (2005)

Speaker: Shuzhe Shi (Indiana University)

148 A new large acceptance silicon pixel detector for measurements of heavy flavour by NA61 Beyond 2020

The NA61/SHINE experiment at the CERN SPS experiment is planning to upgrade the detector and extend the heavy-ion programme after 2020 to allow precise measurements of particles with short lifetime (charmed particles in particular).

The study of heavy flavour production is a sensitive tool for new detailed investigations of the properties of hot and dense matter formed in nucleus-nucleus collisions. In particular, it offers new possibilities for studies of such phenomena as in-medium parton energy loss and quarkonium dissociation and possible regeneration, thus providing new information to probe deconfinement. Recently a silicon Small-Acceptance Vertex Detector was installed to measure production of open charm mesons. It is planned to significantly expand the vertex detector with more sensors both in longitudinal and transverse directions, as well as tho increase by an order of magnitude the read-out rate. In addition to improve measurements of open charm particles, the larger size will also significantly increase the capabilities to reconstruct the secondary vertices of relatively long-lived (multi strange) particles that decay inside the detector.

The physics motivation as well as the proposed detector layout simulations and hardware implementation will be discussed.

Speaker: Anastasia Merzlaya (St Petersburg State University (RU), Jagiellonian University (PL))

MerzlayaA_QM2018.pdf

149 A Quark-Gluon Plasma inspired model of the universe

We show that certain ideas developed in the last few years of heavy ion physics research could be used to produce key features of the standard cosmological model, in the context of a beyond the standard model pure gauge theory with a high (~TeV) equivalent of the QCD scale.
In particular, the peak in bulk viscosity argued to exist within QCD [1,2] can be used to generate inflation, while glueballs within the same theory are viable dark matter candidates.
We present solutions of the FRW equations for matter with these characteristics, in the hope of establishing weather the right number of e-foldings and dark matter abundance can be generated in such a model.

[1] https://inspirehep.net/search?p=find+eprint+0805.0442
[2] https://inspirehep.net/search?p=find+eprint+0707.4405

Speaker: Ms Melissa Mendes (IFGW)

150 A Simple Pico-second Timing ToF Prototype

DIRC-like Time-of-Flight detector (DTOF) is an innovative TOF utilizing internally reflected Cherenkov light for high energy charged particle identification. It achieves a high level of performance at the extreme data taking conditions under high luminosity and high backgrounds. The basic structure of DTOF is composed of a Fused Silica radiator connected to fast photomultiplier (MCP-PMT or SiPM) array, readout by a dedicated front-end electronics. The challenge comes from the fact that the limited flight length for charged particles in detectors requires its timing measurement achieves the level of tens of pico seconds, summing up all uncertainties, to meet the requirement for current and future high luminosity particle colliders. For example, the high luminosity upgrade of the Large Hadron Collider (HL-LHC) at CERN is expected to provide instantaneous luminosities of 1034cm-2s-1 and above, which requires TOF's time resolution ~30ps to suppress pileup in collisions.

To meet these requirements, we developed a pico-second timing TOF prototype based on DTOF technology, using 1.5cm x 1.5cm x 2cm square Cherenkov radiator connected by high-resolution fast MCP-PMT(Hamamastu R3809U). And we also developed high speed readout electronics (Bandwidth 2.4GHz, Gain 6dB ~ 26.6dB): Programmable Differential Amplifier(PDA) LMH6881/2 and Dual-threshold Differential Discriminator(DDD). It applied dual thresholds to process signals: low threshold to measure signals’ arrival time, while high threshold to identify real signals and exclude noise. It is a much simpler and faster timing method than wave sampling. The beam test in H4 at CERN shows that: the intrinsic time resolution readout by DDD and PDA is <20ps. Since there is no tracking selection and the readout electronics (PDA and DDD) are preliminary designation, there is still potential to improve its performance. We also plan to test larger radiator and various MCP-PMTs and SiPMs in the future.

Speaker: Xin Li (University of Science and Technology of China (CN))

QM_poster_xinli.pdf

151 Adaptation of the THERMINATOR model for BES program

THERMINATOR model [1] is a Monte Carlo event generator invented to study the statistical production of particles created in relativistic heavy-ion collisions. Its current description allows one to study the highest collision energies achieved by LHC and RHIC colliders. However it is possible to adapt THERMINATOR model to the lower energy spectrum as is used in Beam Energy Scan (BES) program at RHIC.
Femtoscopy of two particles investigates the properties of matter produced in heavy-ion collisions. Two-particle correlations use Quantum Statistics and the Final State Interactions which allow one to examinate the space-time characteristics of the medium.
For the first time we present single- and two-particle momentum distributions of identified particles generated for the energy spectrum from BES program. To verify how model predictions agree with experimental results, we compare transverse momenum distributions of pions, kaons and protons and the correlation functions obtained for identical pions in Au+Au collisions to the results from the STAR experiment from BES program.
[1] Comput.Phys.Commun. 183 (2012) 746-773

Speaker: Dr Hanna Zbroszczyk (Warsaw Univesroty Of Technology)

Zbroszczyk_Plakat.pdf

152 AdS/CFT predictions for partonic and fragmented momentum, azimuthal, and rapidity correlations of heavy flavors in pA and AA collisions

We compute the suppression, angular, and rapidity distribution of single open heavy flavour and the momentum, angular, and rapidity correlations for pairs of open heavy flavour in pA and AA collisions at RHIC and LHC from an AdS/CFT-based energy loss model. We quantitatively compare the strongly-coupled QGP predictions for AA collisions to the weakly-coupled QGP predictions of Nahrgang et al.

When restricted to leading order production processes, we predict similar angular correlations for open heavy flavour pairs in a strongly coupled plasma and a weakly coupled plasma, but with an order of magnitude difference in the low momentum momentum correlations. We find that the difference in momentum correlations from the AdS model compared to the pQCD model is, surprisingly, due to tighter momentum correlations in the AdS model than the pQCD model.

When initialised at next-to-leading order (aMC@NLO matched to Herwig++), we observe significant additional broadening of azimuthal correlations. However, the momentum correlations remain even when NLO production mechanisms are included. Thus, our conclusion for differences in momentum correlations with leading order production processes should carry over to next-to-leading order production processes once comparable predictions for a weakly-coupled QGP emerge.

We then show quantitative agreement between all measured high momentum open heavy flavour observables in AA collisions at RHIC & LHC and predictions from this new NLO production plus AdS energy loss model using a recent AdS derivation for the spectrum of momentum fluctuations. Finally, we present first results from this model for open heavy flavour observables in p+A collisions.

Speaker: Robert Hambrock (University of Cape Town)

AdS:CFT predictions for azimuthal and momentum correlations of heavy quarks in heavy ion collisions.pdf

153 ALICE studies of proton-hyperon and hyperon-hyperon interaction via the femtoscopy method in pp collisions

The initial conditions and particle emission in proton-proton collisions is much better constrained than in heavy-ion collisions. This allows for a precise investigation of the interaction between pairs of produced baryons such as proton-$\Lambda$ and $\Lambda$-$\Lambda$ in this system.

In this analysis femtoscopic correlations of proton-proton, proton-$\Lambda$ and $\Lambda$-$\Lambda$ pairs have been studied for the first time in pp collisions at $\sqrt{s}$=7 TeV and 13 TeV recorded with the ALICE detector.

A new formalism to separate the background contributions from the genuine correlation arising from the baryon-baryon interaction was developed. The measured correlations were fit with the parametrization obtained by the "Correlation Analysis Tool using the Schrödinger Equation (CATS)" .

The sensitivity to different interaction potentials of the proton-$\Lambda$ and $\Lambda$-$\Lambda$ correlation function is investigated and a comparison to previous measurements by the STAR collaboration is presented.

Speaker: Bernhard Hohlweger (Technische Universitaet Muenchen (DE))

QM_Hohlweger_Print.pdf

154 An equation-of-state-meter of QCD transition from deep learning with (2+1)-D relativistic viscous hydrodynamics coupled to a hadronic cascade model

Supervised learning with a deep convolutional neural network (CNN) is used to identify the QCD equation of state (EoS) employed in event-by-event (2+1)-D relativistic viscous hydrodynamics coupled to a hadronic cascade afterburner" simulations of heavy-ion collisions from the simulated final-state pion spectra $\rho(p_T, \phi)$. High-level correlations of $\rho(p_T,\phi)$ are learned by the neural network, which acts as an effectiveEoS-meter" in distinguishing the nature of the QCD transition. The EoS-meter is robust against many simulation inputs, such as shear viscosity, freeze-out temperature, equilibration time and collision energy. Thus the EoS-meter provides a powerful tool as the direct connection of heavy-ion collision observables with the bulk properties of QCD.

Speaker: Yilun Du (Frankfurt Institute of Advanced Studies, Goethe University Fran)

Yi-lun_Du_QM2018_poster.pdf

155 An event-shape-engineering method to study charge separation in heavy-ion collisions

Recent measurements of charge-dependent azimuthal correlations in high-energy heavy-ion collisions at RHIC and the LHC have indicated charge-separation signals perpendicular to the reaction plane, and have been related to the chiral magnetic effect (CME) (see a review in Ref [1]). The discovery of this phenomenon in heavy-ion collisions will signify simultaneously three important physics ingredients: the strongest magnetic field ever made by mankind, the chirality imbalance caused by vacuum transition, and the chiral symmetry restoration in the deconfined nuclear matter. However, the correlation signal is contaminated with the background driven by the elliptic flow ($v_2$) of the collision system [2], and an effective approach is needed to remove the flow background from the correlation.

In this talk, we will disclose a few shortcomings of a previous attempt of the event shape engineering (ESE) based on the "event-by-event $v_2$" [3]. We will further present a novel ESE technique [4] utilizing the magnitude of the flow vector to select spherical events in heavy-ion collisions, which leaves the charge separation measurements free of flow contributions. The simplified Monte Carlo simulations and a multi-phase transport model (AMPT) are employed to develop the ESE scheme to reveal the true CME signals from the experimental observation. Caveats regarding artificial effects and extreme conditions in this method will also be discussed.

References
1. D.E. Kharzeev et al., Prog. Part. Nucl. Phys. 88 (2016) 1.
2. A. Bzdak et al., Phys. Rev. C 83 (2011) 014905 .
3. L. Adamczyk et al., [STAR Collaboration], Phys. Rev. C 89 (2014) 044908.
4. F. Wen et al., Chinese Phys. C 42(1) (2018) 014001 [arXiv:1608.03205].

Speaker: Dr Gang Wang (UCLA)

QM18poster_ese.pdf

156 An Experimental Handle on the Magnetic Field from Spectator Protons in A+A Collisions

The chiral magnetic effect (CME) and the chiral magnetic wave (CMW) have been predicted to arise from the coupling of domains with quark chirality imbalances in the quark-gluon plasma (QGP) and the strong magnetic field produced by energetic spectator protons. Searches for these quark chirality effects in nucleus-nucleus collisions have been performed at RHIC and the LHC as major scientific goals. For example, the RHIC 2018 run will be devoted to the isobaric collisions of $^{96}$Ru+$^{96}$Ru and $^{96}$Zr+$^{96}$Zr at √s$_{NN}$ = 200 GeV, where one may expect an up-to-20% difference in the experimental observables related to the magnetic-field-induced effects.
Current data indicate that the experimental sensitivity to the chirality effects also depends on the beam energy and the colliding system size, presumably owing to variations in the magnetic field and/or the size of the QGP droplets. Therefore, another venue to enhance the experimental sensitivity could be Au+Au collisions at lower beam energies. We will demonstrate with the AMPT simulations that the number of net protons (N$_{\mathrm{net-p}}$) at mid-rapidity is anti-correlated with the number of spectator protons, and hence provides an excellent handle on the magnetic field from spectator protons in Au+Au collisions at lower RHIC beam energies. Equipped with the event-shape engineering technique [1], the search for chirality effects by varying N$_{\mathrm{net-p}}$ in Au+Au collisions at lower energies (with √s$_{NN}$ still higher than 10 GeV) will complement the isobaric collision data. The future RHIC Beam Energy Scan II program will facilitate the application of our method and discern the true contribution due to the quark chirality effects.

[1] F. Wen et al., Chinese Phys C 42(1) (2018) 014001 [arXiv:1608.03205].

Speaker: Prof. Huan Zhong Huang (Key Laboratory for Nuclear Physics and Ion-Beam Applications (MOE) and Institute of Modern Physics, Fudan University, Shanghai, China, Department of Physics and Astronomy, University of California, Los Angeles, CA 90095, USA.)

Poster_CME_QM.pdf

157 An Initial State with local shear and vorticity for peripheral heavy ion collisions

More than 15 years ago a longitudinal effective string rope model was proposed [1] to construct nucleus-nucleus collision Initial State (IS) for realistic 3+1D relativistic fluid dynamical models. This model reflected correctly not only the energy-momentum, but also angular momentum conservation, initial shear flow, and local vorticity [2]. Recent experimental and theoretical developments indicate that angular momentum, local vorticity and the subsequent particle polarization is observable and provides valuable information: a significant Λ polarization was detected and analyzed in detail in the RHIC BES program [3].

On the other hand, recent developments in parton kinetic and field dominance models provide a rather different initial state configuration, more compact for non-central collisions, see for example [4], what makes us revisit the early IS model [1] in that direction.

We will present a new initial state model for hydrodynamical simulation of relativistic heavy ion collisions, which is based on Bjorken-like solution applied streak by streak in the transverse plane [5]. The proposed model satisfies all the conservation laws including conservation of a strong initial angular momentum which is present in non-central collisions. As a consequence of this large initial angular momentum we observe the fluid shear in the IS, which leads to large flow vorticity. Another advantage of the proposed model is that the initial state can be given in both [t,x,y,z] and [τ, x, y,η] coordinates.

[1] V.K. Magas, L.P. Csernai, D.D. Strottman, Phys. Rev. C64 (2001) 014901; Nucl. Phys. A712 (2002) 167.
[2] L.P. Csernai, V.K. Magas, D.J. Wang, Phys. Rev. C87 (2013) 034906.
[3] L. Adamczyk et al. (The STAR Collaboration), Nature 548 (2017) 62.
[4] L.G. Pang, H. Petersen, G.Y. Qin, V. Roy and X.N. Wang, Nucl. Phys. A956 (2016) 272.
[5] V.K. Magas, J. Gordillo, D.D. Strottman, Y.L. Xie and L.P. Csernai, arXiv:1712.00283 [nucl-th].

Speaker: Prof. Volodymyr Magas (University of Barcelona)

Magas_Poster_QM2018.pdf

158 Angular correlations between heavy and light jet-particles as a means to study in-medium heavy-quark energy loss

Energetic heavy quarks passing through the hot and dense medium of a quark-gluon plasma (QGP), represented by the resulting mesons, are viewed as a suitable probe for the interactions inside of the QGP, in particular the mechanisms of energy loss, as they are less likely to thermalize within the medium and are mostly created at early stages of the medium evolution.
However, models of both, purely collisional energy loss as well as combinations of collisional and radiative energy loss are equally successful for reproducing the nuclear modification factor $R_{AA}$ and the elliptic flow $v_2$ [1]. In an attempt to discriminate between the two different energy-loss mechanisms,an alternative observable, the angular correlations between two mesons were investigated. Azimuthal correlations between pairs of heavy mesons, like $D$-$\bar{D}$ pairs, allow for distinguishing the energy-loss scenarios [2].

We continue these studies by investigating the angular correlations between pairs of heavy and light mesons ($D$ and $\pi$), originating from a heavy quark jet. This is motivated by the fact that the emitted gluon in radiative collisions hadronizes and these hadrons are correlated to the emitting heavy quark.

We created a Monte-Carlo code for the parton splitting in the vacuum together with an effective medium model. This program represents a consistent framework to study the influences of either collisional or radiative processes on parton propagation, and the resulting two-particle correlations. In order to learn at which stages of their space-time evolution jets are affected the most by interactions with the medium we studied contributions to angular correlations from different jet topologies.

[1] P. B. Gossiaux, J. Aichelin, T. Gousset and V. Guiho,
J. Phys. G 37 (2010) 094019
[arXiv:1001.4166 [hep-ph]].

[2] M. Nahrgang, J. Aichelin, P. B. Gossiaux and K. Werner,
J. Phys. Conf. Ser. 509 (2014) 012047
[arXiv:1310.2218 [hep-ph]].

Speaker: Martin Rohrmoser (Jan-Kochanowski University Kielce)

poster.pdf

159 Angular correlations between J/$\psi$ mesons and charged hadrons in proton-proton collisions at $\sqrt{s}$ = 13 TeV with ALICE

Due to the different energy scales involved in the production of charmonium states in proton-proton collisions, they provide important testing grounds for the theory of Quantum Chromo-Dynamics (QCD). The initial charm-quark pairs are produced in large-$Q^2$ processes that allow for a perturbative treatment while the hadronization into a bound system is non-perturbative.

Different effective theories for the description of charmonium production exist, like the Color Singlet Model, the Color Evaporation Model or the non-relativistic QCD approach. However, none of them describes the production cross-sections and the polarization simultaneously. The correlations of J$/\psi$ mesons and hadrons can provide constraints on the color-singlet or color-octet nature of the pre-resonant charmonium state by measuring the amount of hadronic activity in the vicinity of the J$/\psi$.

In this poster, preliminary ALICE results on the angular correlations between inclusive J$/\psi$ mesons and charged hadrons at mid-rapidity in pp collisions at $\sqrt{s} = 13~\text{TeV}$ will be shown. The high multiplicity triggered data taken by ALICE in Run-2 allows for measurements in high multiplicity events, in addition to the analysis of minimum-bias data. Projections for the LHC Run-3 and Run-4 will also be reported. Our measurements will be compared to model calculations.

Speaker: Lucas Altenkamper (University of Bergen (NO))

QM18_poster_JpsiHadronCorrelation_altenkamper.pdf

160 Angular Correlations Study of Identified Hadrons in the STAR Beam Energy Scan Program

The angular correlation function (CF) refers to the correlation of particles in the relative pseudorapidity ($\Delta\eta$) and relative azimuthal angle ($\Delta\phi$). CF is influenced by various physical phenomena such as conservation laws, collective particle flow, resonance decays, final state interactions, or particle production mechanism - e.g., correlation of particles within the single jet. By analysis of long-range correlations (of pairs with $\Delta\eta \geq$1.0) it is possible to access the early stage of the system created during heavy-ion collision and its longitudinal and azimuthal dynamics.

The STAR Beam Energy Scan data allows one to perform a detailed CF analysis to investigate the phase diagram of strongly interacting matter. Recently [1] STAR reported an angular correlation measurements of $\pi$-$\pi$, K-K, and p-p pairs with $\Delta \eta \leq$1 in 0-5% central Au+Au collision at $\sqrt{s_{NN}}$ = 7.7-200 GeV. These results show a significant difference between CF of given particle species combinations.

In this poster, we extend this results to $\Delta \eta \leq\;$2, which allows for analysis of long-range correlations of $\pi$-$\pi$, K-K, and p-p pairs. We describe the data by fitting a multi-component function. Such an approach allows for disentanglement of various correlation sources. The study is conducted in nine centrality classes (70-80%, 60-70%, 50-60%, 40-50%, 30-40%, 20-30%, 10-20%, 5-10% and 0-5%) of Au+Au collisions at $\sqrt{s_{NN}}$ between 7.7 and 200 GeV. The collision energy and centrality dependence of the best fit-to-data function parameters, describing short- and long-range correlations, will be presented.

Reference
[1] S. Jowzaee (for the STAR Collaboration), Nucl. Phys. A967, 792 (2017).

Speaker: Andrzej Lipiec (Warsaw University of Technology)

AndrzejLipiec-QM2018Poster.pdf

161 Anisotropic flow from Initial state geometry in pp collisions at LHC energies.

Anisotropic flow plays a crucial role to characterize the momentum anisotropy of the final state particles. In order to probe the properties of the system created in high multiplicity pp collisions at LHC energies, we study within the percolation color sources, the effects of initial state geometry, profile distribution, size and eccentricity fluctuations in pp collisions at the LHC energies. The results on the higher harmonic flow modes shown how the initial state geometry and the density of color string sources vary significantly the contribution of the higher flow modes (vn) due to the size effect. The correlation of the higher flow harmonics with the corresponding η/s is compared with hydrodynamic calculations.

Speaker: Irais Bautista Guzman (Autonomous University of Puebla (MX))

QM18-0.pdf

162 Anisotropic flow measured in Pb-Pb collisions with the NA49 experiment at the CERN SPS

Anisotropic flow at SPS energies was measured by the NA49 Collaboration more than 10 years ago. Recently new data for Pb-Pb collisions were collected by the NA61/SHINE experiment during the Pb-ion beam energy scan program at the SPS. This motivated a new analysis of the available NA49 data, based on modern flow measurement techniques that will also utilize the spectator fragments for reaction plane determination.

The new results on directed and elliptic flow in Pb-Pb collisions at beam energy of 40 A GeV recorded with the fixed target experiment NA49 at CERN SPS are presented. Event classification is based on the multiplicity of produced particles as well as on the energy of the projectile spectators using the procedure implemented within the Centrality Framework developed for the future CBM experiment at FAIR. To account for the azimuthal asymmetry of the fixed target setup of the NA49 experiment, a three-subevent technique is used for the determination of the reaction plane resolution. The reaction plane is estimated both from the azimuthal asymmetry of the produced particles measured with the NA49 TPCs as well as by using the transverse granularity of the NA49 forward VETO calorimeter. Corrections for the detector acceptance anisotropy in the transverse plane are applied using an extension of the Qn-Corrections Framework developed originally for the ALICE experiment at the LHC.

The results are compared with those previously obtained by the experiments STAR at RHIC and NA49 at the SPS. The new study is complementary to the ongoing analysis of the recently collected Pb-Pb data of the NA61/SHINE experiment at the CERN SPS and provide an important reference for the performance investigations for the future CBM experiment at FAIR.

Speaker: Oleg Golosov (National Research Nuclear University MEPhI (RU))

poster_Golosov.pdf

163 Anisotropic flow of multi-strange particles in Pb--Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV with ALICE

Anisotropic flow plays a critical role in understanding the properties of the quark- gluon plasma. In this poster we present the elliptic and triangular flow of multi-strange particles in Pb--Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV. The measurements are presented at mid-rapidity for a wide range of particle transverse momenta. The results are compared to those for elliptic and triangular flow for other identified hadrons and measurements for Pb-Pb collisions at lower energy.

Speaker: Mr Ya Zhu (Central China Normal University)

poster.pdf

164 Anomalous current from covariant Wigner function

We consider accelerated and rotating media of weakly interacting fermions in local thermodynamic equilibrium on the basis of kinetic approach. Kinetic properties of such media can be described by covariant Wigner function calculated on the basis of relativistic distribution function of particles with spin. We obtain the formulae for axial current by summation of the terms of all the orders over thermal vorticity tensor, chemical potential and temperature arising from the distribution functions under consideration, both for massive and massless particles and calculate axial current divergence. We show, that in the massless limit all the terms, since the fourth order over vorticity and third order over chemical potential and temperature equal zero. It is shown, that axial current gets a topological component along the 4-acceleration vector. The similarity between different approaches to baryon polarisation is established.

Speaker: Mr George Prokhorov

AxialPoster.pdf

165 Application of MVA methods to the analysis of prompt and non-prompt J/$\psi$ in Pb-Pb collisions with ALICE at the LHC

J/$\psi$ mesons and other hadrons containing a charm or a beauty quark are
excellent probes to study the Quark-Gluon Plasma (QGP) produced under
extreme temperature and energy density conditions in heavy-ion collisions. Because of their large mass,
heavy quarks are produced in hard parton-scattering processes at the
beginning of the collisions and they are therefore present in the QGP
during all stages of its evolution.

At mid-rapidity ($|y|<0.8$), ALICE can reconstruct J/$\psi$ mesons via their decay
into the dielectron channel, down to zero transverse momentum $p_{\rm T}$. However,
particularly at very low $p_{\rm T}$ and in central collisions, the measurement is
limited by the low signal to background ratio. Increasing the significance of the
measurement in the low $p_{\rm T}$ region is extremely important for several reasons:
First, in the study of prompt J/$\psi$ production, higher precision will
shed light on the interplay between J/$\psi$ dissociation and regeneration.
Second,
the non-prompt J/$\psi$ analysis can give access to low $p_{\rm T}$ beauty
measurements.

Using multivariate methods helps to reduce the background and increase the
significance while keeping as much signal as possible.
A study of the multivariate methods with data from Pb--Pb collisions at
$\sqrt{s_{\rm NN}}=5.02$ TeV will be presented in this poster. Different
choices of training variables were tested, with respect to background
rejection and good stability of the efficiency corrections.

Speakers: Alena Harlenderova (GSI - Helmholtzzentrum fur Schwerionenforschung GmbH (DE)), Lukas Layer (Ruprecht Karls Universitaet Heidelberg (DE))

poster_MVA_Jpsi.pdf

166 Averaged jet charge as a probe of quark gluon plasma in heavy-ion collisions

Averaged jet charge characterizes the electric charge distribution inside jets, and provides a powerfull tool to distinguish quark jets from gluon jets. In this talk, we give the first prediction for the medium nodification of averaged jet charge in heavy-ion collision at the LHC energy, where the jet productions in $pp$ collisions are simulated by pythia6+FastJet, and parton energy loss effects in the QGP are calculated with two Monte Carlo codes of jet quenching: PYQUEN and JEWEL. In $pp$ collisions, the value of jet charge for quark jets goes up with increasing jet transverse momentum, while for gluon jets it approximates to zero in the whole range of $p_{T}$ because gluon carries no electric charge. It is shown that the distribution of averaged jet charge is significantly suppressed by initial state nuclear effects due to the participants of neutrons with zero electric charge during nuclear collisions. Considerable enhancement of averaged jet charge in central $PbPb$ collisions relative to peripheral collisions is observed, since jet quenching effect is more pronounced in central collisions. In the jet quenching calculations, a fast gluon will lose more energy in the QGP than a fast quark due to its large color-charge($\Delta E_{g}/\Delta E_{q}=C_{A}/C_{F}=9/4$), more quarks with electric charge may survive in central collisions as compared with that in peripheral $PbPb$ collisions. The fraction of quark jet will be increased, which results in the larger value of averaged jet charge in central collisions than that in peripheral reactions. Distinct feature of averaged jet charge between quark and gluon jets, together with the sensitivity of jet charge alternations to flavour dependence of parton energy loss, could be very useful to discriminate the energy loss pattern between quark and gluon jets in heavy-ion collisions.

Speaker: Dr Shi-Yong Chen (Central China Normal University)

167 Azimuthal anisotropy of b$\rightarrow$e and c$\rightarrow$e in 200 GeV Au+Au collisions at RHIC-PHENIX

Heavy quark yields is a powerful tool to study the quark gluon plasma (QGP)
created in high energy heavy ion collisions.
PHENIX separated electrons from the charm and bottom decays by measuring the distance of the closest approach with the silicon vertex detector, and found the suppression of bottom quarks is smaller than that of charm quarks at low $p_T$. Heavy quark measurements also show a strong coupling with the QGP medium. It is important to measure the the flow of bottoms and charms separately.
In this poster, we present the analysis method and current status of b$\rightarrow$e and c$\rightarrow$e flow measurement at mid-rapidity in Au+Au 200GeV collisions with the PHENIX detector

Speaker: Dr Takashi Hachiya (RIKEN)

QM2018poster_hachiya_v3.pdf

168 Azimuthal anisotropy of high $p_T$ hadrons via long-range two particle correlations in d+Au and p+p collisions by PHENIX

PHENIX measured two-particle angular correlations between high $p_T$ ($2 < p_T < 11 $ GeV/c) $\pi^{0}$ at midrapidity $|\eta| < 0.3 $ and hadrons emitted at
forward $(3.1<\eta<3.9)$ or backward $(-3.7<\eta<-3.1)$ rapidity in 200 GeV
p+p and d+Au collisions at $\sqrt{s_{NN}}$=200 GeV. In the Au-going direction the azimuthal correlations of these particle pairs with this large rapidity gap exhibit a ridge-like structure. This structure persists up to $p_{T} \approx 6$ GeV/c and strongly depends on collision centrality. It is reminiscent of collective behavior in A+A collisions. The ridge-like structure is absent in the d-going direction as well as in p+p collisions.

We present the final results of two particle correlations with a large rapidity
gap in 200 GeV d+Au and p+p collisions and discuss the physics implication of
the results.

Speaker: Brett Fadem

qm2018_BF_azimuthal_02.pdf

169 Azimuthal correlations of D0 mesons with charged particles in pp collisions at $\sqrt{s}$ = 13 TeV with the ALICE experiment at the LHC

The ALICE experiment at the Large Hadron Collider (LHC) is dedicated to study the properties of the Quark-Gluon Plasma (QGP), a de-confined state of strongly-interacting partons formed in relativistic heavy-ion collisions. Heavy quarks, produced by parton-parton hard scatterings in the early stages of such collisions, stand out as unique probe to study the QGP, as they are expected to experience the whole evolution of the system formed in the collision.\

The azimuthal correlations between heavy-flavour particles and charged particles give insight on the modification of charm-jet properties in nucleus-nucleus collisions and the mechanisms through which heavy quarks lose energy inside the medium. Studies in pp collisions are necessary as a reference for nucleus-nucleus collisions and also important for testing expectations from pQCD-inspired Monte Carlo generators. In this contribution, we will present the first study of azimuthal correlations of $D^{0}$ mesons with charged particles in pp collisions at $\sqrt{s}=13$ TeV, so far the highest available energy at the LHC, performed with the ALICE apparatus. A comparison with pp collisions results at $\sqrt{s}=7$ TeV will help to evaluate the energy dependence of the correlation function. Data will also be compared with expectations from POWHEG and PYTHIA event generators.

Speaker: Ms Samrangy Sadhu (Department of Atomic Energy (IN))

QM_final.pdf

170 Azimuthally sensitive femtoscopy with sorted events

In the first part of the talk we shall investigate how the averaging
over a large number of events influences the shape of the observed
correlation function. We demonstrate that a shape characterised by Levy
distribution may result from an average over Gaussian sources with
varying sizes and orientations. We then propose to sort the events
according to their similarity and investigate azimuthal dependence of
the correlation radii on events classes which differ in shape. The
method is explained and demonstrated on events simulated with different
event generators.

Speaker: Jakub Cimerman (Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University)

poster.pdf

171 Baryon clustering near a (hypothetical) QCD critical point II

To understand the dynamics of cluster formation, starting from homogeneous distribution, we set up classical molecular dynamics simulation of the baryon motion, supplemented by a Langevin equation to model the effect of a meson heat bath. Quantum mechanical kinetic energy is included via an effective potential, tuned to reproduce known properties of nuclear matter. We then modify the inter-nucleon potential, in a way expected in the vicinity of the hypothetical QCD critical point, and calculate the rate of baryon cluster formation. Then we compare it with the time available in real heavy-ion collisions.

Speaker: Dr Juan M Torres-Rincon (Stony Brook University)

Torres-RinconQM18.pdf

172 Baryon-(anti-)baryon and baryon-meson interaction cross-section measurement with femtoscopy technique in heavy-ion collisions

Interaction cross-sections for baryon pairs are of fundamental interest
and they are actively investigated theoretically. They are known well for
pairs of common (anti-)baryons, however there is a lack of precise
data for heavier baryons, including the ones carrying strangeness. The
so-called kaonic atoms are also investigated theoretically and their
properties crucially depend on the kaon-nucleon interaction. The
two-particle correlation formalism (femtoscopy) is sensitive to the
interaction kernel for a pair of particles, which is related to the
pair interaction cross-section [1]. The formalism is extensively used
to measure two-particle correlations in heavy-ion collisions. In
particular the collisions at RHIC and LHC produce simultaneously large
number of baryons and anti-baryons and even larger number of kaons. We
show how this formalism can be used to extract the cross-sections from
the femtoscopic baryon-(anti-)baryon correlation functions [2], as
well as from proton-charged kaon functions. The analysis is
complicated by the presence of the so-called "residual correlations"
arising from weak decay products in the measured sample. We show how
this effect can be exploited to gain further insight into the
cross-sections of even heavier baryons. We discuss the limitations of
the measurement technique and estimate the discovery potential of
currently available and soon-to-be-collected heavy-ion collision
datasets at RHIC and at the LHC.

[1] A. Kisiel, H. Zbroszczyk, M. Szymanski; "Extracting
baryon-antibaryon strong interaction potentials from pΛ¯ femtoscopic
correlation functions"; Phys.Rev. C89 (2014) 5, 054916
[2] R. Lednicky, V.L. Lyuboshits; "Final State Interaction Effect on
Pairing Correlations Between Particles with Small Relative Momenta";
Sov.J.Nucl.Phys. 35 (1982) 770, Yad.Fiz. 35 (1981) 1316-1330

Speaker: Adam Kisiel (Warsaw University of Technology (PL))

PosterQM2018.pdf

173 Bayesian analysis of the temperature- and momentum-dependence of the heavy flavor diffusion coefficient

Recent years have seen significant theoretical progress in the transport description of open heavy flavor in QCD matter -- a number of models are now able to simultaneously describe a subset of the most important heavy flavor observables -- a simultaneous description of a comprehensive set of observables at all available collision energies still poses a challenge. A global analysis encompassing all available collision systems and energies as well as an improved treatment of known uncertainties for different observables would significantly improve our ability to distinguish between different theoretical models and constrain the heavy flavor diffusion coefficient in an unbiased way.

In this study, we show that describing the heavy quark energy loss with Langevin diffusion and a radiative energy loss component in a state-of-the-art hydrodynamic medium, including heavy meson hadronic interactions modeled with UrQMD allows for a simultaneous description of the $D$-meson $R_{\mathrm{AA}}$ and $v_n$ at both RHIC (200 GeV) and the LHC (2.76 \& 5.02 TeV) energies. The heavy flavor interaction with the quark-gluon plasma is encoded in the diffusion coefficient, which is calibrated on experimental measurements using a systematic model-to-data Bayesian analysis. The estimated diffusion coefficient $D_sT$ has a positive temperature dependence and a non-trivial momentum dependence. The constrained diffusion coefficient is validated by comparing $D$-meson $R_{\mathrm{AA}}$ in pPb collisions along with $B$-meson measurements. New observables are proposed to further constrain the diffusion coefficient.

Speaker: Yingru Xu (Duke University)

Bayesian_YingruXU_QM2018_v3.pdf

174 Bayesian unfolding of charged particle $p_{\mathrm{T}} $ spectra with ALICE at the LHC

The study of the Quark-Gluon Plasma created in ultrarelativistic heavy-ion collisions at the CERN-LHC is complemented by reference measurements in proton-lead (p--Pb) and proton-proton (pp) collisions, where the effects of multiple-parton interactions and hadronization beyond independent string fragmentation can be investigated.

In this poster, we present a Bayesian unfolding procedure
to reconstruct the correlation between transverse momentum ($p_{\mathrm{T}} $) spectra of charged particles and the corresponding charged particle multiplicities $N_{\mathrm{ch}}$.
The unfolded spectra are presented in single multiplicity ($\Delta N_{\mathrm{ch}}$ = 1) bins and are used to derive moments of the $p_{\mathrm{T}} $ distributions.

We illustrate the unfolding procedure of the $p_{\mathrm{T}} $ spectra
with MC simulations for pp collisions and compare the resulting $\langle p_{\mathrm{T}}\rangle $ of different systems (pp, p--Pb, Pb--Pb) and collision energies.

Speaker: Mario Kruger (Johann-Wolfgang-Goethe Univ. (DE))

Poster_BayesianUnfolding_QM18.pdf

175 Beam Energy and Collisions System Dependence of Charge Separation Relative to the Second-, Third- and Fourth-order Event Planes and the Implications for the Search for Chiral Magnetic Effects in STAR

We present new differential measurements of charge separation relative to the second- ($\Psi_2$), third- ($\Psi_3$) and fourth-order ($\Psi_4$) event planes for Au+Au collisions at $\sqrt{s_{NN}}$= 200, 39, 27 and 19.6~GeV, U+U at $\sqrt{s_{NN}}$= 193 GeV and Cu+Au, Cu+Cu, d+Au and p+Au at $\sqrt{s_{NN}}$=200 GeV. The measurements are performed with a charge-sensitive correlator $R(\Delta S)$ [1] and the three-particle mixed harmonic correlator $\mathrm{C_{m,n,m+n} = \left< cos(m\phi_1 + n\phi_2 -(m+n)\phi_3)\right>}$ [2]. These are expected to give different responses to the CME-driven charge separation and non-CME background correlations. The $R(\Delta S)$ measurements are found to be flat relative to $\Psi_3$ in all systems and $\Psi_2$ in p(d)+Au systems, consistent with the expectation of random $\vec{B}$-field orientations relative to these event planes. In contrast, the heavy-ion measurements relative to $\Psi_2$ show concave-shaped $R(\Delta S)$ distributions, which is consistent with the presence of CME-driven charge separation characterized by an out-of-plane Fourier dipole coefficient $a_1$. We will present and discuss $R(\Delta S)$ and $\mathrm{C_{m,n,m+n}}$ measurements for a broad range of transverse momenta, pseudorapidity, and centrality intervals and compare it with model predictions [1]. The implication of these measurements for the upcoming isobar collisions at RHIC will also be discussed.

References
[1] N. Magdy, S. Shi, J. Liao, N. Ajitanand, and R. A. Lacey, arXiv:1710.01717.
[2] L. Adamczyk et al. (STAR Collaboration), arXiv:1701.06496.

Speaker: Niseem Abdelrahman"Magdy" (Stony Brook University)

QM18poster_CME_R.pdf

176 Beam Energy Scan program with EPOS model

Studies of collisions of highly accelerated ions are the key to understand the creation of quark matter. Experimental physicists put considerable effort in collecting information characterizing the various processes occurring during such collisions. In order to describe such scenarios, complex models have been constructed, one of them being the EPOS approach. It applies Parton-based Gribov-Regge theory as an initial condition, introduces the core-corona approach, hydrodynamical evolution and hadronic cascades as well. The model is used by the experimental physicist at the LHC or in cosmic ray physics.

At the Brookhaven National Laboratory, the STAR collaboration is currently investigating an interesting project called Beam Energy Scan. The QCD phase diagram is studied in order to understand the phase transitions close to the critical point, which should be in the energy domain studied in this program. Models have difficulties to describe this energy range properly. The aim of our investigation is to adapt the EPOS model to describe correctly collisions of ions with energies studied in the framework of the BES program.

The detailed description of the theory included in EPOS model will be presented. The energy dependence of the separation into the core and corona will be discussed, and the way it affects transverse momentum spectra of identified particles and the observables of the azimuthal anisotropy of expanding matter. The particles from the corona are strongly affected by the radial flow and the flow asymmetries. The results of different types of analysis of elliptic flow will be discussed. The simulation results for collisions of Au+Au at selected BES energies will be presented in comparison with the published STAR data.

Speaker: Maria Stefaniak (Warsaw University of Technology)

qm_maria_stefaniak.pdf

177 Beauty production via non-prompt $D^0$ from CMS in pp and PbPb collisions at 5.02 TeV

Heavy quarks are unique probes to study the medium created in heavy-ion collisions. Detailed measurements of the production of bottom hadrons can supply information crucial to understanding the properties of the strongly interacting QCD matter and the flavor dependence of parton energy loss. In this poster, the measurement of transverse momentum spectra of $D^0$ from beauty-hadron decays in pp and PbPb Collisions at 5.02 TeV performed by the CMS collaboration is presented. The $D^0$ from B decay are distinguished from prompt $D^0$ by their different geometrical distributions relative to the collision point, due to the large decay length of B meson. The measured spectrum in pp collisions is compared to perturbative QCD calculations. The Nuclear Modification Factor ($R_{AA}$) of $D^0$ from B decay will also be reported, comparing with prompt $D^0$, light flavor hadrons, as well as model predictions.

Speaker: Wei Xie (Purdue University (US))

QM18poster_BtoD_QiuHao.pdf

178 Benchmark of microscopic hadronic direct photon emission in thermal equilibrium

Cross sections for direct photon production in hadronic scattering processes have been calculated according to an effective chiral field theory following Turbide et al. For $\ \pi + \rho \rightarrow \pi + \gamma$ and $\ \pi + \pi \rightarrow \rho + \gamma$ processes, these cross sections have been implemented into a novel hadronic transport approach (SMASH), which is suitable for collisions at low and intermediate energies. Comparisons of the obtained thermal rates in infinite matter calculations to theoretical predictions and to the ones used in hydrodynamic calculations are shown. This constitutes a benchmark for future non-equilibrium calculations. Employing SMASH for the final state rescattering in a hybrid approach will allow to assess the importance of the hadronic stage in the generation of direct photon flow.

References:
J. Weil et al, “Particle production and equilibrium properties within a new hadron transport approach for heavy-ion collisions”. In: Phys. Rev C 94 (2016) no. 5, 054905
Simon Turbide, Ralf Rapp, and Charles Gale. “Hadronic production of thermal photons”. In: Phys. Rev. C69 (2004), p. 014903

Speakers: Ms Anna Schäfer (Frankfurt Institute for Advanced Studies (FIAS)), Mr Jonas Rothermel (Goethe University Frankfurt)

QM_Poster.pdf

179 Bjorken expansion with gradual freeze out via HBT

For Bjorken models with gradual freeze out, the resulting post freeze out momentum distribution practically does not depend on the layer thickness. Using such a model we calculate the pion correlation function produced in Pb+ Pb central collisions The correlation function is in qualitative agreement with other publications but our model allows us to perform a more detailed study of how this affects the final observables. We also find a good agreement with experimental data from ALICE and we deduce that long freeze out averaged correlation functions are more similar to experimental data than sharp freeze out.

Speaker: Marc Borrell Martinez

Poster.pdf

180 Bulk observables within hybrid approach for heavy ion collisions, at RHIC and the LHC, with SMASH afterburner

We present a model of the dynamical evolution of relativistic heavy ion collisions, which combines second-order viscous hydrodynamics and microscopic transport. In particular, we present a hybrid approach with MUSIC hydrodynamics, particlization with improved treatment of resonance masses based on spectral functions, and SMASH (Simulating Many Accelerated Strongly-interacting Hadrons) afterburner. In this work, we focus on low-$p_T$ hadronic observables --- identified hadron $p_T$ spectra and anisotropic flow coefficients. Given that the low-$p_T$ bulk dynamics in hadronic re-scattering is dominated by resonance excitations and decays, it is expected that implementation of mass sampling at the particlization and better treatment of resonances in microscopic transport play important roles in the late stage of heavy ion collisions. This motivates us to compare other hybrid approaches, such as MUSIC+UrQMD, to MUSIC+SMASH hybrid with an emphasis put on the importance of mass sampling at the particlization and effect of hadronic re-scatterings.

Speaker: Dr Sangwook Ryu (Goethe-Universität Frankfurt (FIAS))

Poster_SRYU_QM2018.pdf

181 Can Baryon Stopping be understood within the String Model?

Baryon stopping, experimentally established by the changing shape of net-proton rapidity distributions as a function of beam energy, is still lacking a proper theoretical understanding. In this work, baryon stopping in heavy ion collisions is investigated. In a hadronic transport approach the colliding nucleons form a string, which fragments, producing new hadrons. From the comparison with data, it is possible to fix parameters of the string model (for example the formation time of the produced hadrons) and to find out whether baryon stopping can be described within the string model or other mechanisms are needed.

Speaker: Justin Mohs

poster_justin.pdf

182 Canonical partition functions, virial expansion and the critical point(s) of QCD

We study the interplay of the fugacity expansion for the Grand Canonical Partition Function, and the Taylor and virial expansion for the number density. We compare results from the Vladivostok group lattice QCD study [1], and from a toy model of QCD with the predictions of a Cluster Model Expansion. We outline different strategies for the search of singularities in the complex chemical potential plane, including a possible QCD critical point for real chemical potential.

[1] V.G.Bornyakov, D.L.Boyda, V.A.Goy, A.V.Molochkov, A.Nakamura, A.A.Nikolaev and V.I.Zakharov,
Phys.Rev.D95(2017)9,094506

Speaker: Maria Paola Lombardo (INFN)

QM2018_poster_mpl.pdf

183 Causal Charge Diffusion and Fluctuations in Heavy-Ion Collisions

We present a relativistic causal description of conserved-charge diffusion for heavy-ion collisions and show that it produces measurable effects in observables such as the charge balance functions. Other descriptions, based on ordinary diffusion, are known to produce charge fluctuations which propagate with infinite velocity, thus violating a fundamental postulate of special relativity. We present an alternative approach based on Cattaneo diffusion which restores relativistic causality, and show how to generalize this approach to dynamical, rapidly evolving systems such as heavy-ion collisions. We demonstrate that this approach leads to measurable consequences for the balance functions constructed from electrically charged hadrons in a simple 1+1 dimensional Bjorken hydrodynamic model. We find that limiting the speed of propagation of charge fluctuations increases the height and reduces the width of these balance functions when plotted versus separation in rapidity. We conclude by estimating the numerical value of the associated diffusion time constant from AdS/CFT.

Speaker: Christopher Plumberg

QM2018_Plumberg_Poster_portrait.pdf

184 Causality as a bound to fluid dynamics

Dissipative relativistic fluid dynamics is not always causal. We discuss the causality structure of high energy nuclear collisions. When the fluid evolution equations are hyperbolic, one can bring them to a characteristic form describing the radial expansion of the fireball. This dynamics is causal if the characteristic velocities are smaller than the speed of light such that the domain of dependence of a space-time point is within its past light cone. Within the second order theory of Denicol, Niemi, Molnar and Rischke, we obtain a concrete inequality from this constraint and discuss how it can be violated for certain initial conditions sometimes used in phenomenological studies. We argue that causality poses an important bound to the applicability of relativistic fluid dynamics in particular at very early times.

Speaker: Eduardo Grossi (Heidelberg University)

185 Centrality and Transverse Momentum Dependences of D0-meson and D±-meson Production at Mid-rapidity in Au+Au Collisions at $\sqrt{s_{NN}}$ = 200 GeV at STAR

Due to their large masses, heavy quarks are considered to be an excellent probe to study the properties of the quark gluon plasma through their interactions with the medium. In this presentation, we report on improved measurements, achieved by using supervised machine learning technique, of $D^0$-meson and $D^{\pm}$-meson transverse momentum ($p_{\rm T}$) spectra at mid-rapidity ($|y|<$1) in Au+Au collisions at $\sqrt{s_{_{\rm NN}}}$ = 200$\ $GeV. The data were taken in 2014 by the STAR experiment with the Heavy Flavor Tracker, a high resolution silicon vertex detector. $D^0$ and $D^{\pm}$ mesons are measured through their hadronic decay channels, $D^0\rightarrow K^-+\pi^+$ and $D^{\pm}\rightarrow K^\mp+\pi^\pm+\pi^\pm$, via topological reconstruction of the secondary decay vertices. After being corrected for the detector acceptance, tracking and topological cut efficiencies, invariant yields of $D^0$ and $D^{\pm}$ mesons are presented in various centrality intervals covering a wide transverse momentum region (0 $<$ $p_T$ $<$ 10 GeV/$c$). The charmed hadron freeze-out properties and radial collectivity are discussed within the Blast-Wave model. Nuclear modification factors ($R_{\rm CP}$, $R_{\rm AA}$) in various centrality bins are calculated and compared to phenomenological model calculations.

Speaker: Guannan Xie (University of Illinois at Chicago)

QM18poster_D0_GX_0510_2.pdf

186 Centrality dependence study of nuclear modification factor of electrons from heavy-flavour hadron decay in p-Pb collisions with ALICE at the LHC

The goal of relativistic heavy ion collider experiments is to explore the properties of the strongly interacting matter produced with very high temperature and energy density, conditions under which the formation of a Quark-Gluon Plasma (QGP) is expected. Heavy quarks, i.e. charm and beauty are sensitive probes of the QGP as they are produced in the initial stages of the collision and witness the entire evolution of the system. Measurements in p-Pb collisions help understanding Cold Nuclear Matter (CNM) effects such as the modification of the nuclear Parton Distribution Function (nPDF) with respect to the expectation from proton PDF, parton momentum ($k_{\rm T}$) broadening from soft scattering processes and parton energy loss in nuclear matter. Studies of heavy-flavour production in different centrality intervals can provide information on the dependence of CNM effects on the collision geometry and on the density of final-state particles. In addition, these allow us to study the interplay between the hard and soft processes in heavy-flavour production. In this contribution, we will present the $p_{T}$-differential cross-section of heavy-flavour decay electrons for different centrality intervals in p-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV at mid-rapidity ($|\eta| <$ 0.8). The Time Projection Chamber (TPC) was used to identify the electrons in 2 $< p_{T} <$ 8 GeV/c and the Electromagnetic Calorimeter (EMCal) was used to extend the $p_{T}$ range up to 16 GeV/c. The nuclear modification factor, $Q_{pPb}$, ratio of transverse momentum spectra in p-Pb collisions and the corresponding cross section in pp collisions scaled by the nuclear overlap function, and the central-to-peripheral ratio $Q_{cp}$, ratio of transverse momentum spectra measured at central collisions to that from peripheral collisions, scaled by the corresponding nuclear overlap functions, will be presented for different centrality intervals of p-Pb events.

Speakers: Sudipan De (Indian Institute of Technology Indore (IITI)), Shingo Sakai (University of Tsukuba (JP))

Poster_QM2018_HFE_pPb_Sudipan.pdf

187 Charged particle spectra in Xe--Xe collisions at $\sqrt{s_{{\text{NN}}}}=$ 5.44 TeV measured with ALICE

The ALICE experiment at the LHC is designed to investigate the properties of the Quark-Gluon Plasma by studying high-energy pp, p-Pb, Pb-Pb and also in the recently for the first time recorded Xe-Xe collisions. Medium effects like parton energy loss can be examined by measuring the production of charged particles and their nuclear modification factor at high transverse momentum ($\textit{p}_{\text{T}}$).
In this poster, we present the analysis of $\textit{p}_{\text{T}}$-spectra for primary charged particles as well as the nuclear modification factor ($R_{\text{AA}}$) in Xe-Xe collisions at $\sqrt{s_{\text{NN}}}=$ 5.44 TeV measured with ALICE. In particular, we focus on a comparision of the nuclear modification factor in Pb-Pb and Xe-Xe collisions to investigate a possible system size dependence of $R_{\text{AA}}$.

Speaker: Patrick Huhn (Johann-Wolfgang-Goethe Univ. (DE))

QM18_Poster_PatrickHuhn_ChargedParticlesXeXe.pdf

188 Charged Particle Yields and Anisotropic Flow at Forward Rapidities from Au+Au Collisions at 54 GeV Using the STAR Event Plane Detector

The Event Plane Detector (EPD) is an upgrade to the STAR experiment that will significantly improve event plane resolution and provide a measure of collision centrality at forward rapidity ($2.1<|\eta|<5.1$). The complete detector, composed of two scintillator wheels at $\pm\eta$ and 2.1$<$$|\eta|$$<$5.1, will be operational in the 2018 run, but in 2017, a quarter of one wheel was commissioned. Results from this run including the partial EPD from Au+Au collisions at $\sqrt{\rm s_{\rm NN}}$$=$54 GeV will be presented. The track densities at this energy are considerably higher than those expected for RHIC Beam Energy Scan energies ($\sqrt{\rm s_{\rm NN}}$$\leq$20 GeV) for which the detector was originally designed. Nevertheless, the detector performed very well in this higher density environment. Preliminary pseudorapidity distributions and anisotropic flow ($v_1$ and $v_2$) results will be shown for forward rapidities measured by the EPD during the 2017 run.

Speaker: Isaac Upsal (Ohio State University)

upsal_QM18poster_v7.pdf

189 Charmonium Suppression within a quasi particle picture

We have investigated the properties of charmonium states through the in- medium modifications to both perturbative and nonperturbative term of the Cornell potential. We have then extended our exploration of quarkonium to a medium which exhibits a local anisotropy in the momentum space. For that, we have first visited the anisotropic corrections to the retarded, advanced and symmetric propagators through their self-energies in the hard-loop resummation technique and apply these results to calculate the medium corrections to the perturbative and nonperturbative term of the Cornell potential. The flavor dependence of the binding energies of the heavy quarkonia states and the dissociation temperature for isotropic as well as anisotropic case have been obtained by employing the Debye mass for pure gluonic and full QCD case, which is computed by employing the quasi-particle picture. Finally we observe that overall the anisotropy makes the dissociation temperatures higher, compared to isotropic medium. By using these dissociation temperatures as an input we further explore the sensitivity of prompt and sequential suppression of these states to the shear viscosity-to-entropy density ratio, η/s from perturbative QCD and AdS/CFT predictions. Our results show excellent agreement with the recent experimental results at LHC energy.

Speaker: Indrani nilima

190 Clusters and Hypernuclei production within PHQMD+FRIGA model

We present for cluster produced with the new combined PHQMD+FRIGA model for Nuclotron and NICA energies. PHQMD is a new n-body approach to simulate heavy ion collisions starting from FAIR/NICA energies. The FRIGA clusterisation algorithm, which can be applied to n-body transport approaches, is based on the simulated annealing technique to obtain the most bound configuration of fragments and nucleons. This configurations is close to the finally observed configuration.
The PHQMD+FRIGA model is able to predict isotope yields as well as hyper-nucleus production.

Speaker: Viktar Kireyeu (Joint Institute for Nuclear Research (RU))

QM_poster_Kireyeu.pdf

191 Collision Energy and Centrality Dependence of Light Nuclei (Triton) Production at RHIC with the STAR Experiment

In high-energy nuclear collisions, light nuclei provide a unique tool to explore the QCD phase structure. The production of light nuclei is sensitive to the temperature and phase-space density of the system at freeze-out. In addition, phase transition will lead to large baryon density fluctuations, which will be reflected in the light nuclei production. For example, the ratio of proton ($N(p)$) and triton ($N(t)$) to deuteron ($N(d)$) yields, which is defined as $N(t)\cdot$N(p)/$N^{2}(d)$ , may be used as a sensitive observable to search for the QCD critical point [1].

In this poster, we will report the first results of the collision energy and centrality dependence of triton production in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 7.7, 11.5, 14.5, 19.6, 27, 39, 62.4 and 200 GeV, measured by the STAR experiment at RHIC. We will present the beam energy dependence of the coalescence parameter $B_3(t)$, directed flow ($v_1$) of light nuclei (d, t, ${}^3$He), and the yield ratio $N(t)\cdot$N(p)/$N^2(d)$. We will also show the energy dependence. Their physics implications will be discussed.

Reference
[1] K.J. Sun, L.W. Chen, C.M. Ko and Z.B. Xu, Phys. Lett. B 774, 103 (2017), arXiv:1702.07620.

Speaker: Mr Dingwei Zhang (Central China Normal University)

QM18poster_Dingwei.pdf

192 Comprehensive study of hadron production from small to large systems by PHENIX

The mass dependence of anisotropic flow as a function of $p_T$ in small systems
observed at both RHIC and the LHC provided strong evidence of collective
behavior and suggests the formation of the smallest QGP droplets in these systems. If the cause of this mass dependence is indeed radial flow, this should be reflected in the spectral shapes at low $p_T$. Further, one would expect hard scattered partons to lose energy in these QGP droplets.
PHENIX has measured particle production from a broad set of projectile-target
combinations including p+Au, d+Au, $^{3}$He$+$Au, Cu+Cu, Cu+Au, Au+Au, and U+U. At low $p_T$ the spectra can reveal how radial flow emerges with system size. At high $p_T$ they carry information about energy loss.

We will present a comprehensive study of identified pion, kaon, proton, and
$\eta$ spectral shapes and nuclear modification factors as a function of system size and discuss the implications about radial flow and in-medium energy loss.

Speaker: Richard Seto (University of California, Riverside)

Seto_poster_QM2018 fixed_reduced.pdf

193 Computation of the Berry curvature in lattice QCD

The Berry curvature is a fundamental quantity to describe the chiral magnetic effect and chiral kinetic theory. While it can be analytically tractable in non-interacting systems, numerical simulations are necessary in interacting systems. We formulated the lattice simulation to calculate the Berry curvature in interacting systems. We present the first result in quenched lattice QCD.

Speaker: Arata Yamamoto

20180515Venice.pdf

194 Confinement/deconfinement phase transition in dense medium

Confinement/deconfinement phase transition in dense medium

In this talk we report the lattice observation of deconfinement in dense matter. The study of the deconfinement transition was conducted within lattice simulation of dense two-color QCD at zero temperature. We reach very large baryon density (up to quark chemical potential $\mu_q > 2000 \mathrm{~MeV}$). In the region $\mu_q\sim 1000 \mathrm{~MeV}$ we observe for the first time the confinement/deconfinement transition which manifests itself in a rising of the Polyakov loop and vanishing of the string tension. After the deconfinement at $\mu_q > 1000 \mathrm{~MeV}$ we observe a monotonous decrease of the spatial string tension which ends up with its vanishing at $\mu_q > 2000 \mathrm{~MeV}$. From this observation we draw the conclusion that the confinement/deconfinement transition at finite density and zero temperature is quite different from that at finite temperature and zero density. Our results indicate that in very dense matter the quark-gluon plasma is similar to a weakly interacting gas of quarks and gluons without magnetic screening mass in the system, sharply different from a quark-gluon plasma at large temperature. Implications of our results to properties of real QCD are briefly discussed.

Speaker: Andrey Kotov

qm2018.pdf

195 Constraining heavy-flavour production mechanisms with dielectrons in pp collisions at $\sqrt{s}$ = 13 TeV with ALICE

Correlated electron-positron pairs produced in heavy-ion collisions provide an excellent probe of the hot and dense strongly-interacting medium, i.e. the Quark-Gluon Plasma (QGP), created in such systems. They are produced at all stages of the collision without significant final-state interactions. Moreover, thermal radiation from the medium, both during the partonic and the hadronic phase, can be investigated through its internal conversion to e+e- pairs. In the intermediate mass region (1.2 – 2.8 GeV/c2), the measurement of thermal dileptons from the QGP is nevertheless challenging due to the dominant contribution from simultaneous semileptonic decays of correlated open heavy-flavour hadrons. The continuum yield in this mass region is sensitive to the energy loss of charm and beauty quarks in the QGP and further medium effects on the heavy-flavour hadron production. In order to understand the resulting modifications of the dielectron spectrum in heavy-ion collisions, a good understanding of the relevance of the various heavy-quark production mechanisms in proton-proton collisions is mandatory.

In this poster, the latest dielectron invariant-mass spectrum measured with ALICE in pp collisions at √s = 13 TeV is used to study the charm production mechanisms implemented in PYTHIA event generator. It will be shown how the relative importance of these processes can lead to model dependencies of the extracted charm cross section from a fit of the data.

Speaker: Anisa Dashi (Technische Universitaet Muenchen (DE))

ADashi_Poster_QM18.pdf

196 Constraining the QCD equation of state with identified particle spectra

The equation of state is one of the fundamental properties of the QCD matter created in relativistic nuclear collisions. Lattice QCD simulations now provide a realistic equation of state at vanishing density, but it may differ from what we should see in the experiments because heavy-ion systems may be out of chemical equilibrium, in strong magnetic fields and affected by finite size effects. It is thus important to understand the imprints of the equation of state on the data.

We find that the mean transverse mass as a function of the multiplicity density reproduces, up to proportionality factors, the energy over entropy ratio as a function of the entropy density [1]. We perform viscous hydrodynamic simulations using a variety of equations of state and compare the results to the experimental data. The equations of state with the effective number of degrees of freedom equal to or larger than that of lattice QCD are favored. We also discuss how we can constrain the equation of state at finite baryon density.

[1] A. Monnai and J.-Y. Ollitrault, Phys. Rev. C 96, 044902 (2017), arXiv:1707.08466 [nucl-th]

Speaker: Dr Akihiko Monnai (Institut de Physique Théorique, CNRS/CEA)

qm18_monnai_poster.pdf

197 Constructing probability density function of net-proton multiplicity distributions using Pearson curve method

One of the main goals of Beam Energy Scan program of Relativistic Heavy-ion collision experiment is to map the QCD phase diagram. Measurement of higher order cumulants of net-proton and net-charge distributions are regarded as one of the potential tools to locate the QCD critical point in the phase diagram. Knowing the probability distributions of net-proton are useful for quark-meson (QM) model within the functional renormalization group approach to study the O(4) criticality. However, there are a lot of challenges to eliminate the detector effect from the experimentally measured distributions. In this poster, we will discuss the Pearson curve method to construct the efficiency corrected probability distribution of net-proton from the experimental results of STAR experiment. Furthermore, the beam energy dependence of sixth and eighth order cumulants estimated from the constructed distributions will be discussed. The predicted cumulants ratio results will be compared with various statistical models.

Speaker: Dr Nirbhay Kumar Behera (Inha University (KR))

posterQM2018.pdf

198 Construction and beam test results of the sPHENIX EMCal Prototype

Construction and beam test results of the new prototype of electromagnetic calorimeter (EMCal) module for the sPHENIX detector are presented. sPHENIX will collect high statistics proton-proton, proton-nucleus and nucleus-nucleus data at the Relativistic Heavy Ion Collider (RHIC) from the early 2020's. The sPHENIX capabilities will enable investigations of jet modification, upsilon suppression and open heavy flavor production to probe the nature of Quark Gluon Plasma, and will allow a broad range of cold QCD studies. The EMCal will be the principal sub detector for identification of photons and electrons. Prototype EMCAL modules have been constructed by embedding scintillating fibers into a tower of Tungsten powder and epoxy. Performance results obtained from a run at the Fermilab Test Beam Facility in Feb 2018 will be discussed.

Speaker: Yongsun Kim (Univ. Illinois at Urbana Champaign (US))

199 Construction of the STAR Event Plane Detector

The Event Plane Detector (EPD) is an upgrade to the STAR experiment. It is similar to the Beam Beam Counter (BBC) which has been a part of the STAR experiment since the beginning, but will provide more pseudorapidity coverage ($2.2<|\eta|<5.1$ compared to $3.3<|\eta|<5.0$) and higher granularity (744 distinct channels compared to 32), leading to an increase in first-order event plane resolution by a factor of at least 1.5. Additional benefits from the EPD include TPC-independent centrality determination and event planes at BES energies where the VPD and ZDC suffer from low occupancies. The EPD is a set of disks consisting of 1.2cm-thick scintillator tiles optically isolated with reflective epoxy and embedded with wavelength-shifting fibers held in place with optical epoxy which are coupled to Silicon photomultipliers via clear fiber optics. The detector was constructed in $2\pi/12$ azimuthal sections called supersectors, each of which were tested for tile quality with cosmic rays and tile crosstalk with a radioactive source. In this poster, I will discuss the process of constructing the supersectors that make up the disks as well as the multiple tests performed on the finished supersectors to characterize their quality.

Speaker: Joseph Adams (Ohio State University)

200 Contrasting freezeout schemes in large versus small systems

Freezeout in relativistic collisions occurs as a result of competition between interaction of the fireball constituents and fireball expansion. The magnitude of interaction of the fireball constituents is expected to go down as we go from nucleus-nucleus (A-A) to proton-nucleus (p-A) to proton-proton (pp) collisions which should show up in the thermal model fits of the hadron yields. However, on the contrary, it has been found that within the unified freezeout scheme (1CFO), the fits to hadron yields are insensitive to system size. In this talk we extend the 1CFO scheme to multiple freezeout with early freezeout of strangeness (2CFO) and analyse the system size dependence of the freezeout scheme. We find unlike 1CFO that is blind to system size, 2CFO fits clearly distinguish between large and small system sizes.

We discuss the freezeout conditions in pp, p-Pb and Pb-Pb collisions at the LHC energies by analysing the data on hadron yields and transverse momentum spectra. We have studied three different schemes of freezeout, i) 1CFO, ii) strange hadrons freeze out along with non-strange with an additional strangeness undersaturation factor $\gamma_{S}$ which accounts for the non-equilibrium production of strangeness (1CFO+$\gamma_{S}$), and iii) 2CFO. A comparison of the fit to data suggests that different freezeout schemes are preferred for different collision systems. For small systems (pp and p--Pb) and peripheral Pb--Pb, data prefer 1CFO+$\gamma_{S}$ where $\gamma_{S}$ starts from ~0.8 for pp and reaches close to unity for central p-Pb and peripheral Pb-Pb. For Pb-Pb, 2CFO describes data better than 1CFO and 1CFO+$\gamma_{S}$.

Speaker: Bedangadas Mohanty (National Institute of Science Education and Research (IN))

201 Contributions of Elliptic Wigner distribution to multi-particle azimuthal correlations

Multi-particle azimuthal correlations have recently been measured in proton/deuteron-nucleus collisions at RHIC and at the LHC, and call for theoretical explanations. In particular, whether they originate from the initial or final state interaction is a matter of intense debate. We propose a new, initial-state mechanism to generate multiple correlations like $c_2\{4 \}$ from the combined effect of multi-parton scattering and the elliptic gluon Wigner distribution of the nucleus. This can arise even if the individual parton-nucleus scatterings are independent of each other. We present a numerical estimate of this effect by using the Wigner distribution computed from the impact parameter dependent Balistky-Kovchegov equation.

Speaker: Yoshikazu Hagiwara (Kyoto University)

MPD.pdf

202 Corona effect in AA collisions at LHC and RHIC

Following our earlier finding based on RHIC data about the dominant jet production from nucleus corona region, we reconsider this effect in nucleus-nucleus collisions at LHC energy. Our hypothesis was based on the experimental data, which raised the idea of a finite formation time for the produced medium. At RHIC energy and in low density corona region this time reaches about 2~fm/c. In the center of interaction region it's about 0.7 fm/c. All observed high $p_t$ particles are produced in the corona region and have a chance to escape during this 2~fm/c. After that, the formed high density matter absorbs all jets. Following this hypothesis, the nuclear modification factor $R_{AA}$ should be independent on particle momentum and be flat versus $p_t$. At the same time, we can describe at RHIC the finite azimuthal anisotropy of high $p_t$ particles, $v_2$. A separate prediction held that, at LHC energy, the formation time in the corona region should be two times smaller, about 1~fm/c. New data at LHC show that $R_{AA}$ is not flat and is rising with $p_t$. We add to our original hypothesis an assumption that a fast parton traversing the produced medium loses the fixed portion of its energy. A shift of about 7~GeV from the original power law $p^{-6}$ production cross section in $pp$ explains well all the observed $R_{AA}$ dependencies at all centrality. The shift of about 7~GeV is also valid at RHIC energy, where the cross section follows a power law with about $p^{-8}$ and this shift explains a very slow rise of $R_{AA}$ seen for neutral pions with $p_t$ above 15~GeV/c. We also show that the observed at LHC dependence of $v_2$ at high $p_t$ and our previous predictions agree. It is very attractive to call this value of 7 GeV as a parton binding energy.

Speaker: Dr Vladislav Pantuev (INR, RAS)

Corona_RHIC_LHC.pdf

203 Coulomb influence on charged pion production in Au+Au collisions at relativistic energies

Coulomb effects on charged pion transverse momentum spectra produced in Au-Au collisions at RHIC-BES energies are investigated. From these spectra the negative-to-positive pion ratios as a function of transverse momentum are obtained and used to analyze the Coulomb final state interaction between the charged pions and the positive net-charge of the particle source. The „Coulomb kick” (a momentum change due to Coulomb interaction) and initial pion ratio for three different collision energies and various centrality classes were obtained. The Coulomb kick shows a decrease with the increase of beam energy and clear centrality dependence, with largest values for the most central collisions. These results are connected with the kinetic freeze-out dynamics and results are discussed.

Speaker: Prof. Alexandru Jipa (University of Bucharest, Faculty of Physics, Romania)

Alexandru_JIPA_poster_Quark_Matter_2018.pdf

Alexandru_JIPA_poster_Quark_Matter_2018.ppt

204 Cumulants of Net-Proton Multiplicity Distributions in Cu+Cu Collisions at $\sqrt{s_{NN}}$ = 22.4, 62.4 and 200 GeV from STAR

Fluctuations of conserved charges (B, Q, S) are sensitive observables to explore the QCD phase structures in high-energy nuclear collisions. The STAR experiment has reported the energy dependence of the cumulants of net-proton, net-charge and net-kaon distributions in Au+Au collisions at RHIC. Non-monotonic energy dependence has been observed in the net-proton fluctuations in the most central (0-5%) Au+Au collisions for the energies in the RHIC beam energy scan.

In this poster, we will report the collision energy and centrality dependence of net-proton higher moments for Cu+Cu collisions at $\sqrt{s_{NN}}$ = 22.4, 62.4 and 200 GeV in STAR. In a smaller colliding system, the final freeze-out of the hot QCD matter is closer to the phase boundary so more genuine information on the phase structure, including QCD critical point, is retained compare to much larger systems. We will compare the results from Cu+Cu collision to that of Au+Au collisions as a function of both initial system size ( $N_{part}$) and the final size ($N_{mult}$) at these collision energies.

Speaker: Zhenzhen Yang (CCNU/LBNL)

QM18poster_ZhenzhenYang_v7.pdf

205 D$^{*\pm}$ Production in Au+Au Collisions at $\sqrt{s_{NN}}$ = 200 GeV Measured by the STAR Experiment

One of the goals of heavy-ion collisions is to search for the Quark-Gluon Plasma (QGP) and study its properties. Due to their large masses, heavy quarks are mainly produced in the initial hard scatterings during the early stage of heavy-ion collisions and experience the entire space-time evolution of the system. At the STAR experiment, utilizing high-precision secondary vertex reconstruction provided by the Heavy Flavor Tracker (HFT), $D^{0}$ mesons have been comprehensively studied to investigate the charm quark transport in the QGP. Measurement of $D^{*\pm}$ production is complementary to the $D^{0}$ measurement in studying the medium modification to the open charm meson production. It also provides useful information on feed-down contributions to the $D^{0}$ yields.

In this poster, measurement of $D^{*\pm}$ production at mid-rapidity ($|y|<1$) in Au+Au collisions at $\sqrt{s_{_{\rm NN}}}$ = 200 GeV is reported. $D^{*\pm}$ are reconstructed via the hadronic decay channel ($D^{*+}\rightarrow D^{0}\pi^{+}$, $D^{0}\rightarrow K^{-}\pi^{+}$, and its charge conjugate channel) utilizing the STAR HFT detector. The invariant yields of $D^{*\pm}$ and the ratios of $D^{*\pm}/D^{0}$ yields will be shown as a function of transverse momentum in different centralities. The nuclear modification factor ($R_{AA}$) for $D^{*\pm}$ will be presented as well, and physics implications will be discussed.

Speaker: Ms Yuanjing Ji (University of Science and Technology of China)

QM18poster_jiyjv8.pdf

206 D-meson elliptic flow in Pb-Pb collisions at 5.02 TeV with ALICE

The ALICE experiment studies Pb-Pb collisions at the LHC in order to investigate the properties of the hot and dense QCD matter at extreme energy densities. Heavy quarks are sensitive probes to test the medium properties, since they are formed at a shorter time scale with respect to the deconfined state. In particular, the elliptic flow parameter $v_2$ of D mesons is sensitive to the degree of thermalization of charm quarks within the QGP medium and, at high-$p_{\rm T}$, to the path-length dependence of parton energy loss. In addition, the role of recombination mechanisms can be studied by comparing the D mesons with and without strange-quark content.
The elliptic flow of the ${\rm D}^0$, ${\rm D}^+$, ${\rm D}^{*+}$ mesons reconstructed in their hadronic decay channels in the central rapidity region in Pb-Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV will be presented in the centrality classes 10-30% and 30-50%. The first ALICE measurement of the ${\rm D_s}$ $v_2$ in semi-central collisions will be also presented. The D meson $v_2$ in the 30-50% centrality class will be compared to model calculations to constrain the values of the heavy quarks diffusion coefficients at the critical temperature $T_{\rm c}$.

Speaker: Grazia Luparello (Universita e INFN Trieste (IT))

GLuparello_QM2018_V4.pdf

207 D0-meson production as a function of event transverse spherocity in pp collisions at √s = 7 TeV with ALICE at the LHC

Multiplicity and event-shape variables like spherocity can be used to select events according to their topology. They provide a powerful tool to study soft-QCD processes (low Q$^{2}$), such as multiple parton interactions (MPI) and colour reconnection (CR) mechanisms which are expected to produce more isotropic events with respect to events dominated by jet production.

At the Large Hadron Collider (LHC) energies, heavy quarks are produced in hard scattering processes and their production can be described using perturbative quantum chromodynamics (pQCD). The measurements of open heavy-flavour hadrons as a function of spherocity and charged-particle multiplicity could improve the theoretical understanding of the production mechanisms, and the interplay between hard and soft processes.

In this contribution, recent results of the production of prompt D$^{0}$-meson as a function of event transverse spherocity (S$_{\rm O}$) in minimum bias pp collisions at $\sqrt{s}$ = 7 TeV will be presented. The results will be compared to predictions obtained with PYTHIA event generator.

Speaker: Manoj Bhanudas Jadhav (IIT- Indian Institute of Technology (IN))

posterQM2018_ManojJadhav.pdf

208 D0-meson production in p-Pb collisions measured with ALICE at the LHC

The heavy-flavour production in proton--nucleus collisions is sensitive to Cold Nuclear Matter effects (CNM), related to the presence of nuclei in the colliding system such as the modification of the parton distribution functions of nuclei (e.g. shadowing or saturation effects), and parton energy loss in cold nuclear matter. These effects can induce a modification of the heavy-flavour production at low momentum and their measurement is required to understand final-state effects in Pb--Pb collisions related to the presence of the Quark-Gluon Plasma.
The study of heavy-flavour production as a function of multiplicity of charged particles produced in the collision provides information on the dependence of CNM effects on the collision geometry and on the density of final-state particles. In addition, the study of heavy-flavour transverse-momentum modification in high-multiplicity p-Pb collisions could give insight into the possible presence of collective effects.

In this contribution the ALICE measurements of open heavy-flavour production via the reconstruction of $\rm{D^{0}}$-meson hadronic decay are presented, focusing on recent results in p--Pb collisions at $\sqrt{s_{\rm NN}}$= 5.02 TeV collected during LHC Run2. In particular, the production cross sections and the nuclear modification factors down to $p_{\rm T}$ = 0 will be shown. The $\rm{D^{0}}$ nuclear modification factor $Q_{\rm pPb}$, measured as a function of the centrality of the collision and the central-to-peripheral ratio, $Q_{\rm{cp}}$, will be presented as well.
The results will be compared with theoretical model predictions.

Speaker: Cristina Terrevoli (Universita e INFN, Padova (IT))

QM2018D0inpPb_terrevoli.pdf

209 D^{0}-meson Elliptic Flow Measurement in Au+Au Collisions at $\sqrt{s_{NN}}$ = 200 GeV from STAR

A recent result from the STAR experiment shows that in 10-40% central Au+Au collisions at the top RHIC energy the elliptic flow ($v_2$) of the $D^0$-meson follows the Number-of-Constituent-Quark scaling in the same way as it does for light flavor hadrons. This suggests that charm quarks have gained sufficiently large collectivity through their interactions with the Quark-Gluon Plasma (QGP). It is of great interest to see whether this scaling holds in more peripheral collisions, which will shed more lights on how charm quarks interact with the QGP and gain collectivity.

In this poster, we present the centrality and transverse momentum dependences of the $D^0$-meson $v_{2}$ measured in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV by the STAR experiment. The measurement is based on the combined datasets recorded in 2014 and 2016, which yield about a factor of 3 times of the statistics compared to the previously published results. In order to better understand the non-flow contribution in peripheral collisions, the azimuthal anisotropy parameter $v_{2}$ is measured as a function of the pseudo-rapidity gap between the $D^0$-meson and tracks used for reconstructing the event plane. The results will be compared to those of light hadrons in various centrality intervals and physics implications will be discussed.

Speaker: Yue Liang (Kent State Univesrsity & Lawrence Berkeley National Laboratory )

QM18poster_D0v2_Yue_Final.pdf

210 Decoherence and von Neumann entropy production of classical Yang-Mills fields in relativistic heavy ion collisions

In the early stage of relativistic heavy-ion collisions, coherent and anisotropic classical Yang-Mills field emerges.
This field, referred to as glasma, has several instabilities from the anisotropy, so small fluctuations in glasma grow exponentially.
Glasma is also known to have chaoticity, which make the field configuration complex and produces the entropy.
Instability and chaoticity of glasma rapidly drive the pressure isotropization and are expected to cause thermalization.
In this work, we compare the time scale of the entropy production and the pressure isotropization in the classical Yang-Mills field.
We regard the classical field as a coherent state, and evaluate the quantum entropy (von Neuman entropy) obtained by ignoring the off-diagonal density matrix elements, namely decoherence.
We find that the growth of fluctuations cause entropy production and pressure isotropization in the same time scale.
We also discuss how the classical Yang-Mills field loses coherence as a result of time average of the density matrix.

Speaker: Hidefumi Matsuda (kyoto university)

QM.pdf

211 Dielectron production in Pb-Pb collisions at $\sqrt{s_{\textrm{NN}}} = 5.02 \textrm{ TeV}$ with ALICE

Electron-positron pairs are an excellent probe to investigate the properties of the Quark-Gluon Plasma (QGP) created in ultra-relativistic heavy-ion collisions. Because they are produced at all stages of the collision and do not interact strongly with the medium, their spectra reflect the entire space-time evolution of the system. At low invariant mass ($m_{\textrm{ee}} < 1.2 \textrm{ GeV/c}^2$), the dielectron production is sensitive to the properties of vector mesons in the dense medium which is related to the predicted restoration of the chiral symmetry. In the intermediate-mass region ($1.2 < m_{\textrm{ee}} < 2.9 \textrm{ GeV/c}^{2}$), the dielectron continuum gives further insight into the heavy-quark energy loss in the QGP via the measurement of correlated electron-positron pairs from charm- and beauty- hadron decays. Finally, contributions of thermal radiation from the medium, both during the partonic and the hadronic phases, are predicted in a broad mass range and provide information on the temperature of the system.

In this poster, the status of the dielectron measurements in Pb-Pb collisions at $\sqrt{s_{\textrm{NN}}} = 5.02 \textrm{ TeV}$ with ALICE will be presented. In order to interpret the data, the findings will be compared to the expected yield of known hadronic sources, i.e. the hadronic cocktail, as a function of the invariant mass and pair transverse momentum. Finally, the status of the measurement of virtual direct photons and modifications of the dielectron yield in Pb-Pb collisions will be discussed.

Speaker: Carsten Klein (Johann-Wolfgang-Goethe Univ. (DE))

2018-may-09-conference_presentation-poster_0.pdf

212 Dielectron production in pp collisions at sqrt(s)= 7 TeV with ALICE

Dileptons are a prime probe of the deconfined state of strongly-interacting matter, the Quark-Gluon Plasma (QGP), produced in high-energy heavy-ion collisions, as they are not affected by final-state interactions and produced at all stages of the collision. A measurement of the thermal radiation from the QGP in the dielectron intermediate-mass region gives information on the medium temperature. In this region the main component of the dielectron continuum is coming from correlated semi-leptonic decays of charm and beauty hadrons, which may be affected by the energy loss and collectivity of charm and beauty quarks in the QGP. Therefore, it is crucial to understand the primordial heavy-flavour production in vacuum and find a way to separate this contribution from the thermal signal of the QGP. This can be studied in proton-proton collisions.

In this poster, the measurement of correlated e$^+$e$^-$. pairs in pp collisions at $\sqrt{s}$ = 7 TeV with ALICE will be presented. In particular, we will show how the measured distance of closest approach (DCA) of the electrons to the primary vertex of the collision gives the possibility to separate prompt and non-prompt dielectron pairs. The results will be compared with the expectations from known hadronic sources as a function of $m_{\rm ee}$, $p_{\rm T,ee}$ and $DCA_{\rm ee}$. The extraction of the charm and beauty cross sections from a fit of the data with different Monte-Carlo generators will be discussed, as well as the measured fraction of direct photons to inclusive photons.

Speaker: Horst Sebastian Scheid (Johann-Wolfgang-Goethe Univ. (DE))

2018-may-09-conference_presentation-poster_qm18_scheid_finalv2.pdf

213 Dielectron production in pp collisions at sqrt(s)=13 TeV measured in a dedicated low magnetic-field setting with ALICE

Low-mass dielectrons are an important probe for the hot and dense medium which is created in ultra-relativistic heavy-ion collisions. Since leptons do not interact strongly and are produced throughout the whole collision process, they carry information from all collision stages with negligible final-state interaction.

The ALICE detector is well-suited to perform this measurement due to its excellent tracking and particle identification capabilities at low momenta. However, Dalitz decays and photon conversions lead to a high combinatorial background with a signal-to-background ratio of 1:10 to 1:1000 in Pb-Pb collisions, depending on the invariant mass. Therefore, the minimization of the background is a key aspect of this analysis.
The reconstruction efficiency of low-$p_{\rm{T}}$ electrons can be increased by reducing the magnetic field of the ALICE central barrel solenoid from 0.5 T to 0.2 T. This allows a better rejection of the electron background and simultaneously gives the opportunity to increase the accessible phase space of the dielectron measurement. Such a configuration is planned in ALICE for part of the Pb-Pb campaigns in LHC Run 3 and 4 from 2021 on.

This poster will present the status of the dielectron measurement in pp collisions at $\sqrt{s}$ = 13 TeV from pilot runs taken with B=0.2 T in the ALICE central barrel. It will be shown how the analysis was adapted to the reduced-field configuration. The results will be compared to reference data recorded with the nominal field, to illustrate the benefits of the low magnetic field setting. Finally, the invariant-mass and pair-transverse-momentum distributions will be compared to the expected yield from known hadronic sources.

Speaker: Jerome Jung (Johann-Wolfgang-Goethe Univ. (DE))

2018-may-11-conference_presentation-jeromeposterqm18v10.pdf

214 Dijet, dihadron and hadron-jet correlations in resummation improved pQCD approach

Dijet, dihadron and hadron-jet angular correlations as well as dijet transverse momentum asymmetry have been reckoned as important probes of the transverse momentum broadening effects in relativistic nuclear collisions [1,2]. Dijets become de-correlated due to the vacuum soft gluon radiation associated with the Sudakov logarithms and the medium-induced transverse momentum broadening.

We first employ the systematic Sudakov resummation formalism to describe the dihadron and hadron-jet angular correlation data in $pp$ and central $AA$ collisions [1]. For a quark jet at RHIC top energy, a global $\chi^2$ analysis of dihadron and hadron-jet angular correlation data renders the best fit for the medium-induced broadening $\langle p_\perp^2\rangle$ and the so-called jet transport coefficient $\hat q$ in central $AA$ collisions.

Then we develop a systematic theoretical approach to dijet asymmetries in $pp$ collisions based on pQCD expansion and Sudakov resummation formalism [2]. We find that the NLO pQCD calculation is indispensable to describe experimental data, while the resummation formalism is vital near the end points where the pQCD expansion fails to converge due to appearance of large Sudakov logarithms. Utilizing our resummation-improved pQCD approach, we extract jet transport coefficient for quark-gluon plasma in $PbPb$ collisions at 2.76A~TeV.

We can also use this method to study the properites of cold nuclear matter and other related topics [3].

Further experimental and theoretical efforts along the direction of this work shall significantly advance the quantitative understanding of transverse momentum broadening and help us acquire precise knowledge of jet quenching parameter in heavy-ion collisions.

[1] L. Chen, G. Y. Qin, S. Y. Wei, B. W. Xiao and H. Z. Zhang, Phys. Lett. B 773, 672 (2017).
[2] L. Chen, G. Y. Qin, S. Y. Wei, B. W. Xiao and H. Z. Zhang, arXiv:1612.04202 [hep-ph].
[3] L. Chen, G. Y. Qin, S. Y. Wei, B. W. Xiao and H. Z. Zhang, in preparing.

Speaker: Hanzhong Zhang (IOPP, CCNU)

poster-dijet-v1.pdf

215 Dilepton production and resonance properties within a new hadronic transport approach

As electromagnetic probes dileptons open a window to the in-medium properties of vector mesons. In this talk, medium effects to vector mesons are discussed for heavy ion collisions in the low kinetic energy regime of $1 - 3A$ GeV, where the dielectron emission is accessed by the HADES experiment at GSI. A new hadronic transport approach named SMASH (Simulating Many Accelerated Strongly-interacting Hadrons) is employed to study dilepton production, which is based on vacuum resonance properties and consistently includes dilepton emissions below the hadronic threshold. The approach is validated by an excellent agreement with experimental data up to system sizes of carbon-carbon collisions. After establishing this well-understood baseline in elementary and small systems, the significance of medium effects is investigated with a coarse-graining approach based on the same hadronic evolution. Interestingly, the effect of explicit in-medium modifications to the vector meson spectral functions is already important for dilepton invariant mass spectra in ArKCl and larger systems, even though the transport approach with vacuum properties reveals similar features due the coupling to baryonic resonance and the intrinsically included collisional broadening. In addition, the validated dilepton production allows to assess the importance of a microscopic evolution of the hadronic stage by studying the non-equilibrium dilepton radiation in late, dilute stages of high-energy heavy ion collisions, i.e. in hybrid approaches.

Reference:
J. Staudenmaier, J. Weil, V. Steinberg, S. Endres, H. Petersen, "Dilepton production and resonance properties within a new hadronic transport approach in the context of the GSI-HADES experimental data", arXiv:1711.10297 [nucl-th]

Speaker: Jan Staudenmaier (Goethe University Frankfurt, Frankfurt Institute for Advanced Studies)

Poster_QM18.pdf

216 Dirac-mode expansion for quark-number holonomy in lattice QCD

We investigate the quark number density and the quark number holonomy at finite imaginary chemical potential in the lattice QCD using the Dirac-mode expansion. The quark number holonomy is defined by the quark number density and it can be an order parameter which detects the quark-deconfinement [1,2]. We find some analytical formulae of the quark number density. In the large quark mass regime, the quark number density is expressed in terms of the Polyakov loop. On the other hand, in the small quark mass region, the quark number density is expressed by the eigenmodes of the Wilson-Dirac operator on a lattice. It is found that the quark number density strongly depends on the low-lying Dirac modes. However, the quark number holonomy is not sensitive to the low-lying Dirac modes. Based on these results, we discuss the confinement-deconfinement transition [3].

References:
[1] K. Kashiwa, A. Ohnishi, Phys. Lett. B750, 282 (2015), arXiv:1505.06799.
[2] K. Kashiwa, A. Ohnishi, Phys. Rev. D93, 116002 (2016), arXiv:1602.06037.
[3] T. M. Doi, K. Kashiwa, arXiv:1706.00614.

Speaker: Takahiro Doi (RIKEN)

Poster_QuarkMatter_20180515.pdf

217 Direct virtual photons production in minimum-bias and high-multiplicity pp collisions at sqrt(s) = 13 TeV at the LHC with ALICE

Dielectrons produced in ultra-relativistic heavy-ion collisions provide a unique probe of the system evolution as they are unperturbed by final-state interactions. Among the different physics sources of dielectrons, thermal radiation in the form of real and virtual photons is of particular interest as it carries information about the temperature of the hot and dense system created in such collisions.

In heavy-ion collisions, the very low dielectron mass region ($m_{\rm ee} < 0.3 GeV/c^2$) provides information on the temperature of the system via the measurement of thermal radiation in the form of quasi-real virtual photons.Recently, one has observed collective phenomena in high-multiplicity pp collisions that are similar to the ones observed in heavy-ion collisions. If such collisions produce a thermalised system, it should emit thermal radiation as well.

We present the status for the search of such radiation in high-multiplicity pp collisions together with a vacuum reference measurement in minimum bias pp collisions at $\sqrt{s}$ = 13 TeV.

Speaker: Oton Vazquez Doce (Technische Universitaet Muenchen (DE))

QM18POSTER_v6.pdf

218 Direct γ-hadron correlations in Pb-Pb collisions at √sNN=5.02 TeV with ALICE

The medium modification of jets continues to be studied in greater and greater detail, ranging from their absolute yields to substructure measurements. A key problem has always been to accurately determine the jet energy calibration in order to establish the influence of the hot QCD medium on the observed jet properties. A way to circumvent this ambiguity is the measurement of direct $\gamma$-hadron correlations. The direct photon, produced in hard scatterings back-to-back with a parton, serves as a calibration of the away-side jet and thus provides less-biased insight into how the medium affects the away-side jet fragmentation. We ultimately aim to measure the modified fragmentation function f($z_{\mathrm{T}}$) and its dependencies on several quantities like the $\gamma$-trigger $p_{T}$ or associated hadron $p_{T}$ to understand the $z_{T}$ dependence.
\par
This poster will demonstrate our capability to measure inclusive $\gamma$-hadron and $\pi^{0}$-hadron correlation functions. Results will be presented for Pb--Pb data at \ensuremath{\sqrt{s_\mathrm{NN}}}=5.02\,TeV, measured with the EMCal and DCal detectors of the ALICE experiment.

Speaker: Eliane Epple (Yale University)

Poster_Printversion_QM2018_GammaPi0HadronCorr.pdf

219 Directed Flow Due to the Initial Source Tilt and Density Asymmetry in Cu+Au and Au+Au Collisions at STAR

Despite of a generally very successful description of the elliptic and higher harmonic flow in heavy-ion collisions by theoretical models, there is no single model that explains the dependence of the directed flow on pseudorapidity, collision energy, system size, and the particle type. This indicates that an important piece in our picture of ultrarelativistic heavy-ion collisions is still missing. Directed flow is thought to arise from two main mechanisms: the so-called "tilted" source and the dipole-like initial density asymmetry. The asymmetric Cu+Au collisions provide a unique possibility to identify the roles of theses two mechanisms.

We present the results of directed flow measurements for charged and identified particles in Cu+Au and Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 200 GeV as a function of centrality, pseudorapidity, and transverse momentum. We show how the comparison of pseudorapidiy dependence of $v_1$ and $\langle p_x\rangle$ can be used to quantify the contribution of different mechanisms of directed flow formation. We compare the results with Pb+Pb collisions at the LHC energies, and discuss the centrality and energy dependence of the relative contributions to the directed flow from the initial source tilt and from the density asymmetry.

Speaker: Takafumi Niida (Wayne State University)

QM18_poster_niida_v3.pdf

220 Dissipative effects in ultrarelativistic kinetic theory

The equations of relativistic hydrodynamics can be obtained from
the Boltzmann equation via the Chapman-Enskog (CE) procedure and
Grad’s 14 moments approximation. These approaches give different
results for the transport coefficients, which reduce to the same
expressions in the non-relativistic limit.

In this contribution, the propagation of a harmonic longitudinal
wave is considered in the frame of the first- and second-order
relativistic hydrodynamics theories. The ensuing hydrodynamic
equations are solved in the linearized regime (valid for small
wave amplitudes). The analytic solutions corresponding to the
CE and Grad transport coefficients are compared to the numerical
solution of the relativistic Boltzmann equation for massless
particles in the Anderson-Witting (AW) approximation, obtained
using the lattice Boltzmann (LB) method. The comparison clearly
confirms the validity of the CE prediction.

For particular initial conditions, the first-order formulation
gives incorrect predictions for the wave evolution even when
the AW relaxation time is small. This is remedied in the
second-order formulation, the solution of which is confirmed
by numerical simulations.

Speaker: Victor Eugen Ambrus (West University of Timisoara)

qm2018-hydro.pdf

221 Divergence of the gradient and slow-roll expansions in Bjorken and Gubser flow

Relativistic hydrodynamics has played a key role in our understanding of the novel properties of quark-gluon plasma. However, the validity of hydrodynamical models in describing the extreme conditions produced in heavy ion collisions has still not been properly justified theoretically. Even more, the gradient expansion, commonly used to derive hydrodynamics from microscopic theory, has been recently shown to diverge for conformal fluids or relativistic gases undergoing Bjorken flow [1,2], putting under question the definition of hydrodynamics itself. Alternative derivation of the hydrodynamic series have been proposed recently, such as the slow-roll expansion [1], and can be promising candidates to define hydrodynamics.

In this contribution, we present general analytical and semi-analytical solutions of the hydrodynamic attractor of Israel-Stewart theory [2] and kinetic theory for Bjorken and Gubser expanding fluids. We show that the gradient expansion diverges in both cases. For Israel-Stewart theory, we show for the first time that even the slow-roll expansion, a commonly used approach to characterize the attractor, diverges. Finally, we construct the slow-roll expansion for a general flow scenario and find the effective shear viscosity [3] and relaxation time that are able to describe a more general hydrodynamic regime.

[1] M. P. Heller and M. Spalinski, "Hydrodynamics Beyond the Gradient Expansion: Resurgence and Resummation," Phys. Rev. Lett. 115, no. 7, 072501 (2015).
[2] G. S. Denicol and J. Noronha, "Analytical attractor and the divergence of the slow-roll expansion in relativistic hydrodynamics,'' arXiv:1711.01657 [nucl-th].
[3] P. Romatschke, "Relativistic Hydrodynamic Attractors with Broken Symmetries: Non-Conformal and Non-Homogeneous,'' arXiv:1710.03234 [hep-th].

Speaker: Gabriel Denicol (McGill University)

222 Dynamical initialization with core-corona picture in small colliding systems

We study effects of dynamical initialization with a core-corona picture in hydrodynamic description of small colliding systems at RHIC and the LHC energies. We previously proposed an idea of dynamically initializing hydrodynamic fields by utilizing source terms in hydrodynamic equations [1]: Instead of setting initial conditions at a fixed hydrodynamic initial time, we make initially produced partons propagate and deposit energy and momentum into the bulk matter via the source terms to form the quark gluon plasma (QGP) fluids gradually. Under this idea, not only initial fluctuations of geometry but also those of velocity fields are naturally generated. In the present study, we further introduce the core-corona picture to the idea by considering spatial density of the initially produced partons. Here, partons produced in the dilute region fragment into hadrons separately instead of taking part in the initial QGP fluid formation. This picture strongly affect the fluid profile in small colliding systems and must be taken into account.

To demonstrate the above idea, we employ a QGP fluid + jet model [2] in which the QGP medium evolution is described by (3+1)-D hydrodynamic equations with source terms. As an input, we generate partons by using the latest version of PYTHIA 8.230 which involves heavy-ion collisions. As propagating after the production, these partons deposit energy and momentum into the bulk QGP fluid according to the parton density around them in the core-corona picture. From simulations with this newly developed framework, we calculate hadron spectra including contributions from both the surviving partons in the dilute regions with PYTHIA fragmentation and the fluid part in the dense region and show that the core-corona picture plays a crucial role in small colliding systems.

[1] M.Okai, K.Kawaguchi, Y.Tachibana, T.Hirano, Phys. Rev. C 95, no. 5, 054914 (2017).

[2] Y.Tachibana, T.Hirano, Phys. Rev. C 90, no. 2, 021902 (2014).

Speaker: Yuuka Kanakubo (Sophia Univ.)

posterYK_ver5.pdf

223 Dynamical quenching weights in an expanding medium

In this work, we extend the resummation of multiple medium-induced emissions to apply to dynamically expanding media. This is done by recasting the quenching weight as the solution of a rate equation with medium-induced partonic splitting functions that are sensitive to the expansion. We perform the calculations in the framework of Baier-Dokshitzer-Mueller-Peigne-Schiff-Zakharov (BDMPSZ) formalism for multiple soft scatterings with a time-dependent transport coefficient. Furthermore, we discuss the validity of a dynamical scaling law that relates the spectrum in an expanding medium to the equivalent static case with rescaled medium parameters [1] and test the size of energy loss fluctuations in a realistic medium.

References:
[1] Carlos A. Salgado and Urs Achim Wiedemann "A Dynamical Scaling Law for Jet Tomography", Phys. Rev. Lett. 89, 092303.

Speaker: Souvik Priyam Adhya (Department of Atomic Energy (IN))

224 Dynamical Thermalization in the Quark-Meson Model

Understanding the early out-of-equilibrium dynamics of heavy-ion collisions (HIC) remains one
of the biggest theory challenges. So far, there are no first principle calculations for the equilibration
process of the quark gluon plasma and the dynamics close to the phase transition. In particular
describing the behavior close to the conjectured critical point, where critical slowing down leads
to off-equilibrium dynamics, poses difficulties.
Here we study the initial stages of a HIC using a low-energy effective theory of QCD, the
quark-meson model, in order to gain insight into the thermalization process. This model manifests
a central and physically relevant feature of QCD: chiral symmetry breaking in vacuum and its
restoration at finite temperature and density. At the critical endpoint this model is expected to
be in the same universality class as QCD and hence a viable model to explore dynamical critical
phenomena.
We solve the non-perturbative real-time quantum equations of motions for the quark and meson
fields in the two-particle irreducible effective action framework. Similar to a HIC, our system is
prepared in a high-energy initial state and suddenly quenched out of equilibrium, evolving towards
a thermal final state in the chirally broken phase.
In a first step, we investigate the time-evolution of both bulk and spectral properties of this
system, which provides us with insight into the approach of thermalization over time and the
properties of the relevant degrees of freedom dominating the real-time dynamics. For the thermal
final state, this implies information about the mass spectrum and the thermalization temperature.
Finally, the prospects of generalizing the simulations to finite baryon density and the approach to
the critical point are discussed.

Speaker: Linda Shen (Institute for Theoretical Physics, Heidelberg University)

Poster.pdf

225 Dynamics of relativistic polarized vortices

We present first numerical applications of a recently formulated framework of perfect fluid hydrodynamics with spin [1] to model the space-time evolution of polarization in heavy-ion collisions. We consider various initial conditions for the hydrodynamic evolution and different forms of the spin tensor to study consequences of various physical assumptions for the time evolution of the system's polarization [2]. Our findings show a characteristic decrease of the overall polarization in the system with the increasing collision energy, as recently found in the experimental measurements of the Lambda hyperons. We also find that the polarization in our approach increases with time during the hydrodynamic evolution, an effect connected with the overall angular momentum and entropy conservation laws.

[1] W. Florkowski, B. Friman, A.Jaiswal, E. Speranza, arXiv:1705.00587
[2] W. Florkowski, B. Friman, A.Jaiswal, R.Ryblewski, E. Speranza, forthcoming

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

226 Effect of field fluctuations on heavy mesons nuclear modification factor at LHC energies

The aim of the ongoing relativistic heavy-ion collision experiments is to explore the possible hot and dense deconfined state of QCD matter produced in such high energy collisions, the so called Quark-Gluon-Plasma (QGP). High energy partons (gluons, light quarks as well as heavy quarks) are produced in initial partonic sub-processes in the collisions between two heavy nuclei. Heavy quarks are mostly produced at the early stage of the collisions from the initial fusion of the partons which makes them a good probe to characterize the QGP. Immediately after their production, these heavy quarks will travel through the dense QGP medium and will start loosing energy during their path of travel. They lose energy in two different manners,one is by elastic collisions and another is by bremsstrahlung gluon radiations. These energy loss calculations are usually obtained by considering the QGP medium in an average manner and statistical field fluctuations of the QGP medium are ignored. The QGP being a statistical system of mobile color charge particles, one could characterize it by stochastic electromagnetic field fluctuations. The effect of this field fluctuations in the QGP leads to an energy gain of the travelling heavy quarks of all momenta and significant at the lower ones.

We have calculated the nuclear modification factor ($R_{AA}$ ) of heavy mesons by considering the collisional and radiative energy loss of heavy quarks along with the energy gain due to field fluctuations. Our results are in good agreement with the experimentally measured $R_{AA}$ of D and B mesons by ALICE and CMS experiments at $\sqrt{s_{NN}} = 2.76$ TeV and $\sqrt{s_{NN}} = 5.02$ TeV.

Speaker: Ashik Ikbal Sheikh (Department of Atomic Energy (IN))

posterQM_ashik.pdf

227 Effect of initial state on thermal photons in heavy ion collisions

The experimental measurement of the direct photon $v_2$ and the theoretical prediction for the same differ by a large margin both at RHIC and at the LHC energies. This is known as the ``direct photon puzzle". We investigate the effect of initial conditions on the production and elliptic flow of photons from relativistic heavy ion collisions in detail.

It is well known that the inclusion of fluctuations in the hydrodynamic initial condition explains the experimental data on hadronic spectra and elliptic flow better compared to a smooth initial condition and it also increases the production and $v_2$ of photons significantly. In the same spirit, we consider another realistic constraint; initial state nucleon shadowing in the Monte-Carlo Glauber model and investigate the effect of shadowed initial condition on the production and elliptic flow of thermal photons at RHIC and LHC collision conditions [1].

In addition, we calculated the $p_T$ spectra and elliptic flow of thermal photons for two different orientations of fully overlapping uranium nuclei at 193A GeV at RHIC using a hydrodynamic model [2]. We see that the elliptic flow from body-body collisions of uranium nuclei is large and comparable to the photon $v_2$ obtained from mid-central collisions of gold nuclei at 200A GeV. We show that the photon results from fully overlapping U+U collisions are complementary to the results from Au+Au collisions at RHIC.

[1] P.~Dasgupta, R.~Chatterjee, S.~K.~Singh and J.~E.~Alam, arXiv:1704.05715.
[2] P.~Dasgupta, R.~Chatterjee and D.~K.~Srivastava, Phys.\ Rev.\ C {\bf 95}, no. 6, 064907 (2017).

Speaker: Mr Pingal Dasgupta (Variable Energy Cyclotron Centre)

poster2.pdf

228 Effect of Quantum Corrections on a Realistic Nuclear Matter EoS and on Compact Star Observables

The accuracy of astrophysical observations regarding compact stars are
ahead of a big evolution jump thanks to instruments like NICER [1],
which will increase the accuracy of the measurements. The discovery of
gravitational waves originating from merging neutron stars in this year
(GW170817 [2]) is the first step to use gravitational waves as a probe
for extremely dense nuclear matter.

Despite these developments the masquarade problem still persists in
modeling cold superdense nuclear matter based on compact star
observables. Since many different models yield similar neutron star
parameters only high-precision measurements and theoretical reasons can
exclude models.

In this talk we present a realistic, Walecka-type model where the
bosonic fluctuations are included using the Functional Renormalization
Group (FRG) method in the Local Potential Approximation (LPA), based on
a our technique published previously [3,4]. The thermodynamical
quantities, equation of state (EoS), compressibility are calculated in
different approximations: mean field, 1st order and high order. Based
on these EoS, the properties of the corresponding neutron stars are
also calculated using the Tolman--Oppenheimer--Volkov (TOV) equations.

It is also presented, how calculating quantum corrections in different
approximations change the predicted neutron star parameters like mass,
radius and compactness. These results show, that in the light of the
new developments in astrophysical observations quantum corrections are
approaching the threshold where calculating them will be necessary for
the correct comparison between different models.

References
[1] NASA 2017, Nicer, https://www.nasa.gov/nicer
[2] Ligo/Virgo 2017, Phys. Rev. Lett., 119, 161101
[3] Barnaföldi G. G., Jakovac A., Posfay P., 2017, Phys. Rev., D95,025004
[4] Pósfay P. Barnaföldi G.G., A. Jakovác,
arXiv:1710.05410, arXiv:1610.03674

Speaker: Gergely Gabor Barnafoldi (Wigner RCP Hungarian Academy of Sciences (HU))

Posfay_Peter_qm2018_v1.6.pdf

229 Effect of the QCD equation of state and strange hadronic resonances on multiparticle correlations in heavy ion collisions

The QCD equation of state at zero baryon chemical potential is the only element of the standard dynamical framework to describe heavy ion collisions that can be directly determined from first principles. Continuum extrapolated lattice QCD equations of state have been computed using 2+1 quark flavors (up/down and strange) as well as 2+1+1 flavors to investigate the effect of thermalized charm quarks on QCD thermodynamics. Lattice results have also indicated the presence of new strange resonances that not only contribute to the equation of state of QCD matter but also affect hadronic afterburners used to model the later stages of heavy ion collisions. We investigate how these new developments obtained from first principles calculations affect multiparticle correlations in heavy ion collisions. We compare the commonly used equation of state S95n-v1, which was constructed using what are now considered outdated lattice results and hadron states, to the current state-of-the-art lattice QCD equations of state with 2+1 and 2+1+1 flavors coupled to the most up-to-date hadronic resonances and their decays. New hadronic resonances lead to an enhancement in the hadronic spectra at intermediate $p_T$. Using an outdated equation of state can directly affect the extraction of the shear viscosity to entropy density ratio, $\eta/s$, of the quark-gluon plasma and results for different flow observables. The effects of the QCD equation of state on multiparticle correlations of identified particles are determined for both AuAu $\sqrt{s_{NN}}=200$ GeV and PbPb $\sqrt{s_{NN}}=5.02$ TeV collisions. New insights into the $v_2\{2\}$ to $v_3\{2\}$ puzzle in ultracentral collisions are found. Flow observables of heavier particles exhibit more non-linear behavior regardless of the assumptions about the equation of state, which may provide a new way to constrain the temperature dependence of $\eta/s$.
[1] Alba, Sarti, Noronha, Noronha-Hostler, Parotto, Vazquez and Ratti, arXiv:1711.05207

Speaker: Dr Valentina Mantovani Sarti (TU Munich)

Poster_VMS.pdf

230 Effect of Volume Fluctuation and Non-binomial Efficiency on the Cumulants of Net-proton Multiplicity Distributions at the STAR Experiment

Recent STAR results on net-proton cumulant ratio $C_{4}/C_{2}=\kappa\sigma^{2}$ show a non-monotonic behavior as a function of beam energy [1], which has been interpreted as a signature of the QCD critical end point. However, all previous STAR results were obtained with a binomial assumption for the efficiency correction. Unfolding of net-proton distributions is necessary in order to correct for non-binomial detector effects [2]. In addition, there are still no established ways for volume fluctuation corrections. Recently another model dependent method [3] has been suggested to eliminate the participant fluctuations. In this poster, we present the results of the unfolding method that attempts to correct for the non-binomial detector efficiencies and apply the new method for volume fluctuation corrections. The differences with respect to the previous results are discussed.

References
[1] Xiaofeng Luo (for the STAR collaboration), Proceedings, 9th International Workshop on Critical Point and Onset of Deconfinement (CPOD 2014), Vol. CPOD2014 (2015).
[2] A. Bzdak, R. Holzmann, and V. Koch, Phys. Rev. C94, 064907 (2016).
[3] P. Braun-Munzinger, A. Rustamov, and J. Stachel, Nucl. Phys. A960, 114130 (2017).

Speaker: Toshihiro Nonaka (Univ. Tsukuba)

poster_tnonaka_v2.pdf

231 Effective kinetic description of event-by-event pre-equilibrium dynamics in high-energy heavy-ion collisions

We develop a macroscopic description of the space-time evolution of the energy momentum tensor during the pre-equilibrium stage of a high-energy heavy-ion collision. Based on a weak coupling effective kinetic description of the microscopic equilibration process (a la ``bottom-up"), we calculate the non-equilibrium evolution of the local background energy-momentum tensor as well as the non-equilibrium linear response to transverse energy and momentum perturbations for realistic boost-invariant initial conditions for heavy ion collisions. We demonstrate that this framework can be used on an event-by-event basis to propagate the energy momentum tensor from far-from-equilibrium initial state models, e.g. IP-Glasma, to the time $\tau_\text{hydro}$ when the system is well described by relativistic viscous hydrodynamics. We show that with kinetic theory pre-equilibrium, the final hadron multiplicities and radial and elliptic flows become essentially independent of the hydrodynamic initialization time $\tau_\text{hydro}$. The effective kinetic description of the pre-equilibrium evolution can be also used for studying the chemical equilibration of quarks and gluons and the pre-equilibrium photon production.

Speaker: Aleksas Mazeliauskas (Universität Heidelberg)

poster.pdf

232 Effects of composite pions on the chiral condensate within the PNJL model at finite temperature

We investigate the effect of composite pions on the behaviour of the chiral condensate at finite temperature within the Polyakov-loop improved NJL model.
To this end we treat quark-antiquark correlations in the pion channel (bound states and scattering continuum) within a Beth-Uhlenbeck approach that uses medium-dependent phase shifts.
A striking medium effect is the Mott transition which occurs when the binding energy vanishes and the discrete pion bound state merges the continuum. This transition is triggered by the lowering of the continuum edge due to the chiral restoration transition. This in turn also entails a modification of the Polyakov-loop so that the SU(3) center symmetry gets broken at finite temperature and dynamical quarks (and gluons) appear in the system taking over the role of the dominant degrees of freedom from the pions.
At low temperatures our model reproduces the chiral perturbation theory result for the chiral condensate while at high temperatures the PNJL model result is recovered.
The new aspect of the current work is a consistent treatment of the chiral restoration transition region within the Beth-Uhlenbeck approach on the basis of mesonic phase shifts for the treatment of the correlations. Special emphasis is on the discussion of the result for the pseudocritical temperature of the chiral transition which in PNJL models at the mean field level comes out too large, in contradiction with lattice QCD results. The present approach provides a considerable improvement.

Speaker: Alexandra Friesen (Joint Institute for nuclear research)

QM2018_Friesen.pdf

233 Effects of equation of state and spectators on directed flow in Au+Au collisions at √sNN = 3-20 GeV from JAM model

The STAR experiment has published the energy dependence of the directed flow (v1) of identified particles, such as proton, charged kaons and pions [1]. A clear sign change is observed in excitation function of the proton v1 slope, which could be an indication of the softening of the equation of state (EoS) due to 1st order phase transition. The v1 slope for produced particles, such as charged pions and kaons are negative while the v1 slope of protons show positive values at low energies. This anti-correlation between proton and pion v1 slope has been previously studied at 1GeV beam energy [2].

In this talk, we will report the v1 of proton, and charged pions, kaons in Au+Au collisions at √sNN = 3-20 GeV from transport model (JAM). For the first time, we explicitly and quantitatively discuss the effects of spectator shadowing on the v1 at RHIC BES energy region. We observe that the negative v1 slope for both pions and kaons BES energies are caused by their scattering with the spectator nucleons (shadowing effects), which can explain the different behavior of the directed flow for proton and other produced particles. We also find that a softening of EoS will lead to a negative proton v1 slope within JAM hadronic transport model.

[1] STAR Collaboration, arXiv: 1708.07132, PRL in Press.
[2]S. A. Bass, R. Mattiello, H. Stocker, W. Greiner, Physics Letters B
302, 381(1993).

Speaker: Chao Zhang (Central China Normal University)

ChaoZhangQM2018poster_v5(1).pdf

234 Effects of multiple jets in gamma-jets and dijet correlations in heavy ion collisions

The study of modification of boson-tagged jet and dijet in high energy heavy ion collision can provide physical insight of jet-medium interactions. In this study, we use the Linear Boltzmann Transport(LBT) model to simulate the propagation of the shower partons generated from pythia or sherpa Monte Carlo simulations in the hot quark gluon plasma. We first calculate the $p_{T}$ distribution of the 2nd jet in gamma-jet events according to gamma-jet asymmetry. In the gamma-jet correlation, we find that the inclusion of the 2nd jet will lead to the suppression of the angular correlation at large angle in AA collision. For dijet correlation, we investigate the dijet azimuthal correlation in events with 2, 3, 4 energetic jets for different regions of the leading jet $p_{T}$ in both pp and AA collision. We also show the important contribution of the 3rd jet in dijet transverse momentum balance distribution. We further find that the energy distribution at the edge of the jet cone is modified by the interference among multiple jets inside quark gluon plasma.

Speaker: Tan Luo (Central China Normal University)

235 Effects of resonance widths on particle distributions and anisotropies in heavy-ion collisions

We extend the S-matrix framework to the Delta-type resonances (spin 3/2, isospin 3/2) in elastic pion-nucleon scatterings up to 1.8 GeV mass. We evaluate not only Deltas, but also rho, f_0, K* and K_0 meson properties using the S-matrix framework, and implement them in the hydrodynamical description of Pb+Pb collisions at LHC.

We show that the proper treatment of resonances modifies the spectrum of daughter particles, and thus the final observable distributions. In particular the yield of pions at low p_T increases, which reduces the average transverse momentum, and thus improves the description of the pion spectrum measured in the heavy-ion experiments.

Speaker: Krzysztof Redlich (University of Wroclaw)

236 Electric conductivity of a hadron gas

The electric conductivity of a hadron gas is calculated within the hadronic transport
approach SMASH (Simulating Many Accelerated Strongly-interacting Hadrons). Microscopic
non-equilibrium models are well suited to calculate transport coefficitents that
synthesize the information on the many-particle dynamics. The temperature dependence of
the electric conductivity is extracted using the Green-Kubo formalism for
$T\sim 100-200~\mathrm{MeV}$. The results for the electric conductivity show good agreement
compared to analytic results from literature [Phys.Rev.D 93, 096012 (2016)] for systems
with small number of particle species and simple interactions. Furthermore, the influence of a
finite lifetime of resonances on the electric conductivity is investigated. After validating
the approuch results for the electric conductivity of a more realistic hadron gas including more
particle species are presented.

Speaker: Jan Hammelmann

QMposter18_Final_hammelmann.pdf

237 Electron identification and trigger performance of the ALICE Transition Radiation Detector in p–Pb collisions

The Transition Radiation Detector (TRD) of the ALICE detector at the LHC provides electron identification and an online trigger on high-$p_{\rm T}$ tracks of electron candidates, to significantly enrich samples of electrons originating from open heavy-flavour and heavy quarkonia decays.
The TRD consists of 522 chambers arranged in 6 layers. Each chamber comprises a radiator and a MWPC with pad read-out. When electrons with $p$ > 1 GeV/$c$ travel through the radiator, crossing many boundaries between media with different dielectric constants, TR photons with energies in the X-ray range may be created. These photons are detected using the MWPC filled with Xe/CO$_{2}$, where they deposit their energy on top of the ionisation signals from the particle track. The ALICE TRD is uniquely designed to record the time evolution of the signal. This functionality allows electrons and pions to be better discriminated compared to a 1d-likelihood on the total integrated charge measured in a chamber, because of the preferential TR absorption at the entrance of the MWPC (corresponding to large times).
In addition, chamber-wise track segments from fast on-detector reconstruction are read out with position, angle and PID information. In the Global Tracking Unit these track segments are matched and used for the reconstruction of transverse momenta and electron identification of individual tracks. These tracks form the basis for versatile and flexible trigger conditions, such as electrons with high $p_{\rm T}$.
We present the electron identification and trigger performance in p–Pb collisions recorded during the LHC Run 2. The first is addressed with various methods, e.g. 1d- and multidimensional likelihood as well as neural networks. The second is quantified in terms of efficiency, purity and enhancement factors of physics observables.

Speaker: Dr Yvonne Chiara Pachmayer (Ruprecht Karls Universitaet Heidelberg (DE))

poster_qm2018_pachmayer.pdf

238 Elliptic flows of charmonium states in heavy ion collisions

Starting from the investigation on the measurements of elliptic flows for charmed hadrons, we study charmonium state elliptic flows formed from coalescence of charm and anti-charm quark elliptic flows in the quark-gluon plasma. We find that the elliptic flow of the J/ψ meson is larger than that of the ψ(2S) meson in the intermediate transverse momentum region, and show that the elliptic flows of charmonium states depend significantly on both their constituent quark elliptic flows and their wave function distributions in momentum space. Based on our evaluations of charmonium state elliptic flows we also discuss the quark number scaling of elliptic flows for charmonium states, and conclude that studying the elliptic flow of each charmonium state allows us to have a better understanding of the production mechanism of charmonium states in relativistic heavy ion collisions.

Speaker: Sungtae Cho (Kangwon National University)

239 Emissivity of baryon-rich matter – dilepton spectroscopy in CBM

An experimental observation of a first order phase transition, the critical end point and the restoration of spontaneously broken chiral symmetry is the milestone in our understanding of the phase structure of strongly interacting matter. Herewith, electromagnetic probes (dileptons) play a unique role. An unprecedented interaction rate of the Compressed Baryonic Matter (CBM) experiment at FAIR is the key for high-precision measurements of multi-differential observables of rare dilepton signal. This contribution discusses systematic investigations of lepton pairs over the whole range of invariant masses emitted from a hot and dense fireball. An important part of the research program will be the high-precision measurement of the dilepton invariant mass distribution not only below 1 GeV/c$^2$, but in particular between 1 and 2.5 GeV/c$^2$ for different beam energies. In order to extract the continuum dilepton signals, the physical and combinatorial background of lepton pairs has to be precisely determined. Simulation results in both the di-electron and in the di-muon channel will be presented.

Speaker: Mr Etienne Bechtel (Goethe University)

QM2018_EB.pdf

240 Energy and centrality dependence of resonance production in heavy-ion collisions with ALICE at the LHC

In this talk we present a comprehensive set of measurements on hadronic resonance production with ALICE, including new results from the LHC Run II . Transverse momentum spectra, integrated yields, mean transverse momenta, particle ratios and nuclear modification factors will be presented for $\rho(770)^{0}$, $K^*(892)^{0}$, $\phi(1020)$, $\Sigma(1385)^{\pm}$, $\Lambda(1520)$ and $\Xi(1530)^{0}$ as a function of multiplicity/centrality in Pb-Pb collisions. New data for $K^*(892)^{0}$ and $\phi(1020)$ in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV are used to study the energy dependence of the hadronic interactions and of jet quenching. The first results from the recent Xe-Xe run will also be shown. The obtained results give us the possibility to constrain the lifetime of the hadronic phase. They are discussed and compared to predictions of models such as grand-canonical thermal models, PYTHIA, PHSD and EPOS3 event generators and with lower energy measurements.

Speaker: Anders Garritt Knospe (University of Houston (US))

Knospe180515v7.pdf

241 Energy and multiplicity dependence of K*(892)0 production in pp Collisions with ALICE at the LHC

The lifetimes of short-lived hadronic resonances are comparable to the lifetime of the hadronic phase in high-energy heavy-ion collisions. These resonances are sensitive to re-scattering and regeneration processes in the time interval between the chemical and kinetic freeze-out, which might affect the resonance yields. Thus, such resonances can be very useful to probe the medium. Measurements in pp collisions are used as a reference for nuclear collisions and provide, in addition, information for the tuning of Quantum Chromodynamics (QCD) inspired event generators. In this contribution, we plan to present recent measurements of the production of the $K^{*}(892)^{0}$ resonance in pp collisions at the LHC with the ALICE detector. Results on transverse momentum spectra, yields and their ratios to long-lived particles will be presented and discussed as a function of energy and event multiplicity, as well as in comparison to model predictions.

Speaker: Arvind Khuntia (Indian Institute of Technology Indore (IN))

Arvind_QM2018_v4.pdf

242 Energy Dependence of the Fluctuations of Net-Lambda Distributions at STAR

The measurement of conserved charge distributions have generated considerable interest in understanding the cumulants of conserved quantum numbers in the QCD phase diagram, in particular the behavior near a possible critical end point and hadronization near chemical freeze-out line. Net-protons have been used as a proxy for net-baryons. In this poster, we show a first measurement of the efficiency-corrected cumulant ratios ($C_{2}/C_{1}$, $C_{3}/C_{2}$) of net-$\Lambda$, which are subject to strangeness and baryon number conservation, for five beam energies ($\sqrt{s_{NN}} = $ 19.6, 27, 39, 62.4 and 200 GeV Au$+$Au collisions) as a function of centrality and rapidity. We compare our results to the previous STAR results [1, 2], the Poisson and negative binomial expectations, as well as the UrQMD model, the hadron resonance model, and lattice QCD predictions. We deduce chemical freeze-out parameters ($\mu_{B}$, T) and discuss the deviations of the cumulant ratios from Poisson as possible signals for critical fluctuations.

References
[1] L. Adamczyk et al. (STAR Collaboration), "Energy Dependence of Moments of Net-proton Multiplicity Distributions at RHIC", Phys. Rev. Lett.112, 032302 (2014), arXiv:1309.5681.
[2] L. Adamczyk et al. (STAR Collaboration), "Collision Energy Dependence of Moments of Net-Kaon Multiplicity Distributions at RHIC", arxiv:1709.00773.

Speaker: Mr Nalinda Kulathunga (University of Houston)

QM_nLambda_STAR.pdf

243 Energy dependence of the transverse momentum distribution of charged particles in Pb--Pb measured with ALICE

We present the analysis of transverse momentum ($\textit{p}_\text{T}$) spectra of primary charged particles in Pb-Pb collisions at $\sqrt{s_\text{NN}}=5.02\,\text{TeV}$ and $\sqrt{s_\text{NN}}=2.76\,\text{TeV}$.
For both data sets, we employ improved analysis methods that result in a significant reduction of systematic uncertainties with respect to previous analyses.
We discuss the evolution of the $\textit{p}_\text{T}$ spectrum with collision energy and the nuclear modification factors ($\text{R}_\text{PbPb}$), which are compared with theoretical model calculations.

Speaker: Michael Karim Habib (GSI - Helmholtzzentrum fur Schwerionenforschung GmbH (DE))

poster_mh.pdf

244 Energy dependence of transverse momentum spectra of primary charged particles in proton proton collisions measured by ALICE at the LHC

Particle production at high energies is often described as a result of the interplay of perturbative (hard) and non-perturbative (soft) QCD processes. Therefore, the measurements of transverse momentum spectra in pp collisions are important to provide a baseline for perturbative QCD and constraints for a better tuning of models and event generators. In addition, they constitute a valuable reference to study nuclear effects in nucleus-nucleus and proton-nucleus collisions, in particular allowing one to measure the nuclear modification factors.

The ALICE experiment has collected data of proton-proton collisions at 2.76 TeV, 5.02 TeV, 7 TeV and the top LHC energy of 13 TeV. The 5.02 TeV and 2.76 TeV datasets, in particular, are crucial for the comparison with the measurements in Pb-Pb (5.02TeV and 2.76TeV) and p-Pb (5.02TeV) collisions taken at the same energy. We present the measurements of charged particle transverse momentum spectra in pp collisions at all these energies and the energy evolution as well as comparisons to the expectations from Monte Carlo event generators commonly used at the LHC.

Speaker: Edgar Perez Lezama (Johann-Wolfgang-Goethe Univ. (DE))

posterQM18_v5.pdf

245 Enhancement of $\psi(2S)$ in p-Pb collision at LHC as an indication of QGP formation

Asymmetric p+A collisions serve as a baseline for the understanding of the nucleus-nucleus collisions. Traditionally, they have been employed to observe the differences between the elementary and heavy-ion collision experiments. The heavy flavor production in p+A collision is well explained by cold nuclear matter effects in earlier experiments such as SPS and RHIC. The recent observation of heavy quarkonium production in p+Pb collision at CERN LHC indicates the possible existence of Quark-Gluon Plasma (QGP) in such small system. In this work, we performed pNRQCD calculation to calculate $\psi(2S)$ enhancement and also incorporated other hot nuclear matter effects to explain the yields of different charmonium states in p+Pb collisions at LHC energy,$\sqrt{s_{NN}}\; = \;5.02\; TeV$. We proposed here that the relative enhancement of $\psi(2S)$ vis a vis $J/\psi$, especially at high transverse momentum ($p_{T}$), is a possible clean probe for indicating QGP formation in such a small systems at LHC energies. The $\psi(2S)$ suppression effects observed at ALICE, is also qualitatively explained in the present work.

Speaker: Mr Captain R. Singh (Birla Institute of Technology and Science, Pilani)

qm2018.pdf

246 Equilibration in finite gluon systems

The equilibration of a finite Bose system is modelled using a gradient expansion of the collision integral in the bosonic Boltzmann equation that leads to a nonlinear transport equation. Employing a method that had been proposed earlier for the analytical solution of the equilibration problem in a finite fermion system [1], the basic equation for bosons and in particular, gluons, is solved in closed form for constant transport coefficients through a nonlinear transformation.

With initial conditions that are appropriate for the gluon system in a relativistic heavy-ion collision such as Au+Au or Pb+Pb at energies reached at RHIC or LHC, the exact solution is derived. It agrees well with the numerical solution of the nonlinear equation. The analytical expression for the local equilibration time in the thermal tail is compared to the corresponding case for fermions. The method is also applicable to the (nonrelativistic) equilibration of a cold quantum gas.

Due to the nonlinearity of the basic equation, the sharp edges of the initial gluon distribution at Q_s ≈ 1 GeV are continously smeared out and local equilibrium of the gluon distribution with a thermal tail in the ultraviolett region is rapidly attained [2]. Although gluon condensate formation at p=0 is in principle possible, due to inelastic processes and the nonconservation of particle number in relativistic collisions this appears unlikely to occur in heavy-ion collisions.

The thermal equilibration time for gluons turns out to be nine times shorter than the equilibration time for fermions (quarks) as a consequence of the statistical properties of bosons versus fermions [2]. This result can be viewed as one of the main reasons for the very short local equilibration time in relativistic heavy-ion collisions that are dominated by gluons in their initial stage.

[1] G. Wolschin, Phys. Rev. Lett. 48, 1004 (1982).
[2] G. Wolschin, submitted to Physica A (2017); arXiv:1712.02659.

Speaker: Georg Wolschin (Heidelberg University)

Poster.pdf

247 Estimation of background for photon-hadron correlations in proton-lead collisions at sqrt(sNN) = 5.02 TeV with ALICE

This poster presents a study of an estimation of the background for the measurement of photon-hadron correlations in 5.02 TeV proton-lead collisions. Photon-hadron correlations measure the fragmentation function, which may be modified by energy loss in the QGP. The energy of the photon is not affected by the QGP, so it gives information about the energy of the parton prior to interaction with the QGP. This parton fragments into a jet from which the hadron arises. The main background for this measurement are photons from meson decays. This is estimated via a parameterization of the measurement of the pi0 and eta cross sections and theoretical calculations of the direct photon cross-section using JETPHOX and PeTeR. In order to ensure purity of the photon trigger, we investigate template fits to a novel shower shape variable, which is being developed for the ALICE electromagnetic calorimeter.

Speaker: Barbara Jacak (Lawrence Berkeley National Lab. (US))

rgamma-qm18-poster.pdf

248 Event shape engineering for the D-meson elliptic flow in Pb-Pb collisions at sqrt{s_NN}=5.02 TeV with ALICE at the LHC

Heavy-flavor mesons are effective tools to study the properties of the Quark-Gluon Plasma (QGP) created in ultra-relativistic heavy-ion collisions. Charm and beauty quarks are produced in hard scattering processes on timescales shorter than the QGP formation time due to their large masses and, thus, they experience the entire evolution of the medium interacting with its constituents via in-medium gluon radiation and collisional processes. The measurement of D-meson azimuthal anisotropy, quantified in terms of the elliptic flow $v_2$, allows one to study whether low-momentum charm quarks, interacting with the medium constituents, participate in the collective expansion of the system. At high transverse momentum, the path length dependence of parton energy loss mechanisms can be tested. The dynamics of heavy quarks in the QGP can be further investigated through the Event Shape Engineering (ESE) analysis. Measuring the D-meson $v_2$ in classes of events defined on the basis of the average flow in a given centrality class allows to evaluate the correlation between the elliptic flow of soft hadrons and D mesons. Furthermore, it provides information about the effect of initial state fluctuations on the energy loss experienced by the heavy quark propagating in the QGP.

The measurement of the D-meson $v_2$ in Pb-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV with ALICE performing an ESE analysis based on the selection of events according to the magnitude of the so-called reduced flow vector will be presented. The D mesons are reconstructed via their hadronic decay channels at mid-rapidity in the centrality classes 10-30% and 30-50%. The ratios of the D-meson yields measured in events with large and small average elliptic flow will be shown as well.

Speaker: Andrea Festanti (CERN)

posterQM18_festanti.pdf

249 Event-by-Event fluctuations and consequences on experimental observable at CBM-FAIR and MPD-NICA energies

The evolution of strongly interacting matter created at the FAIR-NICA energies characterized by high net baryon densities and moderate temperatures is expected to occur near the boundary of the first order phase transition and probable in vicinity of the critical QCD point. A large event-by-event fluctuations of hadronic observables are expected to be the signatures of this critical point. In this work we analyze event-by-event fluctuations of several observables like multiplicity, particle ratio, pT, eliptic flow, other flow harmonics, strangeness fluctuations, using different simulation codes . The initial state asymmetry and its effects is discussed based on Glauber model. The region of high density and small temperature of the nuclear matter at FAIR-NICA energies can be considered also in terms of dense local multinucleon fluctuations that is a motivation to consider the possibility of the cumulative processes.

Speaker: Dr Valerica Baban (Constanta Maritime University, Romania)

qm2018.pdf

250 Evolution of higher moments of multiplicity distribution

With the help of a master equation we study the evolution of the
multiplicity distribution. Particularly we focus on the third and fourth
factorial moments from which all other kinds of moments can be
calculated. Among them we also determine the skewness and the kurtosis.
We first study how the third and the fourth moments thermalise when the
kinetic temperature is fixed. Then we study the evolution of the moments
in a situation with decreasing temperature. It is shown that the
relaxation time is the same for all moments but moments of higher orders
get initially further from the equilibrium value if temperature is
changed. We thus issue a warning flag on extraction of temperature from
the higher moments if they come from a rapidly cooling fireball.

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

QMposter18_final.pdf

251 Extending the Bjorken Formula to Describe Initial Energy Production at Lower Energies

The Bjorken formula [1] is very useful for estimating the initial energy density in relativistic heavy ion collisions, once an initial time $\tau_0$ is specified. However, it is well known that the formula is only valid at very high energies [2], where $\tau_0$ is much bigger than the time it takes for the two nuclei to cross each other. Therefore, the Bjorken formula cannot be trusted at lower energies, for example, below $\sqrt{s_{NN}} \sim 50$ GeV for central Au+Au collisions.

Here we extend the Bjorken formula by including the finite crossing time of the two nuclei, which leads to a finite duration time for the initial energy production. We have derived analytical solutions for the energy density as a function of time for several representative duration-time profiles. We also use a multi-phase transport (AMPT) model [3], which treats more realistically the baryon stopping and has been modified to include the finite duration time (as well as the finite longitudinal width) of the initial energy production, and the AMPT results confirm the key features of our analytical solutions. At low energies in comparison with the Bjorken formula, we find [4] that the maximum energy density achieved is much lower while the width of the time evolution of the energy density is much bigger. In addition, it is good to find that the energy density is much less sensitive than the Bjorken formula to the value of the poorly-known formation time $\tau_0$. Furthermore, the extended analytical solutions reduce to the Bjorken formula at high energies. This extension thus provides a general model for the initial energy production of relativistic heavy ion collisions, especially at lower energies such as the RHIC Beam Energy Scan energies.

[1] J.D. Bjorken, Phys. Rev. D 27, 140 (1983).
[2] K. Adcox et al. [PHENIX Collaboration], Nucl. Phys. A 757, 184 (2005).
[3] Z.W. Lin, C.M. Ko, B.A. Li, B. Zhang, and S. Pal, Phys. Rev. C 72, 064901 (2005).
[4] Z.W. Lin, arXiv:1704.08418.

Speaker: Dr Zi-Wei Lin (East Carolina University, Central China Normal University)

poster-BjorkenExtension-ZWLin.pdf

252 Extension of the Identity Method to Measurements of Differential Correlation functions

Studies of integral and differential correlation functions of elementary particles produced in high-energy nucleus-nucleus collisions provide invaluable information on the particle production dynamics, the collision system evolution, and might also enable the determination of fundamental properties of the quark matter produced in these collisions. Extensive measurements of general balance functions, in particular, should provide detailed probes of the formation, evolution, and hadronization of the quark matter produced in relativistic heavy-ion collisions. The difficulty arises, however, that such measurements are particularly statistics hungry and severe particle losses may be incurred experimentally to achieve high species purity and contamination free measurements of correlation functions. However, the identity method, invented by Gazdzicki, provides a technique to essentially recover the full statistics and extend the kinematic range of measurements while providing reliable disambiguation of particle species. The technique was first proposed for measurements of first and second moments of particle multiplicities (integral correlation functions) with two particle species but successively extended to handle an arbitrary number of species, higher moments, and measurements of moments in the presence of transverse momentum dependent efficiency losses. I present yet another extension of the method towards measurements of differential correlation functions, more specifically for differential measurements of the normalized two-particle cumulants, $R_2$, but the method can be extended to other types of two-particle correlators or towards multiple-particle correlation functions. The method is developed for an arbitrary number of particle species and in the presence of particle losses, as well as multiple sources of particle identification ($dE/dx$, TOF, etc).

Speaker: Prof. Claude Andre Pruneau (Wayne State University (US))

PosterIMQM18.pdf

253 Extraction of Bottom Production via the Semi-leptonic Decay Channel in Au+Au Collisions at √sNN = 200 GeV by the STAR Experiment

Quantum Chromodynamics (QCD) predicts that heavy quarks lose less energy than light quarks in the Quark-Gluon Plasma (QGP) created in relativistic heavy-ion collisions. However, recent measurements of the nuclear modification factor ($R_{AA}$) and elliptic flow ($v_2$) for open charm mesons at RHIC show results comparable in magnitude to those of light hadrons, suggesting that charm quarks also interact strongly with the QGP medium. This could mean that the charm quark may not be heavy enough to clearly exhibit the mass dependence of parton energy loss in these measurements at RHIC. Thus it is of particular interest to study the bottom quark energy loss in the medium since bottom quarks are about three times heavier than charm quarks.

In this poster, we will present an analysis based on a data-driven method for determining the yields of electrons from charm and bottom hadron decays, respectively, in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV. The former is estimated from the measured charm hadron yields, and is subtracted from the inclusive heavy-flavor electrons to obtain the latter. The electron $R_{AA}$ and $v_2$ from charm and bottom hadron decays will be presented separately. Model comparison will be discussed as well.

Speaker: Yifei Zhang (University of Science and Technology of China)

254 Factorization of two-particle probability distributions in Pb--Pb collisions at $\sqrt{s_{NN}} = 5.02$ TeV with ALICE

The flow coefficients $v_n$ are commonly extracted from multi-particle distributions where the properties of one or several particles are averaged over a large range in pseudorapidity $\eta$ or transverse momentum $p_{\text{T}}$.
Such approaches assume that the observed multi-particle distributions can be factorized into a product of single-particle distributions.
However, it is known that this condition is violated even in ideal hydrodynamics due to initial state fluctuations or the presence of non-flow.
Detailed studies of a possible violation of this factorization assumption can therefore be used to constrain the size of such fluctuations as well as to identify possible non-flow contributions.
A factorization breakdown can be measured directly in multi-particle probability distributions.
This poster presents an explicit approach to the $\eta$-dependent factorization of two-particle probability distributions within $-3.4 \leq \eta \leq 5$ in the latest $\sqrt{s_{NN}} = 5.02$ TeV Pb--Pb data measured with ALICE.
A factorizing phase-space region is identified by varying the minimal $\Delta\eta$ separation between particles; the factorization breakdown for small separations is attributed to non-flow and detector effects.
The analysis yields the well known $v_n$ coefficients as the result of the factorization process.
These flow coefficients are compared to similar results measured with the Q-cumulant method.
All findings are also compared to model calculations and previous studies at $\sqrt{s_{NN}} = 2.76$ TeV.

Speaker: Christian Bourjau (University of Copenhagen (DK))

180501_QM_Poster.pdf

255 Far-from-equilibrium dynamics near a critical point

We employ the AdS/CFT correspondence and numerical relativity techniques to investigate the far-from-equilibrium dynamics of a strongly coupled non-Abelian plasma with a critical point [1] in the temperature and chemical potential phase diagram. In the case of an out-of-equilibrium homogeneous medium [2], isotropization happens before the system thermalizes and the behavior of the pressure anisotropy changes qualitatively as the chemical potential is increased towards the critical point. These results are then generalized [3] to consider the case of an expanding plasma undergoing Bjorken flow in the vicinity of the critical point, which allows us to determine for the first time how the presence of a critical point affects the emergence of hydrodynamic behavior (hydrodynamization) in a strongly coupled plasma similar to the Quark-Gluon Plasma formed in the RHIC beam energy scan. The interplay between critical phenomena and non-equilibrium hydrodynamic attractor solutions in Bjorken flow [3] will be also discussed.

[1] S.I.Finazzo, R.Rougemont, M.Zaniboni, R.Critelli and J. Noronha, "Critical behavior of non-hydrodynamic quasinormal modes in a strongly coupled plasma," JHEP 1701, 137 (2017).

[2] R.Critelli, R. Rougemont and J. Noronha,"Homogeneous isotropization and equilibration of a strongly coupled plasma with a critical point," JHEP 1712, 029 (2017).

[3] R. Critelli, R. Rougemont and J. Noronha, to appear.

Speaker: Renato Critelli (University of Sao Paulo - Institute of Physics)

poster_QM2018.pdf

256 Fast hydrodynamization with bulk viscosity

Ever since the discovery of the quark-gluon plasma the understanding of its fas thermalization has been a topic of intense research. We use the gauge/gravity duality to model the out-of-equilibrium first stage of a heavy ion collision through the collision of gravitational shockwaves in numerical relativity. This investigation of collisions of sheets of energy density in a non-conformal theory with a gravity dual is the first non-conformal holographic simulation of a heavy ion collision. We demonstrate new non-conformal physics that arises (as compared to the much simpler conformal case) such as a new plasma relaxation channel, the equilibration of the conformal symmetry breaking scalar condensate and the presence of a sizeable bulk viscosity. These ingredients are crucial to make contact of the fast hydrodynamization process of hot plasmas with real-world QCD deconfinement matter.

Speakers: Jorge Casalderrey Solana (University of Oxford), David Mateos (ICREA & U. Barcelona)

257 Femtoscopic Bose-Einstein correlations in proton-proton collisions at 13 TeV with the CMS experiment

Two-particle Bose-Einstein femtoscopic correlations are measured with the data from the LHC Run II collected by CMS in proton-proton collisions at 13 TeV. The analysis is performed over a wide range in event multiplicity, especially reaching the multiplicity regime in which long-range collective correlations were observed. This extension to high multiplicity events represents an important investigation to probe the behavior of the femtoscopic radius and shed light on theoretical models. Three different experimental techniques are applied and discussed in the measurement of these quantum-statistical correlations. Each one of them adopts a different analysis approach, with variable degrees of dependence on Monte Carlo simulated events, which is employed for estimating and correcting the non-Bose-Einstein contributions (resonances and mini-jets). All of the three methods employed provide values for the resulting one-dimensional fit parameters (lengths of homogeneity and correlation intensity) that are consistent within the experimental uncertainties of the analysis. The results are presented as a function of charged particle multiplicity and of the mean transverse pair momentum, in order to study the dynamical behavior of the emitting source.

Speaker: Cesar Bernardes (UNESP - Universidade Estadual Paulista (BR))

Poster_HBT_QM2018_v8.pdf

258 Femtoscopic Measurements for Shape-engineered Events in Au+Au Collisions at STAR

Femptoscopic measurements allow access to the spatio-temporal characteristics of the systems produced in relativistic heavy-ion collisions. This poster presents new measurements of the two-pion HBT radii $\mathrm{R_{out}}$, $\mathrm{R_{side}}$ and $\mathrm{R_{long}}$ have been made for shape-engineered events by the STAR experiment. Shape selection was accomplished via cuts on the distributions of the second-order flow vector $Q_2$ \cite{timmins}\cite{lacey}. Selected events, characterized with larger magnitudes of $Q_{2}$, indicate a systematic decrease for $R_{long}$ and $R_{out}$ with little, if any, change for $R_{side}$. Results obtained as a function of collision centrality and average pair transverse momentum ($k_T$) will be presented for the full range of the Au+Au beam energy scan ($\sqrt{s_{NN}} = 7.7 - 200$ GeV). The implications of these results for expansion dynamics of the collision systems will be discussed.

References
[1] J. Schukraft, A. Timmins, and S. A. Voloshin, Phys. Lett. B719, 394 (2013).
[2] Roy. A Lacey, et. al., J.Phys. G 43 (2016) no.10, 10LT01, arXiv:1311.1728.

Speaker: Benjamin Schweid (Stony Brook University)

259 Femtoscopy with identified charged pions in $p$+Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV with the ATLAS detector

Hanbury Brown and Twiss (HBT) radii are measured as a function of centrality, transverse momentum, rapidity, and azimuthal angle with respect to the second-order event plane in central $p$+Pb collisions at $\sqrt{s_{NN}} = 5.02$ TeV with the ATLAS detector at the LHC. A total integrated luminosity of 28 nb$^{-1}$ is sampled. The radii are presented as a function of the local density dN/dy$^\star$ and the rapidity-dependence is shown to depend directly on the density. The radii and their relative azimuthal modulation are presented as a function of the magnitude of the flow vector $|q_2|$ measured in the ATLAS calorimeters in the lead-going direction, with pseudorapidity $\eta<-2.5$. Modulations of the transverse HBT radii are observed with the same orientation as in ion--ion collisions, in which they are attributed to hydrodynamic evolution from an elliptic initial geometry. This modulation is consistent with a hydrodynamic evolution of a short-lived medium.

Speaker: Brian Cole (Columbia University (US))

ATL-COM-PHYS-2018-478.pdf

260 First results on charged K∗(892) resonance production in pp collisions at √s = 13 with ALICE at the LHC

The study of strange hadronic resonances in pp collisions contributes to the study of strangeness production in small systems. Measurements in pp collisions constitute a reference for the study in larger colliding systems and provide constraints for tuning QCD-inspired event generators. Since the lifetimes of short-lived resonances such as $\rm K^{*}(892)^{\pm}$ ($\tau \sim 4$ fm/$\textit{c}$) are comparable with the lifetime of the fireball produced in heavy-ion collisions, regeneration and rescattering effects can modify the measured yield, especially at low transverse momentum.

The first results for the $\rm K^{*}(892)^{\pm}$ resonance obtained in inelastic pp collisions at $\sqrt{\text{s}}=$ 13 TeV will be shown. The $\rm K^{*}(892)^{\pm}$ has been measured at mid-rapidity via its hadronic decay channel $ \rm K^{*}(892)^{\pm} \rightarrow \rm K^{0}_{\rm{S}}+ \pi^{\pm} $, with the ALICE detector. In particular, the transverse momentum ($ p_{\rm T}$) spectrum, integrated yields, $\langle p_{\mathrm{T}} \rangle$ and ratio to stable hadrons will be presented. The $\rm K^{*}(892)^{\pm}$ results are compared with $\rm K^{*}(892)^{0}$ measurements and with commonly-used Monte Carlo models. Measurements at 13 TeV are in addition a baseline for comparison with pp measurements at other LHC energies.

Speaker: Kunal Garg (Universita e INFN, Catania (IT))

poster_v3.pdf

261 First Unambiguous Measurements of Partonic Energy Loss in Cold Nuclear Matter at E906/SeaQuest

Initial state partonic energy loss is an important benchmark of the nuclear medium properties in fixed target and heavy ion collision experiments, yet remains imprecisely determined up to now. The E906/SeaQuest experiment at Fermilab primarily measures Drell-Yan and J/psi production for p+A collisions with fixed targets H, D, C, Fe, and W. The experiment provides an ideal configuration for making unambiguous energy loss measurements based on the nuclear modification $R_{pA}$. The low energy 120 GeV proton beam from the Fermilab Main Injector amplifies the suppression, while the spectrometer's acceptance of high-$x_2$ (target $x > 0.1$) Drell-Yan events minimizes shadowing and final state effects, resulting in enhanced precision for the determination of radiation length $X_0$ and stopping power $-dE/dx$. We will present results from the Drell-Yan energy loss analysis and compare with previous experiments.

Speaker: Alexander Bernard Wickes (Los Alamos National Laboratory (US))

262 Forward Dihadron Angular Correlations in pA collisions

Dihadron angular correlations in forward $pA$ collisions have been considered as one of the most sensitive observables to the gluon saturation effects. In general, both parton shower effects and saturation effects are responsible for the back-to-back dihadron angular de-correlations. Recent developments have allowed to incorporate the so-called parton shower effect, namely the Sudakov effect, into the small-$x$ formalism [1-3]. This, in particular, will enable us to go beyond the saturation dominant region, and conduct calculations for dihadron correlation in a much wider regime where both saturation effects and Sudakov effects are important.

In this paper [4], we carry out the first detailed numerical study in this regard, and find a very good agreement with previous RHIC $pp$ and $dAu$ data. This study can help us to establish a baseline in $pp$ collisions which contains little saturation effects, and further make predictions for dihadron angular correlations in $pAu$ collisions, which will allow to search for the signal of parton saturation.

[1] A. H. Mueller, B. W. Xiao and F. Yuan, Phys. Rev. D 88, 114010 (2013); Phys. Rev. Lett. 110, no. 8, 082301 (2013).

[2] P. Sun, C.-P. Yuan and F. Yuan, Phys. Rev. Lett. 113, no. 23, 232001 (2014); Phys. Rev. D 92, no. 9, 094007 (2015).

[3] A. H. Mueller, B. Wu, B. W. Xiao and F. Yuan, Phys. Rev. D 95, no. 3, 034007 (2017).

[4] A. Stasto, S. Y. Wei, B. W. Xiao and F. Yuan, to appear.

Speaker: Shu-yi Wei (Ecole Polytechnique)

posterfinal.pdf

263 Forward instrumentation for the ALICE Upgrade: the Fast Interaction Trigger and the FoCal proposal

Two additions to the forward instrumentation of ALICE will be described: the new Fast Interaction Trigger (FIT) and the Forward Calorimeter (FoCal). The former will be installed during the Long Shutdown 2 (2019/2020), while the latter is proposed for Long Shutdown 3 (2024-2026).

The FIT detector provides a fast trigger, a precise collision time measurement for time-of-flight based particle identification, and will be the main ALICE luminometer. FIT will measure an unbiased multiplicity distribution in the forward direction needed for the determination of the centrality and of the event plane in heavy-ion collisions. FIT is composed of two Cherenkov detector arrays (T0+) with a time resolution in the 20-50 ps range and a large, sectored scintillator ring (V0+). The T0+ arrays surround the beam pipe on both sides of the IP at a distance of 82 cm on the side of the muon arm, and 330 cm on the opposite side. In total, FIT will produce 208 Cherenkov signals and 48 scintillator signals, respectively.

The main goal of the FoCal proposal is to measure forward ($3.5 < y < 5$) direct photons in pp, and p--Pb collisions to obtain unique experimental constraints on proton and nuclear PDFs in a new region of low $x$ ($10^{-5} - 10^{-6}$). In addition it provides measurements of neutral mesons, two particle correlations, and jets in p+p, p--Pb and (partially) in Pb--Pb. The direct photon measurement requires a new electromagnetic calorimeter with extremely high granularity. The design principle of the high-resolution SiW sandwich calorimeter will be presented and results from the ongoing R$\&$D program with test beams will be shown. The detector will be instrumented with Si-pad sensors with analog readout and a MAPS-based digital pixel readout. The test beam results include linearity and energy resolution measurement, but also three-dimensional shower distributions on the sub-millimeter scale and the corresponding excellent position resolution.

Speaker: Prof. Ian Gardner Bearden (University of Copenhagen (DK))

264 Forward Photon Measurements at the LHC and the FoCal Proposal in ALICE

A Forward Calorimeter (FoCal) is proposed as an addition to the ALICE experiment to be installed during Long Shutdown 3 (2024-2026).

The main goal of the FoCal proposal is to measure forward (3.5 < y < 5) direct photons in pp and p-Pb collisions to obtain unique experimental constraints on proton and nuclear PDFs in a new region of low x $(10^{-5} - 10^{-6})$. It provides measurements of neutral mesons, two particle correlations, and jets in p+p, p-Pb and (partially) in Pb-Pb collisions. The direct photon measurement requires a new electromagnetic calorimeter with extremely high granularity. We will discuss the physics case of this proposed detector. The design principle of the high-resolution silicon-tungsten (Si-W) sandwich calorimeter will be presented and results from the ongoing R&D program with test beams will be shown. The detector will be instrumented with Si-pad sensors with analog readout and on a Monolithic Active Pixel Sensor (MAPS) based digital pixel readout. The test beam results include linearity and energy resolution measurements, but also three-dimensional shower distributions on the sub-millimeter scale contributing to the excellent position resolution.

Speaker: Norbert Novitzky (Helsinki Institute of Physics (FI))

FocalPoster.pdf

265 Forward rapidity open heavy flavor measurements at PHENIX in $p$+$p$ and Au+Au collisions

Heavy flavor and quarkonia productions are important hard probes to test Quantum Chromodynamics (QCD) and study the properties of the Quark Gluon Plasma (QGP) created in high energy heavy ion collisions. The energy loss of quarks and gluons in the QGP is expected to have flavor/mass dependence. The Forward Silicon Vertex Tracker (FVTX), installed in the PHENIX detector in 2012, enables the displaced vertex measurement of muons in the rapidity range of $1.2<|y|<2.2$, allowing the separation of charm and bottom quark decays. A new method to separate the charged pion, kaon and proton yields based on the displacement vertex distribution of prompt hadrons and their muon decays is also possible.
We will present the current status of the analysis of B- and D-meson semi-leptonic decayed, the B$\rightarrow J/\psi$ production, and identified hadron yields in $p$+$p$ and Au+Au collisions at $\sqrt{s_{NN}}$=200 GeV.

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

QM18_poster_XuanLi_ver3.pdf

266 From Debye screening to regeneration and jet quenching: charmonium production in pp and PbPb collisions with the CMS detector

The understanding of charmonium production in PbPb collisions requires the inclusion of many phenomena such as dissociation in the QGP, partonic energy loss, statistical recombination, on top of cold nuclear matter effects (modifications of nPDFs, initial-state energy loss, nuclear break-up). In this talk, final results on prompt J/$\psi$ and $\psi(2S)$ production, based on the pp and PbPb data collected at 5.02 TeV by CMS in 2015, are reported. The prompt J/$\psi$ results in PbPb collisions, including the cross section and the nuclear modification factor R$_{\mathrm{AA}}$, are presented single- and double-differentially over a wide kinematic and centrality range ($3< p_T<50$ GeV /c, |y|<2.4, and fine event-centrality intervals). The results are compared to those obtained at 2.76 TeV over a similar kinematic range. Final prompt $\psi(2S)$ R$_{\mathrm{AA}}$ results at 5.02 TeV are also presented, showing a stronger suppression of the excited state as compared to the ground state in all measured bins. Finally, exploratory studies of jets containing J/$\psi$ mesons are shown.

Speaker: Émilien Chapon (CERN)

chapon_QM18.pdf

267 Functional QCD: From Correlators to Thermodynamics

Functional continuum methods provide ab-initio access to the non-perturbative regime of quantum chromodynamics. In particular, they allow accessing non-zero temperatures and densities, making them an ideal tool to access QCD's phase diagram. The functional QCD collaboration [1] aims to map out the phase diagram in a systematic manner. Within the functional renomalization group (FRG) approach, remarkable progress has been achieved over the last few years.

In this talk I will briefly review results on chiral symmetry breaking and confinement at vanishing and finite temperature [2-5]. A particular challenge within the functional approaches is the extraction of the equation of state from correlation functions. I will report on recent progress and present first results on the trace anomaly as well as the pressure.

References:
[1] fQCD Collaboration, J. Braun, L. Corell, A. K. Cyrol, W.-J. Fu, M. Leonhardt, M. Mitter, J. M. Pawlowski, M. Pospiech, F. Rennecke, N. Wink
[2] M. Mitter, J. M. Pawlowski, and N. Strodthoff, arXiv:1411.7978 [hep-ph], Phys. Rev. D91, 054035 (2015)
[3] A. K. Cyrol, L. Fister, M. Mitter, J. M. Pawlowski, and N. Strodthoff, arXiv:1605.01856 [hep-ph], Phys. Rev. D94, 054005 (2016)
[4] A. K. Cyrol, M. Mitter, J. M. Pawlowski, and N. Strodthoff, arXiv:1706.06326 [hep-ph]
[5] A. K. Cyrol, M. Mitter, J. M. Pawlowski, and N. Strodthoff, arXiv:1708.03482 [hep-ph]

Speaker: Anton K. Cyrol (University of Heidelberg)

268 Glasma calculation of energy-momentum tensor correlations at early times

We provide an analytical calculation of the covariance of the energy-momentum tensor of the glasma in heavy ion collisions at tau=0+. This is done in the McLerran-Venugopalan model. We then implement its proper time evolution, providing the initial conditions for the subsequent hydrodynamical evolution of the system. Quantities such as the initial viscosity of the Quark Gluon Plasma can also be computed. Incidentally, as part of our calculations we obtain interesting results such as the correlator of four Wilson lines in the adjoint representation, which we derive for the first time in the most general case.

Speaker: Pablo Guerrero Rodríguez (UGR)

269 Global Polarizations of Phi-meson and Lambda in Heavy Ion Collisions

In non-central relativistic heavy ion collisions, the created matter possesses a large initial orbital angular momentum. Particles produced in the collisions could be polarized globally in the direction of the orbital angular momentum due to spin-orbit coupling. Recently, the STAR experiment has presented the polarization signals for Λ hyperons and possible spin alignment signals for phi mesons. These results opened a new direction for better understanding the medium properties in such collisions.
In this talk, we will present the results of our study on the polarizations of both phi-mesons and Lambda hyperons. A multi-phase transport (AMPT) model is used in our analysis, and these results will be compared with published data. We will focus on the effects of finite experimental coverage on the global polarizations

Speaker: Mr Shaowei Lan (Central China Normal University)

QM18poster_Shaowei.pdf

270 Hadron gas with repulsive mean field

We study the thermodynamics of hadronic matter using the hadron
resonance gas model where the repulsive interactions between baryons
are modeled using the mean field approach.

We have shown [1] that repulsive interactions are especially important
when considering the higher order fluctuations. We now extend the
treatment of [1] to cover not only ground state baryons but heavier
resonances too, include the resonance states predicted by lattice
calculations and relativistic quark models. We evaluate both the
equation of state and the higher order fluctuations and correlations
of baryon number and strangenss, and compare the results with the most
recent lattice results. After fixing the magnitude of nucleon-nucleon
repulsion from the nucleon-nucleon scattering phase shift, we study
how different repulsion between ground state baryons and resonances on
one hand, and between strange and non-strange baryons on the other,
affect the EoS and fluctuations.

In fluid dynamical and hydrid calculations such a a constrained
extension of conventional hadron resonace gas model is important for
consistent matching of fluid with lattice QCD EoS to hadronic
ensembles.

[1] Huovinen and Petreczky, arXiv:1708.00879

Speaker: Pasi Huovinen (University of Wroclaw)

Poster.pdf

271 Harmonic flow with self-consistent bulk viscous corrections

One of the most spectacular observations in heavy ion physics has been that thermalization may occur in small system collisions. For example, harmonic flow coefficients vn(pT) measured in high multiplicity p+A reactions are well reproduced by viscous hydrodynamics calculations. Small system collisions in fact serve as good tests of hydrodynamics because they should be more difficult to thermalize; in other words, shear stress and bulk pressure corrections are expected to be larger than in A+A collisions.

At freezeout, shear stress and bulk pressure manifest as nonthermal $\delta f$ corrections to the particle distributions. Hydrodynamic variables cannot fix the momentum dependence of the corrections, nor how these vary with hadron species. Therefore, to compute observables, hydro calculations rely on a model for $\delta f_i$. In practice, ad hoc postulated forms are used based on Grad's quadratic ansatz, completely disregarding the microscopic dynamics of the system. On the other hand, a self-consistent set of corrections can be obtained from kinetic theory, which depend on the scattering rates between the various species.

Self-consistent shear viscous corrections can generate a characteristic meson vs baryon difference in harmonic flow coefficients, much akin to quark number scaling. The difference arises because meson-meson cross sections tend to be smaller than meson-baryon cross sections (additive quark model). It is not yet known, however, how bulk viscosity and self-consistent bulk corrections affect harmonic flow. This is especially interesting in small systems because bulk pressure can be large. Extending the work of Molnar and Wolff (PRC95, 024903) we calculate self-consistent bulk viscous corrections in a multi-species hadron gas. Then, we use the self-consistent corrections to calculate harmonic flow observables in p+Pb collisions at the LHC, and show how bulk viscosity manifests in the momentum and species dependence of the harmonic flow coefficients.

Speaker: Denes Molnar (Purdue University)

DMolnar_qm2018.pdf

272 Heavy flavour dynamics in event-by-event viscous hydrodynamic backgrounds

Heavy flavour probes provide important information about the in-medium properties of the quark gluon plasma produced in heavy-ion collisions. In this work, we investigate the effects of (2+1)d event-by-event fluctuating hydrodynamic backgrounds on the nuclear suppression factor and momentum anisotropies of heavy flavour mesons and non-photonic electrons [1,2]. Using the state-of-the-art D and B mesons modular simulation code (the so-called "DAB-Mod"), updated recently with heavy-light quark coalescence, we perform a systematic comparision of different transport equations, including a few energy loss models - with and without energy loss fluctuations - and a relativistic Langevin model with different drag parametrisations. We present the resulting D and B mesons $R_{AA}$, $v_2$, $v_3$ and $v_4$ as well as their multiparticle cumulants, in Au-Au collisions at 200 GeV and Pb-Pb collisions at 2.76 TeV and 5.02 TeV, and compare them to the latest experimental data. We also study the linearity of the resulting heavy meson and soft hadron flow correlations, as new experimental observables that could provide greater insight into flow fluctuations, and compare for the first time our predictions with ALICE preliminary measurements of D meson $v_2$ vs $q_2$ in Pb-Pb collisions at 5.02 TeV [3].

[1] C. Prado, J. Noronha-Hostler, R. Katz, A. Suaide, J. Noronha and M. Munhoz, Nucl. Phys. A 967 (2017) 664-667 [arXiv:1704.04654].
[2] C. Prado, J. Noronha-Hostler, R. Katz, A. Suaide, J. Noronha and M. Munhoz, accepted in Phys. Rev. C [arXiv:1611.02965].
[3] ALICE collaboration, presentation at QM 2017, https://indico.cern.ch/event/576735/contributions/2565849/.

Speaker: Dr Roland Katz (University of São Paulo)

poster_katz_HF_QM_2018.pdf

273 Heavy hadrons production by coalescence in pp and AA collisions at RHIC and LHC

The hadronization process of heavy hadrons with botttom and charm quarks, especially for baryons $\Lambda_{c}$ and $\Lambda_{b}$, in a dense QGP medium is largely not understood.
We present within a coalescence plus fragmentation model the predictions for $D_{0}$, $D_{s}$, $\Lambda_{c}$, $B$ and $\Lambda_{b}$ and the related baryon to meson ratios at RHIC and LHC in a wide range of transverse momentum region up to 10 GeV [1].
We will discuss how our model can predict values for $\Lambda_{c}/D_{0}$ and $\Lambda_{b}/B$ of the order of $O(1)$, which is much larger than the expectations from fragmentation, and in agreement whit early data from STAR collaboration [2].
Furthermore the same approach can be employed to predict baryon to meson ratio $\Lambda/K$ [3], $\Lambda_{c}/D^{0}$ in $pp$ collisions assuming that at the LHC top energies there can be the formation of QGP matter.
We find considerable volume effects that significantly reduce the ratios but still predict quite larger values with respect to fragmentation, again in agreement with recent data from ALICE in $pp$ collisions [4]. A comparison to other coalescence models and thermal models is discussed.

[1] S. Plumari, V. Minissale, S.K. Das, and V. Greco, arXiv:1712.00730 [hep-ph]
[2] STAR Collaboration, Nucl.Phys. A967 (2017) 620-623
[3] V. Minissale, F. Scardina, and V. Greco, Phys. Rev. C 92, 054904 (2015)
[4] A. Grelli, ALICE Coll., plenary talk Strangeness in Quark Matter 2017, Utrecht

Speaker: Vincenzo Minissale

Minissale_QM2018.pdf

274 Heavy quark energy loss and longitudinal dependent final states in $\sqrt{s_\text{NN}} = 5.02$ TeV PbPb collisions

Heavy flavor $R_\text{AA}$ and $v_n\{m\}$ have been previously calculated in an event-by-event framework at mid-rapidity [1,2]. Those results showed that exploring new observables in the heavy flavor sector can lead to further constraints on the properties of the QGP. Furthermore, longitudinal dependence of the heavy flavor observables has not yet been explored. In this work we expand the previous framework to a (3+1)D smooth viscous hydrodynamic medium background. We obtain D$^0$ meson nuclear modification factor and elliptic flow predictions for rapidity bins in the range $-4.8 \leq \eta \leq 4.8$ for $\sqrt{s_\text{NN}} = 5.02$ TeV PbPb collisions. We also study the effects of energy loss fluctuations on the $v_n$ cumulants using event-by-event hydrodynamics.

[1] Caio A. G. Prado, Jacquelyn Noronha-Hostler, Roland Katz, Jorge Noronha, Marcelo G. Munhoz, Alexandre A. P. Suaide, Nuclear Physics A967 (2017), 664-667 [arXiv:1704.04654].

[2] Caio A. G. Prado, Jacquelyn Noronha-Hostler, Roland Katz, Jorge Noronha, Marcelo G. Munhoz, Alexandre A. P. Suaide, accepted in Phys. Rev. C [arXiv:1611.02965].

Speaker: Dr Caio Prado (Central China Normal University (CN))

PCaio_poster.pdf

275 Heavy quark transport in a hybrid Boltzmann + Langevin approach

Heavy quarks produced in relativistic heavy-ion collisions have proven to be sensitive to the properties of quark-gluon plasma (QGP) through which they propagate. Current measurements of open charm in heavy-ion collisions show unexpectedly large momentum anisotropies and small nuclear modification factors, posing a challenge for the theoretical understanding of the nature of coupling between heavy quark and the medium.

Linearized Boltzmann transport and Langevin diffusion are two popular kinetic models for heavy quark in-medium propagation. However, both of these approaches also suffer from shortcomings, i.e. Langevin diffusion is only fully applicable for heavy quarks experiencing small momenta transfer and vice versa a linearied Boltzmann transport approach with perturbative matrix elements works best in the high momentum transfer limit. In this work, we develop a hybrid heavy quark transport model that combines the strengths of each approach: heavy quarks are evolved with Langevin diffusion using an empirical diffusion constant, while rare but important scattering processes are described using linearized Boltzmann equations with perturbative matrix elements. This Langevin component is a complementary contribution to the Boltzmann component when perturbative calculation may be inadequate to describe all the interactions. Both elastic and inelastic scatterings are included in the Boltzmann component. The Landau-Pomeranchuk-Migdal effect is treated effectively via a gluon formation time and detailed balance is imposed between gluon emission and absorption. Finally, the QGP evolution is obtained by a state-of-the-art relativistic viscous hydrodynamic calculation.

With this hybrid model, we study heavy flavor momentum anisotropies, nuclear modification factor, and correlation observables in A-A collisions at RHIC and LHC energies. Comparing to available D and B meson data, we constrain the diffusion constant of the Langevin component.

Speaker: Weiyao Ke (Duke University)

poster-WK.pdf

276 High-Energy Jet Interaction Monte Carlo for the Future Generations: HIJING++

The high luminosity (HiLumi) upgrade of the Large Hadron Collider will
enable us for more detailed, high-precision experimental analysis of
the heavy ion collisions. Testing both the new theoretical models and
performing high-statistics simulations require novel, easy-to-use,
fast, extendable generators.

The recently developed HIJING++ version is based on the latest version
of PYTHIA8 and contains all the nuclear effects has been included in
the final HIJING2.552 version, including a new version of the shadowing
parametrization and jet quenching module.

Results with the HIJING++ are presented for high-energy heavy ion
collisions from small to large systems from pp to AA collisions,
including the recent XeXe and PbPb data. We also present the extended
performance and benchmark test of the generator.

Speaker: Mr Gabor Biro (Hungarian Academy of Sciences (HU))

GaborBiro_QM18.pdf

277 Higher harmonics and flow at FAIR energies

In this presentation we make comparisons between hydrodynamic behavior in UrQMD/CASCADE [1], UrQMD/HYDRO, AMPT and Chaos Many-Body Engine [2] Au+Au simulated events at CBM-FAIR energies. We analyze the properties of different flow streams classes [1] and of the Fourier coefficients in the mentioned interaction models as a function of incident energy, rapidity and impact parameter.
[1] Danut Argintaru, Calin Besliu, Alexandru Jipa, Tiberiu Esanu, Valerica Baban, Madalin Cherciu, and Valeriu Grossu, Flow shapes and higher harmonics in anisotropic transverse collective flow, Eur. Phys. J. A (2017) 53: 6;
[2] I.V. Grossu, C.Besliu, D.Felea, , Al.Jipa, High precision framework for Chaos Many-Body Engine, March 2013 Computer Physics Communications 185(4)

Speaker: Dr Danut Argintaru (Constanta Maritime University, Romania)

ArgintaruPosterPresentationlast.pdf

278 Hydrodynamic fluctuations and long time tails of a baryon charged expanding fluid

Recent studies of hydrodynamic fluctuations in rapidly expanding fluids suggest the existence of a universal renormalization which characterizes the long time behaviour of the equilibrium correlators of energy and momentum and transport coefficients. These results were obtained by assuming zero densities of conserved charges. In this work we study the effects of hydrodynamic fluctuations when the chemical potentials conjugated to the conserved charges are turned on. We study the small frequency behavior of different response functions using stochastic fluid dynamics. We obtain a number of model independent results, including the long-time tail of different transport coefficients, and the leading non-analyticity of the correlators of energy, momentum and particle density for a system undergoing Bjorken flow. When applying our formalism to the lattice QCD equation of state at finite chemical potential we find lower bounds on the heat conductivity, shear and bulk viscosities. These bounds are weakly dependent on assumptions regarding the range of applicability of fluid dynamics. We comment on the phenomenological consequences of our findings in Ultrarelativistic Heavy Ion Collisions

Speaker: Dr Mauricio Martinez Guerrero (North Caroline State University)

posterQM2018-martinez.pdf

279 Hydrodynamic results of a Principal Component Analysis at $\sqrt{s_{NN}}=2.76$ TeV

We perform a principal component analysis (PCA) of $v_n(p_T)$ in event-by-event hydrodynamic simulations of Pb+Pb collisions at the Large Hadron Collider. PCA is a statistical technique for extracting the dominant components in fluctuating data. It was suggested to apply it to relativistic collisions [1] in order to extract the information from event-by-event fluctuations from the two-particle correlation matrix. A generalization was proposed in [2]. Its connection to initial geometry was studied in [3,4]. Here we make a comparison with the data recently presented by the CMS collaboration [5] for elliptic and triangular flows as well as multiplicity fluctuations.

References:
[1] Rajeev S. Bhalerao, Jean-Yves Ollitrault, Subrata Pal, Derek Teaney, Phys. Rev. Lett. 114, 152301 (2015), arXiv:1410.7739
[2] P. Bozek, arXiv:1711.07773
[3] Aleksas Mazeliauskas and Derek Teaney, Phys. Rev. C 91, 044902 (2015)
[4] Aleksas Mazeliauskas and Derek Teaney, Phys. Rev. C 93, 024913 (2016)
[5] CMS Collaboration, arXiv:1708.07133

Speaker: Mr Pedro Ishida (Instituto de Física da Universidade de São Paulo)

PedroIshidaQM2018poster.pdf

280 Identification of charged kaons using kink topology in pp and Pb-Pb collisions with ALICE at the LHC

Identification of charged kaons can be carried out using kink topology based on the two-body decay mode ($K\rightarrow \mu +\nu_\mu$) inside the volume of TPC detector. For the first time for Pb-Pb collisions, the transverse momentum spectra of charged kaons are measured from their decay daughters using kink topology with the new Run 2 data at $\sqrt{\it{s}_{NN}} = 5.02$ TeV for different centrality classes. Based on the same technique, the transverse momentum spectra of the charged kaons for the minimum bias pp collisions at $\sqrt{\it{s}} = 5.02$ TeV are also measured and the collision energy dependence is studied. Using MC simulated data, the geometrical acceptance of decaying kaons as well as the kink reconstruction efficiency inside the TPC detector have been studied in order to obtain the corrected charged kaons spectra.

Speaker: Nur Hussain (Gauhati University)

poster_ID_257_Nur_Hussain.pdf

281 Impact of CMS dijets on EPPS16 nuclear PDFs with non-quadratic reweighting

The CMS measurement of the dijet pseudorapidity and transverse momentum distributions in pPb versus pp collisions at 5.02 TeV provides a direct constraint on nuclear gluon PDFs in a wide range of $x$ and $Q^2$ [CMS-PAS-HIN-16-003]. We report on the impact of these data on the EPPS16 nuclear PDFs [Eur.Phys.J. C77, 163]. For this, we have devised a non-quadratic extension of the Hessian PDF reweighting method [JHEP 1412, 100], which now more accurately reflects the impact of a dataset on PDFs. Based on the (preliminary) CMS data on the pPb/pp ratios of normalized dijet cross sections, we predict that the uncertainty in the nuclear gluon modification can be significantly reduced especially in the antishadowing region.

Speaker: Petja Paakkinen (University of Jyväskylä)

Poster_Paakkinen.pdf

282 Impact of magnetic field fluctuations on the CME in small systems

Many great efforts have been made to investigate the Chiral Magnetic Effect (CME), which replies on the existence of extremely large electromagnetic fields in relativistic heavy-ion collisions. However, the recent CMS measurements in small systems challenge the traditional CME interpretation, indicating that the dominant contribution to the CME observable of charge azimuthal correlation ($\gamma=$) may not be related to the CME in p+Pb and Pb+Pb collisions.

In this work, we investigate the properties of the electromagnetic fields in small systems by using a multiphase transport (AMPT) model [1]. We find that compared to A+A collisions, the magnitudes of absolute electric and magnetic fields in small systems are comparable. We show that the correlation of $$ between the magnetic field direction and the particant plane angle is strongly suppressed in high-multiplicity events, but strongly correlated in parallel in low-multiplicity events. It indicates that the traditional CME observable $\gamma$ is not valid to study the CME in high-multiplicity events. However, the strong correlation in low-multiplicity events can reduce or even change sign of the traditional CME observable, which is qualitatively consistent with the recent event-shape engineering measurement from the CMS [2]. Therefore, we suggest searching for a possible CME signal in small systems with low multiplicities.

[1] X. L. Zhao, Y. G. Ma and G. L. Ma, [arXiv:1709.05962 [hep-ph]].

[2] A. M. Sirunyan et al. [CMS Collaboration], [arXiv:1708.01602 [nucl-ex]].

Speaker: Xinli Zhao (Shanghai Institute of Applied Physics, Chinese Academy of Scien)

Xinli Zhao_QM2018.pdf

283 Implications from GW170817 and I-Love-Q relations for relativistic hybrid stars

Gravitational wave observations of GW170817 placed bounds on the tidal deformabilities of compact stars allowing one to probe equations of state for matter at supranuclear densities. Here we design new parametrizations for hybrid hadron-quark equations of state and test them against GW170817. We find that GW170817 is consistent with the coalescence of a binary hybrid star-neutron star. We also find that the I-Love-Q relations for hybrid stars agree with those for realistic neutron stars and quark stars within ∼3% for both slowly and rapidly rotating configurations [1]. We extend this initial study that used multipolytrope EoS and piecewise constrant speed-of-sound modeling by a more realistic equation of state [2] with a strong deconfinement phase transition [2].

[1] V. Paschalidis et al., arxiv:1712.00451
[2] M. Bejger et al., A&A 600, A39 (2017).

Speaker: Prof. David Blaschke (University of Wroclaw)

Blaschke-Poster_Venice-2.pdf

284 In-medium spectral properties of light hadrons in an arbitrary magnetic field

Quantum Chromodynamics in the presence of intense magnetic field reveals exotic phenomena
like chiral magnetic effect, magnetic catalysis, inverse magnetic catalysis, vacuum
superconductivity etc. Such a strong magnetic field is expected to be produced in non-central
relativistic heavy ion collision experiments at RHIC and LHC. So, the study of ``strongly"
interacting hot and/or dense matter under external magnetic field has become one of the
most important topics of research since a decade. In particular, the study of the
properties of mesons at finite temperature and/or density in an external magnetic field
is important in order to extract information about chiral phase transition parameters.

In this contribution, we will present the medium modification of pions and rho mesons under
an arbitrary external magnetic field. The one-loop self energies of $\pi$ and $\rho$ are calculated
using effective field theoretical techniques taking nucleon and pions as the loop particles
respectively. The proton and charged pion propagators are modified due to the magnetic field
using the full Schwinger proper time propagator. From the
in-medium self energies, we obtained the effective mass and dispersion relations for $\pi$
and $\rho$ at the pole of the complete propagator calculated from the Dyson-Schwinger equation.
We have also studied the spectral function as well as the detailed analytical structure
of the self energy function of $\rho$. A non-trivial effect of magnetic field on these mesonic
properties is observed.

Speaker: Mr Snigdha Ghosh (Variable Energy Cyclotron Centre, Kolkata, India)

snigdha_qm_2018.pdf

285 Inclusive full jet measurements in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV with ALICE

Measurements of the yield and structure of jets in heavy-ion collisions at different collision energies and kinematic ranges can be used to constrain jet energy loss models, and in turn give information about the structure of the quark-gluon plasma itself. ALICE reconstructs ''full'' jets with high-precision tracking of charged particles combined with calorimetric detection of neutral particles, achieving a unique kinematic range of jets down to low momenta. The status of a recent inclusive full jet measurement over a variety of jet radii and momenta in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV with ALICE will be shown.

Speaker: James Mulligan (Yale University (US))

Mulligan_QM2018poster.pdf

286 Inclusive Psi(2S) Suppression in p-Pb collisions with ALICE at the LHC

Quarkonia are produced in the initial hard scatterings and are useful probes to study the microscopic properties of the matter produced in the ultra relativistic heavy-ion collisions. The experimental results show that in nucleus-nucleus collisions, the charmonium yields are modified compared to the expectations based on the yields measured in proton proton interactions, scaled by the number of binary collisions. In proton-nucleus collisions this yield modification is due to the so-called Cold Nuclear Matter (CNM) effects such as shadowing, gluon saturation, parton energy loss, comover absorption. This information can be obtained from p-Pb collisions.

At LHC energies ($\sqrt{s_{\rm{NN}}}$ = 5.02 and 8.16 TeV), ALICE has observed a modification of the J/$\rm{\psi}$ yields in p-Pb collisions which can be understood assuming shadowing to be the dominant contribution. On the other hand, the $\rm{\psi}$(2S) was found to have a similar suppression as the J/$\rm{\psi}$ at forward rapidity, but it shows a much stronger suppression in the backward rapidity region. So, this behavior cannot be explained by the shadowing or energy loss only unlike J/$\rm{\psi}$. Final state mechanisms, as the comover absorption, should be playing a role in this region.

ALICE results on the measurement of $\rm{\psi}$(2S) yields and nuclear modification factor as a function of transverse momentum, rapidity and collision centrality in p-Pb $\sqrt{s_{\rm{NN}}}$ = 8.16 TeV collisions will be presented in the poster.

Speaker: Ms Jhuma Ghosh (Saha Institute of Nuclear Physics (IN))

QM2018_poster_Jhuma_final.pdf

287 Influence of final-state radiation on heavy-flavour observables in pp collisions

Initial- and final-state radiation are important processes for the physical interpretation of high-energy collisions at the Large Hadron Collider. Calculations of these perturbative QCD corrections are, however, limited to probabilistic approximations using parton shower approaches in event generators. Although this Monte-Carlo DGLAP description is nowadays state-of-the-art, there still exist significant differences on the quantitative level. To address these open questions, it is important to investigate final-state radiation processes experimentally by identifying sensitive observables.

In this study, a new transverse momentum correlation observable, the momentum imbalance between D and Dbar mesons, is identified as a sensitive tool to study final-state radiation. This is shown by using simulations with the EPOS3+HQ model and the event generator Pythia 6. The presented results will focus on heavy-flavour particles only because these are most likely pair-produced in the initial stages of the collision. With the upcoming detector upgrades for LHC Run-3, statistically significant correlation measurements of these heavy-flavour particles will become feasible. In the end, this method can be extended to pA and AA data to study several aspects of energy loss in heavy-ion collisions.

Speaker: Luuk Vermunt (Utrecht University (NL))

poster_QM2018_LuukVermunt_final.pdf

288 Initial Energy-Momentum Conservation and its Role in Particle Emission in A+A Collisions

Our presentation will be based on our recent paper [1].

We construct a new, simple model of the heavy ion collision, local in the impact parameter plane. This model can be regarded as a new realization of the ``fire-streak'' approach, originally applied to studies of lower energy nucleus-nucleus reactions.

Starting from local energy and momentum conservation, we provide a full description of the centrality dependence of pion rapidity spectra in Pb+Pb collisions at $\sqrt{s_{NN}}=17.3$ GeV. In particular we also explain the broadening of this distribution when going from central to peripheral collisions.

The results of our calculations are compared to SPS experimental data. We discuss the resulting implications on the role of energy and momentum conservation for the successive stages of the A+A collision, and for the dynamics of subsequent particle production.

A specific space-time picture emerges, where the longitudinal evolution of the system strongly depends on the position in the impact parameter (${b_x}$, ${b_y}$) plane. In non-central collisions we predict the existence of ``streams'' of excited matter moving very close to the spectator system in configuration $(x,y,z)$ space.

This picture is consistent with our earlier findings on the longitudinal evolution of the system as deduced from electromagnetic effects on charged pion directed flow [2], and can provide an explanation for specific low-$p_T$ phenomena seen in the fragmentation region of Pb+Pb collisions which we also address in this talk. We present our conclusions on the link between the initial stage of the A+A collision and the final state observables connected to strong and electromagnetic phenomena.

[1] A. Szczurek, M. Kielbowicz and A. Rybicki, Phys. Rev. C 95 (2017), 024908.

[2] A. Rybicki and A. Szczurek, Phys. Rev. C 87 (2013), 054909.

Speaker: Nikolaos Davis (Polish Academy of Sciences (PL))

QM2018_poster_firestreaks_Nikolaos_Davis.png

289 Insight into thermal modifications of quarkonia from a comparison of continuum-extrapolated lattice results to perturbative QCD

Spectral functions of quarkonia hold many information on bound states and their in-medium modifications as well as on transport properties. Determining spectral functions is subject of many calculations, in lattice QCD as well as in perturbation theory.
We compare continuum extrapolated lattice results [1] to a perturbatively determined spectral function obtained by interpolating between vacuum asymptotics at high frequencies and resummed thermal effects around the threshold [2]. Modest differences are observed, which may originate from non-perturbative mass shifts and renormalization factors. However, in the pseudoscalar channel no resonance peaks are needed for describing the quenched lattice data for charmonium at and above $T \sim 1.1T_c$. In the bottomonium case a good description of the lattice data is obtained with a spectral function containing a single thermally broadened resonance peak at $T$ up to $\sim 1.5T_c$.
The knowledge gained from the pseudoscalar channel is used to improve the studies in the vector channel [3]. In addition to information on the in-medium modification of charmonium and bottomonium bound states, this allows for continuum estimates on the temperature and quark mass dependence of heavy quark diffusion coefficients.

$[1]$ H.-T. Ding, O. Kaczmarek, A.-L. Kruse, H. Ohno, H. Sandmeyer, Continuum extrapolation of quarkonium correlators at non-zero temperature. [arXiv 1710.08858]
$[2]$ Y. Burnier, H.-T. Ding, O. Kaczmarek, A.-L. Kruse, M. Laine, H. Ohno and H. Sandmeyer, Thermal quarkonium physics in the pseudoscalar channel. JHEP 1711 (2017) 206 [arXiv 1709.07612]
$[3]$ Y. Burnier, M. Laine, Massive vector current correlator in thermal QCD. JHEP 1211 (2012) 086 [arXiv 1210.1064]

Speaker: Anna-Lena Kruse (Bielefeld University)

poster_qm.pdf

290 Interference effect between jet-induced flows in dijet events

We investigate the hydrodynamic medium response to jets in the quark gluon plasma (QGP) fluid in dijet events, in particular focusing on the interference effect between the flows induced by a back-to-back pair of jets. In high-energy heavy-ion collisions, jets deposit their energy and momentum into the QGP medium fluid via the successive interactions with the medium constituents during their propagation. The deposited energy and momentum are supposed to excite the medium fluid, and induce flows following the jets as hydrodynamic medium responses. The flow induced by the highly quenched jet develops very widely in the QGP fluid, and can affect also the medium response contribution to the structure of the opposite-side jet in dijet events.

We simulate dijet events in high-energy heavy-ion collisions by employing a coupled jet-fluid model combining jet shower transport equations and hydrodynamic equations with source terms [1]. The jet shower transport equations describe the evolution of the momentum distributions of partons in the jet showers with the medium effects, i.e., collisional energy loss, transverse momentum broadening, and medium-induced radiation. The QGP medium evolution is described by (3+1)-dimensional ideal hydrodynamic equations with source terms which transfer the energy and momentum deposited by the jet pair to the QGP fluid. We study how the interference effect between the jet-induced flows in dijet events come out in the jet-correlated particle distributions in the final state and their dependence on the event selection and background subtraction method. For the extensive studies, we also study the energy momentum deposition and induced flows by heavy quarks or jets with virtuality-ordered splittings.

Reference

[1] Y. Tachibana, N.-B. Chang, G.-Y. Qin, “Full jet in quark-gluon plasma with hydrodynamic medium response,” Phys. Rev. C 95, 044909 (2017)

Speaker: Yasuki Tachibana (Wayne State University)

qm18_poster.pdf

291 Intermittency analysis of proton density as a probe for the critical point of strongly interacting matter in NA61/SHINE

The search for experimental signatures of the critical point (CP) of strongly interacting matter is one of the main objectives of the NA61/SHINE experiment at the CERN SPS. In the course of the experiment, an energy (beam momentum 13A – 150/158A GeV/c) and system size (p+p, p+Pb, Be+Be, Ar+Sc, Xe+La) scan is performed. Proposed observables include non-monotonic fluctuations of integrated quantities, as well as local critical fluctuations connected to the critical behavior of the order parameter in the CP neighborhood, which scale according to universal power-laws.

Proton density fluctuations are investigated as a possible order parameter of the phase transition in the neighborhood of the CP by performing an intermittency analysis of the proton second scaled factorial moments (SSFMs) in transverse momentum space. A previous analysis of this kind [1] revealed significant power-law fluctuations in the NA49 heavy-ion collision experiment for the Si+Si system at 158A GeV/c. The fitted power-law exponent was consistent with the theoretically expected critical value within uncertainties, a result suggesting a baryochemical potential for the critical point in the vicinity of ~250 MeV.

The intermittency analysis is extended to systems of intermediate size as studied by NA61/SHINE, the primary candidates being the Be+Be and Ar+Sc systems at 150A GeV/c. Statistical techniques are developed for the calculation of scaled factorial moments which allow to subtract non-critical background and enhance the signal in case of low statistics. The analysis is supplemented by both critical and non-critical Monte Carlo simulations, by which one can estimate non-critical background effects on the quality and magnitude of uncertainties of the intermittency power-law fit, as well as explore the possibility of non-critical effects producing an intermittency signal.

References

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

Speaker: Ludwik Turko (University of Wroclaw (PL))

QM2018_Intermittency_poster fnl.pdf

292 Interpreting jet quenching measurements and charmonia suppression

Understanding the energy loss of partons traversing the strongly interacting matter created in heavy ion collisions is one of key goals of the heavy ion physics program. In this talk we present results of phenomenological analyses of various recent jet quenching data. The core of the model used in these analyses is based on the shift formalism which allows for an extraction of the magnitude of parton energy loss from the data with minimal assumptions on the underlying physics mechanisms. The model is capable of describing the full $p_{T}$, rapidity, and centrality dependence of the measured jet $R_{AA}$ using three effective parameters. The analysis done using this simple model can explain the shape of the modification of fragmentation functions observed in the data as well as the relation between the magnitude of the jet $R_{AA}$ and the $R_{AA}$ of charged particles. The analysis of recent data on splitting functions and fragmentation functions allows for further constrains on the role of coherence effects in the parton energy loss. Further, the analysis of charmonia suppression using this model points to a remarkable similarity between the quenching of light-quark-initiated jets and the prompt charmonia suppression. In this talk, we also discuss possible explanations of intriguing features seen in the recently published dijet asymmetry measurement by ATLAS and differences in how fragmentation patterns are modified for inclusive jets compared to those in the gamma-jet system.

Speaker: Martin Spousta (Charles University)

Spousta_QMPoster_20180507.pdf

293 Inverting the mass hierarchy of jet quenching with b-jet substructure

The two-prong substructure of the leading subjets inside a reconstructed jet opens new windows on precision constraints on the in-medium modification of parton showers. We present the first resumed calculation of the groomed soft-dropped subjet momentum sharing distribution in heavy ion collisions, and demonstrate that both the STAR data at RHIC and the CMS results at LHC can be understood in the unified framework of soft-collinear effective theory with Glauber gluon interactions. Recent advances in understanding mass effects on the QCD splitting functions enable us to apply this method for the first time to heavy flavor tagged jets, the main topic of this presentation. Theoretical predictions for the momentum sharing distribution modification of jets tagged by single and two in-jet heavy mesons will be presented. We find that in the kinematic region that will be accessed by sPHENIX in the future, or by studying jets of lower transverse momenta than currently explored at the LHC, there is a unique reversal of the mass hierarchy of jet quenching effects. Namely, the momentum sharing distribution of b-tagged jets is more strongly modified in comparison to the one for light jets. This unique feature provides a handle on mass corrections that are at present difficult to constraint using inclusive heavy meson production.

Speaker: Dr Ivan Vitev (Los Alamos National Laboratory)

294 Investigating applicability of fluid dynamics in heavy ion collisions

We investigate the applicability of fluid dynamics (FD) in relativistic heavy-ion collisions by comparing its solutions to those of the relativistic Boltzmann equation (BE) [1]. The latter can be solved numerically [2] and its FD limit is well known [3]. We consider various (2+1)-dimensional boost-invariant scenarios, with realistic initial transverse profiles of energy and particle density. By varying the system size and the cross section we then identify regions where FD is a good approximation to the BE.

We observe that the space-time evolution of energy density and fluid velocity is well described by FD for all considered values of the cross section. However, the FD shear-stress tensor starts to deviate from its BE counterpart when the Knudsen number $\rm Kn$, defined as a mean free path times the local expansion rate, exceeds a value of one.

We furthermore study the elliptic flow generated for Glauber-type initial conditions. We consider various decoupling conditions in FD and identify the $\rm Kn$ regions where the elliptic flow is generated. Decoupling at a constant $\rm Kn \sim 2-3$ gives a good agreement with the solutions of the BE when the cross section is sufficiently large, i.e., when most of the elliptic flow is generated during the evolution where $\rm Kn < 1$. With decreasing cross section most of the flow signal is generated in regions where $\rm Kn > 1$. In this case, the FD elliptic flow starts to deviate from that generated by the BE.

[1] K. Gallmeister, H. Niemi, C. Greiner, D. H. Rischke, in preparation

[2] Z. Xu and C. Greiner, Phys. Rev. C71, 064901 (2005)

[3] G. Denicol, H. Niemi, E. Molnar and D. H. Rischke, Phys. Rev. D85, 114047 (2012)

Speaker: Harri Niemi (J. W. Goethe Universität)

295 J/psi coherent photo-production at very low transverse momentum in Pb-Pb collisions at sqrt{s_{NN}} = 5.02 TeV with ALICE

A large excess in the yield of $\mathrm{J/\psi}$ at very low transverse momentum (${p}_\mathrm{T}<\mathrm{300\ MeV/}c$) and forward rapidity (2.5< $y$ <4.0) was recently reported by ALICE using the LHC Run-1 data, in Pb-Pb collisions at $\sqrt{s_\mathrm{NN}}$ = 2.76 TeV. This is suggestive of coherent $\mathrm{J/\psi}$ photo-production, similar to measurements in ultra-peripheral collisions (UPC), where the nuclei only interact electromagnetically.

During the LHC Run-2, the measurement of the very low ${p}_\mathrm{T}$ $\mathrm{J/\psi}$ at mid-rapidity (-0.9< $y$ <0.9) in the di-electron decay channel was possible thanks to the large sample of recorded Pb-Pb collisions. The central barrel detectors provide a good momentum resolution, and make the measurement sensitive to the key characteristics of $\mathrm{J/\psi}$ coherent photo-production, like the corresponding transverse momentum spectrum.

In this poster, we will present the ${p}_\mathrm{T}$-integrated and ${p}_\mathrm{T}$-dependent coherent $\mathrm{J/\psi}$ photo-production cross-section at mid rapidity in Pb-Pb collisions at $\sqrt{s_\mathrm{NN}}$ = 5.02 TeV. Our data will be discussed in comparison to the UPC measurements and model calculations. The expectations for this measurements with LHC Run-3 and Run-4 data will be discussed.

Speaker: Zhuo Zhou (University of Bergen (NO))

Poster_QM18_CohJpsi_zzhou.pdf

296 J/psi polarization in Pb-Pb collisions at sqrt(sNN) = 5.02 TeV with ALICE at the LHC

Polarization is a key observable to determine the quarkonium production mechanism in hadronic elementary collisions. Its very small value measured at the LHC has been challenging the commonly-used theoretical models and it still represents a major standing issue in the field.
On the other hand, phenomenological studies have shown that primordial quarkonium in AA interaction can be polarized by the strong magnetic field generated by the two colliding nuclei, while re-combined quarkonium is expected to be completely unpolarized.
We present a feasibility study for the pT-differential measurement of J/psi polarization in $\sqrt{s_{NN}}$ = 5.02 TeV Pb-Pb collisions at the LHC. The analysis strategy and technique are discussed and first preliminary results are presented.

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

QM2018_poster_LucaMicheletti.pdf

297 J/psi production as a function of charged particle multiplicity in pp collisions at √s = 13 TeV at forward rapidity with ALICE

In high-energy pp collisions, there can be a substantial contribution from Multi-Parton Interactions (MPI) in particle production mechanisms. In this case, several interactions at the partonic level occur in a single pp collision and this implies a correlation between the particle production and the total event multiplicity. At the LHC energies, MPI might occur at hard momentum scales, thus affecting the heavy quark production. Such an effect can be investigated by studying the correlations between heavy-flavour production and the total charged-particle multiplicity. In this poster, we will present the preliminary results of $J/\psi$ production as a function of charged-particle multiplicity in pp collisions at $\sqrt{s}$ = 13 TeV at forward rapidity (2.5$<$y$<$4) using the data collected by the ALICE detector. $J/\psi$ are reconstructed via $J/\psi \rightarrow \mu^{+} + \mu^{-}$ decay channel using the Forward Muon Spectrometer, while the charged-particle multiplicity is obtained from the Silicon Pixel Detector. Results will be compared with the perturbative Quantum Chromodynamics (pQCD) inspired models.

Speaker: Dhananjaya Thakur (Indian Institute of Technology Indore (IN))

2018-may-10-conference_presentation-qm_poster_jpsi_mult_final.pdf

298 J/Psi production as a function of charged particle multiplicity in pp collisions at √s = 2.76 and 5.02 TeV with ALICE

The quarkonium production as a function of multiplicity in proton-proton and proton-lead collisions is considered as an interesting observable to comprehend multi-parton interactions and to seek out the presence of collectiveness in the small systems. The multiplicity dependence of J/$\psi$ production has been studied in pp collisions at $\sqrt{s} = 7$ and 13 TeV and p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV by ALICE. An increase of the relative J/$\psi$ yields with the relative charged particle multiplicity is observed.

In the light of previous works, results on the multiplicity dependence of the J/$\psi$ yield in pp collisions at $\sqrt{s}$ = 2.76 and 5.02 TeV, measured at forward rapidity, will be presented for the first time in this poster. They will be compared to the available ALICE measurements obtained in pp collisions at $\sqrt{s}$ = 7 and 13 TeV to explore the energy dependence of this correlation. The results will also be compared with theoretical model predictions.

Speaker: Ms Anisa Khatun (Aligarh Muslim University (IN))

2018-may-10-conference_presentation-qm2018_poster_anisa-v6.pdf

299 J/psi production at mid-rapidity in p--Pb collisions with the ALICE detector

Relativistic heavy-ion collisions are the unique tool to study the properties of the deconfined state of quarks and gluons, Quark-Gluon Plasma (QGP). Dissociation of J/$\psi$ is thought as one of the strong evidences of QGP formation. At LHC energy, regeneration of J/$\psi$ from thermalized charm quarks is also expected to be pronounced.
In order to discuss the QGP effects in relativistic heavy-ion collisions, the understanding of cold nuclear matter effects such as gluon shadowing, gluon saturation, and nuclear absorption is crucial.
Proton--nucleus collisions are suited for the study of the cold nuclear matter effects.
Furthermore, the charged particle multiplicity dependence of J/$\psi$ production provides an insight on the underlying physics such as Multi-Parton Interactions (MPI).
p--Pb collisions were recorded in 2016 with the ALICE detector at the LHC. In this poster, we will show the status of J/$\psi$ analysis in p--Pb collisions which includes the centrality dependence of the nuclear modification factor ($R_{\rm{pPb}}$, $Q_{\rm{pPb}}$) and the charged particle multiplicity dependence of J/$\psi$ yield.

Speaker: Shinichi Hayashi (University of Tokyo (JP))

QM2018Poster_shayashi_v4_1.pdf

300 Jet energy loss in a flowing plasma

We present new results on the energy loss of light partons traversing a highly dynamical strongly coupled quark-gluon plasma. As QGP has large gradients in both temperature and the fluid velocity, it is crucial to study energy loss without assuming a homogeneous plasma, especially as it is known that energy loss depends on the plasma evolution in a non-local way. In a holographic description, we consider several subsequent improvements of the hydrodynamic background by keeping increasing orders in the gradient expansion. Already for varying temperature and velocity profiles and ideal hydrodynamics, the energy loss is considerably modified. However, this description is limited to very small gradients and it is hence necessary to include viscous corrections. We present a numerical analysis of jet energy loss in a boost-invariant and transversely-expanding droplet of QGP. We find that depending on the direction of the fluid flow, the velocity gradients can change the distance a parton can travel by a factor of two, which would correspond to changing the coupling constant by a factor of more than fifty.

Speaker: Wilke van der Schee (MIT)

Poster Quark Matter Final.pdf

301 Jet modification by MPI and determining the characteristic jet size based on multiplicity dependent jet-shape analysis

High multiplicity events of small colliding systems at high c.m.s. energies show similar collective features as those observed in events
of heavy ion collisions with comparable multiplicities, such as long-range near-side correlations and v_n coefficients [1,2]. Whether this behaviour may be attributed to the presence of a deconfined state in small systems is an open question.

Recent analyses of pp and p-Pb collisions also show an universal enhancement of heavy-flavour particles [3], that is usually attributed to multiple parton interactions (MPI) and higher gluon radiation associated with short distance production processes [4,5]. While we cannot expect to be able to apply hard probes on the medium created in the collisions of small systems, phenomena like MPI or Color reconnection (CR) may cause a modification of the jet shapes that can in principle be experimentally accessible.

We have carried out extensive studies using Monte Carlo event generators. We give predictions for multiplicity-dependent jet structures, and propose a way to validate the presence and extent of effects such as MPI or Color Reconnection, based on the detection of non-trivial jet shape modification in high multiplicity events. We also propose a definition of a characteristic jet size measure that is independent of multiplicity [6].

References:
[1] CMS Coll., JHEP 09 (2010) 091
[2] CMS Coll., Phys.Rev.Lett. 112 (2014) 082301
[3] ALICE Coll., JHEP 1608 (2016) 078
[4] S. Porteboeuf, R. Granier de Cassagnac, Nucl.Phys.Proc.Suppl. 214 (2011) 181
[5] T. Sjostrand, M. van Zijl, Phys.Rev.D 36 (1987) 2019.
[6] Z.V., https://indico.cern.ch/event/684046/contributions/2809561/attachments/1571304/2478958/Zoltan_Varga_ZimanyiSchool.pdf

Speaker: Robert Vertesi (Hungarian Academy of Sciences (HU))

pyJetStruct-vertesi-QM18-final.pdf

302 Jet reconstruction and measurements of jet substructure in heavy ion collisions with CMS

Measurements of jet substructure are useful tools for the understanding of the mechanism of jet quenching. Using those multi-scale probes, the results of jet fragmentation functions, jet shape and jet spectra could be used to search for possible medium response and to quantify the properties of the Quark-Gluon Plasma within the theoretical models. In this poster, jet reconstruction, background subtraction, and jet substructure extraction methods used in CMS analyses are presented. The results are compared to theoretical model calculations and implications from various jet substructure measurements using electroweak bosons, hadrons and jets are also summarized.

Speaker: Yen-Jie Lee (Massachusetts Inst. of Technology (US))

303 K*(892)± production in pp collisions at √s = 5.02 and 8 TeV with ALICE at the LHC

Resonances are useful tools to study the properties of the hadronic medium produced in high energy heavy-ion collisions, due to their short lifetime. They are good candidates to probe the interplay of particle re-scattering and regeneration in the hadronic phase. In particular, the K$^{*}(892)^{\pm}$ resonances are important because of their very short lifetimes ($\sim$ 4 fm/$\it c$) which are comparable to that of the fireball. The K$^{*\pm}$ is reconstructed via a two-step decay process: the resonance undergoes a strong decay to K$^{0}_{S}$ + $\pi^{\pm}$ and then the K$^{0}_{S}$ decays weakly to $\pi^{+}$ + $\pi^{-}$. Measurements in pp collisions constitute a reference for the measurements in p-Pb and Pb-Pb collisions at the same center-of-mass energy and contribute to the study of the energy and multiplicity dependence of particle production in pp collisions. The results presented here include the transverse momentum ($\it p_{\rm T}$) spectra, integrated yields and $\langle p_{\rm T} \rangle$ for K$^{*\pm}$ in pp collisions at $\sqrt{s}$ = 5.02 and 8 TeV. The results are compared to the measured production of neutral K$^{*}(892)$ and with the predictions from commonly used QCD-inspired event generators.

Speaker: Ms Pragati Sahoo (Indian Institute of Technology Indore (IN))

qm18_poster_PragatiSahoo.pdf

304 Kaon flow at HADES Au+Au @ 1.23A GeV collisions

We present the first preliminary results on direct and elliptic flow of particles with strange content ($K^0_s$ and $K^+$) in Au+Au collisions at $1.23\,\mathrm{A GeV}$ measured with HADES. The study of strange particle flow in heavy-ion collision is according to the theory sensitive to in-medium hadron modifications. Kaon flow was seldom measured at such low center-of-mass energy region $\sqrt{s_{NN}} = 2.42\,\mathrm{GeV}$ due to sub-threshold production of strangeness. Thanks to the quantity of $2.6$ bilion events of the $40\,\%$ most central collisions this study is now possible. The obtained flow parameters are compared with previously published world data as well as with flow of non-strange particles. The agreement of measurement with simulations using several transport codes is also checked.

Speaker: Lukáš Chlad (Nuclear Physics Institute of the CAS)

chlad_kaon_QM2018_v3_A0.pdf

305 Kaon Isospin Fluctuation in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV with ALICE at LHC

The first measurement of isospin fluctuations in the kaon sector is reported in Pb-Pb collisions at $\sqrt{s_{NN}}=$ 2.76 TeV, recorded with the ALICE detector. A robust statistical observable $\nu_{dyn}$ was used to extract the novel isospin fluctuations from the distributions of neutral and charged kaons as a function of collision centrality. The results show a significant variation in the behaviour of $\nu_{dyn}$ in data when compared to existing Monte-Carlo models such as HIJING and AMPT. The details of the analysis and systematic studies in the extraction of $\nu_{dyn}$ and its centrality dependence in both data and Monte-Carlo models are reported.

Speaker: Mr Ranjit Nayak (IIT Bombay)

2018-may-10-conference_presentation-kaon_isospin_fluct_qm18_posterv5.pdf

306 Kinetic equations and anisotropic hydrodynamics for quark and gluon fluids

Relativistic hydrodynamics is one of the fundamental tools used to interpret the data measured in heavy-ion collision experiments at RHIC and the LHC. Despite the success of second order viscous hydrodynamics in reproducing physical observables, there exist still theoretical problems that may question validity of this approach for description of heavy-ion collisions. The main source of the problems are large gradients and fast longitudinal expansion which produce very large anisotropic pressure corrections to local equilibrium. One way to avoid this problem is the use of anisotropic hydrodynamics, a framework where large pressure corrections are taken into accound already in the leading order of the hydrodynamic expansion [1-4].

We have recently extended the anisotropic hydrodynamics description to the case of a non-conformal mixture of quark and gluon fluids studied in a one-dimensional and boost-invariant setup with quantum statistics effects included. We compared the predictions of the coupled kinetic equations treated in the relaxation time approximation with anisotropic hydrodynamics results, founding a very good agreement [5].

Our numerical results also illustrate how a non-equlibrium mixture approaches hydrodynamic regime described by the Navier-Stokes equations with appropriate forms of the kinetic coefficients. The numerical studies of the ratio of the longitudinal and transverse pressures show, to a good approximation, that it depends on the ratio of the relaxation and proper times only. This behaviour is connected with the existence of an attractor for conformal systems [6].

[1] W.Florkowski, R.Maj, R.Ryblewski, M.Strickland, Phys. Rev. C87 (2013) 034914
[2] W.Florkowski, O.Madetko, Acta Phys. Polon. B45 (2014) 1103
[3] L.Tinti, W.Florkowski, Phys.Rev. C89 (2014) 034907
[4] W.Florkowski, E.M., R.Ryblewski, L.Tinti, Phys. Rev. C92 (2015) 054912
[5] W.Florkowski, E.M., R.Ryblewski, arXiv:1711.03872
[6] W.Florkowski, E.M., R.Ryblewski, arXiv:1710.07095

Speaker: Ewa Maksymiuk (Jan Kochanowski University)

307 Landau damping in a strong magnetic field: Dissociation of quarkonia

We have investigated the properties of quarkonia in a hot QCD medium in the presence of strong magnetic field, which may be produced in the non-central events at RHIC and LHC and then studied its quasi-free dissociation due to the Landau-damping mechanism. Using the Schwinger propagator in the lowest Landau level, we have calculated the real and imaginary parts of the retarded gluon self-energy in a strong magnetic field using the real-time formalism. The aforesaid self-energy computes the resummed retarded and symmetric propagators whose static limits embody the effects of the medium into the real and imaginary part of both short- and long-distance components of $Q \bar Q$ interaction in vacuum. In strong magnetic field, the large-distance interaction is affected more than the shot-distance interaction, as a result, the real part of potential becomes more attractive. On the other hand, due to the dimensional reduction, the magnitude of imaginary part becomes smaller compared to a thermal medium in absence of strong magnetic field. We have found that the average radii of the quarkonia get reduced and become more strongly bound in presence of the strong
magnetic field. However, further increase of the magnetic field results in the decrease of binding energies. In the presence of strong magnetic field, the decay width of the resonances becomes smaller and the dependence on magnetic field becomes less steep than the dependence on temperature. Having discussed the properties of quarkonia, we have estimated the magnetic field beyond which
the resonances go to the continuum due to Landau damping, where we found that $\psi^\prime$ and $\chi_c$ in a hot QCD medium are dissociated relatively at larger magnetic fields, $eB= 4~m_\pi^2$ and $5~m_\pi^2$, compared to the dissociation by the color screening mechanism only. However, the $J/\psi$ is dissociated at very large magnetic field.

Speaker: Ms Subhalaxmi Rath (Indian Institute of Technology Roorkee)

308 Large area triple GEM chambers for muon tracking at CBM experiment at FAIR

A Muon Chamber (MUCH) system comprising of alternating layers of segmented absorbers and detector triplets will perform the task of dimuon detection at CBM experiment at FAIR. Unprecedented interaction rates (~10 MHz) of Au+Au collisions and a high radiation environment in CBM impose severe constraints on the detector design. For the first two stations of MUCH where the particle rates reach more than 140 kHz/sq. cm. for minimum bias events, large area, Gas Electron Multiplier(GEM) based detectors with self-triggered readout will be used for muon tracking. Triple-GEM prototypes of both small and large sizes have been tested with particle beams. Design criteria such as a high charged particle detection efficiency, high-rate capability have been validated. Real-size trapezoidal shaped detectors (~2000 sq.cm area) have been fabricated and tested with Pb+Pb collisions at CERN SPS. Single-mask GEM foils consisting of 24 segments each, were stretched using “ns2” no-glue technique. Data was acquired in a free-streaming mode, using realistic CBM DAQ involving AFCK boards coupled to a self-triggered electronics and time synchronizing modules for the first time. Events were reconstructed offline by grouping the hits on the basis of their timestamps. Detailed response of the detectors in terms of time correlations, hit-multiplicity, their dependence on varying detector parameters have been studied and track reconstruction carried out. A cost-effective opto-coupler based, novel HV-biasing design for controlling individual segments will be presented. Low voltage distribution system(LVDS) with requisite radiation hardness have also been designed and tested. The detailed layout of the GEM stations, detector fabrication and the test results along with pre-production readiness plans for the upcoming mini-CBM experiment at GSI will be presented and discussed.

Speakers: Ajit Kumar (VECC, Kolkata), Anand Kumar Dubey

QM2018_CBMposter_ajit_v6_final.pdf

309 Light and heavy flavor jet quenching at RHIC and the LHC energies

The study of hard jets and their interactions with the traversed medium provides a very improtant tool to probe the quark-gluon plasma produced in relativistic heavy-ion collisions. In this work [1], we study both light and heavy flavor jet quenching on the same footing utilizing a Boltzmann transport model including both elastic and inelastic parton-medium interactions within perturbative QCD. The dynamical evolution of the QGP medium that hard jets probe is simulated with relativistic hydrodynamics that has been tuned to describe the soft hadron production at RHIC and the LHC. Our numerical results can simultaneously describe the experimental data on both light and heavy flavor hadron suppressions for different centralities at both RHIC and the LHC heavy-ion collisions. Detailed analysis show that the initial parton spectra, the details of the energy loss mechanism, and the shapes of fragmentation functions all play important role in understanding the difference between the nuclear modifications of light and heavy flavor hadrons. The temperature, flavor and energy dependences of the jet quenching parameter $\hat{q}$ are quantitatively extracted. We further study the correlations between light and heavy flavor hadrons.

[1] S. Cao, T. Luo, G.-Y. Qin, X.-N. Wang, arXiv:1703.00822, Phys.Lett. B, in press; arXiv:1605.06447, Phys.Rev. C94 (2016) no.1, 014909.

Speaker: Guang-You Qin (Central China Normal University)

QM_poster_v3.pdf

310 Linearly polarized gluons and axial charge fluctuations in the Glasma

We calculate energy deposition and axial charge production from color flux tubes at early times in a heavy-ion collision. Based on analytic expressions for the space-time dependent fluctuations of the axial charge and energy density distributions in terms of the unpolarized and linearly polarized gluon distributions of the nuclei, we develop a phenomenological model for the initial state, which can be used as an input to anomalous hydrodynamic simulations. Besides fluctuations of the axial charge density, we also calculate fluctuations of the energy density and discuss how our results can be used to consistently include fluctuations of the energy density on sub-nucleonic scale into simple initial state models, such as for example the MC-Glauber model.

Speaker: Soeren Schlichting (University of Washington)

QM_POSTER.pdf

311 LO and NLO Calculations of Heavy Flavour Electron Correlations in Small Systems

Heavy flavour quarks (charm and beauty) are of special interest for the study of the Quark-Gluon Plasma as they are predominantly produced in the initial hard-scattering processes and participate in the entire evolution of the system. Moreover, heavy flavour production is well under control of perturbative QCD. Thus, heavy flavours are an excellent probe to study pQCD in small systems as well as parton in medium energy loss and transport mechanisms in nuclear collisions by measuring, for instance, the spectra, angular correlations or the nuclear modification factor $R_{AA}$.
Experimentally, heavy flavours are often investigated using measurements of electrons from heavy-flavour hadron decays. These electrons can be separated statistically from the background and their angular correlations with other heavy flavour electrons or with charged particles can be studied.
In this poster, we present theoretical predictions for the spectrum and angular correlations of heavy flavour electrons in pp collisions at $\sqrt{s}=13$ TeV obtained at LO and NLO accuracy using PYTHIA and POWHEG, respectively. The correlations can be utilized to separate charm and beauty contributions and provide insights into different heavy-flavour production mechanisms. – Supported by DFG GRK2149.

Speaker: Florian Herrmann (Westfaelische Wilhelms-Universitaet Muenster (DE))

QMPoster.pdf

312 Low $p_{T}$ direct photon production from small to large systems

Direct photons are unique probes to study both the thermal and collective properties of the Quark Gluon Plasma (QGP). PHENIX has discovered a large excess of the direct photon yield as well as a large azimuthal anisotropy at the low $p_{T}$ region in Au+Au collisions at  $\sqrt{s_{NN}}=200$ GeV$/c^{2}$. The two observations of large yield and anisotropy are quite challenging for the current theoretical models to reconcile simultaneously. To provide more constrains and insights to the theoretical picture, PHENIX is making a more precise measurements for both yield and anisotropy using the high statistics data sample of Au+Au collisions taken in 2014, where photons are reconstructed via conversions to $e^{+}e^{-}$ pairs. As evidence mounts for a collective behavior in small systems, PHENIX also measured the direct photon production in p+Au collisions to see if there is any thermal signal in small systems. In this poster we will present the updated result on direct photon yields and azimuthal anisotropies $v_{2}$ and $v_{3}$ in Au+Au collisions at 200 GeV$/c^{2}$ and the status of direct photon yields in p+Au collisions at the same beam energy.

Speaker: Wenqing Fan (Stony Brook University)

QM2018_wenqing_v4.pdf

313 Low-mass Dielectrons in p-Pb collisions at sqrt(sNN) = 5.02 TeV with ALICE

A very promising probe to study the quark-gluon plasma, a deconfined state of
quarks and gluons predicted by lattice quantum chromodynamics calculations
in ultra-relativistic heavy-ion collisions, are correlated dielectron pairs.
Electrons reach the detector without significant final state
interactions. In addition, the low-mass dielectron spectrum comes from various
sources, i.e. Dalitz and resonance decays of pseudoscalar and vector mesons,
semi-leptonic decays of charm and beauty hadrons, as well dielectrons from the
thermalised system, which are produced at all stages of the collision.
Therefore, they can be used to study the space-time evolution of the system.

While pp collisions provide an important baseline measurement in vacuum for
heavy-ion studies, p-Pb collisions can be used to disentangle cold from hot
nuclear matter effects. Moreover, recent studies in small colliding systems
(pp and p-Pb) showed intriguing collective behaviours similar to observations previously
done in heavy-ion collisions. They require further investigations in
particular as a function of the event charged-particle multiplicity. Searching
for the thermal signatures through dielectrons is also important in small
systems to disentangle the initial state effects and final state effects.

In this poster the latest status of the dielectron analysis with ALICE in
p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV will be presented. Data recorded
in 2016 are used. Furthermore, it will be discussed how a multivariate approach
can be useful in the measurements of low-mass dielectrons.

Speaker: Aaron Capon (Stefan Meyer Institute for Subatomic Physics (SMI), Austrian Academy of Sciences (AT))

acapon.pdf

314 Low-mass dimuon measurements in pp and Pb-Pb collisions with ALICE at the LHC

Low-mass dimuon production, including light neutral mesons $\eta,~\rho,~\omega,~\phi$, provides key information on the hot and dense state of strongly interacting matter produced in ultra-relativistic heavy-ion collisions. The proper baseline for these observations is provided by the measurements of low-mass dimuons in pp collisions, which also allows for the tuning of light particle production models in the largely unexplored LHC energy regime.

ALICE studies low-mass dimuon production at the CERN LHC with the Muon Spectrometer covering the forward rapidity range $2.5 < y < 4$. Observations in Pb-Pb collisions at $\sqrt{s_\mathrm{NN}} = 2.76$ and $5.02$ TeV allowed for the characterisation of $\phi$-meson production in the $p_{\rm T}$ range $2 < p_{\rm T} < 5$ GeV/$c$ and $2 < p_{\rm T} < 7$ GeV/$c$, respectively, giving insight on strangeness production at forward rapidity. $\phi$-meson production has also been studied in pp collisions at $\sqrt{s} = 2.76$, $5.02$, $7$, $8$ and $13$ TeV, offering the unique possibility to test the energy dependence of the production cross section in the common $p_{\rm T}$ range $1.5 < p_{\rm T} < 5$ GeV/$c$. The large statistical sample available at $\sqrt{s} = 13$ TeV also allowed for a new, dedicated study of the $p_{\rm T}$-$y$ dependence of the production cross section of the low-mass mesons.

Speaker: Antonio Uras (Inst. Nat. Phys. Nucl et Particules (FR))

Poster_QM18_Uras_v6.pdf

315 Magnetohydrodynamics with chiral anomaly: phases of collective excitations and instabilities

We study the relativistic hydrodynamics with chiral anomaly and dynamical electromagnetic fields. This theory is called the chiral magnetohydrodynamics (MHD) [1]. It is a framework that can evolve the system of QGP fluids and electromagnetic fields consistently, and it will play an important role in quantifying anomaly-induced effects in heavy-ion collisions. We formulate the chiral MHD as a low-energy effective theory based on a derivative expansion. We demonstrate that the modification of ordinary MHD due to chiral anomaly can be obtained from the second law of thermodynamics and is tied to the chiral magnetic effect with the universal coefficient. When the chirality imbalance exceeds a critical value, a new type of collective gapless excitation emerges, as a result of the interplay among magnetic field, flow velocity, and chiral anomaly; we call it the chiral magnetohelical mode (CMHM). These modes carry definite magnetic and fluid helicities and either grow exponentially or dissipate in time, depending on the relative sign between their helicity and axial charge density. The presence of exponentially growing CMHM indicates a hydrodynamic instability.

[1] Koichi Hattori, Yuji Hirono, Ho-Ung Yee, Yi Yin, “Magnetohydrodynamics with chiral anomaly: phases of collective excitations and instabilities,”[arXiv:1711.08450 [hep-th]].

Speaker: Koichi Hattori (Fudan University)

QM_poster---qm18-2.pdf

316 Measurement of $\Lambda_\mathrm{c}$ production via $\Lambda_\mathrm{c}\rightarrow \mathrm{pK}\pi$ channel in p-Pb collisions at 5.02 TeV with ALICE

Heavy flavour quarks (charm and beauty) offer a unique opportunity to study the strongly-interacting medium, known as the Quark-Gluon Plasma (QGP), created in ultra-relativistic heavy-ion collisions. They are produced in the early stages of the collision, in hard scattering processes, allowing the heavy quarks to interact with the QGP throughout its entire evolution. The measurement of the $\Lambda_\mathrm{c}$ baryon and of the charmed mesons allows the baryon-to-meson ratio to be evaluated, probing hadronisation and thermalisation mechanisms in the medium. This measurement, made in p-Pb collisions, will also help to separate the hot and cold nuclear matter effects seen in Pb-Pb collisions.

The ALICE detector, with its excellent vertex reconstruction and hadron identification, allows for the study of $\Lambda_\mathrm{c}$ production. This poster presents the measurement of the $p_{\rm T}$-differential cross section of the $\Lambda_\mathrm{c}$ baryon through the $\Lambda_\mathrm{c}\rightarrow \mathrm{pK}\pi$ decay channel in p-Pb collisions at $\sqrt{\textit{s}_\mathrm{NN}}$ = 5.02 TeV. The use of multivariate methods to optimise topological cuts, for improved signal extraction, will also be discussed.

Speaker: Christopher Hills (University of Liverpool (GB))

QM18Poster_CH_final.pdf

317 Measurement of $D$ meson production and long-range azimuthal correlation in 8.16 TeV $p$+Pb collisions the ATLAS experiment

Measurements of production and azimuthal anisotropy of prompt charm mesons ($D^0$ and $D^*$) are presented using $p$+Pb data at $\sqrt{s_{NN}}=8.16$ TeV collected in 2016 by ATLAS. Prompt charmed meson production is measured in minimum bias $p$+Pb data, and is reconstructed via two decay channels: $D^0\rightarrow K+\pi$ and $D^*\rightarrow D^0+\pi\rightarrow K+\pi+\pi$. The measured charm meson production cross sections are comparable with FONLL predictions scaled by $A_\mathrm{Pb} = 208$ within uncertainties. The production asymmetry between forward and backward center-of-mass rapidities for the charm mesons is studied for the range of $|y^*| < 0.5$, and no significant asymmetry is observed. The anisotropy is studied using two-particle correlations, with a template fitting procedure used to subtract the residual jet contribution. Finite long-range correlations are observed for particle pairs containing $D^*$ mesons. The flow modulation of $D^*$ is broadly consistent with what has been observed for light hadrons and muons from heavy quark decays.

Speaker: Qipeng Hu (University of Colorado Boulder)

poster_QM2018_QHU.pdf

318 Measurement of $Z$ boson production in Pb+Pb and $pp$ collisions by the ATLAS experiment

A measurement of $Z$ boson production is performed via leptonic decay channels using data samples from the 2015 LHC run obtained at the center-of-mass energy of $\sqrt{s_{_{\rm{NN}}}} = 5.02$ TeV with a total integrated luminosity of 0.49 nb$^{-1}$ and 25.3 pb$^{-1}$ in Pb+Pb and $pp$, respectively. Integrated and differential cross sections are measured for both electron and muon channels in a fiducial detector acceptance defined by a lepton selection of $p_{\rm{T}}^{\ell}>20$ GeV and $|\eta^{\ell}|<2.47(2.5)$ for electrons (muons) with correction for FSR effects. The combined result for both decay channels is compared to NNLO pQCD predictions with different PDF sets calculated with DYNNLO. The large statistical sample of Pb+Pb collisions also allows a high-precision test of the Glauber model.

Speaker: Mirta Dumancic (Weizmann Institute of Science (IL))

ZPbPb_poster_QM2018_ver3.pdf

319 Measurement of (anti-)$^{3}\mathrm{He}$ production in p--Pb collisions and of (anti-)$^{3}\mathrm{He}$ elliptic flow in Pb--Pb collisions with ALICE at the LHC

The formation of light nuclei and their antiparticles in high-energy hadronic and heavy-ion collisions can be described by two phenomenological models: the statistical hadronization model and the coalescence approach. The former assumes that light nuclei, as well as other hadrons, are produced thermally at the phase boundary in heavy-ion collisions, while the latter describes the light nuclei formation as the result of coalescence of nucleons which are close in the phase space.
\newline \indent
In this poster, results on the production yields of (anti-)$^{3}\mathrm{He}$ in p--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV and elliptic flow measured in Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 and $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV for different centrality classes are presented.
\newline \indent
The attempt is to provide additional constraints to the coalescence model, thus contributing to an improved understanding of the process of formation of light nuclei in high-energy collisions. Integral part of this effort is the comparison of results in different collision systems such as p--Pb and Pb--Pb.
The measurement of the elliptic flow of (anti-)$^{3}\mathrm{He}$ in Pb--Pb collisions complements the picture obtained from the elliptic flow measurements of (anti-)protons and (anti-)deuterons.

Speaker: Dr Alberto Calivà (GSI)

qm18_Poster_AlbertoCaliva.pdf

320 Measurement of azimuthal correlations of D mesons with charged particles in pp collisions at sqrt{s}=7 TeV with ALICE at the LHC

The collisions of heavy ions at ultrarelativistic energies provide an excellent
way to study the phase transition from hadronic matter to a deconfined state
of quarks and gluons, the Quark-Gluon Plasma (QGP). The ALICE (A Large
Ion Collider Experiment) detector at the LHC is designed for the study of the
QGP properties. Heavy quarks (charm and beauty), having a large mass, are
produced in the initial stages of the collision in hard parton scatterings. Hence,
they experience the whole evolution of the hot and dense medium, representing
an important tool for its characterization.
The study of angular correlations between D mesons and charged particles
in different collision systems provides information about the possible medium-
induced modification of charm quark fragmentation into jets. In pp collisions,
this measurement allows the study of the production mechanisms, fragmentation
and hadronization of charm quarks. In addition, it acts as a reference for p-Pb
and Pb-Pb systems.
In this poster, the measurement of azimuthal correlations
between D mesons(D$^{0}$ , D$^{+}$ , D$^{∗+}$ ) and charged particles in pp collisions at $\sqrt{s}$ = 7 TeV will be
presented. The D mesons are reconstructed via their hadronic decay channels at
midrapidity ($|y| < 0.5$) in the transverse momentum range $3 \leq p_{T} \leq 16$ GeV/$c$
and correlated to charged particles with $p_{T }> 0.3$ GeV/$c$ with pseudorapidity
$|\eta| < 0.8$. The results are compared with expectations of simulations performed
with different event generators.

Speaker: Bharati Naik (IIT- Indian Institute of Technology (IN))

2018-apr-04-conference_presentation-qmposterfinal.pdf

321 Measurement of charged jet cross-section and properties in proton-proton collisions at 2.76 TeV with ALICE

Jet is the collection of concentrated final state hadrons produced from the fragmentation of hard scattered parton in high energy hadronic, leptonic or heavy-ion collision. In proton-proton (pp) collisions, measurement of jet production cross-sections and jet properties provide validation for perturbative Quantum Chromo Dynamics (pQCD) and gives detailed insight of parton to jet fragmentation. These measurements also stand as vacuum reference for similar measurements in heavy-ion collisions where the created hot and dense medium modifies the jet fragmentation.

We will report the measurements of charged jet production cross-sections and jet properties observables such as the charged particle multiplicity distribution inside leading jet, leading charged jet size and the radial momentum distribution in pp collisions at √s = 2.76 TeV with ALICE. The sequential recombination anti-kT algorithm is used for jet reconstruction taking only charged particles with pT ≥ 0.15 GeV/c into account. Jets are reconstructed for resolution parameter (R) 0.2, 0.4 and 0.6 in the range 5 GeV/c < pT < 70 GeV/c. Results will be compared to predictions from different Monte Carlo event generators.

Speaker: Rathijit Biswas (Bose Institute (IN))

QM2018_rbiswas_v4.pdf

322 Measurement of D meson azimuthal correlations with charged particles in p-Pb collisions at √ s = 5.02 TeV with ALICE

Heavy quarks (charm and beauty) are produced via hard parton scatterings in the initial stage of the collision. Thus, they are ideal probes of the Quark-Gluon Plasma (QGP) created in ultra-relativistic heavy-ion collisions at the LHC. Two-particle angular correlation studies in heavy-ion collisions have provided deep insight into the the in-medium partonic energy loss and its dependence on the parton path length in the medium. The extension of these studies to the heavy-flavour sector could shed light on the interaction of the heavy quarks with the medium.

Heavy-flavour correlation measurements in p-Pb collisions are necessary to disentangle final-state QGP-induced modifications from effects caused by cold nuclear matter. In p-Pb collisions, double-ridge long-range correlations have been observed for light particles. They could originate from a collective behaviour of the system, as well as from gluon saturation in the initial state, as addressed by the Color Glass Condensate theory. This feature can also be searched for heavy quarks. Angular correlation of D mesons with charged particles are also useful to probe the properties of charm jets and charm-production processes.

In this contribution, we will present ALICE results on D-meson azimuthal correlations with charged particles in p-Pb collisions at $ \sqrt{s_{\rm{NN}}}$ = 5.02 TeV collected during run 2 at the LHC. The measurement extends the $ p_{\rm T}$ coverage of the previous result obtained with run-1 data and improves significantly its precision. The results are compared with Monte Carlo simulation expectations obtained with PYTHIA and POWHEG event generators and with pp-collision results at $ \sqrt{s}$ = 7 TeV.

Speaker: Mr Shyam Kumar (IIT- Indian Institute of Technology (IN))

323 Measurement of D*+-meson production as a function of centrality in p–Pb collisions with ALICE

Heavy quarks (charm and beauty) are sensitive probes to study the properties of the Quark-Gluon Plasma (QGP), the hot and dense medium formed in high-energy heavy-ion collisions. Due to their large masses, heavy quarks are produced in hard partonic scattering processes in the initial stages of the collision. Their abundance is not expected to be modified through the evolution of the system. Therefore, they experience the whole evolution of the system interacting with the medium constituents.
In p–Pb collisions, the measurements of heavy-flavour production allow us to study cold nuclear matter effects, such as shadowing, $k_{\rm T}$ broadening and initial-state energy loss, as well as possible geometrical and collective effects in high-multiplicity events.

In this poster, the ALICE results on the $\rm D^{*+}$-meson production measurement in p–Pb collisions at $\sqrt{s_\rm{NN}}=5.02$ TeV will be presented, focusing on the centrality-dependent studies from LHC Run 2 data. The nuclear modification factor of the $\rm D^{*+}$ mesons, measured through the full reconstruction of the hadronic decay in $\rm{D}^{*+}\to\rm{D}^0\pi^+\to \rm{K}^-\pi^+\pi^+$, will be shown in different centrality classes and compared to charged particles. The central-to-peripheral ratio will also be presented and discussed.

Speaker: Cristina Bedda (Utrecht University (NL))

posterQM_Bedda.pdf

324 Measurement of D*+-meson production in small systems with ALICE at the LHC.

Heavy quarks (charm and beauty) are a valuable probe to study the properties of the Quark-Gluon Plasma created in Pb--Pb collisions. In order to distinguish the hot nuclear matter effects in Pb--Pb collisions from possible Cold Nuclear Matter effects (CNM), measurements in p--Pb collisions are crucial.
Possible CNM effects, such as $k_{\rm{T}}$-broadening, shadowing and parton energy loss in the cold nuclear matter, are studied via the comparison of the $\rm{D}^{*+}$ yield measured in p--Pb and pp collisions. This comparison is quantified by the nuclear modification factor $R_{\rm{pPb}}$.
Furthermore, studies of the $p_{\rm{T}}$-differential cross-section of $\rm{D}^{*+}$ mesons in pp collisions at the Large Hadron Collider (LHC) allow us to test next-to-leading-order perturbative QCD calculations at the TeV energy regime, while also providing a reference for p--Pb and Pb--Pb measurements.

The $\rm{D}^{*+}$ mesons measured with ALICE at the LHC are reconstructed at mid rapidity via the hadronic channel $\rm{D}^{*+}\to\rm{D}^0\pi^+\to \rm{K}^-\pi^+\pi^+$.
In this contribution, the $\rm{D}^{*+}$-meson production in pp collisions collected in Run I at $\sqrt{s}=8$ TeV will be presented, as well as the latest Run II results for the $\rm{D}^{*+}$-meson production in pp collisions at $\sqrt{s}=13$ TeV and p--Pb collisions at $\sqrt{s_{\rm{NN}}}=5.02$ TeV.

Speaker: Annelies Marianne Veen (Utrecht University (NL))

QMVeniceAMveen.pdf

325 Measurement of D+ -meson production in pp and p-Pb collisions with ALICE at the LHC

Heavy quarks (charm and beauty) are sensitive probes to study the properties of the Quark-Gluon Plasma (QGP) produced in high-energy heavy-ion collisions. Due to their large masses, charm and beauty quarks are produced in the initial stages of the collisions in hard-scattering processes and they explore the entire evolution of the system
The measurement of charm production in pp collisions is important to test perturbative Quantum Chromodynamics (QCD) calculations and provides an essential baseline for the studies in heavy-ion collisions. Charm production measurements in p--Pb collisions allow us to disentangle the influence on particle production of cold nuclear matter effects from those related to the formation of a QGP in Pb--Pb collisions.
In ALICE, charm production is studied through the reconstruction of D-meson hadronic decays at midrapidity. In this contribution, we will present the measurement of the production cross section of D^{+} -mesons in pp collisions at $\sqrt{s}$ = 5.02, 7, 8 and 13 TeV with the ALICE detector. The D^{+} meson nuclear modification factor measured in p--Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV will also be presented.

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

2018-may-09-conference_presentation-rbala_qm_2018_new_1.pdf

326 Measurement of Ds+/D+ as a function of transverse momentum and charged-particle multiplicity in pp, p-Pb and Pb-Pb collisions with ALICE

Heavy quarks (charm or beauty) are powerful probes to study and characterise the properties of the deconfined medium created in high-energy heavy-ion collisions, the Quark-Gluon Plasma (QGP). Because of their large masses, heavy quarks are produced in initial hard-scattering processes, and they subsequently experience the whole system evolution, interacting with the medium constituents. The observation of a large suppression of the heavy-flavour hadron yields at intermediate/high transverse momentum ($p_{\rm T}$) in central Pb-Pb collisions with respect to those in pp collisions provides a strong evidence of the in-medium parton energy loss. Moreover, the measurement of heavy-flavour hadrons with strange-quark content (i.e. ${\rm D^+_{s}}$ mesons) can give insight into the heavy-quark hadronisation mechanism. If a fraction of charm quarks hadronises via coalescence, the relative abundance of ${\rm D^+_{s}}$ with respect to non-strange D mesons is expected to be larger in heavy-ion collisions compared to pp collisions, due to the enhanced production of strange quarks in the QGP. Furthermore, an enhanced production of strange and multi-strange hadrons was recently observed in high-multiplicity pp and p-Pb collisions. For these reasons, the measurement of the production of ${\rm D^+_{s}}$ mesons compared to that of non-strange D mesons as a function of the charged-particle multiplicity (${\rm d}N_{\rm ch}/{\rm d}\eta$) is interesting to study a possible enhancement of particles with strange-quark content in pp and p-Pb collisions in the heavy-quark sector, similar to the one observed for light hadrons.

In this poster, the measurement of ${\rm D^+_{s}}/{\rm D^+}$ yield ratios as a function of $p_{\rm T}$ in pp collisions at $\sqrt{s}=7~{\rm TeV}$ and Pb-Pb collisions at $\sqrt{s_{\rm NN}}=5.02~{\rm TeV}$, and as a function of ${\rm d}N_{\rm ch}/{\rm d}\eta$ in p-Pb and Pb-Pb collisions at $\sqrt{s_{\rm NN}}=5.02~{\rm TeV}$, will be presented.

Speaker: Fabrizio Grosa (Politecnico di Torino (IT))

DsOverDplus_pp_pPb_PbPb_QM2018_Grosa_final.pdf

327 Measurement of isolated photons in p–Pb collisions at 5.02 TeV with the EMCal detector in ALICE

In high energy hadron collisions, direct photons can be produced at different stages and are of particular interest to study the hot QCD medium since they escape it without being affected.

At high transverse momentum ($p_{\text{T}}$), these photons may come from hard scattering processes (prompt photons) and from high $p_{\text{T}}$ parton fragmentation. Their measurement in proton-proton collisions allows to test pQCD and to put constraints on parton distribution functions. In proton-ion collisions (e.g., p–Pb), measuring direct photons enables to study cold nuclear effects and especially access nuclear parton distribution functions (nPDF). Their knowledge is crucial to understand the direct photon production in a context of hot nuclear matter where other mechanisms occur in addition.

One can access prompt photons experimentally with an isolation procedure. The isolated photon production in p–Pb collisions at $\sqrt{s_{\text{NN}}} = 5.02\,\text{TeV}$ measured with the ALICE ElectroMagnetic Calorimeter (EMCal) will be discussed in this poster.

Speaker: Erwann Masson (Subatech, IN2P3-CNRS (FR))

QM2018_Poster_ErwannMasson.pdf

328 Measurement of J/psi Polarization in p+p Collisions at √s = 200 GeV through the Di-muon Channel at STAR

Quarkonium production mechanism in elementary collisions has not been fully understood. Experimental data on the $J/\psi$ cross section in p+p collisions can be described relatively well by several models that are currently available on the market. However, these models differ in their predictions for the $J/\psi$ polarization. Therefore precise measurements of $J/\psi$ polarization can provide further constraints on the production models. During the RHIC 2015 run, the STAR experiment recorded a large sample of p+p collisions at $\sqrt{s}$ = 200 GeV triggered by the Muon Telescope Detector for charmonium studies via the di-muon decay channel. In this poster, we will present the $J/\psi$ polarization measurement in the helicity and Collins-Soper reference frames utilizing this data set. The polarization parameters $\lambda_{\theta}$ and $\lambda_{\phi}$ are extracted from simultaneous fit to 1-dimensional polar and azimuthal angular distributions of decay $\mu^{+}$ in the J/$\psi$ transverse momentum range of 0-6 GeV/c in both frames. The results will be compared with similar measurements in higher transverse momentum region as well as with model calculations.

Speaker: Zhen Liu (University of Science and Technology of China and Brookhaven National Laboratory)

QM18_ZhenLiu_v8.pdf

329 Measurement of Lambda_cbar-/Lambda_c+ Ratio in Au+Au Collisions at √sNN = 200 GeV with the STAR Experiment

The yield ratios of strange anti-baryons to baryons have been measured in heavy-ion collisions and exhibit a trend that is getting closer to unity with increasing number of valence strange quarks. This ratio has, however, never been measured for charm baryons, and it will be important to establish if they exhibit a similar amount of baryon-to-anti-baryon enhancement as strange baryons. $\Lambda_\mathrm{c}$ is the lightest baryon containing a charm quark and, as such, presents a unique probe to study the hadronization of charm quarks in the hot and dense QCD medium created in ultra-relativistic heavy-ion collisions. $\Lambda_\mathrm{c}$ has, however, an extremely short lifetime ($c \tau \sim 60\,\mu$m) which makes the reconstruction experimentally challenging. The Heavy Flavor Tracker, installed at the STAR experiment between the years 2014-2016, has shown a high efficiency and an unparalleled track-pointing resolution that facilitates the $\Lambda_\mathrm{c}$ reconstruction in heavy-ion collisions. In this poster, we will present the reconstruction of $\Lambda_\mathrm{c}$ baryons via hadronic decays and the measurement of the yield ratio of $\overline{\Lambda_\mathrm{c}}^-/\Lambda_\mathrm{c}^+$, utilizing the high-statistics data samples of Au+Au collisions at $\sqrt{s_\mathrm{NN}} = 200\,$GeV, recorded with the STAR experiment in 2014 and 2016.

Speaker: Miroslav Simko (Nuclear Physics Institute of the Czech Academy of Sciences (cz))

QM18posterLc_v14.pdf

330 Measurement of Lambdac/D0 ratio in Pb-Pb collisions at 5.02 TeV with ALICE

The ALICE detector at the Large Hadron Collider (LHC) has been optimised for the studies of the Quark-Gluon Plasma (QGP) created in heavy-ion collisions. Charm quarks are one of the probes that has been extensively used to elucidate the properties of the QGP. They are dominantly produced at the initial stage of the collisions and experience the whole evolution of the system.

While most of the charm-hadron measurements in heavy-ion collisions are currently limited to mesons, charm-baryon measurements could provide unique insights into hadronisation processes from the QGP. The baryon-to-meson ratio is expected to be enhanced if charm quarks hadronise via recombination with the surrounding light quarks in the QGP. Moreover, in such a recombination picture, the baryon-to-meson ratio could further be enhanced in the presence of diquark bound states in the QGP. Thus, the measurements of charm baryons could shed light on an unexplored aspect of the QGP.

The production of charm baryons has been studied in pp and p-Pb collisions with the ALICE detector. The measurement in Pb--Pb collisions also became possible with the significantly improved statistics of LHC Run-2 compared to LHC Run-1. In this poster, we will report on the first measurement of the $\Lambda_{\rm c}/{\rm D}^0$ ratio in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV.

Speaker: Yosuke Watanabe (University of Tsukuba (JP))

poster.pdf

331 Measurement of low transverse momentum electrons from heavy-flavour hadron decays in Pb-Pb collisions at 5 TeV with ALICE

Due to their high masses ($m_{\text{c}}\approx 1.5\text{ GeV}/c^2$, $m_{\text{b}}\approx 4.8\text{ GeV}/c^2$), charm and beauty quarks are mostly produced in the initial hard scattering processes, happening immediately after the lead nuclei collide. This process has typical time scales shorter than the Quark-Gluon Plasma formation time, therefore by studying the kinematic properties of heavy-flavour particles, the medium can be investigated. In particular, it is important to understand how these quarks lose energy by traversing the medium and to test shadowing, hadronization and flow mechanisms.

In this poster the status and progresses on the results concerning open heavy-flavour detection through semi-electronic decay channels in Pb-Pb collisions at the centre of mass energy per nucleon pair of $\sqrt{s_{\text{NN}}}=5.02\text{ TeV}$ registered by ALICE will be shown. Electrons are identified using the information provided by the central barrel detectors (Inner Tracking System, Time Projection Chamber, Time Of Flight). Most of the electrons come from background sources, such as photon conversions
in the detector material and Dalitz decays of light mesons,
which are tagged with an invariant mass technique.
After their subtraction, the $p_{\text{T}}$ spectrum of electrons from heavy-flavour hadron decays
in the transverse momentum region $0.5\text{ GeV}/c\leq p_{\text{T}}\leq 6\text{ GeV}/c$ can be obtained and the nuclear modification factor $R_{\text{AA}}$ can be computed.

Speaker: Mattia Faggin (Universita e INFN, Padova (IT))

Poster_QM2018_MattiaFaggin_final.pdf

332 Measurement of low-mass dielectrons in minimum-bias and high-multiplicity pp collisions at 13 TeV with ALICE

Electron-positron pairs are a unique experimental tool to investigate the hot and dense medium created in ultra-relativistic heavy-ion collisions. Such pairs are produced during all stages of the collision and do not interact strongly. Therefore, they carry information about the medium properties and the whole space-time evolution of the system.

Measurements of dielectron production in minimum-bias proton-proton collisions provide an important vacuum reference for any modifications observed in heavy-ion collisions. Moreover, the measurement of e$^{+}$e$^{-}$ pairs from semi-leptonic decays of correlated heavy-flavour hadrons in the intermediate-mass region (1.2 < mee < 2.9 GeV/$c^{2}$) allow further studies and understandings of the primordial heavy-flavour production. Finally, recent studies of proton-proton collisions with high charged-particle multiplicities showed interesting results similar to the observations previously done in heavy-ion collisions. Measurements of low-mass dielectrons could provide further insight into the underlying physics processes.

In this poster we present the latest results of the dielectron analysis with ALICE in pp collisions at $ \sqrt{s}=13 $ TeV. A particular focus of the discussion is put on the modification of dielectron spectrum in pp collisions collected with a trigger on high charged-particle multiplicities compared to the minimum-bias events.

Speaker: Ivan Vorobyev (Technische Universitaet Muenchen (DE))

QM18_poster_IV_lmee13TeV.pdf

333 Measurement of neutral K*(892) and phi(1020) production in p-Pb collisions at c.m energy 8.16 TeV with ALICE at the LHC

Hadronic resonances are interesting probes of the hot and dense matter created in heavy-ion collisions. Due to their short lifetime, resonances are useful tools to understand the mechanism of particle production and properties of the hadronic phase. If the time interval between the chemical and kinetic freeze-out (hadronic phase) is comparable with the lifetime of the resonance, the yield of resonances might be modified due to in-medium effects such as re-scattering and regeneration. In particular, studying resonance production in p-Pb collisions along with pp provides a baseline for measurements in Pb-Pb collisions and helps in understanding cold nuclear matter effects such as the Cronin enhancement at intermediate $p_{\mathrm{T}}$ and shadowing effects.
We report on the measurement of K$^{*}(892)^0$ and $\phi(1020)$ resonances, performed in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=8.16$ TeV in the rapidity range -0.5 < $y$ < 0. The results include the transverse momentum ($p_{\mathrm{T}}$) spectra, integrated yields and mean transverse momentum. The $p_{\mathrm{T}}$ spectra of K$^{*0}$ and $\phi$ have also been measured as a function of multiplicity up to $p_{\mathrm{T}}$ = 20 GeV/$c$ and 16 GeV/$c$, respectively. The results will be compared with p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV.

Speakers: Mr Sandeep Dudi (PU, Chandigarh, India), Dukhishyam Mallick (National Institute of Science Education and Research (IN))

Kstar_Phi_pPb8TeV_QM2018.pdf

334 Measurement of neutral meson spectra in proton-proton collisions at $\sqrt{s} = 5$ TeV with the ALICE EMCal detector.

Neutral meson production in proton-proton collisions is described by pQCD in a large kinematic range. Parameters of theoretical models in both perturbative (NLO, NNLO) and non-perturbative (structure function, fragmentation function) regimes are constrained by neutral pion and $\eta$ meson spectra. The ratio of $\eta$ to $\pi^0$ spectra tests $m_{\rm T}$ scaling violation in the low $p_{\rm T}$ regime. Neutral meson spectra in pp serve as a reference for p-Pb and Pb-Pb measurements at the same collision energy per nucleon pair. Additionally, decay photons coming from neutral mesons are a major source of background for direct photon measurements. There are several methods of neutral meson reconstruction used in the ALICE experiment. Photons are measured directly in the EMCal or PHOS calorimeter or are reconstructed via photon conversion method (PCM) from $e^+ e^-$ pairs coming from photons which converted in the detector. Neutral mesons are combined from photons measured only by one calorimeter, photons reconstructed in PCM or from hybrid methods. The final neutral meson production spectra are a combination of results with different methods. Here we present neutral meson spectra measurements via the invariant mass technique in pp collisions at $\sqrt{s}=5$ TeV with the ALICE electromagnetic calorimeter (EMCal).

Speaker: Adam Tomasz Matyja (University of Tennessee (US))

posterQM2018_AdamMatyja.pdf

335 Measurement of Neutral Mesons and Direct Photons in pp collisions with the ALICE EMCal detector at the LHC

ALICE has measured the invariant cross sections for the production of $\pi^{0}$ and $\eta$ mesons in proton-proton collisions at center of mass energies of $\sqrt{s}$ = 0.9 TeV, 2.76 TeV, 7 TeV and most recently 8 TeV.
Neutral mesons are reconstructed via their two photon decay channels by means of an invariant mass analysis.
Photons are detected with three different systems; using the central barrel tracking detectors of ALICE in order to reconstruct photon conversions (PCM) and the two available calorimeters in the experiment, namely the Photon Spectrometer (PHOS) and the Electromagnetic Calorimeter (EMCal).
The reported measurements are carried out as well using a 'hybrid' system which reconstructs meson candidates by combining one EMCal photon with one PCM photon.
Thus, this 'hybrid' system serves as an important cross-check for the single measurements and additionally measures an almost independent set of meson candidates.
The EMCal is a sampling calorimeter with good acceptance and high reconstruction efficiency, enabling measurements of $\pi^{0}$ and $\eta$ mesons up to highest transverse momenta due to its excellent triggering capabilities.
In addition to these results on neutral meson production, the corresponding $\eta/\pi^0$-ratios will be shown to test scaling laws for particle production.
All obtained results will be compared with different Monte Carlo generators as well as recent NLO pQCD predictions.

Based on the obtained results, inclusive direct photon measurements are being carried out, for which the most recent status will be presented.
A novel method using the 'hybrid' PCM-EMCal system is followed in addition to tag $\pi^{0}$ candidates and extract the direct photon signal, which will be shortly illustrated.

Speaker: Daniel Michael Muhlheim (Westfaelische Wilhelms-Universitaet Muenster (DE))

Poster_DanielMuehlheim.pdf

336 Measurement of neutral mesons in pp collisions at sqrt{s} = 5 TeV via photon conversions in ALICE

Measurements of neutral meson spectra in pp collisions provide a good opportunity to test pQCD calculations at high ${p}_{T}$.
The ratio $\eta$ to $\pi^0$ allows to study phenomenological principles like $\rm{m}_{T}$ scaling at low ${p}_{T}$. Furthermore, $\pi^0$ and $\eta$ spectra in pp collisions provide a reference to understand the mechanisms appearing in p-Pb and Pb-Pb collisions at the same collision energy. The spectra are also important for the description of the decay photon background in direct photon measurements.
In ALICE, we measure $\pi^0$ and $\eta$ mesons by using PHOS and EMCal calorimeters as well as the photon conversion method (PCM).
These different methods make it possible to measure neutral mesons in a very wide $p_{T}$ range.
In the PCM, neutral mesons are measured by detecting decay photons converted in electron-positron pairs which are reconstructed in the ALICE central barrel detectors, the Inner Tracking System and the Time Projection Chamber. In this poster, the results of neutral meson spectra obtained with PCM will be presented.

Speaker: Hikari Murakami (University of Tokyo (JP))

qm18_murakami_v4_submission.pdf

337 Measurement of the pT-differential cross section and fragmentation function of D0-tagged jets in pp collisions with ALICE

The production of heavy quarks in proton-proton (pp) is described in the framework of perturbative Quantum Chromo-Dynamics (pQCD) via the leading order process ${\rm gg\, (q\bar{q})} \rightarrow {\rm Q\bar{Q}}$. Among higher-order processes, gluon splitting ${\rm gg\, (q\bar{q})} \rightarrow {\rm gg} \rightarrow \rm gc\bar{c}$ is known to account for a large fraction of the charm produced at the LHC. Charmed hadrons coming from the fragmentation of charm quarks produced in the leading order process are expected to carry a larger fraction of the total jet momentum, as compared to those coming from gluon splitting. Therefore the measurement of the charm jet fragmentation functions (FFs) can be used to improve our understanding of the charm production mechanisms.

Heavy-flavor jets can also provide important insights into the Quark-Gluon Plasma (QGP) produced in ultra-relativistic heavy-ion collisions, as heavy quarks are predicted to interact with the QGP constituents differently compared to light quarks and gluons. Measuring charm jets gives a better estimate of the initial parton energy when compared to single-hadron measurements, which allows a more precise test of heavy-quark transport models of the QGP in the low momentum region, where the effect of the quark mass is expected to be more prominent.

We present the measurement of the production of charm jets tagged with fully reconstructed D$^0$ mesons in minimum bias pp collisions at $\sqrt{s} = 7$ TeV with the ALICE detector. The production of charm jets is investigated both in the $p_{\rm T}$-differential cross section and in the distribution of the jet momentum fraction ($z$) carried by the D$^0$ meson. D$^0$-meson candidates are identified in their hadronic decay channel D$^0\rightarrow$K$^{-}\pi^{+}$ and combined with the other tracks reconstructed in the central barrel using the anti-$k_{\rm T}$ jet-finding algorithm.

Speaker: Salvatore Aiola (Yale University (US))

SAiola_ALICE_D0jets_pp_v5.pdf

338 Measurement of the Sixth-order Cumulant of Net-charge Distributions in Au+Au Collisions at √sNN = 200 GeV by the STAR Experiment

In heavy-ion collision experiments, the study of event-by-event fluctuations is a powerful tool to characterize the thermodynamic properties of the hot and dense QCD matter. According to the Lattice QCD calculations, an analytic cross-over exists at small $\mu_{B}$ regions but there is no experimental evidence for the location of predicted cross-over. Experimentally, it is thought that up to the sixth-order cumulant and the ratio to the variance may be the signal of the cross-over. The STAR experiment presented up to the fourth-order cumulant ratios of net-charge and up to the sixth-order of net-proton fluctuations at $\sqrt{s_{NN}}=200$ GeV. However, the fifth and sixth-order cumulant of net-charge have not been presented yet. This poster presents measurements of cumulants from the first- to sixth-order and the ratio to the variance of net-charge using particle species and $p_{T}$ dependent efficiency corrections for Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV during Beam Energy Scan in 2010 and 2011.

Speaker: Tetsuro Sugiura (University of Tsukuba, Japan)

tsugiura_QM18poster_v2.pdf

339 Measurement of the substructure of jets in $pp$ and Pb+Pb collisions using ATLAS Run 2 data

The substructure of inclusive jets in lead-lead and proton-proton collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV is reported using the ATLAS Run 2 data at the LHC. Jet substructure observables have been recently developed to access the internal structure of jets produced in proton-proton collisions. These observables are sensitive to the angular and momentum correlations of the jet fragments, and are thus useful in characterizing the modification of jets in heavy ion collisions providing complementary information to single particle fragmentation functions. In this analysis, jets are reconstructed in kinematic range of $p_{\mathrm{T}}>150$ GeV and $|\eta|<1.2$ in Pb+Pb and $pp$ collisions. The current status of this measurement is presented and discussed in the context of other jet measurements in Pb+Pb collisions.

Speaker: Yongsun Kim (Univ. Illinois at Urbana Champaign (US))

340 Measurement of the Underlying Event in pp collisions at√s = 13 TeV with the ALICE experiment at the LHC

Large In LHC RUN 2, the Large Hadron Collider restarted with a centre-of-mass energy increase of around 60% with respect to the end of the LHC RUN 1, in which the highest energy of pp collision is 7 TeV. At this new energy, 13 TeV in pp collision, it is absolutely essential to restudy the general features of the pp interaction, in particular the soft or semi-hard bulk of particles that form the Underlying Event, which is defined to be the complementary activity with respect to the leading interaction.

Measurement of the Underlying Event allows us to access fundamental information on the particle production. This has important consequences for lepton and photon isolation, and also for jet calibration.

In order to estimate the contributions to the Underlying Event, we present a characterization of the event properties focusing on the orthogonal plane with respect to the beam direction: the primary charged particle with the highest transverse momentum is used to give the energy scale of the interaction, Underlying Event activity is measured as a function of this energy scale. Primary charged particle and energy densities are measured in different azimuthal regions with respect to the leading charged particle. Three track $p_{T}$ cuts are considered for all the tracks: 1, 0.5 and 0.15 GeV/c.

In this poster, the first results on Underlying Event measurement in pp collisions at $\sqrt{s}$ = 13 TeV with the ALICE experiment will be presented.

Speaker: Mr Xiaowen Ren (Central China Normal University CCNU (CN))

QM2018_poster_UE_ALICE.pdf

341 Measurement of the underlying event in the presence of high pileup at ATLAS

In meaurements of bulk charged-particle production, the kinematic characteristics of produced hadrons and correlation between them in the presence of the hard scattering signatures is a very interesting topic for understanding the physics processes relevant in small collision systems. Extensive data samples have been accumulated by the LHC experiments experiments to conduct these studies in $pp$ collisions. These measurements, however, are complicated by the presence of many pileup vertices in each bunch crossing which contaminate direct studies of the characteristics of the underlying event. This problem is addressed in the ATLAS detector using an event mixing technique which allows to correct for the presence of the pileup on a statistical basis. The implementation, result and limitations of the techniques are presented in this poster. The results use $\sqrt{s} = 8$ and 13 TeV data samples with a combined integrated luminosity exceeding 50 fb$^{-1}$.

Speaker: Alexander Milov (Weizmann Institute of Science (IL))

Z-h_poster_v0.pdf

342 Measurements of $\gamma\gamma\rightarrow \mu^{+}\mu^{-}$ with the ATLAS detector at the LHC

In heavy ion collisions, the intense electromagentic fields result in a high rate of photon-photon collisions. The cross section for the process $\gamma\gamma\rightarrow \mu^{+}\mu^{-}$ involves the equivalent photon fluxes from the nuclei and elementary cross sections calculated in QED. These fluxes also arise in the calculation of exclusive vector meson production and ultra-peripheral jet photo-production, which may be used to constrain nuclear parton distributions. Thus measurements of $\gamma\gamma\rightarrow \mu^{+}\mu^{-}$ provide an important tool to calibrate the photon fluxes. This talk presents such measurements performed with the ATLAS detector. This includes new results correlating the dimuon system with neutron multiplicity measured with Zero Degree Calorimeters. A careful analysis of the acoplanarity distributions is also presented that includes the effects of final-state QED radiation and contributions from dissociative and background processes. The new results are sufficiently-precise to constrain and tune theoretical models.

Speaker: Aaron Angerami (Lawrence Livermore National Laboratory)

343 Measurements of D$^0$ meson production in pp collisions with ALICE at the LHC

Heavy quarks (charm and beauty) are powerful probes to investigate the properties of the Quark-Gluon Plasma (QGP), the hot and dense medium produced in ultra-relativistic heavy-ion collisions. Heavy quarks are produced in hard-scattering processes on a time scale shorter than the QGP formation time; therefore, they experience the whole evolution of the produced system of strongly-interacting matter.

The study of the production of hadrons containing heavy quarks in proton-proton (pp) collisions at LHC energies represents a very important test of perturbative Quantum Chromodynamics (pQCD). Furthermore, measurements in pp collisions provide also the essential baseline for heavy-ion analyses.

In this contribution, we present the production cross section of prompt charmed D$^{0}$ mesons, measured with the ALICE detector at the LHC in pp collisions at $\sqrt{s}$ = 8 and 13 TeV. The D$^{0}$ mesons are reconstructed at mid-rapidity via their hadronic decay channel $\mathrm D^0 \to \mathrm K^-\pi^+$.
Moreover, the $p_{\text{T}}$-differential cross sections will be compared with the results at $\sqrt{s}$ = 7 TeV and with pQCD calculations.

Speakers: Susanna Costanza (Universita e INFN, Pavia (IT)), Nicolo' Valle (Universita and INFN (IT))

D0production_pp_v8.pdf

344 Measurements of D0 Production in p+Au and d+Au Collisions at √sNN = 200 GeV by the STAR Experiment

Charm quarks possess large masses, and thus can serve as penetrating probes to study the intrinsic properties of the hot medium created in heavy-ion collisions. However, Cold Nuclear Matter (CNM) effects, such as the change in the parton distribution function between a free nucleon and a nucleus, also affect the charm quark production in nuclear collisions with respect to p+p collisions. These effects can be measured in small systems such as p+A and d+A collisions, where only the CNM effects are present. Furthermore, a sizable azimuthal anisotropy ($v_2$) has been observed in both nucleus-nucleus collisions and small-system collisions of high multiplicities. To better understand the origin of the flow-like signal in small-system collisions, it is important to study charm quark azimuthal anisotropy in these systems.

In this presentation, we will report on the first measurements of $\text{D}^{0}$ production in p+Au collisions, and the $\text{D}^{0}$ transverse momentum spectrum and $v_2$ with the Heavy Flavor Tracker in d+Au collisions, all at $\sqrt{s_{\text{NN}}}=200$ GeV. The nuclear modification factors of $\text{D}^{0}$ meson will be extracted to quantify the CNM effects, and a comparison will be made to those of electrons from open heavy flavor hadron decays in p+Au collisions. Different cuts on the pseudo-rapidity gap between $\text{D}^{0}$ candidates and tracks used for event plane reconstruction, as well as different techniques, such as event plane and two-particle correlation methods, will be explored to help understand different physics mechanisms contributing to the azimuthal anisotropy.

Speaker: Lukas Kramarik (Czech Technical University (CZ))

QM18poster_kramarik.pdf

345 Measurements of heavy-flavour production and study of heavy-flavour jets via electrons in heavy-ion collisions with ALICE

In relativistic heavy-ion collisions, heavy quarks (charm and beauty) are ideal probes to investigate the properties of the hot and dense colour-deconfined QCD matter, so called Quark-Gluon-Plasma (QGP). Heavy quarks are produced in initial hard partonic interactions, and they propagate through the QGP.A strong suppression of heavy-flavour hadron production has been observed in the most central heavy-ion collisions with respect to the expectation from binary-scaled pp collisions at intermediate and high $p_{\rm{T}}$. This is ascribed to energy loss of heavy flavours via radiative and collisional processes in the dense matter. In addition, the positive $v_{2}$ (elliptic flow) observed at low $p_{\rm{T}}$ in semi-central heavy-ion collisions suggests that heavy quarks participate to the collective motion of the system. These results indicate strong interaction of heavy quarks in the medium. Further information of the interaction of heavy quarks in the QGP is obtained by measuring their production in different collisions energies. Measuring heavy-flavour jets allows for a more direct access to the initial parton kinematics and therefore provides an additional information on the energy loss and hadronisation of heavy quarks in the medium. The study of jets allows also to address the spatial distribution and kinematic properties of the radiative energy.

In this poster, recent ALICE measurements of the $R_{\rm{AA}}$ of electrons from heavy-flavour hadron decays in Pb--Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 5.02 TeV is shown. The result is compared with the $R_{\rm{AA}}$ measured at $\sqrt{s_{\rm{NN}}}$ = 2.76 TeV for discussing the energy dependence of the suppression and with theoretical predictions. In addition, we will present studies of heavy-flavour jets tagged with electrons from heavy-flavour hadron decays in p--Pb collisions, as an outlook for further study of QGP with heavy quarks.

Speaker: Shingo Sakai (University of Tsukuba (JP))

poster_HFE_Ssakai.pdf

346 Measurements of Open Bottom Hadron Production via Displaced J/psi, D0 and Electrons in Au+Au Collisions at √sNN = 200 GeV at STAR

Recent RHIC and LHC results show that the nuclear modification factors of open charm hadrons at high transverse momenta as well as their elliptic flow are similar to those of light flavor hadrons, indicating that charm quarks also interact very strongly with the Quark Gluon Plasma (QGP). During interactions, charm quarks suffer from substantial energy loss and gain significant elliptic flow. It is then imperative to measure bottom production in heavy-ion collisions to study the mass dependence of parton-medium interactions in the QGP suggested by QCD.

In this talk, we will report on STAR measurements of open bottom hadron production through their displaced decay daughters ($B \rightarrow J/\Psi,~D^{0},~e$) in Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 200 GeV. These measurements are made possible with the high-precision vertexing and tracking provided by the Heavy Flavor Tracker. With a factor of 2-5 times more data recorded in year 2016, signal precisions of these measurements are greatly improved compared to previous preliminary results. For Non-prompt $D^0$, further improvement is obtained from a successful implementation of a supervised machine learning method in offline reconstruction. Centrality dependence of nuclear modification factors for non-prompt $D^0$ and electrons from bottom hadron decays will be presented. These new results will be compared to those of open charm hadrons at RHIC and those of open charm and bottom hadrons at the LHC as well as to theoretical calculations. Physics implications will be discussed.

Speaker: Mr Xiaolong Chen (USTC / LBNL)

QM18_xlchen_v7.pdf

347 Measurements of the Upsilon Meson Production in Au+Au Collisions at √sNN = 200 GeV by the STAR Experiment

In ultra-relativistic heavy-ion collisions, creation of a novel state of matter, the quark-gluon plasma (QGP), has been observed. This hot, dense, and short-lived medium of deconfined quarks and gluons is experimentally very challenging to study. Suppressed production of heavy quarkonia, caused by colour screening of the binding force, has been viewed as a direct evidence of the QGP formation. Moreover, different quarkonium states are expected to dissociate at different temperatures, which can be used to constrain the properties of the medium.

In this poster, we will present recent measurements of the $\Upsilon$ production in Au+Au collisions at $\sqrt{s_\mathrm{NN}}=200$ GeV via the di-lepton channel by the STAR experiment at RHIC. At RHIC energies, other phenomena influencing the quarkonium production, such as the regeneration and co-mover absorption, are expected to have little or no effect for the bottomonium family, which makes it a cleaner probe compared to the $J/\psi$ meson. We will show the nuclear modification factors for both the ground and excited $\Upsilon$ states. Furthermore, we will compare these with results from p+Au collisions at RHIC, which provide a quantification of the cold nuclear matter effects, and also with measurements from Pb+Pb collisions at the LHC as well as with theoretical calculations.

Speaker: Oliver Matonoha (Czech Technical University in Prague)

QM18poster_matonoha_v10.pdf

348 Medium response to jet energy loss and redistribution of lost energy via the AMPT model

Jet-medium interaction has two important aspects: jet energy loss and the medium response to the lost energy/momentum. The study of jet energy loss has been very successful in the explanation of the suppression of high $p_T$ hadron and jet productions as well as the nuclear modification of dihadron, dijet, photo-jet and hadron-jet correlations. The search for the signal of the medium response to jet transport has been a long-standing topic: how does the lost energy from the jets evolve with the dynamical medium and where does it show up in the final state particle distributions and correlations?

We study the medium response and redistribution of the lost energy from hard jets via the AMPT model. In particular, we study asymmetric dijet events in PbPb collisions at 2.76 TeV. We first investigate in detail the contribution from the final charged hadrons carrying different transverse momenta and emitted from different angular directions, the projected transverse momentum $\langle p_{T}^{||} \rangle$ [1]. It is found that $\langle p_{T}^{||} \rangle $ in the leading jet direction is mainly contributed by hard hadrons in both peripheral and central PbPb collisions, while the opposite direction in central collisions is dominated by soft hadrons. Our study of the in-cone and out-of-cone contributions to $\langle p_{T}^{||} \rangle$ shows that these soft hadrons are mostly emitted at large angles away from the dijet axis. These results indicate that in the AMPT model, a large amount of the lost energy from hard jets occurred in the partonic stage is transported by elastic collisions to soft partons at large angles; this is qualitatively consistent with the CMS measurements. To further investigate the signals of the medium response effect and the redistribution of the lost energy at large angles, we also study the jet shape functions with a wide range of $r$ for asymmetric dijet events.

[1] Z. Gao, A. Luo, G. L. Ma, G.Y. Qin, H.Z. Zhang, arXiv:1612.02548 [hep-ph].

Speaker: Mr Ao Luo (Central China Normal University)

QM_poster_luoao.pdf

349 Medium-energy Nuclear Physics with sPHENIX

A potential upgrade with forward instrumentation of the proposed sPHENIX detector at the Relativistic Heavy Ion Collider (RHIC), together with RHIC’s unique capabilities to collide polarized protons and heavy nuclei, will open the door to exciting new measurements to enhance our understanding of quantum chromodynamics (QCD). These measurements will reveal more about how partons behave in a nuclear environment, explore spin-spin and spin-momentum correlations in the nucleon in a new kinematic regime, and investigate high-temperature QCD systems over a range of baryon densities. In addition, they will probe early times in the formation of the strongly coupled quark-gluon plasma. This poster focuses on the measurements enabled by the sPHENIX forward upgrade, as well as the medium-energy nuclear physics program for the sPHENIX mid-rapidity detector itself.

Speaker: Joseph Osborn (University of Michigan)

ColdQCD_sPHENIX_QM18_poster_Joe_Osborn.pdf

350 Metric anisotropies and emergent anisotropic hydrodynamics

Expansion of a locally equilibrated fluid is considered in an anisotropic space-time given by Bianchi type I metric. Starting from an isotropic equilibrium phase-space distribution function in the local rest frame, we obtain expressions for thermodynamic quantities such as number density, energy density and pressure components. In the case of an axis-symmetric Bianchi type I metric, we show that they are identical to that obtained within the setup of anisotropic hydrodynamics. We further consider the case when Bianchi type I metric is a vacuum solution of Einstein equation: the Kasner metric. For axis-symmetric Kasner metric, we discuss the implications of our results in the context of anisotropic hydrodynamics.

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

poster.pdf

351 Modeling QCD phase diagram within chiral relativistic mean field model fitted to $\mu_B=0$ lattice data

The SU(3) flavor parity-doublet quark-hadron model is used to investigate the phase diagram of QCD matter. The quark sector of the model is tuned to the $\mu_B=0$ lattice QCD data on trace anomaly. The structure of the baryon number susceptibilities in the temperature/chemical potential plane is studied in some detail.
The model predicts three phase transitions - nuclear first-order liquid-gas phase transition, chiral symmetry restoration, and deconfinement transition.
At $\mu_B=0$, good agreement with the corresponding lattice data is obtained.
The deviations from the free hadron gas baseline in the crossover temperature region at $\mu_B=0$ are mainly attributed to the leftover of the liquid-gas transition in nuclear matter, the chiral phase transition determines the baryon fluctuations at much higher $\mu_B$, and at even higher baryon densities the behavior of fluctuations is controlled by deconfinement transition.

[1] J. Steinheimer, S. Schramm and H. Stoecker, J.Phys. G38, 035001 (2011)
doi:10.1088/0954-3899/38/3/035001 [arXiv:1009.5239 [hep-ph]].
[2] J. Steinheimer, S. Schramm and H. Stoecker, Phys. Rev. C 84, 045208 (2011)
doi:10.1103/PhysRevC.84.045208 [arXiv:1108.2596 [hep-ph]].
[3] A. Mukherjee, J. Steinheimer and S. Schramm, Phys. Rev. C 96, no. 2, 025205 (2017)
doi:10.1103/PhysRevC.96.025205 [arXiv:1611.10144 [nucl-th]].
[4] V. Vovchenko, L. Jiang, M. I. Gorenstein and H. Stoecker, arXiv:1711.07260 [nucl-th].

Speaker: Mr Anton Motornenko (Frankfurt Institute for Advanced Studies)

QM2018_Motornenko.pdf

352 Moliere scattering in QGP: finding scatterers within the liquid

By looking for rare (but not exponentially rare) large-angle deflections of a jet or of partons within a jet, experimentalists can find the weakly coupled short-distance quark and gluon quasiparticles (scatterers) within the strongly coupled liquid quark-gluon plasma produced in heavy ion collisions, as was proposed in Ref. [1]. In this previous work, the probability for picking up a given transverse momentum via a Moliere scattering was calculated, but in the limit of infinite parton energy which means zero angle scattering. Here we calculate the Moliere scattering probability for incident partons with finite energy, meaning that we have now calculated the probability for a parton showing up with a nonzero angle with respect to its initial direction due to scattering with the constituents of QGP, using leading order perturbative QCD.

[1] Francesco D’Eramo, Mindaugas Lekaveckas, Hong Liu, and Krishna Rajagopal, JHEP 1305 (2013) 031 .

Speaker: Dr Yi Yin (MIT)

353 Momentum and energy dependence of J/Psi Suppression in Relativistic Heavy Ion Collisions

With a view to understanding and analyzing the recent available data on momentum- and energy dependence of J/Psi suppression, We compute suppression rate within a hydrodynamical model. For this, we consider an ellipsoidal flow and use an ansatz for temperature profile function which accounts for time and three dimensional space evolution of the quark-gluon plasma. A satisfactory agreement with the recent available data on J/Psi suppression is found and the result is also compared with other theoretical calculations.

Speaker: Prof. Santosh Kumar Karn (PCCS, Greater Noida, NCR-Delhi, Dr APJ Abdul Kalam Technical University, India)

354 Momentum anisotropy at freeze out

The transition from a hydrodynamical modeling to a particle-based approach is a crucial element of the description of heavy-ion collisions at high energies. Assuming this "freeze out" happens instantaneously at each point of the expanding medium, we show that the local phase-space distribution of the emitted particles is asymmetric in momentum space. This suggests the relevance of anisotropic hydrodynamics for the last stages of the fluid evolution. We further discuss how finite-state observables depend on the amount of momentum-space anisotropy at freeze out and how smaller or larger anisotropies allow for different values of the freeze-out temperature.

Speaker: Steffen Feld (Universität Bielefeld)

Poster.pdf

355 Multi-differential analysis with KF Particle Finder in the CBM experiment

The CBM experiment at FAIR is being designed for the study of the QCD phase diagram in the region of high baryon chemical potential at relatively moderate temperatures, where a complex structure is predicted by modern theories. The physics program of CBM is based, among others, on the precision measurements of a wide set of observables that contains extremely rare decays like, for example, charmed particles, dileptons, multi-strange particles and their antiparticles.

Such particles can be reconstructed and investigated only through their decay products. The KF Particle finder package was developed for solving the task of their reconstruction and selection. The package searches for more than 100 decay channels covering signals from most of the physics cases of the CBM experiment: strange particles, strange resonances, hypernuclei, low mass vector mesons, charmonium, and open-charm particles. Based on the Kalman filter mathematics, KF Particle Finder allows to estimate not only the parameters, but their errors as well.

The large multiplicity of the charged particles produced in heavy ion collisions leads to the combinatorial background in the reconstructed spectra of short-lived particles. The KF Particle Finder provides the machinery to describe the background and extract the signal spectra. Collecting the efficiency plots, the package contains tools for efficiency correction of the obtained spectra and their multi-differential analysis. Results obtained for strange particles are discussed. The rich functionality of KF Particle Finder makes it a universal platform for physics analysis.

Speaker: Maksym Zyzak (GSI)

Zyzak_QM2018.pdf

356 Multi-differential study of J/Psi RAA in forward rapidity in Pb-Pb collisions at sqrt(sNN) = 5.02 TeV with ALICE

At high temperature, Lattice Quantum Chromodynamics (LQCD) predicts the existence of dense and hot nuclear matter which behaves as a deconfined medium of quarks and gluons. Inside such medium, quarkonia are suppressed due to the color-screeening effect. However, at LHC energies an enhancement in the production of $J/\psi$ has been observed. This enhancement effect is more prominent at lower dimuon transverse momentum ($p_{T}$ $<$ 4 GeV/c) and central Pb-Pb collisions.

In the present study, the $J/\psi$ production as measured by ALICE in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV, in the forward rapidity region (2.5 $<$ y $<$ 4.0), is discussed. The $J/\psi$ nuclear modification factor $R_{AA}$ has been measured as a function of rapidity in different $p_{T}$ bins (0 - 2 GeV/c, 2 - 4 GeV/c, 4 - 6 GeV/c and $>$ 6 GeV/c) and centrality bins (0 - 20 $\%$, 20 - 40 $\%$ and $>$ 40 $\%$). The study of the $R_{AA}$ as a function of rapidity and transverse momentum may provide a deeper insight on the mechanism of $J/\psi$ regeneration and suppression.

New ALICE results on the $J/\psi$ nuclear modification factor measured as a function of rapidity, in $p_{T}$ and centrality classes, in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV will be presented.

Speaker: Hushnud Hushnud (Saha Institute of Nuclear Physics)

2018-may-09-conference_presentation-poster_v6.pdf

357 Multi-particle azimuthal correlations with subevent cumulants method in p+Pb collisions in a multiphase transport model

Recent observations of long-range correlations in small systems, such as p+p or p+A, challenge our understanding of the collectivity in the strongly coupling syetems. It has been shown that a multiphase transport (AMPT) model can naturally reproduce the long-range two-particle correlation in p+Pb collisions and in a good agreement with the experimental data [1]. A new subevent cumulant method is recently developed, which can significantly reduce the non-flow effects in long-range correlations for small systems [2]. In this study, we use subevent cumulant method to study multi-particle correlations in p+Pb collisions within the AMPT model. The 2nd and 4th order of multi-particle cumulants and multi-particle azimuthal correlations between different flow harmonics, SC(2,3) and SC(2,4), are numerically calculated. Our results show that $v_{2}\{2\}$ is consistent with the experimental data, while $v_{2}\{4\}$ is systematically smaller than the experimental data, which may indicate the collectivity is underestimated by the AMPT model. The SC(2,3) from the traditional cumulant method is negative at high multiplicity, while it is positive at low multiplicity. However, the SC(2,3) from the subevent cumulant methods is negative for all range of multiplicity. The SC(2,4) from the traditional cumulant method is larger than that from subevent cumulant methods. We will discuss the implication of these results, which help us to understand the origin of collectivity in small systems [3].

[1] A. Bzdak and G.-L. Ma, Phys. Rev. Lett. 113, 252301 (2014).

[2] J. Jia, M. Zhou, and A. Trzupek, Phys. Rev. C 96, 034906 (2017).

[3] M.-W. Nie and G.-L. Ma, in preparation.

Speaker: Maowu Nie (Shanghai Institute of Applied Physics (SINAP))

358 Multiparticle femtoscopy with marginal distributions

The usage of multiparticle correlation techniques for the study of genuine three-body and even higher-order interactions between hyperons and nucleons, which are relevant for instance for the description of equation of state of a neutron star, is plagued by difficulties in estimating consistently the background contribution to all terms (which are in general of different order) in the corresponding multiparticle cumulant expansion. In two-particle femtoscopy the background can be estimated with the mixed-event technique, but this approach appears to be impossible to reconcile with the standard cumulant formalism for the case of more than two particles.

We demonstrate how the mixed-event technique can be replaced with marginal distributions, which unifies multiparticle femtoscopy with the standard cumulant formalism. We discuss in detail whether the resulting new formalism satisfies the standard physical requirements (frame-independence, invariance to projection onto a single relative momentum variable, etc.).

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

ab_QM_0c.pdf

359 Multiplicity dependence of azimuthal correlations of D mesons with charged particles in p-Pb collisions with ALICE

Ultra-relativistic heavy-ion collisions allow the investigation of the Quark-Gluon Plasma (QGP), a colour-deconfined state of strongly-interacting matter produced in such collisions. Heavy quarks (charm and beauty) are important probes to understand the properties of this QCD medium, since they are produced in the early stages of the collisions and thus experience the whole evolution of the QGP.
The analysis of angular correlations between heavy-flavour particles and charged particles in pp collisions allows us to characterize the heavy-quark parton shower and gives us sensitivity to their production mechanisms. Differences between the measurements in pp and p-Pb collisions can give insight on how cold nuclear matter effects affect the heavy-quark production and the fragmentation into heavy-flavour jets. This is important for the interpretation of possible medium-induced modifications to the correlation pattern in Pb-Pb collisions. In the analysis of hadron-hadron correlations in high multiplicity p-Pb collisions, a double-ridge long-range structure has been observed, possibly coming from either a collective behavior of the system, or gluon saturation in the initial state. This feature can be investigated for heavy quarks as well through heavy-flavour correlation studies.
In this contribution, we will present ALICE measurements of azimuthal correlations between prompt D mesons and charged hadrons in p-Pb collisions at $\sqrt{s_\mathrm{NN}}$ = 5.02 TeV. A particular focus will be given on the ongoing studies to address possible modifications of the jet-induced correlation peaks at different event multiplicities.

Speaker: Marianna Mazzilli (Universita e INFN, Bari (IT))

MMazzilli_QM2018.pdf

360 Multiplicity dependence of strangeness production in proton-proton collisions at $\sqrt{s}$ = 5.02 TeV with ALICE at the LHC

Recent measurements performed in high-multiplicity proton-proton and proton-lead collisions at the LHC have shown features that are reminiscent of those observed in lead-lead collisions. Results on (multi-)strange hadron production in proton-proton collisions at $\sqrt{s}$= 5.02 TeV will be shown, based on the analysis of a data sample collected in 2015 with the ALICE detector. This sample is complemented by a large sample of minimum bias triggered events collected at the end of 2017. The first results on (multi)strange production in this collision system constitute an important reference for measurements in lead-lead collisions at the same energy.

Speaker: Mr Lukas Tropp (Pavol Jozef Safarik University)

QM2018poster_finalVersion.pdf

361 Multiplicity dependence study of the pseudorapidity density distribution of charged particles in pp collisions with ALICE

In this contribution, we report on the multiplicity dependence of the pseudorapidity density distribution of charged particles in proton-proton (pp) collisions at $\sqrt{s} =$ 5, 7 and at 13 TeV with the ALICE experiment.

The measurements rely on track segments reconstructed with the Silicon Pixel Detector in the kinematic region $|\eta| < 1.8$. Results are presented for three different event classes: inelastic (INEL), inelastic events with at least one charged particle in the central region $|\eta| < 1$ (INEL > 0), and non-single-diffractive (NSD) events for pp collisions at $\sqrt{s} =$ 5.02 TeV. The measurements are shown for different multiplicity slices, defined by a forward multiplicity estimator and a central multiplicity estimator, which manifest different physics. To better understand the role of collective effects that have been recently observed in pp collisions, the evolution of the shapes of the pseudorapidity density distributions at very high multiplicities is presented for pp collisions at $\sqrt{s} =$ 13 TeV using data collected with high-multiplicity triggers.

The results are compared to the predictions from the QCD-inspired Monte Carlo (MC) event generators PYTHIA and DIPSY as well as to expectations from the hydrodynamically treated MC event generator EPOS LHC.

Speaker: Prabhakar Palni (Central China Normal University CCNU (CN))

MM_QM_v4.4b.pdf

362 Multiplicity dependent production of heavy-flavour decay electrons in p-Pb collisions with ALICE

Heavy quarks (charm and beauty), produced in the initial stages of hadronic collisions in hard scattering processes, provide an important testing ground for perturbative QCD calculations. Measurements of their production as a function of the charged-particle multiplicity in pp and p-Pb collisions have recently gained interest for investigating the interplay between hard and soft mechanisms of particle production. In the p-Pb collision system, the formation and the kinematic properties of heavy-flavour hadrons can be influenced at all stages by Cold Nuclear Matter (CNM) effects and by concurrent Multiple Parton Interactions (MPI).
In recent studies, a faster than linear increase of the self-normalised yield of electrons from heavy-flavour hadrons as a function of charged-particle multiplicity up to 8 GeV/$c$ has been observed in p-Pb collisions at $\sqrt{s_{\rm{NN}}} = $ 5.02 TeV. Such trend can arise from the interplay between MPI and multiple binary nucleon-nucleon collisions. To further explore the non linear rise, we extend these measurements to higher $p_{\rm{T}}$ where the contribution of electrons from beauty-hadron decays is expected to dominate.
In this contribution, we will present the measurement of the self-normalised yield of electrons from heavy-flavour hadron decay as a function of the self-normalised charged-particle multiplicity estimated at mid-rapidity $|{\eta}|<1$ in p-Pb collisions at $\sqrt{s_{\rm{NN}}} = $ 8.16 TeV.

Speaker: Ms Preeti Dhankher (IIT- Indian Institute of Technology (IN))

QMPoster_HFEpPbSelfNormalise_PreetiDhankher.pdf

363 Multivariate background suppression in the low-mass dielectron analysis in Pb-Pb collisions at sqrt(sNN)= 5.02 TeV with ALICE

The measurement of e$^{+}$e$^{-}$ pair production in ultra-relativistic heavy-ion collisions offers a way to investigate the temperature of the quark-gluon plasma created in such systems and to study the effect of the hot medium and the predicted restoration of chiral symmetry. The dominant background in ALICE originates from tracks produced via photon conversions in the detector material. Numerous observables allow for discrimination of this background which motivates a multivariate approach in the classification of dielectron pairs.

In this poster, the latest results of the low-mass dielectron analysis obtained with a machine learning method in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$=5.02 TeV are presented. A robust classifier is obtained via domain adversarial training of neural networks on simulation data and real data. It will be shown how this novel training technique reduces the impact of mis-modeled features in the simulation data and therefore the systematic uncertainty of the classification.

Speaker: Sebastian Lehner (Austrian Academy of Sciences (AT))

QM18_slehner.pdf

364 New Jet-quenching model for Heavy Ion Monte Carlo Generators

The Gyulassy-Lévay-Vitev jet quenching [1] has been implemented for Monte Carlo particle event generators, especially for the HIJING$^{++}$[2]. With this new extension, one is able to perform calculations taking into account the geometry and opacity of the colliding nuclei.

We analyzed the old and recent heavy ion data from RHIC to LHC in comparison of the opacity parameter values extracted in Ref [3]. We made predictions for the upcoming Xe+Xe collisions at $\sqrt{s}=5.44$ TeV energy in the HIJING$^{++}$ and kTpQCD_v20 frameworks.

References:
[1] M. Gyulassy, P. Lévai, I. Vitev, Phys.Lett. B538 (2002) 282-288
and Nucl.Phys. B594 (2001) 371-419
[2] G.G. Barnaföldi et al. Nucl.Part.Phys.Proc. 289-290 (2017) 373
[3] J. Albacete et al, Int.J.Mod.Phys. E22 (2013) 1330007
[4] G.G. Barnaföldi et al Eur.Phys.J. C49 (2007) 333-338

Speaker: Gábor Papp (Eötvös University)

HijQuench.pdf

365 New perturbative solutions for relativistic hydrodynamics and the effect of longitudinal acceleration on spectra

In this work, we aim to investigate analytical solutions which take into account the longitudinal acceleration effect of fluid dynamics for nucleus-nucleus collisions. Starting from the equations for dissipative fluid dynamics, a new perturbative analytical solution for $1+d$ dimensional accelerating relativistic viscous hydrodynamics is presented.
From this accelerating hydrodynamic theory, the solution not only contains the general first-order viscous construct, but also includes a longitudinal acceleration parameter. The results show that, with the longitudinally accelerating hydrodynamic expansion, the temperature gradient becomes larger due to the acceleration effect, meanwhile the viscous corrections will decelerate the longitudinal hydrodynamic expansion and make the cooling rate smaller. Numerical results on the transverse momentum spectra, rapidity spectra and pseudo-rapidity spectra in the final state, are given for different values of the acceleration parameter, shear (bulk) viscosity to entropy density ratio $\eta/s$ ($\zeta/s$), and speed of sound $c_{s}$.

Speaker: Mr Zefang Jiang (CCNU)

CKCJ solution

Initial energy density calculation paper

JiangZF-QM2018-poster.pdf

366 News from the Micro Vertex Detector of CBM

The Compressed Baryonic Matter Experiment (CBM) is one of the core experiments
of the future FAIR facility. It will explore the phase diagram of strongly
interacting matter in the region of high net-baryon densities with numerous
probes including open charm. The Micro Vertex Detector (MVD) will enable
secondary vertex reconstruction with a resolution along the beam axis of 10 – 20
µm, enhance background rejection in dielectron spectroscopy and extend the
capability in the reconstruction of weak decays to channels with a neutral
particle in the final state. The detector comprises up to four stations placed
next to the target in vacuum. The stations are populated with 50~μm thin,
highly-granular customized Monolithic Active Pixel Sensors. A new version called
MIMOSIS, featuring a spatial resolution of <5 μm, a readout speed in the order
of 5 μs as well as radiation tolerance of >10^13 neq/cm² and 3 Mrad is currently
developed at IPHC in Strasbourg.

This contribution will include an update of
the MVD project status and present first physics performance studies using the
new MIMOSIS sensors geometry and performance parameters.

Speaker: Philipp Sitzmann

QM2018_CBMposter_Sitzmann_final.pdf

367 Next generation jet measurements with sPHENIX

The proposed sPHENIX detector at RHIC will allow state-of-the-art measurements of jets and jet correlations, making using of recent technological and conceptual advances. The kinematic reach of these measurements will overlap with those made at the LHC by taking advantage of the increased luminosity due to accelerator upgrades and the sPHENIX acceptance and rate capability. Particle jets, formed when a hard scattered parton fragments and then hadronizes into a spray of particles, were proposed as a probe of the Quark Gluon Plasma (QGP) formed in heavy-ion collisions. As these partons traverse the QGP, they lose energy to the medium, an effect called "jet quenching". To answer fundamental questions about parton energy loss and the microscopic nature of the QGP, we need to characterize both the medium induced modification of the jet fragmentation pattern and the correlation of the lost energy with the jet axis. Observables centered around gamma-jet correlations are especially useful as the photon kinematics are more tightly correlated with the hard scattered parton. In addition, there are other observables such as jet fragmentation functions and jet shape measurements, which require the precise tracking and calorimetry that sPHENIX will provide. We will show the performance of jet and gamma-jet observables with the improved simulation framework developed for understanding the performance of the new detector.

Speaker: Songkyo Lee (Iowa State University (US))

180515_songkyo_QM2018_v3.pdf

368 Nonequilibrium viscous correction and bulk viscosity in the relaxation time approximation

We present the correct form of the nonequilibrium viscous correction to the phase space density in the relaxation time approximation that properly takes into account the space-time dependence of the thermal mass. We also investigate the impact the correction has on the bulk viscosity. This correction automatically satisfies the Landau matching condition and energy-momentum conservation. It also makes the appearance of the Callan-Symanzyk $\beta_\lambda$-function natural in the bulk viscosity calculation. The bulk viscosity has the expected parametric form for the Boltzmann gas, while for the Bose-Einstein case, it is affected by the cut-off of infrared divergences. This may be an indication that the relaxation time approximation is too crude to obtain the correct form of the bulk viscosity for quantum gases.

Speaker: Alina Czajka (McGill University)

poster-new-Venice.pdf

369 Novel lattice simulations for transport coefficients in quenched QCD

Transport coefficients, such as the temperature-dependent shear and bulk viscosities, are essential QCD ingredients in the hydrodynamical description of relativistic heavy-ion collisions. While the equation of state by now is known with high precision from lattice simulations, the extraction of the transport coefficients from Euclidean simulations is extremely challenging. In particular, the corresponding Kubo formula requires the evaluation of a spectral function at vanishing momentum, and hence a reliable spectral reconstruction from Euclidean data at low frequencies. In standard lattice simulation at finite temperature this reconstruction is based on the discrete Matsubara frequencies, and is -in practice- exponentially hard: the thermal part of the low frequency information is hidden in the thermal decay of the Euclidean data at large frequencies.

In order to overcome this limitation, we apply the novel approach for thermal fields on the lattice [1] to gauge fields [2]. The formalism operates in a non-compact imaginary time domain that leads to continuous imaginary time frequencies. The quantum evolution is formulated as an initial value problem and the thermal initial conditions are supplied by a standard lattice simulation.

We present results for the energy momentum tensor in SU(2) Yang-Mills theory and SU(3) quenched QCD, which show excellent convergence to the standard results at finite Matsubara frequencies. From the correlation functions, we extract the relevant spectral functions using the Bayesian BR method [3] and determine the shear and bulk viscosity over entropy ratios. The imaginary time data in the present novel approach are precise enough to allow for a conclusive discussion of transport peaks in the spectral functions. Results are presented for the confined and deconfined phase.

[1] J.M. Pawlowski, A. Rothkopf, arXiv:1610.09531
[2] J.M. Pawlowski, A. Rothkopf and F. Ziegler (in progress)
[3] Y.Burnier, A.Rothkopf, PRL 111, 182003 (2013)

Speaker: Felix Ziegler (Heidelberg University)

QM2018-Poster-Ziegler.pdf

370 Nuclear modification factor in the monte-carlo model with burning-out partons

The so-called wounded-quark model (WQM) of particle production in heavy-ion collisions extends the monte-carlo Glauber approach to sub-nucleonic degrees of freedom. In the current work, a monte-carlo model, which is conceptually similar to the WQM, is presented. The main difference from the WQM is that each parton from the projectile nucleus can interact with only one parton inside the target (burning-out partons). As a result of each binary partonic interaction, a particle-emitting source is formed (usually modeled as a quark-gluon string), and this pair of partons does not participate in other partonic collisions anymore. It is shown that in this model it is possible to reproduce in a natural way the behaviour of some basic observables like the centrality dependence of charged particle multiplicity and nuclear modification factor, as well as several kinds of fluctuation observables in A-A and p-A collisions. Bayesian approach is used to estimate main parameters of the model, namely, number and distribution of partons inside nucleons and partonic cross sections.

Speaker: Igor Altsybeev (St Petersburg State University (RU))

poster_IgorAltsybeev_QM2018_v2.pdf

371 Nuclear modification factors of strange and multi-strange particles in pPb collisions with the CMS experiment

Identified particle spectra provide an important tool for understanding the particle production mechanism and the dynamical evolution of the medium created in relativistic heavy ion collisions. Studies involving strange and multi-strange hadrons, such as $K^0_S$, $\Lambda$, $\Xi^-$, and $\Omega^-$, carry additional information since there is no net strangeness content in the initial colliding system. Strangeness enhancement in AA collisions with respect to pp and pA collisions has long been considered as one of the signatures for quark-gluon plasma (QGP) formation. The Recent observation of collective effects in high-multiplicity pp and pA collisions raise the question of whether QGP can also be formed in the smaller systems. Systematic studies of the strange particle abundance and nuclear modification factors can shed light on this issue. The CMS experiment has excellent strange-particle reconstruction capabilities over a broad kinematic range in pp and pPb collisions. The spectra of $K^0_S$, $\Lambda$, $\Xi^-$, and $\Omega^-$ hadrons have been measured in various rapidity regions as a function of $p_T$ in pp and pPb collisions at 5.02 TeV. Based on the measurements of these spectra, nuclear modification factors of $K^0_S$, $\Lambda$, $\Xi^-$, and $\Omega^-$ in mid-rapidity are measured. Since pPb is an asymmetric system, the nuclear modification factor of $K^0_S$, $\Lambda$, and $\Xi^-$ in Pb-going direction are compared to those in p-going direction. These final results for nuclear modification factors measured out to high-$p_T$ can be helpful in discussing the implications of collective behavior and energy loss. In addition, the measurement of the forward-backward rapidity yield asymmetries of $K^0_S$ and $\Lambda$ as a function of $p_T$ provide sensitivity to initial state effects, such as shadowing in the nuclear parton distributions. Detailed comparisons with theoretical models will be presented.

Speaker: Julia Velkovska (Vanderbilt University (US))

372 Observation of the top quark in proton-nucleus collisions with the CMS experiment at the LHC

The first observation of top quark production in proton-nucleus collisions is reported using proton-lead data collected by the CMS experiment at the CERN LHC at a nucleon-nucleon center-of-mass energy of $\sqrt{s_\text{NN}}$ = 8.16 TeV. The measurement is performed using events with exactly one isolated electron or muon candidate and at least four jets. The data sample corresponds to an integrated luminosity of 174 nb$^-1$ .The significance of the $t\bar{t}$ signal against the background-only hypothesis is above five standard deviations. The measured cross section is $\sigma($t\bar{t}$) = 45 \pm 8$ nb, consistent with predictions from perturbative quantum chromodynamics.

Speaker: Mr Georgios Krintiras (Universite Catholique de Louvain (UCL) (BE))

QM_Poster_GKKrintiras.pdf

373 Off-diagonal Cumulants of Net-charge, Net-proton, and Net-kaon Multiplicity Distributions in Au+Au collisions at STAR

Event-by-event fluctuations of conserved quantities have been extensively used to study the thermodynamic properties around phase transition region of QCD matter. According to lattice QCD calculation, the off-diagonal cumulants of net-charge ($Q$), net-baryon ($B$) and net-strangeness ($S$) and their ratios to diagonal cumulants are sensitive to the evolution of the system and to constrain the freeze-out parameters in the QCD phase diagram [1,2].

In this poster, we report a first measurement of $2^{nd}$-order off-diagonal cumulants of net-charge, net-proton and net-kaon multiplicity distributions at RHIC in Au+Au collisions at $\sqrt{s_{NN}} =$ 7.7, 11.5, 14.5, 19.6, 27, 39, 62.4 and 200 GeV. We study beam energy, centrality, and acceptance ($\eta$) window dependence of off-diagonal cumulants after implementing efficiency and other experimental corrections. The measured cumulants ratios are compared with the predictions from UrQMD and hadron resonance gas models. The results will be discussed in the context of understanding the correlated fluctuations of the conserved quantities.

References
[1] A. Majumder and B. Muller, Phys. Rev. C74, 054901 (2006).
[2] F. Karsch and K. Redlich, Phys. Lett. B695, 136 (2011).

Speaker: Mr Arghya Chatterjee (Variable Energy Cyclotron Centre)

QM18_poster_arghya-v1.pdf

374 On the differences among Initial Conditions and their role in the distribution of particles

There are several theoretical models for initial conditions, which intend to describe the matter created in ultrarelativistic heavy-ion collisions. In this work, we will perform hydrodynamics computations using different initial conditions, as Wood-Saxon, Glauber, Mckln, Nexus and Gubser [1], and calculate several observables, as for instance, anisotropic flows $v_n$ [2], eccentricities $\varepsilon_n$, symmetric cumulants $SC(n,m)$ [3], event-plane correlations, and others quantities, in order to understand the hydrodynamics response to different initials geometry in heavy-ion collisions.

[1] Different references, but you can see "The Fate of the Initial State Fluctuations in Heavy Ion Collisions. II The Fluctuations and Sounds". Pilar Staig, Edward Shuryak.Phys.Rev. C84 (2011) 034908
[2] "Anisotropic flow in event-by-event ideal hydrodynamic simulations of 200 GeV Au+Au collisions." Fernando G. Gardim, Frederique Grassi, Matthew Luzum, Jean-Yves Ollitrault. Phys.Rev.Lett. 109 (2012) 202302
[3] "Hydrodynamic Predictions for Mixed Harmonic Correlations in 200 GeV Au+Au Collisions" Fernando G. Gardim, Frederique Grassi, Matthew Luzum, Jacquelyn Noronha-Hostler. Phys.Rev. C95 (2017) no.3, 034901

"This work is in progress, and will be finished up to march 2018.

Speaker: Dr Fernando Gardim (Federal University of Alfenas)

375 On the origin of the late-side tail in the time-of-flight distribution: A long-standing puzzle solved

Dedicated Time-of-Flight detectors are used for particle identification in ALICE, HADES, PHENIX, and STAR. New TOF detectors for Belle II, BESIII, LHCb, MPD, Panda, and SoLID are in various stages of development and implementation. Heavy ion detector experiments using TOF observe an anomalous early-late asymmetry in the time of flight distribution for particles of a given narrow momentum interval and mass hypothesis. A number of competing explanations have been sought, most of which focus on the pronounced late-side tail in the TOF signal. Some examples include: influence of feeddown descendants, energy losses from multiple scattering, biases from inner-to-outer detector track matching, and biases innate to TOF detector technology. Herein we examine each of these and derive from first principles the ideal TOF distribution and momentum dependent early-late asymmetry. We further conclusively explain its mysterious absence in test beam trial data. This new understanding will refine the standard fit-to-data calibration technique critical for high precision TOF detectors. Furthermore, it will improve the momentum range over which particle separation is possible, the estimates of systematic uncertainties, and detector simulations.

Speaker: Brennan Schaefer (Oak Ridge National Laboratory - (US))

A0_TOFmath_QM2018_BSchaefer.pdf

376 On the spin correlations of final leptons generated in the processes of annihilation of $(e^+ e^-)$ pairs, formed in relativistic heavy-ion collisions, and in the high-energy two-photon processes $\gamma \gamma \rightarrow e^+ e^-, \mu^+ \mu^-, \tau^+ \tau^-$

The electromagnetic processes of annihilation of $(e^+ e^-)$ pairs, produced
in high-energy nucleus-nucleus collisions, into heavy lepton pairs are
theoretically studied in the one-photon approximation, using the technique of
helicity amplitudes . For the process $e^+e^- \rightarrow \mu^+\mu^-$, it is
shown that -- in the case of the unpolarized electron and positron -- the final
muons are also unpolarized but their spins are strongly correlated. For the
final $(\mu^+ \mu^-)$ system, the structure of triplet states is analyzed and
explicit expressions for the components of the spin density matrix and
correlation tensor are derived. It is demonstrated that here the spin correlations
of muons have the purely quantum character, since one of the Bell-type
incoherence inequalities for the correlation tensor components is always violated.
In doing so, it is established that the qualitative character of the muon spin
correlations does not change when involving the additional contribution of the
weak interaction of lepton neutral currents through the virtual $Z^0$ boson.

On the other hand, the theoretical investigation of spin structure for the two-photon
process $\gamma \gamma \rightarrow e^+e^-$ ( where the photon pairs, in
particular, may be emitted in relativistic heavy-ion and hadron-nucleus collisions )
is performed as well. Here -- quite similarly to the process
$e^+e^- \rightarrow \mu^+\mu^-$ -- in the case of unpolarized photons the final
electron and positron remain unpolarized, but their spins prove to be strongly
correlated. Explicit expressions for the components of the correlation tensor
and for the relative fractions of singlet and triplet states of the final $(e^+ e^-)$
system are derived. Again, one of the Bell-type incoherence inequalities for the
correlation tensor components is always violated and, thus, spin correlations of
the electron and positron have the strongly pronounced quantum character.

Analogous considerations can be wholly applied as well, respectively, to the
annihilation process $e^+ e^- \rightarrow \tau^+ \tau^-$ and to the two-photon
processes $\gamma \gamma \rightarrow \mu^+ \mu^-$, $\gamma \gamma \rightarrow \tau^+ \tau^-$, which become possible at considerably higher energies.

Speaker: Dr Valery Lyuboshitz (Joint Institute for Nuclear Research, Dubna )

Quark_Matter_2018_Venice--Valery_Lyuboshitz.pdf

377 Open bottom hadron physics program at sPHENIX

Recent data from RHIC and LHC show that $R_{AA}$ and $v_{2}$ of charm hadrons are very similar to that of light and strange hadrons. At the same time, the $R_{AA}$ of bottom decay daughters at low $p_{T}$ seems to be less suppressed compared to light and charm hadrons, suggesting a mass suppression hierarchy. Precision open bottom measurements over a broad momentum range are needed for detail understanding of parton energy loss mechanisms and to characterize the transport properties of the strongly-coupled QGP medium.

sPHENIX is a planned next generation high-rate jet, Upsilon and open heavy-flavor detector at RHIC. A fast MAPS-based silicon vertex detector (MVTX) is proposed to greatly enhance the heavy flavor detection capabilities of sPHENIX. In this poster, we will present physics simulation studies on the open bottom measurements within the full sPHENIX tracking environment including the MVTX detector. Open bottom reconstruction has been explored via the inclusive non-prompt $D^0$ daughters and the full exclusive reconstruction of $B^+\rightarrow \bar{D}^0+\pi^+$. Statistical projections for nuclear modification factor and elliptic flow measurements will be presented.

Speaker: Xin Dong (Lawrence Berkeley National Lab)

378 Parameterization of deformed nuclei for Glauber modeling in relativistic heavy-ion collisions

The density distributions of large nuclei are typically modeled with a Woods-Saxon distribution characterized by a radius $R_{0}$ and skin depth $a$. Deformation parameters $\beta$ are then introduced to describe non-spherical nuclei using an expansion in spherical harmonics $R_{0}(1+\beta_2Y^0_2+\beta_4Y^0_4)$. But when a nucleus is non-spherical, the $R_{0}$ and $a$ inferred from electron scattering experiments that integrate over all nuclear orientations cannot be used directly as the parameters in the Woods-Saxon distribution. In addition, the $\beta_2$ values typically derived from the reduced electric quadrupole transition probability B(E2)$\uparrow$ are not directly related to the ones used in the spherical harmonic expansion.

In this talk, I present a method to calculate the $R_0$, $a$, and $\beta_2$ values that when used in a Woods-Saxon distribution, will give results consistent with electron scattering data, and then tabulate such parameters for nuclear species recently used in relativistic heavy-ion collisions, including U, Xe, Ru and Zr. The calculations of the second and third harmonic participant eccentricity ($\varepsilon$) with the new and old parameters are also presented and compared. It is demonstrated that $\varepsilon$ is sensitive to $a$, therefore, using the incorrect parameters has important implications for the extraction of viscosity to entropy ratio ($\eta/s$) from the QGP.

Speaker: Qi-Ye Shou (Shanghai Institute of Applied Physics)

379 Particle identification (PID) as a tool for the study of event-by-event fluctuations in MPD

The study of event-by-event fluctuations requires excellent particle identification (PID) over as large as possible phase space volume. Identification of charged hadrons is achieved at momenta 0.1 − 3 GeV/c. Results of hadron identification and preliminary possibility estimation of the study of event-by-event fluctuations in MPD are presented for the current PID phase space coverage |η| ≤ 1.6.

Speaker: Alexander Mudrokh (JINR (Russia))

PID_as_a_tool_for_EvE_study_MPD.pdf

380 Particle production mechanisms studied via angular correlations of pions, kaons, protons, and lambdas in pp collisions at 7 TeV with ALICE

Two-particle correlations as a function of pseudorapidity difference, $\Delta\eta$, and azimuthal angle difference, $\Delta\varphi$, are used to study a wide range of physical phenomena and provide access to the underlying physics mechanisms of particle production in collisions of both protons and heavy ions. Examples include the collective behaviour of the QGP medium, jets, quantum statistics or Coulomb effects, conservation laws, and resonance decays.

In this contribution, we report measurements of the correlations of identified particles and their antiparticles ($\pi$, K, p, $\Lambda$) in pp collisions at $\sqrt{s}$ = 7 TeV for momenta up to 2.5 GeV/$c$. The analysis reveals significant differences in particle production between mesons and baryons. The correlation functions for mesons exhibit the expected peak dominated by effects of mini-jet fragmentation and are well reproduced by general purpose Monte Carlo generators. This is not the case for baryon pairs; results for baryons present a challenge to the contemporary models (PYTHIA, PHOJET) with simulations showing significant differences in respect to experimental data. Moreover, when both particles have the same baryon number (pp, $\bar{p}\bar{p}$, p$\Lambda$, $\bar{p}\bar{\Lambda}$, $\Lambda\Lambda$, $\bar{\Lambda}\bar{\Lambda}$) a near-side anti-correlation structure is observed instead of a peak. This unexpected observation is further interpreted in the context of baryon production mechanisms in the fragmentation process.

Speaker: Malgorzata Anna Janik (Warsaw University of Technology (PL))

particle-production-mechanisms-printed.pdf

381 Pathlength dependence of particle-yield modification on the near-side with ALICE at the LHC

Ultra-relativistic heavy-ion collisions at the LHC produce a hot and dense medium, which is a deconfined state of quarks and gluons. Jets are produced from hard processes in the initial stages of the collision and interact with the medium while propagating through it. Angular correlation analyses of hadron pairs are a convenient method to observe jets and their interaction with the medium without fully reconstructing the jets.
Comparing the jet peak yield in pp collisions and Pb-Pb collisions gives information about the hard parton's energy loss mechanism through the medium. The jet energy loss while propagating through the medium can be quantified in azimuthal di-hadron correlations with the observable $I_{AA}$, the ratio between the jet peak yield in Pb-Pb collisions to pp collisions. Furthermore, the in-medium jet modification can be more precisely measured by comparing jets which traverse different pathlengths through the medium. The pathlength dependence of the jet modification can be observed with $I_{AA}$ as a function of the relative angle between the trigger particle and the event plane.
In this presentation, $I_{AA}$ as a function of centrality, relative angle to the event plane, and the transverse momentum of the associated particles for Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV will be shown. In addition, the results will be compared to AMPT model calculations.

Speaker: Hyeonjoong Kim (Yonsei University (KR))

2018-may-08-conference_presentation-qm_poster_final (1).pdf

382 Performance and Design of the Transition Radiation Detector for the CBM Experiment

The Compressed Baryonic Matter (CBM) experiment will be installed at the SIS100 accelerator at FAIR and is currently in construction. It is devoted to precision measurements of QCD matter at high net-baryon densities. With heavy-ion interaction rates up to $10\;\textrm{MHz}$, rare probes like, e.g., multi-strange hyperons will be accessible. In-medium mass distributions of vector mesons can be measured via lepton pairs and excitation functions of various observables will serve as sensitive probes for phase transitions. This talk reports on the Transition Radiation Detector (TRD) of CBM. Multi-Wire Proportional Chambers (MWPCs) for this detector are challenged to record the mentioned unprecedented heavy-ion interaction rates, which will result in particle rates at the TRD plane up to $120\;\textrm{kHz}\;\textrm{cm}^{-2}$: the MWPCs will therefore be built in a fast design with signal collection times below $300\;\textrm{ns}$ and nevertheless deliver an excellent pion suppression.

The physics case, the detector concept and its PID as well as tracking performance will be presented. The TRD will, for instance, be essential for the identification of hypernuclei and the measurement of intermediate mass dielectrons. The latest evolution of the fully self-triggered and free-streaming read-out chain will be shown. In 2017, testbeam measurements have been performed in DESY II electron beam and in the high-rate environment of the Gamma Irradiation Facility (GIF$^{++}$) at CERN. Results from these tests will be presented and their implications discussed.

Speaker: Christoph Blume (Johann-Wolfgang-Goethe Univ. (DE))

QM2018_CBM-TRD_poster.pdf

383 Performance of Elliptic Flow Studies at NICA / MPD

The Nuclotron-based Ion Collider fAcility (NICA) is a new accelerator complex being constructed at the Joint Institute for Nuclear Research (JINR). The general goal of the project is to study the hot and dense baryonic matter in heavy ion collisions in the energy range up to $\sqrt{s_{NN}}$ = 11 GeV and average luminosity of $L = 10^{27}$ cm$^{-2}$s$^{-1}$ for Au+Au collisions. Anisotropic flow presents a unique insight into heavy ion collision physics. Presented are simulation results for performance in elliptic flow ($v_{2}$) measurements by the Multi-Purpose Detector (MPD) for identified and reconstructed hadrons.

Speaker: Mr Nikolay Geraksiev (JINR)

GeraksievPoster2018.pdf

384 Performance of Heavy-flavor Tagged Jet Identification in STAR

The measurement of heavy-flavor tagged jets in relativistic heavy ion collisions is an important tool to study the properties of the hot and dense QCD medium. While the flavor dependence of jet quenching has been attributed to several physics mechanisms, such as collisional and radiative energy losses of hard-scattered partons, previous measurements at the LHC have not shown a strong flavor dependence of jet quenching in the jet transverse momentum ($p_{\mathrm{T}}$) range of $80$-$250$ GeV/$c$ in heavy ion collisions. However, experimental inability to distinguish prompt heavy-flavor quarks and those from gluon splitting has limited the quantitative interpretation of currently available measurements. Compared to collision energies at the LHC, the fraction of heavy-flavor quarks from gluon splitting to prompt heavy-flavor quarks is predicted to be lower at RHIC energies, making flavor-dependent measurements more accessible. In this poster, performance studies of heavy-flavortagged jet identification in the STAR experiment at RHIC are reported.

STAR's recent addition of the Heavy Flavor Tracker (HFT) provides significantly improved resolution of secondary vertices and thus excellent identification of particles containing heavy quarks. Taking advantage of the HFT capability, we have developed a number of heavy-flavor jet tagging algorithms based on properties of reconstructed secondary vertices and properties of constituent tracks. Tagging efficiency and misidentification rate of each algorithm are investigated via Monte Carlo simulations. These performance results will be used as a basis for upcoming STAR measurements on flavor dependence of jet quenching in heavy ion collisions.

Speaker: Saehanseul Oh (Yale University and Brookhaven National Laboratory)

QM18poster_HFjet_SOh.pdf

385 Performance of the large Time-Of-Flight detector of ALICE

The Time-Of-Flight detector of ALICE has set a new record in the realm of large-area highly-segmented gaseous timing detectors. The apparatus covers the ALICE central barrel with high-performance MRPC strip detectors for a total active area of 140 square metres segmented into about 150000 readout channels, delivering crucial particle-identification information and contributing to a diverse set of physics measurements. Thanks to a new calibration campaign and the larger data sample available with the Run-2 data-taking at the LHC, a deeper and more refined knowledge of the detector characteristics is possible. As a consequence a significant improvement of its timing performance was achieved reaching a global time resolution better than 60 ps. After almost ten years of operations at the LHC with proton and nuclear collisions, the TOF detector of ALICE continues to show very high efficiency and top performance. The results of a comprehensive analysis of the ALICE TOF detector will be presented as well as the plans for its upgrade programme for a continuous readout mode in LHC Run3 and Run4.

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

QM_carnesecchi.pdf

386 Performance of the new DiRICH based readout chain for MAPMTs in test beam data

Modern RICH detectors often employ Multianode Photomultiplier tubes (MAPMTs), providing excellent timing properties, good quantum efficiency, fine granularity and low dark noise. The CBM RICH detector, as well as the upgraded HADES RICH detector, will both use, actually even share, Hamamatsu H12700 MAPMTs for spacially resolved Cherenkov photon detection. A new FPGA-TDC based electronic readout chain has been developed for the readout of MAPMTs or MCPs with the 32ch DIRICH readout module as its core component. The signal discrimination, time- and time-over-threshold measurement, as well as digital data handling, are all implemented on a central Lattice ECP5 FPGA, providing a very cost-efficient and powerful solution. Another important aspect is the very low power consumption (12 mW/amplifier, 50 mW per channel, including discrimination, TDC, and data handling).
The new readout chain has been tested at the COSY accelerator, Forschungszentrum Jülich, for the first time under realistic beam conditions, using a small Cherenkov prototype detector. Cherenkov photons were produced by the 600 MeV proton beam passing a solid Cherenkov radiator made of 3 mm quartz. The photons were registered by 12 MAPMTs read out using 24 DIRICH modules, with a total of 768 individual channels. In addition to the readout electronic test, a wavelength shifter (WLS) coating on the MAPMTs was tested.

The poster will present first performance results from the analysis of the COSY beamtime data, focusing in particular on efficiency and timing precision, and the potential suppression of crosstalk and noise by making use of the precise Time-over-Threshold information. In addition, the effect of the WLS coating on efficiency and timing properties is investigated.

Speakers: Mr Vivek Patel, Mr Adrian Amatus Weber

QM2018_AWeber_VPatel.pdf

387 Performance of the STAR Event Plane Detector

The Beam Energy Scan (BES) program at the Relativistic Heavy-Ion Collider has shown hints of a critical point and first order phase transition at the BES energies. Key measurements for locating the critical point and determining the first order phase transition are limited by poor event plane resolution, limited statistics and a TPC-only centrality determination. A new event plane and collision centrality detector (EPD) is planned to replace the existing detector, the Beam-Beam Counter (BBC), with higher granularity and acceptance. The design of the EPD consists of two scintillator discs at z = $\pm$ 3.75 m from the center of STAR, covering $2.1<|\eta|<5.1$. The EPD is estimated to increase 1st order Reaction Plane resolution by a factor of at least 1.5 and has timing resolution on the order of 1 ns. One quarter of a single disc was installed in STAR for the 2017 run for commissioning. We will discuss the detector performance during the 2017 commissioning run in AuAu collisions at $\sqrt{s_{NN}}$ = 54.4 GeV and the 2018 isobar run. Outlook on the performance of the EPD in BESII will also be discussed.

Speaker: Justin Ewigleben (Lehigh University)

QM18_Ewigleben_EPD_v4.1.pdf

388 Performance​ for​ anisotropic​ flow​ measurements​ of​ the​ future​ CBM​ experiment​ at​ FAIR

The Compressed Baryonic Matter experiment (CBM) at FAIR aims to study the area of the QCD phase diagram at high net baryon densities and moderate temperatures using collisions of heavy ions at center-of-mass energies of a few GeV per nucleon. Anisotropic transverse flow​ ​is​ ​among​ ​the​ ​key​ ​observables​ ​to​ ​study​ ​the​ ​properties​ of​​ matter​ created​ in​ such​ ​collisions.

The CBM performance for anisotropic flow measurements is studied with Monte-Carlo simulations using gold ions at SIS-100 energies with lab momentum of 2-10 AGeV employing different heavy-ion event generators. Various combinations of CBM detector subsystems are used to investigate the possible systematic biases in flow measurement and to study effects of detector azimuthal non-uniformity. The resulting performance of CBM for flow measurements is demonstrated for different harmonics of identified charged hadron anisotropic flow as a function of rapidity and​ transverse​ momentum​ in​ different​ centrality​ classes.

The measurement techniques developed for CBM were also validated with the experimental data recently collected by the NA61/SHINE experiment at CERN SPS for Pb-Pb collisions at the beam momenta 13 and 30 AGeV (the first energy point is close to the top SIS-100 energy). This is also of importance for CBM performance studies, because both CBM and the NA61/SHINE are fixed target experiments and have a similar Projectile Spectators Detector (PSD)​ ​as​​ a​​ part​​ of​​ their​ setup.

Speaker: Viktor Klochkov (GSI / Frankfurt Uni)

qm2018_cbm_flow_poster.pdf

389 PHENIX measurement of J/psi polarization via decay di-electron pairs produced in p+p collisions at sqrt(s) = 510 GeV at mid-rapidity

Heavy quarkonia in high-energy collisions is a sensitive probe of Quantum Chromo Dynamics (QCD) due to its large scale provided by the heavy quark mass relative to the hadronization scale. The angular distribution of decay leptons from heavy quark bound state is a key observable to test heavy quarkonia production mechanisms and bound state formation. Charmonium, in particlular, is an essential tool as it decays into di-leptons with a large branching ratio. PHENIX and STAR have observed J/$\psi$ polarization consistent to zero within uncertainties with limited statistics via measurements of polar angular distribution in decay di-electron pairs at $\sqrt{s}$ = 200 GeV at midrapidity. Recently, measurement of full (polar and azimuthal) angular distribution from J/psi decay to di-muon pairs at $\sqrt{s}$=510 GeV in the forward rapidity region has shown good agreement with predictions made by non-relativistic QCD at high pT and disagreement at low pT, posing a challenge to this theoretical approach. This poster will present the status of data analysis underway on the data taken from p+p collisions at $\sqrt{s}$=510 GeV in 2013 at RHIC. This new measurement of J/psi polarization via full angular distribution from J/$\psi$ decays to di-electrons at mid-rapidity $|y|<$0.35 at this higher energy will bring new insights into charmonium production and hadronization process.

Speaker: Sookhyun Lee (Iowa State University)

390 PHENIX measurements of $J/\psi$ and $\psi(2S)$ production at forward and backward rapidity in p/d/$^{3}$He+Au and p+Al collisions at 200 GeV

Bound states of heavy quarks produced in collisions of large nuclei have been the object of intense experimental and theoretical interest for decades, but precise quantification of the various mechanisms affecting their production from p+A collisions to A+A collisions is still not totally understood. One advantage of the RHIC accelerator complex is the flexibility of beam species available for collisions, and the PHENIX Collaboration has collected data from small reaction volumes produced in p/d/$^{3}$He+Au collisions and p+Al collisions. Based on these various data sets, we can study the evolution of nuclear effects on charmonia production as the size of collision system changes. Measurements at forward and backward rapidity (1.2<|y|<2.2) also allow us to study different regions of the nuclear PDF, the effects of nuclear crossing time, and various regions of final state charged particle multiplicity which may influence bound state formation. In this presentation, we will discuss these effects in the context of our results on J/$\psi$ and $\psi$(2S) production at forward and backward rapidity in p/d/$^{3}$He+Au and p+Al collisions.

Speaker: John Matthew Durham (Los Alamos National Laboratory)

391 PHENIX Measurements of Bottom and Charm Quark Production at Mid Rapidity in p+p Collisions at $\sqrt{s} = $ 200 GeV

Heavy quarks are important probes of the properties of the Quark Gluon Plasma (QGP) produced in heavy ion collisions. At RHIC energies charm and bottom quarks are valuable as they are produced primarily in the initial collision, and not through the thermalization of the QGP. PHENIX has previously published, and shown, the invariant yields of bottom and charm quarks in Au-Au collisions at $\sqrt{s}=$ 200 GeV. In order to study QGP effects a similar analysis has now been done in p+p at $\sqrt{s} =$ 200 GeV, extracting a p+p baseline for the full range of 1-8 GeV in electron transverse momentum. The analysis uses Bayesian unfolding techniques applied to both an inclusive heavy flavor invariant differential cross-section and measured distance of closest approach for electron candidates to extract bottom and charm hadron invariant yields. This poster will present recent PHENIX results of bottom and charm hadrons obtained from the 2015 p+p dataset, as well as details of the analysis procedure.

Speaker: Marzia Rosati (Iowa State University (US))

392 PHENIX measurements of charged hadron and heavy flavor v2 at forward/backward rapidity in d+Au collisions at sqrt{s}=200 GeV

Recent measurements at both RHIC and the LHC continue to indicate that particles produced in small collision systems exhibit collective behavior similar to those observed in large collision systems. The PHENIX experiment has measured substantial elliptic ($v_2$) flow coefficients for charged hadrons at midrapidity in a suite of small collision systems over a range of collision energies. We extend these results with new measurements of charged hadron $v_2(p_T)$ at forward and backward rapidities in $d+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV in order to better constrain the rapidity extent of these correlations. To further investigate the origins of these correlations we also present the status of the $v_2$ of heavy flavor decay muons at forward and backward rapidities in the same collision system.​

Speaker: Darren McGlinchey (Los Alamos National Laboratory)

McGlinchey_poster_QM2018.pdf

393 PHENIX measurements of elliptic and triangular flow in $d$+Au collisions

Results on azimuthal anisotropies in the particle production from $p+p$ and $p/d/^{3}$He+A at LHC and RHIC have raised the question of how small a system can be while still exhibiting collective behavior. In 2016, RHIC operations included $d$+Au collisions at $\sqrt{s_{NN}}=$ 200, 62.4, 39, and 19.6 GeV. In this poster we present results on elliptic and triangular flow at midrapidity as a function of transverse momentum in $d$+Au collisions. We compare these results with several theoretical predictions in scenarios including viscous hydrodynamic flow, partonic scattering, and purely hadronic scattering in order to assess the origin of collectivity in the smallest systems.

Speaker: Victoria Greene (Vanderbilt University (US))

Greene-PHENIX-SmallSystems-QM2018-final.pdf

394 PHENIX results on Bose-Einstein correlation functions using a Lévy analysis in Au+Au collisions at RHIC

The RHIC beam energy scan program allows for the investigation of the phase
diagram of QCD matter by varying the beam energy in the region where the change from crossover to first order phase transition is expected to occur. The nature of the quark-hadron transition can be studied through analyzing the space-time structure of the hadron emission source. An excellent tool to gain information about the source is the measurement of Bose-Einstein or HBT correlations of identical bosons. In recent measurements, we utilized Lévy-type sources to describe the measured two-particle correlation functions. In this presentation we report on the detailed measurements of the Lévy source parameters as a function of transverse mass.
We discuss the collision energy and centrality dependence of the Lévy-exponent,
which is related tp the spatial correlation exponent. We also discuss the Lévy-
scale, as well as that of the correlation strength and its relation to the
$\eta '$ mass.

Speaker: Sándor Lökös

poster_newstyle.pdf

395 PHENIX results on centrality and collision energy dependent Lévy analysis of HBT correlation functions

Varying the center of mass energy and the centrality in heavy-ion collisions allows us to investigate different regions of the QCD phase diagram. In our latest measurements at the PHENIX experiment at RHIC, we utilize Lévy-type sources to describe the measured HBT correlation functions at different beam energies and centralities. The different source parameters can yield different information about the source. The scale parameter $R$ is related to the physical size of the source, while the $\lambda$ parameter (the strength of the correlation function) may provide an indirect measurement of in-medium mass modification. The index of stability $\alpha$ is related to one of the critical exponents (the so-called correlation exponent $\eta$), so it may yield information on the nature of the quark-hadron phase transition. In this poster we report the current status of the analysis of the centrality and beam energy dependence of Lévy source parameters in Au+Au collisions from $\sqrt{s_{NN}}=15$ GeV to $\sqrt{s_{NN}}=200$ GeV.

Speaker: Dániel Kincses (Eötvös Loránd University)

QM18_poster_kincsesd_v4.pdf

396 PHENIX results on collectivity in d+Au collisions from 200 to 19.6 GeV

Small system (p+p, p+A, d/He+A) collisions at RHIC and LHC exhibit interesting
azimuthal anisotropies, with explanations varying from geometry coupled to final
state interactions to glasma diagrams to color recombination. The PHENIX
experiment has extended many of these observables to even lower energies with the d+Au beam energy scan at 19.6, 39.0, 62.4, and 200 GeV.

We present results on $v_2$ anisotropies as a function of transverse momentum and pseudorapidity for various centrality selections. We also study multi-particle cumulants ($v_2\{2\}, v_2\{4\}, v_2\{6\})$ that provide additional information about flow, non-flow and event-by-event fluctuations. We compare the results with calculations within the framework of viscous hydrodynamics and parton scattering models (with and without final state interactions). The results provide key evidence for collectivity from the lowest RHIC energies to the highest LHC energies.

Speaker: Kenta Shigaki (Hiroshima University (JP))

397 PHENIX results on three-dimensional Bose-Einstein correlations in $\sqrt{s_{\rm NN}}$ = 200 GeV Au+Au collisions

The Bose-Einstein correlation of identical bosons may give information about the space-time structure of the sQGP created at the ultrarelativistic heavy ion collisions. Previous measurements have shown that, instead of the Gaussian-type of source, one should rather consider a more general Levy-type source, which gives a better descripiton of the data. Moving to three dimensions from one-dimensional measurements gives insight into the nature of the expanding system by measuring the parameters of a Levy-type source in three (out, side, long) directions. We can also measure the deviation from the Gaussian source in three dimensions. In this poster we present the transverse mass dependence of the Levy source parameters. The shape parameter ($\alpha$) describes the stability of the source. The HBT-radii ($R_{out}, R_{side}, R_{long}$) measure the physical size of the source, and the correlation strength ($\lambda$) measures the ratio of pions originated from resonance decays. The measurement is being done on Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 200 GeV for $\pi\pi$ pairs.

Speaker: Bálint Kurgyis

kurgyis_QM18_3d_levy.pdf

398 Photon - Hadron Correlations in Heavy Ion Collisions from PHENIX

Direct photon-jet pairs are produced in the initial hard scattering of nucleons in A+A collisions in which a quark-gluon plasma is formed. The photon is not affected by the quark-gluon plasma, while the jet loses energy. This allows the direct photon to be an energy calibrator for the jet which can then be studied through photon-hadron pair correlations. Obtaining direct photons is challenging because of the myriad of background photons. Typically, a statistical subtraction method is used in A+A at RHIC. In addition to a statistical method, we have also developed a direct method to obtain isolated photons in A+A by using an isolation cut like those used in direct photon identification in p+p collisions. The isolation cut provides for a cleaner sample of direct photons, potentially reducing the systematic uncertainties on direct photon-hadron correlations when compared to the statistical subtraction sample but presents its own new challenges in the high multiplicity A+A environment. We present the status of centrality-dependent direct photon-hadron angular correlations and fragmentation functions in A+A collisions as well as results from recent high-statistics PHENIX datasets.

Speaker: Mr Tyler Danley (PHENIX Collaboration)

399 Photon Hadron Discrimination in Photon Multiplicity Detector

A density based algorithm has been applied for clustering of cell-hits in the Photon Multiplicity Detector(PMD) installed in the ALICE experiment at CERN. This approach is shown to produce better clustering and thus better correlation among the cell-hits on the two planes of PMD and high energy primary photons. Sixteen features are ex- tracted from the clusters and three multivariate techniques, namely Boosted Decision Trees, Support Vector Machines and Bayesian Neural Networks are used to obtain a classification of hits as either photons or hadrons. The final result is shown to have both a better efficiency as well as better purity of particle identification than the cut based scheme. This has important implications in the search for the Disoriented Chiral Condensates (DCC) conjectured to be formed in relativistic collisions. This is primarily because the cut based analysis relies on high energy cuts on the energy of the photons to obtain reasonable efficiency and purity. This would eliminate low energy photons resulting from the decay of off-shell pions. The work in important as it would be a direct signature of chiral phase transition in these collisions.

Speaker: Prof. Raghava Varma (I.I.T. Bombay)

400 Photons as probes of gluon saturation in p+A collisions

We compute the cross section for photons emitted from a $q\bar{q}$ pair produced from gluon splitting in proton-nucleus (p+A) collisions at ultra-relativistic energies [1]. The computation is performed within the dilute-dense kinematics of the Color Glass Condensate (CGC) effective theory. Although the result obtained is formally at next-to-leading order in the CGC power counting, it provides at higher energies the dominant contribution for central rapidities.
We present the first numerical results for the photon cross-section including both the leading order terms computed previously [2,3] supplemented by novel next-to-leading results [4]. We compare the relative contributions of the LO and the NLO terms at different collider energies, and present detailed comparisons to data from RHIC and LHC on p+p and p/d+A collisions.

References:
[1] S. Benic, K. Fukushima, O. Garcia-Montero, R. Venugopalan, JHEP 1701 (2017) 115
[2] J. Jalilian-Marian and A.H. Rezaeian, Phys. Rev. D 86 (2012) 034016
[3] B. Ducloué, T. Lappi, H. Mäntysaari, arXiv: 1710.02206
[4] S. Benic, K. Fukushima, O. Garcia-Montero, R. Venugopalan, (In preparation)

Speaker: Oscar Garcia Montero (Karl-Ruprechts-Universität Heidelberg)

posterOscarGarciaMontero.pdf

401 Pion induced reaction with carbon and polyethylene targets obtained by HADES-GSI in 2014

In the summer of 2014, HADES conducted measurements with secondary pion-beam using different targets. The program is devoted to measure dielepton radiation from baryonic resonances. In particular we investigated a sub-threshold coupling of rho to baryonic resonances in the second resonance region, specially N(1520). Most of the beam time was dedicated to measurement of $e^{+}e^{-}$ production from PolyEthylene target at pion beam momentum of 690 $MeV/c$. Combining these data with carbon data it is possible to extract pion-proton interactions. Therefore it was possible to measure at the same time exclusive $\pi^{-}p \rightarrow e^{+}e^{-}$ and inclusive $e^{+}e^{-}$ production. The normalization of spectra has been done using elastic scattering of pion on proton. The identification of $e^{+}e^{-}$ is was performed through appropriate cuts on time-of-flight, energy loss, shower signal and RICH (Ring Imaging Cherenkov) observables. Exclusive and inclusive invariant mass spectra is compared with the different channel contributions simulated with a dedicated Monte Carlo simulation tool for hadronic physics (PLUTO). Using missing mass cuts it was possible to identified the events from the reaction $\pi^{-}p \rightarrow n e^{+}e^{-}$ which shows that the $e^{+}e^{-}$ yield of invariant mass above 250 $MeV/c^{2}$ is consisted with $N(1520)\rightarrow n\rho\rightarrow ne^{+}e^{-}$. Models associate the excess of dilepton measured in heavy ions reactions with the excitation and decay of baryonic resonances of dileptons via intermediate $\rho$ meson

Speaker: Pablo Rodríguez-Ramos (Nuclear Physics Institute ASCR)

Poster_QM2018_Pablo_Rodríguez_Ramos.pdf

402 Pion-Kaon femtoscopy in Pb-Pb collisions at 2.76 TeV measured with ALICE

Femtoscopic correlation between charged pions and kaons for different charge combinations are measured in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV with ALICE at the LHC. The three-dimensional pion-kaon correlation functions and double ratios in out-side-long pair rest frame are studied in different centrality bins. The $\pi$-K femtoscopic source size parameter ($R_{\pi K}$) and emission asymmetry ($\mu$) are extracted. It is observed that average source size of the system and emission asymmetry between pions and kaons increase from peripheral to central events.

Speaker: Sadhana Dash (IIT- Indian Institute of Technology (IN))

qm18_ver4.pdf

403 Plasmon mass scale in classical nonequilibrium gauge theory in two and three dimensions

The initial stage of a relativistic heavy ion collision is dominated by an overoccupied, strong gluon field, which can be understood in a classical approximation. The physics of equilibration and isotropization of this field is dominated by the plasmon mass scale, which is poorly understood in this very nonequilibrium system. We address this by measuring the plasmon mass scale in two and three dimensional classical Yang-Mills systems numerically. We use three different methods: a Hard Thermal Loop (HTL) expression involving the quasiparticle spectrum constructed from Coulomb gauge field correlators, an effective dispersion relation (DR) and the measurement of oscillations between electric and magnetic energies after introducing a spatially uniform perturbation to the electric field (UE). We find that the HTL and the UE methods are in rough agreement. The DR method agrees with other methods within a factor of two. We also study the dependence on time and occupation number. We observe that a power law dependence sets in in both cases after an occupation number dependent transient time. We find that in both cases our results are insensitive to the infrared cutoff. In three dimensions we find that the UE and HTL measurements can be brought into agreement when we take the ultraviolet cutoff to zero. However, in two dimensions the results obtained using all three methods seem to increase when we take the ultraviolet cutoff to zero. At late times in three spatial dimensions, the square of the plasmon mass seems to scale as $t^{-2/7}$, which is also predicted by kinetic theory analysis and previous research. In two dimensions the square of the plasmon mass seems to decrease as $t^{-1/3}$ according to HTL method measurement.

Speaker: Jarkko Peuron (University of Jyväskylä)

QMposter.pdf

404 Practical considerations for measuring global spin alignment of vector mesons in relativistic heavy ion collisions

The study of global polarization and spin alignment can help us probe the vorticity field generated by the initial global angular momentum and understand particle production mechanisms during hadronization. For those reasons this topic is gaining increasing interest in recent years. The study of spin alignment (quantified by $\rho_{00}$) of vector mesons involves the reconstruction of the direction of global angular momentum (L), which is the normal to the reaction plane (RP). In experiments the RP is estimated with correlations among particles and has finite resolution. In this poster, we demonstrate a procedure to correct $\rho_{00}$ for the finite RP resolution. In addition, since the 1st- and 2nd-order RP are usually not the same and they have different sensitivity to L, we derive a relationship to explain the $\rho_{00}$ obtained between the two RP. Furthermore, a deviation of $\rho_{00}$ from 1/3 can be caused by finite acceptance in pseudo rapidity (e.g., the case for STAR and ALICE). We demonstrate that this effect can be corrected elegantly in a data-driven approach. At last, because vector mesons can have an apparent spin alignment in the helicity frame (local $\rho_{00}$), this will cause an artificial azimuthal angle dependence when study the global $\rho_{00}$ as a function of emission angle with respect to the RP. We lay down a procedure to correct for this effect as well as a procedure to correct for the effect of smearing $\rho_{00}$ in azimuth bins.

Speaker: Dr Aihong Tang (Brookhaven National Lab)

405 Predictions for event-by-event flow harmonic distributions at RHIC

Hydrodynamical models must be able to reproduce data not only in average for a given centrality class but for each event. In particular they must reproduce the scaled $v_n$ distributions obtained by ATLAS [1,2] and ALICE [3]. These distributions are independent of medium properties such as viscosity, and so directly probe the initial conditions.

They in fact provide a strong test for initial condition models: many models (e.g. Glauber and MC-KLN) can be ruled out and so far only two models lead to satisfactory results [4,5]. In this work, we show that NeXus initial conditions also provide reasonable results for scaled $v_n$ distributions at LHC energies and make predictions for RHIC top energy.

References:
[1] ATLAS Collaboration Nucl. Phys. A 904-905 421c (2013)
[2] ATLAS Collaboration JHEP 1311 183 (2013)
[3] ALICE Collaboration J. Phys. Conf. Ser. 446 012031 (2013)
[4] C. Gale, S. Jeon, B. Schenke, P. Tribedy, and R. Venugopalan, Phys. Rev. Lett. 110, 012302 (2013),
[5] H. Niemi, K. J. Eskola, and R. Paatelainen, Phys. Rev. C 93, 024907 (2016)

Speaker: Leonardo Barbosa (Instituto de Física da Universidade de São Paulo)

LeonardoQM2018_Final.pdf

406 Preliminary study of the (anti-)deuteron absoprtion in the detector material of ALICE at the LHC

The interaction cross section of nuclei and anti-nuclei with matter is not well known in the momentum region from about 3 GeV/c down to about 0.7 GeV/c. The determination of this cross section will be of crucial importance for the precise measurement of the (anti-)nuclei production in pp, p-Pb and Pb-Pb collisions at the LHC because this lack of information is presently the biggest source of systematic uncertainties. As a matter of fact, different transport codes used for the data and MC reconstruction reproduce different tracking efficiencies for (anti-)nuclei. In this poster, a preliminary study of the (anti-)deuteron absorption in the detector material of ALICE will be presented, exploiting the fact that, during the Run 1 data taking, few modules of the Transition Radiation Detector (TRD) were not yet installed, leaving empty spaces between the Time Projection Chamber and the Time-Of-Flight Detector, in a portion of the azimuthal acceptance.
A first analysis of the effect due to the presence of the additional material of the TRD will be performed, based on the p-Pb data sample. The ratio between the spectra of deuterons passing through the TRD and those passing in the regions where the TRD was not installed is determined. The choice of the p-Pb data sample with respect to Pb-Pb collisions will help in limiting the background due to the secondary deuteron contamination. Possible improvements in such a study and the perspectives in view of the LHC Run3+4 will be presented.

Speaker: Alexander Philipp Kalweit (CERN)

407 Probing beauty and charm production in p-Pb collisions with high pT electrons measured with ALICE

Lattice Quantum Chromodynamics (QCD) calculation predicts that a colour-deconfined Quark-Gluon Plasma (QGP) is formed at high temperature and high energy density reached in ultra-relativistic heavy-ion collisions. Heavy quarks (charm and beauty) are mostly produced by initial hard scatterings before the formation of the QGP. Therefore heavy-flavour hadrons are ideal probes to investigate the properties of the hot and dense QCD matter. In Pb-Pb collisions, a strong suppression of the production of heavy-flavour hadrons with high transverse momentum has been observed.
　A deeper understanding of heavy-flavour production in nucleus-nucleus collisions requires detailed studies of Cold Nuclear Matter (CNM) effects in order to clarify the role of initial- and final-state effects on their production. CNM effects include shadowing and/or saturation of partons, energy loss in CNM and $k_{\rm{T}}$-broadening. Such effects on heavy quark production can be studied in proton-nucleus collisions by measuring electrons from heavy-flavour hadron decays.
　The nuclear modification factor of electrons from heavy-flavor hadron decays was measured up to $p_{\rm{T}}$ = 20 GeV/$c$ in p-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 5.02 eV. The result suggests that heavy-flavour production in p-Pb collisions scales with the number of binary nucleon-nucleon collisions. High $p_{\rm{T}}$ electrons are particularly interesting because they mainly originate from beauty hadron decays. In this poster we will present new results on the production of electrons from heavy-flavor hadron decays and its nuclear modification factor up to approximately 30 GeV/$c$ in p-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 8.16 TeV collected in LHC-Run2 in 2016.

Speaker: Daichi Kawana (University of Tsukuba (JP))

QMposter_HFEpPb8TeV_v10.pdf

408 Probing QCD phase diagram with light nuclei production in relativistic heavy-ion collisions

Fluctuation signals of phase transitions from quark-gluon plasma (QGP) to hadronic matter can greatly advance our knowledge of the nature of strong interaction. In relativistic heavy-ion collisions, the enhanced density fluctuations due to phase transitions (either first-order or second-order at CEP) can cause large correlations in nucleon densities at final state, which in turn affect the productions of composite particles like light nuclei. The light nuclei (e.g. deuteron) can only be formed within a restricted volume in phase space, therefore, they can probe local density fluctuation.

I will demonstrate the usefulness and advantage of probing the QCD phase diagram with light nuclei in relativistic heavy-ion collisions.

Especially, from recent experimental data in central Pb+Pb collisions at the CERN Super Proton Synchrotron (SPS) energies measured by the NA49 Collaboration, we find significant non-monotonic behaviours of nucleon density correlations and fluctuations. The results indicate that the density fluctuations become the largest in collisions at $\sqrt{s_{NN}}=8.8$~GeV. With the known chemical freeze-out conditions determined from the statistical model fit to experimental data, we obtain a chemical freeze-out temperature of $\sim 144~$MeV and baryon chemical potential of $\sim 385~$MeV at this collision energy, which are close to those predicted by various theoretical studies for the critical endpoint in the QCD phase diagram.

Speaker: Dr Sun Kai-Jia (Department of Physics and Astronomy and Shanghai Key Laboratory for Particle Physics and Cosmology)

KaiJiaSunQM2018Poster.pdf

409 Probing the thermal state of the fireball at freezeout via isothermal compressibility and specific heat capacity

The thermal state of the fireball at freezeout has been inferred from the mean hadron yields previously. In this study, we go beyond the mean hadron multiplicities and access the variances from multiplicity and transverse momentum distributions that provide us the thermodynamic responses of the fireball at freezeout – namely the isothermal compressibility ($k_T$) and specific heat capacity ($c_v$) that enable us to determine the thermodynamic state of the fireball at freezeout independently of the mean hadron yields. Further, in case the freezeout lies in the critical region of the QCD phase diagram, evidence of criticality could also show up in $k_T$ and $c_V$.

We have for the first time estimated $k_{T}$ of the system formed in heavy-ion collisions for energies from 7.7 GeV to 2.76 TeV, with the help of event-by-event multiplicity fluctuations. An estimate of the dynamical fluctuation has been made from the experimental data by subtracting the statistical fluctuation within the approximation of the participant model. For $c_v$, the experimental data on the event-by-event mean transverse momentum distributions are transformed to distributions of effective temperatures and the dynamical temperature fluctuations are obtained by subtracting the widths of the corresponding mixed event distributions. We have compared our results with model expectations based on the hadron resonance gas model as well as event generators. The estimation of $k_{T}$ and $c_{v}$ complements our previous understanding of the thermal state of the fireball at freezeout based on mean hadron yields.

Speaker: Dr Maitreyee Mukherjee (Central China Normal University)

410 Production and azimuthal anisotropy of beauty decay electrons in Pb--Pb collisions at 2.76 TeV with ALICE

The study of the interaction of heavy quarks with the constituents of the medium created in heavy-ion collisions provides important information about the characteristics of the Quark-Gluon Plasma (QGP). The production of heavy quarks occurs prior to the formation of the QGP, implying that they experience the entire evolution of the system. To infer the properties of the partonic interactions of charm and beauty quarks in the medium, it is useful to investigate how heavy quarks are influenced by the collective expansion of the system. A sufficiently strong interaction could lead to a themalization of the heavy quarks which then would move along with the flow of the surrounding medium constituents leading to a substantial azimuthal anisotropy in non-central collisions.
The excellent particle-identification capabilities of the ALICE detector allow for an investigation of beauty production via the measurement of beauty-hadron decay electrons. The separation from background electrons is achieved via a statistical separation based on the track impact parameter distribution. This distribution is wider for the beauty decay electrons due to the comparatively larger decay length of their parent hadrons ($c\tau\approx500\,\mathrm{\mu m}$). This poster shows the current status of the measurements of the production and azimuthal anisotropy of beauty electrons in Pb--Pb collisions at$\sqrt{s_{\tiny NN}}=2.76~\mathrm{TeV}$.

Speaker: Martin Andreas Volkl (Eberhards Karls Universiy Tubingen (DE))

VoelklQMPosterFinal.pdf

411 Production of D± Mesons in Au+Au Collisions at √sNN = 200 GeV Measured by the STAR Experiment

Charm quarks are primarily produced at early stages of ultra-relativistic heavy ion collisions and can be used to probe the properties of the quark-gluon plasma (QGP) created in these collisions. Final-state open charm mesons are usually used experimentally to study the charm quark interaction with the medium. For example, suppression of D-meson production in heavy-ion collision is sensitive to the energy loss of charm quarks in the QGP. In this poster, the production of D$^{\pm}$ mesons in Au+Au collisions at $\sqrt{s_\mathrm{NN}}$ = 200 GeV measured by the STAR experiment using data taken in 2016 is presented. Precise topological reconstruction of secondary decay vertices enabled by the STAR Heavy Flavor Tracker through the hadronic decay channel, $\mathrm{D^{\pm} \rightarrow K^{\mp}\pi^{\pm} \pi^{\pm} }$, is used in this analysis. The nuclear modification factor of the D$^{\pm}$ meson will be shown as a function of transverse momentum as well as the collision centrality.

Speaker: Jan Vaněk (Nuclear Physics Institute, Czech Academy of Sciences)

QM18poster_Vanek_v2.0_final.pdf

412 Production of electrons from beauty-hadron decays in Pb-Pb collisions at 5.02 TeV with ALICE

Heavy-flavour quarks (charm and beauty) are an important tool used to probe the Quark Gluon Plasma (QGP), the colour-deconfined medium created in ultrarelativistic heavy-ion collisions. They are created in the first stages of the collision, mainly via hard parton scattering, and they experience the whole evolution of the medium. The study of the energy loss of heavy-flavour quarks is of particular interest to understand the mass dependence of energy loss in the QGP.
We will show the status of the measurement of electrons from beauty hadron decays in Pb-Pb collisions at 5.02 TeV using the ALICE detector. Electrons with low transverse momentum (1 < $p_{\rm T}$ < 6 GeV/c) are identified using the Time Projection Chamber (TPC) and Time-Of-Flight detectors, while high-momentum electrons (6 < $p_{\rm T}$ < 20 GeV/c) are identified using the TPC and the Electromagnetic Calorimeter. Beauty decay electrons are extracted by performing fits to the impact parameter distribution using templates of different electron sources obtained from Monte Carlo simulations. At low $p_{\rm T}$, templates of impact parameter distribution for electrons from gamma, Dalitz, charm and beauty decays are used to obtain the relative fraction of each source. At high $p_{\rm T}$, the invariant mass of electron-positron pairs is used to identify electrons from gamma conversions and Dalitz decays, and only the templates for charm and beauty decay electrons are used in the impact parameter fit.

Speakers: Camila De Conti (Universidade de Sao Paulo (BR)), Erin Frances Gauger (University of Texas at Austin (US))

BeautyElectronsRAA_PbPb5_v7.pdf

413 Production of electrons from beauty-hadron decays in pp collisions at the LHC with ALICE

The measurement of heavy-flavor production cross sections in pp collisions at LHC energies is an excellent tool to test perturbative Quantum Chromodynamics calculations. Due to their large masses, charm and beauty quarks are mainly produced in hard scattering processes at the initial stage of the collisions. Moreover, beauty-hadron measurements in pp collisions are essential as a baseline for understanding beauty-quark production and in-medium energy loss in heavy-ion collisions. In this poster, we will describe the analysis of the electron impact-parameter distribution performed to separate the electrons from beauty decays from the other sources. The identification of electrons using the Time Projection Chamber (TPC) and Time of Flight (TOF) will be discussed. We will report the status and updates of the measurements of electrons from beauty-hadron decays in pp collisions.

Speaker: Ms Jiyeon Kwon (Inha University)

b2e_QM2018_v7.pdf

414 Production of electrons from heavy-flavour hadron decays in proton-proton and Xe-Xe collisions with ALICE at the LHC

At the LHC energies, heavy quarks (i.e. charm and beauty) are produced in proton-proton (pp) collisions mainly via hard partonic scattering processes. They provide an essential testing ground for perturbative QCD calculations. In heavy-ion collisions, heavy quarks are produced in a shorter timescale than the quark-gluon plasma. Therefore, they experience the full collision history carrying unique information on the medium properties. On this regard, heavy-flavour measurements in pp collisions serve as a baseline for the heavy-ion measurements.
In this poster we will show the status of measurements of the production of electrons from heavy-flavour hadron decays in pp collisions at different collision energies. The nuclear modification factor ($R_{\rm AA}$) of electrons from heavy-flavour hadron decays in Xe-Xe collisions will be also discussed. The comparison with Pb-Pb data allows us to investigate the influence of different system geometry and size at similar energy densities. The analysis procedure employed for measuring the spectra of electrons from the heavy-flavour hadron decays will be discussed, including the most recent data-driven method used to subtract the large electron background component from photon conversion and Dalitz decay. Comparisons with model calculations including the interaction of heavy quarks with the hot, dense, and deconfined medium will be presented.

Speaker: Sebastian Hornung (GSI - Helmholtzzentrum fur Schwerionenforschung GmbH (DE))

QMPoster_HFE_pp_XeXe_SebastianHornung.pdf

415 Production of heavy-flavour hadron decay electrons in pp collisions at √s = 13 TeV as a function of charged-particle multiplicity with ALICE

The study of heavy flavours in pp collisions as a function of the charged particle multiplicity gives an insight into the particle production mechanisms. Moreover, the multiplicity dependence of the heavy flavour yield in pp collisions is sensitive to the large amounts of gluon radiation and the contribution of Multiple Parton Interactions (MPI) in the collisions.

In this contribution, we present the measurement of the yield of heavy-flavour hadron decay electrons at mid-rapidity ($|\eta| <$ 0.8) as a function of transverse momentum and charged particle multiplicity in pp collisions at $\sqrt{s} =$ 13 TeV. Electron identification is done within 0.5 $< p_\mathrm{T}<$ 4.5 GeV/$c$ with the Time Projection Chamber (TPC) and the Time of Flight (TOF) detectors of the ALICE apparatus. The measurement of electrons from heavy-flavour hadron decay is expressed in terms of the ratio of the yield in a particular multiplicity interval to the multiplicity integrated yield (self-normalized yield). The result is given as a function of the relative charged particle pseudorapidity density within $|\eta| <$ 1.

Speaker: Shreyasi Acharya (Variable Energy Cyclotron Centre (IN))

QM_conference_poster.pdf

416 Production of pions, kaons and protons as a function of charged particle multiplicity in pp collisions at √s = 13 TeV with ALICE at the LHC

Measurements of identified charged particle production as a function of multiplicity in pp and p-Pb collisions are important tools for understanding the similarities and differences between small and large interacting systems. The collective-like behavior observed in high multiplicity pp events is reminiscent of those observed in heavy-ion collisions. With its excellent tracking and particle identification capabilities, ALICE is an ideal instrument for the systematic study of pion, kaon and proton production from very low to high transverse momentum. In this report, the results of minimum bias as well as multiplicity-dependent transverse momentum spectra, $p_{\rm{T}}$-integrated yield ratio and $\langle p_{\rm{T}} \rangle$ of pions, kaons and protons in pp collisions at $\sqrt{s}$ = 13 TeV will be presented. These results will be compared with the lower energy results of pp, p-Pb and Pb-Pb collisions as well as the predictions of various Monte-Carlo event generators and hydrodynamic models.

Speaker: Pranjal Sarma (Gauhati University (IN))

QM_final_piKp13TeVvsMult.pdf

417 Production of pions, kaons and protons in p-Pb collisions at~$~\sqrt[]{s_{NN}}=$~8.16 TeV with ALICE at the LHC

At the end of 2016 the ALICE detector, installed at the LHC, collected p-Pb data at a center of mass energy equal to $\sqrt[]{s_\textrm{\tiny{NN}}} =$~8.16 TeV.
These data represent an important chance to test the emergence of possible initial state effects, by comparing the spectra of identified light hadrons extracted in this dataset to the ones measured in previous pp and Pb-Pb data in a wide transverse momentum range.
In this poster, the first results on transverse momentum spectra for identified $\pi$, $K$ and p at $\sqrt[]{s_\textrm{\tiny{NN}}}=$~8.16 TeV measured through the capabilities of the ALICE \textrm{ITS}, \textrm{TPC} and \textrm{TOF} systems will be presented.
This analysis has been performed at midrapidity over a wide transverse-momenta range (100~MeV/$c$~$<$~\ensuremath{p_{\rm T}}~$<$~20~GeV/$c$) for different multiplicity classes ranging from central to peripheral ones.

Speaker: Dr Silvia Pisano (INFN e Laboratori Nazionali di Frascati (IT))

418 Production of strange particles in jets and the underlying event in pp collisions at $\sqrt{s}=13$ TeV with ALICE at the LHC

The $p_{\rm T}$ dependence of the baryon-to-meson yield ratio in hadronic and nuclear collisions is sensitive to the collective expansion of the system, the partonic recombination into hadrons, the jet fragmentation and hadronization. In the region $2< p_{\rm T} < 6$ GeV/$c$, this ratio for inclusive yields is significantly enhanced at high multiplicity in small collision systems, such as pp and p-Pb collisions, relative to that at lower multiplicity. However, the origin of the enhancement still remains an open question.
In this contribution, we explore the connection between the baryon-to-meson ratio enhancement and jet production via the measurement of the $p_{\rm T}$-differential spectrum of strange and multi-strange particles (${\rm K}_{\rm S}^{0}$, $\Lambda$ and $\Xi$) in pp collisions at $\sqrt{s}=13$ TeV, both inclusively and within energetic jets. The results will set new constraints on the particle production mechanisms in jets, and will provide new insight in the understanding of the origin of flow-like correlations observed in small systems.

Speaker: Pengyao Cui (Central China Normal University CCNU (CN))

StrangenessInJet.pdf

419 Prompt and non-prompt $J/\psi$ elliptic flow in Pb+Pb collisions at 5.02 TeV with the ATLAS detector

The measurement of prompt and non-prompt $J/\psi$ in heavy-ion collisions provides a powerful tool to probe the dynamics of the hot, dense plasma formed in heavy ion collisions at the LHC. Prompt $J/\psi$ probe the effects of color screening, color recombination, and potential new phenomena. Non-prompt $J/\psi$'s serve as a proxy for $b$-quark systems produced in these collisions, and their behavior primarily reflects that of the produced $b$ quarks. The azimuthal distribution of $J/\psi$ relative to the event plane estimated with forward-going particles and their energy deposit on the calorimeters, provides complementary information to the $R_\mathrm{AA}$, offering clues about the stage at which charmonium states are formed during the system evolution, and thus providing insights on the factors affecting its production. On this poster, ATLAS will present its first measurements of the elliptic flow of prompt and non-prompt charmonia in intervals of transverse momentum, rapidity and centrality.

Speaker: Jorge Andres Lopez Lopez (Federico Santa Maria Technical University (CL))

poster_QM_2018_Jorge.pdf

420 Prompt and non-prompt J/psi production measurements in high-multiplicity proton-proton collisions at sqrt(s) = 13 TeV with ALICE at the LHC

The study of heavy-flavour hadron production as a function of the charged particle multiplicity in proton-proton (pp) collisions allows to study the interplay between hard and soft QCD processes. In particular the simultaneous comparison of open and hidden heavy-flavour multiplicity dependent measurements with theoretical models imposes tight constraints improving significantly our knowledge about the role of Multi-Parton Interactions (MPI).
The ALICE detector provides excellent capabilities to study J/$\psi$ production down to $p_{\mathrm T}$ = 0 in the central barrel ($|y|$ < 0.9), via its di-electron decay channel. In this poster we will present the newest mid-rapidity results on the J/$\psi$ yields as a function of the event multiplicity in pp collisions at $\sqrt{s}$ = 13 TeV, measuring separately the contribution of prompt and non-prompt J/$\psi$. The latter component originates from beauty hadron decays and provides the multiplicity dependence of open-beauty hadron production. The usage of high-multiplicity triggered data will allow to extend significantly the multiplicity reach for both measurements.

Speaker: Fiorella Fionda (University of Bergen (NO))

421 Prompt photon production and photon-jet correlations at the LHC

Next-to-leading order predictions matched to parton showers are compared with recent ATLAS data on inclusive photon production and CMS data on associated photon and jet production in pp and pPb collisions at different centre-of-mass energies of the LHC. We find good agreement and, as expected, considerably reduced scale uncertainties compared to previous theoretical calculations. Predictions are made for the ratio of inclusive photons over decay photons R_γ, an important quantity to evaluate the significance of additional photon sources, e.g. thermal radiation from a Quark-Gluon-Plasma, and for distributions in the parton momentum fraction in lead ions x_obs, that could be determined by ALICE, ATLAS, CMS and LHCb in ongoing analyses of photon+jet production in pPb collisions at √s_NN = 5.02 TeV. These data should have an important impact on the determination of nuclear effects such as shadowing at low x.

Speaker: Hendrik Poppenborg (Westfaelische Wilhelms-Universitaet Muenster (DE))

qm18_poppenborg.pdf

422 Prompt photon production in $p$+Pb collisions with the ATLAS detector

Electroweak bosons produced in heavy ion collisions are excellent tools to probe a variety of initial state effects on hard processes involving nuclei. They are expected to be unmodified by final state hot nuclear matter effects while being sensitive to the initial state nuclear modification of the partonic momentum structure and the energy loss of the incoming partons participating in a hard scattering. Thus, these probes are important for serving as a standard candle against which to compare the production of strongly interacting particles, such as hadron and jet production, which are sensitive to both the initial and final state. This poster presents a new measurement of prompt photon production in the recently collected high-statistics 8.16 TeV $p$+Pb collision data. Photon yields are reported over a broad kinematic range, $25 < p_\mathrm{T}^{\gamma} < 500$ GeV and $\left|\eta^\mathrm{lab}\right|<2.37$, and the production rates are compared to an extrapolated $pp$ reference based on existing $\sqrt{s}=8$ TeV $pp$ collision data. The measured spectra and nuclear modification factors are compared to theoretical calculations of initial state energy loss as well as the expectations from nuclear parton distribution functions.

Speaker: Kurt Keys Hill (University of Colorado Boulder (US))

poster_buff_kurthill.pdf

423 Protons and light nuclei in Au+Au Collisions at 1.23A GeV with HADES

As light hadrons have successfully been analysed, ongoing studies try to extend the set of identified particles towards light nuclei.

Light nuclei are expected to form at a later stage of the evolution and can probe the final freeze-out. The production of nuclei in heavy ion collisions is commonly discussed within two different scenarios: the thermal-statistical model and the coalescence model.

In 2012 the HADES experiment at GSI Helmholtzzentrum f\"ur Schwerionenforschung in Darmstadt measured Au+Au collisions at $\sqrt{s_{NN}}$ = 2.41 GeV. In this contribution, we present results on protons and light nuclei.

Speaker: Melanie Szala (Goethe University Frankfurt)

QM2018_Poster_Szala.pdf

424 Pseudorapidity dependence of anisotropic flow in Pb-Pb collisions measured with ALICE

Anisotropic flow coefficients $v_n$ are used to study the properties of the quark-gluon plasma created in heavy-ion collisions.
In this poster we will present $v_n$ measured for a wide range of pseudorapidity -$3.4 < \eta < 5$ in Pb-Pb collisions at $\sqrt{s_{NN}} = 5.02$ TeV.

These new results will be compared to measurements at lower energies as well as model calculations. The presented results help to constrain the longitudinal profile of the initial conditions and the parameters of the 3D hydrodynamical modelling of relativistic heavy-ion collisions.

Speaker: Ms Freja Thoresen (The Niels Bohr Institute)

Pseudorapidity_dependence of_anisotropic_flow_in_PbPb_collisions_measured_with_ALICE_poster_v6.pdf

425 Pythia8 is ready for heavy-ion physics

We have formulated a new model for collisions with nuclei, called Angantyr, which is now included in the Pythia8 event generator. The model is inspired by the old Fritiof model, but includes also effects of hard partonic interactions. It uses the Glauber model to calculate the number of wounded nucleons, but includes fluctuations in the NN interaction to separate absorbed and diffractively excited nucleons. The MC simulates final states without assuming a thermalized plasma. Hence, in this manner we are providing an event generator to be used to simulate events from pp to AA with the same underlying physics approach. Collective effects due to high string density are not included in the present version, but will be added in future work.

Speaker: Harsh Shah (Lund University)

QM18_harsh_shah.pdf

426 Quark / Antiquark Correlations in Heavy-Light Ion Collisions

The correlation length associated with color-charge fluctuations, known as the inverse saturation momentum, plays a fundamental role in the initial conditions of heavy-ion collisions. With state-of-the-art hydrodynamic codes tailored for the finite-baryon-density physics of the Beam Energy Scan, it is interesting to study the analogous role of correlations between quarks and antiquarks. While recent work has studied the quantum statistical effects of Bose enhancement for gluons and Pauli blocking for quarks, we will present here new results on the quark / quark, quark / antiquark, and antiquark / antiquark correlation functions in asymmetric “heavy-light” ion collisions. The correlation function is dominated by qualitatively different mechanisms at different length scales, and quantum entanglement between two sets of quark / antiquark pairs leads to highly nontrivial correlations. The results of this work can be used to construct initial state models for heavy-ion collisions which incorporate nontrivial spatial fluctuations of quarks and antiquarks.

Speaker: Matthew Sievert (Los Alamos National Laboratory)

Baryon_Poster.pdf

427 Quarkonium hadroproduction and photoproduction in quark-gluon plasma and strong electromagnetic fields at RHIC and LHC

We study the charmonium coherent photoproduction and hadroproduction consistently with modifications from both cold and hot nuclear matters. The strong electromagnetic fields from fast moving nucleus interact with the other target nucleus, producing abundant charmonium in the extremely low transverse momentum region $p_T<0.1$ GeV/c, based on the process $\gamma +A\rightarrow J/\psi +A$. This results in significant enhancement of $J/\psi$ nuclear modification factor in semi-central and peripheral collisions. In the middle $p_T$ region such as $p_T<3\sim 5$ GeV/c, $J/\psi$ final yield is dominated by the combination process of single charm and anti-charm quarks moving in the deconfined matter, $c+\bar c\rightarrow J/\psi +g$. In the higher $p_T$ region, $J/\psi$ production are mainly from parton initial hard scatterings at the beginning of nucleus-nucleus collisions and decay of B hadrons. We include all of these production mechanisms and explain well the experimental data from ALICE and STAR in different transverse momentum regions at LHC and RHIC energies.

Speaker: Dr Baoyi Chen (Goethe University)

QM_Baoyi__charmonium.pdf

428 Quarkonium properties at T>0 from lattice NRQCD

I will present results on the T>0 charmonium and bottomonium
spectral functions, based on high statistics lattice NRQCD calculations
of the corresponding correlators performed in 2016-2018 (full
statistics for $48^3 \times 12$ lattices and new results on $64^3 \times 16$ lattice).

We extract the quarkonium in-medium spectral functions based on two
complementary strategies: 1. A direct Bayesian reconstruction via
a novel variant of the BR method. This remedies the ringing
problem inherent in the previous analysis. 2. Correlator model fits with
adapted frequency binning, which incorporate the combined insight
from potential based computations and the T=0 spectral functions.

We find that the quarkonium masses are shifted to smaller values
with increasing temperatures and also provide upper limits
on the thermal width. We compare the temperature
dependence of the correlation functions obtained
in lattice NRQCD with the potential model.

Speaker: Alexander Rothkopf (Heidelberg University)

Poster_Petreczky_Quarkonium_FINAL.pdf

429 Readout of the MAPS vertex detector at sPHENIX

The MVTX detector will serve as the micro-vertex tracking detector of the sPHENIX experiment at RHIC. It is an extremely precise silicon pixel vertex detector, with excellent displaced secondary vertex detecting capabilities. The MVTX will enable key measurements of heavy-flavor-tagged jets and B-mesons in heavy ion collisions. The detector is based on the latest generation of Monolithic Active Pixel Sensors (MAPS) technology, developed for the ALICE collaboration at CERN.

The readout chain is comprised of three parts: a sensor stave assembly, a RU (Readout Unit) board, and a FELIX (Front End LInk eXchange) board. The stave assembly consists of 9 ALPIDE (ALice PIxel DEtector) sensor chips, which will send its data on 9 gigabit links over a FireFly cable to an RU board. The RU board primarily consists of two FPGA’s, one for reading the stave data and sending data using CERNs rad-hard GBT links over fiber to the FELIX board and a second FPGA which is used for scrubbing (SEU detection). The FELIX board primarily consists of an FPGA that reads out the the data over the fiber link and sends its data to a 16 lane PCIe interface, placing the data to disk.

We will present the R&D efforts and performance achievements for the three parts of the Readout system mentioned above.

Speaker: Dr Sanghoon Lim (LANL)

QM18_poster_MVTX_readout_v0.pdf

430 Recent results on cumulant ratios at nonzero temperature and density from lattice QCD

We present recent results on the distributions of conserved charge fluctuations. In particular, we discuss ratios of the shape parameters mean, variance, skewness and kurtosis of the net baryon- number, electric charge and strangeness distributions. For the net baryon-number fluctuations we find – using a next-to-leading order Taylor expansion – that qualitative features of these ratios closely resemble the corresponding experimentally measured cumulants ratios of net proton-number fluctuations for beam energies down to collision energies of 19.6 GeV. We show that the observed difference in cumulant ratios for the mean net baryon-number and the normalized skewness arises naturally in QCD thermodynamics. Moreover, we establish a close relation between skewness and kurtosis ratios, at small values of the baryon chemical potential. In the case of electric charge and strangeness fluctuations we show that these ratios are sensitive to the presence of multiple charged particles.
The calculations are based on lattice QCD simulations with physical quark masses and a highly improved staggered quark (HISQ) action. The lattice size is $N_\sigma^3\times N_\tau$, with an aspect ratio $N_\sigma/N_\tau=4$ and three different lattice spacings, corresponding to the number of temporal sites $N_\tau=8, 12$ and $16$. Continuum extrapolations have been performed for most of our observables.

1. A. Bazavov et al. [HotQCD Collaboration], “Skewness and kurtosis of net baryon-number distributions at small values of the baryon chemical potential,” Phys. Rev. D 96 (2017), 074510 [arXiv:1708.04897].
2. A. Bazavov et al., “The QCD Equation of State to $\mathcal{O}(\mu_B^6)$ from Lattice QCD,” Phys. Rev. D 95 (2017), 054504 [arXiv:1701.04325].

Speaker: Christian Schmidt (University of Bielefeld)

poster_schmidt.pdf

431 Reconstruction of Weak Decays in Au+Au Collisions at 1.23A GeV with HADES

We use a high statistic data sample of $7.3 \times 10^{9}$ recorded
Au(1.23A GeV)+Au events to investigate $\Lambda^{0}$ baryon and $K^{0}_{S}$ meson
production below their free nucleon nucleon threshold. For the first
time these hadrons have been investigated using a neural network
to identify their weak decay topologys inside HADES. We highlight
details of the analysis procedure such as event selection, particle
identification and topological cuts on the decay kinematic before
presenting and discussing the transverse energy spectra as well as
production yields and their rapidity dependence. The results are
confronted with phenomenological models.
This work has been supported by BMBF (05P15RFFCA), GSI and
HIC for FAIR.

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

QM2018_SimonSpies.pdf

432 Relativistic hydrodynamics of Polarized Matter

The observation of hadronic polarization in the reaction plane in heavy ion collisions has heightened interest in the behavior of relativistic fluids where microscopic degrees of freedom carry spin.
We use Lagrangian Effective Field theory techniques to understand the ideal hydrodynamic limit for such systems. After discussing the relation between this limit, transport theory, and ideal hydrodynamics we derive the equations of motion for a polarized fluid. We show that this system will generally require non-dissipative dynamics at higher order in gradient than first order, leading to breakdown of stability and causality. Thus, such a system necessitates relaxation-type dynamics already in the ideal fluid limit, unlike unpolarized hydrodynamics where the ideal limit is known to be causal.
We discuss this result in light of the conjectured lower limit of viscosity for strongly coupled fluids, and comment on phenomenological applications.
Based on
https://arxiv.org/abs/1701.08263
https://arxiv.org/abs/1703.03079
(both published, PRD) as well as ongoing work.

Speaker: Giorgio Torrieri (IFGW, Unicamp)

posterv2.4.pdf

433 Relaxation Time for the Chiral Vortical Effect and Spin Polarization in Strongly Coupled Plasma

Anomalous transport phenomena arising from chiral anomaly such as the Chiral Magnetic Effect have recently attracted much attention. One such phenomenon, the Chiral Vortical Effect, that is an induced current along fluid vorticity, is somewhat special because it is related to chiral anomaly on one hand, while on the other hand its microscopic origin is the spin polarization of chiral quarks in the fluid vorticity, whose physics is more general and applicable even for massive spinful particles such as Lambda baryon. In theoretical understanding of recently measured Lambda polarization in off-central heavy-ion collisions at RHIC, it is vitally important to know the dynamical time scale of this spin polarization, that is, the relaxation time it takes to achieve the equilibrium with Lambda spins polarized in a finite fluid vorticity. Therefore, by studying the relaxation time of the Chiral Vortical Effect in massless chiral limit, we can get a useful proxy for this time scale for Lambda spin polarization.
We first derive the correct Kubo formula for the relaxation time of the Chiral Vortical Effect from the energy-momentum and current two point functions, pointing out that some of the previous claims for a zero relaxation time of the Chiral Vortical Effect is due to an incorrect identification of the Kubo formula for the relaxation time of the Chiral Vortical Effect. Using our Kubo formula, we compute the correct and finite relaxation time of the Chiral Vortical Effect for the first time in strongly coupled plasma using the AdS/CFT correspondence.

Speaker: Shiyong Li (University of Illinois at Chicago)

QMposter20180511v2.pdf

QMposter20180511v2.pptx

434 Resolution Effects in the Hybrid Strong/Weak Coupling Model

Within a hybrid strong/weak coupling model of jet quenching, plasma produced in a heavy ion collision cannot resolve the substructure of a collimated parton shower propagating through it with arbitrarily fine spatial resolution. We introduce a screening length parameter, $L_{res}$, proportional to the inverse of the local temperature in the plasma, estimating a range for the value of the proportionality constant via comparing weakly coupled QCD calculations and holographic calculations appropriate in strongly coupled plasma. When a parton in a jet splits, its two offspring are initially unresolved and suffer the energy loss of the original parton until they are separated by $L_{res}$. This delays the quenching of partons with intermediate energy, resulting in the survival of more hadrons in the final state with $p_T$ in the several GeV range. Introducing a nonzero $L_{res}$ results in modifications to the jet shapes and jet fragmentations functions, as it makes it more probable for particles carrying a small fraction of the jet energy at larger angles from the jet axis to survive their passage through the quark-gluon plasma. These effects are small in magnitude, which we confirm via checking for effects on missing-$p_T$ observables.

Speaker: Zachary Hulcher (Cambridge University)

QM Hulcher 2018.pdf

435 Response studies of the CME-sensitive sine observable to heavy ion backgrounds

A new sine observable, $R(\Delta s)$, has been proposed [1] to measure the Chiral Magnetic Effect (CME) in heavy ion collisions, where $\Delta s$ is the $\langle\sin\phi\rangle$ difference between positive and negative charges ($\phi$ is the particle azimuth) and $R(\Delta s)$ is the ratio of the out-of-plane to in-plane $\Delta s$ distributions. Studies with A Multi-Phase Transport (AMPT) and Anomalous Viscous Fluid Dynamics (AVFD) models show concave R($\Delta s$) distributions for CME signals and convex ones for typical resonance backgrounds [1]. A recent hydrodynamic study, however, indicates concave shapes for backgrounds as well [2]. Preliminary STAR data, on the other hand, reveal concave $R(\Delta s)$ distributions in 200 GeV Au+Au collisions.

To better understand these results, we present a systematic study of the $v_{2}$ and $p_{T}$ dependences of resonance backgrounds by toy-model simulations, based on the toy model used in our previous study [3]. The resonance $v_{2}$ introduces different numbers of decay $\pi^+\pi^-$ pairs in the in-plane and out-of-plane directions. The resonance $p_{T}$ affects the opening angle of the decay $\pi^+\pi^-$ pair. Low $p_{T}$ resonances decay into large opening-angle pairs, and result in more ``back-to-back'' pairs out-of-plane because of the more in-plane resonances, mimicking a CME charge separation signal perpendicular to the reaction plane, or a concave $R(\Delta s)$. High $p_{T}$ resonances, on the other hand, decay into small opening-angle pairs, and result in a background behavior of convex $R(\Delta s)$. With this toy-model insight, we further investigate the responses of the $R(\Delta s)$ observable to AMPT backgrounds and AVFD CME signals,and the possible implications of the preliminary STAR data.

[1] N. Magdy, S. Shi, J. Liao, N. Ajitanand and R. A. Lacey, arXiv:1710.01717

[2] P. Bozek, arXiv:1711.02563

[3] F. Wang, J. Zhao, Phys. Rev. C95, 051901 (R) (2017)

Speaker: Yicheng Feng (Purdue University)

436 Results on femtoscopy from hydrodinamics in pp collisions at $\sqrt{{s}}$ = 7 TeV

The hydrodynamical model has a long history in high-energy physics,
being an essential tool for describing the collective behaviour of
the matter produced in relativistic heavy-ion collisions at RHIC and
LHC. Recently, experimental results have shown evidence of a similar
collective behavior in small systems (pp and pPb collisions).

Bose-Einstein correlation or femtoscopy, are a powerful probe of the
space-time geometry of the particle emitting source. In this work,
a study of such correlations is perform using the hydrodynamical model
in 2+1 dimensions. Both the ideal and the viscous (shear and bulk)
fluid cases are considered. An equation of state inspired in lattice
QCD results, with a crossover phase transition between the quark-gluon
plasma and the hadronic phase, is employed. The results are compared
with experimental data on pp collisions at $\sqrt{s}$ = 7 TeV.

Speaker: Dener De Souza Lemos (UNESP - Universidade Estadual Paulista (BR))

D_Lemos.pdf

437 Scalar product and event plane methods for measurements of azimuthal anisotropy in Pb+Pb and Xe+Xe collisions with the ATLAS detector at the LHC

Measurements of the azimuthal anisotropy of charged particles in heavy-ion collisions are sensitive to the detailed properties of the quark-gluon plasma, in particular its dependence on initial conditions, transport coefficients and time evolution. The presented measurements are based on 0.49 n$\mathrm{b}^{-1}$ of Pb+Pb data collected by the ATLAS detector in 2015 with center-of-mass energy $\sqrt{s_{NN}}=5.02$ TeV. The elliptic flow and higher-order Fourier coefficients ($v_{2}$ - $v_{7}$) are presented in a wide range of transverse momenta ($p_\mathrm{T}<60$ GeV), pseudorapidity ($|\eta|<2.5$) and 0-80% collision centrality. The collected minimum-bias sample is enhanced by triggers for "ultra-central" collisions, providing an opportunity to perform precise measurements of flow harmonics in the fluctuation-dominated regime. The magnitude of azimuthal anisotropy is estimated by measuring the angular correlations of produced particles using both the scalar product and event plane methods. To suppress non-flow, $v_{n}$ harmonics are calculated by correlating two flow vectors estimated in two different detectors separated in pseudorapidity (the forward calorimeter $3.2<|\eta|<4.8$, or the inner detector $|\eta|<2.5$), and in the opposite hemispheres. The obtained results are compared to the $v_{n}(p_\mathrm{T})$ values at measured in $\sqrt{s_{NN}}=2.76$ TeV Pb+Pb collisions and recent $\sqrt{s_{NN}}=5.44$ TeV Xe+Xe collisions as well as to predictions of hydrodynamical models.

Speaker: Klaudia Burka (Polish Academy of Sciences (PL))

KBurka-QMposter.pdf

438 Search for a Lambda nn bound state in Pb-Pb collisions with ALICE at the LHC

The extreme energy densities reached at LHC lead to the production of a significant amount of baryons and strangeness. Such a regime allows for an increased production of potentially existing exotic QCD bound states containing nuclei and strange hadrons. An interesting measurement for the phenomenology of the nuclear interaction is the presence of a neutral bound state constituted by one Λ and two neutrons. The excellent particle identification, tracking and vertexing performance of the ALICE experiment allow for the search of this exotic bound state in the decay channel Λnn → πt in Pb-Pb collisions. In order to improve the detection of this state within a big combinatorial background, the extraction of the signal is performed by means of a multivariate approach with the TMVA (Toolkit for Multivariate Data Analysis with ROOT). So far the indication for the existence of the Λnn state was reported only by one Collaboration, so the observation by ALICE would crucially contribute to the study of such an exotic state.

Speaker: Annalisa Mastroserio (Universita e INFN, Bari (IT))

AnM_posterqm2018.pdf

439 Search for gluon saturation at small Bjorken-x with the LHCb detector

A new state of matter, where gluons have overlapping wave functions, has
been in the minds of particle and nuclear physicists for decades. This
gluon saturated state could explain several recent observations such as
particle production and collectivity observed in p+p, p+A and A+A
collisions at RHIC and LHC.

The LHCb experiment is a forward spectrometer with vertexing, tracking,
$p$, $K$, $pi$, $e$, $\mu$ identification and calorimetry in the
pseudorapidity region $2< \eta <5$. LHCb is therefore well suited to
study the gluon density of hadrons in at small Bjorken-x values ($x \sim 10^{-6}-10^{-5}$), down to two orders of magnitude smaller than HERA.

The status of the analysis efforts aimed at finding the gluon saturation
scale at LHCb using isolated photon yields and their correlations with
hadrons and jets will be shown. In addition, the concept and R&D efforts
of a new particle tracker inside the LHCb magnet to improve measurements
of small $Q^2$ processes, where gluon saturation is expected, will be
presented.

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

QM_poster-gamma_hadron.pdf

440 Searches for pion condensation in pp and Xe-Xe collisions at the LHC with the ALICE Inner Tracking System

Most hydrodynamical models have problems with the correct prediction of very low transverse-momentum ($p_{\mathrm{T}}$) spectra of pions. The problem may be solved by assuming that the matter at LHC energies is produced out of chemical equilibrium. The chemical non-equilibrium model predicts that the pion abundances are characterized by the non-zero value of the chemical potential which is very close to the critical value for the Bose-Einstein condensation. The crucial point is the measurement of pions at very low $p_{\mathrm{T}}$ (< 200 MeV/$\textit{c}$), as the onset of pion condensation would manifest itself as an excess in the low $p_{\mathrm{T}}$ pion yield while the spectra of kaons and protons remain unaltered.
In October 2017, the ALICE Collaboration at the CERN Large Hadron Collider collected for the first time data in Xe-Xe collisions at $\sqrt{s_{\rm NN}}$ = 5.44 TeV with low magnetic field (B = 0.2 T). Thanks to this, the pion spectra can be measured down to 100 MeV/$\textit{c}$ and below with the Inner Tracking System (ITS), allowing the search for pion condensation effects.
The search for an enhancement of pions at very low $p_{\mathrm{T}}$ is carried out also in very high multiplicity pp events.
In this contribution we compare the performance of the ALICE ITS with low and nominal magnetic field and we present the first results on the measurement of pion, kaon and proton spectra down to the lowest $p_{\mathrm{T}}$ possible with the ALICE detector.

Speaker: Ivan Ravasenga (Politecnico di Torino (IT))

IRavasenga_QM2018_poster_v3.pdf

441 SiPM performance characterization and radiation hardness tests for sPHENIX

The electromagnetic (EMCal) and hadronic (HCal) calorimeters for the sPHENIX experiment will use ~120,000 Silicon Photo-Multipliers (SiPMs) as optical sensors (Hamamatsu S12572-33-015P). SiPMs are small, immune to magnetic field, low bias voltage, high gain devices, but are also sensitive to radiation damage, particularly to neutrons. Moreover, one EMCal tower will be read out by four SiPMs, whose performance characteristics, including gain versus operating voltage have to be closely matched. We have performed irradiation tests with gamma rays up to 1 Mrad and neutron exposures up to $10^{12}{\mbox{cm}}^{-2}$, with a continuous neutron spectrum up to 17 MeV, and studied the dark current, breakdown voltage and gain curve as a function of integrated dosage. We also designed and constructed an SiPM testing device that measures the breakdown voltage and gain curve with the SPS (single photon spectrum) method. This testing device will serve as the prototype for three large scale devices that will be used to characterize and group all ~120k SiPMs for the sPHENIX EMCal and HCal detector before final assembly. In this poster we will report on the results of our irradiation tests and the performance of the prototype test device used to characterize the 1800 SiPMs being used for the sPHENIX preproduction calorimeter prototypes being assembled in 2018.

Speaker: Dr Balazs Ujvari (Debrecen University)

qm18sipm.pdf

442 Soft-gluon approximation in calculating radiative energy loss of high $p_T$ particles - is it well-founded?

The soft-gluon approximation, which implies that radiated gluon carries away a small fraction of initial parton's energy, is a commonly used assumption in calculating radiative energy loss of high momentum partons traversing the dense QCD medium, created in ultra-relativistic heavy ion collisions at RHIC and LHC. While soft-gluon approximation is convenient, doubts have been raised over its validity, especially since different theoretical approaches reported significant radiative energy loss of high $p_T$ partons, which implies that this approximation is not applicable in such calculations.

To address this issue, we relaxed the soft-gluon approximation within DGLV formalism [1], and discuss generalizing this relaxation in the dynamical QCD medium. Although the obtained results are quite distinct compared to the soft-gluon case, numerically both cases lead to nearly overlapping predictions for the first order in opacity fractional energy loss. The fractional number of radiated gluons is also barely affected. The effect on these two variables runs in opposite directions, which when combined results in negligible suppression change. Therefore, we unexpectedly conclude that soft-gluon approximation works surprisingly well in energy loss calculations, and that there is no need to go beyond the soft-gluon approximation in energy loss based models of parton suppression.

[1] B. Blagojevic, M. Djordjevic and M. Djordjevic, to be submitted (2017).

Speaker: Bojana Blagojevic (Institute of Physics Belgrade, University of Belgrade)

QM2018_Poster_BojanaBlagojevic.pdf

443 Spectator Tagging for the EIC and High Luminosity LHC

At the Electron Ion Collider Deep Inelastic Scattering on deuterons combined with proton and tagging would complete control of the initial state and allow detailed measurements of the neutron and proton parton functions and their spin dependence. At the LHC proton tagging of diffractive, pp and pA events allow for complete control of the kinematics of the initial state. Similarly neutron tagging of incoherent vector meson production allows the photon direction to be determined and so allows for the measurement of low x gluon distribution functions over a range of Bjorken X. Both colliders impose severe constraints on the resolution, speed and radiation hardness of the forward systems. This talk will discuss possible implementations of such detectors and map out the R&D needed to enable the physics measurements described above.

Speaker: Prof. Michael Murray (University of Kansas)

444 Spectral function from real-time lattice gauge simulations

We study spectral properties of a highly occupied non-Abelian plasma, which is expected to be created in the weak-coupling picture during the initial stages after a heavy-ion collision. The spectral function of this far-from-equilibrium plasma is measured by employing linear response theory to classical-statistical lattice simulations. We obtain the dispersion relation of the quasi-particles, their effective mass as well as the form of the spectral function in frequency space. Our results are consistent with hard thermal loop effective theory where expected but can be extended beyond the regime of validity of the latter.

Speaker: Kirill Boguslavski (University of Jyvaskyla (FI))

VeniceQM2018_Boguslavski.pdf

445 sPHENIX INTT Silicon Intermediate Tracker R&D status

The sPHENIX experiment will collect high statistics proton-proton, proton-nucleus and nucleus-nucleus data at RHIC, starting in the early 2020's. sPHENIX will investigate jet modification, upsilon suppression and open heavy flavor production to probe the nature of the strongly-coupled Quark Gluon Plasma, and will perform a broad range of cold QCD studies.

The Silicon Intermediate Tracker (INTT) is one of the key detectors in the sPHENIX tracking system and plays an important role for DCA measurements, pile-up event separation, as well as charged particle tracking. The INTT, consisting of 4 layers of Silicon strip detectors, covers the radial space at 6-12cm away from the interaction point. Extensive efforts for INTT development are being made and a beam test is scheduled at FNAL in March 2018 to characterize the performance of INTT prototype modules.
We will report the latest R&D status, including the beam test results, in this presentation.

Speaker: Yorito Yamaguchi (RIKEN)

INTT_QM18poster.pdf

446 Spin-offs from the rapid, volume hadronization of QGP applied at other scales for transitions in extreme hot and dense matter

By now there is ample experimental and theoretical evidence that in high energy heavy ion reactions the Quark Gluon Plasma hadronizes in a very rapid transition, where most of the hadronization hypersurface or layer has a time-like normal. Thus the neighboring points of this surface are not causally connected to each other, and so collective pressure driven instabilities cannot develop. This process is naturally described by relativistic fluid dynamics.

Rapid, simultaneous phase transitions or ignition in most of the volume of the material are important and vital problems in many fields of research and technology. Present laser and nano technology make radiation dominated, relativistic, rapid events possible at larger scales. This enables experimental and theoretical studies of rapid, volume transitions and phase transitions for extreme hot and dense matter.

One example for pico second, laser pulse induced, simultaneous ignition for pellet fusion is presented. Methods taken from nano-plasmonics, will be shown to enable us to achieve this simultaneous ignition, with moderate compression and enhanced light absorption. Consequently, mechanical, pressure driven Rayleigh-Taylor instabilities, preventing stable volume ignition up to now, will not have time to develop and whole volume ignition can be achieved.

Speaker: Laszlo Pal Csernai (University of Bergen)

QuarkMatterposter_2018-May.pdf

447 STAR Measurements of Elliptic Flow in Small Collision Systems

The coefficient of the second harmonic in azimuthal anisotropy ($v_2$) of produced particles gives insight to bulk properties of the medium being created in high-energy heavy-ion collisions. These measurements have provided important evidence of the partonic collective motion in the quark-gluon plasma (QGP). In recent years, the study of collective motion in small systems has gained increased attention. These studies aim to answer the questions of how small a QGP droplet can be and what is the boundary between a confined and deconfined medium. However, non-flow correlations, especially due to jets and di-jets, can influence the observed flow and may tend to dominate in small systems. Therefore, special care has to be taken to differentiate collectivity from non-flow contributions.

In this poster, we present the STAR measurements of charged-hadron elliptic flow, $v_2$, in p+Au collisions at $\sqrt{s_{NN}} = 200$ GeV, and in d+Au collisions at 200, 62.4, 39 and 19.6 GeV. Data analysis is done with the event plane method, and with 2-particle and 4-particle cumulants. The results will be shown as a function of multiplicity which provides control of the system size. This will be compared with peripheral Au+Au collisions with similar multiplicities at the same center of mass energies to determine whether or where the onset of the QGP exists in these small systems.

Speaker: Ms Maria Sergeeva (UCLA)

very_last_ver2.pdf

448 Strange and multi-strange particle production in pp collisions at √s = 13 TeV with ALICE at the LHC

Strangeness production plays a crucial role in the understanding of the formation and the evolution of a fireball created in heavy-ion collisions. To better understand the effects of the collectivity and their interplay with the particle production mechanisms it is also necessary to study pp and p–Pb collisions. We report the measurements of the production of KS0 mesons and Λ, Ξ and Ω hyperons with the ALICE detector at the LHC energy √s = 13 TeV for minimum bias pp collisions. The results include Λ∕KS0 spectra ratio, pT-differential yields, ⟨pT⟩ and particle yield ratios compared to the measurements at lower energies. The results showcase the excellent tracking capabilities of the ALICE detector and of the particle identification methods using the topology of weakly decaying hadrons and serve as the support for the multiplicity dependent measurements.

Speaker: Dr Peter Kalinak (Slovak Academy of Sciences (SK))

StrangenessProd13TeVppMinBias_v4.pdf

449 Strangeness production at SIS energies

The production of strange particles in heavy-ion collisions is enhanced compared to elementary reactions with particularly interesting results on the $\phi$ meson production close to the threshold by the HADES collaboration at GSI-SIS energies. In this talk, SMASH (Simulating Many Accelerated Strongly-interacting Hadrons), a new hadronic transport approach designed to describe the non-equilibrium evolution of heavy-ion collisions, is applied to investigate the production of strange particles. Two different mechanisms are discussed: one based on resonances and another one using forced canonical thermalization. The resonance framework is constrained by experimental data from elementary collisions and can describe strangeness production in small systems. To describe large systems, in-medium effects may be important.

Speaker: Mr Vinzent Steinberg (Frankfurt Institute for Advanced Studies)

poster.pdf

450 Strangeness Production in U+U Collisions at STAR

Strange quark production in high-energy heavy-ion collisions is a good tool in studying the properties of the deconfined phase of quarks and gluons. It is suggested that the dominant process for the production of strange quarks in the quark gluon plasma is gluonic fusion. Chemical equilibration of strange quarks, formed in such a medium, happens faster than would be the situation in hadronic scenario [1]. At similar colliding energies, U+U collisions are expected to have larger energy density [2] and higher number of produced particles than in the case of Au+Au or Pb+Pb collisions. This makes U+U system to be a unique platform for testing various observables.

We will present transverse momentum spectra of $K_s^{0}$, $\Lambda$($\bar{\Lambda}$), $\Xi$($\bar{\Xi}$) and $\Omega$($\bar{\Omega}$) in U+U collisions at $\sqrt{s_{NN}}$ = 193 GeV in the STAR experiment at RHIC. These strange particles are reconstructed from their weak decay topology via dominant hadronic decay modes using the Time Projection Chamber (TPC) detector of STAR. We will also show a comparison of the properties of these particles with PDG values and other measurements viz., particle ratios, nuclear medium effect etc. Physics implications of these results will be discussed along comparison with results from Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV.

References
[1] P. Koch, B.B. Mueller and J. Rafelski, Phys. Rep.142, 167 (1986).
[2] D. Kikola, G. Odyniec and R. Vogt, Phys. Rev. C84, 054907 (2011).

Speaker: Srikanta Tripathy (Institute Of Physics, Bhubaneswar)

QM18poster_srikanta_v14.pdf

451 Studies of $\Lambda_{\rm c}^{+}\to p \rm K^{0}_{\rm S}$ in p-Pb collisions with the ALICE experiment at the LHC

The ALICE (A Large Ion Collider Experiment) experiment at CERN is mainly aimed to study strongly-interacting matter under extreme conditions of temperature and energy density and, in particular, to verify the QCD predictions about the existence of a phase transition of the hadronic matter to the Quark-Gluon Plasma (QGP).
Heavy quarks (charm and beauty) are a powerful tool to study the properties of the QGP. Indeed they are formed during the early stages of the collisions via hard scattering of high-energy partons, on a time scale generally shorter than the QGP thermalisation time. So they can traverse the QCD medium, interact with its constituents and experience the whole evolution of the medium.
The $\Lambda_{c}^{+}$\$\rm D^{0}$ ratio is sensitive to hadronisation mechanisms and it will offer a unique probe of the role of coalescence and predicted existence of diquark states in the QGP.
Measurements of charmed-baryon production in small system (pp and p-Pb) collisions are a fundamental reference for measurements in Pb-Pb collisions and allow studies of possible modifications of the production due to cold nuclear matter effects.
Moreover, the study of charm production as a function of the multiplicity of charged particles produced in the collision can give insight into multi-parton interactions and into the interplay between hard and soft processes.
The recent results for $\Lambda_{c}^{+}$ baryons reconstructed via their hadronic decay $\Lambda_{\rm c}^{+}\to p \rm K^{0}_{\rm S}$ at mid-rapidity in p-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV will be presented.
The analysis takes advantage of the high precision tracking, good vertexing capabilities and excellent particle identification offered by the ALICE detector.

Speaker: Dr Elisa Meninno (Universita e INFN, Salerno (IT))

Poster_EMeninno_v6.pdf

452 Studies of event and jet shape in high multiplicity e+e- collisions using archived data from the ALEPH detector at LEP

Studies of thrust distributions and jet shapes in $e^+ e^-$ collisions using $730 ~pb^{-1}$ of data collected between 91 and 209 GeV with the ALEPH detector at LEP are presented. The event and jet shapes are studied for the first time with both tracker and the calorimeters in bins of the event charged particle multiplicity or event activity in order to reveal the possible modification of those observables in the high particle density environment. The results from the archived ALEPH data are compared to predictions from various event generators which were tuned to describe the inclusive event shape data at LEP, as well as theoretical calculations.

Speaker: Anthony Badea (Massachusetts Inst. of Technology (US))

PosterQM18vFINAL.pdf

453 Study of nuclear effects of charged hadron production at forward and backward rapidity in $p$+Al, $p$+Au, and $^3$He+Au collisions at $\sqrt{s_{NN}}$=200 GeV

Study of hadron production in $p$+A collisions is useful to study of nuclear effects of intrinsic nucleus with minimized hot nuclear matter effects. Early results in central $d$+Au collisions showed that both light and heavy hadron production is suppressed at forward rapidity ($d$-direction), whereas an enhancement is observed at backward rapidity (Au-direction). Thanks to the flexibility of RHIC, we can do a comprehensive study such as dependencies on size of projectile ($p$/$d$/$^3$He+Au) or target ($p$+Au/Al). PHENIX muon arm ($1.2<|\eta|<2.4$) has a capability to measure unidentified charged hadrons (mostly pion and kaon), and FVTX can provide precise measurements of $p_T$ and $\eta$ before particles suffering from multiple scatterings inside absorber material as well as reject secondary particles produced inside the absorber. In this presentation, we will present results of nuclear modification of charged hadron production at forward and backward rapidity in various centrality bins of $p$+Al, $p$+Au, and $^3$He+Au collisions at $\sqrt{s_{NN}}$=200 GeV.

Speaker: Mr Sang Hoon Lim

QM18_poster_shlim.pdf

454 Study of Quarkonia Production in proton+proton collisions at the LHC and the Role of Multiple Partonic Interaction

In high multiplicity p+p collisions, the Underlying Event observable is of great interest to the scientific community. The Multiple Partonic Interaction (MPI) is one of them, where several inelastic interactions at partonic level occur in a single p+p collision. In general, MPI plays an important role to produce light quarks and gluons. But it is observed that it can also contribute to produce heavy flavor particles like charmonia, when the interaction occurs in a harder scale. This leads to a strong dependence of J/ψ production with charged particle multiplicity. ALICE experiment has observed a monotonic increase of J/ψ with charged particle multiplicity in p+p collisions at √s = 7, 13 TeV in dimuon as well as dielectron channels. But, till now the measurements are not available for all the LHC energies. This forbids one to infer about the energy dependence role of MPI on J/ψ production.

In our current study, we have made an effort to understand the role of MPI on multiplicity and energy dependence production of J/ψ using perturbative Quantum Chromodynamics (pQCD) inspired model, PYTHIA8 at different LHC energies of √s = 0.9, 2.76, 5.02, 7 and 13 TeV. J/ψ are reconstructed via dimuon channel at forward rapidities (2.5 < y < 4.0) and the charged particle multiplicity is measured at midrapidity (|y| < 1.0). The effect of Color Reconnection (CR) on the production of J/ψ at the LHC energies at different multiplicity bins is studied. The multiplicity ratio of higher state of charmonia, to J/ψ, i.e. ψ(2S)/J/ψ will be presented as a function of multiplicity at all the LHC energies. We observe the dominance of CR and MPI effects towards high multiplicity events at the LHC energies, showing a threshold of Nch > 20. The present study will help in understanding the charmonia production in p+p collisions at the LHC energies.

Speaker: Raghunath Sahoo (Indian Institute of Technology Indore (IN))

QM_Poster-RNS.pdf

455 Study of Thermodynamic and Transport Properties of Strongly Interacting Matter in a Color String Percolation Approach at RHIC energies

The phase transition of a strongly interacting matter from hadron to a quark-gluon plasma state have received considerable interest. In the color string percolation phenomenology the interactions between the strings occur in the initial stage of the collisions. This frame-work naturally predicts the reduction in the charged particle multiplicity and the enhancement of the transverse momentum with respect to the value expected from the number of independent strings. The initial temperature and energy density are obtained from the data via the color reduction factor $F(\xi)$ and the associated string density parameter $\xi$. The shear viscosity to entropy density ratio($\eta/s$), trace anomaly($\Delta$) ,the squared speed of sound ($C_{S}^{2}$), entropy density, bulk viscosity to entropy density ratio($\zeta/s$) are extracted using Color String Percolation Model (CSPM) for STAR data at various RHIC energies from $\sqrt{s_{NN}}$ = 7.7 to 200 GeV. Results are in agreement with the lattice QCD calculations for (2+1) flavour. The initial temperatures obtained by CSPM are compared with various hadronization and chemical freeze-out temperatures. This analysis shows that the deconfinement to confinement transition possibly takes place between $\sqrt{s_{NN}}$ = 11.5 and 19.6 GeV.

Speaker: Swatantra Tiwari (Indian Institute of Technology Indore, Indore)

456 Study of two particle correlations with photon and pion triggers in pp collisions at 13 TeV with ALICE

Two-particle correlations with high-pT triggers allow the study of the hard scat- tering phenomena like soft QCD radiation, angular ordering and jet fragmentation in the low and intermediate pT regions where full jet reconstruction is challenging. An analysis of data taken during LHC Run II by ALICE will be presented for using π0 and isolated photon triggers. The data used is collected by the ALICE detectors using a trigger based on calorimeter information. Trigger performance using EMCal and DCal will be discussed. A selection based on shower shape and isolation methods is used to identify π0 and direct photon triggers, with the latter ones originating from hard parton scatterings in the nucleus-nucleus. In leading order these are annihilation from Comp- ton scattering and Annihilation in the hard processes happened in the nucleus-nucleus collisions. The selected isolated photons satisfying the criteria will reduce background photons from meson decays and fragmentations and therefore enhance the direct pho- ton triggers. In this contribution, azimuthal correlations between trigger and charged particles will be studied and per-trigger yield will be extracted from these correlations.

Speaker: Ran Xu (Central China Normal University CCNU (CN))

IsoPhotonPoster_QM2018_v16.pdf

457 Suppression of charmonia states in Pb+Pb collisions at 5.02 TeV with the ATLAS detector

The suppression of heavy quarkonia states in heavy-ion collisions is a phenomenon understood as a consequence of QGP formation in the hot, dense system produced in high-energy heavy ion collisions. A full assessment of the physics scenario requires a detailed study of effects present in Pb+Pb, in comparison to $pp$ collisions. Using Pb+Pb data collected in 2015 at the LHC by the ATLAS experiment at $\sqrt{s_{_\mathrm{NN}}}$=5.02 TeV we have studied prompt and non-prompt $J/\psi$ and $\psi(2S)$ productions via their di-muon decay channel. In this poster, ATLAS will present in detail how the separation of prompt and non-prompt signal is performed, as well as the description of the systematic uncertainties and technical details of the yield and suppression measurements.

Speaker: Sebastian Tapia Araya (Federico Santa Maria Technical University (CL))

poster_QM_v3.pdf

458 Suppression of high $p_T$ single hadrons and dihadrons in heavy-ion collisions at $\sqrt{s_\rm{NN}}$ = 0.2, 2.76 and 5.02 TeV

The suppression of high $p_T$ single hadron and dihadron productions in high-energy heavy-ion collisions at RHIC and the LHC energies is studied within a NLO pQCD model [1, 2]. The jet quenching effect is included via the medium-modified fragmentation functions based on the higher-twist energy loss formalism [3]. The evolution of the bulk medium is simulated by a (2+1)-dimensional viscous hydrodynamic model which has been tuned to describe the soft hadron production at RHIC and the LHC [4].
A global $\chi^2$ fit is performed for both single hadron $R_{AA}$ and dihadron $I_{AA}$ with the experimental data taken from ALICE, CMS, PHENIX and STAR Collaborations, and the jet transport coefficient $\hat q_0$ is quantitatively extracted for central A+A collisions at both RHIC and the LHC energies. Our results show that $\hat q_0$ extracted from dihadron suppression is consistent with single hadron suppression. We obtain, for energetic quarks, $\hat q_{0}\approx 1.1 \pm 0.3$ GeV$^2$/fm in central Au+Au collisions at RHIC, while $\hat q_{0}\approx 1.8 \pm 0.5$ GeV$^2$/fm in central Pb+Pb collisions at the LHC. Using the $\hat q_0$ values extracted from central A+A collisions, we obtain good description of the experimental data on single hadron $R_{AA}$ and dihadron $I_{AA}$ in non-central A+A collisions at $\sqrt{s_{\rm{NN}}}$ = 0.2 and 2.76 TeV. We also predict dihadron $I_{AA}$ at $\sqrt{s_{\rm{NN}}}$ = 5.02 TeV using the $\hat{q}_0$ value extracted from single hadron $R_{AA}$.

References

[1] Hanzhong Zhang, J. F. Owens, Enke Wang, Xin-Nian Wang, Phys. Rev. Lett. 103, 032302 (2009).

[2] Zhi-Quan Liu, Hanzhong Zhang, Ben-Wei Zhang, Enke Wang, Eur. Phys. J. C 76, no. 1, 20 (2016).

[3] Xiao-feng Guo, Xin-Nian Wang, Phys. Rev. Lett. 85, 3591 (2000).

[4] Chun Shen, Zhi Qiu, Huichao Song, Jonah Bernhard, Steffen Bass, Ulrich Heinz, Com- put. Phys. Commun. 199, 61 (2016).

Speaker: Ms Man Xie (Central China Normal University)

xieman-QM-poster2.pdf

459 Suppression of resonance production in high multiplicity pp events due to colour reconnection effects in PYTHIA8

The measurement of short-lived hadronic resonances in high energy collisions has always been considered an important observable to investigate the properties of the systems created in such collisions. In particular, the observed suppression of the measured yields of resonance with respect to non-resonance particles towards central heavy-ion collisions has so far been interpreted as being due to re-scattering of decay daughters in a hadronic phase of the system evolution. However, hints of suppression in the measured resonance to non-resonance particle ratios have also been recently observed for high multiplicity events in collisions of small systems, such as pp and p-Pb. In this work, we explore the effects of colour reconnection (CR) mechanisms, such as the new more QCD based scheme and the rope hadronization approach, in hadronic resonance production in high multiplicity pp collisions using the PTYHIA8 event generator. Our studies have shown that the inclusion of CR leads to a suppression of hadronic resonance production with respect to non-resonance states, observed in the evolution of the ratios of $K^{*}/K$, $\rho/\pi$ and $\eta’/\pi$ as a function of the event activity. These results bring an alternative possible explanation for the phenomenon in small systems collisions. Finally, we discuss other heavy-ion observables that may also be affected by CR, such as those associated with collectivity.

Speaker: Rafael Derradi De Souza (University of Campinas UNICAMP (BR))

poster_QM2018_v3.pdf

460 Surprising similarities between the high transverse Surprising similarities between the high transverse momentum spectra in pp and Pb-Pb collisions at sNN = 5.02 TeV

We present the comparison of the transverse momentum (pT) spectra for different centralities in Pb-Pb collisions with multiplicity dependent spectra in pp collisions and the apparent link among them.

The origin of the work lies in two observations concerning particle production at high pT (> 8 GeV/c) in pp and Pb-Pb collisions at sNN = 5.02 TeV. On one hand, within uncertainties the RAA of light and heavy flavoured particles is essentially the same. On the other hand, the identity of the rise observed in the RAA with that observed in the ratios of the multiplicity dependent spectra, in pp collisions, divided by the same pp reference spectrum. We have made a systematic study of available data, fitting the power law function to the high pT spectra in different multiplicity and centrality classes. The comparison of the spectra of pp and Pb-Pb collisions at multiplicities corresponding to the same power law exponent exhibits marked differences at low momenta, namely, an increased contribution of low momentum particles, that could be attributed to the debris of the high momentum jets in Pb-Pb collisions. The claim is supported with studies of leading particle pT production as well as its connection with the event activity and quenching properties. The connection to the respective energy densities will be discussed.

Speaker: Guy Paic (Universidad Nacional Autonoma (MX))

461 System-size and energy dependence of hyperon production with ALICE in p-Pb collisions at the LHC

One of the key results of the LHC Run 1 was the observation of an enhanced production of strange particles in high multiplicity pp and p-Pb collisions at 7 and 5.02 TeV, respectively. In this contribution, the energy dependence of this phenomenon is addressed by new measurements of strange and multi-strange particle production in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV and $\sqrt{s_{\rm NN}}$ = 8.16 TeV as function of transverse momentum and multiplicity. The large statistics sample collected during the LHC Run 2 is used. The strangeness enhancement is investigated by measuring the evolution with multiplicity of single-strange and multi-strange baryon production relative to non-strange particles. The results from pp, p-Pb and Pb-Pb are compared to each other as well as to statistical hadronisation models and Monte Carlo predictions.

Speaker: Silvia Delsanto (Universita e INFN Torino (IT))

2018-may-10-conference_presentation-silvia_delsanto_poster_qm2018_version_5.pdf

462 Temperature dependence of $\eta/s$: Constraints from Xe+Xe collisions and uncertainties from the equation of state

Recent advancements in multi-parameter model-to-data comparison have provided notable constraints on the temperature dependence of the shear viscosity over entropy density ratio $\eta/s$ in the matter produced in the Pb+Pb collisions at the LHC. Bayesian analysis with a flexible initial state parametrization [1,2] supports a linear temperature dependence of $\eta/s$ found in the earlier study using the EKRT pQCD + saturation + hydrodynamics model [3]. However, some open issues yet remain. The uncertainties regarding the value of $\eta/s$ increase quickly towards higher temperatures, and it remains unexplored how much the choice of the equation of state affects the final outcome of the global analysis.

The recently performed LHC Xe+Xe run at $\sqrt{s_{NN}}=5.44$ TeV introduces a new nuclear mass number and a new maximum collision energy for the heavy ion collisions, and consequently adding Xe+Xe data to the analysis has potential to further constrain $\eta/s(T)$. We perform a global model-to-data comparison on Au+Au, Pb+Pb, and Xe+Xe collisions at $\sqrt{s_{NN}}=200$ GeV, $2.76$ TeV, $5.02$ TeV and $5.44$ TeV, respectively, using a hydrodynamics model with the EKRT initial state, and the same parametric form for $\eta/s(T)$ as in Ref. [3]. Furthermore, to quantify the amount of uncertainty incorporated in the choice of EoS, we compare analysis results based on three different equations of state: the well known s95p parametrisation [4], an updated parametrisation based on the same list of particles, but recent lattice results [5] for the partonic EoS, and an updated parametrisation based on the Particle Data Group 2016 particle list and the recent lattice results.

References:
[1] Bernhard et al., PRC 94, 024907 (2016)
[2] Bass et al., NPA 967, 67 (2017)
[3] Niemi et al., PRC 93, 024907 (2016)
[4] Huovinen and Petreczky, NPA 837, 26 (2010)
[5] Bazavov et al., arXiv:1710.05024 and
Bazavov et al., PRD 90, 094503 (2014) and
Borsanyi et al., PLB 730, 99 (2014)

Speaker: Jussi Auvinen (Institute of Physics Belgrade)

qm18poster_auvinen.pdf

463 Temperature dependence of transport coefficients of QCD in high-energy heavy-ion collisions

We quantitatively investigate the temperature dependence of shear and bulk viscosities 
of QCD from comparison with ALICE data of Pb+Pb √sNN = 2.76 collisions at the LHC, using our state-of-the-art (3+1)-d relativistic viscous hydrodynamics code [4]. The algorithm for solving the relativistic hydrodynamic equation is based on a Riemann solver with the two shock approximation [1,2] and stable even with small numerical viscosity [1]. We check the energy and momentum conservation in one-dimensional expansion with initial fluctuations of high-energy heavy ion collisions and the correctness of our code in the following test problems; the viscous Bjorken flow for one-dimensional expansion and the Israel-Stewart theory in Gubser flow regime for the three-dimensional calculation [3]. 

Applying the hydrodynamics code to the hybrid model, hydro+UrQMD model, 
we perform comprehensive analyses of ALICE data. Here we use the initial condition, TRENTO and lattice QCD-based equations of state. We find that flow harmonics as a function of transverse momentum Pt is not sensitive to transport coefficients, though centrality dependence of mean Pt and integrated v2 and v3 is sensitive to them. To obtain the detail information of transport coefficients, investigation of rapidity dependence of observables with (3+1)-d hydrodynamic expansion is indispensable. From our numerical computation, we obtain the following temperature dependence of transport coefficients. Finite bulk viscosity is preferable and the bulk viscosity has a peak around the critical temperature. The shear viscosity increases with decreasing temperature in the hadronic phase and takes a minimum value around the critical temperature and increases with temperature in the QGP phase.

[1]Akamatsu,Inutsuka, Nonaka, and Takamoto,J. Comput. Phys. 256,34(2014).
[2]Okamoto, Akamatsu, and Nonaka, Eur. Phys.J. C76, 579(2016).
[3]Okamoto and Nonaka, Eur. Phys. J. C77, 383(2017). 
[4]Okamoto and Nonaka, arXiv:1712.00923.

Speaker: Prof. Chiho Nonaka (Nagoya University)

qm2018_poster.pdf

464 Test and development of the front-end electronics for the Silicon Tracking System of the CBM experiment

The Compressed Baryonic Matter (CBM) Experiment at the FAIR facility will explore the QCD phase diagram at very high baryon densities, where a first order phase transition from hadronic to partonic matter as well as a chiral phase transition is expected to occur. The design goal of CBM is to cope with very high interaction rates up to 10 MHz. This will allow performing high precision measurements of extremely rare probes. To achieve the high rate capability, CBM will be equipped with fast and radiation hard detectors employing free-streaming readout electronics. The Silicon Tracking System (STS), is the essential component for tracking up to 1000 particles per event in A+A collision. Having 2.1 million readout channels, it poses the most demanding requirements in terms of bandwidth and density of all CBM detectors. The custom developed front-end device for reading out the double-sided silicon sensors is the STS-XYTER ASIC. This is a low power, self-triggering ASIC with 128 channels, which provides timing and energy information for each sensor signal. In addition, the ASIC implements a new readout protocol, developed for operation with the GBTx data aggregation ASIC. To ensure its satisfactory operation, it demands low noise levels as the system is self-triggering; it needs to be fully integrated into a very confined space and it must have a reliable performance in a highly irradiated environment and strong magnetic field. Various tests are carried out to check the ASIC functionalities, its performance in different data taking scenarios, system integration as well as radiation hardness. An overview of the experimental setup, device testing procedures and results will be presented.

Speaker: Adrian Rodriguez (Goethe University Frankfurt am Main)

QM2018_Rodriguez_Lehnert_poster.pdf

465 Test Stand and performance studies of scintillator tiles for the sPHENIX Hadronic Calorimeter

The sPHENIX experiment will collect high statistics proton-proton, proton-nucleus and nucleus-nucleus data at the Relativistic Heavy Ion Collider (RHIC) from the early 2020's. sPHENIX will investigate jet modification, upsilon suppression and open heavy flavor production to probe the nature of Quark Gluon Plasma, and will perform a broad range of cold QCD studies. A key component to the detector design and the ability to accurately measure jets is the hadronic calorimeter (HCal). The sPHENIX HCal is located outside of the solenoid magnet and is composed of alternating layers of tapered steel plates and scintillator tiles. These layers are tilted in azimuth such that a particle coming directly from the interaction point will traverse 4 tiles. The extruded plastic tiles are embedded with a wavelength shifting fiber which directs the light produced by the energy deposited in the tile to SiPMs. This design has been shown to yield the energy resolution required by the sPHENIX physics program.

It is crucial that the tiles behave uniformly, therefore, in preparation of the production phase of sPHENIX, a test stand for the tiles and a quality test has been developed to ensure the performance of the tiles prior to assembly. This poster will present the design of the tile test stand, the plans for production and testing of the tiles, in addition to showing studies of the tiles' response to cosmic rays using the test stand setup and their connection to the calibration of the detector.

Speaker: Megan Elizabeth Connors (GSU)

sPhenix_QM18poster_HCal_ConnorsV2.pdf

466 The Azimuthal Angle Dependence of Lambda (anti-Lambda) Polarization in Au+Au Collisions from STAR

The STAR experiment at RHIC has observed for the first time a significant alignment between the angular momentum of the medium produced in non-central collisions [1] and the spin of $\Lambda$($\overline{\Lambda}$) hyperons ($J$$=$1/2), revealing that the matter produced in heavy-ion collisions is by far the most vortical system ever observed. Such vorticity is expected to be maximal at the equator, and due to the low viscosity of the system, the vorticity may not be propagated efficiently to the poles. This may lead to a larger in-plane than out-of-plane polarization for $\Lambda$ hyperons.

In this poster, we will present the azimuthal angle (with respect to the reaction plane) dependence of $\Lambda$ and $\overline{\Lambda}$ polarization in 20-50% central Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV. The implications of our results will be discussed.

Reference
[1] L. Adamczyk et al. (STAR Collaboration), Nature 548, 62 (2017).

Speaker: Biao Tu (Central China Normal University and Brookhaven National Laboratory)

BiaoTu_QM18_poster.pdf

467 The CBM Time-of-Flight system

The Compressed Baryonic Matter (CBM) experiment aims at exploring the QCD phase diagram at large baryon densities in the beam energy range from 2 A GeV to 11 (35) A GeV at the SIS100 (SIS300) accelerator of FAIR/GSI. For charged particle identification that is required by many observables that are sensitive to the phase structure like collective flow, phase space population of rare hyperons, fluctuations of conserved quantities, … a high performance Time-of-Flight (TOF) wall with a granularity of about 100.000 channels and a system timing resolution of better than 80 ps is being built. Part of the wall (~ 10.000 channels) will be installed in the forward hemisphere ( 1.0 < eta < 1.5) of the STAR experiment at RHIC/ BNL during the beam energy scan (BES II) campaign planned for 2019/2020. The status and performance of the detector system as well as the physics reach will be discussed.

Speaker: Ingo-Martin Deppner (Physikalisches Institut der Universität Heidelberg)

deppner_QM18_poster_V2_1.pdf

468 The free-streaming data acquisition system for the Compressed Baryonic Matter experiment at FAIR

The Compressed Baryonic Matter experiment (CBM) will be based at the new Facility for Antiproton and Ion Research (FAIR), which will deliver heavy-ion beams up to energies of 14 AGeV. In nucleus-nucleus collisions at these beam energies strongly interacting matter with densities up to 10 times normal nuclear matter is expected to be produced. The key objective of CBM is to investigate the QCD phase diagram in the region of high baryon-densities, where a first order phase transition from hadronic to partonic matter as well as a chiral phase transition is expected to occur, representing a substantial discovery potential at FAIR energies. As a fixed-target experiment CBM is consequently designed to cope with very high interaction rates up to 10 MHz. This will allow to perform high precision measurements of extremely rare probes which have not been accessible by previous nucleus-nucleus experiments in this energy regime. To achieve the high rate capability CBM will be equipped with fast and radiation hard detectors employing free-streaming readout electronics. A prototype high performance Data Aquisition (DAQ) system is currently being built for mini-CBM (mCBM). The mCBM setup is scaled down from the full CBM experiment. Already by summer 2018, it will serve as development platform for a high rate system test of the detector systems, the free-streaming readout chain, the online time-slice building and online event selection in the First Level Event Selector (FLES). We will report on the concept and status of the CBM DAQ system.

Speaker: Dr David Emschermann (GSI)

20180523_QM2018_CBM_DAQ_poster_v06.pdf

469 The HADES RICH Upgrade Program*

The HADES experiment at GSI, Darmstadt, is a key element of the FAIR Phase 0 activities, and will continue data taking at its present location at the SIS 18 accelerator.
The next beamtime has been approved and scheduled for August 2018, with 4 weeks of data taking in $Ag+Ag$ collisions at 1.65 AGeV, aiming to study baryonic matter in the region of high net-baryon density.

For the upcoming beamtime, the HADES RICH detector is currently undergoing an upgrade, to ensure enhanced dielectron reconstruction.
For the upgrade, the current $CsI$ based MWPC will be exchanged with an arrangement of multi-anode photo multiplier tubes (HAMAMATSU H12700).
The upgrade of the photon detector is supplemented by the development of a completely new electronic readout chain, with the $32\,$ch DIRICH FPGA-TDC readout module as its core element.
The DIRICH module combines discrimination, time measurement, and data handling on a single FPGA, providing a powerful and cost-efficient solution for this kind of sensor.
The larger efficiency of the new photomultiplier sensors will significantly enhance the detection efficiency for $e^{+}$$e^{-}$ pairs with small opening angle and hence reduce combinatorial background.

The poster will give an overview on the advanced status of the HADES RICH upgrade project.
One focus will be on the performance evaluation of the new readout chain, both in lab measurements and prototype tests.
Showing the excellent performance, low noise and good interplay between readout electronics and MAPMTs.
Furthermore, simulation results on the detector performance will be shown, demonstrating the influence of the new components on the overall performance of the improved HADES RICH.

*supported by BMBF grants 05P15PXFCA and 05P15RGFCA, GSI and HGS-HiRe

Speakers: Mr Jan-Hendrik Otto (Justus-Liebig-Universität Giessen), Jörg Förtsch (Universität Wuppertal)

Poster QM 18.pdf

Poster QM 18.pptx

470 The measurement of W boson in pPb collisions at sqrt(sNN) = 8.16 TeV with the CMS detector

The measurement of the W boson in pPb collisions at sqrt(sNN) = 8.16 TeV is presented. The muon decay channel was used to study both positive and negative W bosons production as a function of muon pseudorapidity. Rapidity and charge asymmetries in the W yield are also shown, and a comparison with theoretical predictions with and without nuclear PDF (nPDF) effects is made. The measurement is sensitive to the presence of nuclear modifications to the parton distributions in the lead nucleus, and can help improve and constrain future nPDF calculations.

Speaker: Hyunchul Kim (Chonnam National University (KR))

HyunchulKIM_QM2018_poster_final.pdf

471 The Power Spectrum of Heavy Ion Collisions

Using features from Cosmic Microwave Background (CMB) analysis, we calculate the angular power spectrum of central heavy ion collisions at $ \sqrt{s_{NN}} = 5.02 \mathrm{TeV} $. The idea is to treat the particles' angular distribution like the background radiation originated from the recombination epoch of the early Universe. In practice, detector deficiencies and lack of full pseudorapidity ($\eta$) coverage introduce artificial structures to the power spectrum, which are related only to the geometric cuts, i.e. to the $ \eta $ range. We clarify this issue in order to determine what is the true power spectrum of an ideal detector. One can thus finally discover which properties of the Quark Gluon Plasma (QGP) can be seen through this type of analysis.

Speaker: Ms Meera Vieira Machado (Niels Bohr Institute)

poster_QM2018.pdf

472 The Projectile Spectator Detectors for the CBM at FAIR and NA61/SHINE at CERN

The unique feature of future CBM experiment at FAIR and NA61/SHINE experiment beyond 2020 at CERN SPS are their high-rate capabilities that makes these experiments sensitive to the extremely rare probes. The Projectile Spectator Detector (PSD) is the forward hadron calorimeter to be used in these both fixed target experiments to measure the event centrality and reaction plane orientation in heavy-ion collisions. The PSD at the CBM is designed for the beam energy range of 4-10 AGeV and rates up to 10 MHz, whereas the PSD at the NA61 beyond 2020 would operate in the beam energy range of 20-150A GeV and rates up to 5x10$^4$ Hz.
In this poster we will present the status of the development of the PSD for both, CBM and NA61 beyond 2020 experiments. Both detectors have similar design, modular transverse structure and longitudinal segmentation. Each module has 5.6 hadron interaction lengths and transverse size of 200x200 $mm^2$. The module consist of 60 lead/scintillator sandwiches with the sampling ratio 4:1. Light from each scintillator plate in module is collected by WLS fibers. Six consecutive scintillator plates are read out by one photodetector, 3x3 $mm^2$ Hamamatsu MPPC placed at the end of the module.
Recently, for the first time, the PSD supermodule (3x3 array of 9 modules) was studied at CERN test beams with protons and pions in the energy range of 2-10 GeV. Preliminary results of the energy resolution, linearity of response and longitudinal profile of hadron showers will be presented. These results are undoubtedly important also for the development of forward hadron calorimeters for MPD/NICA and BM@N experiments in Dubna.

Speaker: Fedor Guber (Russian Academy of Sciences (RU))

Guber_poster_QM2018_NA61_CBM_PSD_8.pdf

473 The RICH detector for the CBM experiment at FAIR

The Compressed Baryonic Matter (CBM) experiment at the future FAIR complex will investigate the phase diagram of strongly interacting matter at high baryon density and moderate temperature in A+A collisions from 2-15 AGeV (SIS 100). One of the most promising observables to explore this matter is electromagnetic radiation from the fireball.

One of the key detectors for clean electron identification is the RICH (Ring Imaging Cherenkov) detector using CO${_2}$ as radiator gas, spherical glass mirrors with reflective Al+MgF${_2}$ coating as focusing elements and a photo-detector plane consisting of an array of H12700 MAPMTs from Hamamatsu. Prior to the CBM start at FAIR about half of theses MAPMTs will be employed for the upgrade of the HADES RICH detector. An FPGA-TDC based readout chain is being developed in cooperation with both experiments.
The mirror wall will consist of two half spheres with 40 trapezoidal glass mirrors each with high reflectivity and excellent surface homogeneity. An important aspect to guarantee a stable operation of the RICH detector is the mirror alignment and its control.

In this poster we will report on the design and status of the CBM RICH developments with particular focus on the mirror wall development as well as qualitative and quantitative measurements to monitor and correct potential mirror misalignments.

Speaker: Jordan Bendarouach (Justus Liebig University (Giessen))

Poster_QM2018_JBendarouach.pdf

474 The sign change of the four-particle cumulant in small systems from hydrodynamics and momentum conservation

The azimuthal cumulants, $c_2\{2\}$ and $c_2\{4\}$, originating from the global conservation of transverse momentum [1] in the presence of hydro-like elliptic flow are calculated [2]. We observe a sign change of $c_2\{4\}$ for small number of produced particles, which is in a qualitative agreement with the recent ATLAS measurement of multi-particle azimuthal correlations with the subevent cumulant method [3]. Our results offer a new insight into the problem of the onset of collectivity in small systems.

References
1. Adam Bzdak and Guo-Liang Ma, arXiv: 1710.00653.
2. Adam Bzdak and Guo-Liang Ma, in preparation.
3. The ATLAS Collaboration, arXiv:1708.03559.

Speaker: Dr Guo-Liang Ma (Shanghai INstitute of Applied Physics (SINAP), CAS)

TMC_poster_v2.pdf

475 The Silicon Tracking System of the CBM experiment at FAIR

In the CBM experiment at FAIR, the Silicon Tracking System is the central detector for charged-particle identification and momentum measurement. Its key performance requirements are (a) pile-up free track measurement in collision rates between 0.1 and 10 MHz, (b) momentum resolution in a 1 Tm dipole magnetic field of better than 2%, and (c) capabilities for the identification of particle decays, e.g. such with strangeness content.

The STS comprises 8 tracking stations equipped with double-sided silicon microstrip sensors. Two million channels are read out with self-triggering electronics, matching the data streaming and on-line event analysis concept applied throughout the experiment. The detector’s functional building block is a module consisting of a sensor, microcables and two front-end electronics boards. The modules are mounted on carbon fiber support ladders and further to mechanical frames. The microstrip sensors provide double-sided segmentation at a strip pitch of 58 $\mu$m and 7.5 degree stereo angle, have integrated AC signal coupling and second-metal routing lines. Ultra-thin microcables with up to 60 cm length transfer the sensor signals to the electronics located at the periphery of the detector. The custom-developed 128-channel read-out ASIC “STS-XYTER” has a self-triggering architecture that delivers time and amplitude information per channel. The detector will be operated at below −5 $^\circ$C within a thermal enclosure of about 2 m$^3$ volume so that the sensors’ leakage currents are kept low and the detector remains operational up to an integrated particle fluence of 10$^{14}$ n/cm$^{2}$ (1 MeV equivalent). The front-end, data aggregation and powering electronics will dissipate about 40 kW which is planned to be taken out of the system with a bi-phase CO$_2$ evaporative cooling.

The presentation will discuss the development status of the STS components and system integration and will give an outlook on the beginning detector construction.

Speaker: Johann Heuser (GSI - Helmholtzzentrum fur Schwerionenforschung GmbH (DE))

QM2018_poster_CBM-STS_J.Heuser.pdf

QM2018_poster_CBM-STS_J.Heuser.pptx

476 The Specific Shear Viscosity of a Hot Hadron Gas

We extract the specific shear viscosity eta/s of nuclear matter in the hadronic phase for various temperatures and chemical potentials from data. We use a blastwave parameterization of the final state of high energy nuclear collisions, including non-equilibrium deformations of particle distributions due to shear stress in the Navier-Stokes approximation. We apply a Bayesian analysis to spectra and elliptic flow of identified hadrons for a variety of collision energies and centralities at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). The systems analyzed cover a temperature range from about 110 to 145 MeV and vary in their chemical potentials for hadrons. We find that eta/s falls from about 6/(4pi) at lower temperatures to close to the proposed quantum bound 1/(4pi) at higher temperatures. We attempt to assign meaningful systematic uncertainties to our results. This work is complementary to efforts using viscous fluid dynamics to extract the specific shear viscosity of quark gluon plasma at higher temperatures.

Speaker: Rainer Fries (Texas A&M University)

477 The sPHENIX HF-jet physics program

Jets initiating from heavy flavor quarks (HF-jets) are sensitive to the collisional energy loss of high energy partons when traversing through Quark Gluon Plasma. Using sPHENIX, a state-of-the-art jet detector, we will perform the first HF-jet measurements at RHIC, which will include the nuclear modification and flow of $b$-jets, and the momentum balance in di-$b$-jet pairs. A variety of $b$-Jet tagging algorithms have been developed, which select the HF-jet sample rich in tracks displaced from the primary collision point as measured by the high precision sPHENIX MAPS vertex tracker. The detection method, physics projection and possible impact to the field of our understanding of parton energy loss will be discussed in this poster.

Speaker: Dr Jin Huang (Brookhaven National Lab)

sPhenix_QM18poster_bjet.pdf

478 The STAR Forward-Rapidity Physics Program after the BES-II

The physics program described in this poster complements the STAR mid-rapidity physics program after the BES-II. The program is based on the planned STAR forward rapidity (2.5 < $\eta$ < 4.5) detector upgrade, consisting of tracking detectors (Silicon mini-strip disks combined with small-strip Thin Gap Chambers) preceded by an electromagnetic and hadronic calorimeter. The uniqueness of the forward rapidity pA program is based on the flexibility of the RHIC accelerator to run collisions of different particle species at very different center-of-mass energies. This in combination with the existing and planned STAR detector capabilities allows to disentangle nuclear effects in the initial and final state as well as leading twist shadowing from saturation effects in a kinematic regime where all these effects are predicted to be large. It is specifically noted that the forward upgrade will provide new detector capabilities at RHIC and STAR to explore the longitudinal structure of the initial state and the temperature dependent transport properties of matter in relativistic heavy ion collisions.

Speaker: Li Yi (Yale University)

479 The STAR Mid-Rapidity Physics Program after the BES-II

Upgrades that are currently underway to maximize the physics output from Beam Energy Scan (BES) phase II will substantially enhance STAR's already excellent capabilities. These upgrades will enable STAR to continue its unique, ground-breaking mid-rapidity science program in the period following BES-II. The key physics opportunities envisioned address three broad areas of interest within the cold QCD community in the years following the BES-II. These programs will shed light on the dynamics of low and high x partons in cold nuclear matter (CNM) and how the fragmentation and hadronization of these partons is modified through interactions within the CNM and experiments to study the 2+1d spatial and momentum structure of protons and nuclei. These measurements will provide critical new insights into the QCD structure of nucleons and nuclei in the near term, as well as the high precision data that will be essential to enable rigorous universality tests when combined with future results from the Electron Ion Collider. In A+A collisions measurements with unprecedented precision using deep penetrating probes such as leptons and photons will enable us to probe the whole evolution of the collision. In addition, significantly improved hypertriton lifetime measurements may have important implications on astrophysics. The poster will highlight mid-rapidity physics program after the BES-II.

Speaker: Qian Yang (Shandong University)

480 The Study of Muon Production in Ultra-Peripheral Collisions in Au+Au and U+U in the PHENIX Experiment at RHIC

High energy photon-nucleon (nucleus) collisions provide a unique opportunity to probe the gluon distribution of nuclei in ultra-peripheral ions collisions (UPC). This study provides the initial state constraints for probing the properties of quark-gluon plasma created in relativistic heavy ion collisions. The viability of this physics analysis has been demonstrated both at the RHIC and LHC experiments by triggering on electromagnetic processes produced in ultra-peripheral A+A collisions. In this poster, we will present 1) the data analysis status of muon production (mainly from $\phi$ and $J/\psi$) in the forward rapidity range of $1.2 < |\eta| < 2.4$ both for the RHIC Run12 U+U collisions at $\sqrt{s_{NN}} = 193$ GeV and the Run14 Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV, respectively, and 2) Monte Carlo simulations based on STARlight for these collisions.

Speaker: Prof. Xiaochun He (Georgia State University)

481 The thermodynamics of a geometrically confined small system

The emergence of evidence for collectivity and strangeness enhancement in small colliding systems has raised urgent questions surrounding the apparent absence of energy loss among the observables that are traditionally attributed to the presence of a Quark Gluon Plasma in heavy ion collisions. However, theoretical difficulties abound in the calculation of any measure of the energy loss, resulting in methods that were highly successful in the heavy ion regime coming up empty handed in the small system arena. We present a novel approach, generalizing standard thermal field theory and thermodynamic techniques, to probe the thermodynamic behavior of a small system. We consider first a single free scalar field theory that is geometrically confined. We investigate the partition function along with the usual thermodynamic quantities, as well as the thermodynamic stability and statistical fluctuations of such a system. Our results, while still approaching the Stefan-Boltzmann limit for large systems, offer new insights into the thermodynamics of smaller systems and exhibit new, Casimir-like effects, thereby also providing a natural solution to the so-called infra-red Linde problem.

Speaker: Isobel Kolbe (University of Cape Town (ZA))

QM18Kolbe_1.pdf

482 The Tsallis Thermometer -- understanding the non-extensivity parametersThe Tsallis Thermometer -- understanding the non-extensivity parameters

Identified hadron spectra from recent years are analyzed in the non-
extensive thermodynamical framework. The Tsallis-Pareto cut power-law
is known to describe the pT distributions for a wide energy range, but
its origin is thermodynamical-model dependent [1,2].

We pursue the physical origin of this observation by investigating the
center-of-mass energy, multiplicity, mass and strangeness dependency of
the Tsallis q and T parameters comprehensively from ee, pp to pA
collisions [3,4]. We describe the main characteristics of a statistical
hadronization model that could explain our observations. We present the
Tsallis-thermometer, which can be use to gain more information on the
high-energy nuclear collisions even for the smallest system [5].

[1] T.S. Biró, G.G. Barnaföldi, P. Ván, Thermodynamic Derivation of the Tsallis and Rényi Entropy Formulas and the Temperature of Quark-Gluon Plasma, Eur.Phys.J. A49 (2013) 110;
[2] T.S. Biró, P. Ván, G.G. Barnaföldi, K. Ürmössy, Statistical Power Law due to Reservoir Fluctuations and the Universal Thermostat Independence Principle, Entropy 2014, 16(12), 6497-6514;
[3] K. Ürmössy, T.S. Biró, G.G. Barnaföldi, Microcanonical jet-fragmentation in proton–proton collisions at LHC energy, Phys.Lett. B718 (2012) 125-129;
[4] G. Bíró, G.G. Barnaföldi, T.S. Biró, K. Ürmössy, Á. Takács, Systematic Analysis of the Non-Extensive Statistical Approach in High Energy Particle Collisions—Experiment vs. Theory, Entropy 2017, 19(3), 88;
[5] G. Bíró et al, in preparation.

Speaker: Ádám Takács (Wigner Research Centre for Physics)

Adam_Takacs_QM18_poster.pdf

483 Thermal dilepton radiation at low and intermediate collision energies from a coarse-graining approach

Electromagnetic radiation emanates over the entire course of a heavy-ion collision, decoupling from the matter once produced, thus providing unique information about the interacting QCD medium. Specifically, the yield of low-mass thermal dileptons was identified as a measure of the fireball lifetime, while the slope of intermediate-mass dilepton spectra can serve as a thermometer unaffected by blue-shift effects of collective expansion which distort $p_T$ spectra. Here, we couple in-medium thermal dilepton rates, which reproduce existing data at ultrarelativistic collision energies, with a coarse-graining method of hadronic transport simulations to compute dilepton spectra at lower energies, $\sqrt{s_{NN}} \leq$ 10 GeV, where hydrodynamic simulations may be less reliable. By extracting local temperature, baryon and pion densities the convolution with thermal rates can be readily carried out. Our calculations suggest that also at lower energies the $\rho$-meson melting in a near-thermal source prevails and that the emission duration closely correlates with the build-up of the transverse flow in the fireball. The resulting yields and slopes of the invariant-mass spectra extend previous excitation functions of the fireball lifetimes and temperatures to lower energies. We use this as a baseline to analyze signatures of a putative critical point on dilepton observables, to facilitate its search in future campaigns with the HADES and CBM experiments at GSI/FAIR, as well as in the RHIC beam energy scan phase II with STAR.

Speaker: Florian Seck (TU Darmstadt)

seck_qm18.pdf

484 Thermal fluctuations in relativistic heavy-ion collisions

Fluctuation-dissipation theorem indicates the presence of hydrodynamic (local thermal) fluctuations in otherwise deterministic theory of viscous hydrodynamics. We have formulated a general theory of thermal fluctuations within causal second-order viscous hydrodynamic evolution of matter formed in relativistic heavy ion collisions. The fluctuation is treated perturbatively on top of boost-invariant longitudinal expansion [(0+1)-dim] as well as for realistic (1+1)-dim expansion. A numerical model simulation was developed for hydrodynamic evolution in (1+1)-dim which was tested to reproduce the analytic results for the Riemann solutions of expansion of matter in vacuum at early times, and the Landau-Khalatnikov wave propagation inside the medium for later times. Numerical simulation of thermal noise is performed for various second-order dissipative evolution equations using lattice QCD equation of state. Phenomenological effects of thermal fluctuations for the two-particle rapidity correlations showed that viscous damping of the correlation is at most ~20%.Further, significant damping was found at small rapidity separations when second-order dissipative hydrodynamics was employed instead of first-order Navier-Stokes theory. As compared to the conformal equation of state, the softer lattice QCD EOS causes reduced propagation of the fluctuations and leads to a pronounced peak in
the rapidity correlations. In contrast to Bjorken flow, enhanced velocity gradients at large rapidities induce quite large fluctuations and thereby larger rapidity correlations.

Speaker: Prof. Subrata Pal (Tata Institute of Fundamental Research, Mumbai, India)

poster.pdf

485 Thermodynamic and magnetic properties of hot QCD medium in a strong magnetic field

We have investigated the equation of state of a hot QCD medium with two light flavors in a strong magnetic field, which may be produced in the non-central events at RHIC and LHC. We have cal- culated the thermodynamic observables up to one-loop perturbatively in real-time formalism, where the quark contribution is largely affected by the magnetic field whereas the gluon component is least affected except for the softening of the screening mass. For example, the presence of a strong magnetic field makes the pressure of hot QCD medium larger and the dependence of pressure on the tempera- ture becomes less steep compared to the dependence of the pressure on the magnetic field. This can be understood from the dominant scale of thermal medium in the strong magnetic field, being the magnetic field, in the same way that the temperature dominates in a thermal medium in the absence of magnetic field. the dependence of pressure on the temperature becomes less steep. Consistent with the above observations, the entropy density is found to decrease with the temperature in the presence of a strong magnetic field which is again consistent with the fact that the strong magnetic field restricts the dynamics of quarks to two dimensions, hence the phase-space becomes squeezed resulting in the reduction of the number of microstates. Due to the aforesaid reasoning, the energy density of hot QCD medium is seen to decrease, hence the speed of sound of thermal is increased due to the presence of a strong magnetic field. These findings could have implications on the expansion of the medium produced at RHIC and LHC and influence the outcomes of various signatures. Finally we determine the magnetization and susceptibility for several temperatures in strong magnetic field, where the paramagnetic response increases with the temperature. Hence a portion of QGP may be squeezed perpendicular to the direction of magnetic field, which is quantified by the enhancement of elliptic flow.

Speaker: Ms Subhalaxmi Rath (Indian Institute of Technology Roorkee)

POSTER_Shubhalaxmi.pdf

486 Time-based particle reconstruction and event selection in the CBM experiment.

The CBM experiment is a future fixed-target heavy-ion experiment at FAIR/GSI, targeting for very rare probe measurements. In order to obtain sufficient statistics, the experiment will operate at high interaction rates of up to 10 MHz. Moreover, most of the trigger signatures are complex and require information from several detector subsystems. Thus, CBM needs a novel data read-out and analysis concept based on free streaming front-end electronics. The CBM experiment will collect time-stamped data into a readout buffer in a form of a time-slice and deliver it to a large computer farm. In order to effectively reduce the number of events to be recorded, a First Level Event Selection (FLES) has to identify a clean event sample containing the desired physical observable.

Grouping measurements into physical collisions in this case must be performed in software and requires reconstruction not only in space, but also in time, the so-called 4-dimensional reconstruction. The FLES reconstruction package consists of several modules: track finding, track fitting, event building, short-lived particles finding, and event selection, which allow reconstructing time-slices in parallel (between processor cores). The tracks, reconstructed with the 4D Cellular Automaton track finder, are combined into event-corresponding clusters according to the estimated production time, obtained with the 4D Kalman Filter method. The reconstructed events are given as an input to the KF Particle Finder package for short-lived particle reconstruction. The last stage of the FLES package is a selection of events according to the requested trigger signatures. The reconstruction procedure and the results of its application to simulated collisions for the CBM detector setup are presented.

Speaker: Akishina Valentina (GSI)

QM2018_CBM Akishina poster.pdf

487 TMVA methods to reconstruct $\Lambda_\mathrm{c}\rightarrow \mathrm{pK}^0_\mathrm{S}$ in p--Pb collisions with ALICE at the LHC

Open heavy flavour (charm and beauty) production is one of the leading probes to study the strongly interacting medium that is formed in high-energy heavy-ion collisions. As the charm and beauty quarks have very large mass with respect to the temperature of the medium, they are produced early in initial hard scatterings and not through thermal processes later on.

One particularly interesting observable is the baryon-to-meson ratio, which allows us to better understand hadronisation and thermalisation processes. This can be examined in the heavy-flavour sector by measuring the production ratio of the $\Lambda_\mathrm{c}$ baryon to the $\mathrm{D}^0$ meson.

ALICE's excellent tracking and particle identification capabilities allow it to reconstruct the $\Lambda_\mathrm{c}$ baryon using a variety of methods, including machine learning techniques via the Toolkit for Multivariate Data Analysis (TMVA). This poster will present the latest results for $\Lambda_\mathrm{c}\rightarrow\mathrm{pK}^0_\mathrm{S}$ reconstructed by ALICE with TMVA methods from p--Pb collisions at $\sqrt{s_\mathrm{NN}} = 5.02\,\mathrm{TeV}$, with a view towards future prospects in this field.

Speaker: Jeremy Wilkinson (Universita e INFN, Bologna (IT))

lctmvaposter_qm2018_final.pdf

488 Topological Cut Optimization for Lambda_c Reconstruction Using the Supervised Learning Algorithm in TMVA at STAR

Measurement of charmed baryon, $\Lambda_c$, provides a unique tool to study the charm quark hadronization in the hot and dense medium created in heavy-ion collisions. With the dataset of Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV recorded by the STAR experiment at RHIC in 2014, $\Lambda_c$ signals were successfully reconstructed through the hadronic decay channel ($\Lambda_c\rightarrow pK\pi$) with a 5 $\sigma$ significance. Measurements of better precision of the $\Lambda_c$ production require more statistics and refined topological cut optimization.

In this poster, we will present $\Lambda_c$ reconstruction using the Toolkit for Multi-Variate Data Analysis (TMVA)-Boost Decision Tree (BDT) method with combined data from 2014 and 2016. The improvement in the signal significance is notable compared to previous results using the TMVA-Rectangular Cut Optimization method. We will also discuss the cut optimization for $\Lambda_c$ reconstruction in different transverse momentum and centrality bins with the TMVA-BDT method.

Speaker: Fu Chuan (Central China Normal University)

QM18poster_Lc_optimization.pdf

489 Towards first-principle hydrodynamics for heavy-ion collision phenomenology

Heavy-ion collisions are well described by a dynamical evolution with a long hydro-dynamical phase. In this phase the properties of the strongly correlated quark-gluon plasma are reflected in the equation of state (EoS) and the transport coefficients, most prominently by the shear and bulk viscosities over entropy density ratio $\eta$/s(T) and $\zeta$/s(T), respectively.
While the EoS is by now known to a high accuracy, the transport coefficients and in particular their temperature and density dependence are not known from first-principle computations yet. To remedy this situation we deploy a complementary QCD based approaches to compute $\eta$/s(T) using functional renormalization group to compute gluon real-time spectral functions [1]. In addition we will show the work and progresses of a novel lattice simulation prescription in non-compact imaginary time [2,3], in which the conventional analytic continuation problem is significantly improved.
In this work, these most recent QCD-based parameters are provided as input to the MUSIC framework [4]. The IP-Glasma model is used to describe the initial energy density distribution, and UrQMD the late hadronic phase. Simulations are performed for Pb-Pb collisions at $\sqrt{\rm s_{NN}}$ = 2.76 TeV, for different centrality intervals. The resulting kinematic distributions of the particles produced in the collisions are compared to data from the LHC, for several experimental observables. The high precision of the experimental results and the broad variety of observables considered allow to critically verify the quality of the description based on first-principle input to the hydro-dynamic evolution.

[1] N. Christiansen et.al. PRL 115 (2015) 112002
[2] J. M. Pawlowski and A. Rothkopf arXiv:1610.09531,
[3] J.M. Pawlowski, A. Rothkopf, F.Ziegler (in preparation)
[4] Sangwook Ryu, et al., https://arxiv.org/abs/1704.04216

Speaker: Andrea Dubla (GSI)

QM18PosterADublaMUSIC.pdf

490 Transport coefficient of quark matter

The transport coefficients of quark matter at non-zero chemical potential and temperature are computed within the two-flavor Nambu--Jona-Lasinio model. We apply the Kubo formalism to obtain the thermal and electrical conductivities as well as the shear and bulk viscosity by evaluating the corresponding equilibrium two-point correlation functions to leading order in the 1/N_c expansion. The Dirac structure of the self-energies and spectral functions is taken into account as these are evaluated from the meson-exchange Fock diagrams for on-mass-shell quarks [1,2]. I will also discuss the same transport coefficients in dense color superconducting quark matter [3] on the basis of the Boltzmann equation.

[1] Phys. Rev. D 95, 114021 (2017)
[2] Phys. Rev. D 96, 034006 (2017)
[3] Phys. Rev. C 90, 055205 (2014)

Speaker: Arusyak Harutyunyan

ArusHarutyunyan_poster.pdf

491 Transverse sphericity dependence of di-hadron angular correlations in pp collisions with ALICE at the LHC

Two-particle angular correlations are a useful tool to study the mechanisms of particle production. Different structures in the $(\Delta \eta,\Delta \phi)$ space of the correlation function are caused by various modes of particle production and interactions between particles shortly after production. Examining these structures can give us insight into the nature of these interactions.

Transverse sphericity is a momentum space event shape variable giving a measure of how isotropically particles and their momenta are distributed within an event. This variable allows us to differentiate events containing jets produced in hard processes from those events containing multiple soft, non-perturbative QCD processes.

In this contribution, two-particle angular correlations from pp collisions at $\sqrt{s} =$ 7 TeV are analysed using transverse sphericity and multiplicity to isolate and study different structures in the correlation function.

Speaker: Filip Erhardt (University of Zagreb (HR))

QM2018 poster #521

492 Triple and quadruple GEM detectors for high energy physics experiments

GEM based detectors are now almost an integral part of high energy physics (HEP) experiments. Most of the experiments have, however, used triple GEM detectors. A quadruple GEM detector specially designed for low ion back flow will be used for the readout of the upgraded TPC in ALICE experiment. We present the study of a triple and a quadruple GEM detector and compare their performances in order to understand the usefulness of increasing the number of GEM foils and obtain better operating parameters to suit the requirements of HEP experiments.

The detectors have been assembled in standalone configuration and tested with $^{55}$Fe X-ray and $^{106}$Ru-Rh $\beta$-source using Ar/CO$_2$ gas mixtures with 90:10 and 70:30 proportions. Effective gain and energy resolution have been measured using $^{55}$Fe source. The efficiency is measured using the $^{106}$Ru-Rh $\beta$-source and a coincidence setup consisting of three scintillators. In addition, the uniformity of the gain and energy resolution of the GEM detectors have been investigated by dividing the active area in 7$\times$7 zones.

It was found that quadruple GEM detector operates at less voltage across individual GEM foil ($\Delta$V$_{GEM}$) compared to the triple GEM detector. It is also found that the energy resolution of the detector deteriorates in case of quadruple GEM detector. Time resolution of the detectors is also measured and the obtained value is $\sim$10 – 13 ns at the operating voltage.

We have studied the electron transparency of the quadruple GEM detector with different drift field configurations for understanding the charge transfer phenomena through the GEM foils. An optimum drift field for the maximum transparency is obtained from the results. Garfield simulation studies are in progress for understanding the working phenomena and results of the test.

Speakers: Mr Rajendra Nath Patra (Variable Energy Cyclotron Centre (IN)), Dr Tapan K. Nayak (CERN, Geneva and VECC, Kolkata)

Rajendra_4GEM_QM18_v1.pdf

493 Two-particle correlations in azimuthal angle and pseudorapidity in Be+Be collisions at SPS energies

The NA61/SHINE experiment aims to discover the critical point of strongly interacting matter and study the properties of the onset of deconfinement. These goals are to be achieved by performing a two dimensional phase diagram $(T-\mu_B)$ scan by measurements of hadron production properties in proton-proton, proton-nucleus and nucleus-nucleus interactions. Two-particle correlations in pseudorapidity and azimuthal angle will be presented for Be+Be interactions at beam momenta: 20, 30, 40, 75 and 150 GeV/c per nucleon. The NA61/SHINE results, corrected for detector inefficiencies, will be compared with the already published results from proton-proton collisions at similar beam momenta as well as to predictions of the EPOS model.

Speaker: Bartosz Maksiak (Warsaw University of Technology (PL))

Maksiak_DetaDphi_QM.pdf

494 Two-particle transverse momentum correlations in Pb-Pb collisions at ALICE

Two-particle correlations are powerful tools for studying the medium produced in heavy-ion collisions. In particular, two-particle transverse momentum correlations enable measurements of features of the collision dynamics sensitive to momentum currents. Their evolution with collision centrality, i.e. system life time, provides information about shear viscosity, $\eta$/s, and about system relaxation time, $\tau_{\pi}$. We report on measurements of two-particle transverse momentum correlations in nine centrality intervals from Pb-Pb collisions taken at the LHC with the ALICE detector. The shape of the correlation function is then parametrized once the flow components are suppressed. The collision centrality dependence of the near side peak of the correlation function, most particularly its longitudinal width, provides information about the shear viscosity of the produced medium. Suggested theoretical interpretations are then mapped against the obtained data.

Speaker: Mr Victor Gonzalez (GSI - Helmholtzzentrum fur Schwerionenforschung GmbH (DE))

QMposter_20180510C.pdf

495 Understanding $\gamma$-jet angular correlation and momentum imbalance with QCD resummations.

$\gamma$-jet correlations and their momentum imbalance have been widely regarded as the "Golden probe". Based on our previous studies on dijet, dihadron and hadron-jet angular correlations in $p+p$ and $A+A$ collisions [1,2,3,4], we further employ the systematic Sudakov resummation formalism to study the angular correlation between direct photon and jets as well as their transverse momentum imbalance in both $pp$ and $PbPb$ collisions.

Our results [5] for the $\gamma$-jet angular correlation agree nicely with the ATLAS and CMS data. Since the vacuum Sudakov effects are overwhelmingly larger than QGP medium effects,  we can naturally explain the negligible difference between $pp$ and $PbPb$ data. Furthermore, based on the resummation improved pQCD approach, our calculation for the distribution of $\gamma$-jet transverse momentum imbalance in $pp$ collisions can provide  important predictions for this observable, and can be compared with all LHC data once experimental data are unfolded. In addition, using the $pp$ collision as the baseline, we can also apply BDMPS and High-Twist energy loss formalism to $PbPb$ collisions, and thus extract the jet transport coefficient in the LHC regime.

[1] L. Chen, G. Y. Qin, S. Y. Wei, B. W. Xiao and H. Z. Zhang, Phys. Lett. B 773, 672 (2017).
[2] L. Chen, G. Y. Qin, S. Y. Wei, B. W. Xiao and H. Z. Zhang, arXiv:1612.04202 [hep-ph].
[3] A. H. Mueller, B. Wu, B. W. Xiao and F. Yuan, Phys. Lett. B 763, 208 (2016).
[4] A. H. Mueller, B. Wu, B. W. Xiao and F. Yuan, Phys. Rev. D 95, no. 3, 034007 (2017).
[5]  L. Chen, G. Y. Qin,  L. Wang, S. Y. Wei, B. W. Xiao and H. Z. Zhang, Y.Q. Zhang, in preparation.

Speaker: Mr Lin Chen (Central China Normal University)

poster-gamjet-v1.pdf

496 Understanding phenomenological constraints on the bulk viscosity of QCD

The bulk viscosity of QCD is expected to vary considerably with temperature, from very small values at high temperatures to a possible large peak in the confinement region. Heavy ion collisions present a unique opportunity to establish experimental constraints on this transport coefficient, providing guidance to better understand the response of QCD systems to deviations from equilibrium.

In this work, we undertake a systematic analysis of hadronic observables within a state-of-the-art hydrodynamic model of the quark-gluon plasma, and establish a set of measurements that can constrain the temperature dependence of bulk viscosity. We explicitly show the resilience of these constraints to experimental uncertainties. The temperature dependence of shear viscosity is investigated side-by-side with bulk viscosity for completeness.

We highlight the impact of bulk viscosity on the hadronic chemistry. We further look at different models of initial conditions of the plasma to clarify their effect on phenomenological constraints of bulk viscosity. These results are used to reconcile recent investigations of bulk viscosity in heavy ion collisions [1,2].

[1] J. E. Bernhard, J. S. Moreland, S. A. Bass, J. Liu and U. Heinz, Phys.Rev. C 94, no. 2, 024907 (2016)
[2] S. Ryu, J.-F. Paquet, C. Shen, G. S. Denicol, B. Schenke, S. Jeon and C. Gale, Phys. Rev. Lett. 115, no. 13, 132301 (2015)

Speaker: Prof. Steffen A. Bass (Duke University)

poster_jfpaquet_qm2018_lido.pdf

497 Unequal Rapidity Correlators in the Dilute Limit of JIMWLK

Within the Colour Glass Condensate effective field theory, the JIMWLK equation can also be used to describe the energy evolution of long-range rapidity correlations in nuclear collisions. The projectile interaction with the target classical field is described by Wilson lines. It is useful for numerical implementations to study JIMWLK evolution as a stochastic process. A Langevin equation then governs the evolution of the Wilson lines. I will present a diagrammatic interpretation of the long range rapidity correlators in the Langevin picture. By evolving the classical field in the direct and complex conjugate amplitudes, we have studied the cross section for two-gluon production. In the dilute limit, the rapidity correlations from the Langevin framework map to the transverse momentum correlations that appear in BFKL evolution. This link will give some insight into the interpretation of BFKL evolution as a stochastic process.

Speaker: Andrecia Ramnath (University of Jyvaskyla)

Ramnath_Poster.pdf

498 Universal Scaling of Low Momentum Direct Photon Production in Relativistic Heavy Ion Collisions

Direct photons are an important tool with unique capabilities to study the colored medium created in (ultra)relativistic heavy ion collisions. We map out the low momentum direct photon observables and present the results of the measurements in Au+Au collisions at $\sqrt{s_{NN}} = 62.4$ GeV and $\sqrt{s_{NN}} = 39$ GeV, using data samples of externally converted photons. These results are aimed to further constrain the sources of the low momentum direct photons, in addition to the previous PHENIX measurement results at $\sqrt{s_{NN}} = 200$ GeV. The observed direct photon excess yield at these three collision energies can be interpreted as an evidence of thermal radiation from the Quark Gluon Plasma.

We have found that at low-$p_{T}$ the yield of direct photons, $dN_{\gamma}/dy$, from heavy ion collisions follows a universal scaling as a function of the charged-particle multiplicity $(dN_{ch}/d\eta)^{\alpha}$, where we combine the data from various collision systems at four center-of-mass energies. The prompt photon yield seems to have the similar functional behavior. The observed scaling properties of direct photons from these systems show that the strength of the thermal radiation source increases faster than the charged-particle multiplicity. In this poster we present these new results.

Speaker: Vladimir Khachatryan (Stony Brook University)

Poster_QM2018(1)(1).pdf

499 Upsilon production in p-Pb collisions with ALICE at the LHC

Quarkonia are bound states of a quark and an anti-quark (i.e $c\bar{c}$ or $b\bar{b}$) and are important probes to study the properties of the deconfined medium of quarks and gluons produced in Pb-Pb collisions at LHC. These probes can also be used to study the cold nuclear matter (CNM) effects, like shadowing or gluon saturation, which are related to the modification of the parton distribution functions (PDF), or parton energy loss, which is related to the interaction of the partons with the nuclear matter. These effects can be studied at LHC in p-Pb collisions.

ALICE has reported the inclusive production of $\Upsilon$ in forward (2.03<$y$<3.53) as well as backward (-4.46<$y$<-2.96) rapidity regions with the Muon Spectrometer in p-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 5.02 TeV via $\mu^{+}\mu^{-} $ decay channel. It was found that the CNM effects are smaller for $\Upsilon$(1S) compared to $J/\psi$. In this poster we will present the first ALICE measurement of the differential production cross-section of $\Upsilon$ as a function of transverse momentum ($p_{\rm T}$) and rapidity ($y$) in p-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 8.16 TeV with the Muon Spectrometer. The nuclear modification factor ($R_{AA}$) of $\Upsilon$(1S) as function of $p_{\rm T}$ and $y$ will also be reported.

Speaker: Wadut Shaikh (Saha Institute of Nuclear Physics (IN))

QM2018_Upsilon_pPb8TeV_Wadut.pdf

500 Using femtoscopy to probe the strong interaction for mesons and baryons and their anti-particles in pp and Pb-Pb collisions with ALICE

Understanding the strong interaction between particles is one of the most fundamental problems in nuclear physics. Parameters of this interactions are well-known only for a limited set of particle pairs. Little is known about the cross section of baryon-anti-baryon scattering as well as about the interaction of mesons and baryons with $\Lambda$ or $\Xi$ hyperons.
The ALICE detector has excellent tracking and particle identification capabilities over a broad momentum range which makes a variety of different measurements possible. Femtoscopy, the technique of measuring short-range two-particle correlations as a function of relative momentum, which is traditionally utilized to measure the size of the QGP fireball created in relativistic heavy-ion collisions, can be also used to probe the strong interaction for different meson and baryon pairs.
In this talk we present the results of the femtoscopic analysis of baryon-baryon and baryon-anti-baryon pairs, namely pp, $\rm p\Lambda$, and $\rm \Lambda\Lambda$ pairs in pp collisions at 7 and 13 TeV, as well as $\rm p\bar{p}$, $\rm p\bar{\Lambda}$, and $\Lambda\bar{\Lambda}$ in Pb-Pb collisions at 2.76 and 5.02 TeV. Correlations of $\Lambda$ and $\Xi$ hyperons with charged kaons in Pb-Pb collisions at 2.76 TeV are also discussed. For all studied pairs the strong interaction cross section parameters are extracted and compared to available world data.

Speaker: Jesse Thomas Buxton (Ohio State University (US))

JBuxton_QM18Poster_Final.pdf

501 Using machine learning for data quality assurance, particle identification, and fast simulations in ALICE

Machine learning (ML) is one of the most rapidly evolving fields of computer science. High-energy physics (HEP) with its complex detectors is an ideal place to utilize ML in its full extent. The ALICE experiment is a perfect environment to test the ML capabilities, which can automatize quality assurance (QA), particle identification, as well as perform fast simulations.

QA in ALICE is an important task in order to avoid processing low quality or redundant data, and to classify it for analysis. Currently, human experts are involved in an offline data assessment. This process is time-consuming and it typically takes days, or weeks to assess the quality of the past data taking periods. Furthermore, since after the LHC Long Shutdown 2 upgrades ALICE plans to record data at higher rates, manual data quality checks may not be feasible. We show first attempts of using ML for this purpose.

Monte Carlo (MC) simulations are important ingredients of HEP experiments. They are needed not only to compare experimental data with theory but also to calibrate the detector as well as the reconstruction and analysis software. One of the biggest tasks is propagating each generated particle through the detector medium in order to obtain the correct detector responses. This usually involves the use of Geant or other transport packages which is very time consuming. Generative Adversarial Networks (GAN) can be utilized to provide reconstructed clusters basing on input MC particles with much higher computational speed. We show results of the preliminary approach of using GANs for this purpose in ALICE.

ML can also be used for particle identification. In traditional analysis physicists usually select particles by applying an arbitrary specific selection criteria on certain detector signals, such as the TPC energy loss or TOF arrival time. We show the results of applying ML methods to select particles of interest with maximized efficiency.

Speaker: Dr Lukasz Kamil Graczykowski (Warsaw University of Technology (PL))

QM2018_LukaszGraczykowski.pdf

502 Virtual photon polarization and dilepton anisotropy in relativistic heavy-ion collisions

We present a general framework for studying the angular anisotropy of dileptons produced from polarized virtual photons in relativistic heavy-ion collisions. The spin-anisotropy coefficients characterizing the angular distribution of the dilepton final state are introduced and their dependence on the medium evolution via flow velocity and temperature profiles is obtained. We illustrate these effects in dilepton production from quark-antiquark annihilation in the QGP phase and $\pi^+ \pi^-$ annihilation in the hadronic phase for a static uniform medium and for a longitudinally expanding system. It is shown that the anisotropy coefficients are in general non-zero in a thermalized medium, and depend on the flow of the medium as well as on the transverse momentum and invariant mass of the virtual photon. The present framework can be easily implemented in a realistic hydrodynamic simulation of relativistic heavy-ion collisions in order to study the effect of non-trivial medium properties on dilepton anisotropy.

Speaker: Enrico Speranza (Frankfurt University)

speranza_poster_qm2018_a0.pdf

503 Volume fluctuations in multi-particle flow correlation measurement

Volume fluctuations are background for the event-by-event multiplicity fluctuation analysis, and its effects have been extensively studied for net-proton fluctuations in search of the QGP critical point. In this poster, we show that the two major volume fluctuations effects, centrality bin width and centrality resolution effects, can be probed using flow fluctuation measurements. Using a Glauber model with particle production, we show that the recently observed sign-change of the $c_2\{4\}$ in ultra-central collisions by ATLAS is directly sensitive to the amount of centrality smearing. Therefore the pattern of $c_2\{4\}$ sign-change can be used to quantify the centrality resolution effect. Furthermore, we find that the volume fluctuation effects naturally evolves with rapidity, and therefore the sign-change pattern of $c_2\{4\}$ also expected to evolve with rapidity. We explore new approaches based on flow measurements to constrain the volume fluctuation.

Speaker: Jiangyong Jia (Stony brook Universty (US))

504 Vorticity generation and transmission to polarisation in heavy-ion collisions

We systematically compare the different mechanisms of generation and transmission of vorticity to hyperons polarisation in heavy-ion collisions. The special attention is payed to anomalous mechanism. The transverse and longitudinal components of polarisation are considered. The effects of pionic superfluidity and the emerged quantized vortices is analyzed. The role of polarisation as a probe of properties of quark-gluon matter is studied. The energy dependence of polarisation in the various combination of vorticity generation and transmission mechanisms is addressed.

Speaker: Alexander Sorin (Joint Institute for Nuclear Research (RU))

PowerPoint template for a scientific poster.pdf

505 Rivet as an Experiment-Theory Interface for the Heavy-Ion Community

The comparison of experimental data and theoretical predictions is crucial for our understanding of the mechanisms for particle production in hadron collisions at the LHC. The Rivet (Robust Independent Validation of Experiment and Theory) framework was developed to this purpose and is used as a generator-independent system for event generator validation and tuning. It provides a large set of experimental analysis algorithms together with the published data. Thus, Rivet allows a direct comparison of different generators and experimental data, as well as the preservation of the analysis algorithms used.

Originally developed for validation and tuning of models in high energy physics, Rivet does not fulfil the requirements of many of the heavy-ion analyses, which usually require calibration steps, comparisons of AA and pp collisions, and/or binning in global event observables. This contribution will show extensions made to the Rivet framework in order to adapt to the needs of the heavy-ion analyses. We will show a first prototype of the experiment-theory interface for the ALICE experiment, intended to be used by the whole heavy-ion community.

Speaker: Przemyslaw Karczmarczyk (Warsaw University of Technology (PL))

QM18Poster_ExperimentTheoryInterface_v3.pdf

506 Calculations of coherent photon-nucleus and photon-photon interactions in hadronic A+A collisions at RHIC and LHC

The coherent photon-nucleus and photon-photon interactions has been studied in detail at RHIC and LHC to probe the gluon distribution in nucleus and to test QED via relativistic heavy-ion collisions. These kind of interactions are traditionally thought to only exist in ultra-peripheral collisions, where there is no hadronic interactions. Recently, a significant excess of $J/\psi$ yield at very low transverse momentum ($p_T < 0.3$ GeV/c) was observed by the ALICE and STAR collaborations in peripheral A+A collisions, which points to evidence of coherent photoproduction of $J/\psi$ in violent hadronic interactions. Assuming that the coherent photonuclear production is response for the observed $J/\psi$ excess, the coherent two-photon process should be there and contribute to the dilepton production. According to above, STAR made measurements of $e^{+}e^{-}$ pair production at very low $p_{T}$, and indeed, a significant excess is observed in peripheral collisions. The survival of photoproduced $J/\psi$ and electron pair merits theoretical investigations, which are currently absent on the market.

In this presentation we report on calculations of coherent photon-nucleus ($\gamma + A \rightarrow J/\psi + A$) and photon-photon ($\gamma + \gamma \rightarrow e^{+} + e^{-}$) interactions in hadronic A+A collisions at RHIC and LHC energies. We also address the questions about how the electromagnetic field translates into a flux of equivalent photons in hadronic A+A collisions: if the photons is emitted from the whole nucleus, or if only the spectator fragments contribute to the photon emission. Similarly, for photon-nucleus interactions, it is not clear whether the whole nucleus or only spectator fragment act as photon target. The model used to calculate the cross section will be discussed and the expected yield will be compared with experimental results from RHIC and LHC.

Speaker: Wangmei Zha (USTC/BNL)

QM18poster_Wangmei.pdf

507 Charmonium production in proton-proton collisions with ALICE

Speakers: Tasnuva Chowdhury (Université Clermont Auvergne (FR)), Yanchun Ding (Central China Normal University CCNU (CN))

508 Collision Dynamics near the Critical Point at Strong Coupling

We present the first out-off-equilibirum analysis of relativistic collision dynamics in the vicinity of a critical point. Using holography, we study the collision of ultra-relativistic lumps of energy in a strongly coupled gauge theory with a non-trivial phase diagram which includes a critical point. Choosing collision energies in the vicinity of the critical point, we explore the distribution of matter in the aftermath of the collision. For those energies we observe that independently of the nature of the transition, almost all the energy of the projectiles ends up in a quasi-static, slowly evolving blob of energy. We also observe that this distribution is well described by hydrodynamics, provided specific second order coefficients are taken into account. At least at the level of energy distributions, we observe no distinction in the collision dynamics across the critical point, first order or cross-over transitions.

Speaker: Jorge Casalderrey Solana (University of Oxford)

509 Diffusion of conserved charges in relativistic heavy ion collisions

We present the first calculations of all the diffusion transport coefficients related to the baryon, electric and strangeness charge for a hot and dense hadron resonance gas and for a simplified kinetic model of the quark-gluon plasma [arXiv:1711.08680]. We demonstrate that the diffusion currents do not only depend on gradients of their corresponding charge density. Instead, there exists coupling between the different charge currents, in such a way that it is possible for density gradients of a given charge to generate dissipative currents of another charge. Within this scheme, the charge diffusion coefficient is best viewed as a matrix, in which the diagonal terms correspond to the usual charge diffusion coefficients, while the off-diagonal terms describe the coupling between the different currents. We find that the baryon diffusion current is strongly affected by baryon charge gradients, but also by its coupling to gradients in strangeness. The electric charge diffusion current is found to be strongly affected by electric and strangeness gradients, whereas strangeness currents depend mostly on strange and baryon gradients.

The calculated diffusion coefficients can be easily included in hydrodynamic simulations of heavy ion collisions, and will be particularly important for lower energy collisions such as those that are performed at the RHIC Beam energy scan and that will be performed at NICA or FAIR. We show preliminary hydrodynamic calculations that include the effects of the computed diffusion coefficients.

Reference: Greif, Fotakis,Denicol,Greiner: arXiv:1711.08680

Speaker: Carsten Greiner (University of Frankfurt)

510 Event-by-event cumulants of partonic eccentricity and flow harmonic

We report a comprehensive study on the initial-state partonic eccentricity fluctuation and final-state anisotropic flow fluctuation in Au + Au collisions at 200 GeV using a multiphase transport model. Event-by-event eccentricity and flow anisotropy are characterized by multi-particle cumulants up to fourth order harmonic. Experimental results of azimuthal anisotropy fluctuation by means of cumulants are well reproduced by our model simulation [1]. Results of initial eccentricity and their fluctuations in terms of second-, fourth- and sixth-order cumulants for different order of harmonics as function of centrality, transverse momentum ($p_{T}$) and pseudorapidity ($\eta$) are presented. The ratio of the eccentricities $\varepsilon\left\{4\right\}/\varepsilon\left\{2\right\}$ and $\varepsilon\left\{6\right\}/\varepsilon\left\{4\right\}$ are shown in comparison with the ratio of the corresponding flow harmonics. The conversion coefficients $v_{n}$/$\varepsilon_{n}$ (n=2,3,4) are explored based on the cumulant method. We show that higher harmonic $v_{n}$/$\varepsilon_{n}$ (n$>=$3) show similar trend but exhibit quantitative difference in comparison with $v_{2}$/$\varepsilon_{2}$ [2]. We investigate further the role of partonic and hadronic scatterings in anisotropic flow and flow fluctuation development. We show that collisions between initial active partons are directly responsible for not only the development of anisotropic flow but also flow fluctuation [3]. Relevant physics on the connections between higher-order cumulant eccentricities and flow harmonics is discussed.

References:
[1] L. Ma , G. L. Ma, and Y. G. Ma, Phys. Rev. C 89, 044907 (2014)
[2] L. Ma , G. L. Ma, and Y. G. Ma, Phys. Rev. C 94, 044915 (2016)
[3] L. Ma , G. L. Ma, and Y. G. Ma, in preparation

Speaker: Mr Long Ma (Fudan University)

511 Finite-Size-Finite-Time Scaling of susceptibilities and susceptibility ratios; Implications for the search for the QCD Critical Point

Studies of the fluctuations of conserved charges (baryon number, electric charge, strangeness, etc.) can be used to chart the phases of strongly interacting QCD matter, as well as to locate the critical end-point (CEP) in the associated QCD phase diagram. The cumulants (and cumulant ratios) of the multiplicity distributions for conserved charges, which are linked to susceptibilities and their ratios, are predicted to be sensitive to the growth of fluctuations near the critical point, leading to detectable non-monotonic signatures for the CEP [1]. However, the effects of Finite-Size (FS) and Finite-Time (FT) complicate the search for the CEP, because they nullify the possible non-monotonic patterns, and shift the CEP's location to a so-called pseudo-critical point, different from its genuine location. Alternatively, Finite-Size-Finite-Time scaling (FSFTS) of susceptibilities and susceptibility ratios provide a robust avenue to search for the CEP and to characterize its critical exponents. I will describe the rudiments of FSFTS and present the scaling functions for the inverse compressibility ($\kappa^{-1}$) obtained from both the cumulant ratio $C_1/C_2$) for net-protons, and two-pion HBT radii, measured over a broad range of collision centralities in Au+Au collisions spanning the energy rage $\sqrt{s_{NN}}= 7.7 - 200$ GeV. The location of the CEP and the critical exponents estimated from these disparate measurements will be presented and discussed.

[1] M. Stephanov, PRL 102, 032301 (09)

Speaker: Roy Lacey (Stony Brook University)

512 Locating the QCD critical point using holographic black holes

We use the gauge/gravity duality to map thermodynamic fluctuations of black holes onto fluctuations of baryon charge in a hot and baryon dense Quark-Gluon Plasma (QGP). Our approach gives results that are in quantitative agreement with state-of-the-art lattice simulations for the QCD equation of state at finite baryon density and the moments of fluctuations of baryon charge, while simultaneously encompassing nearly-perfect fluidity. This framework provides a definite prediction for the QCD critical point, which is found to be within the reach of low collision energy experiments at RHIC and also the CBM experiment at FAIR. We also determine the temperature and baryon chemical potential dependence of the bulk viscosity and the coefficients that characterize the transport of baryon charge, electric charge, and strangeness in the QGP.

Speaker: Israel Portillo (University of Houston)

Isra_QM18.pdf

513 PHENIX beam energy and centrality dependence of direct photon emission in heavy ion collisions

Direct photon measurements provide a unique tool to study the strongly
coupled QGP produced in heavy ion collisions and its evolution to hadron resonance matter. PHENIX has observed that a large number of direct photons are radiated during the evolution of the system created in Au+Au collision at 200 GeV, and that the photons are emitted with a large azimuthal anisotropy. The theoretical models of thermal radiation are qualitatively consistent with the data, but the simultaneous observation of large yield and flow strength are difficult to reconcile quantitatively.

In order to provide new insights, PHENIX is analyzing new data from 39, 62.4,
and 200 GeV Au+Au collisions and from Cu+Cu collisions at 200 GeV. We find a new scaling behavior, the photon yield $dN^{\gamma}/d\eta$ is proportional to
$(dN_{ch}/d\eta)^{\alpha}$. The scaling holds for beam energies measured at RHIC and LHC, for centrality selected samples, as well as for different collision systems. In this talk we will discuss these new results and their implications. We will also show updated results on direct photon yields and azimuthal anisotropies $v_2$ and $v_3$ from high statistics Au+Au data at 200 GeV.

Speaker: Axel Drees

Poster_QM2018.pdf

514 Screening masses and static quark free energy at non-zero baryon density from lattice QCD

In the deconfined region of QCD at sufficiently high temperatures or baryon density, the interactions between two static color charges is screened by the medium and this is at the basis of interesting phenomenology, like the dissociation of heavy quark bound states in the Quark-Gluon Plasma. Screening properties have been widely studied in lattice QCD by means of Polyakov loop correlators which, in the deconfined region, allow to probe the properties of the medium and to define gauge-invariant non-perturbative screening masses related to the chromo-electric and chromo-magnetic fields.

In this talk we discuss the extension of electric and magnetic screening masses in the Quark-Gluon Plasma to the case of a finite baryon density. Numerical results are obtained performing lattice QCD simulations at imaginary chemical potential then exploiting analytic continuation, and are presented for $N_f=2+1$ QCD with physical quark masses. As results, we found that both screening masses increase as a function of the baryon density $\mu_B$. In addition, we will also present our determination of the dependence of the static quark free energy on the baryon chemical, showing that it is a decreasing function of $\mu_B$.

Speaker: Andrea Rucci (University of Pisa and INFN)

poster_RUCCI_QM18.pdf

515 Tachyonic instability of the scalar mode prior to the QCD critical point based on the functional renormalization-group method in the two-flavor case

We investigate spectral properties of the collective excitations around the QCD critical point (CP) by applying the functional renormalization-group (FRG) method to the two-flavor quark-meson model with current quark mass $m_q$ being varied. The nature of the CP such as the soft modes is known to be affected by the value of $m_q$: We first determine the whole phase structure in the three-dimensional space $(T, μ, m_q)$ consisting of temperature $T$, quark chemical potential $\mu$ and $m_q$, with the tricritical point, $\mathrm{O}(4)$ and $\mathrm{Z}_2$ critical lines being located; they altogether make a winglike shape quite reminiscent of those known in the condensed matters with a tricritical point. We then calculate the spectral functions in the scalar and pseudoscalar channel around the critical points. We find that the sigma mesonic mode becomes tachyonic with a superluminal velocity at finite momenta before the system reaches the $\mathrm{Z}_2$ point from the lower density, even for $m_q$ smaller than the physical value. One of the possible implications of the appearance of such a tachyonic mode at finite momenta is that the assumed equilibrium state with a uniform chiral condensate is unstable toward a state with an inhomogeneous $\sigma$ condensate. No such anomalous behavior is found in the pseudoscalar channel. We find that the $\sigma$-to-$2\sigma$ coupling due to finite $m_q$ plays an essential role for the drastic modification of the spectral function.

Speaker: Takeru Yokota (Kyoto University, Japan)

QM_poster.pdf

516 Temperature dependence of SU(3)-gluodynamics bulk and shear viscosities within lattice simulation

This talk is devoted to the study of $SU(3)$-gluodynamics bulk and shear viscosities temperature dependence. We measured the correlation functions of the Energy-Momentum Tensor for a set of temperatures in the region $T/T_c \in [0.9, 1.5]$. To extract the values of bulk and shear viscosities from correlation functions we applied various parametrical and non-parametrical approaches which give consistent results. Observed temperature dependence agrees with the recent experimental data. We notice a peak of bulk viscosity in the vicinity of phase transition, as for shear viscosity, there is a slight rise with the temperature at $T > T_c$. The analysis of our data confirms that the quark-gluon plasma behaves as a strongly-interacting system.

Speaker: Nikita Astrakhantsev

517 Testing the QGP properties at finite $\mu_B$ with heavy-ion collisions

The nonequilibrium Parton-Hadron-String-Dynamics (PHSD) transport approach is extended to study the properties of the high-density baryonic matter produced in heavy-ion collisions in the energy range of the actual Beam Energy Scan (BES) program at the Relativistic Heavy Ion Collider (RHIC), of the future Facility for Antiproton and Ion Research (FAIR) and of the Nuclotron-based Ion Collider fAсility (NICA) experiments. With the help of the Dynamical QuasiParticle Model (DQPM) that provides the parton properties at finite temperature ($T$) and baryonic chemical potential ($\mu_B$) in line with the available lattice QCD (lQCD) results, we are able to describe the dynamics of heavy-ion collision in a consistent manner and to study the properties of the Quark-Gluon Plasma (QGP) in the whole range of collisional energy. We analyze the effects of a baryon-rich medium on the relevant observables compared with the available experimental data. We finally discuss the different regions probed in the ($T-\mu_B$) plane by the QGP phase and the perspectives to identify a possible critical point in the phase diagram.

Speaker: Pierre Moreau (Frankfurt Institute of Advanced Studies)

P.Moreau_QM2018.pdf

518 The anisotropic non-equilibrium hydrodynamic attractor

We determine the dynamical attractor associated with anisotropic hydrodynamics (aHydro) for a system undergoing Bjorken flow and compare our results to the corresponding attractor obtained from exact solution of the Boltzmann equation, Navier-Stokes theory, and two second-order viscous hydrodynamics theories (Mueller-Israel-Stewart and Denicol-Niemi-Molnar-Rischke). We demonstrate that the aHydro attractor is virtually indistinguishable from the exact attractor and show that the success of aHydro in reproducing the exact attractor solution stems from the fact that in this approach there is a resummation in both gradients (Knudsen number ${-}$ $Kn$) and inverse Reynolds number ($R_\pi^{-1}$). This allows aHydro to be applied at much higher inverse Reynolds numbers than traditional hydrodynamic approaches. We close by discussing the implications for heavy-ion collision modeling.

Speaker: Michael Strickland (Kent State University)

strickland.pdf

519 The many onsets of NA61/SHINE

NA61/SHINE is a fixed target experiment operating at the CERN Super-Proton-Synchrotron (SPS). The main goal of the experiment is the study of the phase diagram of strongly interacting matter. This goal is pursued by performing a two-dimensional scan by varying the beam momentum (13A-158A GeV/c) and the system size (p+p, Be+Be, Ar+Sc, Xe+La, Pb+Pb) of the collisions.

The properties of strangeness production show nontrivial dependence on the beam momentum. This dependence is interpreted as the onset of deconfinement. The prediction of theoretical models will be compared with the measured data.

A new effect, onset of fireball, is indicated by the unexpected similarity between p+p and Be+Be data. Collisions of the light systems can be treated as a superposition of nucleon-nucleon collisions. However, a rapid qualitative change of the value of various observables occurs when colliding heavier systems. This may indicate another threshold behaviour of strongly interacting matter.

The theoretical models SMES and PHSD describe the onset of deconfinement in the heaviest system relatively well. However, no model describes the behaviour of the data in previously unmeasured collisions of light and intermediate size ions. The onset of fireball is not described by models at all.

Speaker: Emil Aleksander Kaptur (University of Silesia (PL))

520 Dimuon Invariant Mass Spectra with the Muon Telescope Detector at STAR in p+p collisions at 200 GeV

Dileptons ($l^+l^-$) are produced throughout all stages of heavy-ion collisions (HIC) through various production mechanisms. Since leptons have a small interaction cross section with the strongly interacting medium, they carry information about the medium from the early stages to the final state of the system. For this reason, dileptons provide an essential tool for studying the properties of the strongly interacting medium produced in HICs. Dileptons produced within the intermediate mass region (IMR, $M_\phi$<$M_{ll}$<$M_{J/\psi}$) result predominantly from the decay of correlated charm but also arise from thermal radiation of the hot and dense medium. The inverse slope parameter of the thermally produced dileptons in the IMR provides a measurement of the medium's temperature at early times which is free from radial flow effects [1]. The installation of the Muon Telescope Detector (MTD) at STAR allows a measurement of the dimuon ($\mu^+\mu^-$) production over a large invariant mass range for the first time. Data has been collected with the full MTD from Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV and from p+p collisions at $\sqrt{s}$ = 200 GeV. These two datasets allow for new opportunities to measure the dimuon invariant mass spectra at STAR.

As a first step towards measuring the thermal dimuon invariant mass spectra in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV, this talk will present the baseline dimuon measurement in p+p collisions at $\sqrt{s}$ = 200 GeV. The dimuon invariant mass spectra in p+p collisions at $\sqrt{s}$ = 200 GeV will be presented and the viability of measurements in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV will be discussed.

Reference
[1] R. Rapp and H. van Hees, Phys. Lett. B753, 586 (2016).

Speaker: James Brandenburg (Rice University)

jdb_QM18poster_final.pdf

521 Direct flow of heavy mesons as unique probes of the initial Electro-Magnetic fields in Ultra-Relativistic Heavy Ion collisions

In Ultra-relativistic Heavy-Ion Collision (HIC) very strong initial electro-magnetic (e.m.) fields are created inducing a vorticity in the reaction plane that is odd under charge exchange, allowing to distinguish it from the large vorticity of the bulk matter due to the initial angular momentum conservation. Conjointly thanks to its mass, $M_{b,c}>>\Lambda_{QCD}$, there should be no mixing with the chiral magnetic dynamics. We show that such e.m. field entails a transverse motion of both heavy quarks (HQ), bottom and charm, resulting in a splitting of directed flow $v_1$ of D(B) and anti-D (anti-B) of few percent, i.e. much larger compared to pions. The considerable effect is due to a combination of several favorable conditions for HQ, mainly: (i) unlike light quarks formation time scale of HQ is comparable to the time scale when the e.m. field attains its maximum value and (ii) the kinetic relaxation time is similar to the QGP lifetime, which allows the HQ to retain the initial kick picked up from the electromagnetic field in the transverse direction. Hence HQs provide very crucial and independent information on the strength of the electro-magnetic field produced in HIC,
moreover the effect comes out of a delicate balance between the magnetic and the electric field supplying a novel probe of the electric conductivity of the QGP. Moreover, the impact of a Langevin vs a Boltzmann transport of HQ in the medium is also investigated.

[1] S. K. Das, S. Plumari, S. Chatterjee, J. Alam, F. Scardina, V. Greco, Phys.Lett. B768 (2017) 260.
[2] F. Scardina, S. K. Das, V. Minissale, S. Plumari, V. Greco, Phys.Rev. C96 (2017) no.4, 044905.
[3] S. K. Das, F. Scardina, S. Plumari, V. Greco, Phys.Lett. B747 (2015) 260.
[4] F. Scardina, D. Perricone, S. Plumari, M. Ruggieri, V. Greco, Phys.Rev. C90 (2014) no.5, 054904.

Speaker: Mr Gabriele Coci (INFN - National Institute for Nuclear Physics)

CociG_posterQM18.pdf

522 Direct photon production at low pT in small systems with ALICE

Measurements of low $p_{\rm T}$ direct photon production at midrapidity in pp collisions at $\sqrt{s}=2.76$ and 8 TeV, as well as in p-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV were carried out by the ALICE experiment at the LHC. Photons were detected with either of the two electromagnetic calorimeters, EMCal and PHOS, and via reconstruction of $e^+e^-$ pairs from conversions in the ALICE detector material using the central tracking system. Where possible the results were combined for the inclusive photon spectra. An additional hybrid method, combining the conversion information with that of the calorimeters, was included in our best estimate of the direct photon excess ratio $R_{\gamma}$, as well as the extraction of direct photon spectra or their upper limits. Below $3$ GeV/$c$, $R_\gamma$ was found to be consistent with unity in all of the investigated collision systems. Furthermore, the direct photon spectra will be compared to pQCD next-to-leading order calculations.

Speaker: Mike Henry Petrus Sas (Nikhef National institute for subatomic physics (NL))

Direct_Photon_Flow_ALICE_msas.pdf

523 Energy dependence of $\phi (1020)$ production at mid-rapidity in pp collisions with ALICE at the LHC

Hadronic resonances are unique tools to investigate the interplay of re-scattering and regeneration effects in the hadronic phase of heavy-ion collisions. As the $\phi$ meson has a longer lifetime compared to other resonances, it is expected that its production will not be affected by regeneration and re-scattering processes. Measurements in small collision systems such as proton-proton (pp) collisions provide a necessary baseline for heavy-ion data and they help to tune pQCD inspired event generators. Being an $\mathrm{s\bar{s}}$ quark pair with zero net-strangeness content, measurements of $\phi$ meson production contribute to the study of strangeness production in small systems.

We report on measurements with the ALICE detector at the LHC of $\phi$ meson production in minimum bias pp collisions at different beam energies and as a function of charged particle multiplicity. The results include the transverse momentum $(p_{\mathrm{T}})$ distributions of $\phi$ as well as the $\langle p_{\mathrm{T}}\rangle$ values and particle yield ratios. The key question that will be addressed is whether there is a dependence of the relative $\phi$ production in pp collisions on the collision energy.

Speaker: Mr Sushanta Tripathy (Indian Institute of Technology Indore (IN))

Energy_dependence_phi.pdf

524 Equation of state for QCD with a critical point from the 3D Ising Model

Currently, one of the major investigations in heavy ion physics concerns the search for the QCD high temperature critical
point associated with the chiral transition, which has stimulated tremendous effort from both theory and experiment. On the theory side, a major role in the analysis of experimental results is played by hydrodynamical simulations of heavy ion collisions, which need as an input an equation of state driving the evolution of the system. Current knowledge of the finite-density QCD equation of state from first principles is limited to a Taylor expansion in the baryonic chemical potential around $\mu_B = 0$.

By means of a scaling form for the equation of state of the 3D Ising model and a non-universal, parametrized map to QCD coordinates, we construct an equation of state matching state of the art first principle Lattice QCD calculations and including the correct critical behavior, which can be readily employed in hydrodynamical simulations of heavy ion collisions at finite density, covering most of the BES range at RHIC.

The parametrized form of this equation of state can be exploited to constrain the value of the parameters themselves by imposing thermodynamic consistency and through comparison of predictions obtained by simulations with experimental results.

This contribution reports on work done within the Fluctuations/Equation of State working group of the BEST Collaboration.

Speaker: Paolo Parotto (University of Houston)

Poster_Parotto_QM18.pdf

525 f0(980) resonance production in pp collisions with the ALICE detector at LHC

We report on a preliminary study of the production of f$_{0}$(980)$\rightarrow \pi^{+}\pi^{-}$ at mid-rapidity ($\vert y \vert$ < 0.5) performed with the ALICE detector at the LHC in minimum bias pp collisions at centre-of-mass energy $\sqrt{\mathit{s}}$ = 5.02 TeV. The f$_{0}$(980) signal extraction is challenging due to the large background from correlated $\pi^{+}\pi^{-}$ pairs from resonance decays in the invariant mass window under study, as well as due to the combinatorics from uncorrelated pairs. We present in detail the strategy followed for the signal extraction and first results in terms of $p_{\mathrm{T}}$-dependent production yields. Results are discussed and compared with production yields of other resonances and stable hadrons.
Short-lived hadronic resonances are a useful sampling tool for the late hadronic phase of ultra-relativistic heavy-ion collisions since their lifetimes are of the same order of magnitude as the time span between the chemical and kinetic freeze-out, tipically estimated to be about 10 fm/$c$ for central collisions. Our study in pp collisions provides a feasibility check and constitutes a reference for the measurement in high-multiplicity events (p-Pb, Pb-Pb).
The nature of the f$_0$(980) remains elusive: different interpretation of this resonance including $q\bar{q}$ states, bound states of hadrons such as $K\bar{K}$, and as tetraquark candidate are available. Studies in different collision systems are particularly interesting because they can provide information about the nature of this particle.

Speaker: Alessandra Lorenzo (Universita e INFN, Bologna (IT))

AL_posterQM_v07.pdf

526 J/psi in jets in pp collisions at 5.02 TeV with the CMS experiment

The extent to which J/psi mesons are accompanied by other particles within the same jet provides information about how the J/psi is formed, which is still not completely understood. The details of J/psi production may have important consequences for their interaction with the quark-gluon plasma. We present a study of jets containing a J/psi in pp collisions at 5 TeV with the CMS experiment. The fraction of the jets momentum carried by the J/psi is compared to models.

Speaker: Batoul Diab (Centre National de la Recherche Scientifique (FR))

BatoulDiabHIN18012Poster.pdf

527 Measurement of jet fragmentation in $pp$, $p$+Pb and Pb+Pb collisions with ATLAS

The measurement of the fragmentation functions of jets into charged particles in heavy ion collisions can provide insight into the mechanism of the modification of the parton shower in the hot, dense QCD medium created in these collisions. Additionally, a study of the jet fragmentation in $p$+Pb collisions, where a large volume of hot QCD matter is not expected to be created, can provide insight into a possible influence on the jet fragmentation by effects due to the participation of the nucleus in the collision. This poster presents the latest measurements of fragmentation functions in $pp$, $p$+Pb, and Pb+Pb collisions by the ATLAS experiment using data from the LHC Run 2.

Speaker: Akshat Puri (Univ. Illinois at Urbana Champaign (US))

poster_final.pdf

528 Non-linear dynamical systems approach to out of equilibrium hydrodynamical attractors: the Gubser flow case

Attractors for relativistic hydrodynamics have been found recently in weakly and strong coupling physical systems. The existence of hydrodynamical attractor provides a firm theoretical foundation for the applicability of hydrodynamics in far-from-equilibrium conditions. In this work we explain how the non-equilibrium attractors of systems undergoing Gubser flow within relativistic kinetic theory can be established on general grounds by using methods of nonlinear dynamical systems. Namely we find the fixed points and investigate the structure of flow diagrams of the evolution equations and characterize the basin of attraction using a Lyapunov function near the stable fixed point. We obtain the attractors of anisotropic hydrodynamics, Israel-Stewart (IS) and transient fluid (DNMR) theories and show that they are indeed non-planar and the basin of attraction is essentially three dimensional. The attractors of each hydrodynamical model are compared with the one obtained from the exact Gubser solution of the Boltzmann equation within the relaxation time approximation. We observe that the anisotropic hydrodynamics is able to match up to high numerical accuracy the attractor of the exact solution while the second order hydrodynamical theories fail to describe it. Our findings indicate that anisotropic hydrodynamics is an effective theory for far-from-equilibrium fluid dynamics which resums the Knudsen and inverse Reynolds numbers to all orders.

Speaker: Mr Nikolás Cruz Camacho (Universidad Nacional de Colombia)

posterQM2018.pdf

529 The curvature of the pseudocritical line from lattice QCD: Taylor expansion and Analytic continuation compared

The $T-\mu$ phase diagram of QCD is, both theoretically
and experimentally, still largely unknown.
On the theoretical side, lattice QCD is the only reliable
tool to investigate the region close to the $\mu=0$ axis.
I will present our determinations of the curvature of the chiral
pseudocritical line from $N_f=2+1$ lattice QCD at the physical point
as obtained by adopting different approaches.
I will directly compare the method of the analytic continuation
from imaginary chemical potential with the method of Taylor expansion.

Speaker: Francesco Negro (INFN - Sezione di Pisa)

Negro_qm2018.pdf

Concert

concert_programme.pdf

Wednesday, 16 May

Chirality, vorticity and polarisation effects: II

Convener: Alexander Sorin (Joint Institute for Nuclear Research (RU))

530 Search for the chiral magnetic effect at the LHC with the CMS experiment

Searches for the chiral magnetic effect (CME) using charge-dependent azimuthal correlations with respect to event planes are presented in PbPb collisions at 5.02 TeV and pPb collisions at 5.02 and 8.16 TeV, with the CMS experiment at the LHC. The azimuthal correlations with respect to the second- and third-order event planes are explored as a function of pseudorapidity, transverse momentum, and event multiplicity, which provides new insights into the underlying background correlations. By employing an event-shape engineering technique, a linear dependence of charge-dependent correlations on the second-order anisotropy flow (v2) is observed, and the upper limits on the v2-independent fraction, which is directly related to the CME signal, are obtained at 95% confidence level for both pPb and PbPb collisions. These results provide strong constraints on the search for the chiral magnetic effect at LHC energies, and establish new guidelines for searches in future experiments.

Speaker: Zhoudunming Tu (Rice University (US))

QM18-kong-CME-05162018v1.pdf

531 Re-examining the premise of isobaric collisions and a novel method to measure the chiral magnetic effect

Due to the topology of QCD vacuum, a strong magnetic field can lead to an electric current, or charge separation in heavy ion collisions, a phenomenon called chiral magnetic effect (CME). Finite azimuthal correlator ($\Delta\gamma$) signals have been measured in experiments, consistent with the CME, but contaminated by a major elliptic flow ($v_{2}$) induced background. The isobaric $_{44}^{96}$Ru+$_{44}^{96}$Ru and $_{40}^{96}$Zr+$_{40}^{96}$Zr collisions have been proposed and planned at RHIC in 2018 to search for the CME with their expected 15% signal difference and almost identical backgrounds. In this talk we will show, however, that these expectations may not hold as originally anticipated due to large uncertainties in the isobaric nuclear structures [1]. We demonstrate this using Woods-Saxon densities and the proton and neutron densities calculated by the density functional theory and the nuclear shell model. Furthermore, a novel method is proposed to gauge background and possible CME contributions in the same system, intrinsically better than the isobaric collisions of two different systems [2]. The new method is based on the opposite behaviors in the fluctuations of the magnetic field and $v_{2}$ in a single nucleus-nucleus collision, thus bears minimal theoretical and experimental uncertainties. We illustrate the method with Monte Carlo Glauber and AMPT (A Multi-Phase Transport) simulations.

References:
[1]. Hao-jie Xu, Xiaobao Wang, Hanlin Li, Jie Zhao, B. Alex Brown, Zi-Wei Lin, Caiwan Shen, and Fuqiang Wang, Importance of isobar density distributions on the chiral magnetic effect search, arXiv:1710.03086.
[2]. Hao-jie Xu, Jie Zhao, Xiaobao Wang, Hanlin Li, Zi-Wei Lin, Caiwan Shen, and Fuqiang Wang, Varying the chiral magnetic effect relative to flow in a single nucleus-nucleus collision, arXiv:1710.07265.

Speaker: Dr Haojie Xu (Huzhou University)

precentation.pdf

532 Measurements of the Chiral Magnetic Effect with Background Isolation in 200 GeV Au+Au Collisions at STAR

Using two novel methods, pair invariant mass ($m_{inv}$) [1] and comparative measurements with respect to reaction plane ($\psi_{\rm RP}$) and participant plane ($\psi_{\rm PP}$) [2], we isolate the chiral magnetic effect (CME) from backgrounds in 200 GeV Au+Au collisions at STAR.

The invariant mass method identifies the resonance background contributions, coupled with the elliptic flow ($v_{2}$), to the charge correlator CME observable ($\Delta\gamma$). At high mass ($m_{inv}>1.5$ GeV/$c^{2}$) where resonance contribution is small, $\Delta\gamma$ is found to be consistent with zero within uncertainty. In the low mass region ($m_{inv}<1.5$ GeV/$c^{2}$), resonance peaks are observed in $\Delta\gamma$ as function of $m_{inv}$. A two-component model fit is devised to extract the CME signal, assumed smooth in $m_{inv}$.

In the comparative method, the $\psi_{\rm RP}$ is assessed by spectator neutrons measured by the ZDC, and the $\psi_{\rm PP}$ by the 2nd harmonic event plane measured by TPC. The $v_{2}$ is stronger along $\psi_{\rm PP}$ and weaker along $\psi_{\rm RP}$; in contrast, the magnetic field, being from spectator protons, is weaker along $\psi_{\rm PP}$ and stronger along $\psi_{\rm RP}$. As a result the $\Delta\gamma$ measured with respect to $\psi_{\rm RP}$ and $\psi_{\rm PP}$ contain different amounts of CME and background, and can thus determine these two contributions. We report the results from this determination.

References
[1] J. Zhao, H. Li, F. Wang, arXiv:1705.05410 (2017).
[2] H. Xu, J. Zhao, X. Wang, H. Li, Z. Lin, C. Shen, F. Wang, arXiv:1710.07265 (2017).

Speaker: Jie Zhao (Purdue University)

QM2018_JieZhao.pdf

533 Quantitative Predictions for the Chiral Magnetic Effect with Event-By-Event Anomalous Viscous Fluid Dynamics from AuAu to Isobaric Collisions at RHIC

Chiral Magnetic Effect (CME) is the macroscopic manifestation of the fundamental chiral anomaly in a many-body system of chiral fermions, and emerges as a generic anomalous transport current in the hydrodynamic framework. The study of CME has attracted significant recent interest across many disciplines from condensed matter to nuclear physics. An experimental observation of CME in heavy ion collisions would further provide the tantalizing evidence for the chiral symmetry restoration as well as QCD topological fluctuations. Currently the most pressing theoretical challenge is the quantitative modeling of CME while also accounting for background contamination. We report a significant step forward toward this goal, by the development of the full-fledged Event-By-Event Anomalous Viscous Fluid Dynamics (EBE-AVFD) framework. The EBE-AVFD starts with event-wise initial conditions for the bulk+axial charge+magnetic fields, simulates the evolution of fermion currents in QGP on top of the bulk fluid evolution from either VISHNU or MUSIC (both being validated with extensive soft observable data) on an event-by-event basis, to be followed by an event-wise URQMD hadron cascade stage. The millions of simulation events would then be analyzed with the same observables and methods as the experimental analysis. We show systematic computation results for charge-dependent azimuthal correlations in CuCu, AuAu and UU collisions at RHIC, to be compared with available experimental data. After such verification step, we finally present the state-of-the-art quantitative predictions for the CME signals in isobaric collisions (RuRu v.s. ZrZr), which will provide the most critical test of the CME in heavy ion collisions.
[Refs: arXiv:1711.02496; arXiv:1712.01386; CPC42(2018)011001 (arXiv:1611.04586); NPA967(2017)748 (arXiv:1704.05531); Shi and Liao, in preparation]

Speaker: Jinfeng Liao (Indiana University)

LIAO_AVFD_QM18.pdf

534 ALICE constraints on the chiral magnetic effect from charge-dependent azimuthal correlations with identified hadrons

The strong magnetic field generated by colliding nuclei could create a current in the QGP medium resulting in charge separation along the direction of the magnetic field which is perpendicular to the reaction plane. This phenomenon is called the chiral magnetic effect (CME). Initial studies by ALICE showed that the magnitude of the three particle correlator used in the search for the CME is comparable at the LHC and at RHIC. Recent results from the ALICE and CMS experiments have shown that the magnitude of these correlators are similar in Pb-Pb and p-Pb collisions for events with similar multiplicity, which indicates that the measured correlations are dominated by effects not related to the magnetic field and the CME.
We present results for two- and three-particle correlations measured for identified ($\pi$, K, p) hadrons and for different order harmonics relative to various symmetry planes ($\Psi_n$), estimated using the forward detectors of ALICE, for Pb-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV. The measurements are presented as a function of centrality as well as differentially with respect to the pair separation in rapidity and average pair transverse momentum. The results are compared with similar measurements reported previously by ALICE at the lower energy $\sqrt{s_{NN}}$ = 2.76 TeV and recent studies from the CMS Collaboration.

Speaker: Dr Rihan Haque (Nikhef National institute for subatomic physics (NL))

ALICE_CME_Run2_QM2018.pdf

Jet modifications and high-pT hadrons: III

Convener: Gunther Roland (MIT)

535 PHENIX results on jet modification with $\pi^0$- and photon-triggered two particle correlations in p+p, p(d)+Au, and Au(Cu)+Au collisions

As a colorless probe, direct photons balance the $p_T$ of the away-side jet at
leading order. Direct photon-hadron correlations are thus an excellent probe for
nuclear structure and QCD effects, including parton energy loss in the
Quark-Gluon Plasma.

PHENIX has measured $\pi^0$ and direct photon-triggered two-particle azimuthal
correlations in a variety of collision systems ranging from p+p to Au+Au at 200
GeV. In p+Au and d+Au collisions, no modification of the per-trigger jet yield or
away-side correlation width compared to p+p collisions is observed for direct
photon triggered correlations while an increase in the away-side width for
$\pi^0$ triggered correlations in p+Au has been measured. In Au+Au and Cu+Au collisions, direct photons have been identified statistically as well as using an isolation cut. Combining data sets from different collision systems allows us to quantify the transition from suppression at high
$z_T$ ($p_{T,h}/p_{T,gamma}$) to the enhancement of low $z_T$ particles relative to p+p, and to study this transition as a function of trigger $p_T$. The implication for our understanding of cold and hot nuclear matter from these measurements will be discussed.

Speaker: Joseph Osborn (University of Michigan)

PHENIX_correlations_QM18.pdf

536 Photon-tagged measurements of jet quenching with the ATLAS detector

Events containing a high transverse momentum ($p_\mathrm{T}$) prompt photon offer a useful tool to study the dynamics of the hot, dense medium produced in heavy ion collisions. Because photons do not carry color charge, they are unaffected by the medium, and thus provide information about the momentum, direction, and flavor (quark or gluon) of the associated hard-scattered parton before it begins to shower and become quenched. In particular, the presence of a high-$p_\mathrm{T}$ photon can be used to select $pp$ and Pb+Pb events with the same configuration before quenching, limiting the effects of selection biases present in other jet measurements. The large statistics $pp$ and Pb+Pb data delivered by the LHC in 2015 thus allow for a detailed study of photon-tagged jet quenching effects, such as the overall parton energy loss and modified structure of the component of the shower which remains correlated with the initial parton direction (e.g. in cone). These can be explored as a function of photon $p_\mathrm{T}$, centrality, and reaction plane. In this talk, the latest status of photon-tagged jet measurements in ATLAS will be presented, including a new measurement of how the fragmentation function for jets in photon-tagged events is modified. This measurement in particular reveals a non-trivial difference relative to the analogous observable for inclusive jets.

Speaker: Dennis Perepelitsa (University of Colorado Boulder)

dvp-QM18-5-16-18.pdf

537 Jet quenching in Z/W+jet in heavy-ion collisions

Gauge boson tagged jet production has long be regarded as a "golden channel" to study the jet quenching effect. Recently, the back-to-back azimuthal alignment $\Delta\phi_{jZ}$, $p_T$ asymmetry $x_{jZ}$ distribution and its mean value, as well as the average number of jet partners per Z boson $R_{jZ}$ of Z associated jet production have been reported in both pp and Pb-Pb collisions by CMS.

In the talk, we report the theoretical calculations of Z/W+jet production in pp and Pb-Pb at the LHC, which are confronted with all available data and very nice agreements between theory and data are observed for all four observables of Z+jet in both pp and Pb-Pb collisions. In the model, a very good description of Z+jet in pp is achieved by utilizing Sherpa, which combines the NLO with resummation by a matched parton shower (PS). To compute observables of Z+jet in Pb-Pb we consider the parton energy loss in hot/dense QCD medium, which is simulated by Linear Boltzmann Transport(LBT) model. Our calculations of distributions of $\Delta\phi_{jZ}$ and $R_{jZ}$ can give excellent descriptions of CMS measurements both in pp and Pb-Pb for the first time. Compared to pp collisions, $R_{jZ}$ is suppressed and smaller fraction of jets is lost for larger initial jet parton energy in Pb-Pb collisions. The distribution of $\Delta\phi_{jZ}$ at large azimuthal angle in Pb-Pb is suppressed relative to that in pp, because jet quenching effect will reduce the contributions of multiple-parton processes. We evaluate the transverse momentum imbalance $x_{jZ}$ simultaneously which is broadened and shifted to lower value, and we find a very good agreement with LHC data for both $x_{jZ}$ distribution and its mean value. Predictions for several observables of W+jet in pp and Pb-Pb collisions are also presented for completeness.

Speaker: Shanliang Zhang

QM2018_ZSLV10.pdf.pdf

538 Electroweak probes of small and large systems with the ATLAS detector

Measurements of isolated prompt photon and massive electroweak (W and Z) boson production in different collision systems are of great interest to understanding the partonic structure of heavy nuclei, and serve as a constraint on the initial state in larger collision systems. These channels are sensitive to a variety of effects such as the modification of the parton densities in nuclei in certain kinematic regions, and the energy loss of partons as they undergo multiple interactions in the nucleus before the hard parton-parton scattering. High-statistics samples of lead--lead and proton--lead collision data at $\sqrt{s_{_{\rm{NN}}}}=5.02$ TeV and 8.16 TeV, respectively, taken by the ATLAS experiment, as well as proton--proton comparison data at analogous collision energies, allow for a detailed study of these phenomena in data and comprehensive comparisons to the predictions of a variety of theoretical approaches. This talk presents the latest ATLAS results in these topics, including updated results on inclusive prompt photon production in proton--lead collisions over a broad kinematic range and high-precision W boson results in lead--lead collisions.

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

QM_zcitron_olp.pdf

539 Systematic Studies of Jet-medium Interactions in STAR

Recent STAR's jet physics results in heavy-ion collisions will be reported in this talk. Coincidence measurements of semi-inclusive jets recoiling from high-$p_T$ hadrons or direct photons will be presented to offer constraints on path length and flavor dependence of energy loss. Di-jets selected with a constituent cut of 2 GeV/$c$ showed significant transverse momentum imbalance which could be recovered from soft constituents to the level of p+p collisions within the original $R=0.4$ cone. Di-hadron correlation measurements with a method to subtract all orders of flow background using data themselves will also be presented to study how the lost energy is redistributed at low to modest $p_T$. We will contextualize and discuss recent and new systematic studies of jet coincidence and correlation measurements at STAR, taking advantage of the tenfold increase in statistics from recent data taking runs.

Speaker: Kun Jiang (University of Science and Technology of China and Purdue University)

QM18_0516_2018_Kun.pdf

New theoretical developments: I

Convener: Sangyong Jeon (McGill University)

540 Anomlaous hydrodynamics from projection operator method

Anomalous hydrodynamics is a low-energy effective theory that captures anomaly-induced transport such as the chiral magnetic effect. Although there are several derivations of anomalous hydrodynamic equation from microscopic quantum theory, it has been unclear how we can derive it based on the operator formalism of quantum theory. In this study, we derive anomalous hydrodynamic equation based on so-called Mori's projection operator method, which provides a systematic way to derive the equation of motion for slow variables like conserved charge densities in hydrodynamics. The vital point for Mori's projection operator method is that it gives a generalization of the current algebra technique used in low-energy hadron dynamics of the QCD vacuum to the nonequilibrium situations. As a result, we find that the chiral magnetic effect is caused by the anomalous commutation relation between vector and axial charge densities which represents a manifestation of the quantum anomaly in the operator formalism. We further discuss an extension of our derivation to the symmetry-broken phase which brings about anomalous superfluid hydrodynamics.

Speaker: Masaru Hongo (RIKEN)

180516-QM2018-hongo.pdf

541 Hydrodynamization and Attractors at Intermediate Coupling

The tremendous success of hydrodynamics in describing the Quark-Gluon Plasma poses many challenges to our understanding of collective phenomena in interacting systems out of equilibrium. Recently the concept of hydrodynamic attractors, which generalize the gradient expansion beyond local thermal equilibrium, has been put forward. In this talk we will present the first analysis of this configuration at intermediate coupling. Using holography, we resum large orders in the gradient expansion to constrain the hydrodynamization dynamics and the attractor beyond the strong coupling limit. We find that independent of the coupling, hydrodynamization occurs at early times where the pressure anisotropies are large, and that the attractor is determined by first order hydrodynamics. By comparing our results to kinetic theory, we also observe that the approach of different configurations to the attractor is faster in gravity/based computations than in an extrapolation of kinetic theory to intermediate coupling.

Speaker: Ben Meiring (University of Oxford)

intermediate_coupling_attractors.pdf

542 Analytical solutions of causal relativistic hydrodynamic equations for Bjorken and Gubser flow

Bjorken and Gubser flow profiles are well known analytic solutions for relativistic Navier-Stokes equations. Recently several attempts have been made to obtain analytic solutions for relativistic second-order dissipative hydrodynamic equations with Bjorken and Gubser flow. We obtain general analytical solutions, for these flow profiles, up to third-order viscous hydrodynamic equations for a system with vanishing bulk viscosity and chemical potential, and having a constant shear relaxation time. We also analytically determine the hydrodynamic attractors for such systems by studying the universal behavior of these solutions at late times where all informations about the initial conditions are lost. Finally we discuss the properties of these hydrodynamic attractors for transport coefficients obtained from relativistic kinetic theory in the relaxation-time approximation.

Speaker: Chandrodoy Chattopadhyay (Tata Institute of Fundamental Research)

QM_talk.pdf

543 (3+1)D Viscous Anisotropic Hydrodynamics for Nonconformal Fluids

Anisotropic hydrodynamics improves upon standard dissipative fluid dynamics by treating certain large dissipative corrections non-perturbatively. Relativistic heavy-ion collisions feature two such large dissipative effects: (i) Strongly anisotropic expansion generates a large shear stress component which manifests itself in very different longitudinal and transverse pressures, especially at early times. (ii) Critical fluctuations near the quark-hadron phase transition lead to a large bulk viscous pressure on the conversion surface between hydrodynamics and a microscopic hadronic cascade description of the final collision stage.

We present a new dissipative hydrodynamic formulation for non-conformal fluids where both of these effects are treated nonperturbatively. The evolution equations are derived from the Boltzmann equation in the 14-moment approximation, using an expansion around an anisotropic leading-order distribution function with two momentum-space deformation parameters, accounting for the longitudinal and transverse pressures. Generalized Landau matching conditions for the longitudinal and transverse pressures are then required to obtain their evolution. We describe an approximate anisotropic equation of state that relates the anisotropy parameters with the macroscopic pressures. Residual shear stresses are smaller and are treated perturbatively, as in standard second-order dissipative fluid dynamics.

The resulting optimized viscous anisotropic hydrodynamic evolution equations are derived in 3+1 dimensions and tested in a (0+1)-dimensional Bjorken expansion, using an updated lattice equation of state. Comparisons with other viscous hydrodynamical frameworks are presented.

Speaker: Mike McNelis (The Ohio State University)

mcnelis_qm2018.pdf

544 A resummed method of moments for the relativistic hydrodynamic expansion

A modern approach to obtaining the equations of motion of dissipative relativistic hydrodynamics relies on various approximations of the relativistic Boltzmann equation. There is a mounting evidence that the standard Chapman-Enskog expansion of the Boltzmann equation has a vanishing radius of convergence. The method of moments, on the other hand, is free from such problems. The equations thus obtained can be systematically improved, and their convergence properties checked. However, if one introduces mean-field interactions, for example in the form of a medium-dependent mass or an external gauge field interacting with the plasma, this systematic expansion breaks down: Successive moments are found to couple not only to energy moments of higher, but also of lower order,which diverge in the ultra-relativistic (massless) limit, orrequire unrealistic machine precision. This problem is even worse if one starts with the Wigner quasi-probability distribution, in order to generalize the results of the expansion. In the absence of the on-shell condition, all of the moments are ill defined, with the notable exception of the conserved currents (the stress-energy tensor).
We solve the issue using resummed moments which consist of a sum of all the moments of the same tensorial rank, but different energy weights. The resulting equations are always well defined. The evolution of the hydrodynamics moments (four-velocity, energy density, pressure, pressure corrections etc.) is exactly the same as the one provided by the traditional method of moments, if such an expansion is well defined. We tested numerically the convergence properties of the resummed expansion for some known solutions of the microscopic theory, and we checked that the convergence remains intact in the simplest case in which the traditional expansion breaks down. Namely the Boltzmann-Vlasov equation for charged mass-less particles coupled to the Maxwell equations in a (0+1)-dimensional expansion.

Speaker: Leonardo Tinti (The Ohio State University)

Tinti_QM_2018.pdf

Open heavy flavour: II

Convener: Silvia Masciocchi (GSI - Helmholtzzentrum fur Schwerionenforschung GmbH (DE))

545 $\Lambda_C^{+}$ production in pp and PbPb collisions at 5.02 TeV with the CMS experiment

Due to their large mass, the interactions of heavy quarks with the quark-gluon plasma (QGP) may be different from those of light quarks. The lightest charm baryon is the $\Lambda_C^{+}$, composed of a charm quark and two light quarks. Measurements of $\Lambda_C^{+}$ production in both pp and PbPb collisions can provide important inputs to the understanding of heavy quark transport in the QGP and the creation of heavy quark mesons and baryons via coalescence. Models involving quark coalescence predict a large enhancement of $\Lambda_C^{+}$ production in PbPb collisions compared to pp collisions. The high luminosity datasets collected at a nucleon-nucleon center-of-mass energy of 5.02 TeV using the CMS detector have been used to measure $\Lambda_C^{+}$ production in both pp and PbPb collisions via the $\Lambda_C^{+} \to P^{+} K^{-} \pi^{+}$ decay channel. Results for differential cross sections for $\Lambda_C^{+}$ and ratios of $\Lambda_C^{+}$ over $D^0$ yields in pp and PbPb collisions, as well as the nuclear modification factors for $\Lambda_C^{+}$, are presented.

Speaker: Rui Xiao (Purdue University (US))

0516_finalversion.pdf

546 Non-strange and strange D-meson and charm-baryon production in heavy-ion collisions measured with ALICE at the LHC

Heavy quarks (charm and beauty) are a powerful probe of the Quark-Gluon Plasma (QGP) formed in high-energy heavy-ion collisions. They are produced in hard
scattering processes on a timescale shorter than the QGP formation time and experience the whole system evolution. The measurement of the nuclear modification factor ($R_{\rm AA}$) of open heavy flavours can provide important information about the microscopic interactions of heavy quarks with the medium constituents, in particular on the colour-charge and parton-mass dependence of heavy-quark energy loss. The measurements of the elliptic flow ($v_{2}$) at low $p_{\rm T}$ can give insight into the participation of the heavy quarks to the collective expansion of the system and their thermalization in the medium. These two observables can also help in understanding possible modifications of heavy-quark hadronisation in the medium. In particular, the role of the recombination mechanism can be studied for charm via the comparison of D mesons without strange-quark content with D$^+_{\rm s}$ and charm baryons.

Measurements of charm-baryon production in pp and p-Pb collisions are also essential to establish a baseline for Pb--Pb collisions. The measurements in pp collisions provide critical tests of models of charm hadronisation in vacuum and the measurements in p-Pb collisions are useful to study cold nuclear matter effects.

In this talk, the latest results on $p_{\rm T}$-differential $R_{\rm AA}$ and $v_2$ of D mesons measured at mid-rapidity in Pb-Pb collisions with ALICE will
be presented. New results on the D-meson $v_2$ with the Event-Shape Engineering technique in Pb-Pb collisions will be also discussed. The $p_\mathrm{T}$-differential cross section of the $\mathrm{\Xi_c^0}$ baryon in pp collisions and the $\Lambda_{c}^+$ baryon in pp and p-Pb collisions will be presented. Finally, the $\Lambda_{\rm c}^+$ production in Pb-Pb collisions will be shown. The measurements will be compared with model predictions.

Speaker: Xinye Peng (Central China Normal University CCNU (CN))

qm2018-xinye-v8.pdf

547 Measurements of D0 Meson Directed, Elliptic and Triangular Flow Using the STAR Detector at RHIC

Since heavy quarks are predominantly created in the initial hard scatterings in a heavy-ion collision, they can access the information of the early time dynamics. Recently, it has been predicted that the transient magnetic field generated in heavy-ion collisions can induce a larger directed flow ($v_{1}$) for heavy quarks than for light quarks. The model calculation also suggests opposite signs of $dv_{1}/dy$ for charm ($c$) and anti-charm ($\bar{c}$) quarks. This argues for heavy quarks offering a new approach to study the initial electromagnetic field. Furthermore, recent measurements at RHIC have shown that $D^{0}$ mesons in minimum bias and mid-central heavy-ion collisions exhibit significant elliptic ($v_{2}$) and triangular flow ($v_{3}$). Their flow magnitude follows the Number-of-Constituent-Quark (NCQ) scaling with light hadrons' in mid-central collisions. It will be particularly interesting to measure the centrality dependence of these observables and test whether and when the NCQ scaling breaks for charm hadrons.

STAR has collected high statistics data for Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 200 GeV with the Heavy Flavor Tracker detector during 2014 and 2016, allowing us to achieve high precision anisotropic flow measurements for charm hadrons at RHIC energies. In this talk, we will report the first measurement of $v_{1}$ for the $D^{0}(\bar{u}c)$ and $\overline{D^{0}}(u\bar{c})$ mesons at $\sqrt{s_{\rm NN}}$ = 200 GeV Au+Au collisions and compare to those of light flavor hadrons and model predictions. We will present differential measurements of $D^{0}$ meson $v_{2}$ and $v_{3}$ in various centralities of Au+Au collisions, and compare them to those of light flavor hadrons to test the NCQ scaling. The $D^{0}$ $v_{2}$ measured in Au+Au collisions will also be compared to that measured in d+Au collisions to help understand the non-flow effects. Physics implications of these measurements will be discussed.

Speaker: Dr Subhash Singha (Kent State University)

D0_vn_STAR_QM18_SINGHA.pdf

548 Development of heavy-flavour flow-harmonics in high-energy nuclear collisions

We employ the POWLANG transport setup, developed over the last few years, to provide new predictions for several heavy-flavour observables in relativistic heavy-ion collisions from RHIC to LHC center-of-mass energies. In particular, we focus on the development of the flow-harmonics v2 and v3 arising from the initial geometric asymmetry in the initial conditions and its associated event-by-event fluctuations. Within the same transport framework, for the sake of consistency, we also compare the nuclear modification factor of the pT spectra of charm and beauty quarks, heavy hadrons and their decay electrons. We compare our findings to the most recent data from the experimental collaborations. We also study in detail the contribution to the flow harmonics from the quarks decoupling from the fireball during the various stages of its evolution: although not directly accessible to the experiments, this information can shed light on the major sources of the final measured effect. We also display preliminary results obtained with event-shape engineering, selecting events with different eccentricities within the same centrality class or vice versa.

Speaker: Andrea Beraudo (INFN, sezione di Torino (IT))

beraudo-QM.pdf

549 Strong directed flow of heavy flavor as a probe of matter distribution in heavy-ion collisions

The breaking of longitudinal boost invariance in non-central relativistic heavy ion collisions due to asymmetric local participant densities gives rise to a tilt in the reaction plane in the thermalized medium. A direct consequence of this is the observed rapidity odd directed flow of charged particles. We study the $v_1$ of $D$ and $\bar{D}$ mesons by evolving the charm quark phase space distribution within Langevin dynamics coupled to a hydrodynamic background. We demonstrate that the drag from the tilted fireball gives rise to directed flow of charm quarks that is $several$ $times$ $larger$ than that of the $v_1$ of observed charged particles[1]. The $v_1$ slope at mid-rapidity is sensitive to the magnitude of the tilt of the initial thermalized medium. Thus, its measurement will allow us to extract the tilt which also sets the scale of longitudinal correlation. Hence, rapidity odd heavy flavor $v_1$ is an ideal candidate to unravel the longitudinal profile of entropy deposition. We report on the comparison of the heavy flavor $v_1$ across beam energies as well as symmetric and asymmetric systems. Further, the electromagnetic fields of the initial stage can also give rise to rapidity odd $v_1$ but of opposite signs for $D$ and $\bar{D}$ mesons, unlike the tilt mechanism which provides same sign $v_1$ to both $D$ and $\bar{D}$. We study the interplay of the tilt and the electromagnetic fields on the $v_1$ of $D$ and $\bar{D}$ mesons.

[1]. S. Chatterjee and P. Bożek (2017), arXiv:1712.01189 [nucl-th]

Speaker: Sandeep Chatterjee (AGH University of Science and Technology, Krakow)

HQv1.pdf

Phase diagram and search for the critical point: I

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

550 The QCD Phase Diagram from Statistical Model Analysis

Ideally, the Statistical Hadronization Model (SHM) freeze-out curve should reveal the QCD parton-hadron phase transformation line in the ($T$,$μ_B$) plane. We discuss the effects of various final state interaction phenomena, like baryon-antibaryon annihilation, core-corona effects or QCD critical point formation, which shift or deform the SHM freezeout curve. In particular, we present a method to remove the annihilation effects by quantifying them with the microscopic hadron transport model UrQMD[1].
We further discuss the new aspects of hadronization that could be associated with the relatively broad cross-over phase transformation as predicted by lattice-QCD theory at low $μ_{B}$. That opens up the possibility that various observables of hadronization, e.g. hadron formation or susceptibilities of higher order (related to grand canonical fluctuations of conserved hadronic charges) may freeze out at different characteristic temperatures. This puts into question the concept of a universal (pseudo)critical temperature, as does the very nature of a cross-over phase transformation.
[1] F. Becattini, J. Steinheimer, R. Stock and M. Bleicher, Phys.Lett. B764 (2017) 241-246

Speaker: Reinhard Stock

Stock_QM2018-2.pdf

551 Baryon clustering near a (hypothetical) QCD critical point I

Clustering in systems with attractive forces are known in many physical settings:
for example in formation of globular clusters in Galaxies.
Formation of nuclear fragments is a well known phenomenon in low energy nuclear collisions,
especially at temperatures $T\sim 10\, MeV$ near the gas-liquid critical point.
At a freezeout stage of high energy collisions, with $T=100-150\, MeV$,
no clustering is generally expected. However, STAR measurement of the proton
number distribution has found that kurtosis (the 4-proton cumulant)
grows toward the lowest collision energies. Using some version of the mean field approximation and spherical geometry, we study whether the long-range forces, expected near the critical point, can generate bound multi-baryon ``globular clusters".

Speaker: Edward Shuryak (stony brook university)

Shuryak_QM_clusters.pdf

552 Search for the QCD critical point through the rapidity dependence of cumulants

In the coming Beam Energy Scan, RHIC will have much higher luminosity at $\sqrt{s}=20$ GeV than it will at $\sqrt{s}=10$ GeV and below. With the STAR iTPC upgrade in place they will be able to reach proton rapidities up to $|y|\sim 0.8$ where the baryon chemical potential $\mu_B$ in $\sqrt{s}=20$ GeV collisions is somewhat higher than at mid-rapidity. They may therefore be able to use the high statistics at this and nearby collision energies to vary $\mu_B$ somewhat by varying $y$, as well as by scanning down to the lowest possible collision energies. By employing Ising universality together with a phenomenologically motivated freeze-out prescription, we demonstrate that the rapidity dependence of Gaussian and non-Gaussian cumulants is sensitive to the presence of the critical point and exhibits a characteristic pattern as indicated by critical universality. If there is a critical point to be found in the regime that RHIC will explore, we propose the rapidity dependence of cumulants as a complementary route to finding signs of its presence. In particular, it seems likely that the rapidity dependence of cumulants will change qualitatively if one passes the critical point during the RHIC beam energy scan.

Speaker: Jasmine Brewer (Massachusetts Institute of Technology)

JasmineBrewer-QM2018.pdf

JasmineBrewer-QM2018.pptx

553 Search for the critical point by the NA61/SHINE experiment

NA61/SHINE is a fixed target experiment operating at CERN SPS. Its main goals are to search for the critical point of the strongly interacting matter and to study the onset of deconfinement. For these goals a scan of the two dimensional phase diagram (T-$\mu_B$) is being performed at the SPS by measurements of hadron production in proton-proton, proton-nucleus and nucleus-nucleus interactions as a function of collision energy.

In this contribution the status of the search for the critical point of strongly interacting matter by the NA61/SHINE Collaboration will be presented including recent results on proton intermittency, strongly intensive fluctuation observables of multiplicity and transverse momentum and higher moments of net charge fluctuations. These measurements are expected to be sensitive to the correlation length and, therefore, have the ability to reveal the existence of the critical point via possible non-monotonic behavior. The new NA61/SHINE results are compared to the corresponding NA49 measurements and model predictions.

Speaker: Evgeny Andronov (St Petersburg State University (RU))

EA_qm_2018.pdf

554 PHENIX Measurements of $dN_{ch}/d\eta$ in small systems (p$+$A, d$+$Au, and $^{3}$He$+$Au)

The PHENIX experiment has an excellent data set for small systems including p+Au, d+Au, 3He+Au at 200 GeV as well as the d+Au beam energy scan down to 19.6 GeV. We present new measurements of $dN_{ch}/d\eta$ for all of these systems over a broad range in pseudorapidity $-3 < \eta < +3$ and event multiplicity. These measurements provide key constraints of baryon stopping models and are compared with various theoretical calculations. The measurements are also compared with flow observables as a function of pseudorapidity to explore scaling relations. In particular measurements as a function of collision energy provide key inputs for calculations for the upcoming A+A beam energy scan at RHIC in terms of particle production and baryon rapidity shifts.

Speaker: Darren McGlinchey (Los Alamos National Laboratory)

McGlinchey_dndeta_qm2018.pdf

10:40 Coffee Break

Collective dynamics: III

Convener: Steffen A. Bass (Duke University)

555 (3+1)D hybrid model of heavy-ion collisions at BES energies with dynamical sources

At Relativistic Heavy Ion Collider (RHIC) Beam Energy Scan (BES) energies, the dynamics of the pre-equilibrium stage and the effects resulting from a nonzero net baryon current become critical components of the dynamical evolution of the collision fireball. We develop a (3+1)-dimensional hybrid evolution model with dynamical sources for both energy-momentum and the net baryon current. During an initial pre-equilibrium stage based on UrQMD, the four-momenta and baryon numbers carried by secondary particles created within UrQMD are fed continuously, after a short thermalization time, into a (3+1)-dimensional viscous hydrodynamic evolution module. This initialization provides an alternate model to those recently studied by Petersen ${\it et~al}$. [1] and Shen and Schenke [2]: It thermalizes more rapidly than Ref. [1] and yields a different initial net baryon distribution than Ref. [2]. We present and compare with these previous approaches the dynamical evolution of all thermodynamic and dissipative degrees of freedom, including net baryon diffusion. The sensitivity of experimental observables (spectra and anisotropic flows) to the details of the pre-equilibrium stage and to baryon diffusion will also be demonstrated.

[1] H. Petersen ${\it et~al.}$, Phys. Rev. C $\mathbf{78}$, 044901 (2008).

[2] C. Shen and B. Schenke, arXiv:1710.00881 [nucl-th].

Speaker: Lipei Du (The Ohio State University)

QM18_Du_final.pdf

556 Dynamical initialization and hydrodynamic modeling of relativistic heavy-ion collisions

We present a fully three-dimensional model providing initial conditions for energy and conserved charge density distributions in heavy ion collisions at RHIC Beam Energy Scan (BES) collision energies [1,2]. The model includes the dynamical deceleration of participating nucleons or valence quarks. It provides a realistic estimation of the initial baryon stopping during the early stage of collisions. We study various observables obtained directly from the initial state model, including net-baryon rapidity distributions, 2-particle rapidity correlations, and the rapidity decorrelation of the transverse geometry. Their dependence on the model implementation and parameter values is investigated. We also present the implementation of the model with 3+1 dimensional hydrodynamics, which involves the addition of source terms that deposit energy and net-baryon densities produced by the initial state model at proper times greater than the initial time for the hydrodynamic simulation. The importance of this pre-equilibrium stage on hadronic flow observables at the RHIC BES will be quantified.

[1] C. Shen and B. Schenke, "Dynamical initial state model for relativistic heavy-ion collisions", arXiv:1710.00881 [nucl-th].

[2] C. Shen and B. Schenke, "Initial state and hydrodynamic modeling of heavy-ion collisions at RHIC BES energies", arXiv:1711.10544 [nucl-th]

Speaker: Dr Chun Shen (Brookhaven National Laboratory)

QM2018_CShen.pdf

557 Directed Flow of Quarks from the RHIC Beam Energy Scan Measured by STAR

Directed flow ($v_1$) is a good probe of the early-stage dynamics of collision systems, and the $v_1$ slope ($dv_1/dy$) at mid-rapidity is sensitive to the system's equation of state. Previously, a coalescence picture has been used to relate the elliptic flow ($v_2$) of identified particles to the $v_2$ of their constituent quarks [1]. In this talk, the coalescence idea is extended to study the $v_1$ of the constituent quarks - this includes quarks produced in the collision, as well as those transported from the initial-state nuclei. Rather than probe coalescence of $v_2$ versus $p_T$, we focus on $dv_1/dy$ versus $\sqrt{s_{NN}}$.

We report STAR measurements of $v_1(y)$ for ten particle species ($\pi^\pm$, $p$, $\bar{p}$, $\Lambda$, $\bar{\Lambda}$, $\phi$, $K^\pm$ and $K^0_{S}$) in Au+Au collisions at eight beam energies from $\sqrt{s_{NN}} = 7.7$ GeV to 200 GeV. The $v_1$ slopes of $\bar{p}$, $K^-$ and $\bar{\Lambda}$ are used to test the coalescence sum rule for produced quarks. We hypothesize that the $v_n$ of observed mesons and baryons is the summed $v_n$ of their constituent quarks, and it is assumed that deconfined quarks have already acquired azimuthal anisotropy. Data involving produced quarks support the coalescence picture at $\sqrt{s_{NN}} = 11.5$ GeV to 200 GeV, and a sharp deviation from this picture is observed at 7.7 GeV [2].

The $dv_1/dy$ of transported quarks are studied via net particles (net $p$, net $K$ and net $\Lambda$). The net-particle $dv_1/dy$ data for $p$, $K$ and $\Lambda$ agree at and above $\sqrt{s_{NN}} = 14.5$ GeV, but net kaons begin to diverge with decreasing beam energy. Tests of the coalescence sum rule are carried out for net particles, and implications for transported quark $v_1$ are discussed.

References
[1] J. Adams et al. (STAR Collaboration), Nucl. Phys. A757, 102 (2005).
[2] L. Adamczyk et al. (STAR Collaboration), arXiv:1708.07132.

Speaker: Gang Wang (UCLA)

QM2018_GangWang_ver1 (1).pdf

558 Probing the transverse size of initial inhomogeneities with flow observables

Disentangling the effect of initial conditions and medium properties is an open question in the field of relativistic heavy-ion collisions. We argue that, while one can study the impact of initial inhomogeneities by varying their size, it is important to maintain the global properties fixed.

We present a method to do this by systematically smoothening the initial conditions, and apply it to four common initial condition models. We show that many observables are insensitive to the the hot spot sizes, including integrated $v_n$, scaled distributions of $v_n$, symmetric cumulants, event-plane correlations, and differential $v_n(p_T)$. We find however that the factorization breaking ratio $r_n$ and sub-leading component in a Principal Component Analysis are more sensitive to the initial granularity and can be used to probe short-scale features of the initial density.

Reference: article submitted to arXiv

Speaker: Frederique Grassi

fgrassi.pdf

559 Anisotropic hydrodynamic modeling of heavy-ion collisions at LHC and RHIC

In this talk, we will present phenomenological predictions of 3+1d quasiparticle anisotropic hydrodynamics (aHydroQP). First, we will show comparisons with experimental data produced in 2.76 TeV Pb-Pb collisions at the LHC (PRL 119, 042301 and PRC 96, 044910). We will show some observables such as the spectra, multiplicity, elliptic flow, and HBT radii where we find the agreement between our model and experimental results is quite good. Additionally, we will present some comparisons between aHydroQP and experimental results in 200 GeV Au-Au collisions at RHIC. Our preliminary results show a quite good agreement with the experimental data for the spectra and multiplicity. From these two different systems, at two different energies, our results indicate that aHydroQP provides a promising framework for describing the dynamics of the momentum-space anisotropic QGP created in heavy-ion collisions.

Speaker: Mubarak Alqahtani (Kent State University)

Mubarak_QM18v2.pdf

560 Testing the system size dependence of hydrodynamical expansion and thermal particle production with identified particle measurements in Xe-Xe and Pb-Pb collisions with ALICE

In recent data taking campaigns, the ALICE experiment recorded collisions of Xe-Xe as well as Pb-Pb ions at the unprecedented laboratory energies of $\sqrt{s_{NN}}=$ 5.44 and 5.02 TeV, respectively. This unique set of data allows to investigate bulk particle production for very different systems at similar multiplicities. In particular, the charged particle multiplicities in Xe-Xe collisions are comparable to high multiplicity proton-proton (pp) and proton-Pb (p-Pb) collisions. We will present new results on transverse momentum ($p_{\rm{T}}$) spectra, integrated yields, and mean transverse momenta of pions, kaons, and protons, as well as of phi-mesons for various centrality classes.
The chemical and kinetic freeze-out parameters are extracted via statistical-thermal and combined blast-wave fits to the data in heavy-ion collisions and are compared to results obtained in pp and p-Pb collisions at similar multiplicities.
The evolution of collectivity from pp and p-Pb collisions to Xe-Xe and Pb-Pb collisions is further substantiated by detailed comparisons to predictions from models which couple initial conditions with hydrodynamic expansion and subsequent hadronic cascade based on parameters calibrated by Bayesian analysis of lower energy data.

Speaker: Francesca Bellini (CERN)

QM2018_Bellini_Final.pdf

Electromagnetic and weak probes: II

Convener: Charles Gale (McGill University)

561 Electroweak boson production measurements in p-Pb and Pb-Pb collisions at 5.02 TeV with ALICE

Insensitive to the strong interaction, the electroweak W and Z bosons are clean observables for the initial state of heavy-ion collisions. Their measurement in p-Pb and Pb-Pb collisions provides constraints on the nuclear parton distribution functions (nPDFs) of (anti)quarks. In particular, the W and Z rapidity-differential production cross sections and the decay lepton charge asymmetry as a function of rapidity provide stringent tests of nPDFs. Electroweak boson measurements in heavy-ion collisions also constitute a reference for medium-induced effects on other probes.

In this contribution, the measurement of W and Z-boson production in p-Pb and Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV at forward rapidity ($2.5 < y_{\rm lab} < 4.0$) with ALICE at the LHC will be presented. These measurements are complementary to those by ATLAS and CMS at central rapidity, and more precise than the LHCb measurements with similar rapidity coverage. Rapidity differential measurements of W and Z, as well as of the charge asymmetry of W-decay leptons, in p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV will be discussed.

Final results on the Z production cross section in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV will be shown together with the first measurement of W production at forward rapidity. Results will be compared with model calculations including nPDFs. In addition, the centrality dependence of W yields in p-Pb and Pb-Pb collisions and of Z production in Pb-Pb collisions will be discussed.

Speaker: Mohamad Tarhini (Centre National de la Recherche Scientifique (FR))

QM2018_electroweak_ALICE.pdf

562 nPDF studies with electroweak bosons in pPb collisions at 8.16 TeV with the CMS detector

Yields of W and Z bosons can be used to probe the nuclear parton distribution functions of quarks and antiquarks. New results on W boson and Drell-Yan production in pPb collisions at a nucleon-nucleon center-of-mass energy of 8.16 TeV using the CMS detector will be presented. The muon decay channel is used to study both positive and negative W bosons as a function of muon pseudorapidity. Rapidity and charge asymmetries in the W yield are studied. The Drell-Yan cross section is extracted as functions of the dimuon mass for the first time in pPb collisions, between 15 and 600 GeV, and both as a function of dimuon transverse momentum and rapidity, in the Z boson mass region. Comparisons to theory calculations show that these data are sensitive to the presence of nuclear modifications to the parton distributions in the lead nucleus, and can help improve and constrain theoretical calculations.

Speaker: Andre Govinda Stahl Leiton (Centre National de la Recherche Scientifique (FR))

QM2018_Talk_v6.pdf

11:50 Talk cancelled

563 Penetrating probes: Jets and photons in a non-equilibrium quark-gluon plasma

In this talk, we employ new field-theoretical tools to study photons [1] and, for the first time, jets in a non-equilibrium quark-gluon plasma. Jet broadening and photon emission takes place through radiation which is suppressed by repeated and coherent interaction with the medium. We analyze this physics in a medium that is not in thermal equilibrium. This can provide independent means of extracting quark-gluon plasma transport coefficients, such as the shear viscosity, by using jets or photons. Another important application is jet quenching and photon production in the anisotropic plasma [2] created in the early stages of heavy-ion collisions. We present an analyzis of how these probes are affected by such a momentum anisotropy; more specifically we consider the rapidity dependence of photon emission and jet suppression. Finally, we discuss how to extend our work to higher anisotropy where the exponential growth of chromomagnetic fields dominates momentum broadening during radiation.

[1] S. Hauksson, S. Jeon, C. Gale, arXiv: 1709.03598.

[2] P. Romatschke, M. Strickland, Phys. Rev. D 68, 036604 (2003)

Speaker: Sigtryggur Hauksson (McGill University)

presentation_quark_matter_2018.pdf

564 Evidence for light-by-light scattering in ultraperipheral PbPb collisions with CMS experiment

Light-by-light (LbyL) scattering ($\gamma\gamma \rightarrow \gamma\gamma$) is a fundamental quantum-mechanical process with tiny cross sections. Studies of LbyL scattering, using the large photon fluxes from ultraperipheral PbPb collisions at sqrt(s_N) = 5.02 TeV at the LHC, will be reported based on the evidence of a signal corresponding to an integrated luminosity of 391 $\mu b^{-1}$. The measurement can be recasted into limits on physics beyond the Standard Model, such as Born-Infeld corrections to quantum electrodynamics or GeV mass axions.

Speaker: David d'Enterria (CERN)

dde_light_by_light_CMS_QM18.pdf

565 Unveiling the yoctosecond structure of the QGP with top quarks

Top quarks have been recently measured for the first time in nuclear collisions. With most of the integrated luminosity of the LHC PbPb program to be recorded in the coming years and the impressive projections for the future HL-LHC, HE-LHC or FCC, top quark observables will be measured with good precision and become an excellent probe of the QGP. We argue here that the unique properties of the top quark provide a completely new way to study differentially the space-time evolution of the medium created in heavy ion collisions. Top quarks decay almost exclusively into a W boson and a b quark. The finite lifetimes of the top and W particles and the time-delay in the interaction of the (colour-singlet) W-boson’s decay products with the medium add up to a total time during which the top-decay system is unaffected by the QGP. The three times are correlated with the kinematics of the top quark allowing the approximate determination of the time at which the interaction with the QGP begins. We carry out a simple Monte Carlo feasibility study and find that the LHC has the potential to bring first, limited information on the time structure of the QGP. Substantially increased LHC heavy-ion luminosities or future higher-energy colliders would open opportunities for more extensive studies.

Speaker: Liliana Apolinario (Universidade de Lisboa (PT))

LApolinario_tops.pdf

Jet modifications and high-pT hadrons: IV

Convener: Leticia Cunqueiro Mendez (Oak Ridge National Laboratory - (US))

566 Measurements of inclusive jet suppression, azimuthal dependence of jet yields, and jet substructure at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV with ATLAS

A high energy parton is known to lose energy when passing through the hot and dense medium produced in heavy ion collisions. This results in the modification of jet yields and fragmentation patterns. The latest measurements of the nuclear modification factor, $R_{AA}$, for $R=0.4$ jets in Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV with the ATLAS detector at the LHC are presented. The analysis is performed over a large range of transverse momentum, up to $p_{\mathrm{T}}=1$ TeV, and differentially in jet $p_{\mathrm{T}}$ and rapidity. The jet yield is also measured as a function of the azimuthal angle with respect to the second- and third-order event planes. The jet azimuthal harmonic coefficients $v_{n}$ are derived as a function of centrality and jet $p_{\mathrm{T}}$ to probe the path length dependence of jet quenching. In addition, a new measurement of the substructure of jets in Pb+Pb and $pp$ collisions is presented which provides complementary information to jet fragmentation functions.

Speaker: Martin Spousta (Charles University)

Spousta_QM2018_20180416_v2.pdf

567 JETSCAPE 1.0: The first software release of the JETSCAPE collaboration

The Jet Energy-loss Tomography with a Statistically and Computationally Advanced Program Envelope (JETSCAPE) Collaboration is developing an innovative modular event generator to be used by the wider community. In this talk we highlight the performance of the year-1 release of the JETSCAPE software, which consists of an overall framework program, and of several physics modules. The framework organizes the order in which different modules are called, how these can interact with each other, and how the final results are stored or written out. The physics modules provide individual energy loss schemes synchronized by the framework.

The year-1 setup invokes TRENTO for the initial energy density distribution for nucleus-nucleus collisions, which is then used as the initial state for the MUSIC fluid dynamics event generator. The initial binary collision profile from TRENTO is sampled to call PYTHIA events, which generate hard outgoing partons. The passage of these partons through the space-time profile generated by MUSIC is simulated via four different energy loss modules: HYBRID, LBT, MARTINI and MATTER. These can be combined for multi-stage event generation. Hadronization is carried out via Cooper-Frye for the soft medium, and via PYTHIA for the hard sector.

Comparison with experimental results and the resulting determination of input parameters is performed using statistical emulators using Bayesian techniques. In this presentation, we outline the experimental observables that can be successfully described using such a next-generation event generator and discuss the upcoming improvements and enhancements of the year-2 software.

Speaker: Kolja Kauder (Wayne State University)

Kauder_QM18_Jetscape.pptx

568 Measurement of Jet Nuclear Modification Factor in PbPb Collisions at $\sqrt{s_\text{NN}}$ = 5.02 TeV with CMS

Inclusive jet spectra in PbPb and pp collisions at 5.02 TeV are measured in data collected by the CMS detector at the LHC during Run 2 in 2015. The measurement is performed for jet transverse momentum greater than 200 GeV/c and a pseudorapidity window of $|\eta|<2$. The jet nuclear modification factor is extracted for various collision centrality selections to study the impact of jet quenching on jet yields. The measurement is compared to theoretical calculations. The radius dependence of the jet suppression is expected to be sensitive to the jet energy loss mechanism and medium response. Therefore, studies of jets in PbPb and pp are explored for unprecedented large jet radius parameter, ranging from 0.2 to 1.0 with the anti-kt algorithm. The comparative measurement of suppression over small to large radius parameter maps energy loss out of the cone in a theoretically controlled way.

Speaker: Christopher Mc Ginn (Massachusetts Inst. of Technology (US))

qm2018_5TeVCMSJetFinal_CFM_20180515.pdf

569 Probing heavy ion collisions using quark and gluon jet substructure with machine learning

We introduce a novel jet quenching study approach by the classification of quark-initiated jets and gluon-initiated jets in proton-proton and heavy ion collisions using modern machine learning techniques. We train a deep convolutional neutral network on jet images. The classification performance is compared with the multivariate analysis of several physically-constructed jet observables including the jet mass, the $p_T^D$, the multiplicity and the radial moments. We also compare with the systematic $N$-subjet expansion in the recently developed telescoping jet deconstruction framework to exploit the information carried by the subjets. The quark and gluon jet samples generated from the JEWEL simulation are used as an example to demonstrate this general method. We find that the classification performance goes down in the JEWEL-simulated heavy ion collisions. The information carried by the subleading subjets can be washed out by the possible subjet thermalization or randomization due to the soft event activities. Our method provides a systematically improvable framework for analyzing and comparing jet simulations and measurements in heavy ion collisions.

Speaker: Dr Yang-Ting Chien (Massachusetts Institute of Technology)

Chien_QM2018.pdf

570 Measurements of jet fragmentation and the angular distributions of charged particles within and around jets in $pp$ and Pb+Pb with ATLAS

Highly energetic jets produced in ultra-relativistic nuclear collisions are considered to be direct probes to study the properties of the hot and dense QCD matter created in these collisions. The measurement of the fragmentation functions of jets into charged particles in Pb+Pb collisions is sensitive to the strength and mechanism of jet quenching. In this talk, we present the latest measurement of the internal structure of jets and the angular distributions of charged particles within and around jets performed with the ATLAS detector. Fragmentation functions in Pb+Pb collisions and distributions of the transverse momentum of charged particles are compared to the same quantities measured in $pp$ collisions at the same collision energy. Measurements are presented as a function of collision centrality, jet transverse momentum, and jet rapidity at $\sqrt{s_{\mathrm{NN}}}$ of 2.76 and 5.02 TeV. Furthermore, a new measurement of the angular distributions of charged-particles with respect to jet axis extended to distances outside the jet radius of $R = 0.4$ is presented.

Speaker: Martin Rybar (Univ. Illinois at Urbana Champaign (US))

QM2018_Rybar_v3.pdf

571 Adding vacuum branching to jet evolution in a dense medium

It is well known that the multiple interactions of a hard probe with a dense quark-gluon plasma result in the "medium-induced" radiation of soft gluons, responsible e.g. for jet energy loss. Such an emission can be computed using the BDMPS-Z formalism, which has recently been generalised to include multiple medium-induced emissions. To get a complete picture of the evolution of a jet in a dense medium, the main missing ingredient is the inclusion of both medium-induced emissions and "vacuum-like" emissions responsible for the parton shower from large virtualities (of the order of the hard scale) down to the hadronisation scale.

In this talk, we adopt a new approach and show that in a (leading) double-logarithmic approximation, the time scales in the evolution of a jet factorise. The vacuum-like parton cascades develop at early times and exhibit angular ordering due to color coherence, like the standard parton showers in the vacuum. The effect of the medium can be simply formulated as a kinematic constraint which limits the phase-space for vacuum-like radiation and thus reduces the parton multiplicities. The gluons produced by these cascades lose their mutual coherence via multiple scattering and hence act as independent sources of energy loss via medium-induced radiation.

To the best of our knowledge, this is the first complete picture of jet evolution in the medium derived from perturbative QCD. It has the additional advantage of being well-suited for a Monte-Carlo implementation. In the talk, we show how this simple evolution arise and investigate its main properties.

Speaker: Edmond Iancu (Université Paris-Saclay (FR))

Iancu-QM2018.pdf

Phase diagram and search for the critical point: II

Convener: Claudia Ratti (University of Houston)

572 Constraining the QCD critical point from lattice simulations

We examine the reliability of available methods to constrain the location
of the critical endpoint from lattice simulations. For this, we use
several lattice simulations. First, we reexamine the Fodor-Katz
critical endpoint estimate using the same staggered lattice with
modern methods. Second, we look at the compatibility of the
reweighting result with estimates of the convergence radius of the
Taylor expansion. Third, we look at fine
staggered lattices, calculate higher order fluctuations there, and
make estimates of the radius of convergence, now close to the
continuum limit. The talk should make it clearer how much one
can trust claims in the literature about the lattice excluding
regions of the phase diagram for the critical endpoint location.

Speaker: Attila Pasztor (University of Wuppertal)

qm.pdf

573 QCD transition at zero and non-zero baryon densities

We will present new state-of-the-art lattice QCD results on the chiral crossover temperature of QCD for moderately large baryon chemical potential. Firstly, we will present a more precise updated result for the QCD pseudo-critical temperature at zero baryon chemical potential, obtained from all possible second-order chiral susceptibilities that diverge in the chiral limit. Then we will present new results on the QCD pseudo-critical temperature at non-zero baryon chemical potential, computed using Taylor-expansions of chiral condensate and chiral susceptibilities up to 4th-order in the chemical potential. Finally, we will present various second-order fluctuations along the QCD crossover line to look for possible signs of increased fluctuations with increasing baryon density.

Speaker: Patrick Steinbrecher (Brookhaven National Laboratory and University of Bielefeld)

qm18f.pdf

574 Higher moment fluctuations of identified particle distributions from ALICE

We present the first measurements of skewness and kurtosis of fluctuations of identified particle distributions measured with ALICE in Pb-Pb collisions. These distributions can be related to conserved quantum number fluctuations. The measurements can also be compared to RHIC measurements at lower energies and lattice QCD and hadronic resonance gas model calculations to obtain quantum number specific chemical freeze-out parameters. Finally, they will be used to constrain estimates on higher moment measurements for future LHC runs.

Speaker: Nirbhay Kumar Behera (Inha University (KR))

nirbhay_QM2018.pdf

575 Hidden strangeness shines in NA61/SHINE

One of the main objectives of the NA61/SHINE experiment at the CERN SPS is to
study properties of strongly interacting matter (SIM). This includes a
two-dimensional scan in the beam momentum and size of the colliding system, to
investigate the onset of deconfinement discovered by NA49, and to search for
the critical point of SIM. This contribution presents first ever results on
$\phi$ meson production in proton-proton collisions, the smallest system in the
scan, at beam momenta of 40 and 80 GeV/c, and most detailed ever
experimental data at 158 GeV/c.

Strangeness production enhancement in large systems compared to small ones is
traditionally considered as a signal of quark-gluon plasma formation. To
discuss the nature of the enhancement it is important to compare this effect in
both the open and hidden strangeness sector which is done in this contribution.
The comparison of $p + p$ to Pb $+$ Pb results shows also a non-trivial system size
dependence of the longitudinal evolution of hidden strangeness production,
contrasting with that of other mesons.

The results are furthermore compared to world data on $\phi$ meson production
demonstrating superior accuracy, and to several models. The latter include a
statistical and three microscopic models. None is found to be able to describe
simultaneously the shapes of transverse momentum spectra, shapes of rapidity
distributions and total yields.

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

marcinek_QM_2018_05_16.pdf

576 Lattice-based QCD equation of state at finite baryon density

Lattice QCD methods allow to calculate the thermodynamic observables at finite temperature and imaginary chemical potential. The Wuppertal-Budapest collaboration data [1,2] for the temperature dependence of the leading four Fourier coefficients of the imaginary part of the net-baryon density at imaginary baryochemical potential is analyzed. We demonstrate how the lattice behavior of these coefficients is naturally described by the inclusion of the repulsive, excluded volume type interactions between baryons [2], in line with earlier studies regarding conserved charges fluctuations [3,4].

We formulate a Cluster Expansion Model (CEM), which provides all higher order Fourier coefficients on the basis of the leading two coefficients [5], and allows to calculate QCD thermodynamics at non-zero chemical potentials. CEM is shown to be consistent with all the available lattice data, both at $\mu_B = 0$ and at imaginary baryochemical potential. Moreover, the radius of convergence of the Taylor expansion of the QCD pressure is found to be finite within CEM, and caused by the Roberge-Weiss like transition [6] in the complex $\mu_B / T$ plane. No evidence for the QCD phase transition at $\mu_B / T < \pi$ is found.

Finally, we present the full equation of state at finite baryon density within CEM, which can be incorporated in hydrodynamic simulations.

[1] S. Borsanyi et al. [Wuppertal-Budapest Collaboration], Talk at Quark Matter 2017 Conference, 5-11 February, Chicago, USA

[2] V. Vovchenko, A. Pasztor, Z. Fodor, S.D. Katz, H. Stoecker, Phys. Lett. B 775, 71 (2017)

[3] V. Vovchenko, M.I. Gorenstein, H. Stoecker, Phys. Rev. Lett. 118, 182301 (2017)

[4] P. Huovinen, P. Petreczky, 1708.00879

[5] V. Vovchenko, J. Steinheimer, O. Philipsen, H. Stoecker, 1711.01261

[6] A. Roberge, N. Weiss, Nucl. Phys. B 275, 734 (1986)

Speaker: Volodymyr Vovchenko (Frankfurt Institute for Advanced Studies)

vovchenko_qm18.pdf

577 Recent Results and Methods on Higher Order and Off-diagonal Cumulants of Identified Net-particle Multiplicity Distributions in Au+Au Collisions at STAR

The ratios of the cumulants of identified net-partile multiplicity distributions have been suggested to be sensitive to the onset of QCD phase transition and to the additional fluctuations expected from the close proximity to the critical point [1,2,3].
We report the first measurements of $6^{th}$ order cumulants of net-charge distributions, up to $3^{rd}$ order cumulants of net-$\Lambda$ distributions, and off-diagonal cumulants of net-charge, net-proton, and net-kaon distributions for Au+Au collisions at BES energies using particle species dependent efficiencies. Net-proton cumulants up to $4^{th}$ order have been obtained with unfolding to correct for non-binomial detector effects as well as a new method for volume fluctuation corrections [4]. We show the first measurement of cumulant ratios ($C_{2}/C_{1}$, $C_{3}/C_{2}$) of net-$\Lambda$, which are each subject to strangeness and baryon number conservation. We extract the chemical freeze-out parameters ($\mu_{B}$, $T$) from these measurements under the assumption that the experimental multiplicity cumulant ratios are equivalent to the ratios of susceptibilities from the lattice.

[1] M.A.Stephanov, Phys. Rev. Lett. 102, 032301 (2009).
[2] B. Friman, F. Karsch, K. Redlich, V. Skokov, Eur. Phys. J. C 71, 1694 (2011).
[3] A. Majumder and B. Muller, Phys. Rev. C 74, 054901 (2006).
[4] P. Braun-Munzinger, A. Rustamov, and J. Stachel, Nucl. Phys., A960:114130, 2017.

Speaker: Toshihiro Nonaka (Univ. Tsukuba)

draft_tnonaka_v3.pdf

QCD at high temperature: II

Convener: Massimo D'Elia (University of Pisa)

578 Parity doubling of baryons in QCD thermodynamics

Motivated by the recent lattice study by the FASTSUM collaboration [1],
thermal masses of the baryon parity-doublers are explored for
various pion masses [2]. A general trend of the octet and decuplet
parity-doublers is consistent to the results in [1], whereas their
hyperon masses are modified to a large extent for the physical pion mass.

We further investigate the fluctuations and correlations involving
baryon number in hot hadronic matter with modified masses of
negative-parity baryons, in the context of the hadron resonance gas
[3]. Confronting the baryon number susceptibility, baryon-charge
correlation, and baryon-strangeness correlation and their ratios
with the lattice QCD data, we show that the strong downward mass
shift in hyperons can accidentally reproduce some correlation
ratios, however it also tends to overshoot the individual
fluctuations and correlations. This indicates, that in order to
correctly account for the influence of the chiral symmetry
restoration on the fluctuation observables, a consistent framework
of in-medium effects beyond hadron mass shifts is required.

References
[1] G. Aarts, et al., JHEP 1706, 034 (2017).
[2] C. Sasaki, Parity doubling of baryons in a chiral approach with three flavors,'' arXiv:1707.05081 [hep-ph]. [3] K. Morita, C. Sasaki, P. M. Lo and K. Redlich,Overlap between Lattice QCD and HRG with in-medium effects and parity doubling,'' arXiv:1711.10779 [hep-ph].

Speaker: Chihiro Sasaki

qm.pdf

579 Baryons, chiral symmetry and in-medium effects: results from lattice QCD

The behaviour of strange baryons in the hadronic gas and the quark-gluon plasma gives essential insight into chiral symmetry restoration and parity doubling, and has direct consequences for phenomenology, e.g. via the hadron resonance gas. We present results obtained using nonperturbative lattice simulations, employing the FASTSUM anisotropic Nf=2+1 ensembles.

Speaker: Chris Allton (Swansea University)

allton-qm2018.pdf

580 Equation of state at finite density from the lattice

A new precision lattice simulation set is analyzed for the equation of state
to sixth order. We discuss the role of strangeness neturality and the
range of validity of the extrapolation strategy. We calculate the pressure,
trace anomaly, energy and entropy densitiy and the baryon number in the range
up to mu/T < 2. We achieve improved precision by combining the technique of
analitcal continuation from imaginary chemical potentials with the
direct calculation of high order mu-derviatives.

Speaker: Szabolcs Borsanyi (University of Wuppertal)

qm18_borsanyi.pdf

581 Relating the Lyapunov exponents to transport coefficients in kinetic theory

In this work we discuss the phenomenological applications of non-equilibrium hydrodynamical attractors to transport phenomena in fluid dynamics. We study the late-time behaviour of a relativistic fluid undergoing Bjorken flow whose microscopic description is given in terms of the Boltzmann equation with a time-dependent relaxation time. The mathematical problem of solving the Boltzmann equation is recast into an infinite set of nonlinear ordinary differential equations for the moments of the one-particle distribution function. Viewed this as a dynamical system of coupled ODEs, we can then determine with a suitable truncation, the non-equilibrium attractor solution of the Boltzmann equation from a small set of hydrodynamic and non-hydrodynamic moments of the one-particle distribution function. The asymptotic expansion of the attractor allows us to extract numerically the values of the Lyapunov exponents and at the same time, the values of different transport coefficients like the shear viscosity. As a result we are able to establish an empirical relation between the maximal Lyapunov exponent and the shear viscosity in relativistic kinetic theory. We comment on how to generalize our results and the possible implications of our findings in hydrodynamical simulations of relativistic heavy ion collisions.

Speaker: Mauricio Martinez Guerrero (North Caroline State University)

QM18_CNCruz_Camacho.pdf

582 Electric conductivity of hot and dense quark matter in a magnetic field with Landau level resummation via kinetic equations

This talk is based on 1711.01472 in which the longitudinal electric conductivity of hot and dense magnetized quark matter has been computed with full Landau level resummation which requires several nontrivial theoretical techniques. In contrast to the lowest Landau level approximation, there is no singularity in the massless limit, and we find that the resultant electric conductivity is surprisingly consistent with the qualitative features observed in condensed matter (using Weyl semimetals) experiment for the signature of the chiral magnetic effect. This means that our calculation correctly captures the essence of the topologically induced currents. Because the mass and magnetic dependence of the conductivity is found to be mild after the Landau level resummation, we also make a quantitative comparison with the recent lattice QCD simulation results without magnetic field to confirm that our estimate is again surprisingly consistent with the lattice-QCD values. We can apply our calculation to the finite density case, which provides us with theoretical predictions relevant for the beam energy scan program at finite density. Since quarks are enhanced but anti-quarks are suppressed, the longitudinal electric conductivity stays rather constant, which is intuitively natural, but this is theoretically seen only after subtracting coupling to hydrodynamic zero modes correctly. Not only the longitudinal conductivity (that is related to the chiral magnetic effect) but also the transverse conductivities will be discussed. At finite density, in fact, one component of the transverse electric conductivities newly grows up, that is the Hall conductivity. The Hall conductivity could result in more prospective effects observable in the heavy-ion collision experiment, which will be suggested in this talk.

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

fukushima.pdf

583 The Cosmic Quarks

There are at least three sources of cosmic quarks in the universe. One, the quark
nuggets which may survive beyond a certain baryon number during the phase
transition from quarks to hadrons microseconds after the big bang. These quark
nuggets can very well be candidate of cold dark matter and these nuggets consist of
strange quarks.
Second, the interior of the neutron star may well be made of quarks due to very
very high pressure. It is further shown that the interior of heavy neutron star,
recently discovered ≈ 2M⊙, with an appropriate equation of state, can also be made
of quark core.
Finally, using the property of colour entanglement among quarks it is entirely
possible to have free orphan quarks roaming around in the cosmos. Some better
understanding of dark energy and dark matter is possible with these entangled
orphan quarks.

Speaker: Prof. Bikash Sinha (Variable Energy Cyclotron Centre)

Quark Matter, 2018.pdf

Quark Matter, 2018.ppt

13:10 Lunch

Correlations and fluctuations: III

Convener: Tapan Nayak (CERN, Geneva and VECC, Kolkata)

584 Bose-Einstein correlations and b$\bar{\rm b}$ correlations in pp collisions with LHCb

LHCb offers the unique opportunity to perform correlation and production measurements in the light-flavour sector at forward rapidity. The measurement of the dihadron correlation as function of pseudorapidity eta and azimuthal angle phi in pp at sqrt(s)=13 TeV will be shown. The measurement will be put into context with the pPb ridge result by LHCb and will expand our knowledge on collective behaviour in small collision systems. In pPb collisions, both at forward and backward rapidity, the production measurement of the strange particles K^0_S and Lambda will be presented in order to progress our understanding of soft particle production and hadronisation.

Speaker: Bartosz Piotr Malecki (Polish Academy of Sciences (PL))

BartoszMalecki_QM2018.pdf

585 Three-dimensional femtoscopy with two identical pions and pion-kaon pairs in Pb-Pb collisions from the LHC ALICE experiment

Results are presented for femtoscopic correlations with charged pion-kaon and identical pion-pion pairs measured with ALICE for Pb-Pb collisions at $\sqrt{s_{NN}}=$ 2.76 and 5.02 TeV. Three-dimensional femtoscopic analyses were performed for both systems in different transverse-momentum intervals and for different centrality classes. The source radius and the correlation strength parameter for the case of two identical pions together with the source radius and emission asymmetry extracted from the pion-kaon correlations are reported. The average source size of the system and emission asymmetry between pions and kaons increase for more central collisions. The results are compared with calculations from hydrodynamic-based models, and implications for model parameters are discussed.

Speaker: Ashutosh Kumar Pandey (IIT- Indian Institute of Technology (IN))

PionKaonFemto_QM2018_apandey.pdf

586 Centrality and impact parameter in nucleus-nucleus collisions

In heavy-ion collision experiments, the centrality of a collision is defined according to the transverse energy or number of tracks observed in a given detector. We propose a procedure to relate this experiment-defined centrality to the true centrality of the collision, defined according to impact parameter, in a way which does not need require the introduction of a Glauber model or the concept of participant nucleons. Our method allows to accurately reconstruct the probability distribution of impact parameter at a fixed value of the experiment-defined centrality, up to 5%. We argue that in central collisions, the fluctuations of impact parameter have specific signatures in the centrality dependence of the cumulants of elliptic flow, $v_2\{2\}$ and $v_2\{4\}$, and that these effects are clearly visible in experimental data.
Extension to proton-nucleus collisions is discussed (work in progress).

[Based on arXiv:1708.00081]

Speaker: Jean-Yves Ollitrault (CNRS)

QM2018_Ollitrault.pdf

587 Geometry and Dynamics in Heavy-ion Collisions Seen by the Femtoscopy in the STAR Experiment

Geometry and dynamics of the particle-emitting source in heavy-ion collisions at high energies can be inferred via femtoscopy method. Two-particle correlations at small relative momentum exploit Quantum Statistics and the Final State Interactions which allow one to study the space-time characteristics of the source of the order of $10^{-15}$ m and $10^{-23}$ s, respectively. The RHIC Beam Energy Scan (BES) program covers a significant part of the QCD Phase Diagram using collisions of Au nuclei for eight beam energies in the range from 7.7 to 200 GeV, which baryon-rich region should be studied via baryon femtoscopy. Thus, two-baryon measurements together with two-meson and meson-baryon correlations provide complementary information about the source characteristics.

In this talk, the STAR preliminary results on femtoscopic observables of various particle combinations of protons, pions and kaons from Au+Au collisions at BES energies will be presented. Determining how the properties of the particle-emitting source depend on collision energy is an important step towards understanding the physics of heavy-ion collisions. The BES program provides the possibility to study the energy dependence of the source sizes for various collision centralities. In addition to the source size, the measurements of non-identical particle combinations provide information about space-time asymmetries in emission process.

Speaker: Sebastian Siejka (Warsaw University of Technology)

QM_Siejka.pdf

588 The evolution of the near-side peak in two-particle number and transverse momentum correlations in Pb-Pb collisions from ALICE

Two-particle number and transverse momentum correlations are powerful tools for studying the medium produced in heavy-ion collisions. Correlations in the angular separation of pairs of hadrons can provide information on the medium transport characteristics. In particular, the transverse momentum correlations are sensitive to momentum currents, and provide information about the system life time, the shear viscosity $\eta$/s and the system relaxation time $\tau_{\pi}$. Furthermore, the interaction of the jets produced in the initial stages of collision can be studied using number correlations, by observing the medium-induced modification of the near-side jet peak. We report measurements of both sets of correlations from Pb-Pb collisions as a function of centrality. Theoretical interpretations and results from Monte Carlo generators are then confronted with the experimental data.

Speaker: Monika Varga-Kofarago (Hungarian Academy of Sciences (HU))

Varga-Kofarago_QM2018.pdf

Future facilities, upgrades and instrumentation: II

Convener: Grazyna Odyniec

589 The Compressed Baryonic Matter (CBM) Experiment at FAIR

The Compressed Baryonic Matter (CBM) experiment is currently under construction and is one of the pillars of FAIR in Darmstadt. High-intensity heavy-ion beams delivered by the SIS100 accelerator (FAIR Phase 1) will be used to explore the QCD phase diagram in the region of neutron-star core baryon-densities. Interaction rates of up to 10 MHz on a fixed target will enable measurements at an unprecedented level of precision and thereby allow access to rare probes like, e.g., multi-strange hyperons and hyper-nuclei. In-medium mass distributions of vector mesons can be measured via lepton pairs, and excitation functions of various observables will serve as sensitive probes for phase transitions.

After an introduction into the physics program of CBM, this talk will focus on the instrumentation of the experiment. Suiting the conducted collision rates, the CBM detectors will be built in a fast and radiation-hard design. The self-triggered and free-streaming read-out concept will be presented and the online event selection on a high-performance computing cluster will be covered. As examples, detector characteristics and recent test beam results will be discussed for the Silicon Tracking System (STS), for the Muon Chambers (MuCh) and for the Transition Radiation Detector (TRD). An outlook on the status of the next major step of system integration, namely miniCBM in FAIR Phase 0, will be given.

Speaker: Philipp Kahler (Westfaelische Wilhelms-Universitaet Muenster (DE))

CBMatFAIR_PhilippK.pdf

590 Studies of extremely dense matter in heavy-ion collisions at J-PARC

We aim at studies of dense matter as a future project of J-PARC (J-PARC-HI), in fixed target heavy-ion collision experiments at 1-19 AGeV/c. We are going to search for the QCD critical end point and the first order phase boundary. The dense matter created at J-PARC-HI has a density of 5-10 times as high as the normal nuclear density similar to neutron stars and neutron star mergers. Therefore, we aim at studying the properties of dense matter related to them, in particular the equation of state (EOS). Recently, neutron merge has been observed with gravitational wave, and the result already limited the region of the EOS. We aim at constraining the EOS also in heavy-ion collisions. We expect to produce world's highest rate heavy-ion beams of $10^{11}$ with the ion spieces from p to U. The heavy-ion acceleration will be realized by introducing a new injector consisting of a linac and a booster ring, and utilizing existing 3-GeV and 50-GeV synchrotorons (RCS and MR, respectively). MR has achieved acceleration of $4.3 \times 10^{13}$ protons per pulse at 30 GeV is going to achieve the designed rate of $1.2 \times 10^{14}$ in 2019.
We design a multi-purpose spectrometer to measure dileptons, photons, and hadrons, and a spectrometer dedicated to hypernuclear measurements. In this talk, we will optimize the detector configurations and evaluate some of key performance of the spectrometers, such as dilepton and photon measurements, neutron measurements for event-by-event fluctuations, and hypernuclear measurements based on realistic simulations. We also report the R&D status on such as a Time-of-Flight counter based on MRPC (Multi Resisitive Plate Chambers)and a triggerless fast data-acquistion system.

Speaker: Hiroyuki Sako (Japan Atomic Energy Agency (JP))

QM18-sako-20180516-publish.pdf

QM18-sako-20180516-publish.pptx

591 Multi Purpose Detector to study heavy-ion collisions at the NICA collider

The MPD (Multi Purpose Detector) is under construction to study hot and baryon rich QCD matter in heavy ion collisions at the NICA collider in the energy range √s_NN = 4 - 11 GeV. Physics program includes the study of collective phenomena, Λ polarization, dilepton, hyperon and hypernuclei production under extreme conditions of highest baryonic density. The MPD construction is progressing in accordance with the schedule.

Speaker: Vladimir Kekelidze (Joint Institute for Nuclear Research (RU))

Kekelidze.pdf

Kekelidze.pptx

592 Studies of baryonic matter at BM@N JINR

BM@N (Baryonic Matter at Nuclotron) is the first experiment to be realized at the accelerator complex of NICA-Nuclotron in JINR. The aim of the BM@N experiment is to study interactions of relativistic heavy ion beams with fixed targets. The scientific program of the BM@N experiment comprises studies of nuclear matter in the intermediate energy range between experiments at SIS and NICA/FAIR facilities. The BM@N experiment is in the starting phase of its operation and has recorded first experimental data. The experimental runs were performed in the deuteron and carbon beams with the kinetic energy from 3.5 to 4.5 GeV per nucleon. The extended configuration of the BM@N set-up is being realized for the next run with the argon and krypton beams. The future experimental program of the experiment and first experimental results on the production of hyperons are presented.

Speaker: Mikhail Kapishin (JINR, Dubna)

BMN_QM2018.pdf

593 A fixed-target programme at the LHC for heavy-ion, hadron, spin and astroparticle physics: AFTER@LHC

By splitting the multi-TeV LHC proton and lead beams with a bent crystal or by using an internal gas target, the LHC complex allows one to perform the most energetic fixed-target experiments ever and to study with high precision pp, pd and pA collisions at $\sqrt{s}_{NN}$=115 GeV and Pbp and PbA collisions at $\sqrt{s}_{NN}$=72 GeV. A broad programme, covering the large-x frontier for particle and astroparticle physics, spin and heavy-ion physics will greatly complement collider experiments, in particular those of RHIC and the EIC project. We will present our latest feasibility studies for Drell-Yan, quarkonia, heavy-flavoured as well as light flavoured hadrons using LHCb and ALICE detectors. These can be studied with different species in a wide rapidity range providing important information concerning quark and gluon (n)pdf at large x, cold nuclear matter effects, quarkonium formation time in the medium, expected sequential suppression in QGP and final state interaction effects.

Speaker: Daniel Kikola

AFTER-QM-2018.pdf

New theoretical developments: II

Convener: Raju Venugopalan (Brookhaven National Laboratory)

594 Characterizing hydrodynamical fluctuations in heavy­-ion collisions from effective field theory approach

Hydrodynamic fluctuations are found to be important in many situations such as cosmology, condensed matter system and heavy-ion collisions. Recently, an effective field theory for fluctuating dissipative hydrodynamics has been developed in 1511.03646 and 1701.07817. We apply this theory to investigate non-trivial consequence hydrodynamic fluctuations on the Bjorken expanding quark ­gluon plasma (QGP). In particular, we explore nontrivial effects due to interactions among hydrodynamical variables and noises which are systematically incorporated in the present framework but are not fully captured in conventional approaches. Finally, we discuss its application to model bulk evolution of QCD matter near the critical point as well as extracting shear viscosity of QGP.

Speaker: Dr Pak Hang Lau (MIT)

Quarkmatter_present.pdf

595 Applications of deep learning in relativistic hydrodynamics

Deep learning is one of the machine learning technologies developed in computer science. Recently, it has been implemented to various research areas in physics, including search of gravitational lens [1], identifying and classifying the phases of Ising model [2], the search of Higgs and exotic particles [3], classification jet structure [4], etc. In this talk, we will implement deep learning to relativistic hydrodynamics, which is a useful tool to simulate the evolution of relativistic systems in high energy nuclear physics and astrophysics [5].

Using 10000 initial and final energy density and flow velocity profiles generated from 2+1-d hydrodynamics with MC-Glauber initial conditions, we train the network and use it to predict the final profiles associated with various initial conditions, including MC-Glauber, MC-KLN and AMPT and TRENTo. A comparison with the hydrodynamic calculations shows that the network predictions can nicely capture the magnitude and inhomogeneous structures of these final profiles, as well as the related eccentricity distributions $P(\varepsilon_n)$ (n=2, 3, 4). These results indicate that deep learning can capture the main feature of the non-linear evolution of hydrodynamics, which shows the potential of largely accelerate the simulations of relativistic hydrodynamics.

Reference
[1] Y. D. Hezaveh, et.al., Nature 548, 555 (2017).
[2] J. Carrasquilla and G. R. Melko, Nature Phys. 13, 431 (2017).
[3] P. Baldi, et.al, Nature Commun. 5, 4308 (2014).
[4] P. T. Komiske, et. al., JHEP 1701, 110 (2017).
[5] H. Huang, B. Xiao, H. Xiong, Z. Wu, Y. Mu and H. Song, in preparation.

Speaker: Hengfeng Huang (Peking University)

DeepLearning_Hydro_HengfengHuang.pdf

596 Holographic description of quarkonium dissociation in nonequilibrium strongly interacting matter

The real-time dissociation of the heavy quarkonium in a strongly coupled boost-invariant non-Abelian plasma relaxing towards equilibrium is analyzed in a holographic framework. The effects driving the plasma out of equilibrium are described by boundary quenching, impulsive variations of the boundary metric. Quarkonium is represented by a classical string with endpoints kept close to the boundary. The evolution of the string profile is computed in the time-dependent geometry, and the dissociation time is evaluated for different configurations with respect to the direction of the plasma expansion.

Speaker: Pietro Colangelo (Universita e INFN, Bari (IT))

colangelo-qm2018.pdf

597 Particle production in high energy collisions: from high to low pt and back

We describe a new approach to particle production in high energy hadronic/nuclear collisions which aims to unify the Color Glass Condensate (CGC) formalism at low x (low pt) with that of pQCD and collinear factorization formalism at intermediate to large x (high pt) and therefore generalizes the CGC formalism to include high pt physics. To this end we consider scattering of a quark from high x modes of the target hadron or nucleus in addition to (all-order) scattering from the usual soft color field describing the low x modes. We derive an analytical expression for the quark propagator which includes longitudinal momentum exchange with the target and allows for large angle deflection of the projectile quark. This quark propagator is then used to compute the Leading Order DIS structure functions F2 and F_L in the general kinematics 0 < x < 1 and thus generalizes the dipole picture of structure functions at small x. We outline how this formalism can be extended to calculate particle production in high energy proton-nucleus and nucleus-nucleus collisions at all pt, and how it enables one to compute jet energy loss effects from the early stages of a heavy ion collision.

Based on Phys.Rev. D96 (2017) no.7, 074020 (arXiv:1708.07533) and work in progress

Speaker: Jamal Jalilian-Marian (Baruch College)

qm2018.pdf

598 All-opacity gluon spectrum for jet physics at the EIC

The cross-sections and substructure of jets in eA reactions in a
future electron-ion collider (EIC) are expected to be modified
compared to the vacuum. At leading order in the strong
coupling, a jet produced at an EIC is initiated as an energetic
quark, and its substructure arises from its splitting into a quark-
gluon system. The spectrum of gluons within this quark jet is then
heavily modified by multiple scattering in the QCD medium,
allowing jet substructure to be used to pin down the transport
properties of cold nuclear matter. In this talk, I will present new
results on the gluon spectrum of a quark jet computed to an
arbitrary order in opacity (the average number of scatterings in
the medium). This calculation goes beyond the simplifying limit
in which the gluon radiation is soft and can be interpreted as
energy loss of the quark, and it extends previous work which
computes the full gluon spectrum only to first order in opacity.
In addition to presenting the general structure of the all-orders
result, I will also show specific evaluations of the gluon
spectrum at the first few orders in opacity and discuss its
sensitivity to the transport properties of large nuclei.

Speaker: Matthew Sievert (Los Alamos National Laboratory)

Sievert_QM2018_Revised.pdf

Open heavy flavour: III

Convener: Burkhard Schmidt (CERN)

599 Production of open charm and beauty states in pPb collisions with LHCb

A rich set of open heavy flavour states is observed by LHCb in pPb collisions data collected at 5 and 8.16 TeV nucleon-nucleon center-of-mass energy. Results include the new measurements of production of beauty hadrons in pA collisions through cleanly reconstructed exclusive decays. Open charm states include the Lambda_c baryon, that was also observed in pA collisions for the first
time by LHCb.

Speaker: Jiayin Sun (Tsinghua University)

slides_QM2018_Sun.pdf

600 Measurement of heavy flavor production and azimuthal anisotropy in small and large systems with ATLAS

Measurements of heavy flavor hadron production and their correlations in A+A collisions provide insight into the energy loss mechanism and transport properties of heavy quarks in the QGP. From this perspective, the same measurements in $p$+A collisions thus serve as a necessary baseline for understanding the observations in A+A collisions. Additionally, detailed studies of the azimuthal anisotropy for heavy flavor hadrons in $p$+A may help address the question of whether the observed long-range ``ridge'' correlation arises from hard or semi-hard processes, or if it is the result of mechanisms unrelated to the initial hardness scale. This talk presents ATLAS measurements of heavy flavor production, via their semi-leptonic decay to muons in $\sqrt{s_\mathrm{NN}} = 2.76$ TeV Pb+Pb and $pp$ collisions, and via identified prompt $D$ mesons in $\sqrt{s_\mathrm{NN}} = 8.16$ TeV $p$+Pb collisions. Heavy flavor muon yields are observed to be strongly suppressed in Pb+Pb collisions compared to that in $pp$ collisions. On the other hand, the prompt $D$ meson production in $p$+Pb collisions shows no obvious modification compared to the theoretical predictions for $pp$ collisions, indicating relatively small cold nuclear matter effects for $D$ meson production. The $p_{\mathrm{T}}$ and centrality dependence of flow harmonics $v_2$--$v_4$ associated with heavy-flavor muons in Pb+Pb are also presented. The measured $v_2$ decreases over the $p_{\mathrm{T}}$ range of 4--14 GeV, and shows a systematic variation with centrality that was observed in other $v_2$ measurements. The anisotropy measurements are extended to 8.16 TeV $p$+Pb collisions, where the azimuthal modulations of heavy-flavor muons, prompt $D$ mesons and J/$\psi$ are studied using two-particle correlations. The statistical significance of the presence or absence of long range correlations involving heavy flavor production in $p$+Pb events is quantified.

Speaker: Qipeng Hu (University of Colorado Boulder)

ATLAS_HF_QHu.pdf

601 Open-heavy-flavour production and elliptic flow in p-Pb collisions at the LHC with ALICE

Measurements of open heavy flavour production in p-A collisions allow us to investigate Cold Nuclear Matter (CNM) effects, like gluon shadowing, gluon saturation, $k_{\rm T}$ broadening, and energy loss in CNM, that can affect the production rate and the kinematic properties of charm and beauty hadrons in nuclear collisions. In recent years, also the formation of a small-size Quark-Gluon Plasma (QGP) in p-Pb collisions was advanced as a possible explanation of effects like long-range $v_{2}$-like angular correlations in high-multiplicity events or the enhancement of baryon production, typically observed in nucleus-nucleus collisions and ascribed to the collective expansion of the QGP. The measurement of angular correlations of heavy-flavour particles with charged particles, at central and forward rapidities, provide an important extension of studies performed with light-flavoured hadrons to further characterise the $v_{\rm 2}$-like behavior, understand its initial- or final-state nature, constrain its development in the partonic and/or hadronic stages, and better investigate its mass dependence. The study of open heavy flavour production in high-multiplicity p--Pb collisions can also add important information to address the expected connection between collective-like and energy-loss-like effects. Moreover, production studies as a function of the multiplicity of charged particles produced in the collision can give insight into mutiple parton interactions and into the interplay between hard and soft processes

In this talk, we will present production measurements of D$^{0}$, D$^{+}$, D$^{*+}$ and D$_{s}^{+}$ mesons reconstructed with the ALICE detector via their hadronic decays at mid-rapidity in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV, collected during LHC Run-2. In particular, we will report cross sections, down to $p_{\rm T}$ = 0 for D0 mesons, nuclear-modification factors as well as multiplicity- and centrality-dependent studies. The measurement of the production of heavy-flavour hadron decay electrons at central rapidity at $\sqrt{s_{\rm NN}}$ = 5.02 and 8.16 TeV will be also presented. We will discuss the measurement of $v_{\rm 2}$ of heavy-flavour hadron decay electrons in high-multiplicity p-Pb collisions at
$\sqrt{s_{\rm NN}}$ = 5.02. The data will be compared to light flavour ones and theoretical calculations. Results will be shown also for the production of heavy-flavour hadron decay muons at forward and backward rapidity at $\sqrt{s_{\rm NN}}$ = 5.02 TeV. The status of the analysis of muon correlation with charged particles in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 8.16 TeV will be discussed. The production results will be compared with predictions from theoretical models including CNM effects, as well as assuming the formation of a QGP in p-Pb collisions.

Speaker: Henrique Jose Correia Zanoli (Universidade de Sao Paulo (BR) and Utrecht University (NL))

qm.pdf

602 Measurements of charm, bottom, and Drell-Yan via dimuons in $p$+$p$ and $p$+Au collisions at $\sqrt{s_{NN}}=200$ GeV with PHENIX at RHIC

Dilepton spectra are a classic probe to study ultra-relativistic heavy ion
collisions. At RHIC energies, the dimuon continuum is dominated by correlated pairs from charm and bottom semi-leptonic decays and the Drell-Yan process. No Drell-Yan measurement had been made at $\sqrt{s_{NN}}=200$ GeV to date. A precise measurement of the Drell-Yan cross-section can provide constraints to PDFs. The dimuon spectra also contain information on heavy flavor angular correlations, which can constrain the relative contributions from different heavy flavor production mechanisms. Studying heavy flavor correlations in $p$+Au collisions may provide further insight to understanding cold nuclear matter effects.

In this talk, we report measurements of $\mu\mu$ pairs from charm, bottom, and Drell-Yan in $p$+$p$ and $p$+Au collisions at $\sqrt{s_{NN}}=200$~GeV. A further shape analysis is applied to the heavy flavor pair correlations to extract the ratios of leading and next-to-leading order contributions.

Speaker: Yue Hang Leung (Stony Brook University)

qm2018v4.pdf

603 The dynamical energy loss formalism: from explaining unexpected suppression patterns to implications for future experiments

Understanding properties of Quark-Gluon Plasma requires an unbiased comparison of experimental data with theoretical predictions. To that end, we developed the dynamical energy loss formalism which, in distinction to most other methods, takes into account a realistic medium composed of dynamical scattering centers. The formalism also allows making numerical predictions for a wide number of observables with the same parameter set fixed to standard literature values. I will first briefly review the most recent developments of the formalism. I will further argue that numerical implementation of the formalism has reached the stage where it can provide comprehensive and realistic predictions for both the existing and the upcoming experimental data, and also guide some of the future experiments. To that end, I will show: i) that the model post-dictions agree with numerous data for both central and non-central collisions, including qualitatively explaining some of unexpected experimental observations, ii) show that the predictions, which were published well before the data became available, agree very well with these data, again explaining some of the unexpected experimentally observed suppression patterns, iii) predictions for the upcoming data, where some point to qualitative expectations that can be used to distinguish between different energy loss mechanisms, and consequently guide future experiments. Overall, these results show that the dynamical energy loss formalism predicts high pt suppression with high accuracy. The first steps in our work towards the application of this model as a novel high-precision tomographic tool of QGP medium, will also be discussed.

Speaker: Magdalena Djordjevic (Institute of Physics Belgrade)

QM2018_Djordjevic.pdf

Phase diagram and search for the critical point: III

Convener: Helen Caines (Yale University (US))

604 Hydro+ : Hydrodynamics for the QCD critical point

The search for the QCD critical point in heavy-ion collision
experiments requires dynamical modeling of the bulk evolution of the
QCD matter as well as of the fluctuations near the critical
point. Critical slowing down means that fluctuations are significantly
deviating from equilibrium near the critical point. We generalize
hydrodynamics to quasi-equilibrium conditions where the state of the
system is characterized by the off-equilibrium magnitude of
fluctuations in addition to the usual hydrodynamic variables --
conserved densities. We find that the key ingredient of the formalism
-– the extended entropy taking into account the off-equilibrium
fluctuations -- is remarkably similar to the 2PI action in quantum
field theory. We use the new formalism to demonstrate the major
effects of critical fluctuations on the bulk evolution: the strong
frequency dependence of the anomalously large bulk viscosity as well
as the stiffening of the equation of state with increasing frequency
or wave-number.

Speaker: Misha Stephanov (UIC)

qm-2018-slides.pdf

605 Identifying the QCD transition with deep learning

The state-of-the-art pattern recognition method in machine learning (deep convolution neural network) is used to identify the equation of state (EoS) employed in the relativistic hydrodynamic simulations of heavy ion collisions. High-level correlations of particle spectra in transverse momentum and azimuthal angle learned by the network act as an effective EoS-meter in deciphering the nature of the phase transition in QCD. The EoS-meter is model independent and insensitive to other simulation inputs including the initial conditions and shear viscosity for hydrodynamic simulations. Through this study we demonstrate that there is a traceable encoder of the dynamical information from the phase structure that survives the evolution and exists in the final snapshot of heavy ion collisions and one can exclusively and effectively decode these information from the highly complex final output with machine learning when traditional methods fail

Speaker: Dr Long-Gang Pang (Physics department of UC Berkeley)

QM2018_LongGang.pdf

606 Time-evolution of fluctuations as signal of the phase transition dynamics in a QCD-assisted transport approach

For the understanding of the fluctuation measurements in heavy-ion collisions
it is crucial to develop quantitatively reliable dynamical descriptions. In order
to study the phase transition, both in crossover regime as well as near the
conjectured QCD critical point, the non-perturbative nature needs to be fully
included. In this talk, we outline a novel QCD-assisted transport approach based on
non-equilibrium chiral fluid dynamics and the effective action of low energy
QCD. This approach makes use of the full equilibrium correlation functions and
includes dissipation and stochastic noise.

We test the new framework within a low energy effective mesonic theory. For
this case, we discuss the time evolution of fluctuation observables based on
the higher-order moments such as the skewness and kurtosis as the system
passes through the phase boundary. In this way, we can study details of the
equilibration of the order parameter and of higher-order correlations, as well
as the impact of critical slowing down on the correlation length. The
underlying theory naturally includes critical and non-critical contributions.
We can, therefore, explicitly test the size of the critical region, where scaling
and dynamical scaling hold. Finally, the relative effect of critical
versus baseline contributions to the fluctuation dynamics is quantified.

Speaker: Nicolas Wink (University of Heidelberg)

wink_18_QM.pdf

607 Transits of the QCD Critical Point

Building on an analysis of hydrodynamic long time tails for a Bjorken expansion (Akamatsu 2017, Akamatsu 2017), we discuss the hydrodynamic scales associated with transiting the critical point. First, we consider the case where the nuclear medium passes directly through the critical point. In this case, the modes with wave-number of order the inverse Kibble-Zurek length and smaller fall out of equilibrium during the transit, and limit the growth of critical fluctuations in a characteristic way which depends on the wave-numbers involved. This Kibble-Zurek wavenumber will be contrasted to wave numbers of order $k\sim \sqrt{ (e + p)/\eta \tau }$ which are always out of equilibrium, even away from the critical point (Akamatsu 2016). Subsequently we generalize to the situation when the system misses the critical point by a an amount, $\Delta = n_c/s_c \delta(s/n)$. In this case there is an additional scale, and Kibble-Zurek scaling is only relevant if $\Delta$ is sufficiently small. We will define ``sufficiently small" in the talk and analyze the intermediate case. The scales introduced in this analysis give a qualitative picture of the QCD critical point in heavy ion collisions, which can inform all experimental searches.

References:

Y. Akamatsu, A. Mazeliauskas and D. Teaney, ``A kinetic regime of hydrodynamic fluctuations and long time tails for a Bjorken expansion,'' Phys. Rev. C95, no. 1, 014909 (2017) [arXiv:1606.07742 [nucl-th]].

Y.~Akamatsu, A.~Mazeliauskas and D.~Teaney,``Bulk viscosity from hydrodynamic fluctuations with relativistic hydro-kinetic theory,'' arXiv:1708.05657 [nucl-th].

Speaker: Mr Fanglida Yan (Stony Brook University)

FanglidaYan_QM2018.pdf

608 Open charm measurements in the NA61/SHINE experiment - status and plans

The measurement of open charm production was proposed as an important tool to
investigate the properties of hot and dense matter formed in nucleus-nucleus collisions as well as to provide the means for model independent interpretation of the existing data [1]. Recently, the experimental setup of the NA61/SHINE experiment was supplemented with a Vertex Detector (VD) which was motivated by the importance and the possibility of the first direct measurements of open charm meson production in heavy ion collisions at SPS energies.

First test data taken on December 2016 in Pb+Pb collisions at 150$A$ GeV/$c$ allowed to validate the general concept of D$^0$ meson detection via it's D$^0$ $\rightarrow \pi^{+} + K^{-}$ decay channel and delivered a first indication of open charm production [2]. In October and November of 2017 large statistics data were recorded for Xe+La collisions at beam momenta of 150$A$ and 75$A$ GeV/$c$.
Minimum bias and 0-20\% centrality on-line trigger selection was applied. The Xe+La data are currently under intense analysis.

The talk will discuss the physics motivation of open charm measurements at SPS energies and provide an overview of existing heavy flavor measurements in this energy range. Finally, pilot results on open charm production will be presented
and future plans of open charm measurements in the NA61/SHINE experiment will be discussed requiring an upgraded version of the VD and speed-up of the TPC read-out.

[1] H. Satz {\it Adv. High Energy Phys.} {\bf 2013}, (2013) 242918.

[2] ``Report from the NA61/SHINE experiment at the CERN SPS'', CERN-SPSC-2017-038.

Speaker: Pawel Piotr Staszel (Jagiellonian University (PL))

qm2018_16May2018_v2.pdf

16:20 Coffee Break

Chirality, vorticity and polarisation effects: III

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

609 Non-Equilibrium Quantum Transport of Chiral Fluids from Kinetic Theory

The chiral kinetic theory (CKT) is a useful tool to investigate anomalous transport pertinent to quantum anomalies in and out of equilibrium for weyl-fermion systems, which has been widely applied to study chiral magnetic/vortical effects (CME/CVE) in heavy ion collisions (HIC). However, there exist some fundamental issues such as Lorentz covariance and systematic inclusion of collisions in CKT. Such issues have been recently addressed via phenomenological approaches. Nevertheless, a first-principle derivation based on quantum field theories (QFT) is desired.
In this talk, we introduce the QFT derivation of CKT from the Wigner-function approach, which consistently manifests side jumps and non-scalar distribution functions associated with Lorentz covariance and incorporates both background fields and collisions. Moreover, we implement such a formalism to investigate second-order responses of chiral fluids near local equilibrium. Such non-equilibrium anomalous transport is dissipative and affected by interactions. For the study of anomalous transport in closed systems preserving energy-momentum conservation such as quark gluon plasmas, contributions from both quantum corrections in anomalous hydrodynamic equations of motion and those from the CKT and Wigner functions are considered under the relaxation-time (RT) approximation. In the inviscid case, we obtain anomalous charge Hall currents engendered by background electric fields and temperature/chemical-potential gradients. Furthermore, CME/CVE currents receive viscous corrections as non-equilibrium modifications stemming from the interplay between side jumps, magnetic-moment coupling, and chiral anomaly. Our formalism and findings could provide a practical guideline and insights for future simulations of anomalous effects in HIC.
This talk will be based on the works in arXiv:1710.00278, arXiv:1612.04630 (Phys.Rev. D95 (2017) no.9, 091901, Rapid Communication) and an upcoming paper.

Speaker: Di-Lun Yang (RIKEN)

CKT_QM2018.pdf

610 Transport phenomena with chiral fermions in strong magnetic fields

The strong magnetic fields induced by heavy-ion collisions have attracted a lot of interests in transport phenomena in QGP. While the roles of the chiral fermions played in the anomaly-induced transport phenomena have been intensively investigated, their manifestations in the dissipative transport phenomena have not been fully identified. We discuss the heavy-quark diffusion dynamics [1], electrical conductivity [2,3], and viscosities [4] in QGP under the strong magnetic field on the basis of the hard thermal loop resummation, putting an emphasis on the roles of the chiral properties of the lowest-Landau-level fermions. We discuss crucial roles of the chirality conservation and phenomenological consequences, which sheds light on the new aspects of the transport phenomena in the heavy-ion collisions.

Recent related works include the computation of the jet energy loss [5], shear viscosity [6], and the electrical conductivity with the higher Landau levels [7].

[1] K. Fukushima, K. Hattori, H.-U. Yee, and Y. Yin, "Heavy Quark Diffusion in Strong Magnetic Fields at Weak Coupling and Implications for Elliptic Flow," Phys. Rev. D93 (2016) no.7, 074028.

[2] K. Hattori, S. Li, D. Satow, and H.-U. Yee, "Longitudinal Conductivity in Strong Magnetic Field in Perturbative QCD: Complete Leading Order," Phys. Rev. D95 (2017) no.7, 076008.

[3] K. Hattori and D. Satow, "Electrical Conductivity of Quark-Gluon Plasma in Strong Magnetic Fields," Phys. Rev. D94 (2016) no.11, 114032.

[4] K. Hattori, X.-G. Huang, D. Rischke, and D. Satow, "Bulk Viscosity of Quark-Gluon Plasma in Strong Magnetic Fields," Phys. Rev. D96 (2017) no.9, 094009

[5] S. Li, K. Mamo, and H.-U. Yee, Phys. Rev. D94 (2016) no.8, 085016

[6] S. Li and H.-U. Yee, arXiv:1707.00795 [hep-ph].

[7] K. Fukushima and Y. Hidaka, arXiv:1711.01472 [hep-ph].

Speaker: Koichi Hattori (Fudan University)

QM2018---Hattori.pptx

611 Search for the Chiral Magnetic Wave with Anisotropic Flow of Identified Particles at RHIC-STAR

The chiral magnetic wave (CMW) has been theorized to propagate in the Quark-Gluon Plasma formed in high-energy heavy-ion collisions. It could cause a finite electric quadrupole moment of the collision system, and may be observed by charge asymmetry, $A_{\rm ch}$, dependence of elliptic flow of positively and negatively charged hadrons. However, non-CMW mechanisms such as Local charge conservation (LCC) and hydrodynamics with isospin effect [1], could also contribute to the experimental observations.

In this talk, we present the STAR measurements of elliptic flow, $v_{2}$, and triangular flow, $v_{3}$, of charged pions, along with $v_{2}$ of charged kaons and protons, as a function of $A_{\rm ch}$ in Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 27, 39, 62.4 and 200 GeV. The similarity between pion and kaon slopes suggests that the isospin effect is not the dominant mechanism. The slope parameters of $\Delta v_{2}$($A_{\rm ch}$) and $\Delta v_{3}$($A_{\rm ch}$) are reported and compared in different centrality and transverse momentum intervals to investigate the LCC background. The difference between the normalized $\Delta v_{2}$ and $\Delta v_{3}$ slopes, along with the measurements in small systems (p+Au and d+Au at $\sqrt{s_{\rm NN}}$ = 200 GeV), will be presented. Our data favor the CMW interpretation and disfavor the possibility that the observations result from LCC or hydrodynamics at RHIC energies.

Reference
[1] Y. Hatta, A. Monnai and B.-W. Xiao, Nucl. Phys. A947, 155 (2016).

Speaker: Qiye Shou (SINAP/BNL)

qm18_star_cmw_talk.pdf

612 General equilibrium second-order hydrodynamic coefficients

The quark-gluon plasma created in heavy ion collisions is a relativistic fluid with extremely large acceleration and vorticity, as demonstrated by the recent STAR measurement of Lambda polarization.
In local equilibrium conditions, the standard hydrodynamic stress-energy tensor expression is expected to receive corrections proportional to the square of acceleration and vortiicty.

We show how these corrections can be obtained in a systematic way by performing a perturbative expansion around the homogeneous global equilibrium condition as long as the ratio between acceleration, vorticity and temperature are small. The relevant coefficients can be expressed in terms of Euclidean correlators of the stress-energy tensor operator and the generators of the Lorentz group.

We also consider massless fermions with net chirality enforcing a thermal equilibrium with a conserved axial charge. We show that parity-odd collective behavior induced by the interplay between vorticity and chirality, like for instance the Chiral Vortical effect, can be systematically derived within this thermal equilibrium approach.

All these correlators can in principle be estimated for QCD with lattice computations. We present analytic results obtained for a free scalar charged field and a free Dirac field, both massive and massless.

Speaker: Matteo Buzzegoli (University of Florence & INFN Florence)

Buzzegoli_QM2018_169.pdf

613 Phi Meson and K* Spin Alignment in High Energy Nuclear Collisions at STAR

The large initial global angular momentum in non-central collisions, when acting together with spin-orbital coupling, can lead to global polarization of produced quarks. Such effect eventually manifests itself as non-vanishing polarization of hardrons with non-zero spin. Vector mesons, unlike hyperons which have large contributions from resonance decay, are originated predominantly from primordial production, and their alignment are generally additive. Thus, the spin alignment of vector meson is expected to be sensitive to different hadronization scenarios [1] and the vorticity of the colliding system [2-4].

We present STAR's measurement of the global spin alignment of φ and K* vector mesons for Au + Au collisions at $\sqrt{s_{NN}}$ = 7.7, 11.5, 14.5, 19.6, 27, 39 and 200 GeV. The alignment is quantified by the diagonal spin density matrix element $\rho_{00}$ with respect to the normal of the event plane. The $\rho_{00}$ measurement based on the 1st- and 2nd-order event plane will be presented and the relationship between the two will be discussed. The result will be shown as a function of the transverse momentum, the collision centrality and the beam energy. The implications of our results on the vorticity and the hadronization scenarios will be discussed. The dependence on the emission angle with respect to the reaction plane will be presented and compared to model calculations. The dependence on event-by-event charge asymmetry and its implication on the chiral separation effect under the initial magnetic field will also be discussed.

References
[1] Z. T. Liang and X. N. Wang, Phys. Lett. B629, 20 (2005).
[2] Z. T. Liang and X. N. Wang, Phys. Rev. Lett.94, 102301 (2005).
[3] F. Becattini, F. Piccinini and J. Rizzo, Phys. Rev. C77, 024906 (2008).
[4] L.G. Pang, H. Petersen, Q. Wang and X.N. Wang, Phys. Rev. Lett.117, 192301 (2016).

Speaker: Chensheng Zhou (SINAP/BNL)

chensheng_qm2018.pdf

614 A novel invariant mass method to isolate resonance backgrounds from the chiral magnetic effect

The Chiral Magnetic Effect (CME) refers to charge separation along a strong magnetic field, due to topological charge fluctuations in QCD. Charge correlation ($\Delta\gamma$) signals consistent with CME have been first observed almost a decade ago. It has also been known since then that the $\Delta\gamma$ was contaminated by a major background from resonance decays coupled with the elliptic flow ($v_{2}$). The invariant mass ($m_{inv}$) dependence of the $\Delta\gamma$ has, rather surprisingly, not been examined until recently [1].

In this talk, we propose differential $\Delta\gamma$ measurements as function of $m_{inv}$. By restricting to high $m_{inv}$, e.g. above 2 GeV/$c^{2}$, one may extract resonance-free CME signal where particle transverse momenta are still relatively low ($\sim$1.2 GeV/$c$). In the low $m_{inv}$ region, the backgrounds show resonance peaks and the CME signal is presumably smooth in $m_{inv}$. These different behaviors can be exploited by a two-component model to extract the CME signal at low $m_{inv}$. We demonstrate the feasibility and effectiveness of this novel method by using the AMPT and toy-model Monte-Carlo simulations. The power of our method on the upcoming isobaric collisions at RHIC will also be discussed.

[1] J. Zhao, H. Li, F. Wang. Isolating backgrounds from the chiral magnetic effect, arXiv:1705.05410

fqwang.pdf

fqwang.pdf

fqwang.pptx

Collective dynamics: IV

Convener: Tetsufumi Hirano (Sophia Univ)

615 Collective flow and correlations measurements with HADES in Au+Au collisions at 1.23 AGeV

HADES provides a large acceptance combined with a high mass-resolution
and therefore allows to study dielectron and hadron production in
heavy-ion collisions with unprecedented precision. With the high
statistics of seven billion Au-Au collisions at 1.23 AGeV recorded in
2012 the investigation of collective effects and particle correlations
is possible with so far unprecedented accuracy.
At low energies v1 and v2, related to directed and elliptic flow, have
been measured at the BEVALAC and SIS18, but so far high-order harmonics
have not been studied. They allow to characterize the properties of
the dense hadronic medium produced in these collisions, such as its
viscosity, and provide thus an important reference to measurements at
higher energies. We will present data on higher-order flow harmonics
(v3 and v4) of protons and first results on multi-particle azimuthal
correlation analyses, which can be utilized to disentangle the
contribution from collective and non-flow process involved in the
dynamical evolution of heavy-ion reactions. Furthermore, data on
directed and elliptic flow of light nuclei will be shown.
Information on radial flow can be obtained from the analysis of
pion HBT-correlations, deuteron coalescence and transverse momentum
spectra of identified particles. We will present new results on these
observables extracted from the HADES data and discuss their
correlations. From these a consisten picture emerges which provides
strong evidence for a substantial radial expansion already at these low
beam energies.

Speaker: Mr Behruz Kardan (IKF, Uni-Frankfurt)

QM_05_2018_kardan.pdf

616 Elucidating the properties of hot nuclear matter with a comprehensive description of ultra-relativistic heavy-ion collisions

We present the latest developments in the ab-initio description of the initial state of heavy ion collisions at high energies and its coupling to relativistic viscous hydrodynamics. This includes the extension of the IP-Glasma model to include subnucleonic geometry fluctuations, shown to be present in electron-proton scattering, and the inclusion of the full energy-momentum tensor of the Glasma phase at the time of matching to hydrodynamics. After analyzing the effects of these improvements on observables, we present detailed calculations from the combined IP-Glasma+MUSIC+UrQMD model, which also includes the microscopic hadron gas description in the low temperature region. We will show results for multiplicity distributions, transverse momentum spectra, flow observables including higher cumulants, event-plane correlations, and HBT radii in Pb+Pb collisions at 5.02 TeV, as well as predictions for Xe+Xe collisions at 5.44 TeV. We will discuss how the simultaneous description of this wide range of different observables in different systems can be used to constrain the transport properties of the quark-gluon plasma, including the temperature dependence of shear and bulk viscosities.

Speaker: Dr Bjoern Schenke (Brookhaven National Laboratory)

Schenke-QM2018-Venice.pdf

617 NA61/SHINE​ ​measurements​ ​of​​ anisotropic​​ flow​ relative​​ to​​ the​ ​spectator plane​ ​in​ ​Pb-Pb​ ​collisions​ ​over​ a wide​ ​rapidity​ ​range

The NA61/SHINE experiment at the CERN SPS recently extended its program for the energy scan with Pb ions in the energy range of 13-150A GeV/c. Compared to the existing data from the NA49 experiment at the CERN SPS, the new data allows for more precise measurement of anisotropic flow harmonics. The fixed target setup of NA61/SHINE also allows to extend flow measurements available from the STAR at RHIC beam energy scan (BES) program to a wide rapidity range up to the forward region where projectile nucleon spectators appear. The NA61/SHINE measurements with Pb ions and the experimental techniques using spectators at the lowest energy available at the SPS are also relevant for the preparation of the Compressed Baryonic Matter (CBM) heavy-ion​ experiment​ at​ the​ future​ FAIR​ facility​ in​ Darmstadt.

The talk will present an analysis of the anisotropic flow harmonics in Pb-Pb collisions at beam momenta of 13A and 30A GeV/c collected by the NA61/SHINE experiment in the year 2016. Flow coefficients are measured relative to the spectator plane estimated with the Projectile Spectators Detector (PSD). The flow coefficients are obtained as a function of rapidity and transverse momentum in different classes of collision centrality. The results will be compared with the corresponding​ NA49​ data​ and​ the​ measurements​ from​ the​ RHIC​ BES​ program.

In future, measurements will be extended to other collisions systems, such as Xe-La, Ar-Sc, and Be-Be collisions, which are available from the system size scan of the NA61/SHINE experiment. The developed measurement technique using spectators in a fixed target geometry are also relevant for physics performance studies of the future CBM experiment at FAIR at energies of 10A GeV/c and below. CBM is constructing a spectator detector of a design similar to that of the PSD of NA61/SHINE.

Speaker: Viktor Klochkov (GSI / Frankfurt Uni)

20180516_qm_NA61_SHINE_Flow.pdf

618 Collectivity from interference

Abstract:
I discuss how second and higher order cumulant momentum anisotropies may arise
in absence of all mechanisms generally expected to cause finite anisotropy harmonics $v_n$,
namely in absence of initial spatial asymmetries, in absence of initial density effects and in
absence of final state interactions. The mechanism is quantum and color interference of different
particle production channels of multi-particle final states. In a simplified, QCD-inspired model
for the emission of an arbitrary number of $m$ particles from $N$ sources, we show in an
expansion in powers of $1/(N^2_c-1)$ and to leading order in the number of sources
that both second and higher order cumulants show many of the features observed in
proton-proton collisions,including collectivity. \
This presentation will be based on B. Blok, D. J\''akel, M. Strikman, U.A. Wiedemann, arXiv:1708.08241, JHEP in press,
and further work in preparation.

Speaker: Prof. Boris Blok (Technion)

BorisBlokVenice.pdf

619 Latest predictions from the EbyE NLO EKRT model

We present the latest results from the event-by-event NLO pQCD + saturation + viscous hydrodynamics (EbyE NLO EKRT) model [1,2,3,4]. The parameters in the EKRT saturation model are fixed by the charged hadron multiplicity in the 0-5 \% 2.76 TeV Pb+Pb collisions, and the $\sqrt{s}$, A and centrality dependence of the initial particle production is determined by the QCD dynamics of the model. The initial state is then evolved using viscous hydrodynamics, and the $\sqrt{s}$ and A dependence of low-$p_T$ hadron spectra is computed.

Our results are in an excellent agreement with the low-$p_T$ data from 2.76 and 5.02 TeV Pb+Pb collisions at the LHC and 200 GeV Au+Au collisions at RHIC [1,2]. In particular, we study the centrality dependence of hadronic multiplicities, pT spectra, flow coefficients, probability distributions of relative elliptic flow fluctuations, and various flow correlations. A simultaneous analysis of these observables at several collision energies puts much more stringent constraints on the temperature dependence of the shear viscosity than e.g. the flow coefficients at the LHC energies alone.

We present our latest results for various correlators, like symmetric cumulants and non-linear flow coefficients, together with their $p_T$ dependence for all the above collision systems [3]. Furthermore, we show our predictions for the centrality dependence of charged hadron multiplicity and flow coefficients in the 5.44 TeV Xe+Xe collisions at the LHC [4].

[1] H. Niemi, K. J. Eskola and R. Paatelainen, Phys. Rev. C93 (2016) 2, 024907, arXiv:1505.02677 [hep-ph].

[2] H. Niemi, K. J. Eskola, R. Paatelainen and K. Tuominen, Phys. Rev. C93 (2016) 1, 014912, arXiv:1511.04296 [hep-ph].

[3] H. Niemi, K. J. Eskola and R. Paatelainen, work in progress.

[4] K. J. Eskola, H. Niemi, R. Paatelainen and K. Tuominen, arXiv:1711.09803 [hep-ph].

Speaker: Harri Niemi (J. W. Goethe Universität)

qm2018_Niemi.pdf

620 Light (anti-)nuclei production and elliptic flow in Pb-Pb collisions at the LHC with ALICE

Results on the production of stable light nuclei, including deuterons, $^{3}\rm{He}$, $^{4}\rm{He}$ and the corresponding anti-nuclei, in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV and $\sqrt{s_{\rm NN}}$ = 5.02 TeV will be presented and compared with theoretical predictions to provide insight into the production mechanisms in heavy-ion collisions.

These information will be complemented by new results on the elliptic flow of (anti-)deuterons and $^{3}\rm{He}$. While one of the approaches to describe the elliptic flow of hadrons and light nuclei is given by quark coalescence, the production of light nuclei is also depicted as a coalescence of nucleons, i.e. hadron coalescence. Differences should be visible for those two approaches when the elliptic flow is measured simultaneously with the transverse momentum ($p_{\rm T}$) spectra, especially when they are scaled by their number of nucleons and quarks.

The experimental results will be presented giving a critical view of their comparison to the expectations from coalescence and hydrodynamic models that aim at describing both the $p_{\rm T}$-spectra and the elliptic flow.

Speaker: Maximiliano Puccio (Universita e INFN Torino (IT))

180516-mpuccio-QM18final.pdf

Initial state physics and approach to equilibrium: III

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

621 PHENIX study of the initial state with forward hadron measurements in 200 GeV p(d)+A and $^{3}$He$+$Au collisions

Forward hadron measurements in p(d)+A provide a signal to study nuclear
shadowing, initial state energy loss and/or gluon saturation effects as a function of rapidity, centrality and energy. High $p_T$ identified $\pi^{0}$ measurements are also an essential first step toward measuring prompt photon production. The $\pi^{0}$ measurements are enabled by the PHENIX MPC-EX detector, a Si-W preshower detector located in front of Muon Piston Calorimeter (MPC), expanding the neutral pion reconstruction capabilities in the rapidity range $3.1< \eta <3.8$ out to high energies, $E < 80$ GeV. Previous PHENIX measurements of punch-through charged hadrons in the muon arms in the rapidity range $1.4< \vert \eta \vert <2.2$ were significantly improved through the capability of the forward silicon vertex detector (FVTX) to determine the transverse momentum and rapidity with high precison and reject background from secondary hadrons.

PHENIX collected d+Au data with the MPC-EX in the 2016 run at
$\sqrt{s_{NN}} =$ 200, 62, 39 and 19.6 GeV; and p+p and p+Au(Al) data with the FVTX in 2015 at 200 GeV. In this talk we will present first results for high $p_T$ $\pi^{0}$ production from the $\sqrt{s_{NN}}$ = 200 GeV dataset, the status of the prompt photon measurement, as well as charged hadron nuclear modification factors in p+Au(Al) and $^{3}$He$+$Au.

Speaker: Dr Jason Bryslawskyj

Bryslawskyj_Forward_Hadrons_QM2018.pdf

622 ALICE results on system-size dependence of the charged-particle multiplicity density in p-Pb, Pb-Pb and Xe-Xe collisions

Particle production at LHC energies involves the interplay of perturbative (hard) and non-perturbative (soft) QCD processes. Global variables, such as the charged particle multiplicity, related to the initial geometry and the energy density produced in the collision, are important observables to characterize relativistic heavy-ion collisions and to constrain model calculations.
The LHC has produced Xenon-Xenon collisions for the first time in October 2017. New results on the primary charged particle pseudorapidity density, and its pseudorapidity and centrality dependence are presented for this lighter and deformed nuclei, and compared to measurements obtained for lead ions. Novel results will also be presented for p–Pb collisions at the highest energy of 8.16 TeV, as part of an overview of all the measurements at LHC Run 1 and 2 energies. These studies allow us to investigate the evolution of particle production with energy and system size and to compare models based on various particle production mechanisms and different initial conditions.

Speaker: Beomkyu Kim (Inha University (KR))

qm_Beomkyu.pdf

623 Energy and system size dependence of the subnucleonic fluctuations

Understanding the geometric eventy-by-event distribution of gluons in protons and nuclei is a fundamentally interesting task. Moreover, their fluctuating structure has a significant effect on the outcome of hydrodynamical simulations of e.g. proton-nucleus collisions. Thus, it is of utmost interest to determine both the average geometrical structure, and its event-by-event fluctuations, for the hadrons used in high-energy QCD experiments.

Recently, we have shown how the event-by-event fluctuations of the geometric structure of the proton can be constrained from the HERA exclusive vector meson production data [1], and that this information is crucial in order to describe the measured flow harmonics in proton-nucleus collisions [2].

In this talk, we study to what extent the large geometric fluctuations of the proton have effect in nuclear targets. In particular, we show that at large momentum transfer, the J/Psi photoproduction in ultraperipheral heavy ion collisions is sensitive to the event-by-event fluctuations of the nucleon geometry in the LHC kinematics [3]. We also discuss the possibilities of the future Electron Ion Collider to study fluctuations also in light nuclei such as deuteron and helium, whose structure is necessary input for hydrodynamical simulations of e.g. deuteron-gold collisions studied at RHIC.

The high-energy photon-nucleus and proton-nucleus scatterings measured at the LHC make it also possible to study the energy dependence of the fluctuations. We present our ongoing work on describing the Björken-x evolution of the proton structure by solving the JIMWLK evolution equation. The non-perturbative input for the small-x evolution is obtained by fitting the HERA structure function data, which then allows us to predict the energy dependence of the fluctuating structure of the proton.

[1] Phys. Rev. Lett. 117 (2016), 052301
[3] Phys.Lett. B772 (2017) 681-686
[4] Phys.Lett. B772 (2017) 832-838

Speaker: Dr Heikki Mäntysaari (University of Jyväskylä)

qm18_mantysaari.pdf

624 Multiplicity and transverse energy measurements from pp, pPb, PbPb and XeXe collisions with the CMS experiment

One of Richard Feynmans shortest and most cited papers concerns his prediction that for very high energy collisions, the analyticity condition for quantum fields should cause the fragmentation of a nuclear target to become independent of the collision energy. CMS has measured the pseudrapidity dependence of charged hadron multiplicity and transverse energy for a wide range of energies and system sizes. These include pp, (0.9 to 13 TeV), pPb (5.02 and 8.16 TeV), PbPb (2.7 and 5.02 TeV) and recently multiplicity measurements from XeXe at 5.44 TeV. In the mid-rapidity region, $|\eta|<2.4$, the multiplicity measurements are based upon the CMS pixel detectors and the transverse energy measurements use information from both the calorimeters and tracking detectors via a particle flow algorithm. In the forward region the TOTEM T2 tracker has been used to measure the charged particle multiplicity in the region $(5.5<\eta<6.3)$ for 8 TeV pp collisions while theHF and CASTOR Cherenkov calorimeters have been used to measure transverse energy in the $3<|\eta|<6.5$ for a variety of systems. The results are compared across the different collision systems after normalising for the number of participating nucleons.The very large rapidity and energy range of the data allow detailed test of state of the art production models and event generators as well as tests of Feynman's early hypothesis.

Speaker: Ran Bi (Massachusetts Inst. of Technology (US))

QM2018-multiplicity-and-transverse-energy.pdf

625 Thermalization and hydrodynamics in Bjorken and Gubser flows

Rapid and strongly anisotropic expansion throughout its evolution keeps the hot and dense medium created in relativistic heavy-ion collisions from ever reaching a state of local momentum isotropy and thermal equilibrium. Still, hydrodynamic descriptions of heavy-ion collisions are phenomenologically very successful. To elucidate the origin of this success we explore exactly solvable situations where the microscopic dynamics is described by the Boltzmann equation, and compare the exact solution with various hydrodynamic approximations obtained from the Boltzmann equation using different expansion schemes. Specifically, we study the performance of equations derived from a third-order Chapman-Enskog expansion and in the frameworks of second-order anisotropic and viscous hydrodynamics in comparison to the exact solution of the Boltzmann equation for Bjorken and Gubser flows. Systems with Bjorken flow approach an asymptotic state of local thermal equilibrium whereas in Gubser flow the expansion is so strong that the asymptotic state is free-streaming. Anisotropic hydrodynamics can be understood as a form of resummed hydrodynamics that includes terms of all orders in a gradient or Chapman-Enskog expansion. We study the evolution of the longitudinal-transverse pressure anisotropy, the shear stress and the rate of entropy production and show that for all three observables second-order anisotropic hydrodynamics in the $P_L$-matching scheme yields the best agreement with the exact solution of the Boltzmann equation, for both types of flows. We also show that the relatively largest discrepancies between the approximate hydrodynamic and exact kinetic solutions are observed for the entropy: the rate of entropy productions appears to be more strongly affected by couplings to rapidly evolving non-hydrodynamic modes than the hydrodynamic moments of the distribution function that make up the energy-momentum tensor. Phenomenological implications of these findings will be discussed.

Speaker: Ulrich Heinz (The Ohio State University)

Heinz_QM18_final.pdf

626 Forward di-hadron back-to-back correlations in p+A collisions at RHIC and the LHC

The suppression of the away-side peak in azimuthal correlations of forward di-hadrons in d+Au vs. p+p collisions observed at RHIC remains one of the most striking experimental evidences supporting the saturation regime of quantum chromodynamics. Within the Color Glass Condensate (CGC) framework, we improve the state-of-the-art description of this observable, by deriving a cross section for the production of hadron pairs in the back-to-back limit. In this configuration, the cross section is manifestly factorized into a dilute component, the projectile proton, described by standard collinear parton distribution functions, and a dense counterpart, the saturated nuclear target, which is described by means of transverse-momentum-dependent gluon distributions, whose small-x evolution we obtain by solving the running-coupling Balitsky-Kovchegov equation. This formalism has proven able to accurately capture the suppression of the away-side peak observed in RHIC data.

Starting from this approach, then, we argue that the forward two-particle correlation function measured by the LHCb Collaboration in central p+Pb collisions at $\sqrt{s}=5.02$ TeV is amenable to a CGC description. In particular, we show that the away-side peak observed at LHCb can be decomposed into a double-ridge structure - whose origin is not our concern - and a di-jet structure, whose away-side peak is sensitive to parton saturation effects. We show that our formalism correctly describes the away-side peak measured at LHCb in p+Pb collisions, and we make predictions upcoming p+p data at 5 TeV. Comparing our results in p+p to LHCb data, the observation made at RHIC is replicated: We predict a visible suppression of the away-side peak in forward p+Pb collisions at LHC energies. This finding, if confirmed in experiment, would end up providing the best evidence in favor of QCD saturation in LHC data.

Speaker: Cyrille Marquet (CPHT - Ecole Polytechnique)

venice18.pdf

Jet modifications and high-pT hadrons: V

Convener: Julia Velkovska (Vanderbilt University (US))

627 Precision Dijet Acoplanarity Tomography of the Chromo Structure of Perfect QCD Fluids

Dijet azimuthal acoplanarity is dominated by vacuum pQCD radiation always associated with hard jet production. Jet-medium interactions broaden the vacuum Sudakov azimuthal angle distributions. In the Gaussian approximation (A.H.Mueller et al 2016) the broadening rms $\Delta\phi_{G} \sim \sqrt{<\hat{q}(T,E) L>}/E$ depends only on the jet path $L$ averaged transport coefficient $\hat{q}$. We focus on the rarer non-Gaussian “Landau tail” $\Delta \phi_G \ll \Delta \phi$ finite scattering induced fluctuations that are more sensitive to the detailed microscopic chromo-electric and chromo-magnetic structure of prefect QCD fluids. We estimate the magnitude of experimental precision needed in future dijet experiments to discriminate between perturbative QCD/HTL screened color electric q+g color structure and possible non-perturbative color bleached semi-QGP plus emergent magnetic Monopole (sQGMP) color structure of QCD perfect fluids using a new event by event version, CIBJET (S.Shi et al 2018), of the CUJET3 (JHEP 1602 (2016) 169) framework that combines ebe viscous hydro with finite opacity medium induced jet energy loss.

Speaker: Prof. Miklos Gyulassy (Columbia University)

MGyulassy-QM18-051618-vf1.1.pdf

MGyulassy-QM18-051618-vf2.pdf

628 Probing properties of the medium using jet substructure techniques in pp and PbPb collisions at 5.02 TeV with CMS

We present recent results on measurements of jet substructures using grooming techniques with pp and PbPb data collected with the CMS detector at a center-of-mass energy of 5.02 TeV per nucleon pair. Jet grooming techniques are used to focus on the hard structure of the jet by extracting the two subjets corresponding to the hardest parton splitting. This allows to study the properties of medium-induced gluon emissions and the evolution of partons through dense QCD matter. The hard jet structure is also sensitive to the role of (de)coherent gluon emitters. Results and prospects of the transverse momentum balance, mass and angular difference of the two hard subjets over a wide range of jet transverse momentum and various collision centrality selections are discussed.

Speaker: Yi Chen (CERN)

20180516_JetSubstructureCMS_QuarkMatter2018_YiChen_v7.pdf

629 Quantifying jet modifications with substructure

The striking suppression and modification patterns that are observed in jet observables measured in heavy-ion collisions, with respect to the proton-proton baseline, have the potential to constrain the spatio-temporal branching process of energetic partons in a dense QCD medium. The mechanism of jet energy loss in a deconfined medium is intricately associated with medium resolution of jet substructure fluctuations [1]. This is naturally accompanied by modifications of jet substructure [2,3] and impacts the behaviour of the suppression of jets at high-pT [4]. In this work, we highlight the connection between the breakdown of colour coherence and energy loss within a first-principle calculation of a parton splitting process taking place inside the medium [1]. Furthermore, we discuss how a consistent picture between quenching effects and substructure modifications can aid in pinning down scales of the medium, focussing in particular on the advantage of applying grooming techniques to enhance the sensitivity to perturbative aspects of in-medium jet fragmentation [2].

References:
[1] Y. Mehtar-Tani and Konrad Tywoniuk "Radiative energy loss of neighboring subjets" arXiv:1706.06047
[2] Y. Mehtar-Tani and Konrad Tywoniuk "Groomed jets in heavy-ion collisions: sensitivity to medium-induced bremsstrahlung " arXiv:1610.08930
[3] Y. Mehtar-Tani and Konrad Tywoniuk, in preparation
[4] Y. Mehtar-Tani and Konrad Tywoniuk "Quenching of high-pT jet spectra" arXiv:1707.07361

Speaker: Konrad Tywoniuk (CERN)

QM2018_Tywoniuk.pdf

630 Event-by-event jet suppression, anisotropy and hard-soft tomography

A consistent description of high pT particle suppression ($R_{AA}$) and azimuthal anisotropy $v_2$ has been a puzzle in the study of jet quenching, pointing to some non-perturbative native of jet transport. Event-by-event single inclusive jet suppression and azimuthal anisotropy are studied within the Linear Boltzmann Transport (LBT) model for jet propagation in QGP medium from 3+1D hydrodynamic evolution with fluctuating initial conditions. We demonstrate that LBT can describe both the single inclusive jet suppression and azimuthal anisotropy with a single adjustable parameter- effective strong coupling constant $\alpha_s$. This indicate observed jet quenching puzzle might be caused by non-perturbative phenomenon in hadronization at intermediate $p_T$. We also studied the energy and centrality dependence and the effect of fluctuation as compared to a smooth hydro evolution. A linear relationship is found between high $p_T$ jet anisotropy due to jet quenching and soft hadron anisotropy from hydrodynamic expansion

Speaker: Prof. Xin-Nian Wang (Central China Normal Univ / Lawrence Berkeley National Lab)

qm2018-xnwang.pdf

qm2018-xnwang.pptx

631 Exploring jet profiles in pp and Pb-Pb collisions at 2.76 and 5.02 TeV with the ALICE detector

Jets, defined as collimated sprays of particles originating from initial hard scattered partons, serve as well calibrated probes of the Quark-Gluon Plasma formed in high-energy nuclear collisions. Their production cross section and geometrical profile in elementary pp collisions is precisely calculable within the framework of perturbative QCD (pQCD). Hence, any modification of its production observed in heavy-ion collisions compared to an incoherent sum of
individual pp collisions could be attributed to in-medium effects. Such modifications, called jet quenching, have been measured in high-energy heavy-ion collisions both at RHIC and at the LHC, and they were interpreted as partonic energy loss in the QGP.

In this contribution, the measurements of inclusive charged jet spectra for jet resolution R = 0.2, 0.3, 0.4 and 0.6 in pp and R = 0.2, 0.3, 0.4 in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV will be presented. The nuclear modification factors in different centrality and R bins, and comparisons to the results at $\sqrt{s_{\rm NN}} = 2.76$ TeV and pQCD based Monte Carlo simulations will be presented. This allows to explore the radial energy profile of jets via measurements of jet yield ratios in different resolution parameter R in an IR-safe fashion.

The results of jet-hadron correlation measurements in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV for charged jets and fully reconstructed jets will also be presented. The associated hadron yields of inclusive and recoil jets were measured. Jet and associated hadron correlation widths have also been measured to constrain possible modifications of the jet shape. The measurements are compared to the baseline constructed from pp data, which is embedded into Pb-Pb data. Comparison to model predictions will also be shown. To study the influence of the large combinatorial background in Pb-Pb collisions, as well the jets surface bias, the measurement has been performed
for jets reconstructed with several constituent energy and momentum cuts.

Speaker: Ritsuya Hosokawa (University of Tsukuba (JP))

QM2018_JE_JetSpectra_v5.pdf

632 Medium response and jet shape modification in quark-gluon plasma

In this talk, we present the MARTINI study of the modification of jet shapes in quark-gluon plasma. The focus of this study is the effect of medium response on the jet shape function in PbPb collisions at $\sqrt{s}$ = 2.76 and 5.02TeV. As a jet parton propagates, the medium must respond to the energy and momentum
deposited by the jet parton. The medium response thus re-distributes the lost energy around the jet axis, which manifests as the change in the jet-shape function.

To realize the effect of the medium back-reaction, we start with an IP-Glasma event with the corresponding map of binary collisions. The IP-Glasma event then initializes a 3+1D MUSIC hydro event while the map is used to initiate PYTHIA jets. After the initial hydro runs, we let jets propagate in the evolving medium and record the loss of the energy-momentum along the trajectories, keeping careful track of recoiling thermal partons as well as the jet parton shower. MUSIC is then re-run with the same initial condition but with the additional energy-momentum sources representing the lost energy-momentum of the hard partons, and this time we include the UrQMD afterburner. The hadronized hard partons are then combined with the soft hadrons for the reconstruction of jets. Using this realistic event-by-event simulation, we show that the presence of the medium back-reaction including the effect of recoiling thermal partons significantly influences the jet shape function.

Speaker: Chanwook Park (McGill University)

Chanwook_Park_QM2018.pdf

Quarkonia: III

Convener: Yasuyuki Akiba (RIKEN)

633 Quarkonium production in p-A collisions with ALICE

The study of quarkonium production in proton-nucleus collisions is an important tool to investigate cold nuclear matter (CNM) effects. Mechanisms such as the modification of the parton distribution functions in nuclei, the presence of a color glass condensate or coherent energy loss of the $c\overline{c}$ pair in the medium have been employed to describe J/$\psi$ production in proton-nucleus collisions at LHC energies. In addition, final state mechanisms, possibly related to the presence of a dense medium, are required to explain the stronger suppression observed for the loosely bound $\psi$(2S) state.

ALICE has measured quarkonium production in p-Pb collisions at backward ($-$4.46 $<$ $y_{\rm cms}$ $<$ $-$2.96), mid ($-$1.37 $<$ $y_{\rm cms}$ $<$ 0.43) and forward (2.03 $<$ $y_{\rm cms}$ $<$ 3.53) rapidity down to zero transverse momentum ($p_{\rm T}$). Results on J/$\psi$ nuclear modification factor ($R_{\rm pPb}$) measured at mid-$y$ at $\sqrt{s_{\rm NN}}$ = 5.02 TeV and at forward and backward $y$ at $\sqrt{s_{\rm NN}}$ = 8.16 TeV will be presented. J/$\psi$ production as a function of multiplicity and results on the J/$\psi$ $v_{2}$, obtained using J/$\psi$-hadron correlations, will also be discussed. Finally, we will present the results on $\psi$(2S) and $\Upsilon$ $R_{\rm pPb}$ in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 8.16 TeV at forward and backward $y$. All the results will be compared to those obtained at lower energies and with available theoretical calculations.

Speaker: Dr Biswarup Paul (Universita e INFN Torino (IT))

QM18_16thMay2018_Biswarup.pdf

634 Beyond nPDF effects: prompt J/$\psi$ and $\psi(2S)$ production in pPb collisions with CMS detector

A multi-dimensional analysis of prompt charmonia in pp and pPb collisions at 5.02 TeV with the CMS detector is presented. The pPb differential cross-sections of prompt J/$\psi$ are shown in a wide kinematic region, for transverse momentum p$_T$ spanning from 2 to 30 GeV/c and a rapidity interval between -2.87 to 1.93 in the center of mass of the collision. The ratio of yields in forward (p-going beam) and backward (Pb-going beam) directions, R$_{\mathrm{FB}}$, is measured, to quantify the asymmetry of cross-sections as a function of p$_T$, rapidity, and event activity. A significant asymmetry is observed for $2

Speaker: Geonhee Oh (Chonnam National University (KR))

Geonhee_QM2018_vF.pdf

635 Results for RHIC and LHC in a unified framework for Heavy Flavor and Quarkonium production in high multiplicity p+p and p+A collisions

Heavy quark pair production in minimum bias p+p and p+A collisions has been studied extensively in the CGC framework and compared successfully to both the RHIC and LHC data on $J/\psi$ production [1, 2], $\psi(2S)$ production [3] and $D$-meson production [4]. We first present an update in this framework based on comparisons to the latest LHC and RHIC data on p+p and light-heavy ion collisions. We will then present novel results [5] on extensions of these studies of Heavy Flavor and Quarkonia to rare events; this work, in completion, demonstrates that this framework captures the systematics of both Heavy-Flavor and Quarkonium production as a function of $N_{\rm charge}$ at both RHIC and the LHC. Finally, we will discuss the importance of Sudakov resummations in this framework to describe $\Upsilon$ production [6, 7].

[1] Y. Q. Ma and R. Venugopalan, Phys. Rev. Lett. 113, no. 19, 192301 (2014).
[2] Y. Q. Ma, R. Venugopalan and H. F. Zhang, Phys. Rev. D 92, 071901 (2015).
[3] Y. Q. Ma, R. Venugopalan, K. Watanabe and H. F. Zhang, arXiv:1707.07266 [hep-ph].
[4] H. Fujii and K. Watanabe, Nucl. Phys. A 920, 78 (2013).
[5] Y. Q. Ma, P. Tribedy, R. Venugopalan, and K. Watanabe, in preparation.
[6] K. Watanabe and B. W. Xiao, Phys. Rev. D 92, no. 11, 111502 (2015).
[7] J. W. Qiu and K. Watanabe, arXiv:1710.06928 [hep-ph].

Speaker: Kazuhiro Watanabe (ODU/JLab)

QM18-Watanabe-v1.pdf

636 Quarkonium Production and Polarization in an Improved Color Evaporation Model

An improved version of the color evaporation model (ICEM) has been introduced to describe heavy quarkonium production [1]. In contrast to the traditional color evaporation model, the constraint was imposed that the invariant mass of the intermediate heavy quark-antiquark pair must be larger than the mass of produced quarkonium. A momentum shift between heavy quark-antiquark pair and the quarkonium was also introduced. Calculations show that the model can describe the charmonium yields as well as ratio of $\psi^\prime$ over $J/\psi$ better than the traditional color evaporation model.

The ICEM has been extended to calculate the polarization of prompt $J/\psi$ and $\Upsilon$(1S) production for the first time in the color evaporation approach. The first calculations were made at leading order. The polarization parameter $\lambda_\vartheta$ was calculated as a function of center of mass energy and rapidity in $p+p$ collisions. The $x_F$ dependence of the polarization was also calculated and compared to experimental results in $p$+Cu and $\pi$+W collisions [2,3]. The next step of calculating the $p_T$ dependence of the polarization has been taken, with a calculation in the $k_T$-factorization approach [4].

This talk will compare the unpolarized $p_T$ distributions for the $J/\psi$ and $\psi'$, as well as the $\psi'$ to $J/\psi$ ratio, in $p+p$ collisions at RHIC and the LHC for several energies. It will also present the polarization results and make comparison to polarization data from RHIC, the Tevatron and the LHC.

[1] Y.-Q. Ma and R. Vogt, Phys. Rev. D {\bf 94} (2016) 114029.

[2] V. Cheung and R. Vogt, Phys. Rev. D {\bf 95} (2017) 074021.

[3] V. Cheung and R. Vogt, Phys. Rev. D {\bf 96} (2017) 054014.

[4] V. Cheung and R. Vogt, in preparation.

Speaker: Ramona Vogt (LLNL)

QM_Venice_18.pdf

637 Quarkonia productions in heavy ion collisions: coupled Boltzmann transport equations

Quarkonia can be used as probes of quark-gluon plasma (QGP), a hot nuclear environment produced in heavy ion collisions. Quarkonia become unbound or "melt" at sufficiently high temperature due to the significant screening of the color attraction. In this sense, quarkonia can be thought of as thermometers of QGP. But extracting the melting temperature from experimental measurements is much involved. To this end, we develop a set of coupled Boltzmann transport equations of heavy quarks and quarkonia. It includes elastic and inelastic scattering of heavy quarks with the medium, dissociations and recombinations (in-medium formations) of quarkonia. The dissociation and recombination processes are calculated in potential non-relativistic QCD (pNRQCD). The effective field theory pNRQCD is valid because the heavy quark mass is large and the distance between the heavy quark antiquark pair is small inside quarkonia, compared with the thermal scales. We solve the Boltzmann equations by Monte Carlo simulations with given initial conditions and medium backgrounds. We will present how the system of heavy quarks and quarkonia approaches equilibrium in a static QGP box, which indicates that the dissociation and recombination are implemented in a consistent way. Then we will present calculations with realistic initial conditions and hydrodynamical backgrounds. The initial momenta of heavy quarks and quarkonia are generated from event generators such as Pythia with nuclear parton distribution functions while the initial positions are sampled from binary collisions. We will also compare the calculations with experimental measurements. Finally, we will discuss future plans towards a more complete understanding of quarkonia production mechanisms in heavy ion collisions.

Speaker: Xiaojun Yao (Duke University)

QM18_XiaojunYao_May16.pdf

638 Testing charm quark thermalisation within the statistical hadronisation model

A wealth of data on charmonium production from the major LHC experiments has provided strong evidence for (re-)generation as a dominant production mechanism at low transverse momentum. To make further progress in the understanding of the underlying physics we present an important extension of the statistical hadronisation model to describe J/$\psi$ transverse momentum distributions based on input parameters from hydrodynamical simulations. Comparison to the data allows the testing of the degree of thermalisation of charm quarks in the quark-gluon plasma. To this end we will report analyses of the centrality dependence of J/$\psi$ transverse momentum spectra in Pb-Pb collisions at $\sqrt{s_{NN}} = 2.76$ and $5$ TeV. The studies can be naturally extended to the b-quark sector.

Speaker: Markus Kohler (Ruprecht-Karls-Universitaet Heidelberg (DE))

mkk_QM2018.pdf

Thursday, 17 May

Plenary: IV

Convener: Bikash Sinha (Variable Energy Cyclotron Centre, Kolkata, India)

639 Chiral Magnetic Effect and Vorticity in nuclear collisions

Speaker: Zhoudunming Tu (Rice University (US))

Chirality_Vorticity_Kong_QM2018_v1.pdf

640 Polarization and chirality: the quantum features of the Quark Gluon Plasma

Speaker: Francesco Becattini (Unversity of Florence)

becattini.pdf

641 Strangeness and nuclei production in nuclear collisions

Speaker: Stefania Bufalino (Politecnico di Torino (IT))

SBufalino_QM2018_final.pdf

10:30 Coffee Break

Plenary: V

Convener: Jurgen Schukraft (CERN)

642 Collective effects in nuclear collisions

Speaker: You Zhou (University of Copenhagen (DK))

QM_YouZhou.pdf

643 Collective effects in nuclear collisions: theory overview

Speaker: Jorge Noronha (University of Sao Paulo)

Noronha_QM_plenary_2018.pdf

644 Study of small colliding systems

Speaker: Li Yi (Yale University)

SmallSystem_YiLi_1805_v10.pdf

645 Small system studies: theory overview

Speaker: Michael Strickland (Kent State University)

strickland_v9.pdf

strickland_v9.pptx

646 Initiatives for diversity in Physics

Speaker: Ioanna Koutava (CERN)

Initiatives for Diversity - Quark Matter 2018.pdf

Initiatives for Diversity - Quark Matter 2018.pptx

13:30 Lunch box collection, then free afternoon

Friday, 18 May

Plenary: VI

Convener: Hannah Petersen

647 Measurement of fluctuations in nuclear collisions

Speaker: Rosi Jan Reed (Lehigh University)

RReedQM2018v5.pdf

648 Exploring baryon-rich QCD matter and search for the QCD critical point: a theoretical perspective

Speaker: Yi Yin (MIT)

QM_planery_YiYin_vMay17.pdf

649 High-temperature QCD: theory overview

Speaker: Massimo D'Elia (University of Pisa)

qm2018_delia.pdf

10:30 Coffee Break

Plenary: VII

Convener: Roberta Arnaldi (Universita e INFN Torino (IT))

650 Open heavy flavour production in nuclear collisions

Speaker: Elena Bruna (Universita e INFN Torino (IT))

ebruna_QM18_v2.pdf

651 Open heavy flavour: theory overview

Speaker: Pol Gossiaux (Subatech)

QM_Gossiaux - 1609.pdf

652 Quarkonium production in nuclear collisions

Speaker: Rongrong Ma (BNL)

RMa_QM18_Quarkonia_v5.pdf

653 Quarkonium: theory overview

Speaker: Elena Gonzalez Ferreiro (Universidade de Santiago de Compostela (ES))

Ferreiro_QM2018_7c.pdf

13:00 Lunch

Plenary: VIII

Convener: Berndt Mueller (Brookhaven National Laboratory)

654 Initial stages of nuclear collisions: theory overview

Speaker: Aleksas Mazeliauskas (Universität Heidelberg)

Initial_stages_Mazeliauskas_QM18.pdf

655 Electroweak probes in nuclear collisions

Speaker: Norbert Novitzky (Helsinki Institute of Physics (FI))

QM2018Novitzky_v2.pdf

656 Studies of Ultra Peripheral Collisions

Speaker: Aaron Angerami (Lawrence Livermore National Laboratory)

angerami_QM2018.pdf

657 2018 Zimanyi Nuclear Theory Medal presentation

Zimany2018.pdf

16:10 Coffee Break

Plenary: IX

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

658 Jet modifications in nuclear collisions

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

sickles_051818_noanimations.pdf

sickles_051818.pdf

659 Jet quenching in nuclear collisions: theory overview

Speaker: Guilherme Milhano (LIP-Lisbon & CERN TH)

qm2018milhano.pdf

660 Modification of the jet structure in nuclear collisions: theory overview

Speaker: Gavin Salam (CERN)

QM2018-JetSub-Salam.pdf

661 Medium response to jet-induced excitation: theory overview

Speaker: Yasuki Tachibana (CCNU Wuhan)

tachibana_qm_18.pdf

662 QM2018 photographic contest awards

QM2018pc.pdf

Banquet

Saturday, 19 May

Plenary: X

Convener: Norbert Herrmann (Univ. Heidelberg)

663 Future plans for electron-ion colliders

Speaker: Jin Huang (Brookhaven National Lab)

Huang_EIC.pdf

Huang_EIC.pptx

664 Future facilities for high mu_B physics

Speaker: Tetyana Galatyuk (TU Darmstadt / GSI)

2018_05_18_TetyanaGalatyuk_Future_f.pptx

665 The future of high-energy heavy-ion facilities

Speaker: Jan Fiete Grosse-Oetringhaus (CERN)

JFGO11p.pdf

10:30 Coffee Break

666 Elsevier Young Scientist awards

Speakers: Chiara Farinelli (NIKHEF (NL)), Maria Paola Lombardo (INFN), Peter Braun-Munzinger (GSI - Helmholtzzentrum fur Schwerionenforschung GmbH (DE))

QM_YoungScientistAwards_2018.pdf

QM_YoungScientistAwards_2018.pptx

Best-poster flash talks

Convener: Enrico Scomparin (Universita e INFN (IT))

667 Measurement of jet fragmentation in pp, p+Pb and Pb+Pb collisions with ATLAS

Speaker: Akshat Puri (Univ. Illinois at Urbana Champaign (US))

flashtalk.pdf

668 Energy dependence of phi (1020) production at mid-rapidity in pp collisions with ALICE at the LHC

Speaker: Sushanta Tripathy (Indian Institute of Technology Indore (IN))

Sushanta_FlashTalk_phi_QM18.pdf

669 Equation of state for QCD with a critical point from the 3D Ising Model

Speaker: Paolo Parotto (University of Houston)

Flash_Talk_Parotto_QM2018.pdf

670 J/psi in jets in pp collisions at 5.02 TeV with the CMS experiment

Speaker: Batoul Diab (Centre National de la Recherche Scientifique (FR))

BatoulDiabQM18FlashTalk.pdf

671 Direct flow of heavy mesons as unique probes of the initial Electro-Magnetic fields in Ultra-Relativistic Heavy Ion collisions

Speaker: Gabriele Coci (INFN - National Institute for Nuclear Physics)

GCoci_QM18flashtalk.pdf

672 Dimuon Invariant Mass Spectra with the Muon Telescope Detector at STAR in p+p collisions at 200 GeV

Speaker: James Brandenburg (Rice University)

jdb_FlashTalk_QM18_final.pdf

673 Direct photon flow in ALICE

Speaker: Mike Henry Petrus Sas (Nikhef National institute for subatomic physics (NL))

msas_flashtalk_QM.pdf

674 The curvature of the pseudocritical line from lattice QCD: Taylor expansion and Analytic continuation compared

Speaker: Francesco Negro (INFN - Sezione di Pisa)

flashqm18negro.pdf

675 f0(980) resonance production in pp collisions with the ALICE detector at LHC

Speaker: Alessandra Lorenzo (Universita e INFN, Bologna (IT))

Lorenzo_FlashTalk_QM18_v04.pdf

676 Non-linear dynamical systems approach to out of equilibrium hydrodynamical attractors: the Gubser flow case

Speaker: Mr Nikolás Cruz Camacho (Universidad Nacional de Colombia)

Flash_Talk_Nikolas_Cruz_NTH1.pdf

Plenary: XI

Conveners: Enke Wang (Central China Normal University), Feng Liu (Central China Normal University)

677 Summary talk

Speaker: Marco Van Leeuwen (Nikhef National institute for subatomic physics (NL))

QM2018_summary.pdf

678 Presentation of QM2019 - Wuhan

Speakers: Feng Liu (Central China Normal University), Enke Wang (Central China Normal University)

QM2019_wuhan_v5.pdf

QM2019_wuhan_v5.pptx

679 QM2018 closing