Bulletin of the American Physical Society
6th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Sunday–Friday, November 26–December 1 2023; Hawaii, the Big Island
Session F14: Relativistic Heavy Ions II |
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Chair: Ron Soltz, Lawrence Livermore Natl Lab Room: Hilton Waikoloa Village Kohala 4 |
Thursday, November 30, 2023 9:00AM - 9:15AM |
F14.00001: Status Report on the Analyses of Proton-Number Cumulants in the STAR Fixed-Target Program Zachary Sweger Fluctuations of net-proton number distributions in heavy-ion collisions are expected to be sensitive to a QCD critical point. These fluctuations are measured through various-order cumulants, $C_n$, of net-proton multiplicity distributions. The collision-energy dependence of net-proton cumulant ratio from Beam Energy Scan I shows a hint of deviation from the baseline between $sqrt{s_{NN}}=$ 19.6~GeV to 7.7~GeV, while the recent proton $C_4/C_2$ value at $sqrt{s_{NN}}=$ 3~GeV from the Fixed-Target program (FXT) at STAR returns to the baseline. These results indicate the importance of filling the gap between $sqrt{s_{NN}}=$ 3.0~GeV and 7.7~GeV. The analyses of the remaining FXT data are ongoing, although analysis of the STAR fixed-target data comes with challenges. A shifting mid-rapidity with beam energy results in acceptance gaps at some energies, and a reliance on time-of-flight particle identification at top FXT energies necessitates a thorough understanding of the effect of precision timing on proton-number cumulants. These and other challenges and techniques used in the analyses of FXT proton cumulants will be presented, and the status of the analyses will be discussed. |
Thursday, November 30, 2023 9:15AM - 9:30AM |
F14.00002: Anomalous kaon correlations in Pb--Pb collisions at the LHC with ALICE Anjaly Sasikumar Menon Two-particle correlation functions provide critical information about the medium quark--gluon plasma (QGP) created in heavy-ion collisions. Recent ALICE measurements have demonstrated large dynamical correlations between produced neutral and charged kaons in Pb--Pb collisions at $sqrt{s_{
m{NN}}} = 2.76 $ TeV~cite{ALICE:2021fpb}. These integrated correlations cannot be described by conventional heavy-ion models, such as EPOS and AMPT. So far, the ALICE measurements can only be described by invoking the presence of condensates ~cite{Kapusta:2022ovq}. A candidate for such a condensate is the Disoriented Chiral Condensate (DCC)~cite{Mohanty:2005mv}. DCC arises from chiral symmetry restoration in the QGP, which breaks during the phase transition to form a condensate which coherently emits hadrons. Therefore, the discovery of DCC would indicate that chiral symmetry is restored in the QGP, a major prediction of QGP formation that has yet to be confirmed experimentally. |
Thursday, November 30, 2023 9:30AM - 9:45AM |
F14.00003: Rapidity Dependence of π+/-, K+/-, p, and Antiproton Production in BES-II √sNN = 7.7 to 27 GeV Au+Au Collisions at STAR Matthew D Harasty The first phase of the Beam Energy Scan (BES-I) at the Relativistic Heavy Ion Collider (RHIC) covered a range of energies from √sNN = 7.7 to 200 GeV, which ended in 2014. The success of the BES-I program justified a new energy scan (BES-II) with higher statistics and detector upgrades. This BES-II analysis will extend the measurements of transverse mass spectra and production yields of π+/-, K+/-, p, and antiproton beyond the mid-rapidity results of BES-I at √sNN = 7.7 to 27 GeV. The transverse mass spectra are crucial to pin down the location of each collision energy at chemical freeze-out on the QCD phase diagram. We will also present a study of the relative particle yields in different rapidity regions, which will be used to investigate how the chemical freeze-out temperature and chemical potentials vary with rapidity. Our results indicate that we can sample an area of the QCD phase diagram in temperature and baryon chemical potential by varying not only the collision energy, but also rapidity and centrality, which will aid in the search for the critical point. |
Thursday, November 30, 2023 9:45AM - 10:00AM |
F14.00004: Mean pT fluctuations in 3.0 GeV fixed-target collisions from the STAR experiment Rutik Manikandhan, Rene Bellwied, Tapan Nayak The mean pT fluctuations in heavy-ion collisions can be related to temperature fluctuations which quantify the specific heat of the system. Any deviations from the Hadron |
Thursday, November 30, 2023 10:00AM - 10:15AM |
F14.00005: Measurements of π, K, p spectra in fixed target collisions with STAR Mathias Labonte One of the main physics goals of the Beam Energy Scan (BES) at RHIC is to study the QCD phase diagram, especially around the phase transition |
Thursday, November 30, 2023 10:15AM - 10:30AM |
F14.00006: sPHENIX Plans for Bulk Physics Ejiro N Umaka Situated at RHIC, sPHENIX is a new collider detector designed for studies of the Quark-Gluon-Plasma via jet and heavy flavor probes. In addition to the purpose of its original design, the large acceptance, excellent tracking efficiency, high data-taking rate and sub-detectors located in the forward and backward region allows for the study of soft particle production and collective flow. sPHENIX is currently being commissioned with Au+Au collisions at 200 GeV. |
Thursday, November 30, 2023 10:30AM - 10:45AM |
F14.00007: Event-by-event fluctuations on light-nuclei production in coalescence model Koichi Murase, Shanjin Wu We investigate how the event-by-event fluctuations of the final-state distribution function of nucleons physically affect the yield ratio of light nuclei based on the coalescence model. |
Thursday, November 30, 2023 10:45AM - 11:00AM |
F14.00008: Analysis of temperature gradient effects on thermodynamic properties of relativistic scalar field model Daiki Miura, Masaru Hongo Recent experimental and theoretical investigations have revealed that relativistic heavy ion collisions lead to the formation of a quark-gluon plasma (QGP), which behaves as an almost perfect fluid described by relativistic hydrodynamic models . The hydrodynamic equations used in these models have been conventionally relied on a derivative expansion, assuming that spatial derivatives of local thermodynamic quantities (e.g., temperature) are sufficiently small. |
Thursday, November 30, 2023 11:00AM - 11:15AM |
F14.00009: Role of U(1) axial anomaly in two-color dense QCD Mamiya Kawaguchi, Daiki Suenaga The anomaly of U(1) axial symmetry is an important element of the quantum chromodynamics (QCD), which affects the hadron mass spectrum and the chiral phase transition in QCD matter. However, its role in the baryonic QCD matter is not well understood compared to hot medium. In this talk, I will discuss the role of the U(1) axial anomaly by exploring the topological susceptibility at finite quark chemical potential and zero temperature in two-color QCD with two flavors. By using the Ward-Takahashi identities of QCD, we find that the topological susceptibility in hadronic phase is described by only three observables: the pion decay constant, the pion mass, and the eta meson mass in the low-energy regime of two-color QCD. Based on the identities, we numerically evaluate the topological susceptibility at finite quark chemical potential using the linear sigma model which undergoes the baryon superfluid phase transition. Our findings indicate that the nonzero topological susceptibility is induced by the presence of the U(1) axial anomalous interaction, reflecting the mass difference between the pion and eta meson. Moving on to the superfluid phase, it turns to decrease smoothly. The asymptotic behavior of the decrement is fitted by the continuous reduction of the chiral condensate in dense two-color QCD. In addition, effects from the finite diquark source on the topological susceptibility will be also discussed. |
Thursday, November 30, 2023 11:15AM - 11:30AM |
F14.00010: T-matrix Analysis of Static Wilson Line Correlators from Lattice QCD at Finite Temperature Zhanduo Tang, Swagato Mukherjee, Peter Petreczky, Ralf F Rapp We utilize a previously constructed thermodynamic T-matrix approach to the quark-gluon plasma (QGP) to calculate Wilson line correlators (WLCs) of a static quark antiquark pair and apply them to the results from realistic 2+1-flavor lattice-QCD (lQCD) computations. The pertinent T-matrix results can describe the lQCD data for WLCs fairly well, but refinements of the input parameters are necessary to improve the agreement, providing new insights. This renders the T-matrix a more accurate and reliable tool to make predictions for the spectral and transport properties of the QGP, i.e., the charm-quark spatial diffusion coefficients turn out to be in agreement with lQCD results. |
Thursday, November 30, 2023 11:30AM - 11:45AM |
F14.00011: Cooper-Frye sampling with short-range repulsion Volodymyr Vovchenko We incorporate the effect of short-range repulsion among hadrons into the Cooper-Frye sampling procedure through a rejection sampling step that prohibits any pair of particles from overlapping in the coordinate space, effectively modeling the effect of hard-core repulsion. It is then applied to study the effect of excluded volume on proton number cumulants in central collisions of heavy ions in conjunction with exact global conservation of baryon number, electric charge, and strangeness. The results are compared with earlier calculations based on analytical approximations, quantifying the latter's accuracy at different collision energies. An additional advantage of the new method over the analytic approaches is that it offers the flexibility provided by event generators, making it straightforwardly extendable to other observables. The new procedure is called the FIST sampler and is now incorporated in the open-source package Thermal-FIST since version 1.4. |
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