Bulletin of the American Physical Society
APS April Meeting 2021
Volume 66, Number 5
Saturday–Tuesday, April 17–20, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session Q12: Beam Energy ScanLive
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Sponsoring Units: DNP Chair: Deepa Thomas, UT Austin |
Monday, April 19, 2021 10:45AM - 10:57AM Live |
Q12.00001: Energy dependence of forward-backward transverse momentum correlation from STAR Tongzhou Guo Transverse momentum correlations could serve as a powerful probe of the early dynamics of hadronic interactions in heavy ion collisions. The related correlation coefficient is constructed from event-by-event average transverse momentum in two separated pseudorapidity regions. We present measurements of the average transverse momentum correlation coefficient $\rho$ in Au+Au collisions from 27 to 200 GeV at STAR. Results of forward-backward correlations are compared with correlations between adjacent pseudorapidity regions. The centrality and pseudorapidity separation dependence of transverse momentum correlations has been discussed. [Preview Abstract] |
Monday, April 19, 2021 10:57AM - 11:09AM Live |
Q12.00002: Dielectron production in Au+Au collisions at $\sqrt{s_{\rm {NN}}}=54$ GeV at STAR Zhen Wang Dielectrons are excellent probes of the Quark-Gluon Plasma (QGP) created in high-energy heavy-ion collisions. Because they can be produced at all stages of the collision system evolution and do not interact with the medium strongly, dielectrons carry the information from the initial stage to the final stage. In the low mass region ($\rm M_{ee} < M_{\phi}$), the mass spectra of vector mesons will be modified by the hot and dense medium which is related to the chiral symmetry restoration in the medium. In the intermediate mass region ($\rm M_{\phi} < \rm M_{ee} < \rm M_{J/\psi}$), QGP thermal radiation can be used as a QGP thermometer. However, it is complicated to measure the QGP thermal radiation because of the heavy flavor semi-leptonic decay contributions. In this presentation, I will present the dielectron production in Au$+$Au collisions at $\sqrt{s_{\rm {NN}}}=54$ GeV at STAR. With a 10 times larger data sample than that at 62 GeV from the first phase of the STAR Beam Energy Scan (BES-I) program, in-medium $\rho$ modification can be studied with better precision and compared to different theoretical predictions. Furthermore, physics implications of these measurements will be discussed. [Preview Abstract] |
Monday, April 19, 2021 11:09AM - 11:21AM Live |
Q12.00003: Strangeness-Neutral Equation of State with an Ising-model Critical Point Angel Nava, Débora Mroczek, Jacquelyn Noronha-Hostler, Paolo Parotto, Damien Price, Claudia Ratti, Jamie Stafford We develop a family of strangeness-neutral Equations of State (EoS) for QCD, exhibiting critical behavior, matching the results on Taylor expansion coefficients from Lattice QCD, compatible with the SMASH hadronic transport approach, and in a range of temperature and baryonic chemical potential which is pertinent for phase II of the Beam Energy Scan at RHIC\footnote{D. Mroczek, A. R. Nava Acuna, J. Noronha-Hostler, P. Parotto, D. R. P. Price, C. Ratti, and J. M. Stafford, \textbf{Forthcoming publication}.}. With our implementation of strangeness neutrality conditions, the BES-EoS now serves to better reproduce the system in a heavy-ion collision, in which there is zero global strangeness density and a fixed ratio of electric charge to baryon number. In addition to the thermodynamic quantities that comprise the equation of state, we also show the isentropic trajectories and their transformations in a strangeness-neutral system, as well as the critical contribution to the correlation length. Finally, we compare our results with an earlier, non-strangeness-neutral version of the EoS\footnote{P. Parotto, M. Bluhm, D. Mroczek, M. Nahrgang, J. Noronha-Hostler, K. Rajagopal, C. Ratti, T. Schaefer, M. Stephanov, \textbf{ Phys. Rev.} C101 (2020) 034901.}. [Preview Abstract] |
Monday, April 19, 2021 11:21AM - 11:33AM Live |
Q12.00004: Non-equilibrium kinetic freeze-out properties in relativistic heavy ion collisions from RHIC Beam Energy Scan to LHC Jia Chen In this talk, we investigate the kinetic freeze-out properties in relativistic heavy ion collisions at different collision energies. We present a study of BGBW fits and TBW fits performed on $p_T$ spectra of identified hadrons produced in Au + Au collisions at collision energies of $\sqrt{s_{\rm{NN}}}=$ 7.7 - 200~GeV at RHIC, and in Pb + Pb collisions at collision energies of $\sqrt{s_{\rm{NN}}}=$ 2.76 and 5.02~TeV at LHC. The behavior of strange and multi-strange particles is also investigated. We found that the TBW model describes data better than the BGBW one overall, and the contrast is more prominent as the collision energy increases as the degree of non-equilibrium of the produced system is found to increase. From TBW fits, the kinetic freeze-out temperature at the same centrality shows a weak dependence of collision energy between 7.7 and 39~GeV, while it decreases as collision energy continues to increase up to 5.02~TeV. The radial flow is found to be consistent with zero in peripheral collisions at RHIC energies but sizable at LHC energies and central collisions at all RHIC energies. We also observed that the strange hadrons, with higher temperature and similar radial flow, approach equilibrium more quickly from peripheral to central collisions than light hadrons. [Preview Abstract] |
Monday, April 19, 2021 11:33AM - 11:45AM Live |
Q12.00005: Calculation of transverse energy from single particle momentum spectra Christine Nattrass, Biswas Sharma, Soren Sorensen, Ben Smith, Tanner Mengel, Charles Hughes, Nathan Webb In high energy heavy ion collisions, measurements of transverse energy ($E_T$) can constrain the initial energy density and therefore provide insight into the formation of the Quark Gluon Plasma (QGP). This is particularly interesting in regions where it is unclear if the QGP is formed. The $E_T$ in a collision can be measured either from a calorimeter or calculated from the single particle momentum spectra. We use spectra measured by the STAR collaboration to calculate the transverse energy in heavy ion collisions from the RHIC Beam Energy Scan. We use these calculations to calculate the distribution of $E_T$ by particle type. These calculations are compared to PHENIX measurements using a calorimeter. Prospects for similar calculations in small systems are discussed. [Preview Abstract] |
Monday, April 19, 2021 11:45AM - 11:57AM Live |
Q12.00006: Prospects of Dielectron Measurements with STAR BES-II Zaochen Ye Detailed studies of the dielectron mass spectrum in relativistic heavy-ion collisions can help to disentangle its various physics sources. In the intermediate mass range (IMR, $M_{\phi} |
Monday, April 19, 2021 11:57AM - 12:09PM Live |
Q12.00007: Strange Hadron Production in Au+Au Collisions at $\sqrt{S_{NN}}=54.4 GeV$ Yan Huang The RHIC Beam Energy Scan (BES) Program is proposed to study the Quantum Chromodynamics phase transition and to locate the onset of deconfinement. As a sensitive probe to the transition from the hadron gas to the Quark-Gluon Plasma, the particle ratios of strange hadrons are measured to study the properties of nuclear matter and extract the chemical freeze-out parameters\footnote{\textbf{Phys.Rev.C}102,034909(2020)}\footnote{\textbf{Phys.Rev.C}96,044904(2017)} . Recently, the production of strange hadrons ($K_{S}^{0}$,$\Lambda$,$\bar{\Lambda}$,$\Xi^{-}$,$\bar{\Xi}^{+}$,$\Omega^{-}$,$\bar{\Omega}^{+}$,and $\phi$) at mid-rapidity (|$\eta$|<0.5) in Au+Au collisions at $\sqrt{S_{NN}}=54.4 GeV$ are measured at the Relativistic Heavy Ion Collider STAR experiment. In this talk, transverse momentum spectra, nuclear modification factor $R_{cp}$, baryon-to-meson ratio, as well as the overall integrated yields of these strange hadrons at 54.4 $GeV$ are presented. In particular, the multi-strange baryon-to-meson ratio $N(\Omega^{-}+\bar{\Omega}^{+})/[2N(\phi)])$ at 54.4 $GeV$ is studied and compared to previous measurement at other BES energies\footnote{\textbf{Phys.Rev.C}93,021903(R)(2016)}. The strange-hadron-to-pion ratios versus charged hadron multiplicity are also studied. [Preview Abstract] |
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