Bulletin of the American Physical Society
Fall 2022 Meeting of the APS Division of Nuclear Physics
Volume 67, Number 17
Thursday–Sunday, October 27–30, 2022; Time Zone: Central Daylight Time, USA; New Orleans, Louisiana
Session PF: Bulk Matter and Correlations in Heavy-ion Collisions II |
Hide Abstracts |
Chair: Ron Soltz, Lawrence Livermore Natl Lab Room: Hyatt Regency Hotel Celestin F |
Sunday, October 30, 2022 10:30AM - 10:42AM |
PF.00001: Beam-energy dependence of transverse momentum and flow correlations in STAR Niseem M Abdelrahman Extraction of the transport properties of the quark-gluon plasma (QGP) is one of the central objectives of the heavy-ion program at the Relativistic Heavy-Ion Collider (RHIC). Measurements that are selectively sensitive to both initial-state effects and final-state viscous attenuation can provide invaluable constraints on temperature ($T$) and chemical potential ($\mu_{B}$) dependence of the specific shear viscosity $\eta/s$. The transverse-momentum-flow correlations $\rho(v^{2}_{n},\langle p_{T} \rangle)$, that measures the strength of the correlation between an event’s mean-transverse momentum $\langle p_{T} \rangle$ and its flow magnitude $v^{2}_{n}$, is expected to be more sensitivity to the initial-state than to final-state effects~[1,2]. A comprehensive set of $\rho(v^{2}_{n},\langle p_{T} \rangle)$ measurements for Au+Au collisions spanning the beam energy range of $\sqrt{s_{\rm NN}}$ = 19.6-200 GeV, will be presented for several centralities and event shape selections. The results, which show characteristic beam-energy-dependent trends, are compared to results at the LHC and calculations from several theoretical models. The data-model comparisons indicate that the measurements provide significant constraints on the respective influences of initial-state fluctuations, system-size, system-shape, and $\eta/s(\mu_{B},T)$. |
Sunday, October 30, 2022 10:42AM - 10:54AM |
PF.00002: Study the production of identified charged hadrons in Au+Au collisions at √sNN = 54.4 GeV using the STAR detector Arushi Dhamija Exploring the QCD phase diagram and searching for the QCD critical point are some of the main goals of the Beam Energy Scan program at RHIC. In 2017, the STAR experiment collected a large dataset of Au+Au collisions at $\sqrt{s_{NN}} =$ 54.4 GeV. The identified particle spectra and yields provide information about the bulk properties of the hot medium created in these collisions. The centrality dependence of the freeze-out parameters explores a wide ($T$, $\mu_B$) region in the phase diagram facilitating the search for the QCD critical point. We present the measurements of the production of $\pi$$^\pm$, K${^\pm}$, p, and $\bar{p}$. The results for the transverse momentum spectra, particle yields, average transverse momentum $\langle$p$_{T}$$\rangle$, and particle ratios will be presented for different centrality classes and compared with AMPT and HIJING model calculations. In addition, the extracted freeze-out parameters will be compared with the results at other collision energies. The physics implications of the results will be discussed. |
Sunday, October 30, 2022 10:54AM - 11:06AM |
PF.00003: Strange hadron production in d+Au collisions at √sNN = 200 GeV using the STAR detector Ishu Aggarwal Strangeness production has been suggested as a sensitive probe to the early dynamics of the deconfined matter created in heavy-ion collisions. Ratios of particle yields involving strange particles are often utilized to study freeze-out properties of the nuclear matter, such as the strangeness chemical potential and the chemical freeze-out temperature. $\rm{d}$+Au data connect between Au+Au and $pp$ collisions, and supply the baseline for the study of strangeness enhancement in the deconfined matter. The study of nuclear modification factor in $\rm{d}$+Au collisions can also help to understand Cronin-like effects. In this work, we will present new measurements on the production of strange hadrons ($K{_S}{^0}$, $\Lambda$, $\Xi$, $\Omega$) at mid-rapidity in $\rm{d}$+Au collisions at $\sqrt{s_{\rm{NN}}} =$ 200 GeV, recorded by the STAR experiment in 2016. We will report transverse momentum ($p_{\rm{T}}$) spectra, $p_{\rm{T}}$ integrated yield dN/dy, average transverse momentum, yield ratios, and nuclear modification factors for those strange hadrons. The physics implications of the measurement on the collision dynamics will be discussed. |
Sunday, October 30, 2022 11:06AM - 11:18AM |
PF.00004: Results from an improved RΨ2 observable in isobar collisions at STAR Charles Robertson The RΨ2 (∆S) observable, which quantifies charge separation (∆S) fluctuations perpendicular to the reaction plane relative to those parallel [1], has been used to search for the chiral magnetic effect (CME) in isobar (96 44Ru + 96 44Ru and 96 40Zr + 96 8 40Zr) collisions at nucleon-nucleon center-of-mass energy √ 9 sNN = 200 GeV by STAR [2]. Each event measured by the STAR Time Projection Chamber is divided into two subevents according to the particle pseudorapidity, where one is used to reconstruct an event plane as the proxy for the reaction plane and the other subevent is used to calculate ∆S, and vice versa. The ∆S is normalized by the width of the charge-shuffled ∆S parallel to the event plane, and the ∆S values from the two subevents are averaged. The Ru+Ru/Zr+Zr ratio of the squared inverse width of the RΨ2 (∆S) distribution, 1/σ2 RΨ2, is consistent with unity, indicating no evidence for the pre-defined CME signal [2]. In this talk, we present an improved definition of RΨ2 (∆S), where the ∆S values perpendicular and parallel to the event plane are normalized by the respective charge-shuffled widths, and the ∆S from the two subevents are not averaged but treated as independent quantities in the analysis [3]. We report preliminary results on this improved RΨ2 (∆S) observable. We make connections of the improved RΨ2 (∆S) to the ∆γ observable, and discuss our results in the context of the CME search. [1] N.N. Ajitanand, R.A. Lacey, A. Taranenko and J.M. Alexander, Phys. Rev. C 83, 011901 (2011). [2] M. Abdallah et al. (STAR Collaboration), Phys. Rev. C 105, 014901 (2022). [3] Y. Feng, J. Zhao, H.-j. Xu and F. Wang, Phys. Rev. C 103, 034912 (2021). |
Sunday, October 30, 2022 11:18AM - 11:30AM |
PF.00005: Measurements of Transverse Spin Dependent $\pi^+\pi^-$ Azimuthal Correlation Asymmetry and Unpolarized $\pi^+\pi^-$ Cross Section in $pp$ Collisions at $\sqrt s = 200$ GeV at STAR Babu R Pokhrel The transversity distribution function, $h_1^{q}(x)$, where $x$ is the longitudinal momentum fraction of the proton carried by quark $q$, encodes the proton's transverse spin structure at the leading twist. Extraction of it is difficult because of its chiral-odd nature. However, it can be coupled with a spin-dependent interference fragmentation function (FF), $H_1^{\sphericalangle, q}$, in polarized proton-proton ($p^\uparrow p$) collisions. The coupling of $h_1^{q}(x)$ and $H_1^{\sphericalangle, q}$ produces an experimentally measurable azimuthal correlation asymmetry, $A_{UT}$, between the spin of the fragmenting quark and the final state di-hadron. A model-independent extraction of transversity from these measurements relies on the knowledge of di-hadron FFs, namely the unpolarized di-hadron FFs. Extraction of these FFs requires measurements of the unpolarized di-hadron cross section in $pp$ collisions, which are desperately needed. We will present preliminary results on $A_{UT}$ for $\pi^+\pi^-$ pairs with $p^\uparrow p$ data at $\sqrt{s} = 200$ GeV taken in 2015, as well as an update on the unpolarized $\pi^+\pi^-$ cross-section measurement with the $pp$ data at $\sqrt{s} = 200$ GeV taken in 2012, at the STAR experiment. |
Sunday, October 30, 2022 11:30AM - 11:42AM |
PF.00006: Two-particle multiplicity and momentum correlations in relativistic nuclear collisions George S Moschelli, Sean Gavin, Zoulfekar Mazloum We introduce a two-particle correlation observable that measures multiplicity-momentum correlations and may facilitate an estimate of the level of equilibration of the medium created in relativistic nuclear collisions. We also discuss a mathematical connection between multiplicity-momentum correlations and three other two-particle momentum density and number density correlators. We calculate that multiplicity-momentum correlations should vanish in equilibrium in the Grand Canonical Ensemble, therefore non-zero measured values may indicate that the system has not reached local thermal equilibrium. Information about the level of equilibration of the system is important because many state-of-the-art models assume local equilibration either directly or through the use of an equation of state that makes this assumption. We make estimates of multiplicity-momentum correlations using PYTHIA/Angantyr and find positive values comparable in magnitude to well-measured correlations of transverse momentum fluctuations. We then outline a formalism that can use multiplicity-momentum correlations and correlations of transverse momentum fluctuations to quantify the level of partial thermalization of the system. |
Sunday, October 30, 2022 11:42AM - 11:54AM |
PF.00007: Baryon Number Transport, Strangeness Conservation and $\Omega$-hadron Correlations Xiatong Wu, Weijie Dong, Xiaozhou Yu, Hui Li, Gang Wang, Huan Z Huang We will present model studies of dynamics of baryon number transport, strangeness conservation and their manifestation in $\Omega$-hadron correlations. Although strange quarks are produced in $s\bar{s}$ pairs, the ratio of $\Omega^{-}$ to ${\bar{\Omega}}^{+}$ is greater than one in heavy-ion collisions at RHIC. Thus the produced $\Omega$ hyperons must carry net baryon quantum numbers from the colliding nuclei. We will present results of $\Omega^{-}-K^{\pm}$, ${\bar{\Omega}}^{+}-K^{\pm}$, $\Omega^{-}-\bar{\Xi}$ and $\bar{\Omega}^{+}-\Xi$ correlations from model simulations of Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV and 14.6 GeV. These correlations can probe dynamics for baryon number transport to mid-rapidities at these two beam energies. In addition, we use AMPT (default and string-melting modes) and UrQMD models to illustrate how hadronization schemes of quark coalescence and string fragmentations could leave imprints on such correlations. Implications on the experimental program to measure these correlations with the STAR experiment at RHIC will also be discussed. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700