Centrality Dependence of Elliptic Flow of Multi-strange Hadrons in Au+Au Collisions at √sNN PDF Download

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Languages : en
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Here, elliptic flow (v2) values for identified particles at midrapidity in Au + Au collisions measured by the STAR experiment in the Beam Energy Scan at the Relativistic Heavy Ion Collider at √sNN = 7.7-62.4 GeV are presented for three centrality classes. The centrality dependence and the data at √sNN = 14.5 GeV are new. Except at the lowest beam energies, we observe a similar relative v2 baryon-meson splitting for all centrality classes which is in agreement within 15% with the number-of-constituent quark scaling. The larger v2 for most particles relative to antiparticles, already observed for minimum bias collisions, shows a clear centrality dependence, with the largest difference for the most central collisions. Also, the results are compared with a multiphase transport (AMPT) model and fit with a blast wave model.

Author: Satyajit Jena
Publisher: Springer Nature
ISBN: 9819702895
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Languages : en
Pages : 1353

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Using the RQMD model, transverse momentum dependence of the anisotropic flow v2 for [pi], K, nucleon, [phi], and [lambda], are studied for Au + Au collisions at √s{sub NN} = 200 GeV. Both hydrodynamic hadron-mass hiragracy (hhmh) at low p{sub T} region and particle type dependence (baryon versus meson) at the intermediate p{sub T} region are reproduced with the model calculations although the model underpredicted the overall values of v2 by a factor of 2-3. As expected, when the rescatterings are turned off, all v2 becomes zero. The failure of the hadronic model in predicting the absolute values of hadron v2 clearly demonstrate the need of early dense partonic interaction in heavy-ion collisions at RHIC. At the intermediate p{sub T}, the hadron type dependence cold also be explained by the vacume hadronic cross sections within the frame of the model. The measurements of collective motion of hadrons from high-energy nuclear collisions can provide information on the dynamical equation of state information of the system [1, 2, 3]. Specifically, the strange and multi-strange hadron flow results have demonstrated the partonic collectivity [5] and the heavy-flavor flow will test the hypothesis of early thermalization in such collisions [4]. At RHIC, the measurements [6, 7] of elliptic flow v2 and nuclear modification factor r{sub AA} has lead to the conclusion that hadrons were formed via the coalescence/recombination of massive quarks [8, 9, 10]. This finding is directly related to the key issue in high-energy nuclear collisions such as deconfinement and chiral symmetry restoration. In addition, it also touched the important problem of hadronization process in high-energy collisions. Therefore a systematic study with different approaches becomes necessary. In this report, using a hadronic transport model UrQMD(v2.2)/RQMD(v2.4) [11, 12], we study the v2 of [pi], K, p, [phi], and [Lambda] from Au + Au collisions at 200 GeV. Properties of centrality dependent and freeze-out time dependent will be discussed. We try to answer some specific questions like how much the observed features can be reproduced by the hadronic model and why. In this approach, the vacumme cross sections are used for strong interactions. Unlike the treatment in most hydrodynamic calculations, the transition from strong interaction and free-steaming is determined by the local density and gradual. As we will discuss in the paper, the shortcoming of this method is lack of the partonic interactions which is important for the early dynamics in ultra-relativistic heavy ion collisions [13]. In order to take care of both partonic and hadronic interactions in high-energy nuclear collisions, a combination of hydrodynamic model for early stage (the perfect fluid stage) and hadronic transport model for later stage and freeze-out has been tried [14, 15].

Author: Brennan C. Schaefer
Publisher:
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Category : Electronic dissertations
Languages : en
Pages : 87

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Author: Aihong Tang
Publisher:
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Category : Collisions (Nuclear physics)
Languages : en
Pages : 226

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Author: Xiaofeng Luo
Publisher: Springer Nature
ISBN: 9811944415
Category : Science
Languages : en
Pages : 294

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This book highlights the discussions by renown researchers on questions emerged during transition from the relativistic heavy-ion collider (RHIC) to the future electron ion collider (EIC). Over the past two decades, the RHIC has provided a vast amount of data over a wide range of the center of mass energies. What are the scientific priorities, after RHIC is shut down and turned to the future EIC? What should be the future focuses of the high-energy nuclear collisions? What are thermodynamic properties of quantum chromodynamics (QCD) at large baryon density? Where is the phase boundary between quark-gluon-plasma and hadronic matter at high baryon density? How does one make connections from thermodynamics learned in high-energy nuclear collisions to astrophysical topics, to name few, the inner structure of compact stars, and perhaps more interestingly, the dynamical processes of the merging of neutron stars? While most particle physicists are interested in Dark Matter, we should focus on the issues of Visible Matter! Multiple heavy-ion accelerator complexes are under construction: NICA at JINR (4 ~ 11 GeV), FAIR at GSI (2 ~ 4.9 GeV SIS100), HIAF at IMP (2 ~ 4 GeV). In addition, the heavy-ion collision has been actively discussed at the J-PARC. The book is a collective work of top researchers from the field where some of the above-mentioned basic questions will be addressed. We believe that answering those questions will certainly advance our understanding of the phase transition in early universe as well as its evolution that leads to today's world of nature.

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Languages : en
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The pseudorapidity asymmetry and centrality dependence of charged hadron spectra in d+Au collisions at (square root)s{sub NN} = 200 GeV are presented. The charged particle density at mid-rapidity, its pseudorapidity asymmetry and centrality dependence are reasonably reproduced by a Multi-Phase Transport model, by HIJING, and by the latest calculations in a saturation model. Ratios of transverse momentum spectra between backward and forward pseudorapidity are above unity for p{sub T} below 5 GeV/c. The ratio of central to peripheral spectra in d+Au collisions shows enhancement at 2

Author: Yue Liang
Publisher:
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Category :
Languages : en
Pages : 0

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Heavy ion collisions at Relativistic Heavy Ion Collider (RHIC) provide a unique environment to probe nuclear matter under extremely high temperature and density conditions. Among the many insights that can be provided are studying the Quark Gluon Plasma (QGP) created in these collisions, the interaction of color-charged probes with the QGP, the mechanism of hadronization as well as the nature of phase transition to the deconfined phase. Production of heavy quarks in high-energy nuclear collisions occurs mainly through initial hard scattering, via gluon fusion and quark anti-quark annihilation, since the thermal production in the hot QCD medium is significantly suppressed due to the heavy quark masses. This makes heavy quarks ideal probes of the QGP as they experience the whole medium evolution. The diffusion of a heavy particle through a heat bath of the hot-QCD medium can be quantified by the spatial diffusion coefficient D[subscript]s, in analogy to the Brownian motion in molecular physics. Early calculations based on perturbative methods for the diffusion coefficient for the charm and bottom quarks in a QGP produced values of D[subscript]s(2[pi]T) ~ 30 ~ O(1/[alpha]2[subscript]s) for a strong coupling constant of [alpha][subscript]s ~ 0.3-0.4 and with a value varying only weakly with temperature. We now know that these values for D[subscript]s are too large to account for the open heavy-flavor (HF) observables, including the elliptic flow (v2) of D0 mesons, in heavy-ion collisions at RHIC and the LHC. New measurements, including of higher order flow, with better precision and studying their dependence on collision geometry and size and shape of the produced medium allow us to better constrain the value of D[subscript]s and the heavy quark interaction with the QGP. The Solenoidal Tracker At RHIC (STAR) experiment is one of the two remaining large detector systems at the RHIC. The Time Projection Chamber (TPC) is the main detector at STAR measuring 4.2 m in length and 4 m in diameter, it provides full azimuthal coverage out to ± 1.0 units of rapidity and particle identification down to transverse momenta of 100 MeV/c. The Heavy Flavor Tracker (HFT) silicon vertex upgrade for the STAR experiment, is utilizing active pixel sensors and silicon strip technology and provides excellent track pointing resolution to allow the reconstruction of heavy flavor hadron decays. My thesis work is utilizing the STAR Heavy Flavor Tracker's combined datasets recorded during RHIC 2014 and 2016 runs to measure with improved precision the D0-meson elliptical (v2) and triangular flow (v3) as a function of event centrality (quantity which describes the overlap region between the two colliding nuclei) and D0 transverse momentum. I also present results obtained with a new method of event-shape-engineering (ESE) to study correlations of D0 v2 with the event geometry. The physics results are compared with model simulations. My results confirm that the D0 v2 follows the same number-of-constituent-quark (NCQ) scaling as light flavor hadrons. Non-zero v3 is observed, and by combining the 2014 and 2016 data, I also observe that the v3 also follows the NCQ scaling as light hadrons. Compared to theoretical model calculations, the observed large v2/v3 results demonstrate that charm quarks gain these strong collectivity through the diffusion in the strongly-coupled QGP medium. From the ESE study, I observe that the event-shape q2 dependence of the measured [pi][superscript]±, K[superscript]± and D0 hadrons follow the similar linear dependence with comparable slope in 10-40% Au+Au collisions. This demonstrated that the heavy flavor hadron v2 is driven by the event geometry. These results allow putting strict constraints on the values of the diffusion coefficient D[subscript]s. STAR's v2 results have been included in recent model analyses and provided a constraint on the 2[pi]TD[subscript]s to be around 2-5 near the T[subscript]c region while the temperature dependence from various models remains largely uncertain. The next phase of heavy flavor programs at RHIC and LHC need to focus on better constraining the temperature/momentum dependence on the heavy quark diffusion coefficient. Furthermore, since the bottom quark mass is much larger than that of charm, theoretically, bottom quark transport in QGP medium can be better described by the Langevin simulation. Testing the universality of heavy quark spatial diffusion coefficient between charm and bottom quarks will be also the next focus in RHIC and LHC HF programs.