In this study,the chemical freeze-out of hadrons,including light-and strange-flavor particles and light nuclei,produced in Au+Au collisions at the Relativistic Heavy Ion Collider(RHIC),was investigated.Using the Therm...In this study,the chemical freeze-out of hadrons,including light-and strange-flavor particles and light nuclei,produced in Au+Au collisions at the Relativistic Heavy Ion Collider(RHIC),was investigated.Using the Thermal-FIST thermodynamic statistical model,we analyzed various particle sets:those inclusive of light nuclei,those exclusive to light nuclei,and those solely comprising light nuclei.We determined the chemical freeze-out parameters at√^(S)NN=7.7–200 Ge V and four different centralities.A significant finding was the decrease in the chemical freeze-out temperature T_(ch)with light-nuclei inclusion,with an even more pronounced reduction when considering light-nuclei yields exclusively.This suggests that light-nuclei formation occurs at a later stage in the system’s evolution at RHIC energies.We present parameterized formulas that describe the energy dependence of T_(ch)and the baryon chemical potentialμ_(B) for three distinct particle sets in central Au+Au collisions at RHIC energies.Our results reveal at least three distinct T_(ch)at RHIC energies correspond to different freeze-out hypersurfaces:a light-flavor freeze-out temperature of T_L=150.2±6 Me V,a strange-flavor freeze-out temperature T_s=165.1±2.7 Me V,and a light-nuclei freeze-out temperature T_(ln)=141.7±1.4 Me V.Notably,at the Large Hadron Collider(LHC)Pb+Pb 2.76Te V,the expected lower freeze-out temperature for light nuclei was not observed;instead,the T_(ch)for light nuclei was found to be approximately 10 Me V higher than that for light-flavor hadrons.展开更多
Fluctuations of conserved quantities, such as baryon, electric charge, and strangeness number, are sensitive observables in relativistic heavy-ion collisions to probe the QCD phase transition and search for the QCD cr...Fluctuations of conserved quantities, such as baryon, electric charge, and strangeness number, are sensitive observables in relativistic heavy-ion collisions to probe the QCD phase transition and search for the QCD critical point. In this paper, we review the experimental measurements of the cumulants(up to fourth order) of event-byevent net-proton(proxy for net-baryon), net-charge and netkaon(proxy for net-strangeness) multiplicity distributions Au+Au collisions at sNN^(1/2) 7:7; 11:5; 14:5; 19:6; 27;39; 62:4; 200 Ge V from the first phase of beam energy scan program at the relativistic heavy-ion collider(RHIC). We also summarize the data analysis methods of suppressing the volume fluctuations, auto-correlations, and the unified description of efficiency correction and error estimation.Based on theoretical and model calculations, we will discuss the characteristic signatures of critical point as well as backgrounds for the fluctuation observables in heavy-ion collisions. The physics implications and the future secondphase of the beam energy scan(2019–2020) at RHIC will also be discussed.展开更多
In the context of unified hydrodynamics, we discuss the pseudorapidity distributions of the charged particles produced in Au-Au and Cu-Cu collisions at the low RHIC energies of √SNN = 19.6 and 22.4 GeV, respectively....In the context of unified hydrodynamics, we discuss the pseudorapidity distributions of the charged particles produced in Au-Au and Cu-Cu collisions at the low RHIC energies of √SNN = 19.6 and 22.4 GeV, respectively. It is found that the unified hydrodynamics alone can give a good description to the experimental measurements. This is different from the collisions at the maximum RHIC energy of √SNN = 200 GeV or at LHC energy of √SNN= 2.76 TeV, in which the leading particles must be taken into account so that we can properly explain the experimental observations.展开更多
We compare the jet-path length and beam-energy dependence of the pion nuclear modification factor and a patton-jet nuclear modification factor at RHIC and LHC, and contrast the predictions based on a linear pQCD and a...We compare the jet-path length and beam-energy dependence of the pion nuclear modification factor and a patton-jet nuclear modification factor at RHIC and LHC, and contrast the predictions based on a linear pQCD and a highly non-linear hybrid AdS holographic model of jet-energy loss. It is found that both models require a reduction of the jet-medium coupling from RHIC to LHC to account for the measured pion nuclear modification factor. In the case of the parton-jet nuclear modification factor, however, which serves as a lower bound for the LO jet nuclear modification factor of reconstructed jets, the extracted data can be characterized without a reduced jet-medium coupling at LHC energies. It is concluded that when the reconstructed jets are sensitive to both quarks and gluons and thus provide more information than the pion nuclear modification factor, their information regarding the jet-medium coupling is limited due to the superposition with NLO and medium effects. Hence, a detailed description of the underlying physics requires both the leading hadron and the reconstructed jet nuclear modification factor. Unfortunately, the results for both the pion and the parton-jet nuclear modification factor are insensitive to the jet-path dependence of the models considered.展开更多
用双源统计模型分别研究了158 A Gev Pb+Pb和(?)s=130 A GeV Au+Au反应中的多粒子产生并与单源统计模型的结果进行了比较.研究表明,前一个反应由内外两个源组成,内源小而热,外源大而较凉;后一个反应有一个高温且大体积的内源.这个源的...用双源统计模型分别研究了158 A Gev Pb+Pb和(?)s=130 A GeV Au+Au反应中的多粒子产生并与单源统计模型的结果进行了比较.研究表明,前一个反应由内外两个源组成,内源小而热,外源大而较凉;后一个反应有一个高温且大体积的内源.这个源的温度比SPS能量的内源至少高15MeV,体积至少大2倍.文中给出了分析.展开更多
Following over 20 years of research,a direct measurement of the QGP temperature has been achieved at Relativistic Heavy-Ion Collider(RHIC),free from the blue-shift effect and contamination from strong interactions.Thi...Following over 20 years of research,a direct measurement of the QGP temperature has been achieved at Relativistic Heavy-Ion Collider(RHIC),free from the blue-shift effect and contamination from strong interactions.This viewpoint discusses a recent measurement of the QGP temperature at different stages at the Solenoidal Tracker at RHIC(STAR),which used e^(+)e^(-)pairs as penetrating probes.展开更多
Both the PHENIX and STAR experiments at the Relativistic Heavy Ion Collider （RHIC） at Brookhaven National Laboratory are running polarized proton-proton collisions at √s = 200 and 500 GeV. The main goal of the RHIC...Both the PHENIX and STAR experiments at the Relativistic Heavy Ion Collider （RHIC） at Brookhaven National Laboratory are running polarized proton-proton collisions at √s = 200 and 500 GeV. The main goal of the RHIC spin physics program is to gain deeper insight into the spin structure of the nucleon. We will give an overview of recent spin results from RHIC, particularly the study of gluon polarization via jet/hadron production and sea quark polarization via W boson production in longitudinally polarized proton-proton collisions.展开更多
基金supported by the Scientific Research Foundation of Hubei University of Education for Talent Introduction(Nos.ESRC20230002 and ESRC20230007)the Research Project of Hubei Provincial Department of Education(Nos.D20233003 and B2023191)。
文摘In this study,the chemical freeze-out of hadrons,including light-and strange-flavor particles and light nuclei,produced in Au+Au collisions at the Relativistic Heavy Ion Collider(RHIC),was investigated.Using the Thermal-FIST thermodynamic statistical model,we analyzed various particle sets:those inclusive of light nuclei,those exclusive to light nuclei,and those solely comprising light nuclei.We determined the chemical freeze-out parameters at√^(S)NN=7.7–200 Ge V and four different centralities.A significant finding was the decrease in the chemical freeze-out temperature T_(ch)with light-nuclei inclusion,with an even more pronounced reduction when considering light-nuclei yields exclusively.This suggests that light-nuclei formation occurs at a later stage in the system’s evolution at RHIC energies.We present parameterized formulas that describe the energy dependence of T_(ch)and the baryon chemical potentialμ_(B) for three distinct particle sets in central Au+Au collisions at RHIC energies.Our results reveal at least three distinct T_(ch)at RHIC energies correspond to different freeze-out hypersurfaces:a light-flavor freeze-out temperature of T_L=150.2±6 Me V,a strange-flavor freeze-out temperature T_s=165.1±2.7 Me V,and a light-nuclei freeze-out temperature T_(ln)=141.7±1.4 Me V.Notably,at the Large Hadron Collider(LHC)Pb+Pb 2.76Te V,the expected lower freeze-out temperature for light nuclei was not observed;instead,the T_(ch)for light nuclei was found to be approximately 10 Me V higher than that for light-flavor hadrons.
基金supported in part by the Mo ST of China 973-Project(No.2015CB856901)the National Natural Science Foundation of China(No.11575069)
文摘Fluctuations of conserved quantities, such as baryon, electric charge, and strangeness number, are sensitive observables in relativistic heavy-ion collisions to probe the QCD phase transition and search for the QCD critical point. In this paper, we review the experimental measurements of the cumulants(up to fourth order) of event-byevent net-proton(proxy for net-baryon), net-charge and netkaon(proxy for net-strangeness) multiplicity distributions Au+Au collisions at sNN^(1/2) 7:7; 11:5; 14:5; 19:6; 27;39; 62:4; 200 Ge V from the first phase of beam energy scan program at the relativistic heavy-ion collider(RHIC). We also summarize the data analysis methods of suppressing the volume fluctuations, auto-correlations, and the unified description of efficiency correction and error estimation.Based on theoretical and model calculations, we will discuss the characteristic signatures of critical point as well as backgrounds for the fluctuation observables in heavy-ion collisions. The physics implications and the future secondphase of the beam energy scan(2019–2020) at RHIC will also be discussed.
基金Supported by the Shanghai Key Lab of Modern Optical System
文摘In the context of unified hydrodynamics, we discuss the pseudorapidity distributions of the charged particles produced in Au-Au and Cu-Cu collisions at the low RHIC energies of √SNN = 19.6 and 22.4 GeV, respectively. It is found that the unified hydrodynamics alone can give a good description to the experimental measurements. This is different from the collisions at the maximum RHIC energy of √SNN = 200 GeV or at LHC energy of √SNN= 2.76 TeV, in which the leading particles must be taken into account so that we can properly explain the experimental observations.
基金Supported by the Helmholtz International Centre for FAIR within the Framework of the LOEWE Programthe US-DOE Nuclear Science under Grant Nos DE-FG02-93ER40764 and DE-AC02-05CH11231
文摘We compare the jet-path length and beam-energy dependence of the pion nuclear modification factor and a patton-jet nuclear modification factor at RHIC and LHC, and contrast the predictions based on a linear pQCD and a highly non-linear hybrid AdS holographic model of jet-energy loss. It is found that both models require a reduction of the jet-medium coupling from RHIC to LHC to account for the measured pion nuclear modification factor. In the case of the parton-jet nuclear modification factor, however, which serves as a lower bound for the LO jet nuclear modification factor of reconstructed jets, the extracted data can be characterized without a reduced jet-medium coupling at LHC energies. It is concluded that when the reconstructed jets are sensitive to both quarks and gluons and thus provide more information than the pion nuclear modification factor, their information regarding the jet-medium coupling is limited due to the superposition with NLO and medium effects. Hence, a detailed description of the underlying physics requires both the leading hadron and the reconstructed jet nuclear modification factor. Unfortunately, the results for both the pion and the parton-jet nuclear modification factor are insensitive to the jet-path dependence of the models considered.
文摘用双源统计模型分别研究了158 A Gev Pb+Pb和(?)s=130 A GeV Au+Au反应中的多粒子产生并与单源统计模型的结果进行了比较.研究表明,前一个反应由内外两个源组成,内源小而热,外源大而较凉;后一个反应有一个高温且大体积的内源.这个源的温度比SPS能量的内源至少高15MeV,体积至少大2倍.文中给出了分析.
文摘Following over 20 years of research,a direct measurement of the QGP temperature has been achieved at Relativistic Heavy-Ion Collider(RHIC),free from the blue-shift effect and contamination from strong interactions.This viewpoint discusses a recent measurement of the QGP temperature at different stages at the Solenoidal Tracker at RHIC(STAR),which used e^(+)e^(-)pairs as penetrating probes.
基金Acknowledgements The work was supported by the National Natural Science Foundation of China, China, under Grant Nos. 11175106 and 11222551, and the Natural Science Foundation of Shandong Province, China, under Grant No. ZR2013JQ001.
文摘Both the PHENIX and STAR experiments at the Relativistic Heavy Ion Collider （RHIC） at Brookhaven National Laboratory are running polarized proton-proton collisions at √s = 200 and 500 GeV. The main goal of the RHIC spin physics program is to gain deeper insight into the spin structure of the nucleon. We will give an overview of recent spin results from RHIC, particularly the study of gluon polarization via jet/hadron production and sea quark polarization via W boson production in longitudinally polarized proton-proton collisions.
