摘要：
The zero-degree calorimeter (ZDC) plays a crucial role toward determining the centrality in the Cooling-Storage-Ring External-target Experiment (CEE) at the Heavy Ion Research Facility in Lanzhou. A boosted decision tree (BDT) multi-classification algorithm was employed to classify the centrality of the collision events based on the raw features from ZDC such as the number of fired channels and deposited energy. The data from simulated
$$^{238}\textrm{U}$$
+
$$^{238}\textrm{U}$$
collisions at 500
$$\mathrm{MeV/u}$$
, generated by the IQMD event generator and subsequently modeled using the GEANT4 package, were employed to train and test the BDT model. The results showed the high accuracy of the multi-classification model adopted in ZDC for centrality determination, which is robust against variations in different factors of detector geometry and response. This study demonstrates the good performance of CEE-ZDC in determining the centrality in nucleus–nucleus collisions.
作者机构：
[Huang, Huan Zhong] Univ Calif Los Angeles, Dept Phys & Astrophys, Los Angeles, CA 90095 USA.;[Shi, Shusu; Luo, Xiaofeng; Liu, Feng] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.;[Shi, Shusu; Luo, Xiaofeng; Liu, Feng] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.;[Wang, Fuqiang] Purdue Univ, Dept Phys, W Lafayette, IN 47907 USA.;[Xu, Nu] Lawrence Berkeley Natl Lab, Nucl Sci Div, Berkeley, CA 94720 USA.
通讯机构：
[Shusu Shi] K;Key Laboratory of Quark & Lepton Physics (MOE) and Institute of Particle Physics, Central China Normal University, Wuhan 430079, China<&wdkj&>Author to whom correspondence should be addressed.
关键词：
high-energy nuclear collisions;collectivity;chirality;criticality;QCD;critical point;phase boundary;strangeness;thermalization;viscosity;baryon density
摘要：
<jats:p>We celebrate the legacies of our friend and mentor Professor Lianshou Liu who was one of the pioneers for the phenomenology of multi-particle interactions and initiated the physics of relativistic heavy-ion collisions in China. In this article, we discuss some of the recent exciting experimental observations on the collective phenomena including collectivity, chirality, criticality, strangeness production, and thermal equilibrium in high-energy nuclear collisions. Future directions, especially the physics at high baryon density, will be discussed with a focus on the first-order phase boundary and hyperon–nucleon interactions.</jats:p>
作者机构：
[Zhang, Biao; Wang, Ya-Ping; Pei, Hua; Xu, Nu; Shi, Shu-Su; Liu, Li-Ke] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.;[Zhang, Biao; Wang, Ya-Ping; Pei, Hua; Xu, Nu; Shi, Shu-Su; Liu, Li-Ke] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.
通讯机构：
[Shi, SS ] C;Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.;Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.
摘要：
The Cooling Storage Ring external-target experiment (CEE) spectrometer is used to study the nuclear matter created in heavy-ion collisions at
$$\sqrt{s_{_{\mathrm{{NN}}}}}$$
= 2.1–2.4GeV with the aim to reveal the quantum chromodynamics phase structure in the high-baryon-density region. Collective flow is considered an effective probe for evaluating the properties of media during high-energy nuclear collisions. One of the main functions of the zero-degree calorimeter (ZDC), a subdetector system in the CEE, is to determine the reaction plane in heavy-ion collisions. This step is crucial for measuring the collective flow and other reaction-plane-related analyses. In this paper, we illustrate the procedures for event plane determination using the ZDC. Finally, isospin-dependent quantum molecular dynamics model-based predictions of the rapidity dependence of the directed and elliptical flows for p, d, t,
$$^3$$
He, and
$$^4$$
He, produced in 2.1 GeV U+U collisions, are presented.
作者：
Agakishiev, H.*;Aggarwal, M. M.;Ahammed, Z.;Alakhverdyants, A., V;Alekseev, I;...
期刊：
中国物理C,2021年45(4):198-241 ISSN：1674-1137
通讯作者：
Agakishiev, H.
作者机构：
[Kechechyan, A.; Agakishiev, H.; Averichev, G. S.; Efimov, L. G.; Alakhverdyants, A., V; Kizka, V; Rogachevskiy, O., V; Panebratsev, Y.; Shahaliev, E.; Fedorisin, J.; Bunzarov, I; Zoulkarneev, R.; Zoulkarneeva, Y.; Tokarev, M.; Filip, P.; Lednicky, R.; Dedovich, T. G.; Vokal, S.] Joint Inst Nucl Res, Dubna 141980, Russia.;[Underwood, D. G.; Krueger, K.; Bridgeman, A.; Spinka, H. M.] Argonne Natl Lab, Argonne, IL 60439 USA.;[Ullrich, T.; Pile, P.; Lamont, M. A. C.; Ljubicic, T.; Le Vine, M. J.; Xu, Z.; Ogawa, A.; Ruan, L.; Tang, A. H.; Videbaek, F.; Fisyak, Y.; Beavis, D. R.; Lauret, J.; Bland, L. C.; Longacre, R. S.; Webb, J. C.; Christie, W.; Arkhipkin, D.; Fine, V; Debbe, R. R.; Lebedev, A.; Burton, T. P.; Dunlop, J. C.; Gordon, A.; Landgraf, J. M.; Love, W. A.; Yip, K.; Didenko, L.; Guryn, W.; Van Buren, G.; Lee, J. H.] Brookhaven Natl Lab, Upton, NY 11973 USA.;[Perkins, C.; Crawford, H. J.; Engelage, J.; Judd, E. G.] Univ Calif Berkeley, Berkeley, CA 94720 USA.;[Sanchez, M. Calderon de la Barca; Draper, J. E.; Cebra, D.; Brovko, S. G.; Mall, O., I; Sangaline, E.; Reed, R.; Romero, J. L.; Salur, S.; Haag, B.; Liu, H.] Univ Calif Davis, Davis, CA 95616 USA.
通讯机构：
[Agakishiev, H.] J;Joint Inst Nucl Res, Dubna 141980, Russia.
关键词：
relativistic heavy ion collisions;dihadron correlations;jet-medium interactions;anisotropic flow background;event plane
摘要：
<jats:title>Abstract</jats:title>
<jats:p>Dihadron azimuthal correlations containing a high transverse momentum (
<jats:inline-formula>
<jats:tex-math><?CDATA $ p_{T} $?></jats:tex-math>
<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_45_4_044002_M2.jpg" xlink:type="simple" />
</jats:inline-formula>) trigger particle are sensitive to the properties of the nuclear medium created at RHIC through the strong interactions occurring between the traversing parton and the medium, i.e. jet-quenching. Previous measurements revealed a strong modification to dihadron azimuthal correlations in Au+Au collisions with respect to <jats:italic>p</jats:italic>+<jats:italic>p</jats:italic> and <jats:italic>d</jats:italic>+Au collisions. The modification increases with the collision centrality, suggesting a path-length or energy density dependence to the jet-quenching effect. This paper reports STAR measurements of dihadron azimuthal correlations in mid-central (20%-60%) Au+Au collisions at
<jats:inline-formula>
<jats:tex-math><?CDATA $ \sqrt{s_{\rm{NN}}} = 200 $?></jats:tex-math>
<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_45_4_044002_M3.jpg" xlink:type="simple" />
</jats:inline-formula> GeV as a function of the trigger particle's azimuthal angle relative to the event plane,
<jats:inline-formula>
<jats:tex-math><?CDATA $ \phi_{s} = | \phi_{t}- \psi_{{\rm{EP}}}| $?></jats:tex-math>
<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_45_4_044002_M4.jpg" xlink:type="simple" />
</jats:inline-formula>. The azimuthal correlation is studied as a function of both the trigger and associated particle
<jats:inline-formula>
<jats:tex-math><?CDATA $ p_{T} $?></jats:tex-math>
<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_45_4_044002_M5.jpg" xlink:type="simple" />
</jats:inline-formula>. The subtractions of the combinatorial background and anisotropic flow, assuming Zero Yield At Minimum (ZYAM), are described. The correlation results are first discussed with subtraction of the even harmonic (elliptic and quadrangular) flow backgrounds. The away-side correlation is strongly modified, and the modification varies with
<jats:inline-formula>
<jats:tex-math><?CDATA $ \phi_{s} $?></jats:tex-math>
<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_45_4_044002_M6.jpg" xlink:type="simple" />
</jats:inline-formula>, with a double-peak structure for out-of-plane trigger particles. The near-side ridge (long range pseudo-rapidity
<jats:inline-formula>
<jats:tex-math><?CDATA $ \Delta\eta $?></jats:tex-math>
<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_45_4_044002_M7.jpg" xlink:type="simple" />
</jats:inline-formula> correlation) appears to drop with increasing
<jats:inline-formula>
<jats:tex-math><?CDATA $ \phi_{s} $?></jats:tex-math>
<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_45_4_044002_M8.jpg" xlink:type="simple" />
</jats:inline-formula> while the jet-like component remains approximately constant. The correlation functions are further studied with the subtraction of odd harmonic triangular flow background arising from fluctuations. It is found that the triangular flow, while responsible for the majority of the amplitudes, is not sufficient to explain the
<jats:inline-formula>
<jats:tex-math><?CDATA $ \phi_{s} $?></jats:tex-math>
<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_45_4_044002_M9.jpg" xlink:type="simple" />
</jats:inline-formula>-dependence of the ridge or the away-side double-peak structure. The dropping ridge with
<jats:inline-formula>
<jats:tex-math><?CDATA $ \phi_{s} $?></jats:tex-math>
<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_45_4_044002_M10.jpg" xlink:type="simple" />
</jats:inline-formula> could be attributed to a
<jats:inline-formula>
<jats:tex-math><?CDATA $ \phi_{s} $?></jats:tex-math>
<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_45_4_044002_M11.jpg" xlink:type="simple" />
</jats:inline-formula>-dependent elliptic anisotropy; however, the physics mechanism of the ridge remains an open question. Even with a
<jats:inline-formula>
<jats:tex-math><?CDATA $ \phi_{s} $?></jats:tex-math>
<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_45_4_044002_M12.jpg" xlink:type="simple" />
</jats:inline-formula>-dependent elliptic flow, the away-side correlation structure is robust. These results, with extensive systematic studies of the dihadron correlations as a function of
<jats:inline-formula>
<jats:tex-math><?CDATA $ \phi_{s} $?></jats:tex-math>
<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_45_4_044002_M13.jpg" xlink:type="simple" />
</jats:inline-formula>, trigger and associated particle
<jats:inline-formula>
<jats:tex-math><?CDATA $ p_{T} $?></jats:tex-math>
<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_45_4_044002_M14.jpg" xlink:type="simple" />
</jats:inline-formula>, and the pseudo-rapidity range
<jats:inline-formula>
<jats:tex-math><?CDATA $ \Delta\eta $?></jats:tex-math>
<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_45_4_044002_M15.jpg" xlink:type="simple" />
</jats:inline-formula>, should provide stringent inputs to help understand the underlying physics mechanisms of jet-medium interactions in high energy nuclear collisions.
</jats:p>
通讯机构：
[Gupta, Sourendu] T;Tata Inst Fundamental Res, Dept Theoret Phys, Homi Bhabha Rd, Mumbai 400005, Maharashtra, India.
会议名称：
28th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions (Quark Matter)
会议时间：
NOV 04-09, 2019
会议地点：
Wuhan, PEOPLES R CHINA
会议主办单位：
[Gupta, Sourendu] Tata Inst Fundamental Res, Dept Theoret Phys, Homi Bhabha Rd, Mumbai 400005, Maharashtra, India.^[Mallick, Debasish;Mohanty, Bedangadas] HBNI, Natl Inst Sci Educ & Res, Sch Phys Sci, Jatni 752050, India.^[Mishra, Dipak K.] Bhabha Atom Res Ctr, Nucl Phys Div, Mumbai 400085, Maharashtra, India.^[Mohanty, Bedangadas] CERN, Expt Phys Dept, CH-1211 Geneva 23, Switzerland.^[Xu, Nu] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.^[Xu, Nu] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.^[Xu, Nu] Chinese Acad Sci, Inst Modern Phys, 509 Nanchang Rd, Lanzhou 730000, Gansu, Peoples R China.
关键词：
Quark-gluon Plasma;Fluctuations;Thermalization;QCD Critical Point
摘要：
Arguments for thermalization of the QCD matter created in high-energy nuclear collisions has dominantly come from the agreement of the measured yields of produced hadrons with those from statistical thermal models. Ideally for a thermalized system, in addition to mean, the higher orders of the moments of the multiplicity distribution of produced particles should also show agreement with thermal models. In this respect, simultaneously studying the moments of the event-by-event distributions of conserved quantities like net-baryon, net-strangeness and net-charge number is best suited. We present a systematic study of comparing the results from a thermal hadron resonance gas (HRG) model with data on higher moments of net-proton, net-kaon and net-charge distributions measured at RHIC beam energy scan program. The experimental acceptances in terms of rapidity and transverse momentum are used in the model calculations which also include resonance decay. For the first time, the HRG model results are found to explain the measurements up to third order of moment with a common temperature and baryonic chemical potential. These calculations have tested the thermal nature of produced net-particle distributions up to third order, thereby providing evidence for thermalization of the QCD matter formed in such high energy heavy-ion collisions.
通讯机构：
[Yuxiang Zhao] I;Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, China<&wdkj&>University of Chinese Academy of Sciences, Beijing, China
关键词：
electron ion collider;nucleon structure;nucleon mass;exotic hadronic states;quantum chromodynamics;3D-tomography;helicity;transverse momentum dependent parton distribution;generalized parton distribution;energy recovery linac;polarization;spin rotator
摘要：
<jats:title>Abstract</jats:title><jats:p>Lepton scattering is an established ideal tool for studying inner structure of small particles such as nucleons as well as nuclei. As a future high energy nuclear physics project, an Electron-ion collider in China (EicC) has been proposed. It will be constructed based on an upgraded heavy-ion accelerator, High Intensity heavy-ion Accelerator Facility (HIAF) which is currently under construction, together with a new electron ring. The proposed collider will provide highly polarized electrons (with a polarization of ∼80%) and protons (with a polarization of ∼70%) with variable center of mass energies from 15 to 20 GeV and the luminosity of (2–3) × 10<jats:sup>33</jats:sup> cm<jats:sup>−2</jats:sup> · s<jats:sup>−1</jats:sup>. Polarized deuterons and Helium-3, as well as unpolarized ion beams from Carbon to Uranium, will be also available at the EicC.</jats:p><jats:p>The main foci of the EicC will be precision measurements of the structure of the nucleon in the sea quark region, including 3D tomography of nucleon; the partonic structure of nuclei and the parton interaction with the nuclear environment; the exotic states, especially those with heavy flavor quark contents. In addition, issues fundamental to understanding the origin of mass could be addressed by measurements of heavy quarkonia near-threshold production at the EicC. In order to achieve the above-mentioned physics goals, a hermetical detector system will be constructed with cutting-edge technologies.</jats:p><jats:p>This document is the result of collective contributions and valuable inputs from experts across the globe. The EicC physics program complements the ongoing scientific programs at the Jefferson Laboratory and the future EIC project in the United States. The success of this project will also advance both nuclear and particle physics as well as accelerator and detector technology in China.</jats:p>
作者机构：
Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, China;College of Physical Science and Technology, Central China Normal University, Wuhan, China;Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, USA;[Kenji Fukushima] Department of Physics, The University of Tokyo, Tokyo, Japan;School of Physical Sciences, National Institute of Science Education and Research, HBNI, Jatni, India
通讯机构：
[Nu Xu] I;Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, China<&wdkj&>College of Physical Science and Technology, Central China Normal University, Wuhan, China<&wdkj&>Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, USA
摘要：
<jats:title>Abstract</jats:title><jats:p>We make a theoretical and experimental summary of the state-of-the-art status of hot and dense QCD matter studies on selected topics. We review the Beam Energy Scan program for the QCD phase diagram and present the current status of the search for the QCD critical point, particle production in high baryon density region, hypernuclei production, and global polarization effects in nucleus-nucleus collisions. The available experimental data in the strangeness sector suggests that a grand canonical approach in the thermal model at high collision energy makes a transition to the canonical ensemble behavior at low energy. We further discuss future prospects of nuclear collisions to probe properties of baryon-rich matter. Creation of a quark-gluon plasma at high temperature and low baryon density has been called the “Little-Bang” and, analogously, a femtometer-scale explosion of baryon-rich matter at lower collision energy could be called the “femto-nova”, which could possibly sustain substantial vorticity and a magnetic field for non-head-on collisions.</jats:p>
作者机构：
[Bzdak, Adam] AGH Univ Sci & Technol, Fac Phys & Appl Comp Sci, PL-30059 Krakow, Poland.;[Esumi, ShinIchi] Univ Tsukuba, Tomonaga Ctr Hist Universe, Tsukuba, Ibaraki 305, Japan.;[Koch, Volker; Xu, Nu] Lawrence Berkeley Natl Lab, Nucl Sci Div, Berkeley, CA 94720 USA.;[Liao, Jinfeng] Indiana Univ, Phys Dept, 2401 N Milo B Sampson Lane, Bloomington, IN 47408 USA.;[Liao, Jinfeng] Indiana Univ, CEEM, 2401 N Milo B Sampson Lane, Bloomington, IN 47408 USA.
通讯机构：
[Liao, Jinfeng] I;Indiana Univ, Phys Dept, 2401 N Milo B Sampson Lane, Bloomington, IN 47408 USA.;Indiana Univ, CEEM, 2401 N Milo B Sampson Lane, Bloomington, IN 47408 USA.
会议名称：
PRPLC
关键词：
Beam energy scan;Chiral magnetic effect;Critical point;Heavy ion collision;QCD phase diagram
摘要：
We review the present status of the search for a phase transition and critical point as well as anomalous transport phenomena in Quantum Chromodynamics (QCD), with an emphasis on the Beam Energy Scan program at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory. We present the conceptual framework and discuss the observables deemed most sensitive to a phase transition, QCD critical point, and anomalous transport, focusing on fluctuation and correlation measurements. Selected experimental results for these observables together with those characterizing the global properties of the systems created in heavy ion collisions are presented. We then discuss what can be already learned from the currently available data about the QCD critical point and anomalous transport as well as what additional measurements and theoretical developments are needed in order to discover these phenomena. (c) 2020 Elsevier B.V. All rights reserved.
摘要：
轻子散射实验是探索核子与原子核结构的理想工具。中国电子离子对撞机(Electron Ion Collider in China,EicC)建议书设想在已开建的强流重离子加速器装置(High Intensity heavy ion Accelerator Facility,HIAF)的基础上,升级质子束流为20 GeV的极化束流,并建造2.8~5 GeV极化电子束流,从而实现质心系能量为15~ 20 GeV的双极化电子-离子对撞。EicC设计的亮度为(2~4)×10~(33) cm~(–2)·s~(–1),质子束流极化率达到70%,电子束流极化率达到80%。该装置除了能提供极化轻离子束流(例如:氦-3)外,也可产生非极化重离子束流(碳-12 ~铀- 238)。EicC将聚焦核子海夸克部分子结构、原子核物质结构与性质、奇特强子态三个方面的物理研究。高亮度、高精度的对撞机有助于精确地测量核子结构函数并对核子进行三维成像,揭示强相互作用的动力学规律;原子核部分子分布包括核子短程关联以及原子核介质效应同样是该提案的重要科学目标;EicC能区接近重味夸克产生阈值,在研究重味强子谱方面拥有低背景的独特优势,有助于发现研究新的奇特强子态。质子质量起源问题也可以通过重味矢量介子的产生来研究。为了完成上述物理目标,我们将利用最先进的探测器技术建造接近全立体角覆盖的EicC对撞机谱仪。在准备EicC白皮书的过程中,我们得到世界各国专家的支持。EicC的物理与已有的实验和美国即将建设的EIC中的物理项目相互补充。EicC的建成及运行有望引领前沿的中高能核物理研究,使我国在加速器和探测器先进技术等领域实现跨越式发展,为我国核物理与强子物理以及相关科学领域提供大型综合实验平台与人才培养基地。
摘要：
相对论重离子碰撞（又称高能核-核碰撞）为研究极端条件下核物质内禀性质、致密星体内部结构和大爆炸之后宇宙的早期演化过程提供了途径.强相互作用的量子色动力学（QCD）理论预言存在着解禁闭的新物质状态夸克-胶子等离子体（QGP）.经过近30年的努力,在极端相对论能区的核-核对撞实验中,包括RHIC和LHC的实验,科学家找到了QGP存在的证据.目前,高能核物理的一个重要的科学问题是高重子密度区的相结构,包括寻找相边界和可能存在的QCD临界点.量子热动力学基本原理告诉我们只有找到相边界或临界点才能最终确定新的物质相QGP的存在.我们首先回顾了高能核物理实验的研究现状,其中包括RHIC能量扫描实验中的强子集体运动、手征特性的研究和QCD临界点的寻找.然后对利用我国重离子加速器群,如Heavy Ion Research Facility in Lanzhou （HIRFL）和High Intensity heavy-ion Accelerator Facility （HIAF）以及CSR-External-target Experiment等开展高能核物理实验研究进行了展望.
作者机构：
[Shi, Shusu; Xu, Nu; Lin, Zi-Wei; Nayak, Kishora] Cent China Normal Univ, Key Lab Quark & Lepton Phys, MOE, Wuhan 430079, Hubei, Peoples R China.;[Shi, Shusu; Xu, Nu; Lin, Zi-Wei; Nayak, Kishora] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;[Xu, Nu] Chinese Acad Sci, Inst Modern Phys, Lanzhou, Gansu, Peoples R China.;[Lin, Zi-Wei] East Carolina Univ, Dept Phys, Greenville, NC 27858 USA.
通讯机构：
[Shi, Shusu] C;Cent China Normal Univ, Key Lab Quark & Lepton Phys, MOE, Wuhan 430079, Hubei, Peoples R China.;Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.
摘要：
The rapidity-odd component of directed flow ( v1) of identified hadrons ( π±, K±, KS0, p, p¯, ϕ, Ξ, Ξ¯, Λ, Λ¯) and partons ( u, u¯, d, d¯, s, s¯) in Au+Au collisions at various beam energies ( sNN=7.7, 11.5, 14.5, 19.6, 27, 39, 54.4, 62.4, 200 GeV) is analyzed using a multiphase transport model. A data driven approach (inspired from the experimental analysis) is performed here to distinguish the transported and produced quarks which are found to have different directed flow values at various collision beam energies. The coalescence sum rule (number of constituent quark scaling) violation is observed at lower energies where hadronic matters dominate. The strange quark ( s) and ϕ meson slope ( dv1/dy) show a double sign change around 14.5 GeV unlike other partons and hadrons. It suggests that the strange quark is more sensitive to the softening of the equation of state.
作者机构：
Faculty of International Liberal Arts, Akita International University, Yuwa, Akita 010-1292, Japan;Bhabha Atomic Research Centre, Bombay, 400 085, India;Vinca Institute of Nuclear Science, University of Belgrade, Belgrade, 11000, Serbia;Institute of Physics, University of Belgrade, Belgrade, 11000, Serbia;Collider and Accelerator Department, Brookhaven National Laboratory, Upton, NY 11973-5000, United States
作者机构：
[Luo, Xiaofeng; Xu, Nu] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;[Luo, Xiaofeng; Xu, Nu] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Hubei, Peoples R China.;[Luo, Xiaofeng] Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA.;[Xu, Nu] Lawrence Berkeley Natl Lab, Div Nucl Sci, Berkeley, CA 94720 USA.
通讯机构：
[Luo, Xiaofeng] C;[Luo, Xiaofeng] U;Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Hubei, Peoples R China.;Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA.
关键词：
QCD critical point;Fluctuations and correlations;Relativistic heavy-ion collisions;Conserved charges
摘要：
Open and hidden heavy-flavor physics in high-energy nuclear collisions are entering a new and exciting stage towards reaching a clearer understanding of the new experimental results with the possibility to link them directly to the advancement in lattice Quantum Chromo-Dynamics (QCD). Recent results from experiments and theoretical developments regarding open and hidden heavy-flavor dynamics have been debated at the Lorentz Workshop Tomography of the Quark-Gluon Plasma with Heavy Quarks, which was held in October 2016 in Leiden, The Netherlands. In this contribution, we summarize identified common understandings and developed strategies for the upcoming five years, which aim at achieving a profound knowledge of the dynamical properties of the quark-gluon plasma.
摘要：
Substantial experimental and theoretical efforts worldwide are devoted to explore the phase diagram of strongly interacting matter. At LHC and top RHIC energies, QCD matter is studied at very high temperatures and nearly vanishing net-baryon densities. There is evidence that a Quark-Gluon-Plasma (QGP) was created at experiments at RHIC and LHC. The transition from the QGP back to the hadron gas is found to be a smooth cross over. For larger net-baryon densities and lower temperatures, it is expected that the QCD phase diagram exhibits a rich structure, such as a first-order phase transition between hadronic and partonic matter which terminates in a critical point, or exotic phases like quarkyonic matter. The discovery of these landmarks would be a breakthrough in our understanding of the strong interaction and is therefore in the focus of various high-energy heavy-ion research programs. The Compressed Baryonic Matter (CBM) experiment at FAIR will play a unique role in the exploration of the QCD phase diagram in the region of high net-baryon densities, because it is designed to run at unprecedented interaction rates. High-rate operation is the key prerequisite for high-precision measurements of multi-differential observables and of rare diagnostic probes which are sensitive to the dense phase of the nuclear fireball. The goal of the CBM experiment at SIS100 (
$\sqrt{s_{NN}}=$
2.7--4.9 GeV) is to discover fundamental properties of QCD matter: the phase structure at large baryon-chemical potentials (
$\mu_B > 500$
MeV), effects of chiral symmetry, and the equation of state at high density as it is expected to occur in the core of neutron stars. In this article, we review the motivation for and the physics programme of CBM, including activities before the start of data taking in 2024, in the context of the worldwide efforts to explore high-density QCD matter.
摘要：
One of the main purposes of heavy-ion collisions over a wide range of beam energy is to study the bulk properties of strong interaction matter and understand the Quantum Chromo Dynamics (QCD) phase diagram, which carries wealth of information of the phase transition and the possibly existing critical point of the strongly interacting system [1]. Such system exists as hadron gases at lower temperature and low baryon density. By increasing the temperature or density, the boundary of the hadrons disappears and the confined quarks move freely in the whole system. Figure 1 shows the sketched QCD phase-diagram [2]. The red-thick line is the empirical chemical freeze-out curve. Nucleon mass is indicated by the filled dot at T = 0 MeV. The black-thick line is the speculated first-order phase boundary between quark-gluon plasma (QGP) and hadronic phase, while the open square point is the endpoint of the first-order phase boundary [3]. Since at μ_B = 0 the transition from QGP to hadronic phase is a smooth cross-over [4], at larger baryonic-chemical potential, thermodynamically there must be a critical point which ends the first-order phase transition line. Utilizing different beam energy, one can reach different regions on the phase diagram. The coverage of RHIC beam energy scan (BES) program and FAIR (SIS100-300) are shown as thin-lines in the figure [5]. The corresponding μ_B range of the CSR program is also indicated in the figure. While BES program of RHIC-STAR is dedicated to approach the critical point [5] from the high energy side, it is then of highly scientific importance to approach the CP from the low energy up and covers the studies of the phase diagram in the hadron phase.
