重离子碰撞中的轻核产生和QCD相变  

Light nuclei production and QCD phase transition in heavy-ion collisions

作　　者：孙开佳 陈列文 Ko Che Ming 李峰[5] 徐骏[6] 许长补 SUN Kaijia;CHEN Liewen;Ko Che Ming;LI Feng;XU Jun;XU Zhangbu(Key Laboratory of Nuclear Physics and Ion-beam Application(MOE),Institute of Modern Physics,Fudan University,Shanghai 200433,China;Shanghai Research Center for Theoretical Nuclear Physics,NSFC and Fudan University,Shanghai 200438,China;School of Physics and Astronomy,Shanghai Key Laboratory for Particle Physics and Cosmology,Key Laboratory for Particle Physics,Astrophysics and Cosmology(MOE),Shanghai Jiao Tong University,Shanghai 200240,China;Cyclotron Institute and Department of Physics and Astronomy,Texas A&M University,College Station,TA77843,USA;School of Physical Science and Technology,Lanzhou University,Lanzhou 730000,China;School of Physics Science and Engineering,Tongji University,Shanghai 200092,China;Physics Department,Brookhaven National Laboratory,Upton,NY11973,USA)

机构地区：[1]复旦大学现代物理研究所核物理与离子束应用教育部重点实验室,上海200433 [2]理论物理专款上海核物理理论研究中心,上海200438 [3]上海交通大学物理与天文学院上海市粒子物理和宇宙学重点实验室粒子物理与星系宇宙学教育部重点实验室,上海200240 [4]Cyclotron Institute and Department of Physics and Astronomy,Texas A&M University,College Station,TA77843,USA [5]兰州大学物理科学与技术学院,兰州730000 [6]同济大学物理科学与工程学院,上海200092 [7]Physics Department,Brookhaven National Laboratory,Upton,NY11973,USA

出　　处：《核技术》2023年第4期159-175,共17页Nuclear Techniques

基　　金：国家重点研发计划(No.2022YFA1602303,No.2022YFA1604900);国家自然科学基金(No.12235010,No.11625521,No.11922514,No.12147101);科技部SKA专项(No.2020SKA0120300)资助

摘　　要：寻找量子色动力学(Quantum Chromodynamics,QCD)相变信号是当前重离子碰撞实验的一个基础科学目标,对理解强相互作用物质的性质、大爆炸初期的宇宙演化、超新星的爆发机制、致密星的内部结构以及双中子星并合产生的引力波等重要前沿问题都具有重要意义。当重离子碰撞中发生非连续QCD相变时,引发的强相互作用物质的密度涨落与关联可以通过轻原子核的产额观察量来探测。核子间的多体关联决定了重离子碰撞中轻核的产额。特别地,基于核子并合模型对于轻核产额的计算表明质子(p)、氘核(d)和氚核(t)的产额比值N_(t)N_(p)/Nd_(2)敏感于核子密度涨落与关联,是一个较好的寻找QCD相变信号的可观测量。进一步,基于输运模型对于重离子碰撞中的手征相变的模拟发现,当系统的相轨迹经过一阶相变区域时,轻核产额比值N_(t)N_(p)/Nd_(2)有明显增加。这些结果为利用重离子碰撞中的轻核产生寻找QCD相变提供了理论依据。The searching for potential quantum chromodynamics(QCD)phase transition signals is a fundamental goal of on-going experiments on heavy-ion collisions,which is critical to understanding the properties of strongly interacting matter under extreme conditions,the inner structure of compact stars,gravitational waves emitted from neutron star mergers,etc.In particular,the beam energy scan program carried out at the Relativistic Heavy-Ion Collider(RHIC)provides a unique tool that enables studies into the QCD phase diagram and the conjectured QCD critical point.Besides the event-by-event fluctuation of conserved charges,which has been widely accepted as a useful study of the QCD critical point,the production of light nuclei can serve as a sensitive observable to the QCD phase transitions in high-energy heavy-ion collisions.The density fluctuation and correlation among nucleons are automatically encoded in the production of light nuclei in heavy-ion collisions.This study aims to demonstrate how to probe QCD phase transition with light nuclei production in heavy-ion collisions.The progress of studies in this area over the last few years is reviewed.The nucleon coalescence model provides a suitable tool for the study of the effects of density fluctuation/correlation on light nuclei production.A transport model based on the Nambu-Jona-Lasinio(NJL)model is developed to simulate the occurrence of the first-order chiral phase transition in heavy-ion collisions.Within the coalescence model for light nuclei production,the yield ratio N_(t)N_(p)/N 2 d of protons(p),deuterons(d),and tritons(t)is shown to be sensitive to the nucleon density fluctuation and correlation and can function as a good probe to the non-smooth QCD phase transition.The production of light nuclei in heavy-ion collisions encodes the information about baryon density fluctuations and correlations,and enhancements of the yield ratio N_(t)N_(p)/N 2 d could serve as an indicator for the occurrence of a first-order or second-order QCD phase transition.

关 键 词：重离子碰撞 QCD相变 轻核产生 并合模型 临界涨落 

分 类 号：O571.6[理学—粒子物理与原子核物理]