相对论重离子碰撞中的软探针和硬探针

简要回顾了高能核碰撞中夸克胶子等离子体的软探针和硬探针的一些最新进展,主要内容集中在相对论重离子对撞机和大型强子对撞机实验中各向异性集体流和喷注淬火的理论和唯象研究,对小系统中集体流的来源也做了简要的讨论。对于软探针,讨论了初态三维涨落和碰撞几何各向异性、相对论流体力学演化、末态各向异性集体流以及集体流的涨落、关联和纵向去关联等。通过与实验数据作系统的比较,可以探测重离子碰撞中夸克胶子等离子体的动力演化和各种输运性质。对于硬探针,集中讨论了部分子能量损失和喷注淬火对部分子味道的依赖性、重味夸克在夸克胶子等离子体中的强子化、整体喷注在核介质中的演化以及核介质对喷注的响应等。细致分析相关的观测量,可以帮助我们更全面地了解相对论核碰撞中喷注与核介质的相互作用以及重味粒子的生成。对于小系统,讨论初态和末态效应在解释小系统中轻强子和重味强子的集体流方面的贡献,这有助于我们理解大碰撞系统中集体流的起源成因。     

Spatial anisotropy: a method to study anisotropic flow in heavy ion collisions

We introduce a method to study anisotropic flow parameter v<,n> as a collective probe to Quark Gluon Plasma in relativistic heavy ion collisions. The emphasis is put on the use of the Fourier expansion of initial spatial azimuthal distributions of participant nucleons in the overlapped region. The coefficients ε<,n> of Fourier expansion are called the spatial anisotropy parameter for the n-th harmonic. We propose that collective dynamics can be studied by v<,n>/ε<,n>. In this paper, we will discuss in particular the second (n=2) and the fourth (n=4) harmonics.     

Multifragmentation and dynamics in heavy ion collisions

A midrapidity zone formed in heavy-ion collisions has been investigated through special selections of light particles and intermediate mass fragments detected in the reaction ³⁵Cl on ¹²C at 43 MeV/nucleon and the reactions ⁵⁸Ni on ¹²C, ²⁴Mg, and ¹⁹⁷Au at 34.5 MeV/nucleon, and of neutron energy spectra measured in the reaction ³⁵Cl on ^natTa. Properties of the observables have been examined to characterize the neck-like structure formed between the two reaction partners. For the HERACLES collaboration.     

Collective expansion and hadronization in high energy heavy ion collision experiments

An overview of research status of soft physics in high energy heavy-ion collision experiments and recent experimental results are presented.     

Collective expansion and hadronization in high energy heavy ion collision experiments

An overview of research status of soft physics in high energy heavy-ion collision experiments and recent experimental results are presented.     

核物质对称能和重离子碰撞中径向流阈能的同位旋效应

基于同位旋相关的量子分子动力学模型，采用三种不同形式的对称势，研究了¹²⁴Sn+¹²⁴Sn和¹²⁴Ba+¹²⁴Ba对心碰撞时在三种不同对称势下的径向膨胀流，发现径向膨胀流阈能与所采用的对称能形式密切相关，表现出明显同位旋效应，预示着径向膨胀流阈能的同位旋相关性可作为对称能的灵敏探针. 关键词： 径向膨胀流阈能 同位旋效应 重离子碰撞 同位旋相关的量子分子动力学模型     

System-size scan of dihadron azimuthal correlations in ultra-relativistic heavy ion collisions

System-size dependence of dihadron azimuthal correlations in ultra-relativistic heavy ion collision is simulated by a multi-phase transport model. The structure of correlation functions and yields of associated particles show clear participant path-length dependences in collision systems with a partonic phase. The splitting parameter and root-mean-square width of away-side correlation functions increase with collision system size from ¹⁴N + ¹⁴N to ¹⁹⁷Au + ¹⁹⁷Au collisions. The double-peak structure of away-side correlation functions can only be formed in sufficient “large” collision systems under partonic phase. The contrast between the results with partonic phase and with hadron gas could suggest some hints to study onset of confinement.     

Azimuthal correlations between directed and elliptic flow in heavy ion collisions

A method for investigating the azimuthal correlations between directed and elliptic flow in heavy ion collisions is described.The transverse anisotropy of particle emission at AGS energies is investigated within the RQMD model.It is found that the azimuthal correlations between directed and elliptic flow are sensitive to the incident energy and impact parameter.The fluctuations in the initial stage and dynamical evolution of heavy ion collisions are not negligible.