高能核碰撞中带电多重数快度与能量和中心度的关系

用强子–弦级联模型JPCIAE及相应的Monte Carlo事例产生器研究相对论性核–核碰撞中带电粒子多重数的赝快度密度对能量和中心度的依赖关系.无需另调任何模型参数的条件下,此模型可以同时较好地描述相对论性pp实验数据及PHOBOS和PHENIX实验组的Au+Au实验数据.本文指出:因〈N_part〉并非严格定义的物理量,致使实验上和理论上确定〈N_part〉有一定任意性,从而使得每参加者核子对的带电粒子赝快度密度随着〈N_part〉的增加可能逐渐增大,也可能逐渐减小,因此用它来区分粒子产生机制是欠妥的.     

Study of Pion-Source Size in Relativistic Nuclear Collisions

The BoseEinstein correlation of pion pairs is calculated using the space-time and four-momentum distributions Gom an event generator URASiMA for 200 AGeV/c Pb + Pb and compared to pion correlation measurement from CERN experiment of NA44. The spacetime distributions of the simulated pion-emitting source are also analyzed.     

Charged Multiplicity Density and Number of Participant Nucleons in Relativistic Nuclear Collisions

The energy and centrality dependencies of charged particle pseudorapidity density in relativistic nuclearcollisions were studied using a hadron and string cascade model, JPCIAE. Both the relativistic p+p experimental dataand the PHOBOS and PHENIX Au+Au data at RHIC energy could be fairly reproduced within the framework ofJPCIAE model and without retuning the model parameters. The predictions for Pb + Pb collisions at the LHC energywere also given. We computed the participant nucleon distributions using different methods. It was found that thenumber of participant nucleons is not a well defined variable both experimentally and theoretically. Thus it may beinappropriate to use the charged particle pseudorapidity density per participant pair .as a function of the number ofparticipant nucleons for distinguishing various theoretical models.     

Some Possible Asymmetry Effects of Nuclear Matter in Relativistic Heavy Ion Collisions

The asymmetry dependence of nuclear incompraeaibility and that of nuclear critical temperature are calculated baaed on a Thomas-Fermi model with Seyler-Blanchard interaction. It is found that the asymmetry effects are big enough to allow for checking the existence of these effects in relativistic heavy-ion collision experiments.     

Some Aspects of Nuclear Structure in Relativistic Approach

The nucleon effective interaction in the nuclear medium is investigated in the framework of the DiracBrueckner-Hartree-Fock (DBHF) approach. A new decomposition of the Dirac structure of nucleon self-energy in the DBHF is adopted for asymmetric nuclear matter. The properties of finite nuclei are investigated with the nucleon effective interaction. The agreement with the experimental data is satisfactory. The relativistic microscopic optical potential in asymmetric nuclear matter is investigated in the DBHF approach. The proton scattering from nuclei is calculated and compared with the experimental data. A proper treatment of the resonant continuum for exotic nuclei is studied. The width effect of the resonant continuum on the pairing correlation is discussed. The quasiparticle relativistic random phase approximation based on the relativistic mean-field ground state in the response function formalism is also addressed.     

Some Aspects of Nuclear Structure in Relativistic Approach

The nucleon effective interaction in the nuclear medium is investigated in the framework of the DiracBrueckner-Hartree-Fock (DBHF) approach. A new decomposition of the Dirac structure of nucleon self-energy in the DBHF is adopted for asymmetric nuclear matter. The properties of finite nuclei are investigated with the nucleon effective interaction. The agreement with the experimental data is satisfactory. The relativistic microscopic optical potential in asymmetric nuclear matter is investigated in the DBHF approach. The proton scattering from nuclei is calculated and compared with the experimental data. A proper treatment of the resonant continuum for exotic nuclei is studied. The width effect of the resonant continuum on the pairing correlation is discussed. The quasiparticle relativistic random phase approximation based on the relativistic mean-field ground state in the response function formalism is also addressed.     

Analysis of Collective Flow in High Energy Heavy-Ion Collisions in the Relativistic VUU Approach

We have calculated the collective flow for Ar+KCl collisions of 1200 MeV/A by using the relativistic Vlasov-Uehling- Uhlenbeck (VUU) equation based on the QHD-I model of Walecka. The tensitivity of flow characterized by C(ψ)a nd (P_x(Y))to mean field and in-medium NN scattering cross section is studied. It is found that the azimuthal correlation function C(ψ) is reduced dramatically after inserting the collision term and then varies very slowly between NN cross sections from σ = 10 mb to 55 mb and reaches the minimum at σ = 35 mb, while the in-plane mean transverse momentum (P_x(Y))in creases slowly all the way from σ = 0 mb to 55 mb. The collective flow is very sensitive to the momentum dependence (indicated by the effective mass m⁰) of the mean field and less sensitive to the compression modulus K and the cross sections from σ = 10 mb to 55 mb. The numerical results were compared with the experimental data, and we found that the agreement for both (P_x(Y)) and C(ψ) can be reached with the same set of mean field parameters as well as the appropriate NN cross section in collision terms.     

相对论重离子碰撞的趋平衡问题

从相对论ＢＵＵ理论出发,研究了１ＧｅＶ／ｕ能区重离子碰撞全局和局域平衡性质．研究结果表明,在该能区平均场对反应动力学过程仍有相当的作用;对有限核系统的反应动力学过程的时间演化的研究表明,有限核系统未能达到全局平衡,在中心区基本达到局域平衡．因而在该能区的重离子碰撞中引入完全热平衡概念时,需谨慎考虑．The equilibration in relativistic heavy ion collisions for systems 16 O+ 16 O, 40 Ca+ 40 La and 139 La+ 139 La is studied with RBUU theory. We have found that the mean field still plays a role in addition to the collision term in the equilibration process in relativistic heavy ion collisions at energy around 1 GeV/u. For finite systems, the systems do not reach complete equilibrium. But at the center zone, the local equilibrium is almost reached.     

Vorticity and Particle Polarization in Relativistic Heavy-Ion Collisions

Physics of Atomic Nuclei - We review studies of vortical motion and the resulting global polarization of $$Lambda$$ and $$bar{Lambda}$$ hyperons in heavy-ion collisions, in particular, within...     

Relativistic Mean-Field Approach to Infinite Nuclear Matter and Neutron Star

The properties of infinite nuclear matter and neutron star are studied theoretically in relativistic mean-field (RMF) approach with three typical parameter sets NL1, NL-SH and TM1. It is found that all these new RMF parameter sets can very satisfactorily reproduce the properties of high density matter. Among these parameter sets, TM1, with a nonlinear ω term, reproduces a slightly smaller energy, piessure and neutron star mass than NL-SH and NL1. The ρ meson field has a large influence on the properties of neutron star and infinite nuclear matter. A detailed discussion for the significance of numerical results is also given.     

相对论重离子碰撞中的K+产生及集体流

用自洽的相对论BUU模型研究了相对论重离子碰撞的K⁺产生及流,研究结果表明K⁺集体流在相对论重离子碰撞中对核态方程(EOS)和K–N标量吸引项(∑_KN)是敏感的,在对K⁺流中心度依赖的研究中发现在大碰撞参数时有反向流出现,可为确定∑_KN值提供更为有效的信息.对K⁺产生的总产额及各个不同道的贡献与EOS和∑_KN关系进行了细致分析,表明N△道对K⁺产生的贡献和影响都是最显著的; 不同道的贡献对∑_KN的灵敏程度不同,其中∑_KN对N△道的影响要比对πB道的大.     

相对论重离子碰撞与夸克物质

介绍了相对论重离子碰撞与夸克物质研究领域的有关最新进展.讨论了QCD热力学与量子输运理论,对于与QCD相变紧密联系的几个热点问题作了评述,最后分析了该研究领域在近期发展前景.     

Relativistic Heavy Ion Collisions and Quark Matter

The recent progress in the field of relahvistic heavy ion collisions and quark matter is reviewed. Especially, the QCD thermodynamics, quantum transport theory, and some hot topics related to the QCD phase transitions are analyzed in detail. The outlook for thes field is also briefly discussed.     

Search for Tetraquarks in Relativistic Heavy-Ion Collisions

Tetraquarks can be produced in relativistic heavy-ion collision. The yield of this kind of tetraquarks can increase significantly soon as the formation of QGP after the collision. If there is no phase transition after collision, the upper bound of the production of this four-quark states can be estimated from the free hadronlc gas model for nuclear matter. The relative yield ratio of tetraquark cs^-s^-s to Ω is less than 0.0164.     

Search for Tetraquarks in Relativistic Heavy-Ion Collisions

Tetraquarks can be produced in relativistic heavy-ion collision. The yield of this kind of tetraquarks can increase significantly soon as the formation of QGP after the collision. If there is no phase transition after collision, the upper bound of the production of this four-quark states can be estimated from the free hadronic gas model for nuclearmatter. The relative yield ratio of tetraquark cs(s)(s) to Ω is less than 0.0164.     

The Effect of Secondary Collisions in the Rapidity Distribution in Relativistic Heavy Ion Collisions

Based on the participant model the effect of secondary collisions in relativistic heavy ion collisions is analyzed by introducing additional contributions in fragmentation regions. The rapidity distributions of n of NA35 and WA80 groups are well reproduced. Special improvement is shown in the target fragmentation region.     

相对论重离子碰撞的温度涨落与热容

使用LUCIAE3.0模型模拟了SPS能区Pb+Pb和C+C在不同能量(E_lab=20—200A GeV)和不同中心度下的重离子碰撞.并通过逐个事件的粒子温度涨落提取出了相应粒子的热容,发现对于同一碰撞系统,单位发射粒子的热容随碰撞能量的升高而下降直至饱和,随着碰撞参数b的增大而减小,而且发现单位发射粒子的热容具有随粒子质量的变大而变大的关系.同时还发现不同碰撞系统中同一种粒子具有相同的单位发射粒子热容,并给出了相应的解释.