RHIC和LHC能区核核碰撞中奇异粒子产生特性的研究

The study of relativistic heavy ion collisions has been becoming one of the most important research areas during the 21st century with the running of Large Hadron Collider(LHC) at CERN.Strangeness production is one of the most important research topics in the relativistic nuclear collisions at the RHIC and LHC,which will help to understand the QGP matter created by heavy-ion collisions. Our study of this research project will mainly study on the strangeness production mechnism in p-p and A-A collisions, by parton and hadron cascade model PACIAE 2.0. Research contents are as follows:. At first, we will make a research on the fraction of reduction mechanism of strange quark suppression and inelastic rescattering in the parton rescattering stage. In the string fragmentation scheme, s quark pair production compared with u (d) quark pair production were assumed to be suppression, and the suppression was denoted as λ. Originally, the suppression was assumed to be fixed. This assumption was confirmed by some experiments at low energies. However, later experiments have shown that this suppression decreases with increasing reaction energy. The new reduction mechanism of strange quark suppression was proposed in 1997, which described the strangeness enhancement in p-p, p-A and A-A collisions at CERN SPS energies successfully. And the inelastic re-scattering processes in parton (re)scattering stage has effect on the strangeness enhancement. In tis part, the fraction of reduction mechanism of strange quark suppression and inelastic rescattering in the parton rescattering stage will be fixed , base on the study of strangeness production mechanism in the heigher energies at LHC.. Secorandly, we will focus on the strangress production mechanism in the nucleus-nucleus collisions at RHIC and LHC. A strangeness enhancement is observed in heavy-ion collisions at rather low centre-of-mass energies. In particular, the K+/π+ ratio becomes more than twice as large as in pp collisions and then decreases again towards RHIC energies. Therefore, the comparison of strangeness production in A–A and p-p collisions at the LHC at comparable centre-of-mass energies per nucleon pair is particularly interesting. Changes in this ratio are indicative of new production mechanisms, as provided, for example, by new collective effects or by the significant contribution of jet fragments to total multiplicity. On the basis of the research of strangeness production distribution, resparct to rapidity, transverse momentum, as well as nuclear modification factor RAA in heavy-ion collisions at RHIC and LHC, the strangeness production mechanism will be given in heavy-ion collisions at RHIC and LHC.

欧洲核子物理研究中心的大强子对撞机（LHC）的运行，使得相对论重离子碰撞研究成为21 世纪具有重大意义的前沿研究领域之一。其中，奇异粒子产生特性是RHIC和LHC能区相对论重离子碰撞中极其重要的研究课题，对奇异粒子产生机制的研究有助于更深入了解碰撞后形成的物质的特性。本申请欲用部分子和强子复合模型PACIAE 2.0，研究在RHIC和LHC能量下质子－质子和核－核碰撞中奇异粒子产生机制。主要研究内容包括：1、确定RHIC和LHC能区质子－质子碰撞中奇异夸克压低减弱机制和非弹散射作用对奇异增强贡献份额。2 、核-核碰撞中奇异粒子产生机制的研究。相比质子－质子碰撞，在核－核的碰撞中将主要考虑核几何效应。通过计算不同中心度情况下核－核碰撞中奇异粒子快度分布，横动量分布以及核修正因子RAA，并与RHIC和LHC能区的实验结果进行比较，从而研究高能重离子碰撞中产生的高温高密物质QGP的特性。

随着欧洲核子物理研究中心的大强子对撞机(LHC Large Hadron Collider) 的运行, 相对论重离子碰撞研究已经成为21 世纪有重大研究意义的前沿研究领域之一。LHC的运行开辟了高能重离子碰撞实验的新纪元，为科学家们全面而又深入地研究QGP性质创造了有利契机。.通过本项目的实施加强了与华中师范大学夸克与轻子物理教育部重点实验室和中国原子能研究院的科研合作，发展和开发PACIAE产生器，深入分析和研究了RHIC能区Au+Au碰撞和LHC能区Pb+Pb碰撞以及p+Pb碰撞奇异粒子产生机制，并对粒子产生机制进行了一些深入探索。.本项目组另一个重要工作是在DKLMT模型基础上,引入描述冷核物质作用的核几何作用函数f(ξ),讨论RHIC能区D-Au碰撞形成单态J/ψ 产物机制,给出了核修正因子(RD-Au)随快度的变化关系,并能较好解释RHIC能区的快度分布特征。.该项目对三峡大学学科建设和人才培养作出了一定贡献。.1. 人才培养：●培养年轻教师四名：熊伟，杜晓超，钟洋，谢伟；● 培养毕业硕士研究生两名：任小文，江泽方；● 在读研究生三名：张聪聪，周京，冯骥； .2. 对学科建设贡献：● 创立了一个有重要影响的校级学术团队，培养一批年轻的学术骨干；创建一个有特色、稳定、可持续发展的研究方向。.3.实验室建设：●在本项目基金支持下，支持了三峡大学省级物理实验示范中心的申报和验收，并最后获得批准；●在本项目的推动下，建立了核工程与核技术高性能计算实验室。