【作者】 张勇；

【导师】 张卫宁；

【作者基本信息】 大连理工大学 ， 理论物理， 2015， 博士

【摘要】 在高能重离子碰撞所形成的高温度、高密度强子源中,粒子与周围介质的相互作用使得处于源内的粒子发生质量偏移,从而导致正反玻色子对的一种压缩关联,人们称之为背对背关联。本文发展了对正反玻色子对背对背关联的相对论蒙特卡罗模拟计算方法,研究了相对论效应对φφ以及K+K-的背对背关联的影响。结果表明,相对论效应对于质量较小的正反K介子的背对背关联影响较大,并且相对论效应对背对背关联的影响还依赖于粒子发射源的冻出温度。针对高能重离子碰撞所产生的粒子发射源的各向异性,研究了各向异性膨胀源的φφ以及K+K-的背对背关联。研宄发现背对背关联不仅与粒子动量的大小有关,而且与粒子动量的方向有关。当粒子动量与源速度方向近似垂直时,背对背关联随着源膨胀速度的增加而变大；当粒子动量与源速度方向近似平行时,背对背关联随着源膨胀速度的增加而变小。相对论流体力学在高能重离子碰撞中被人们广泛地应用,并且成功解释了很多实验现象。本文研究了流体力学演化源的φφ以及K+K-的背对背关联。研究结果表明,对高斯初始能量密度分布的流体力学演化源,正反玻色子的背对背关联随粒子动量大小的变化具有震荡性。背对背关联随着粒子赝快度绝对值的增大而减小,对于横向各向异性的源,当粒子方位角为零时,背对背关联有最小值。最近人们的研究表明,相对论重离子碰撞产生的初始局域平衡系统是涨落不均匀的。本文利用AMPT模型的HIJING产生器模拟RHIC的(?)=200 GeV Au+Au碰撞以及LHC的(?)=2.76 TeV Pb+Pb碰撞系统的涨落初始条件,研究了涨落初始条件流体力学演化源的正反玻色子的背对背关联。研究表明,对于涨落初始条件流体力学演化源,逐事件计算后平均得到的背对背关联函数随动量的变化是平滑的。φφ的背对背关联要大于K+K-的背对背关联,其随碰撞中心度的增加而增加,随碰撞能量的增加而减小,并且表现出明显的赝快度依赖性。由于背对背关联对源冻出点时间的分布非常敏感,本文进一步计算了RHIC的俪=200和62.4 GeV Cu+Cu碰撞流体力学演化源的φ介子背对背关联,发现因为小碰撞系统所对应的源寿命较小,所以有更大的背对背关联。更多还原

【Abstract】 In the hot and dense hadronic sources created in high energy heavy ion collisions, the particle mass-shift due to medium interactions might lead to a squeezed correlation of boson-antiboson pairs, as so called back-to-back correlation (BBC).In this dissertation, we develop a technique of relativistic calculation for the BBC of boson-antiboson pairs by Monte Carlo simulation. The relativistic effects on the BBC func-tions of φφ) and K+K-pairs are investigated. The investigations indicate that the relativistic effect on the BBC functions of K+K-which have smaller mass is significant, and the rela-tivistic effects are sensitive to the particle freeze-out temperature.Motivated by the anisotropy of particle-emitting sources formed in high energy heavy ion collisions, we study the BBC functions of φφ> and K+K-for anisotropic hadronic sources. It is found that the BBC functions depend not only on the magnitude of particle momentum, but also on its direction. As the source expanding velocity increases, the BBC function increases when the particle momentum is approximately perpendicular to the source velocity, and the BBC function decreases when the particle momentum is approximately parallel to the source velocity.Relativistic hydrodynamics has been extensively applied to high energy heavy ion col-lisions. It has successfully explained a lot of experimental phenomenons. We investigate the BBC functions of φφ and K+K- for hydrodynamic sources. The results indicate that the BBC functions exhibit oscillations as a function of the particle momentum for the hy-drodynamic sources with Gaussian initial energy distributions. The BBC functions decrease with increasing absolute value of the particle pseudo-rapidity. For the transverse anisotropic sources, the BBC functions are minimum when the azimuthal angles of the particles reach zero.Recent investigations indicate that the local equilibrium systems created in high ener-gy heavy ion collisions are fluctuated and inhomogeneous. In this dissertation, we use the HIJING generator in AMPT model to simulate the fluctuating initial conditions in the col-lisions of Au+Au at (?) 200 GeV at the RHIC and Pb+Pb at (?)=2.76 TeV at the LHC, and investigate the BBC of boson-antiboson for the hydrodynamic sources with the fluctuating initial conditions. The results indicate that the BBC functions averaged over event-by-event calculations are smoothed as a function of the particle momentum for the hydrodynamic sources with the fluctuating initial conditions. The BBC functions of φφ are greater than those of K+K-. They increase with increasing collision centrality and decrease with increasing collision energy, and exhibit an obvious dependence on pseudo-rapidity. As the BBC is very sensitive to the temporal distribution of source freeze-out points, we further calculate the BBC function of φφ for the hydrodynamic sources for the collisions of Cu+Cu at (?) 200 and 62.4 GeV at the RHIC. The BBC function of φφ for the collisions of Cu+Cu at (?)62.4 GeV is greater because of the shorter lifetime of the small collision system.更多还原