分类： 物理学 >> 核物理学 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要： A novel method to determine the density and temperature of a system constituted by fermions and/or bosons is proposed based on quantum fluctuations. For fermions system, the results in the limit where the reached temperature T is small and where there is no constraint for the reached temperature T compared to the Fermi energy f at a given density are given, respectively. Quadrupole and multiplicity fluctuation relations are derived in terms of T/f. We compared the two set results in the limit when T is much smaller compared to Fermi energy f and they are consistent, as expected. The classical limit is also obtained for high temperatures and low densities. For bosons system, quadrupole and multiplicity fluctuations using Landau's theory of fluctuations near the critical point for a Bose-Einstein condensate (BEC) at a given density are derived. As an example, we apply our approach to heavy ion collisions using the Constrained Molecular Dynamics model (CoMD) which includes the fermionic statistics. The multiplicity fluctuation quenching for fermions is found in the model and confirmed by experimental data. To reproduce the available experimental data better, we propose a modification of the collision term in the approach to include the possibility of collisions. The relevant Bose-Einstein factor in the collision term is properly taken into account. This approach increases the yields of bosons relative to fermions closer to data. Boson fluctuations become larger than one as expected.
分类： 物理学 >> 核物理学 提交时间： 2023-09-07
摘要： The thermodynamic properties of charged particles, such as the energy density, pressure, entropy density, particle density, and squared speed of sound at the kinetic freeze-out in the mathrm{Au+Au} collisions from the relativistic heavy ion collider (RHIC) beam energy scan program ( sqrt{s_ text{NN}}=7.7--200 GeV) and in the mathrm{Cu+Cu} collisions at sqrt{s_ text{NN}}=62.4, 200 GeV are studied using the thermodynamically consistent Tsallis distribution. The energy density, pressure, and particle density decrease monotonically with the collision energy for the same collision centrality; These properties also decrease monotonically from the central to peripheral collisions at the same collision energy. While the scaled energy density varepsilon/T^4 and scaled entropy density s/T^3 demonstrate the opposite trend with the collision energy for the same collision centrality. There is a correlation between varepsilon/T^4 and s/T^3 at the same centrality. In addition, the squared speed of sound was calculated to determine that all the collision energies share nearly the same value at different collision centralities.
分类： 物理学 >> 核物理学 提交时间： 2023-10-23
摘要： The pseudo-rapidity distributions of the charged particles produced in the asymmetric collision systems p+Al, p+Au and ^3He+Au at sqrt{s_{NN}} = 200 GeV are evaluated in the framework of a fireball model with Tsallis thermodynamics. The fireball model assumes that the experimentally measured particles are produced by fireballs following the Tsallis distribution and it can effectively describe the experimental data. Our results as well as previous results for d+Au collisions at sqrt{s_{NN}} = 200 GeV and p+Pb collisions at sqrt{s_{NN}} = 5.02 TeV validate that the fireball model based on Tsallis thermodynamics can provide a universal framework for pseudo-rapidity distribution of the charged particles produced in asymmetric collision systems. We predict the centrality dependence of the total charged particle multiplicity in the p+Al, p+Au and ^3He+Au collisions. Additionally, the dependences of the fireball model parameters (y_{0a}, y_{0A}, sigma_{a} and sigma_{A}) on the centrality and system size are studied.
分类： 物理学 >> 核物理学 提交时间： 2025-04-30
摘要： 相对论核核(A+A)碰撞中，粒子平均横动量〈p_T〉是一个重要的实验观测量，反映了软质强子的特性和热核物质的性质，对其进行系统研究有助于获取碰撞系统的演化信息。利用位于美国长岛的相对论重离子对撞机(RHIC)上STAR实验组和位于欧洲日内瓦的大型强子对撞机(LHC)上ALICE实验组提供的相对论核核碰撞中心快度区末态粒子的实验数据，包括金核-金核(Au+Au)、铜核-铜核(Cu+Cu）、铀核-铀核(U+U)、铅核-铅核(Pb+Pb)碰撞，应用唯象公式对末态粒子平均横动量随碰撞中心度、粒子质量及碰撞能量的依赖关系进行拟合，均能较好地描述现有实验数据。系统研究证实，末态鉴别粒子的平均横动量与碰撞中心度之间的线性关系具有普适性，碰撞中心度是研究粒子平均横动量的优选物理量。同时粒子平均横动量随碰撞中心度的唯象函数公式的拟合参数随碰撞能量满足幂律关系也具有普适性。在同一碰撞能量与系统中，鉴别粒子的平均横动量随粒子质量定性上满足线性关系，有少量粒子的数据偏离该线性关系，这可能与粒子产生机制的细节有关。同时，在同一碰撞中心度下，鉴别粒子的平均横动量对碰撞能量对数的依赖遵循幂律关系且具有普适性。
分类： 物理学 >> 核物理学 提交时间： 2025-04-02
摘要： 相对论核核(A+A)碰撞中，粒子平均横动量〈p_T〉是一个重要的实验观测量，反映了软质强子的特性和热核物质的性质，对其进行系统研究有助于获取碰撞系统的演化信息。利用位于美国长岛的相对论重离子对撞机(RHIC)上STAR实验组和位于欧洲日内瓦的大型强子对撞机(LHC)上ALICE实验组提供的相对论核核碰撞中心快度区末态粒子的实验数据，包括金核-金核(Au+Au)、铜核-铜核(Cu+Cu）、铀核-铀核(U+U)、铅核-铅核(Pb+Pb)碰撞，应用唯象公式对末态粒子平均横动量随碰撞中心度、粒子质量及碰撞能量的依赖关系进行拟合，均能较好地描述现有实验数据。系统研究证实，末态鉴别粒子的平均横动量与碰撞中心度之间的线性关系具有普适性，碰撞中心度是研究粒子平均横动量的优选物理量。同时粒子平均横动量随碰撞中心度的唯象函数公式的拟合参数随碰撞能量满足幂律关系也具有普适性。在同一碰撞能量与系统中，鉴别粒子的平均横动量随粒子质量定性上满足线性关系，有少量粒子的数据偏离该线性关系，这可能与粒子产生机制的细节有关。同时，在同一碰撞中心度下，鉴别粒子的平均横动量对碰撞能量对数的依赖遵循幂律关系且具有普适性。
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