近日，西班牙圣地亚哥德孔波斯特拉大学的Sergio Barrera Cabodevila及其研究团队取得一项新进展。经过不懈努力，他们对夸克-胶子等离子体的夸克产生和热化过程进行研究。相关研究成果已于2024年6月21日在国际知名学术期刊《高能物理杂志》上发表。
该研究团队首先组装了一套完整的扩散近似玻尔兹曼方程(BEDA)，用于研究非平衡系统中的热化/水动力学以及无质量夸克和反夸克的产生。在BEDA中，一般系统的时间演化由以下时空相关量表征: 射流猝灭参数，有效温度，以及两个特定于每个夸克味的参数，这些参数描述了胶子和夸克/反夸克之间通过22个不同过程发生的转换。
特别地，对于后两个量，研究人员定义了一个有效的净夸克化学势，它等于系统达到热平衡后的净夸克化学势。然后，他们研究了在一个最初仅充满胶子的空间均匀系统中，热化过程以及三种不同味的无质量夸克和反夸克的产生机制。
研究人员获得了初始非常稠密或稀释体系的热化和夸克产生的参数化理解，对初始胶子占据数位于中间值（0附近）的情况进行了细致的数值模拟。结果显示，在广泛的条件下，这些体系的最终平衡时间比纯粹的胶子系统要长出一个数量级。此外，在热化过程的最后阶段，他们发现胶子比夸克和反夸克更早地热化，经历了自上而下的热化过程。
附：英文原文
Title: Quark production and thermalization of the quark-gluon plasma
Author: Barrera Cabodevila, Sergio, Salgado, Carlos A., Wu, Bin
Issue&Volume: 2024-06-21
Abstract: We first assemble a full set of the Boltzmann Equation in Diffusion Approximation (BEDA) for studying thermalization/hydrodynamization as well as the production of massless quarks and antiquarks in out of equilibrium systems. In the BEDA, the time evolution of a generic system is characterized by the following space-time dependent quantities: the jet quenching parameter, the effective temperature, and two more for each quark flavor that describe the conversion between gluons and quarks/antiquarks via the 2 2 processes. Out of the latter two quantities, an effective net quark chemical potential is defined, which equals the net quark chemical potential after thermal equilibration. We then study thermalization and the production of three flavors of massless quarks and antiquarks in spatially homogeneous systems initially filled only with gluons. A parametric understanding of thermalization and quark production is obtained for either initially very dense or dilute systems, which are complemented by detailed numerical simulations for intermediate values of initial gluon occupancy f0. For a wide range of f0, the final equilibration time is determined to be about one order of magnitude longer than that in the corresponding pure gluon systems. Moreover, during the final stage of the thermalization process for f0 ≥ 10-4, gluons are found to thermalize earlier than quarks and antiquarks, undergoing the top-down thermalization.
DOI: 10.1007/JHEP06(2024)145
Source: https://link.springer.com/article/10.1007/JHEP06(2024)145