发表机构
School of Science, Huzhou Normal University; Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research; Institute of Modern Physics, Chinese Academy of Sciences（湖州师范学院理学院; 约飞联合核子研究所波戈留博夫理论物理实验室; 中国科学院近代物理研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究在UrQMD模型中引入介质内NN非弹性截面和短程关联高动量尾，探究其对中能重离子碰撞π介子产生的影响，发现两者共同作用可合理再现HADES和FOPI实验数据。
AI 中文摘要
中能重离子碰撞（HICs）中的π介子产生为核态方程以及反应动力学的同位旋依赖性提供了灵敏的探针。特别是，阈值附近的π介子产生强烈地受到核子-核子（$NN$）非弹性截面以及核子动量分布中高动量成分的影响。为了探究这两个因素对π介子产生及带电π介子比率的影响，我们将相对论Boltzmann-Uehling-Uhlenbeck输运理论中计算得到的介质内$NN$非弹性截面以及由短程关联引起的高动量尾（HMT）引入到超相对论量子分子动力学（UrQMD）模型中。通过模拟中能Au+Au碰撞，我们发现$NN$非弹性截面的介质修正通过降低稠密物质中$N\Delta$产生的概率来抑制π介子多重性。另一方面，HMT增强了核子的高动量成分，并改变了单个$NN$碰撞中的可用能量，从而影响$NN\rightarrow N\Delta$反应及随后的π介子产生。同时包含这两种效应时，HADES测量的π介子产额和FOPI测量的$\pi^-/\pi^+$比率可以被合理地再现。这些结果强调了在输运模型研究中，一致地纳入介质内反应截面和由短程关联引起的高动量成分对于重离子碰撞中π介子产生的必要性。
英文摘要
Pion production in intermediate-energy heavy-ion collisions (HICs) provides a sensitive probe of the nuclear equation of state and of the isospin dependence of reaction dynamics. In particular, pion production near threshold is strongly affected by the nucleon-nucleon ($NN$) inelastic cross sections and by the high-momentum components of the nucleon momentum distribution. To explore the influence of these two ingredients on pion production and charged-pion ratios, the in-medium $NN$ inelastic cross sections calculated within the relativistic Boltzmann-Uehling-Uhlenbeck transport theory and the short-range-correlation-induced high-momentum tail (HMT) are introduced into the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model. By simulating Au+Au collisions at intermediate energies, we find that the in-medium modification of the $NN$ inelastic cross sections suppresses the pion multiplicity by reducing the probability of $NΔ$ production in dense matter. The HMT, on the other hand, enhances the high-momentum components of nucleons and modifies the available energy in individual $NN$ collisions, thereby affecting $NN\rightarrow NΔ$ reactions and the subsequent pion production. With the simultaneous inclusion of these two effects, the pion yields measured by HADES and the $π^-/π^+$ ratio measured by FOPI can be reasonably reproduced. These results highlight the need to incorporate both in-medium reaction cross sections and short-range-correlation-induced high-momentum components consistently in transport-model studies of pion production in heavy-ion collisions.
Comments10 pages, 8 figures
