本项目将基于我们组之前发展起来的考虑了sigma、omega、delta、rho、以及pion介子交换的相对论RBUU输运理论，重点研究对pion产生至关重要的母核Delta共振态在其平均场、产生阈、质量分布、以及产生截面等方面的介质修正（特别是同位旋依赖的）效应。我们还将仔细计算在核介质中同位旋依赖的pion及K介子的自能及色散关系。基于这些理论进展，我们将构造一个理论上顾及pion及K输运中各环节诸多因素的、更为自洽的描述中能区同位旋不对称的重离子碰撞的UrQMD微观输运版本。基于此模型版本，我们将重点关注不同同位旋态的pion、K等介子的产生并不断探索由它们构造的敏感依赖于对称能的有效观测量。利用这些观测量并和国内外最新实验结果比较后抽取对称能在高密区的密度依赖形式。这些研究将为最终理解之前出现的所谓的“高密对称能谜团”提供更加坚实的理论基础和更为自洽的模型基础。

Based on the relativistic BUU transport theory developed by our group before, in which the sigma, omega, delta, rho, and pion meson exchanges are considered, the key research of this project is to focus on the effects of medium modifications (especially its isospin depdence) on the mean field, production threshold, mass distribution, and production cross sections and so on of the Delta resonance which is the parent particle of the pion meson so as to be essential to its production. We will also carefully calculate the isospin-dependent self-energies and dispersion relations of the pion and kaon mesons in the nuclear medium. Based on these theoretical advances, we will theoretically construct a new microscopic transport version of the UrQMD model with which the isospin-asymmetric heavy-ion-collisions (especially related to many factors when considering transport of pion and kaon mesons) at intermediate energies can be more self-consistently described. Further, based on this model version, we will concentrate on the production of separate isobars of pion and kaon mesons, and constantly explore the effective and sensitive observables for the symmetry energy which are mainly constructed by them. Using these observables to compare with the latest experimental data at home and abroad, the density dependent form of the symmetry energy especially at supranormal densities will be extracted finally. These studies will provide both a more solid theoretical basis and a more self-consistent model basis for understanding the so-called "high-density symmetry-energy puzzle" that appeared before in the community.