Probing the Isospin Dependence of In-Medium Nuclear Effective Interactions at the Rare Isotope Accelerator

同位旋不对称性是对有限核和/或无限核物质中中子和质子数目不平衡的度量。在极端同位旋不对称系统中，如中子星，中子和质子是如何相互作用的？在富含中子的核物质中，状态方程，即能量、密度和温度之间的关系，是如何作为同位旋不对称性的函数变化的？这些问题的答案对中子星的结构和超新星爆炸的动力学具有重大的天体物理学意义。然而，天体物理观测过于有限，无法回答这些问题。幸运而有趣的是，这些问题可以通过在计划中的美国稀有同位素加速器(RIA)和其他国外竞争设施中使用短寿命同位素束引发的核反应来进行实验研究。与这些实验相关的物理学目前是核科学的主要推动力之一，也是核科学的前沿。特别是，利用RIA上的高能丰中子束，可以创造出具有明显的同位旋不对称性和超过正常核物质饱和密度两倍以上的压缩的核物质的暂态。因此，放射免疫分析将提供一个独特的机会，在同位旋不对称和密度的极端条件下探索核子物质的性质。为了促进介质中核有效相互作用与同位旋相关的实验研究和核状态方程的成功，我将通过研究富中子物质的新性质及其在稀有同位素束引起的核反应中的表现，对计划实验和解释数据的几个重要问题进行理论研究。我的主要工作将集中在开发放射性束流引起的核反应的新模型；确定同位旋自由度在反应动力学中的作用；确定可用于提取关于介质中核有效相互作用的同位旋依赖关系的关键信息的实验观察量；以及约束同位旋不对称核物质的状态方程。

Isospin asymmetry is a measure of the imbalance between the numbers of neutrons and protons in finite nuclei and/or infinite nuclear matter. How do neutrons and protons interact among themselves in extremely isospin asymmetric systems, such as, neutron stars? How does the equation of state, i.e., a relationship among energy, density and temperature, change as a function of isospin asymmetry in neutron-rich nuclear matter? Answers to these questions have significant astrophysical ramifications for the structure of neutron stars and the dynamics of supernova explosions. However, astrophysical observations are too limited to answer these questions. Fortunately and interestingly, these questions can be studied experimentally by using nuclear reactions induced by short-lived isotope beams at the planned Rare Isotope Accelerator (RIA) in the USA and other competing facilities abroad. The physics associated with these experiments is currently one of the major thrusts and at the foremost front of nuclear sciences. In particular, with high energy neutron-rich beams at RIA, a transient state of nuclear matter with appreciable isospin asymmetry and compression of more than twice the saturation density of normal nuclear matter can be created. RIA will thus provide a unique opportunity to explore the nature of nucleonic matter under extreme conditions of isospin asymmetry and density. To facilitate the success of the experimental research on the isospin dependence of the in-medium nuclear effective interactions and the nuclear equation of state, I shall carry out theoretical studies on several issues important for planning experiments and interpreting data by investigating novel properties of neutron-rich matter and their manifestations in nuclear reactions induced by rare isotope beams. The major foci of my work will be on developing new models for nuclear reactions induced by radioactive beams; identifying the role of isospin degree of freedom in the reaction dynamics; determining experimental observables that can be used to extract critical information about the isospin dependence of the in-medium nuclear effective interactions; and constraining the equation of state of isospin asymmetric nuclear matter.