新的核势下的核物质状态方程与应用的研究

On the basis of the one-boson-exchange potential (OBEP)model the microscopic three-nucleon forces (TNF) will be constructed consistently with the recently completed Nijmegen extended soft-core 08 (ESC08) nucleon-nucleon potential which is for the first time based on a unified theoretical framework. In recent years, with the highly realistic nucleon-nucleon interaction N3LO (at Next-to-Next-to-Next-to Leading Order) obtained, the three-nucleon forces N2LO (at Next-to-Next-to Leading Order) have been extensively developed based on chiral perturbation theory. Combined with the old phenomenological TNF, namely, Urbana IX TNF, and the microscopic TNF which we are already familiar with together , in total the three kinds of TNF are achieved at present. Employing the Brueckner-Hartree-Fock approach，we will systematically compare the effect of these three categories of TNF on the properties of the isospin symmetric and asymmetric nuclear matter，and make a clear distinction among the different TNF components. Since the nucleon-nucleon cross section plays a significant role in the simulation of the heavy-ion collisions at medium and high energies, these new versions of two-nucleon potentials and their corresponding three-nucleon forces are adopted in Brueckner-Hartree-Fock calculations, and the medium effect of the nucleon-nucleon cross section in the nuclear matter will be investigated. As well, to check the modification brought by the TNF, it is better to fulfill the application and extension from infinite nuclear matter to the structure of the finite nuclei in terms of liquid droplet model. Thus we will put more emphasis on the binding energies and the distribution information of the neutrons at the surface of some neutron-rich nuclei. As a result of the strong connection between the neutron-skin thickness of 208Pb and the pressure of pure neutron matter near saturation density, our study will provide some additional correlations between neutron skin of 208Pb and several neutron-star properties. Furthermore,we will compare the theoretical binding energis calculated of some nuclei with the experimental ones, which in turn offers the restrict on the range of some free parameters that appear in TNF.

本项目首先依据单玻色子交换势（OBEP）模型，构建与新的两体Nijmegen软芯势ESC08相自洽的微观三体核力。近年来，建立在手征微扰理论基础上的高精度的两体相互作用势N3LO和三体核力N2LO充分发展起来。结合熟悉的唯象三体核力-Urbana IX 势和以OBEP为基础的微观三体核力，在Brueckner-Hartree-Fock理论方法下，系统地比较这三种三体核力对同位旋对称和非对称的核物质状态方程的影响和区别。基于上述新的两体和三体力，重点研究介质中的核子-核子散射截面，及丰中子核的结合能和表面中子分布信息，前者是模拟重离子核反应所需要的关键输入量，后者属于从核物质到有限核结构研究的基本应用。通过对铅208中子皮厚度的研究，不仅能够提供有限核的中子皮厚度与天体物理中致密星体的一些基本特性的联系，而且，通过和实验上有限核的结合能数据作比较，反过来为三体核力中的不定参数提供一定的限制。

对同位旋非对称核物质状态方程的研究一直是核物理领域研究的基本课题之一。它不仅在核天体物理中具有很重要的研究意义，而且还密切关联着核物理领域中的核结构研究的丰中子核的中子分布等关键信息，尤其是中子皮的厚度研究。而且，最近几年，以QCD理论为指导思想，由手征微扰理论推导出的新的手征核力也迅速发展起来。在本项目中，我们采用新的两体相互作用势和与之相对应的三体核力，在Brueckner-Hartree-Fock（BHF）核多体方法框架下，计算了对称核物质和丰中子物质的状态方程和对称能。与核物质性质相比较，在有限核物理的研究中，根据液滴模型的思想，我们考虑了表面能和库仑能的修正贡献。因此，在考虑到这两部分的修正贡献后，我们研究了一系列稳定的丰中子核（例如48Ca，78Ni，90Zr，208Pb， 132Sn等）的表面中子分布信息和结合能，并且和实验进行了比较。为了更加清楚地表明核物质的性质以及诸多现实核力之间的关联效应，我们研究了现代核子-核子两体相互作用势的关联强度。采用不同新的核子-核子相互作用势，在BHF框架下，计算了关联强度系数和核子动量分布，损伤波函数之间的关系，并且比较了各种两体核势之间的差异。为了进一步完善和扩展BHF的多体理论，在采用空隙选择和连续选择两种情况下，研究了BHF理论模型的三阶空穴展开项的贡献，重点给出了该模型的三阶空穴展开项对对称核物质和中子物质的结合能的贡献。研究表明，特别是具有弱相关性的新的手征核势，关联强度系数紧密联系着BHF方法的粒子-空穴线展开的收敛性，这一研究结果再一次证明了若想得到满意的核物质饱和性质，必须引入三核子的相互作用。以上部分研究成果发表在在国际权威期刊Physical Review C 上，有一篇论文被Physical Review C期刊选为“EDITORS’SUGGESTION（HIGHLIGHTED）”， 为该领域的研究热点。