同位旋非对称核物质性质与扩展的BHF方法(Ⅵ)质子和中子平均自由程及其同位旋依赖性

在扩展的Brueckner-Hartree-Fock理论框架内,研究了同位旋非对称核物质中质子和中子的平均自由程,着重讨论了其同位旋依赖性.结果表明:随核物质同位旋非对称度的增大,质子平均自由程减小而中子的平均自由程增大.这表明中子滴线附近的原子核表面对中子比对质子更具透明度.还简单讨论了基态关联效应对平均自由程的影响.     

核物理中的π介子

在强子层次上,原子核或强子物质的基本组元是核子和介子.弄清这些强子的结构,并由基本原理出发研究它们的性质,是当代核物理的重要课题.在各种介子中,π介子是最轻且最重要的介子.关于自由空间中π介子的结构与性质、核介质内π介子的性质、π 核子相互作用与π 核相互作用等问题,始终受到相当多的关注.π介子在核物理中的作用直接联系着手征对称性,汤川秀树关于π介子的最初概念已经大大发展了.有清楚的实验证据表明,核内存在π介子的集体模式,这种集体模式与以前观测到的所有核集体运动模式截然不同.拟对π 核物理的研究现状及值得进一步研究的主要问题予以简要评述. At the hadronic level, nucleons and mesons are constituents of nuclei and hadronic matter. Understanding the structures of hadrons, finding the physics of how the properties of these particles arise from the first principle, are major interests in modern nuclear physics. Among mesons, the lightest and most important one is certainly the pion, thus it is no accident that its structure, properties (both in free space and in nuclear matter) and interactions with nucleons and nuclei have gotten considerable ...     

Neutrino Mean Free Path in Strange Matter at High Temperatures

We investigate the condition that the neutrino energies E_v can be considered to be small enough to be neglected in the energy momentum conservation equation in the reactions d+v_e → u+e^- and u+e^- → d+v_e. It can be simply expressed as E_v < 4α_cμ_e/π, where α_c is the strong coupling constant and μ_e is the electron chemical potential. Then for E_v < 4α_cμ_e/π, we generalize the mean free path for nondegenerate neutrinos given by Iwamoto and obtain a formula that is valid for both nondegenerate and degenerate neutrinos. We also model the mean free path for both nondegenerate and degenerate neutrinos with energies E_v < 4α_cμ_e/π.     

Temperature Dependent Relativistic Microscopic Optical Potential and Mean Free Paths of Nucleons

The microscopic optical potential,mean free paths and Schrodinger equivalent potential of nucleons at finite temperature in nuclear matter are studied based on Walecka's model and thermo field dynamics.We let only the Hartree-Fock self-energy of nucleon represent to be the real part of the microscopic optical potential and the fourth order of meson exchange diagrams,i.e. the core polarization represent the imaginary part of microscopic optical potential in nuclear matter.The microscopic optical potential of finite nuclei is obtained with the local density approximation.     

Three-Body Force Effects on EOS of Asymmetric Nuclear Matter and Proton Fraction in Neutron Star Matter

The three-body force effects on the equation of state and its iso-spin dependence of asymmetric nuclearmatter and on the proton fraction in neutron star matter have been investigated within Brueckner-Hartree-Fock approachby using a microscopic three-body force. It is shown that, even in the presence of the three-body force, the empiricalparabolic law of the energy per nucleon vs. isospin asymmetry β＝ ( N - Z) /A is fulfilled in the whole asymmetry range0≤β≤1 and also up to high density. The three-body force provides a strong enhancement of symmetry energy at highdensity in agreement with relativistic approaches. It also shows that the three-body force leads to a much more rapidincreasing of symmetry energy with density in relatively high density region and to a much lower threshold density forthe direct URCA process to occur in a neutron star as compared to the predictions adopting only pure two-body force.     

利用密度相关的相对论平均场理论对核物质与中子星的研究(英文)

研究和详细地比较了RMF理论中不同的有效相互作用强度的密度依赖性, 并且讨论了这种密度依赖性对于核物质和中子星性质的影响. 对于核物质, 不同的参数组给出的对称核物质的饱和点非常接近, 基本都在经验值的范围内. 对于中子星, 考虑超子后不同参数组给出的质量极限的范围为1.52—2.06 M☉, 半径为10.24—11.38 km.The density dependencies of various effective interaction strengths in the relativistic mean field and their influences on the properties of nuclear matter and neutron stars are studied and carefully compared. The differences of saturation properties given by various effective interactions are subtle in symmetric nuclear matter. The Oppenheimer Volkoff mass limits of neutron stars calculated from different equations of state are 1.52—2.06 M☉, and the radii are 10.24—11.38 km with hyperons included.     

密度相关的相对论平均场理论对核物质和中子星的描述

基于密度相关有效相互作用的相对论平均场理论,研究了核物质和中子星的性质.对核物质的饱和性质,密度相关的相互作用DD-ME1和TW-99给出了与NL1,NL3,NLSH,TM1基本一致的结果;NL2和TM2主要用于计算轻核,与它们的结果差别较大.对于中子星,在低密度区域,各种相互作用给出的介子势场差别不大;在高密度区域,相应的介子势场的差别随密度增加而增大.密度相关的相互作用DD-ME1和TW-99,与NL1,NL3和NLSH的结果相比,其物态方程明显偏软.相应的中子星的最大质量也不同,不同有效相互作用给出的最大质量为2.0—3.0M⊙,从大到小的顺序依次是NLSH?,NL3,NL1,DD-ME1,TW-99,TM1和GL-97,对应的半径为10—14km.     

Determining Nuclear Form factor for Detection of Dark Matter in Relativistic Mean Field Theory

In this work, we derive the nuclear form factor for the spin-independent collision between the WIMPs and nucleus in terms of the relativistic mean field (RMF) theory. Comparison with the traditional form factors which are commonly used in literature is given and it is found that our results are slightly above that of the 2PF model by 4% to 8%, but deviate from the Helm form factor by 15% to 25% for the whole recoil energy spectrum of 0 ∽ 100keV. Moreover, taking Xe and Ge as examples, we show the dependenceof the form factor on the recoil energy.     

Proton Inelastic Mean Free Path in a Group of Organic Materials in 0.05-10MeV Range

Inelastic mean free paths （MFPs） of 0.05-10 MeV protons in a group of 10 organic compounds are systematically calculated. The calculations are based on the method newly derived from the Ashley optical-data model and from the higher-order correction terms in stopping power calculations. Especially, in this method the new and empirical Bloch correction for the inelastic MFP is given. An evaluation for the optical energy loss function is incorporated into the present calculations because of the lack of available experimental optical data for the considered organic compounds expect for kapton. The proton inelastic MFPs for these 10 organic compounds in the energy range from 0.05 to 10 MeV are presented here for the first time, and the combination of these inelastic MFP data and our previous data of stopping power calculation for these bioorganic compounds may form a useful database for Monte Carlo track-structure studies of various radiation effects on these materials.     

同位旋非对称核物质性质与扩展的BHF方法(Ⅶ)中子星物质中质子和中子的1S0态超流性

利用Brueckner-Hartree-Fock和BCS理论方法,计算了β稳定中子星物质中处于 1S0态的质子和中子的对关联能隙,着重研究和讨论了三体核力的影响.结果表明三体核力对β稳定中子星物质中 1S0态中子超流性的影响相对较小,但对 1S0态质子超流性具有重要影响,而且其效应随核子数密度增大而迅速增强.三体核力的主要作用是强烈地抑制了高密度β稳定中子星物质中的 1S0态质子超流性.     

Chromomagnetism in Nuclear Matter

Quarks are color charged particles. Due to their motion there is a strong possibility of generation of color magnetic field. It is shown that however hadrons are color singlet particles they may have non-zero color magnetic moment. Due to this color magnetic moment hadrons can show color interaction. In this paper we have studied the chromomagnetic properties of nuclear matter.     

质子化学位移各向异性的测量

测量质子化学位移各向异性（CSA）有助于表征分子结构与其动力学,但由于¹H-¹H同核偶极耦合相互作用很强及质子各向异性化学位移较小,测量质子化学位移各向异性仍具有巨大挑战,特别是对含有多种质子的生物大分子,如蛋白质.本文简要综述了测量质子化学位移各向异性的方法,包括同核去耦慢速魔角旋转方法、超快魔角旋转方法、对称重耦（RN_n^v）方法、xCSA方法以及量子化学计算方法.我们重点介绍了在高速魔角旋转条件下蛋白质氨基质子化学位移各向异性的测量及它们与氢键长度、蛋白质二级结构之间的关系.     

核物质中的夸克凝聚

核物质中的夸克凝聚是在夸克层次研究核物理遇到的基本问题之一,特别是,它与核环境下强子性质的研究紧密相关．近年来,国内外对此开展了若干研究．简要介绍这方面的研究现状和指出存在的问题． Quark condensates in nuclear matter are one of the key problems for the study of nuclear physics at quark lever, and it is related closely to a deeper understanding of the properties of hadrons in nuclear matter. Recently we have seen some investigations made of the above subject. The present status and open problems are described in this paper.     

Mass Measurements in Nuclear Reactions

The present status of mass measurements from reactions producing nuclei at the driplines, including those unstable to nucleon or cluster emission, is discussed. The results of recent heavy ion and π-meson induced experiments on the study of the superheavy hydrogen isotopes (⁴H, ⁵H, ⁶H), helium (⁹He, ¹⁰He), lithium (¹⁰Li, ¹¹Li) and beryllium (¹³Be) are given. The possibilities of mass measurements in radioactive ion beam experiments are also considered. This revised version was published online in July 2006 with corrections to the Cover Date.     

FST模型中核物质的不可压缩系数

FST模型是近来提出的一个具有手征对称性的核模型.用它研究了零温及有限温核物质的不可压缩系数.并与其它模型得出的结果进行了比较.