Effective DBHF Method For Asymmetric Nuclear Matter And Finite Nuclei

A new decomposition of the Dirac structure of nucleon self-energies in the Dirac Brueckner-Hartree-Fock (DBHF) approach is adopted to investigate the equation of state for symmetric,asymmetric,and neutron matter. The DBHF G matrix is decomposed as G = V + AG,where V is the realistic nucleon-nucleon (NN) interaction and A G a correlation term. The nucleon DBHF self-energy in the nuclear medium,therefore,can be calculated with the G matrix in the relativistic Hartree-Fock approximation. With the calculated nucleon self-energy in the DBHF,we extract nucleon effective interactions hi the framework of the relativistic mean field theory (RMF),which contains the effect of the nucleon-nucleon short-range correlation and information of the isospin structure. Applying the effective interaction,which is composed of density dependent meson-nucleon coupling constants,we study the properties of finite nuclei and come to some useful conclusions.The DBHF method is one of the most reliable and feasible microscopic methods for the description of effective interactions in the nuclear medium. It reproduces the empirical saturation properties of nuclear matter successfully. However,the Dirac structure of the nucleon self-energy in the DBHF can not be explicitly obtained in a numerical calculation. Therefore a reliable decomposition of the DBHF G matrix is desirable,which is significant for the extraction of effective interactions,especially for the isospin dependence of the effective interactions. There are several ways to obtain the DBHF self-energy from the G matrix used before,such as a simple method,where the Dirac structure of the nucleon self-energy is obtained from the momentum dependence of the single-particle energy,and a projection method. All of them have their drawbacks. Very recently,Schiller and Muether at Tubingen University suggested a new decomposition approach of the DBHF G matrix,and used to calculate the nucleon self-energy. They,separate the G matrix into a barenucleon-nucleon interaction V and correction term A G. The projection method is only applied to the correlation term A G,which is parameterized by four pseudo-mesons. Then the nucleon self-energy in the DBHF can be calculated with the G matrix in the relativistic Hartree-Fock approximation. Shortcomings observed in other methods are removed and a satisfactory description of symmetric nuclear matter is reached. We calculate the scalar and vector self-energy in symmetric and asymmetric nuclear matter with this new decomposition approach of the G matrix. The properties of symmetric,asymmetric,and neutron matter are systematically studied in this effective DBHF approach.The results show that binding energies per nucleon at each density and various asymmetry parameters fulfill the empirical parabolic law and the asymmetry energy is density dependent. It is found that both scalar and vector potentials of neutron in the neutron rich nuclear matter become stronger although the isospin dependence is not stronger. We compare our results with those in a simple method,where the DBHF nucleon self-energies are extracted from the momentum dependence of the single-particle energy. A significant difference on the scalar self-energy and effective mass of neutrons in asymmetric nuclear matter,especially in neutron matter,is observed. The difference would result in an unreasonable sigh of the extracted effective couplings for isovector mesons. The effective coupling constants including isoscalar and mesons and isovector and mesons in the RMF are extracted from the DBHF results in symmetric and asymmetric nuclear matter. Two sets of effective interactions in the RMF approach are deduced by imposing a condition,where the DBHF scalar and. vector self-energy or scalar self-energy and binding energy per nucleon at each density and asymmetry parameter are reproduced,respectively. These effective coupling constants of mesons embody the feature of the DBHF results,such as short-range correlations and the structure of isospin. In general,the effective meson coupling co...