New Effective Nuclear Force And Application Within Covariant Density Functional Theory

The nucleus is a complex microscopic quantum manybody self-bound system.Although nuclear physics has lasted more than a century since its birth,the study of nuclear properties is still full of challenges.Based on the understanding of nucleon-nucleon interaction in nu-clei,namely nuclear force,combined with different nuclear many-body methods,the nuclear theoretical model describing the complexity of nuclei has been developed.Nuclear force is a residual strong interaction,including central force,spin-orbit coupling,tensor force and so on.At present,meson exchange image is one of the most successful theories to describe nuclear force.The effective nuclear force is a common and very effective method to describe the nuclear system.The relativistic mean field(RMF)theory based on meson exchange image of nuclear force naturally considers the important spin-orbit coupling in nuclear force,and has been widely used in the research of nuclear properties with great success.However,recent studies of pseu-dospin symmetry recovery in nuclear structures and new magic number structures in unstable nuclei show that the effective nuclear force under RMF approximation still has some limitations in dealing with the medium effect of nuclear force and spin-orbit coupling.In order to achieve a reliable description of the properties of unstable nuclei,the new effective nuclear force under RMF approximation are developed by optimizing the treatment of the medium effect of the nu-clear force and considering the new meson field degree of freedom,and the new magic number structure and dropline positions in unstable nuclei are studied.The main contents are as follows:Development of new effective nuclear forces under RMF approximation Based on the density dependence relativistic mean field theory,a new effective interaction DD-LZ1 is developed by fitting to the bulk properties of nuclear matter and finite nuclei,which can improve the description of medium effect in nuclei and systematically improve the description accuracy of nuclear mass.On this basis,we introduce the Lorentz?-meson tensor coupling and develop a new effective interaction DD-LZ2.The new magic number structure N=32,34 and the neutron dropline positions of O and Ne isotope chains are reproduced.Applications of new effective nuclear force The new effective interaction DD-LZ2 can reproduce the new magic number structure N=32 and 34 in the Ca isotope chain by comparing with the experimental data.By reducing the Dirac equation to schrodinger-like equation,the effect of?-meson tensor coupling on spin-orbit splitting is analyzed,and the self-consistent formation mechanism of the new magic number structure N=32 and 34 is given.Meanwhile,by analyzing the two proton gap systematicness of N=82 and 126 neutron chains,it is proved that the new effective nuclear forces DD-LZ1 and DD-LZ2 have successfully eliminated the pseudo-shell structure in the original RMF calculations.The boundary of nuclide map is a hot issue of both experimental and theoretical concern,in which the position of neutron dripline is related to some basic problems of nuclear physics,such as manybody correlation in the isospin limit and nuclear mass.Therefore,the determination of the neutron dripline position provides a strict test for the nuclear mass formula,the prediction of the microscopic mass given by the large-scale shell model,the nuclear density functional theory and the first-principle calculation.In this paper,we use the new effective nuclear force DD-LZ2to reconstruct the positions of the two neutron dripline of O and Ne isotope chains.By analyzing the structure of²⁴O,it is found that the spin-orbit splitting of the neutron?1d state is the key physics to determine the position of the neutron dripline in O isotopes,and the?-meson tensor coupling introduced in DD-LZ2 significantly strengthens the splitting of the?1d state.Due to the neutron halo structure in³⁴Ne,the neutron dripline position of Ne isotope is closely related to deformation,pairing correlation and continuous state effects.The shell effect and the weak binding mechanism related to the novel phenomena are the key physics affecting the position of the neutron dripline.The study of dripline position not only tests the theoretical reliability,but also deepens our understanding of unstable nuclear properties and effective nuclear force,which has important reference value for theoretical and experimental development.