Towards a high-precision nuclear mass table with deformed relativistic Hartree-Bogoliubov theory in continuum

Abstract

<p indent=0mm>As one of the most fundamental quantities for the atomic nucleus, nuclear mass is very important for various fields such as nuclear physics, particle physics, astrophysics, and cosmology. It is the key to understand the interaction between nucleons, the evolution of shell structures, and the location of drip lines. It also provides the basic information for nuclear reactions and the necessary inputs to study the origin of elements. Although dramatic progress for the mass measurement of short-lived nuclei has been made, the masses of most exotic nuclei far away from the stability valley still rely on the predictions by nuclear models in the foreseeable future. The popular nuclear mass models are briefly reviewed, including the finite-range droplet model (FRDM), Weizsäcker-Skyrme 4 (WS4) model, and HFB-27* model, etc. The efforts in applying the machine learning to improve the nuclear mass predictions are introduced. The relativistic density functional theory has been proved to be a powerful theory in nuclear physics by its successful description of many nuclear phenomena. The relativistic density functional theory has many attractive advantages, such as the automatic inclusion of nucleonic spin degree of freedom, explaining naturally the pseudospin symmetry in the nucleon spectrum and the spin symmetry in antinucleon spectrum, and the natural inclusion of nuclear magnetism, which plays an important role in nuclear magnetic moments and nuclear rotations. The relativistic density functional PC-PK1 has turned out to be very successful in providing good descriptions of the isospin dependence of the binding energy along either the isotopic or the isotonic chain. The relativistic continuum Hartree-Bogoliubov (RCHB) theory, which takes into account self-consistently the pairing correlations and continuum effects, is very suitable to describe the exotic nuclei. The first nuclear mass table including the continuum effects based on the RCHB theory with PC-PK1 has been constructed, predicting 9035 bound nuclei with 8≤<italic>Z</italic>≤120, which remarkably extends the existing nuclear landscape. The deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) was developed for exotic nuclei including deformation and continuum effects, with the deformed relativistic Hartree-Bogoliubov equations solved in a Dirac Woods-Saxon basis. The success of the DRHBc theory has been demonstrated in predicting an interesting shape decoupling between the core and the halo in ⁴⁴Mg and ⁴²Mg, resolving the puzzles concerning the radius and configuration of valence neutrons in ²²C, and studying particles in the classically forbidden regions for magnesium isotopes. A DRHBc Mass Table Collaboration, presently consisting of sixteen institutions from China and South Korea, which aims to construct the first relativistic nuclear mass table including simultaneously the deformation and continuum effects based on the DRHBc theory and density functional PC-PK1, has been founded. The recent progress in the construction of the DRHBc mass table for even-even nuclei is introduced. By taking even-even Nd isotopes as examples, the improvement for the description of the nuclear masses by deformation effects is shown in comparison with the RCHB calculations. The investigation of the possible exotic structure on the neutron-rich side and the possible proton radioactivity beyond the proton drip line for Nd isotopes is discussed. Possible topics to be investigated based on the DRHBc mass table are proposed.