An improved nuclear mass formula, N. Wang, Department of Physics, Guangxi Normal University, China − We propose a semi-empirical nuclear mass formula based on the macroscopic-microscopic method in which the isospin and mass dependence of model parameters are investigated with the Skyrme energy density functional. The number of model parameters is considerably reduced compared with the finite range droplet model. The rms deviation from 2149 known nuclear masses is significantly reduced to 336 keV, even lower than that achieved with the best of the Duflo-Zuker models. The new magic number N=16 in light neutron-rich nuclei and the shape coexistence phenomena for some nuclei have been examined with the model. The shell corrections, the deformations of nuclei, the neutron and proton drip lines, and the shell gaps are also investigated to test the model. The alpha-decay energies of super-heavy nuclei, the Garvey-Kelson relations, and the isobaric multiplet mass equation (IMME) can be reproduced remarkably well with the model, and the predictive power of the mass model is good. The mirror nuclei constraint and the Wiger effect related to the isospin symmetry in nuclear physics plays a key role in the improvement of mass formula. With a systematic study of 17 global nuclear mass models, we find that the quadratic form of the IMME is closely related to the accuracy of nuclear mass calculations when the Garvey-Kelson relations are reproduced reasonably well. Fulfilling both the IMME and the Garvey-Kelson relations seem to be two necessary conditions for improving the quality of the model prediction. The predicted central position of the superheavy island could lie around N=176-178 and Z=116-120 according to the shell corrections of nuclei.

[1] N. Wang, M. Liu and X. Wu, Phys. Rev. C 81, 044322 (2010).

[2] N. Wang, Z. Liang, M. Liu and X. Wu, Phys. Rev. C 82, 044304 (2010).

[3] M. Liu, N. Wang, Y. Deng and X. Wu, Phys. Rev. C 84, 014333 (2011).