An Alternative Understanding of Mass Formulas in Terms of Nuclear Structure

A typical form of mass formula is re-explained in terms of nuclear structure. For $ N \approx Z $ nuclei, we propose to start with the shell model pictureand to consider the T=0 $2n-2p$ ($\alpha$-like) correlations as the fundamentalconcept, instead of the symmetry energy. Subsequently, the symmetry energy is described on the basis of the$\alpha$-like superfluidity caused by the T=0 $2n-2p$ correlations, in parallelwith the pairing energy described on the basis of the pairing superfluidity.This re-explanation gives useful insight for understanding the nuclear massformula. The origin of the Wigner energy is also explained in an interactingboson model for the Cooper pairs in the $\alpha$-like superfluid vacuum. Addinga correction term due to the T=0 $2n-2p$ correlations, which determines the T=0base level for nuclear masses, can improve the mass formulas in practice.Comment: to be published in Prog. Theor. Phys. Vol. 113, No.