Optimal pair density functional for description of nuclei with large neutron excess

TL;DR

This paper develops an improved energy density functional with enhanced isovector density dependence to better describe pairing properties in nuclei with large neutron excess, aiming for a universal nuclear model.

Contribution

It introduces a new pair density functional with both linear and quadratic isovector density terms, optimized for nuclei far from stability.

Findings

Inclusion of isovector density dependence improves pairing gap predictions.

Different Skyrme forces yield similar pairing gaps when using the optimal pair-DF.

The approach accounts for effects of effective masses in particle-hole and particle-particle channels.

Abstract

Toward a universal description of pairing properties in nuclei far from stability, we extend the energy density functional by enriching the isovector density dependence in the particle-particle channel (pair density functional, pair-DF). We emphasize the necessity of both the linear and quadratic isovector density terms. The parameters are optimized by the Hartree-Fock-Bogoliubov calculation for 156 nuclei of the mass number A=118-196 and the asymmetry parameter (N-Z)/A<0.25. We clarify that the pair-DF should include the isovector density dependence in order to take into account the effect of the isoscalar and isovector effective masses in the particle-hole channel consistently. The different Skyrme forces can give the small difference in the pairing gaps toward the neutron drip line, if the optimal pair-DF consistent with the particle-hole channel is employed.