Semi-microscopic model of pairing in nuclei

TL;DR

This paper introduces a semi-microscopic model for nucleon pairing in nuclei, combining ab initio calculations with phenomenological adjustments, validated across various semi-magic nuclei.

Contribution

It develops a semi-microscopic approach that integrates first-principles effective interactions with a universal phenomenological parameter for nuclear pairing.

Findings

Model successfully describes pairing in semi-magic nuclei

Effective interaction derived from first principles

Phenomenological parameter accounts for many-body and mass effects

Abstract

A semi-microscopic model for nucleon pairing in nuclei is presented starting from the ab intio BCS gap equation with Argonne v18 force and the self-consistent Energy Density Functional Method basis characterized with the bare nucleon mass. The BCS theory is formulated in terms of the model space S0 with the effective pairing interaction calculated from the first principles in the subsidiary space S0. This effective interaction is supplemented with a small phenomenological addendum containing one phenomenological parameter universal for all medium and heavy atomic nuclei. We consider the latter as a phenomenological way to take into account both the many-body corrections to the BCS theory and the effective mass effects. For protons, the Coulomb interaction is introduced directly. Calculations made for several isotopic and isotonic chains of semi-magic nuclei confirm the validity of the model. The role of the self-consistent basis is stressed.