Shell model study of the pairing correlations

TL;DR

This study uses the spherical shell model to analyze how pairing correlations in nuclei vary with temperature and angular momentum, revealing similarities across different nuclear types and effects of neutron-proton asymmetry.

Contribution

It provides a systematic shell model analysis of pairing correlations across various nuclear systems, including asymmetric cases, and offers a simplified model explanation.

Findings

Pairing correlations are similar in even-even and odd-mass nuclei.

Angular momentum I=0 state in odd-odd N=Z nuclei is an isospin t=1 neutron-proton pair.

Pair correlations are significantly reduced in N=Z+4 asymmetric nuclei.

Abstract

A systematic study of the pairing correlations as a function of temperature and angular momentum has been performed in the sd-shell region using the spherical shell model approach. The pairing correlations have been derived for even-even, even-odd and odd-odd systems near N=Z and also for the asymmetric case of N=Z+4. The results indicate that the pairing content and the behavior of pair correlations is similar in even-even and odd-mass nuclei. For odd-odd N=Z system, angular momentum I=0 state is an isospin, t=1 neutron-proton paired configuration. Further, these t=1 correlations are shown to be dramatically reduced for the asymmetric case of N=Z+4. The shell model results obtained are qualitatively explained within a simplified degenerate model.