Alpha-like quartet condensation and isovector pairing correlations in N=Z nuclei

TL;DR

This paper introduces a quartet condensation model (QCM) that accurately describes isovector pairing correlations in N=Z nuclei, highlighting the quartet nature of these correlations and demonstrating high precision compared to exact shell model results.

Contribution

The paper presents a new quartet condensation model that effectively captures isovector pairing correlations in self-conjugate nuclei, with high accuracy validated against shell model calculations.

Findings

QCM reproduces pairing energies with errors below 1%.

Quartet correlations are dominant in isovector pairing in N=Z nuclei.

QCM is effective for both spherical and deformed single-particle states.

Abstract

We propose a simple quartet condensation model (QCM) which describes with very high accuracy the isovector pairing correlations in self-conjugate nuclei. The quartets have an alpha-like structure and are formed by collective isovector pairs. The accuracy of the QCM is tested for N=Z nuclei for which exact shell model diagonalizations can be performed. The calculations are done with two isovector pairing forces, one extracted from standard shell model interactions and the other of seniority type, acting, respectively, upon spherical and axially-deformed single-particle states. It is shown that for all calculated nuclei the QCM gives very accurate values for the pairing correlations energies, with errors which do not exceed 1%. These results show clearly that the correlations induced by the isovector pairing in self-conjugate nuclei are of quartet type and also indicate that QCM is the proper tool to calculate the isovector proton-neutron correlations in mean field pairing models.