Discerning nuclear pairing properties from magnetic dipole excitation

TL;DR

This study explores how magnetic dipole excitations in nuclei can reveal the nature of nuclear pairing correlations, distinguishing between spin-singlet and spin-triplet modes using advanced relativistic models.

Contribution

It introduces a method to determine nuclear pairing modes by analyzing M1 excitations within the relativistic energy-density functional framework.

Findings

M1 excitation properties are sensitive to the pairing model used.

Systematic evaluation of M1 transitions can discern pairing properties in nuclei.

The approach aligns well with experimental data to identify pairing modes.

Abstract

Pairing correlation of Cooper pair is a fundamental property of multi-fermion interacting systems. For nucleons, two modes of the Cooper-pair coupling may exist, namely of $S_{12}=0$ with $L_{12}=0$ (spin-singlet s-wave) and $S_{12}=1$ with $L_{12}=1$ (spin-triplet p-wave). In nuclear physics, it has been an open question whether the spin-singlet or spin-triplet coupling is dominant, as well as how to measure their role. We investigate a relation between the magnetic-dipole (M1) excitation of nuclei and the pairing modes within the framework of relativistic nuclear energy-density functional (RNEDF). The pairing correlations are taken into account by the relativistic Hartree-Bogoliubov (RHB) model in the ground state, and the relativistic quasi-particle random-phase approximation (RQRPA) is employed to describe M1 transitions. We have shown that M1 excitation properties display a sensitivity on the pairing model involved in the calculations. The systematic evaluation of M1 transitions together with the accurate experimental data enables us to discern the pairing properties in finite nuclei.