Spin and pseudospin symmetries in the antinucleon spectrum of nuclei

TL;DR

This paper investigates spin and pseudospin symmetries in nucleon and antinucleon spectra within a relativistic mean-field framework, revealing that spin symmetry is perturbative and nearly exact for antinucleons, while pseudospin symmetry is dynamical and less precise.

Contribution

It provides a detailed analysis of the nature of spin and pseudospin symmetries in nucleon and antinucleon spectra using scalar and vector Woods-Saxon potentials, highlighting their perturbative or dynamical character.

Findings

Spin symmetry is perturbative and nearly exact for antinucleons.

Pseudospin symmetry is dynamical and better realized for nucleons.

Spin-orbit and pseudospin-orbit couplings support the symmetry characterizations.

Abstract

Spin and pseudospin symmetries in the spectra of nucleons and antinucleons are studied in a relativistic mean-field theory with scalar and vector Woods-Saxon potentials, in which the strength of the latter is allowed to change. We observe that, for nucleons and antinucleons, the spin symmetry is of perturbative nature and it is almost an exact symmetry in the physical region for antinucleons. The opposite situation is found in the pseudospin symmetry case, which is better realized for nucleons than for antinucleons, but is of dynamical nature and cannot be viewed in a perturbative way both for nucleons and antinucleons. This is shown by computing the spin-orbit and pseudospin-orbit couplings for selected spin and pseudospin partners in both spectra.