A Separable Pairing Force for Relativistic Quasiparticle Random Phase Approximation

TL;DR

This paper introduces a simple separable pairing force that accurately reproduces pairing properties in nuclear matter and finite nuclei, and successfully describes excited states in relativistic quasiparticle calculations.

Contribution

The paper develops and validates a separable pairing force for use in relativistic quasiparticle RPA, matching Gogny force results in nuclear structure calculations.

Findings

Successfully reproduces pairing properties of Gogny force in nuclear matter

Accurately describes excited states in Sn isotopes and isotones

Converges well with various cutoff parameters in RQRPA

Abstract

We have introduced a separable pairing force, which was adjusted to reproduce the pairing properties of the Gogny force in nuclear matter. This separable pairing force is able to describe in relativistic Hartree-Bogoliubov (RHB) calculations the pairing properties in the ground state of finite nuclei on almost the same footing as the original Gogny interaction. In this work we investigate excited states using the Relativistic Quasiparticle Random Phase Approximation (RQRPA) with the same separable pairing force. For consistency the Goldstone modes and the convergence with various cutoff parameters in this version of RQRPA are studied. The first excited $2^+$ states for the chain of Sn-isotopes with Z=50 and the chain of isotones with N=82 isotones are calculated in RQRPA together with the $3^-$ states of Sn-isotopes. Comparing with experimental data and with the results of original Gogny force we find that this simple separable pairing interaction is very successful in depicting the pairing properties of vibrational excitations.