Parameter adjustment of nuclear leading-order local pairing energy density functionals

TL;DR

This paper benchmarks a protocol for adjusting local pairing energy density functionals in nuclear physics, demonstrating its effectiveness in reproducing nuclear properties and discussing the limitations and impacts of various modeling choices.

Contribution

It introduces a systematic protocol for parameter adjustment of LO pairing EDFs based on infinite nuclear matter calculations, improving predictions of nuclear masses and moments of inertia.

Findings

The protocol yields consistent results for nuclear masses and moments of inertia.

Adjusting pairing gaps alone may not fully characterize the pairing interaction.

Certain parameter regions can lead to unphysical Bose-Einstein condensate transitions.

Abstract

(See paper for full abstract) This study reports on the benchmarking of a protocol for the adjustment of the parameters of a local leading-order (LO) T=1 (like-particle) pairing EDF that consists in adjusting the density-dependence of the 1S0 pairing gap at the chemical potential in infinite nuclear matter (INM). When using a suitably chosen reference calculation, this protocol leads to consistent results for the odd-even staggering of masses of spherical and heavy deformed nuclei and also for the rotational moments of inertia calculated in a time-reversal-breaking cranked HFB approach. The implementation of the HFB solver for infinite matter at arbitrary isospin asymmetry used for this study is sketched in appendices. Additional points that are discussed concern (i) the illustration that the gaps at the chemical potential are not necessarily sufficient to completely characterise the pairing interaction in infinite matter, and that adjusting LO pairing EDF to reproduce gaps obtained from finite-range pairing interactions in HFB or from more microscopic calculations can lead to unrealistic predictions for finite nuclei; (ii) the finding that some regions of the parameter space for the density dependence of the T=1 LO pairing EDF lead to a spurious transition to a Bose-Einstein condensate of di-nucleons in spite of producing realistic pairing correlations for well-bound nuclei; (iii) the correlation between effective mass and the parameters of the LO pairing EDF that control the form factor of the density dependence when reproducing pairing gaps in infinite matter, (iv) the significant impact on the odd-even staggering of masses made by either including or not the spin-gradient terms in the particle-hole part of the Skyrme EDF; (v) the sizeable impact of keeping or not the contribution from the density-dependent LO pairing EDF to the mean fields on the odd-even staggering of radii.