Non-empirical pairing energy density functional. First order in the nuclear plus Coulomb two-body interaction

TL;DR

This paper demonstrates that a non-empirical pairing functional derived at lowest order in the two-nucleon interaction, including Coulomb effects, accurately reproduces experimental pairing gaps in semi-magic nuclei, suggesting missing effects are sub-leading.

Contribution

The study introduces a non-empirical pairing energy density functional based on the lowest order two-nucleon interaction, including Coulomb, showing good agreement with experimental data.

Findings

Neutron and proton pairing gaps closely match experimental data.

Including Coulomb reduces proton pairing gaps by up to 40%.

Higher-order effects are sub-leading for pairing gap generation.

Abstract

We perform systematic calculations of pairing gaps in semi-magic nuclei across the nuclear chart using the Energy Density Functional method and a {\it non-empirical} pairing functional derived, without further approximation, at lowest order in the two-nucleon vacuum interaction, including the Coulomb force. The correlated single-particle motion is accounted for by the SLy4 semi-empirical functional. Rather unexpectedly, both neutron and proton pairing gaps thus generated are systematically close to experimental data. Such a result further suggests that missing effects, i.e. higher partial-waves of the NN interaction, the NNN interaction and the coupling to collective fluctuations, provide an overall contribution that is sub-leading as for generating pairing gaps in nuclei. We find that including the Coulomb interaction is essential as it reduces proton pairing gaps by up to 40%.