Effective interactions in the sd shell

TL;DR

This study evaluates microscopic effective interactions in the sd shell derived from modern nucleon-nucleon potentials, showing improvements with Daejeon16 and proposing modifications for better experimental agreement.

Contribution

It introduces a detailed comparison of effective interactions from different potentials and proposes monopole modifications to enhance agreement with experimental data.

Findings

Daejeon16-based interactions show noticeable improvement.

Proposed monopole modifications improve experimental agreement.

Spin-tensor decomposition provides insights into interaction structures.

Abstract

We perform a quantitative study of the microscopic effective shell-model interactions in the valence sd shell, obtained from modern nucleon-nucleon potentials, chiral N3LO, JISP16 and Daejeon16, using No-Core Shell-Model wave functions and the Okubo-Lee-Suzuki transformation. We investigate the monopole properties of those interactions in comparison with the phenomenological universal sd-shell interaction, USDB. Theoretical binding energies and low-energy spectra of O isotopes and of selected sd-shell nuclei, are presented. We conclude that there is a noticeable improvement in the quality of the effective interaction when it is derived from the Daejeon16 potential. We show that its proton-neutron centroids are consistent with those from USDB. We then propose monopole modifications of the Daejeon16 centroids in order to provide an adjusted interaction yielding significantly improved agreement with the experiment. A spin-tensor decomposition of two-body effective interactions is applied in order to extract more information on the structure of the centroids and to understand the reason for deficiencies arising from our current theoretical approximations. The issue of the possible role of the three-nucleon forces is addressed.