Realistic shell-model calculations for p-shell nuclei including contributions of a chiral three-body force

TL;DR

This paper advances shell-model calculations for p-shell nuclei by incorporating chiral three-body forces, improving the accuracy of ground-state energy predictions and benchmarking against ab initio methods.

Contribution

It introduces a novel method to include three-body forces derived from chiral perturbation theory into shell-model calculations for p-shell nuclei.

Findings

Results are consistent with ab initio no-core shell-model calculations.

Inclusion of three-body forces improves ground-state energy estimates.

Method shows promise for application to heavier nuclear systems.

Abstract

In this paper we present an evolution of our derivation of the shell-model effective Hamiltonian, namely introducing effects of three-body contributions. More precisely, we consider a three-body potential at next-to-next-to-leading order in chiral perturbation theory, and the induced three-body forces that arise from many-body correlations among valence nucleons. The first one is included, in the derivation of the effective Hamiltonian for one- and two-valence nucleon-systems, at first order in the many-body perturbation theory. Namely, we include only the three-body interaction between one or two valence nucleons and those belonging to the core. For nuclei with more than two valence particles, both induced - turned on by the two-body potential - and genuine three-body forces come into play. Since it is difficult to perform shell-model calculations with three-body forces, these contributions are estimated for the ground-state energy only. In order to establish the reliability of our approximations, we focus attention on nuclei belonging to the p shell, aiming to benchmark our calculations against those performed with the ab initio no-core shell-model. The obtained results are satisfactory, and pave the way to the application of our approach to nuclear systems with heavier masses.