Shell-model interactions from chiral effective field theory

TL;DR

This paper develops shell-model Hamiltonians derived from chiral effective field theory, incorporating symmetry principles and in-medium effects, to improve predictions of nuclear structure, especially for neutron-rich isotopes.

Contribution

It introduces a novel method to construct valence-space Hamiltonians from chiral EFT, including center-of-mass operators and uncertainty estimates.

Findings

Achieved root-mean-square deviations of 1.8 MeV at leading order and 0.5 MeV at next-to-leading order.

Fitted low-energy constants to 441 nuclear states in the sd shell.

Demonstrated promising predictions for neutron-rich isotopes beyond the fitted data.

Abstract

We construct valence-space Hamiltonians for use in shell-model calculations, where the residual two-body interaction is based on symmetry principles and the low-momentum expansion from chiral effective field theory. In addition to the usual free-space contact interactions, we also include novel center-of-mass--dependent operators that arise due to the Galilean invariance breaking by in-medium effects. We fitted the low-energy constants to 441 ground- and excited-state energies in the sd shell and obtained a root-mean-square derivation of 1.8 MeV at leading order and of 0.5 MeV at next-to-leading order, with natural low-energy constants in all cases. The developed chiral shell-model interactions enable order-by-order uncertainty estimates and show promising predictions for neutron-rich isotopes beyond the fitted data set.