Sensitivities and correlations of nuclear structure observables emerging from chiral interactions

TL;DR

This study uses chiral effective field theory interactions in ab initio calculations to analyze nuclear structure observables, revealing sensitivities, correlations, and ways to improve predictive accuracy for selected p-shell nuclei.

Contribution

It systematically assesses the impact of different chiral interactions on nuclear observables and uncovers robust correlations that enhance predictive capabilities beyond direct calculations.

Findings

Uncertainty bands generally match experimental excitation energies.

Identified correlations among electromagnetic observables, especially E2 and M1.

Predicted the quadrupole moment of C-12's first 2+ state with improved accuracy.

Abstract

Starting from a set of different two- and three-nucleon interactions from chiral effective field theory, we use the importance-truncated no-core shell model for ab initio calculations of excitation energies as well as electric quadrupole (E2) and magnetic dipole (M1) moments and transition strengths for selected p-shell nuclei. We explore the sensitivity of the excitation energies to the chiral interactions as a first step towards and systematic uncertainty propagation from chiral inputs to nuclear structure observables. The uncertainty band spanned by the different chiral interactions is typically in agreement with experimental excitation energies, but we also identify observables with notable discrepancies beyond the theoretical uncertainty that reveal insufficiencies in the chiral interactions. For electromagnetic observables we identify correlations among pairs of E2 or M1 observables based on the ab initio calculations for the different interactions. We find extremely robust correlations for E2 observables and illustrate how these correlations can be used to predict one observable based on an experimental datum for the second observable. In this way we circumvent convergence issues and arrive at far more accurate results than any direct ab initio calculation. A prime example for this approach is the quadrupole moment of the first 2^+ state in C-12, which is predicted with an drastically improved accuracy.