Robust ab initio prediction of nuclear electric quadrupole observables by scaling to the charge radius

TL;DR

This paper introduces a method to improve ab initio predictions of nuclear electric quadrupole observables by scaling to the charge radius, addressing convergence issues in nuclear structure calculations.

Contribution

The authors demonstrate a correlation between E2 observables and charge radius convergence, enabling more accurate predictions by calibration to experimental charge radius data.

Findings

Robust predictions for E2 transition strengths and quadrupole moments in p-shell nuclei.

Correlation between convergence patterns of E2 observables and charge radius.

Calibration to charge radius improves ab initio E2 predictions.

Abstract

Meaningful predictions for electric quadrupole (E2) observables from ab initio nuclear theory are necessary, if the ab initio description of collective correlations is to be confronted with experiment, as well as to provide predictive power for unknown E2 observables. However, converged results for E2 observables are notoriously challenging to obtain in ab initio no-core configuration interaction (NCCI) approaches. Matrix elements of the E2 operator are sensitive to the large-distance tails of the nuclear wave function, which converge slowly in an oscillator basis expansion. Similar convergence challenges beset ab initio prediction of the nuclear charge radius. We demonstrate that the convergence patterns of the E2 and radius observables are strongly correlated, and that meaningful predictions for the absolute scale of E2 observables may be made by calibrating to the experimentally-known ground-state charge radius. We illustrate by providing robust ab initio predictions for several E2 transition strengths and quadrupole moments in p-shell nuclei, in cases where experimental results are available for comparison.