Radii and binding energies in oxygen isotopes: a puzzle for nuclear forces

TL;DR

This paper systematically compares experimental and theoretical nuclear radii and binding energies in oxygen isotopes, revealing that current ab initio models struggle to accurately predict radii, especially in neutron-rich isotopes.

Contribution

It introduces a novel version of nuclear forces that improves the simultaneous description of radii and binding energies in stable isotopes, highlighting ongoing challenges in modeling neutron-rich nuclei.

Findings

Ab initio calculations reproduce binding energies well.

Conventional nuclear interactions fail to accurately predict radii.

New nuclear force models improve predictions for stable isotopes but not for neutron-rich ones.

Abstract

We present a systematic study of both nuclear radii and binding energies in (even) oxygen isotopes from the valley of stability to the neutron drip line. Both charge and matter radii are compared to state-of-the-art {\it ab initio} calculations along with binding energy systematics. Experimental matter radii are obtained through a complete evaluation of the available elastic proton scattering data of oxygen isotopes. We show that, in spite of a good reproduction of binding energies, {\it ab initio} calculations with conventional nuclear interactions derived within chiral effective field theory fail to provide a realistic description of charge and matter radii. A novel version of two- and three-nucleon forces leads to considerable improvement of the simultaneous description of the three observables for stable isotopes, but shows deficiencies for the most neutron-rich systems. Thus, crucial challenges related to the development of nuclear interactions remain.