Resonances of $A=4$ $T=1$ isospin triplet states within the \textit{ab initio} no-core Gamow shell model

TL;DR

This paper presents ab initio many-body calculations of the broad resonance structures of the A=4 T=1 isospin triplet nuclei, providing insights into their resonance properties and isospin symmetry breaking effects.

Contribution

It introduces a novel ab initio no-core Gamow shell model approach to study broad resonances in A=4 nuclei, aligning theoretical results with experimental observations.

Findings

Confirmed broad resonance nature of H, Li, and excited He

First excited state nearly degenerate with ground state in mirror nuclei

Observed isospin symmetry breaking effects in the triplet

Abstract

The $A=4$ nuclei, i.e., $^4$H, $^4$He and $^4$Li, establish an interesting isospin $T=1$ isobaric system. $^4$H and $^4$Li are unbound broad resonances, whereas $^4$He is deeply bound in its ground state but unbound in all its excited states. The present situation is that experiments so far have not given consistent data on the resonances. Few-body calculations have well studied the scatterings of the $4N$ systems. In the present work, we provide many-body calculations of the broad resonance structures, in an \textit{ab initio} framework with modern realistic interactions. It occurs that, indeed, $^4$H, $^4$Li and excited $^4$He are broad resonances, which is in accordance with experimental observations. The calculations also show that the first $1^-$ excited state almost degenerates with the $2^-$ ground state in the pair of mirror isobars of $^4$H and $^4$Li, which may suggest that the experimental data on energy and width are the mixture of the ground state and the first excited state. The $T = 1$ isospin triplet formed with an excited state of $^4$He and ground states of $^4$H and $^4$Li is studied, focusing on the effect of isospin symmetry breaking.