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

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 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.