SS-HORSE Extension of the No-Core Shell Model: Application to Resonances in $^7{\mathrm He}$

TL;DR

This paper uses ab initio no-core shell model calculations combined with the SS-HORSE method to analyze resonances in unbound ${}^7He$, providing detailed resonance energies and widths, and interpreting experimental data.

Contribution

It introduces the application of the SS-HORSE method within the no-core shell model framework to study ${}^7He$ resonances, including unbound states and decay channels.

Findings

Successfully describes all known ${}^7He$ resonances.

Provides resonance energies and widths consistent with experimental data.

Offers interpretation of a wide resonance with unknown spin-parity.

Abstract

Theoretical ab initio studies of resonances in the unbound ${\rm^{7}He}$ nucleus are presented. We perform no-core shell model calculations with $NN$ interactions Daejeon16 and JISP16 and utilize the SS-HORSE method to calculate the $S$ matrix for two-body channels $n{-}{\rm^{6}He}$ and $n{-}{\rm^{6}He^{*}}$ with ${\rm^{6}He}$ respectively in the ground and excited $2^{+}$ states as well as for the four-body democratic decay channel ${{\rm^{4}He}+n+n+n}$. The resonant energies and widths areobtained by numerical location of the $S$-matrix poles. We describe all experimentally known ${\rm^{7}He}$ resonances and suggest an interpretation of an observed wide resonance of unknown spin-parity.