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

Theoretical ab initio studies of resonances in the unbound ${}^7\mathrm{H}\mathrm{e}$ 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 $n-{}^6\mathrm{H}\mathrm{e}$ and $n-{}^6\mathrm{H}{\mathrm{e}}^{\ast }$ with ${}^6\mathrm{H}\mathrm{e}$ respectively in the ground and excited $2^{+}$ states as well as for the four-body democratic decay channel ${}^4\mathrm{H}\mathrm{e}+n+n+n$. The resonant energies and widths areobtained by numerical location of the $S$-matrix poles. We describe all experimentally known ${}^7\mathrm{H}\mathrm{e}$ resonances and suggest an interpretation of an observed wide resonance of unknown spin-parity.