SS-HORSE extension of the no-core shell model: Application to resonances in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>He</mml:mi><mml:mprescripts/><mml:none/><mml:mn>7</mml:mn></mml:mmultiscripts></mml:math>
I. A. Mazur, Ik Jae Shin, Y. Kim, A. I. Mazur, A. M. Shirokov, Pieter Maris, James P. Vary
Abstract
Theoretical ab initio studies of resonances in the unbound $^{7}\mathrm{He}$ 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 $n+^{6}\mathrm{He}$ and $n+^{6}\mathrm{He}^{*}$ with $^{6}\mathrm{He}$ respectively in the ground and excited ${2}^{+}$ states as well as for the four-body democratic decay channel $^{4}\mathrm{He}+n+n+n$. The resonant energies and widths are obtained by numerical location of the $S$-matrix poles. We describe all experimentally known $^{7}\mathrm{He}$ resonances and suggest an interpretation of an observed wide resonance of unknown spin-parity.