Repulsion and absorption of the Σ -nucleus potential for Σ−−He5 in the Li6(π−,K+) reaction

We study phenomenologically inclusive spectra of the $^{6}\mathrm{Li}({\ensuremath{\pi}}^{\ensuremath{-}},\phantom{\rule{0.16em}{0ex}}{K}^{+})$ reaction at 1.2 GeV/$c$ within a distorted-wave impulse approximation with the optimal Fermi-averaging ${\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}{K}^{+}{\mathrm{\ensuremath{\Sigma}}}^{\ensuremath{-}}\phantom{\rule{0.16em}{0ex}}t$ matrix. We attempt to clarify the property of a $\mathrm{\ensuremath{\Sigma}}$-nucleus potential for ${\mathrm{\ensuremath{\Sigma}}}^{\ensuremath{-}}\text{\ensuremath{-}}^{5}\mathrm{He}$ by comparing the calculated spectra with the data of the J-PARC E10 experiment. The result shows that the repulsive and absorptive components of the ${\mathrm{\ensuremath{\Sigma}}}^{\ensuremath{-}}\text{\ensuremath{-}}^{5}\mathrm{He}$ potential provide the ability to explain the data of the continuum spectra in $\mathrm{\ensuremath{\Sigma}}$ and $\mathrm{\ensuremath{\Lambda}}$ regions; the strengths of ${V}_{\mathrm{\ensuremath{\Sigma}}}=+30\ifmmode\pm\else\textpm\fi{}10$ MeV and ${W}_{\mathrm{\ensuremath{\Sigma}}}=\ensuremath{-}26\ifmmode\pm\else\textpm\fi{}2$ MeV are favored within the Woods-Saxon potential, consistent with analyses for heavier nuclei. Effects of the size and potential range for ${\mathrm{\ensuremath{\Sigma}}}^{\ensuremath{-}}\text{\ensuremath{-}}^{5}\mathrm{He}$ in the neutron excess of $(N\ensuremath{-}Z)/(N+Z)=$ 0.2 are also discussed.