Coulomb-assisted $\bmΣ^-$-nucleus bound states in the ($K^-$, $π^+$) reaction

Abstract

We study a production of Coulomb-assisted $Σ^-$-nucleus bound states by nuclear ($K^-$, $π^+$) reactions within a distorted-wave impulse approximation, so as to examine several types of the $Σ$-nucleus potentials that are consistent with the available $Σ^-$ atomic X-ray data and nuclear ($π^-$, $K^+$) data. We theoretically demonstrate the inclusive ($K^-$, $π^+$) spectra of the $Σ^-$ unstable bound states on $^{28}$Si, $^{58}$Ni, and $^{208}$Pb targets at incident $K^-$ lab momenta $p_{K}= 400\text{--}800$ MeV/c. The results show that the near-recoilless ($K^-$, $π^+$) reaction on the $^{58}$Ni target gives a clear candidate to confirm properties of the $Σ$-nucleus potentials having a repulsion inside the nuclear surface and an attraction outside the nucleus with a sizable absorption, whereas details of the repulsion of the potential at the nuclear center cannot be determined by the inclusive spectra. This is a promising attempt to extract properties of the $Σ$-nucleus potential in the nucleus at forthcoming J-PARC experiments, as a full complement to the analyses of the $Σ^-$ atomic and ($π^-$, $K^+$) data.