Coulomb-assisted Σ−-nucleus bound states in the (K−,π+) reaction

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 28Si, 58Ni, and 208Pb targets at incident K− lab momenta pK=400–800MeV/c. The results show that the near-recoilless (K−,π+) reaction on the 58Ni 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.