The A(Kstop−,π±Σ∓)A′ reaction on p-shell nuclei

This Letter is concerned with the study of the Kstop−A→π±Σ∓A′ reaction in p-shell nuclei, i.e., 6,7Li, 9Be, 13C and 16O. The π±Σ∓/Kstop− emission rates are reported as a function of A. These rates are discussed in comparison with previous findings. The ratio π−Σ+/π+Σ− in p-shell nuclei is found to depart largely from that on hydrogen, which provides support for large in-medium effects possibly generated by the sub-threshold Λ(1405). The continuum momentum spectra of prompt pions and free sigmas are also discussed as well as the π±Σ∓ missing mass behavior and the link with the reaction mechanism. The apparatus used for the investigation is the FINUDA spectrometer operating at the DAΦNEϕ-factory (LNF-INFN, Italy).