The A(K(stop)(-), pi(+/-)Sigma(-/+))A ' reaction on p-shell nuclei

Abstract This Letter is concerned with the study of the K stop − A → π ± Σ ∓ A ′ reaction in p-shell nuclei, i.e., 6,7 Li, 9 Be, 13 C and 16 O. The π ± Σ ∓ / K stop − 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 DA Φ NE ϕ -factory (LNF-INFN, Italy).