Strangeness modes in nuclei tested by antineutrinos

The production of negative strangeness in reactions of inelastic antineutrino scattering on a nucleus provides information on the modification of strange degrees of freedom in nuclear matter. We calculate cross sections of the reaction channels ν̅ _e(μ)→e⁺(μ⁺)+K^- and ν̅ _e(μ)+p⃗Λ+e⁺(μ⁺) and investigate their sensitivity to the medium effects. In particular, we consider effects induced by the presence of a low-energy excitation mode in the K^- spectrum, associated with correlated Λ-particle and proton-hole states, and by renormalization of the weak interaction in medium. In order to avoid double counting, various contributions to antineutrino scattering are classified with the help of the optical theorem, formulated within the nonequilibrium Green’s function technique.