Direct andY1*-Resonant Production ofΛ0andπ−andΣ−Λ0Conversion FollowingK¯-Meson Nuclear Absorption. Final-State Interactions in theK¯+He4→π−+Λ0+He3Reaction

In the reaction of $\overline{K}$-meson nuclear absorption, three fundamental processes are considered: a direct (nonresonant) $\overline{K}+N\to {\pi }^{-}+{\Lambda }^0$ reaction, the same reaction with the ${Y_1}^{*}$ resonance formation in the intermediate state, and the reaction with a $\Sigma$ production in the first stage and its subsequent conversion into a ${\Lambda }^0$ in a successive collision with another nucleon. The "zero-range" impulseapproximation is assumed. The initial $\overline{K}$ state is an $\mathrm{nS}$ or an $\mathrm{mP}$ Bohr mesoatomic orbit. Several forms of the ${\Lambda }^0$-nucleus final-state interaction are considered. For the case of the $\overline{K}+{}_{}{}^4{}_{}{}^{}\mathrm{He}\to {\pi }^{-}+{\Lambda }^0+{}_{}{}^3{}_{}{}^{}\mathrm{He}$ reaction the recoiling-${}_{}{}^3{}_{}{}^{}\mathrm{He}$ momentum distribution, the pion momentum distribution, and the ${\pi }^{-}+{\Lambda }^0$ ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ angular distribution are analyzed. It turns out that in order to explain the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ momentum distribution no elastic scattering distortion of the ${\Lambda }^0$-${}_{}{}^3{}_{}{}^{}\mathrm{He}$ wave is sufficient, and one has to introduce the $\Sigma -{\Lambda }^0$ conversion amplitude, which is most important at high ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-momenta, and which also improves our pion momentum distribution.