(π-,K+) hyperon production inclusive spectra with pπ=1.2 GeV/c measured at KEK on C12 and Si28 are analyzed by the semiclassical distorted-wave model. Single-particle (s.p.) wave functions of the target nucleus are treated using Wigner transformation. This method is able to account for the energy and angular dependences of the elementary process in nuclear medium without introducing the factorization approximation frequently employed. Calculations of the (π+,K+)Λ formation process, for which there is no free parameter because the Λ s.p. potential is known, demonstrate that the present model is useful to describe inclusive spectra. It is shown that to account for the experimental data of the Σ- formation spectra a repulsive Σ-nucleus potential is necessary whose magnitude is not so strong as around 100 MeV previously suggested.
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