Strength of the $\Sigma$ Single-Particle Potential in Nuclei From   Semiclassical Distorted Wave Model Analysis of $(\pi^-,K^+)$ Inclusive   Spectrum
  Semiclassical distorted wave model is developed to describe $(\pi^-,K^+)$ inclusive spectra related to $\Sigma^-$-formation measured at KEK with $p_\pi =1.2$ GeV/c. The shape and magnitude of the spectrum on $^{28}$Si target are satisfactorily reproduced by a repulsive $\Sigma$-nucleus potential, the strength of which is of the order of 30$\sim$50 MeV. This strength is not so strong as more than 100 MeV suggested by the estimation presented in the report of the experiment. 
M. Kohno, Y. Fujiwara, Y. Watanabe, K. Ogata and M. Kawai