Discrimination of $\Sigma$-nucleus potentials in the angular   distribution of elastic scattering of $\Sigma^-$ hyperons from nuclei
  We theoretically investigate the elastic scattering of 50-MeV $\Sigma^-$ hyperons from $^{28}$Si and $^{208}$Pb in order to clarify the radial distribution of $\Sigma$-nucleus (optical) potentials. The angular distributions of differential cross sections are calculated using several potentials that can explain experimental data of the $\Sigma^-$ atomic X-ray and ($\pi^-$, $K^+$) reaction spectra simultaneously. The magnitude and oscillation pattern of the angular distributions are understood by the use of nearside/farside decompositions of their scattering amplitudes. It is shown that the resultant angular distributions can considerably discriminate among the radial distributions of the potentials that have a repulsion inside the nuclear surface and an attraction outside the nucleus with a sizable absorption. 
Toru Harada, and Yoshiharu Hirabayashi
nucl-th