Large-Angle Charge-Exchange Scattering of Pions byHe3at 200, 250, 275, and 290 MeV

Differential cross sections for the reaction ${}_{}{}^3{}_{}{}^{}\mathrm{He}$(${\pi }^{-}$,${\pi }^0$)${}_{}{}^3{}_{}{}^{}\mathrm{H}$ at energies of 200, 250, 275, and 290 MeV over the angular region $80°\lesssim {\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}\lesssim 150°$ are presented. Comparison is made with theoretical predictions based on Glauber theory and optical-potential calculations. Neither approach gives a satisfactory description of the data; in particular, the observed energy dependence is much smaller than the theoretical predictions.