Scattering from nonoverlapping potentials. III. Pion elastic scattering on 4He in the 3,3 region

The $\text{π}{}^{\mathrm{?}}{}^4\text{He}$ elastic scattering in the 3,3 resonance region is discussed in the framework of the nonoverlapping potentials model. Single and double scattering terms are considered together with their modification by reflection terms, which allow the projectile to oscillate back and forth an arbitrary number of times within a pair of nucleons. Reflections and spin and isospin flips are found to constitute a determining factor in a qualitative reproduction of the correct shape of observed angular distributions, in particular for backward scattering angles. Reflections are probably unimportant in πd scattering.