We examine the scattering of charged pions from the trinucleon system at a pion energy of 180 MeV. The motivation for this study is the structure seen in the experimental angular distribution of back-angle scattering for ${\pi }^{+}{-}^3\mathrm{He}$ and ${\pi }^{-}{-}^3\mathrm{H}$ but for neither ${\pi }^{-}{-}^3\mathrm{He}$ nor ${\pi }^{+}{-}^3\mathrm{H}$. We consider the addition of a double spin flip term to an optical model treatment and find that, though the contribution of this term is non-negligible at large angles for ${\pi }^{+}{-}^3\mathrm{He}$ and ${\pi }^{-}{-}^3\mathrm{H}$, it does not reproduce the structure seen in the experiment.

• Received 15 October 1998

DOI:https://doi.org/10.1103/PhysRevC.59.1290