Elastic scattering of pions from the three-nucleon system

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}{sup +}-{sup 3}He and {pi}{sup {minus}}-{sup 3}H but for neither {pi}{sup {minus}}-{sup 3}He nor {pi}{sup +}-{sup 3}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}{sup +}-{sup 3}He and {pi}{sup {minus}}-{sup 3}H, it does not reproduce the structure seen in the experiment. {copyright} {ital 1999} {ital The American Physical Society}