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 π+-3He and π--3H but for neither π--3He nor π+-3H. 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 π+-3He and π--3H, it does not reproduce the structure seen in the experiment. copyright 1999 The American Physical Society