Elastic π+ scattering on polarized 3He

Asymmetries, Ay, for π+ elastic scattering from polarized 3He were measured in the P33 resonance region, where the π‐nucleon force is strongly energy and isospin dependent. Preliminary results at energies of 142 and 180 MeV show large positive Ay near 90°, shifted to larger angles than predicted. At angles near 50° there is evidence for negative asymmetries of about −0.2 in contrast to several theoretical predictions that use up‐to‐date Faddeev wave functions and a first‐order optical potential. Inclusion of a Δ‐neutron spin‐spin interaction gives an excellent fit to the data at 180 MeV.