π−p charge-exchange analyzing power from 547 to 687 MeV/c

The ${\pi }^{\mathrm{-}}$p charge-exchange analyzing power has been measured from 547 to 687 MeV/c in the center-of-mass angular range -0.9≤cosθ${̃}_{\pi }$≤0.9 using a transversely polarized target. The recoil neutron was detected in coincidence with a photon from ${\pi }^0$ decay. The results are compared with the three recent partial-wave analyses (PWA’s); the VPI analysis is most consistent with our measured distributions except at 687 MeV/c where no PWA agrees with our data. The charge-exchange transversity cross sections are evaluated using the differential cross sections of Borcherding et al. These transversity cross sections are used in conjunction with earlier ${\pi }^{\pm }$p data by our group to test the triangle inequalities which are a model-independent test of isospin invariance. Our data satisfy these inequalities everywhere; in contrast, Abaev et al. have reported a violation of more than 5 standard deviations at 685 MeV/c.