Analyzing power forπ−pcharge exchange and a test of isospin invariance up toηthreshold

Abstract

The analyzing power for ${\pi }^{-}p\to {\pi }^{0}n$ has been measured at five incident momenta from 547 to 687 MeV/c using a transversely polarized target. Data were obtained with scintillation counters at 10 angles simultaneously covering the range $-0.9\mathrm{}\le {cos\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}^{\pi }\le 0.9$. Our results and those of Kim et al. are used for a model-independent test of isospin invariance which is based on the triangle inequalities applied to the transversity-up as well as the transversity-down cross sections. No evidence is found of isospin violation.