Measurement of the Spin-Rotation Parametersaandrforπ+p→π+p And

The spin-rotation parameters A and R for ${\ensuremath{\pi}}^{+}$p and ${\ensuremath{\pi}}^{\mathrm{\ensuremath{-}}}$p elastic scattering have been measured at pion momenta from 471 to 625 MeV/c using a frozen spin target polarized in the scattering plane and a recoil-proton polarimeter. Our results show that the major features of the recent \ensuremath{\pi}N partial-wave analyses (PWA's) are correct. This is the first time such confirmation has been possible. Some deviations outside the errors indicate the need for a new round of PWA's.