Measurement Of The Polarization In Large-Angle Pi-P Elastic-Scattering At 2.93 And 3.25 Gev-C

We have measured the polarization for elastic scattering in the reaction ${\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}p$ at 2.93 and 3.25 GeV/c using a polarized proton target and multiwire proportional chambers (MWPC's) with emphasis on large-angle scattering. Events were selected by fast scintillation-counter logic. Beam trajectories were measured with four MWPC's and the scattered-particle angles were measured with one or two MWPC's; elastic events were determined by coplanarity and angle-angle correlations. The polarization is in agreement with previous measurements below $|t|=2.0$ (${\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$, and crosses from negative to positive near the secondary dip in the differential cross section $\frac{d\ensuremath{\sigma}}{\mathrm{dt}}$. In the backward region, an energy dependence appears with the polarization being large and negative at 2.93 GeV/c and consistent with zero at 3.25 GeV/c.