Measurement of the Polarization in Backward-Angleπ+pElastic Scattering Between 2.50 and3.75 GeVc

The polarization in ${\pi }^{+}p$ elastic scattering in the backward hemisphere has been measured at 2.50, 2.75, 2.93, 3.25, and $3.75 \frac{\mathrm{GeV}}{c}$. The data cover a range $u$ of -0.5 to +0.1 ${\left(\frac{\mathrm{GeV}}{c}\right)}^2$ and show a positive peak at approximately the same c.m. angle as the minimum in the differential cross section. At angles farther away from 180° the polarization becomes negative. The data are not well explained by either resonance or Reggepole models.