Polarization of Recoil Protons from Neutral Pion Photoproduction

Abstract

The polarization of recoiling protons from the photoproduction of ${\pi }^0$ mesons on liquid hydrogen has been measured for primary photon energies between 500 and 1000 MeV over a range of ${\pi }^0$ c.m. angles from 55° to 130°. The results show structure not observed previously in experiments of less precision. In particular, the polarization at 90° c.m. is close to zero at a primary photon energy of 900 MeV. Also, a strong dependence of polarization on ${\pi }^0$ c.m. angle between 600 and 900 MeV was observed. A subsidiary measurement of the polarization of the recoil protons from elastic $e-p$ scattering at 900 MeV and $q^2=10\mathrm{}$ ${\mathrm{F}}^{-2\mathrm{}}$ gave a value (1.3±2.0)%.