Recoil Proton Polarization in Eta Photoproduction

Abstract
We measured the polarization of the recoil proton in the process γp→pη0, at 90° in the center-of-mass system, at incoming photon energies from 0.8 to 1.1 GeV. Detection of all three particles in the final state pγγ permitted observation of this process with little background. Subsequent rescattering off carbon nuclei yielded sizable polarization values for the protons, indicating considerable S−P—wave interference in the production process.