Polarization transfer in proton compton scattering at high momentum transfer

Abstract

Compton scattering from the proton was investigated at s=6.9GeV2 and t=-4.0GeV2 via polarization transfer from circularly polarized incident photons. The longitudinal and transverse components of the recoil proton polarization were measured. The results are in disagreement with a prediction of perturbative QCD based on a two-gluon exchange mechanism, but agree well with a prediction based on a reaction mechanism in which the photon interacts with a single quark carrying the spin of the proton. © 2005 The American Physical Society.