Compton scattering from the proton was investigated at s=6.9 (GeV/c)**2 and \t=-4.0 (GeV/c)**2 via polarization transfer from circularly polarized incident photons. The longitudinal and transverse components of the recoil proton polarization were measured. The results are in excellent agreement with a prediction based on a reaction mechanism in which the photon interacts with a single quark carrying the spin of the proton and in disagreement with a prediction of pQCD based on a two-gluon exchange mechanism.
@article{arxiv.nucl-ex/0410001,
title = {Polarization Transfer in Proton Compton Scattering at High Momentum Transfer},
author = {D. J. Hamilton and V. H. Mamyan and the Jefferson Lab Hall A Collaboration},
journal= {arXiv preprint arXiv:nucl-ex/0410001},
year = {2008}
}