Cross-section values for Compton scattering on the proton were measured at 25 kinematic settings over the range s = 5-11 and -t = 2-7 GeV2 with statistical accuracy of a few percent. The scaling power for the s-dependence of the cross section at fixed center of mass angle was found to be 8.0 +/ 0.2, strongly inconsistent with the prediction of perturbative QCD. The observed cross-section values are in fair agreement with the calculations using the handbag mechanism, in which the external photons couple to a single quark.
@article{arxiv.nucl-ex/0701068,
title = {Compton Scattering Cross Section on the Proton at High Momentum Transfer},
author = {A. Danagoulian and V. H. Mamyan and M. Roedelbronn and the Hall A Collaboration},
journal= {arXiv preprint arXiv:nucl-ex/0701068},
year = {2008}
}