Measurements of Inelastic Compton Scattering

Abstract
We have measured inelastic Compton scattering of 21-GeV bremsstrahlung photons on protons, for pT above 1 GeV/c. The yield of photons after subtracting π0 and η decay contributions appears to be nonhadronic and is greater than parton-model predictions for integer-charged partons. The constituent-interchange model provides a possible explanation.