Measurement of Deeply Virtual Compton Scattering with a Polarized-Proton Target

Abstract

The longitudinal target-spin asymmetry A_UL for the exclusive electroproduction of high-energy photons was measured for the first time in ep→→e^'pγ. The data have been accumulated at JLab with the CLAS spectrometer using 5.7 GeV electrons and a longitudinally polarized NH₃ target. A significant azimuthal angular dependence was observed, resulting from the interference of the deeply virtual Compton scattering and Bethe-Heitler processes. The amplitude of the sin⁡ϕ moment is 0.252±0.042^stat±0.020^sys. Theoretical calculations are in good agreement with the magnitude and the kinematic dependence of the target-spin asymmetry, which is sensitive to the generalized parton distributions H∼ and H.