Measurement of Deeply Virtual Compton Scattering with a Polarized Proton Target

TL;DR

This paper reports the first measurement of the longitudinal target-spin asymmetry in deeply virtual Compton scattering using a polarized proton target, providing insights into the proton's internal structure through generalized parton distributions.

Contribution

It presents the first experimental measurement of the target-spin asymmetry in DVCS with a polarized proton, confirming theoretical predictions and advancing understanding of proton structure.

Findings

Significant azimuthal dependence observed in asymmetry

Amplitude of sin(phi) moment measured as 0.252 +/- 0.042(stat) +/- 0.020(sys)

Results agree with theoretical calculations of GPDs H and H-tilde

Abstract

The longitudinal target-spin asymmetry A_UL for the exclusive electroproduction of high energy photons was measured for the first time in p(e,e'p\gamma). The data have been accumulated at Jefferson Lab with the CLAS spectrometer using 5.7 GeV electrons and a longitudinally polarized NH_3 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(phi) 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-tilde.