EG1B run

Spokesperson

Volker Burkert

Year

2006

Abstract

The longitudinal target-spin asymmetry $A_{\rm UL}$ for the exclusive electroproduction of high energy photons was measured for the first time in $e\vec{p} \rightarrow e^{\prime}p\gamma$. A significant azimuthal angular dependence was observed, resulting from the interference of the Deeply Virtual Compton Scattering and Bethe-Heitler processes. The amplitude of $\sin\phi$ moment is $0.252\pm0.042^{stat}\pm0.020^{sys}$, and the amplitude of the $sin2\phi$ moment, a twist-3 term, is $-0.022\pm0.045^{stat}\pm0.020^{sys}$. In addition, the kinematic dependences of the target-spin asymmetry were studied. The asymmetry is in good agreement with theoretical calculations, and is sensitive to the Generalized Parton Distributions $\widetilde{\cal H}$ and ${\cal H}$.

Comment

The experiment data are from EG1b taken from Sep. 2000 to Apr. 2001.

Publication

1. S. Chen, H. Avakian, V.D. Burkert, P. Eugenio, and CLAS collaborations Measurement of Deeply Virtual Compton Scattering with a Polarized Proton Target // Phys. Rev. Lett. 97, 072002 (2006)

Quantities

A_UL

Measurements