Measurement of Deeply Virtual Compton Scattering Beam-Spin Asymmetries

Abstract

The beam-spin asymmetries in the hard exclusive electroproduction of photons on the proton ($\overrightarrow{e}p\to ep\gamma$) were measured over a wide kinematic range and with high statistical accuracy. These asymmetries result from the interference of the Bethe-Heitler process and of deeply virtual Compton scattering. Over the whole kinematic range ($x_B$ from 0.11 to 0.58, $Q^2$ from 1 to $4.8{\mathrm{GeV}}^2$, $-t$ from 0.09 to $1.8{\mathrm{GeV}}^2$), the azimuthal dependence of the asymmetries is compatible with expectations from leading-twist dominance, $A\simeq a\sin \varphi /(1+c\cos \varphi )$. This extensive set of data can thus be used to constrain significantly the generalized parton distributions of the nucleon in the valence quark sector.