Deeply-Virtual Compton Scattering on Deuterium and Neon at HERMES

TL;DR

This paper reports the first measurement of azimuthal beam-spin asymmetries in real photon electroproduction off nuclei, providing a new way to access generalized parton distributions through deeply-virtual Compton scattering.

Contribution

It presents the first observation of these asymmetries in nuclear targets, demonstrating a novel experimental approach to study the internal structure of nuclei via GPDs.

Findings

First observation of azimuthal beam-spin asymmetries in nuclei

Evidence of interference between Bethe-Heitler and DVCS processes

Data collected on deuterium and neon targets at HERMES

Abstract

We report the first observation of azimuthal beam-spin asymmetries in hard electroproduction of real photons off nuclei. Attributed to the interference between the Bethe-Heitler process and the deeply-virtual Compton scattering process, the asymmetry gives access to the latter at the amplitude level. This process appears to be the theoretically cleanest way to access generalized parton distributions. The data presented here have been accumulated by the HERMES experiment at DESY, scattering the HERA 27.6 GeV positron beam off deuterium and neon gas targets.