Current status and future measurements of DVCS at HERMES Original Research Article

Sizable beam-spin, target-spin and beam-charge azimuthal asymmetries in hard electroproduction of photons have been measured at the HERMES experiment using the 27.6 GeV HERA electron beam. The observed asymmetries are attributed to the interference of the Bethe-Heitler and Deeply Virtual Compton Scattering (DVCS) processes. Polarized hydrogen and deuterium targets are used to access the DVCS amplitudes of protons and neutrons. In addition, HERMES observed for the first time DVCS amplitudes which appear in the coherent scattering off nuclei. In 2005, the HERMES spectrometer will be upgraded by a recoil detector to measure the recoiling proton and thus identify the complete final state of the DVCS process. With improved kinematic resolution and background suppression HERMES aims to access the Generalized Parton Distributions (GPDs) of protons and neutrons and possibly those of nuclear states.