DVCS at HERMES
II. Physikalisches Institut, Justus-Liebig-Universität Gießen, 35394 Gießen, Germany
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Published online: 20 March 2014
Azimuthal asymmetries in exclusive electroproduction of real photons by the longitudinally polarized HERA positron beam scattering off an unpolarized hydrogen target (ep → epγ) are measured at HERMES. The asymmetries arise from the interference of DVCS with the Bethe-Heitler process, where DVCS provides the theoretically cleanest access to Generalized Parton Distributions. In 2006, HERMES was upgraded with a recoil detector that, together with the forward spectrometer, allowed the detection of all final state particles in the process ep → epγ. This helped to reduce the background from the associated reaction ep → eγπN from 12% down to a negligible level. In addition, the selection and measurement of the associated reaction itself is shown to be feasible and first results have been obtained.
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