Beam-Charge Asymmetry associated with DVCS at HERMES

Abstract

We report the first observation of an azimuthal asymmetry in the hard electroproduction of real photons with respect to the charge of the incoming lepton beam. The asymmetry is attributed to the interference between the Bethe-Heitler process and the deeply-virtual Compton scattering process, which 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 have been accumulated by the HERMES experiment at DESY, scattering the HERA 27.6 GeV electron/positron beam off an unpolarized hydrogen gas target.

4 pages, 2 figures. Contribution to the European Workshop on the QCD Structure of the Nucleon (QCD - N'02), Ferrara, Italy, 3-6 Apr 2002, to be published in Nucl. Phys. A

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• The dual parameterization of the proton generalized parton distribution functions H and E and description of the DVCS cross sections and asymmetries
• Energy momentum tensor, stability, and the D-term of Q-balls
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• The dynamic origins of fermionic D-terms
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• Real and Virtual Compton Scattering in a Regge Approach
• 2D energy-momentum tensor distributions of nucleon in a large-$N_c$ quark model from ultra-relativistic to non-relativistic limit
• Resumming soft and collinear contributions in deeply virtual Compton scattering
• Unitary constraints on Deeply Virtual Compton Scattering
• Nuclear effects and their interplay in nuclear DVCS amplitudes