Speaker
Sergey Yaschenko
(DESY)
Description
Hard exclusive leptoproduction of real photons, Deeply Virtual Compton Scattering (DVCS), is one of the theoretically cleanest processes to access Generalized Parton Distributions (GPDs). The theoretical framework of GPDs includes information on the correlated transverse spatial and longitudinal momentum distributions of partons in the nucleon. In addition, GPDs may provide a way to investigate the contribution of quark orbital angular momentum to the spin of the nucleon. The HERMES experiment at DESY, Hamburg, collected unique data on DVCS utilizing the HERA polarized electron or positron beams with an energy of 27.6 GeV and longitudinally and transversely polarized or unpolarized gas targets (H, D or heavier nuclei). The azimuthal asymmetries measured in the DVCS process allow access to the imaginary and/or real part of certain combinations of GPDs. For the last two years of HERA running, the HERMES collaboration installed a recoil detector to improve the selection of DVCS events by direct measurement of the recoil protons. An overview of recent HERMES results on DVCS is presented including results on DVCS and associated processes ep -> e gamma p pi0 and ep -> e gamma n pi+ in the Delta-resonance region obtained with the recoil detector.
Author
Sergey Yaschenko
(DESY)
