Speaker
Dr
Sergey Yashchenko
(DESY)
Description
Hard exclusive leptoproduction of real photons (deeply virtual Compton scattering, DVCS) or mesons on nucleons is widely considered to be one of the most promising reactions that can provide information about the structure of the nucleon in the framework of generalized parton distributions (GPDs). During last years, DVCS has been extensively studied at the HERMES experiment through measurements of various cross-section asymmetries. HERMES has collected a wealth of data on scattering a 27.5 GeV longitudinally polarized electron/positron beam off unpolarized, longitudinally and transversely polarized hydrogen targets, as well as off unpolarized and longitudinally polarized deuterium targets. The collected data allow the measurement of a complete set of asymmetries with respect to beam charge, beam helicity and target polarization alone and also with respect to their different combinations. These asymmetries are sensitive to real and/or imaginary parts of different combinations of Compton form factors and can be used to constrain different GPDs. From measurements of exclusive meson production on hydrogen and deuterium targets complementary information about GPDs can be obtained. The study of the azimuthal distribution of the decay products via spin density matrix elements provides constraints on helicity amplitudes used to describe exclusive meson production. Recent results on the exclusive reactions from HERMES are presented.
Primary author
Dr
Sergey Yashchenko
(DESY)
