Bochum 2009 – scientific programme

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HK: Fachverband Hadronen und Kerne

HK 70: Hadron Structure and Spectroscopy II

HK 70.4: Talk

Thursday, March 19, 2009, 17:45–18:00, H-ZO 30

Selected HERMES Results on Deeply Virtual Compton Scattering — •Caroline Riedl — DESY/Zeuthen

The HERMES experiment has collected a rich data set for the analysis of Deeply Virtual Compton Scattering (DVCS), employing different settings of the beam helicity, the beam charge, the target polarization (both longitudinal and transverse) and the target type (H, D and heavier nuclei).

The azimuthal asymmetries measured for the exclusive DVCS reaction allow to access the imaginary and/or real part of certain Generalized Parton Distributions (GPDs). Those GPDs are of great theoretical interest as they embody both spatial and momentum density information of quarks and gluons. Moreover, in a certain kinematic limit, certain moments of the quark (gluon) GPDs E and H deliver the total angular momentum carried by quarks (gluons) in the nucleon.

Until the year 2005, the recoiling target nucleon from the DVCS reaction was not detected by HERMES. Exclusivity was ensured indirectly by a missing-mass-technique. Data with a new Recoil Detector were taken in the last two years of HERA running. The Recoil Detector can identify the recoiling target nucleon and the particles from underlying background processes and can thus be used to directly tag exclusive events and to reject competing background channels. Selected DVCS results will be shown and an outlook to results from the HERMES Recoil Detector will be presented.