Exclusive Leptoproduction of Real Photons on a Longitudinally Polarised Hydrogen Target

Understand

Polarisation asymmetries are measured for the hard exclusive leptoproduction of real photons from a longitudinally polarised hydrogen target.

• These asymmetries arise from the deeply virtual Compton scattering and Bethe-Heitler processes.
• From the data are extracted two asymmetries in the azimuthal distribution of produced real photons about the direction of the exchanged virtual photon: A_UL with respect to the target polarisation and A_LL with respect to the product of the beam and target polarisations.
• Results for both asymmetries are compared to the predictions from a generalised parton distribution model.