Detailed QCD analysis of twist-3 effects in deeply virtual Compton scattering observables
Abstract
In this paper I present a detailed QCD analysis of twist-3 effects in the Wandzura-Wilczek (WW) approximation in deeply virtual Compton scattering (DVCS) observables for various kinematical settings, representing the DESY HERA, HERMES, CLAS and the planned EIC (electron-ion-collider) experiments. I find that the twist-3 effects in the WW approximation are almost always negligible at collider energies but can be large for low ${Q}^{2}$ and smaller ${x}_{\mathrm{bj}}$ in observables for the lower energy, fixed target experiments directly sensitive to the real part of DVCS amplitudes like the charge asymmetry. Conclusions are then drawn about the reliability of extracting twist-2 generalized parton distributions (GPDs) from experimental data and a first, phenomenological, parametrization of the LO and NLO twist-2 GPD H, describing all the currently available DVCS data within the experimental errors is given.