Wide-angle photo- and electroproduction of pions to twist-3 accuracy

We investigate wide-angle photo- and electroproduction of pions within the handbag mechanism in which the gamma(*)N -> pi N' amplitudes factorize into hard partonic subprocess amplitudes, gamma(*)q -> pi q', and form factors representing 1/x-moments of generalized parton distributions (GPDs). The subprocess is calculated to twist-3 accuracy taking into account the 2- and 3-body Fock components of the pion. Both components are required for achieving gauge invariance in QED and QCD. The twist-2 and twist-3 distribution amplitudes (DAs) of the pion as well as the form factors are taken from our study of pi(0) photoproduction. Extensive results on photoproduction of charged pions are presented and compared to experiment. Predictions on electroproduction of pions as well as on spin effects are also given. As a byproduct of our analysis we also obtain the complete twist-3 subprocess amplitudes contributing to deeply virtual electroproduction of pions.