engleski

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 γ^(*) N → π N' amplitudes factorize into hard partonic subprocess amplitudes, γ^(*) q → π 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 π 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.

QCD ; exclusive processes ; pion electroproduction ; wide-angle ; higher-twist

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