An attempt to understand exclusive pi+ electroproduction

Abstract

Hard exclusive pi+ electroproduction is investigated within the handbag approach. The prominent role of the pion-pole contribution is demonstrated. It is also shown that the experimental data require a twist-3 effect which ensues from the helicity-flip generalized parton distribution H_T and the twist-3 pion wave function. The results calculated from this handbag approach are compared in detail with the experimental data on cross sections and spin asymmetries measured with a polarized target. It is also commented on consequences of this approach for exclusive \pi^0 and vector-meson electroproduction.

Comments: 35 pages, 12 figures, using Latex, a number of additional comments have been included in the text, e.g. in paragraph above (3) or at end of sect. 9