An attempt to understand exclusive pi+ electroproduction

TL;DR

This paper investigates hard exclusive pi+ electroproduction using the handbag approach, highlighting the pion-pole contribution and the necessity of twist-3 effects from helicity-flip GPDs and pion wave functions to match experimental data.

Contribution

It demonstrates the importance of pion-pole and twist-3 effects in describing pi+ electroproduction within the handbag framework, providing detailed comparisons with experimental results.

Findings

Pion-pole contribution plays a dominant role.

Experimental data require twist-3 effects from H_T GPDs.

The approach offers insights into related pi^0 and vector-meson production.

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.