Twist-3 contributions to wide-angle photoproduction of pions

TL;DR

This paper analyzes the twist-3 contributions to wide-angle pi^0 photoproduction, demonstrating their dominance and importance for accurate, gauge-invariant results consistent with experimental data.

Contribution

It includes both 2-particle and 3-particle twist-3 contributions, providing a more complete and gauge-invariant theoretical framework for the process.

Findings

Twist-3 contributions dominate the cross section.

Results align well with recent CLAS measurements.

Both 2-particle and 3-particle twist-3 terms are essential.

Abstract

We investigate wide-angle pi^0 photoproduction within the handbag approach to twist-3 accuracy. In contrast to earlier work both the 2-particle as well as the 3-particle twist-3 contributions are taken into account. It is shown that both are needed for consistent results that respect gauge invariance and crossing properties. The numerical studies reveal the dominance of the twist-3 contribution. With it fair agreement with the recent CLAS measurement of the pi^0 cross section is obtained. We briefly comment also on wide-angle photoproduction of other pseudoscalar mesons.