The pion pole in hard exclusive vector-meson leptoproduction

TL;DR

This paper investigates the role of the pion pole in omega meson production during hard exclusive leptoproduction, using GPDs and comparing results with HERMES data, highlighting its significance and extracting the pi-omega transition form factor.

Contribution

It introduces a novel analysis of the pion pole contribution in omega production using GPDs and provides a new extraction of the pi-omega transition form factor from experimental data.

Findings

Pion pole is a significant contributor to omega production.

The model's omega SDME predictions agree well with HERMES data.

The pion pole's role in rho0 and phi production is also discussed.

Abstract

Exploiting a set of generalized parton distributions (GPDs) derived from analyses of hard exclusive leptoproduction of rho0, phi and pi+ mesons, we investigate the omega spin density matrix elements (SDMEs) recently measured by the HERMES collaboration. It turns out from our study that the pion pole is an important contribution to omega production. It will be treated as a one-particle exchange since its evaluation from the GPD E-tilde considerably underestimates its contribution. As an intermediate step of our analysis we extract the pi-omega transition form factor for photon virtualities less than 4 GeV^2. From our approach we achieve results for the omega SDMEs in good agreement with the HERMES data. The role of the pion pole in exclusive rho0 and phi leptoproduction is discussed too.