Odderon and photon exchange in pseudoscalar meson production

TL;DR

This paper investigates exclusive neutral pion production in electron-proton scattering, highlighting the roles of odderon and photon exchanges, and proposes that observing this process at HERA could confirm the existence of the soft odderon.

Contribution

It provides a nonperturbative QCD calculation of odderon exchange and evaluates photon exchange exactly using experimental data, offering new insights into meson production mechanisms.

Findings

Odderon exchange results in a larger inelastic cross section.

Photon exchange contribution is precisely evaluated from experimental data.

Observation at HERA could confirm the soft odderon presence.

Abstract

We consider exclusive $\pi^0$ production in ep-scattering. At high energies odderon and photon exchange contribute. The photon exchange contribution is evaluated exactly using data for the total virtual photon-proton absorption cross section. The odderon exchange contribution is calculated in nonperturbative QCD, using functional integral techniques and the model of the stochastic vacuum. For the proton we assume a quark-diquark structure as suggested by the small odderon amplitude in pp and $p \bar{p}$ forward scattering. We show that odderon exchange leads to a much larger inelastic than elastic $\pi^0$ production cross section. Observing our process at HERA would establish the soft odderon.