Accessing GPDs through the exclusive photoproduction of a $ \gamma $-meson pair

TL;DR

This paper explores how exclusive photoproduction of a photon-meson pair at high invariant mass can be used to access both chiral-even and chiral-odd generalized parton distributions (GPDs), providing insights into their experimental measurement.

Contribution

It introduces a method to access poorly known chiral-odd GPDs through exclusive photon-meson production in a QCD factorisation framework at leading order and twist.

Findings

Potential to measure GPDs at JLab 12-GeV

Access to small ξ regime at LHC pPb collisions

Feasibility of experimental detection discussed

Abstract

We consider the exclusive photo-production of a photon-meson pair with a large invariant mass, working in the QCD factorisation framework. Explicitly, we consider a $ \rho $-meson or a charged $ \pi $ in the final state. This process gives access both to chiral-even GPDs and chiral-odd GPDs, which are not well-known experimentally, especially the latter ones. The computation is performed at leading order and leading twist. We discuss the prospects of measuring them in experiments, focusing on the kinematics at the JLab 12-GeV experiment, and pPb ultra-peripheral collisions at LHC. In particular, the latter gives access to the small $ \xi $ regime of GPDs.