Exclusive photoproduction of a di-meson pair with large invariant mass

TL;DR

This paper studies the exclusive photoproduction of a di-meson pair with large invariant mass, using collinear factorisation, to explore Generalised Parton Distributions (GPDs) through a new class of $2 o 3$ processes.

Contribution

It introduces a framework for calculating the cross section of di-meson photoproduction at large invariant mass, including automation and numerical results relevant for GPD extraction.

Findings

Automated calculation of differential cross section at leading twist and order.

Numerical results provided for JLab 12 GeV kinematics.

Demonstrates the process as a new channel for GPD studies.

Abstract

We consider the exclusive photoproduction of a di-meson pair with large invariant mass, $\gamma N \rightarrow N' M_1M_2$, in the framework of collinear factorisation. The mesons considered $M_1$ and $M_2$ are either pions or rho mesons, charged or neutral. We consider the kinematic regime characterised by a large invariant mass of the two-meson system, and a small deflection of the nucleon in the centre-of-mass frame. In this kinematic domain, the amplitude factorises into a perturbative hard part and non-perturbative parts described by Generalised Parton Distributions (GPDs) and Distribution Amplitudes (DAs). We automate the calculation of the fully differential cross section at leading twist and leading order, and we present some numerical results at JLab 12 GeV kinematics. This class of processes provides yet more exclusive $2 \to 3$ channels that can be used to extract GPDs.