Chiral-odd transversity GPDs from a leading twist hard amplitude

TL;DR

This paper proposes a method to access chiral-odd transversity GPDs through exclusive meson production, providing perturbative calculations and a simple GPD model, with feasibility estimates for JLab and COMPASS experiments.

Contribution

It introduces a leading order perturbative calculation and a simple double distribution model for transversity GPDs in exclusive meson production.

Findings

Feasibility of measuring transversity GPDs at JLab and COMPASS.

Estimated cross sections suggest experimental viability.

Model provides a basis for future phenomenological studies.

Abstract

The chiral-odd transversity generalized parton distributions (GPDs) of the nucleon can be accessed experimentally through the exclusive photoproduction process gamma + N -> pi + rho + N', in the kinematics where the meson pair has a large invariant mass and the final nucleon has a small transverse momentum, provided the vector meson is produced in a transversally polarized state. We calculate perturbatively the scattering amplitude at leading order in alpha_s. We build a simple model for the dominant transversity GPD H_T(x,xi,t) based on the concept of double distribution. We estimate the unpolarized differential cross section for this process in the kinematics of the Jlab and COMPASS experiments. Counting rates show that the experiment looks feasible with the real photon beam characteristics expected at JLab@12 GeV, and with the quasi real photon beam in the COMPASS experiment.