Exclusive leptoproduction of a light vector meson at the twist-3 in a GTMD framework

TL;DR

This paper develops a comprehensive theoretical framework for exclusive leptoproduction of light vector mesons at high energy, incorporating twist-3 accuracy and GTMD formalism to describe all helicity amplitudes, including transversely polarized mesons.

Contribution

It introduces a novel GTMD-based approach at twist-3 accuracy that overcomes endpoint singularities and expresses results in terms of collinear distribution amplitudes.

Findings

Describes all helicity amplitudes including transverse polarization.

Overcomes endpoint singularities using GTMD matrix elements.

Provides a twist-expansion of the proton target in a comprehensive formalism.

Abstract

We provide the most general description of the exclusive leptoproduction of a light vector meson, at high center-of-mass energy, within the CGC/shockwave formalism. We keep a twist-3 accuracy in $s$ channel, thus being able to describe all possible helicity amplitudes, including the ones for the production of a transversally polarized meson. In this latter case, we overcome the well-known issue of endpoint singularities by promoting the GPD to a GTMD given by matrix elements of dipole and double dipole operators. The all-twists treatment of the proton (nucleon) target allow to safely twist-expand the general vacuum-to-meson matrix elements. Therefore, unlike previous attempts in the modified perturbative approach, our final results are expressed in terms of the twist-3 collinear distribution amplitudes, introduced in the context of the higher-twist collinear formalism.