Hard diffractive processes and non-perturbative matrix elements beyond leading twist: rhoT-meson production

TL;DR

This paper calculates the impact factor for gamma* to rhoT transition including twist 3 effects within the kt-factorization approach, ensuring gauge invariance and simplifying non-perturbative inputs for exclusive processes.

Contribution

It provides a gauge-invariant expression for the impact factor and reduces the non-perturbative distribution amplitudes to a minimal set, advancing the theoretical understanding of transversely polarized vector meson production.

Findings

Derived a gauge-invariant impact factor expression.

Reduced distribution amplitudes to a minimal, consistent set.

Proved the equivalence of two rhoT distribution amplitude parametrizations.

Abstract

Within the kt-factorization approach, we evaluate the impact factor of the transition gamma* -> rhoT taking into account the twist 3 contributions. We show that a gauge invariant expression is obtained with the help of QCD equations of motion. More generally, relying on these equations and on the invariance under rotation on the light-cone of the factorized amplitude, the non-perturbative Distribution Amplitudes can be reduced to a minimal set. This opens the way to a consistent treatment of factorization for exclusive processes with a transversally polarized vector meson. We prove the equivalence of two proposed parametrizations of the rhoT distribution amplitudes.