Comments on Exclusive Electroproduction of Transversely Polarized Vector Mesons

TL;DR

This paper analyzes the limitations of QCD factorization in the electroproduction of transversely polarized vector mesons, highlighting infrared divergences and the need for phenomenological regularizations affecting the interpretation of nucleon parton distributions.

Contribution

It demonstrates the breakdown of QCD factorization in this process and discusses the implications of infrared divergences on phenomenological modeling and the role of polarized gluons.

Findings

QCD factorization cannot be applied at leading order for this process.

Infrared divergences arise from both Feynman diagrams and nucleon distributions.

Regularization methods influence the interpretation of parton distribution contributions.

Abstract

We discuss the electroproduction of light vector mesons from transversely polarized photons. Here QCD factorization cannot be applied as shown explicitly in a leading order calculation of corresponding Feynman diagrams. It is emphasized that present infrared singular contributions cannot be regularized through phenomenological meson distribution amplitudes with suppressed endpoint configurations. We point out that infrared divergencies arise also from integrals over skewed parton distributions of the nucleons. In a phenomenological analysis of transverse vector meson production model dependent regularizations have to be applied. If this procedure preserves the analytic structure suggested by a leading order calculation of Feynman diagrams, one obtains contributions from nucleon parton distributions and their derivatives. In particular polarized gluons enter only through their derivative.