The target asymmetry in hard vector-meson electroproduction and parton angular momenta

TL;DR

This paper investigates the target asymmetry in hard vector-meson electroproduction using the handbag approach, constructing the GPD E from double distributions and analyzing how experimental data can reveal parton angular momenta.

Contribution

The paper develops a method to construct the GPD E from double distributions and constrains it with form factors, enabling predictions of target asymmetry in vector meson electroproduction.

Findings

Predictions for target asymmetry across various vector mesons.

Constraints on GPD E from form factors and sum rules.

Insights into parton angular momenta from asymmetry measurements.

Abstract

The target asymmetry for electroproduction of vector mesons is investigated within the handbag approach. While the generalized parton distribution (GPD) H is taken from a previous analysis of the elctroproduction cross section, we here construct the GPD E from double distributions and constrain it by the Pauli form factors of the nucleon, positivity bounds and sum rules. Predictions for the target asymmetry are given for various vector mesons and discussed how experimental data on the asymmetry will further constrain E and what we may learn about the angular momenta the partons carry.