Exclusive meson leptoproduction and spin dependent generalized parton distributions

TL;DR

This paper discusses how exclusive meson leptoproduction can be described using generalized parton distributions (GPDs), highlighting the role of spin dependence, chiral odd GPDs, and their connection to nucleon structure and transversity.

Contribution

It introduces a detailed analysis of spin-dependent GPDs, including chiral odd functions, and shows how different meson production processes can isolate specific GPDs, especially chiral odd ones.

Findings

Pseudoscalar production isolates chiral odd GPDs.

Cross sections and asymmetries depend on the nucleon's tensor charge.

Analysis of GPD analyticity and partonic interpretation issues.

Abstract

Exclusive meson leptoproduction from nucleons in the deeply virtual exchanged boson limit can be described by generalized parton distributions (GPDs). Including spin dependence in the description requires 8 independent quark-parton and gluon-parton functions. The chiral even subset of 4 quark-nucleon GPDs are related to nucleon form factors and to parton distribution functions. The chiral odd set of 4 quark-nucleon GPDs are related to transversity, the tensor charge, and other quantities related to transversity. Different meson or photon production processes access different combinations of GPDs. This is analyzed in terms of t-channel exchange quantum numbers, $J^{PC}$ and it is shown that pseudoscalar production can isolate chiral odd GPDs. There is a sensitive dependence in various cross sections and asymmetries on the tensor charge of the nucleon and other transversity parameters. We also consider, briefly, the analyticity of the GPDs and the problems with the partonic interpretation in the ERBL region.