Generalized parton distributions, the hunt for quark orbital momenta

TL;DR

This paper reviews the current experimental status of Generalized Parton Distributions, focusing on the less known GPD E^q, which is crucial for understanding the nucleon spin structure.

Contribution

It provides a comprehensive review of experimental efforts to determine GPDs, especially E^q, and discusses future prospects in nucleon spin research.

Findings

Current experimental data on GPDs are limited, especially for E^q.

Understanding E^q is essential for solving the nucleon spin puzzle.

The paper highlights upcoming experimental opportunities.

Abstract

The Generalized Parton Distributions (GPDs) are the appropriate framework for a universal description of the partonic structure of the nucleon. They characterize the dynamics of quarks and gluons inside the nucleon and consequently contain information about the spin of the nucleon. The current experimental knowledge about GPDs is reviewed with the emphasis on the determination of E^q(Q^2,x,xi,t), the least known and constrained GPD, of particular importance in the nucleon spin puzzle. The perspectives of this experimental program are also addressed.