Generalized Parton Distributions and the Spin Structure of the Nucleon

TL;DR

This paper discusses generalized parton distributions as a new way to understand the nucleon's internal structure, especially its spin and orbital angular momentum, through theoretical, experimental, and computational approaches.

Contribution

It highlights the significance of generalized parton distributions in revealing nucleon structure and reviews experimental and lattice QCD methods to measure and calculate these distributions.

Findings

Generalized parton distributions unify form factors and parton distributions.

Deeply virtual Compton scattering enables experimental access to these distributions.

Lattice QCD offers promising first-principles calculations of the distributions.

Abstract

Generalized parton distributions are a new type of hadronic observables which has recently stimulated great interest among theorists and experimentalists alike. Introduced to delineate the spin structure of the nucleon, the orbital angular momentum of quarks in particular, the new distributions contain vast information about the internal structure of the nucleon, with the usual electromagnetic form factors and Feynman parton distributions as their special limits. While new perturbative QCD processes, such as deeply virtual Compton scattering and exclusive meson production, have been found to measure the distributions directly in experiments, lattice QCD offers a great promise to provide the first-principle calculations of these interesting observables.