Twist-2 generalized transverse-momentum dependent parton distributions and the spin/orbital structure of the nucleon

Abstract

Generalized transverse-momentum dependent parton distributions (GTMDs) encode the most general parton structure of hadrons. Here we focus on two twist-2 GTMDs which are denoted by F1,4 and G1,1 in parts of the literature. As already shown previously, both GTMDs have a close relation to orbital angular momentum of partons inside a hadron. However, recently even the mere existence of F1,4 and G1,1 has been doubted. We explain why this claim does not hold. We support our model-independent considerations by calculating the two GTMDs in the scalar diquark model and in the quark-target model, where we also explicitly check the relation to orbital angular momentum. In addition, we compute F1,4 and G1,1 at large transverse momentum in perturbative quantum chromodynamics and show that they are nonzero. © 2014 American Physical Society.