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 ${F}_{1,4}$ and ${G}_{1,1}$ 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 ${F}_{1,4}$ and ${G}_{1,1}$ 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 ${F}_{1,4}$ and ${G}_{1,1}$ at large transverse momentum in perturbative quantum chromodynamics and show that they are nonzero.