The 3D structure of the Nucleon in momentum space: TMD phenomenology

TL;DR

This paper reviews the current understanding of the three-dimensional momentum space structure of nucleons, highlighting recent progress in quark TMD extractions and the challenges in understanding gluon TMDs.

Contribution

It provides an overview of recent phenomenological extractions of quark TMDs and introduces a model calculation for gluon TMDs at leading twist.

Findings

Quark TMDs are now extracted with precision comparable to collinear PDFs.

Gluon TMDs remain poorly understood phenomenologically.

A new model covers all polarized and unpolarized gluon TMDs at leading twist.

Abstract

I give a brief overview of our current understanding of the internal partonic 3D structure of nucleons in momentum space. I discuss some recent extractions of transverse-momentum-dependent distributions for quarks, whose analyses in the unpolarized case are reaching a theoretical precision comparable to collinear parton distribution functions. On the contrary, gluon transverse-momentum-dependent distributions are poorly known from a phenomenological point of view. I briefly review their general properties and sketch a recent model calculation covering all (un)polarized combinations at leading twist.