We determine the small-x asymptotics of the gluon helicity distribution in a proton at leading order in perturbative QCD at large Nc. To achieve this, we begin by evaluating the dipole gluon helicity TMD at small x. We then construct and solve novel small-x large-Nc evolution equations for the operator related to the dipole gluon helicity TMD. Our main result is the small-x asymptotics for the quark helicity distribution
I review the recently achieved, complete gauge invariant decomposition of the nucleon spin and clarify its connection to twist-three GPDs. I also discuss how to compute the gluon helicity [Formula: see text] on a lattice.
Probing gluon helicity with heavy flavor at the Electron-Ion Collider