Gluon generalized parton distributions and angular momentum in a light-cone spectator model

TL;DR

This paper models gluon distributions and angular momentum inside the proton using a light-cone spectator approach, providing numerical results and insights into gluon contributions to proton spin.

Contribution

It introduces a light-cone spectator model to calculate gluon GPDs and angular momentum, offering new numerical insights and comparison with lattice results.

Findings

Gluon GPDs vary with transverse momentum transfer, differing from forward distributions.

The gluon total angular momentum contribution to proton spin is approximately 0.19.

The model predicts a negative kinetic orbital angular momentum for gluons.

Abstract

We study the leading twist gluon generalized parton distributions (GPDs) and the gluon angular momentum inside the proton within a light-cone spectator model. Using the light-cone wave functions derived from the model, we provide the expressions of these distributions at the particular kinematical point $\xi=0$ in the overlap representation. The numerical results of the $H^g$, $E^g$, $\tilde{H}^g$, $H_T^g$ and $E_T^g$ as functions of $x$ at different $\Delta_T$ are presented. Particularly, $H^g$, $\tilde{H}^g$ at non-zero $\Delta_T$ are different from their forward counterparts, the unpolarized distribution $f_1^g$ and the helicity distribution $g_1^g$, respectively. We also obtain the total angular momentum of the gluon contributed to the proton spin $J^g=0.19$, which is consistent with the recent lattice calculation after the uncertainties is considered. The kinetic orbital angular momentum is also calculated and is negative in our model.