Twist Three Generalized Parton Distributions for Orbital Angular Momentum

TL;DR

This paper investigates the connection between twist-three generalized parton distributions and orbital angular momentum in the proton, using a diquark model to explore how different gauge links affect the description of orbital angular momentum.

Contribution

It introduces a detailed analysis of the twist-three GPD $ ilde{E}_{2T}$ and the GTMD $F_{14}$, elucidating their roles in describing proton orbital angular momentum with different gauge link choices.

Findings

GTMD $F_{14}$ can describe both Jaffe-Manohar and Ji OAM depending on gauge links.

The diquark model calculation shows how final state interactions influence OAM descriptions.

The connection between GPD $ ilde{E}_{2T}$ and orbital angular momentum is clarified.

Abstract

We study the orbital angular momentum contribution to the spin structure of the proton. It is well known that the quark and gluon spin contributions do not add up to the proton spin. We motivate the connection between the Generalized Transverse Momentum Distribution (GTMD) $F_{14}$, and orbital angular momentum by exploring the underlying quark proton helicity amplitude structure. The twist three Generalized Parton Distribution (GPD) $\tilde{E}_{2T}$, was shown to connect to OAM. We study these functions using a diquark model calculation. The GTMD $F_{14}$ is unique in that it can describe both Jaffe-Manohar and Ji OAM depending on choice of gauge link, i.e. whether final state interactions are included or not. We perform a calculation of $F_{14}$ in both scenarios.