Signature of the gluon orbital angular momentum

TL;DR

This paper introduces a new observable based on azimuthal correlations in electron-proton scattering to detect gluon orbital angular momentum, enhancing understanding of proton spin structure.

Contribution

It proposes a novel experimental method using double spin asymmetry in dijet production to probe gluon OAM at small-x, with numerical estimates for EIC conditions.

Findings

The $ ext{cos} \, ext{phi}$ azimuthal correlation is sensitive to gluon OAM.

Numerical estimates suggest measurable cross sections at EIC.

The method links gluon OAM to observable asymmetries in exclusive processes.

Abstract

We propose a novel observable for the experimental detection of the gluon orbital angular momentum (OAM) that constitutes the proton spin sum rule. We consider longitudinal double spin asymmetry in exclusive dijet production in electron-proton scattering and demonstrate that the $\cos \phi$ azimuthal angle correlation between the scattered electron and proton is a sensitive probe of the gluon OAM at small-$x$ and its interplay with the gluon helicity. We also present a numerical estimate of the cross section for the kinematics of the Electron-Ion Collider.