Hunting the Gluon Orbital Angular Momentum at the Electron-Ion Collider

TL;DR

This paper proposes a method to measure gluon orbital angular momentum in protons at the electron-ion collider by analyzing specific spin asymmetries in diffractive dijet production, providing a new way to understand proton spin structure.

Contribution

It introduces a novel approach linking Wigner distributions to gluon OAM via single spin asymmetries in hard scattering processes at the electron-ion collider.

Findings

Single longitudinal target-spin asymmetry is highly sensitive to gluon OAM.

Characteristic azimuthal angular correlation identified as $ ext{sin}(\phi_q -\phi_\Delta)$.

First potential measurement of gluon OAM in the proton spin sum rule.

Abstract

Applying the connection between the parton Wigner distribution and orbital angular momentum (OAM), we investigate the probe of the gluon OAM in hard scattering processes at the planned electron-ion collider. We show that the single longitudinal target-spin asymmetry in the hard diffractive dijet production is very sensitive to the gluon OAM distribution. The associated spin asymmetry leads to a characteristic azimuthal angular correlation of $\sin(\phi_q -\phi_\Delta)$, where $\phi_\Delta$ and $\phi_q$ are the azimuthal angles of the proton momentum transfer and the relative transverse momentum between the quark-antiquark pair. This study will enable a first measurement of the gluon OAM in the proton spin sum rule.