Gluon Generalized TMD signatures at the EIC from exclusive heavy (axial-)vector meson production

TL;DR

This paper proposes experimental signatures of gluon GTMDs in exclusive heavy meson production at the EIC, revealing new insights into the nucleon's spin and orbital structure through azimuthal asymmetries.

Contribution

It introduces a novel method to access gluon GTMDs via azimuthal asymmetries in exclusive meson production, highlighting their unique role in nucleon structure analysis.

Findings

Identification of azimuthal modulations sensitive to gluon GTMDs

Proposal of observables to measure gluon spin-orbit correlations

Demonstration of potential to study nucleon spin structure at EIC

Abstract

Potential experimental signatures of gluon generalized transverse momentum-dependent distributions (GTMDs) are proposed via exclusive heavy (axial-)vector meson production in lepton-proton collisions. Within the framework of collinear twist-3 factorization, we show that specific azimuthal-angle-dependent observables can provide sensitivity to the gluon GTMDs $F_{1,4}^g$ and $G_{1,1}^g$, which are related to partonic orbital angular momentum and spin-orbit correlations, respectively. These functions represent a unique sector of nucleon structure with no counterparts in the generalized parton distribution or transverse-momentum-dependent frameworks. We show that interference between different virtual-photon polarizations leads to distinct azimuthal modulations, including the polarization-independent $\cos 2\phi$ and polarization-dependent $\sin 2\phi$ terms, with $\phi$ defined as the angle between the lepton scattering plane and the hadron production plane. These observables provide signatures of the elusive gluon GTMDs $F_{1,4}^g$ and $G_{1,1}^g$, opening a new channel to access the spin structure of the nucleon at the future Electron-Ion Collider.