Double spin asymmetries at small-x from exclusive vector meson production

A chief aim of the Electron-Ion Collider (EIC) is to probe the origin of the proton's spin. Decades ago, experiments revealed that the proton's total spin cannot be explained by a simple three-quark model. This "spin crisis" suggests that gluon dynamics play a critical role in generating proton spin, especially at small‑x where gluons dominate the proton's structure. Exclusive vector meson (VM) production from polarized electron‑proton collisions provides a clean probe of gluons in this regime. To uncover the spatial distributions of these gluons and how they contribute to proton spin, we analyzed double-spin asymmetries in exclusive VM production, a novel observable sensitive to Generalized Parton Distributions (GPDs). We isolate helicity and polarization structures, compute the asymmetries, and map different structure functions to GPDs in the leading‑twist approximation. This work lays the foundation for future numerical predictions to assess the experimental feasibility of these measurements at the EIC.