Deeply virtual Compton scattering (DVCS) is a powerful channel to study the spatial structure of protons and nuclei at the future Electron-Ion Collider (EIC). In the collinear framework, DVCS is dependent on the quark and gluon generalized parton distributions (GPDs). At small x, these objects are closely related to the dipole correlator of Wilson Lines .
It is well known that the transverse momentum spectrum of DVCS at small x gives access to the impact parameter dependence of the dipole correlator. In , it was shown that by studying the azimuthal anisotropies of the final state photon with the electron plane in DIS one could also access the angular dependence of the dipole correlator. This information is crucial to unveil the structure of the orbital angular momentum carried by gluons inside hadrons and nuclei.
In this talk, I will review the computation of DVCS at leading order in the CGC EFT, including the azimuthal angular correlations with respect to the electron plane. Then, I will show how to obtain similar expressions for exclusive vector meson production. I will then present our predictions for these anisotropies in electron-proton and electron-gold collisions for the kinematics of the future EIC. Finally, I will discuss the potential to measure the angular structure of color charge and geometric fluctuations in incoherent diffractive production. This talk is based on .
 Probing the Small-x Gluon Tomography in Correlated Hard Diffractive Dijet Production in DIS. arXiv:1601.01585
 Gluon Tomography from Deeply Virtual Compton Scattering at Small-x. Y. Hatta, B-W. Xiao, and F. Yuan. arXiv:1703.02085
 Gluon imaging using azimuthal correlations in diffractive scattering at the Electron-Ion Collider. H. Mäntysaari, K. Roy, F. Salazar, and B. Schenke. arXiv:2011.0246.