Gluon tomography from deeply virtual Compton scattering at small x

We present a full evaluation of the deeply virtual Compton scattering cross section in the dipole framework in the small-x region. The result features the cos phi and cos 2 phi azimuthal angular correlations, which have been missing in previous studies based on the dipole model. In particular, the cos 2 phi term is generated by the elliptic gluon Wigner distribution of which the measurement at the planned electron-ion collider provides important information about the gluon tomography at small x. We also show the consistency with the standard collinear factorization approach based on the quark and gluon generalized parton distributions.