GLUON PROPAGATOR IN BACKGROUND FIELD AT NEXT-TO-EIKONAL ORDER

Studying high-energy hadronic scattering processes to understand the structure of nuclei has been the focus of experimental and theoretical studies for more than three decades now. The Color Glass Condensate effective theory has been developed and used to study high-energy proton- nucleus collisions in particular. One of the main approximations adopted in the Color Glass Condensate is the so-called eikonal approximation, which amounts to neglecting power-suppressed corrections in the high-energy limit. This approximation is well justified for asymptotically high energies, however, corrections to it might be sizable in practice, in particular at the Relativistic Heavy Ion Collider and upcoming Electron Ion Collider. Here, we will briefly review the eikonal approximation and present the computation of a gluon propagator through the target at next-to-eikonal accuracy. Furthermore, we will present its application to gluon production in proton- nucleus collisions.