Spectrum of diffractively produced gluons in onium–nucleus collisions

We calculate spectrum of diffractively produced gluons in onium–heavy nucleus collisions at high energies. We show that it exhibits a characteristic dependence on nucleus atomic number A and energy/rapidity. We argue that this dependence offers a unique possibility for determining the low-x structure of nuclear matter. Applications to RHIC, LHC and EIC experimental programs are discussed.