We calculate the inclusive single-gluon production cross section in high
energy onium-onium scattering including pomeron loop effects. The resulting
inclusive cross section is given by the k_T-factorization formula with one of
the unintegrated gluon distribution functions depending on the total
onium-onium scattering cross section, which includes all pomeron loops and has
to be found independently. We discuss the limits of applicability of our result
and argue that they are given by the limits of applicability of pomeron loop
resummation approach. Since the obtained k_T-factorization formula is infrared
divergent we conclude that, in order to consistently calculate the
(infrared-finite) gluon production cross section in onium-onium scattering, one
has to include corrections going beyond the pomeron loop approximation.Comment: 20 pages, 6 figures; v2: version accepted to Phys. Rev. D, minor
corrections include