Virtual QCD corrections to $gg\to ZZ$: top-quark loops from a transverse-momentum expansion

Abstract

We present the virtual corrections due to the top-quark loops for the process $gg\to ZZ$ at next-to-leading order in QCD. The associated two-loop box diagrams are computed using a small-transverse-momentum expansion. Our results are then merged with those available in the complementary energy region, obtained via a high-energy expansion, in order to provide an analytic result that is valid in the whole phase space. The results presented allow for an efficient modelling of the signal--background interference as well as the irreducible background in off-shell Higgs production.

Comments: 30 pages, 7 figures, 2 tables, 2 appendices