Interference effects for H → WW/ZZ l(v)over-barl(l)over-barvl searches in gluon fusion at the LHC

WW/ZZ interference for Higgs signal and continuum background as well as signal-background interference is studied for same-flavour l (v) over bar (l) (l) over barv(l) final states produced in gluon-gluon scattering at the LHC for light and heavy Higgs masses with minimal and realistic experimental selection cuts. For the signal cross section, we find WW/ZZ interference effects of O(5%) at MH = 126GeV. For MH >= 200GeV, we find that WW/ZZ interference is negligible. For the gg continuum background, we also find that WW/ZZ interference is negligible. As general rule, we conclude that non-negligible WW/ZZ interference effects occur only if at least one weak boson of the pair is dominantly off-shell due to kinematic constraints. The subdominant weak boson pair contribution induces a correction to the signal-background interference, which is at the few percentage point level before search selection cuts. Optimised selection cuts for M-H greater than or similar to 600GeV are suggested.