Interference effects for H → W W → ℓ ν q q ¯ ′ $$ H\to W\;W\to \ell \nu q{\overline{q}}^{\prime } $$ and H → Z Z → ℓ ℓ ¯ q q ¯ $$ H\to ZZ\to \ell \overline{\ell}q\overline{q} $$ searches in gluon fusion at the LHC

Abstract

Signal-background interference effects are studied for H → W W and H → ZZ searches in gluon fusion at the LHC. More specifically, the interference in the channels with semileptonic weak boson pair decay is analysed for light and heavy Higgs masses with minimal and realistic experimental selection cuts. In the semileptonic decay modes, the interference is affected by tree-level background contributions enhanced by 1/e 2 relative to the gluon-fusion continuum background in the fully leptonic decay modes. We find that for both light and heavy Higgs masses the interference with the loop-induced weakboson pair background dominates over the interference with the tree-level weak-boson plus jets background for a range of selection cuts. We therefore conclude that higherorder background contributions can induce leading interference effects. With appropriate background suppression cuts the interference can be reduced to the 10% level for heavy Higgs masses, and to the per mille level for the light SM Higgs.

Heavy Higgs signal–background interference in $$gg\rightarrow VV$$ g g → V V in the Standard Model plus real singlet

“…[26], which were calculated using a previous version of gg2VV with a different phase space implementation based on a decomposition into sections. Furthermore, results for similar processes calculated using the same code show excellent agreement with a fully independent implementation [79].…”

ZZ production at the LHC: NNLO predictions for 2ℓ2ν and 4ℓ signatures

“…ZZ+jet production was computed at NLO QCD [27]. The loop-induced gg → ZZ + X subprocess, which provides a separately finite O(α 2 S ) contribution, is known at leading order (LO) [28][29][30][31][32][33][34][35][36][37] and was recently computed at NLO considering only gg-initiated partonic channels [38][39][40], using the two-loop helicity amplitudes for gg → V V of Refs. [41,42].…”

Higgs interference effects at the one-loop level in the 1-Higgs-Singlet extension of the Standard Model

“…[62], for which results are not yet available. We believe this tree-2-loop contribution is small compared to the 1-loop-1-loop contribution we compute, because tree-1-loop interference was found to be small compared to 1-loop-1-loop interference in similar processes [67,92], but the non-factorisable contribution may be enhanced due to the lifted colour singlet final state restriction. 13 In the inclusive case, nonfactorisable corrections are suppressed by Γt/mt, i.e.…”

“…(3.5), since our study focuses on the region with 2m t < M tt < M h 2 , the double pole approximation [91] with a pair of on-shell top quark states -shown in red in figure 3 -is applied to simplify our calculations. It has been shown that higher-order corrections to interference can be larger than the interference at LO [66,67]. In the case where LO involves treelevel amplitudes, this can be understood as follows: the relative phase that induces large interference arises primarily through the absorptive part of loop graphs.…”

“…Significantly, we investigate the impact of higher-order corrections on the Higgs signal by accurately taking into account its interference with the virtual corrections to the gg → tt continuum background. 5 Due to a non-trivial phase, loop-level amplitude contributions can substantially change integrated cross sections and the shapes of differential cross sections [66][67][68]. Furthermore, it is wellknown that "flat" inclusive K-factors often do not model differential NLO corrections well.…”