Abstract
Pair production of Z bosons in association with a hard jet is an important background for Higgs particle or new physics searches at the LHC. The loop-induced gluon-fusion process gg > ZZg contributes formally only at the next-to-next-to-leading order. Nevertheless, it can get enhanced by the large gluon flux at the LHC, and thus should be taken into account in relevant experimental searches. We provide the details and results of this calculation, which involves the manipulation of rank-5 pentagon integrals. Our results show that the gluon-fusion process can contribute more than 10% to the next-to-leading order QCD result and increases the overall scale uncertainty. Moreover, interference effects between Higgs and non-Higgs contributions can become large in phase-space regions where the Higgs is far off-shell.
Highlights
A similar study for the W boson case shows contributions of about 10 percent to the next-toleading order QCD result [5]
Since we are mostly interested in the effects of the integrated cross section of ZZ + j production in GF, which is not sensitive to the Z decays, in accordance with Ref. [3], the leptonic decay of the Z bosons and off-shell effects, e.g. γ∗ → l+l−, are not considered
The two diagrams in the bottom row both involve a, possibly virtual, Higgs boson, which decays into a Z pair
Summary
A similar study for the W boson case shows contributions of about 10 percent to the next-toleading order QCD result [5]. Final results will be given with program 2 without imposing the KT cut and activating the two rescue systems demanding a global accuracy of the Ward identities of ǫ = 10−3.
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