Abstract
We consider ZZ production in hadronic collisions and present state-of-the-art predictions in QCD perturbation theory matched to parton showers. Next-to-next-to-leading order corrections to the quark-initiated channel are combined with parton showers using the MiNNLOPS method, while next-to-leading order corrections to the loop-induced gluon fusion channel are matched using the Powheg method. Their combination, dubbed nNNLO+PS, constitutes the best theoretical description of ZZ events to date. Spin correlations, interferences and off-shell effects are included by calculating the full process pp → ℓ+ℓ−ℓ(′)+ℓ(′)−. We show the crucial impact of higher-order corrections for both quark- and gluon-initiated processes as well as the relevance of the parton shower in certain kinematical regimes. Our predictions are in very good agreement with recent LHC data.
Highlights
Our phenomenological results for both cross sections and distributions in ZZ production are discussed in section 3, where we present a comparison between showered, fixed-order, and analytically resummed results at high accuracy for various observables as well as a comparison of our nNNLO+PS predictions to recent LHC data from CMS
In the following we provide some information on our implementation of a MiNNLOPS generator for ZZ production in the qqchannel within the Powheg-Box-Res framework [114]
When comparing the MiNNLOPS and the MiNLO predictions for the pT,e− spectrum we observe that the effect of both the NNLOqqcorrections and the loop-induced gg contribution is pronounced in the bulk region of the distribution, where the MiNLO result is more than 20% smaller than the nNNLO result
Summary
For any combination of charged leptons , ∈ {e, μ, τ }. The loop-induced gg contribution, including the single-resonant Higgs mediated diagrams, proceeds through a quark loop and enters the cross section at O(αs2), i.e. it is part of the NNLO QCD corrections. We calculate NNLO+PS predictions in the qqchannel by means of the MiNNLOPS method [106,107,108] and NLO+PS predictions in the loop-induced gg channel using the Powheg approach [111,112,113]. Tation of the NNLO+PS calculation in the qqchannel does not include the loop-induced gg-initiated contribution In this way, all loop-induced gg contributions are correctly accounted for when combining the former with our NLO+PS predictions for the gg channel. We present the implementation of a NNLO+PS generator for ZZ production in the qqchannel by means of the MiNNLOPS method. We first sketch the MiNNLOPS method by introducing its essential ingredients and discuss its practical implementation within the Powheg-Box-Res framework [114] and linking Matrix [115]
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