Electroweak ZZjj production in the Standard Model and beyond in the POWHEG-BOX V2

Barbara Jäger,Giulia Zanderighi,Alexander Karlberg

doi:10.1007/jhep03(2014)141

Barbara Jäger, Giulia Zanderighi + Show 1 more

Open Access

https://doi.org/10.1007/jhep03(2014)141

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Abstract

We present an implementation of electroweak $ZZjj$ production in the POWHEG BOX V2 framework, an upgrade of the POWHEG BOX program which includes a number of new features that are particularly helpful for high-multiplicity processes. We consider leptonic and semi-leptonic decay modes of the Z bosons, and take non-resonant contributions and spin correlations of the final-state particles into account. In the case of decays to leptons, we also include interactions beyond the Standard Model that arise from an effective Lagrangian which includes CP conserving and violating operators up to dimension six. We find that while leptonic distributions are very sensitive to anomalous couplings, because of the small cross-section involved, these analyses are feasible only after a high-luminosity upgrade of the LHC. We consider the cases of a 14 TeV, 33 TeV and 100 TeV machine and discuss the limits that can be placed on those couplings for different luminosities.

Highlights

We present an implementation of electroweak ZZjj production in the POWHEG BOX V2 framework, an upgrade of the POWHEG BOX program which includes a number of new features that are helpful for high-multiplicity processes
We have presented an implementation of electroweak ZZjj production in the POWHEG BOX V2, a framework for the matching of NLO-QCD calculations with partonshower programs
In the context of the Standard Model, we have considered the leptonic and semi-leptonic decay modes of the Z bosons

Summary

Technical details of the implementation

Our implementation of electroweak ZZjj production in the context of the POWHEG BOX proceeds along the same lines as previous work done for Zjj [16], W +W +jj [17], and W +W −jj production [18] via vector-boson fusion. To the cases of electroweak Zjj and W +W −jj production, the POWHEG BOX requires a prescription for dealing with singularities emerging in the Born cross section for pp → ZZjj via VBF One such type of singularities stems from collinear q → qγ configurations that emerge when a photon of low virtuality is exchanged in the t-channel. In VBF ZZjj production processes, an additional type of singular configurations is caused by diagrams with a quasi on-shell photon that decays into a fermion pair, γ⋆ → f f Such contributions can be identified by a small value of the invariant mass mff of the decay system. The full result is obtained by adding the results of the two separate contributions [17]

Phenomenological results

Standard Model results

Effective theory results

Findings

Conclusions