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A study of multi-jet production in association with an electroweak vector boson

Rikkert Frederix, Stefano Frixione, Andreas Papaefstathiou, Stefan Prestel, Paolo Torrielli

TL;DR

This study validates the FxFx NLO merging formalism for vector-boson plus jets by comparing MadGraph5_aMC@NLO FxFx-merged samples, showered with $Herwig++$ or $Pythia8$, to 7 TeV ATLAS/CMS data across $Z$+jets and $W$+jets channels. The results show that NLO merging with up to two additional partons improves agreement with data and reduces dependence on the shower model, delivering reliable predictions for jet multiplicities and kinematic distributions. A careful treatment of uncertainties from renormalization/factorization scales, PDFs, and the merging scale $\mu_Q$ demonstrates that the FxFx approach provides robust, predictive results without ad hoc rescaling. The findings support the use of NLO merged samples for precision V+jets studies and motivate extension to higher multiplicities and Higgs-associated processes in future LHC analyses.

Abstract

We consider the production of a single $Z$ or $W$ boson in association with jets at the LHC. We compute the corresponding cross sections by matching NLO QCD predictions with the Herwig++ and Pythia8 parton showers, and by merging all of the underlying matrix elements with up to two light partons at the Born level. We compare our results with several 7-TeV measurements by the ATLAS and CMS collaborations, and overall we find a good agreement between theory and data.

A study of multi-jet production in association with an electroweak vector boson

TL;DR

This study validates the FxFx NLO merging formalism for vector-boson plus jets by comparing MadGraph5_aMC@NLO FxFx-merged samples, showered with or , to 7 TeV ATLAS/CMS data across +jets and +jets channels. The results show that NLO merging with up to two additional partons improves agreement with data and reduces dependence on the shower model, delivering reliable predictions for jet multiplicities and kinematic distributions. A careful treatment of uncertainties from renormalization/factorization scales, PDFs, and the merging scale demonstrates that the FxFx approach provides robust, predictive results without ad hoc rescaling. The findings support the use of NLO merged samples for precision V+jets studies and motivate extension to higher multiplicities and Higgs-associated processes in future LHC analyses.

Abstract

We consider the production of a single or boson in association with jets at the LHC. We compute the corresponding cross sections by matching NLO QCD predictions with the Herwig++ and Pythia8 parton showers, and by merging all of the underlying matrix elements with up to two light partons at the Born level. We compare our results with several 7-TeV measurements by the ATLAS and CMS collaborations, and overall we find a good agreement between theory and data.

Paper Structure

This paper contains 7 sections, 1 equation, 47 figures, 2 tables.

Table of Contents

  1. Introduction and motivation
  2. Technicalities and settings
  3. Comparison to data
  4. $Z\!+\!{\rm jets}$
  5. $W\!\!+\!{\rm jets}$
  6. Inclusive observables
  7. Summary

Figures (47)

  • Figure 1: Exclusive jet multiplicity. Data from ref. Aad:2013ysa, compared to Herwig++ (left panel) and Pythia8 (right panel) predictions. The FxFx uncertainty envelope ("Var") and the fully-inclusive central result ("inc") are shown as green bands and red histograms respectively. See the end of sect. \ref{['sec:tech']} for more details on the layout of the plots.
  • Figure 2: As in fig. \ref{['fig:Z.1304.7098:03']}, for the transverse momentum of the 1$^{st}$ jet.
  • Figure 3: As in fig. \ref{['fig:Z.1304.7098:03']}, for the transverse momentum of the 3$^{rd}$ jet.
  • Figure 4: As in fig. \ref{['fig:Z.1304.7098:03']}, for the transverse momentum of the 4$^{th}$ jet.
  • Figure 5: As in fig. \ref{['fig:Z.1304.7098:03']}, for the rapidity of the 1$^{st}$ jet.
  • ...and 42 more figures