Abstract

This publication presents the combination of the one-loop matrix-element generator Recola with the multipurpose Monte Carlo program Sherpa. Since both programs are highly automated, the resulting Sherpa +Recola framework allows for the computation of – in principle – any Standard Model process at both NLO QCD and EW accuracy. To illustrate this, three representative LHC processes have been computed at NLO QCD and EW: vector-boson production in association with jets, off-shell mathrm{Z}-boson pair production, and the production of a top-quark pair in association with a Higgs boson. In addition to fixed-order computations, when considering QCD corrections, all functionalities of Sherpa, i.e. particle decays, QCD parton showers, hadronisation, underlying events, etc. can be used in combination with Recola. This is demonstrated by the merging and matching of one-loop QCD matrix elements for Drell–Yan production in association with jets to the parton shower. The implementation is fully automatised, thus making it a perfect tool for both experimentalists and theorists who want to use state-of-the-art predictions at NLO accuracy.

Highlights

  • Three representative LHC processes have been computed at NLO QCD and EW: vector-boson production in association with jets, off-shell Z-boson pair production, and the production of a top-quark pair in association with a Higgs boson

  • NLO QCD validation: The Sherpa+Recola interface has been cross-checked for this process against the independent private Monte Carlo program that had been used for the computations in Refs. [23,24,26,27]

  • The results for the jet-associated Drell–Yan process based on Sherpa+Recola presented here confirm related comparisons of simulations based on NLO QCD matrix elements matched with QCD parton showers with data, see e.g. Refs. [74,75]

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Summary

Details of the implementation

We present some details of the techniques and algorithms used in both Sherpa and Recola, as well as information on the interface between them. For a detailed description of the methods employed by these programs, the reader is invited to explore the references given below

The Sherpa framework
The matrix-element generator Recola
The interface
NLO QCD validation
Phase-space point comparison
NLO QCD fixed-order calculations
Z-boson production in association with jets
Z-boson pair production
Higgs production in association with a top-quark pair
Higgs-boson production in association with a Z boson
Matching to parton shower
NLO EW validation and combined predictions
Vector-boson production in association with jets
Conclusion
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