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.
Highlights
JHEP02(2016)131 to reproduce data, is vital for many new-physics searches, which are very often heavily reliant on theoretical predictions, and categorised in terms of jet multiplicities
We report the predictions for the total rates that result from the FxFx-merged and the fully-inclusive samples; the latter are, by construction in the MC@NLO formalism, equal to those one obtains with fixed-order computations — the Pythia8 and Herwig++ results in the last column agree to a 0.05% level, which is the statistical inaccuracy one expects from a 5M-event sample
In this paper we have presented a comprehensive comparison between NLO+PS theoretical predictions obtained by merging different partonic multiplicities according to the FxFx method, and several measurements performed by ATLAS and CMS for the leptonic channels of Z+jets and W+jets production
Summary
Central hard-scale choice: μ0 = HT /2, with HT the scalar sum of the transverse masses p2T + m2 of all final state particles In merged samples, this is computed by using the 2 → V + 1 process reconstructed by clustering back the given kinematic configuration; on top of that, an αS reweighting is performed — see ref. Since neither of them has been obtained with NNPDF2.3 NLO PDFs, the quality of the comparisons to low-pT data might be degraded w.r.t. one performed by using the MCs standalone in conjuction with the same PDFs as in the tunes While this is a common issue with NLO+PS simulations, and one that will be addressed possibly only in the context of a genuine NLO tune, the impact on Z+jets and W+jets observables is expected, and will be shown, to be rather minimal.
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