In these proceedings we present results from a recent calculation for the
production of a W boson in conjunction with five jets at next-to-leading order
in perturbative QCD. We also use results at lower multiplicities to extrapolate
the cross section to the same process with six jets.Comment: 5 pages, Proceedings for the DIS2013 conferenc

Bern, Z.

Cordero, F. Febres

Dixon, L. J.

Höche, S.

Ita, H.

Kosower, D. A.

Maître, D.

Ozeren, K. J.

English

arXiv

Dixon, L.J.

Cordero, F.Febres

Hoche, S.

Kosower, D.A.

Ozeren, K.J.

Maitre, D.

UNT (University of North Texas) Digital Library

High multiplicity W+jets predictions at NLOD. Maître∗Institute for Particle Physics Phenomenology, University of Durham, Durham DH1 3LE, UKE-mail: daniel.maitre@durham.ac.ukZ. BernDepartment of Physics and Astronomy, UCLA, Los Angeles, CA 90095-1547, USAE-mail: bern@physics.ucla.eduL. J. DixonSLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94309, USAE-mail: lance@slac.stanford.eduF. Febres CorderoDepartamento de Física, Universidad Simón Bolívar, Caracas 1080A, VenezuelaE-mail: ffebres@usb.veS. HöcheSLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94309, USAE-mail: shoeche@slac.stanford.eduH. ItaPhysikalisches Institut, Albert-Ludwigs-Universität Freiburg, D–79104 Freiburg, GermanyE-mail: harald.ita@physik.uni-freiburg.deD. A. KosowerInstitut de Physique Théorique, CEA–Saclay, F–91191 Gif-sur-Yvette cedex, FranceE-mail: david.kosower@cea.frK. J. OzerenDepartment of Physics and Astronomy, UCLA, Los Angeles, CA 90095-1547, USAE-mail: ozeren@physics.ucla.eduB/F/421–13 IPPP/13/62 SLAC–PUB–15709UCLA–13–TEP–105 IPhT–T13/205In these proceedings we present results from a recent calculation for the production of a W bosonin conjunction with five jets at next-to-leading order in perturbative QCD. We also use results atlower multiplicities to extrapolate the cross section to the same process with six jets.XXI International Workshop on Deep-Inelastic Scattering and Related Subject -DIS2013,22-26 April 2013Marseilles,France∗Speaker.c© Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence. http://pos.sissa.it/Work supported by US Department of Energy under contract DE-AC02-76SF00515 and HEP.Published in arXiv:1308.3986.W+jets at NLO D. Maître1. IntroductionThe production of a vector boson in conjunction with jets is an important benchmark processfor experiments at hadron colliders. Reliable predictions for these processes are needed both as atest of our understanding of Standard-Model measurements and because they represent importantbackgrounds to many searches for physics beyond the Standard Model (BSM). The study of thenewly discovered Higgs-like boson [1, 2] and searches for BSM signals requires good modeling ofhigh-multiplicity final states. The same holds true for Standard-Model processes such as top-pairand di-boson production, for which W+multijet processes represent an important background. Be-cause the neutrino from the leptonic decay of the W boson escapes the dectector, W+jets processesrepresent an irreducible background for many searches involving missing transverse energy.Next-to-leading order (NLO) in the strong coupling constant is the lowest order at whichreliable quantitative predictions for cross sections are possible. Theoretical predictions for theproduction of a W boson in assoctiation with up to two jets at NLO have been available for a longtime [3, 4, 5]. At higher multiplicities, predictions have become available only in recent years: theso-called unitarity method (for a review, see Refs. [6, 7]) has been used successfully for W -bosonproduction in association with three [8], four [9] and most recently five jets [10].Vector boson production has been measured in association with up to four jets at the LHC witha center of mass energy of 7 TeV [11, 12] and good agreement was found with NLO predictions.2. W+jets at NLOWe use SHERPA [13] in association with the virtual matrix elements from BLACKHAT [14]to obtain our NLO predictions. We apply the jet and lepton cuts given in Ref. [10]. The resultsfor the total cross sections for W + 1-jet through W + 5-jet production are given in table 1 of [10].In Figure 1 we present the transverse momentum distribution of the leading five jets. The strikingfeature is the reduction of the scale variation obtained by going from LO to NLO. One can alsosee that the radiative corrections affect not only the overall normalization but also the shape ofdistributions.Given that cross sections σn are now available for a large number of jet multiplicities n, onecan investigate several ratios involving these processes, which are interesting because some sourcesof uncertainties largely cancel, both on the experimental and theoretical side. The jet productionand charge asymmetry ratios are defined asRW±n/(n−1) =σ(W±+n jets)σ(W±+(n−1) jets) , RW+/W− =σ(W++n jets)σ(W−+n jets),repectively. Excluding the case n = 2 where new partonic channels open in the denominator, bothratios can be consistently described using a linear interpolation, both at LO and NLO.We collect the coefficients of the interpolation R = an+b for both ratios in the following table.aLO bLO aNLO bNLORW+n/(n−1) −0.0177±0.0004 0.320±0.002 −0.009±0.003 0.263±0.009RW−n/(n−1) −0.0165±0.0005 0.301±0.002 0.009±0.002 0.248±0.008RW+/W− 0.102±0.002 1.347±0.006 0.11±0.01 1.27±0.032W+jets at NLO D. MaîtreFigure 1: The pT distributions of the leading five jets in W−+ 5-jet production at the LHC at√s = 7 TeV. Inthe upper panels, the NLO predictions are shown as solid (black) lines, while the LO predictions are shownas dashed (blue) lines. The lower panels show the predictions for the LO distribution and scale-dependencebands normalized to the NLO prediction (at the scale µ = Ĥ ′T/2). The LO distribution is the dashed (blue)line, and the scale-dependence bands are shaded (gray) for NLO and cross-hatched (brown) for LO.1 2 3 4 5 6 70.180.200.220.240.260.280.300.32Jet production ratioW− LOW− NLOW+ LOW+ NLO0 1 2 3 4 5 61.31.41.51.61.71.81.92.0Charge ratioW+/W− LOW+/W− NLOFigure 2: Linear fits for the jet production and charge asymmetry ratios.Using this linear regression one can extrapolate to obtain a prediction for the W + 6-jet crosssection:σextr(W++6 jets) = 0.30±0.03 pb ,σextr(W−+6 jets) = 0.15±0.01 pb .Englert et al. recently investigated [15] such an extrapolation using jet calculus methods, and foundit to be a good approximation when the jets are required to have the same minimum transversemomenta. In our extrapolation, the errors are computed from the variance of a large set of synthetic3W+jets at NLO D. Maîtredata distributed in Gaussians around the central values of the cross sections, with widths set to thecorresponding Monte-Carlo statistical errors. The procedure is illustrated in Fig 3.Figure 3: Extrapolation of the jet production ratio. The error of the extrapolation is estimated from thevariance of a synthetic set of linear extrapolations based on synthetic input data distributed in a gaussianaround the central values with the width given by the statistical error. Each line represents one of these fits.3. ConclusionsWe have presented results from a NLO calculation for the production of a W boson in associ-ation with up to five jets. We used these results to provide an extrapolation for the cross section ofthe corresponding process with six jets.AcknowledgmentsThis research was supported by the US Department of Energy under contracts DE–FG03–91ER40662 and DE–AC02–76SF00515. DAK’s research is supported by the European ResearchCouncil under Advanced Investigator Grant ERC–AdG–228301. DM’s work was supported by theResearch Executive Agency (REA) of the European Union under the Grant Agreement numberPITN–GA–2010–264564 (LHCPhenoNet). The work of KJO and SH was partly supported bya grant from the US LHC Theory Initiative through NSF contract PHY–0705682. This researchused resources of Academic Technology Services at UCLA, and of the National Energy ResearchScientific Computing Center, which is supported by the Office of Science of the U.S. Departmentof Energy under Contract No. DE–AC02–05CH11231.References[1] S. Chatrchyan et al. [CMS Collaboration], Phys. Lett. B 716, 30 (2012) [arXiv:1207.7235 [hep-ex]].[2] G. Aad et al. [ATLAS Collaboration], Phys. Lett. B 716, 1 (2012) [arXiv:1207.7214 [hep-ex]].4W+jets at NLO D. Maître[3] P. B. Arnold and M. H. Reno, Nucl. Phys. B 319, 37 (1989) [Erratum-ibid. B 330, 284 (1990)];P. B. Arnold, R. K. Ellis and M. H. 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High Multiplicity W Jets Predictions at NLO

High multiplicity W+jets predictions at NLO

High multiplicity W+jets predictions at NLO

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