StandardModelCSCResultsWZJets

Introduction

This page provides information and plots for W/Z+jets studies from ATLAS CSC book, as published in ATLAS Collaboration, Expected Performance of the ATLAS Experiment, Detector, Trigger and Physics, Geneva 2008. CERN-OPEN-2008-020, ISBN978-92-9083-321-5, arXiv:0901.0512v1 [hep-ex].

Production of Jets in Association with Z Bosons

Abstract

We simulate a measurement of the inclusive Z(->e+e-/m+m-) + jets cross-section with the ATLAS experiment in pp collisions at 14 TeV for an integrated luminosity of 1 fb-1 using fully-simulated signal and background Monte Carlo data sets. The reconstruction of leptons and of missing transverse energy becomes more complex in the presence of a multi-jet final state. We quantify the reconstruction differences with respect to those observed for inclusive Z production. We derive statistical and systematic limitations in terms of probing the perturbative QCD predictions and discriminating between predictions of different event generators.

Measurement of Z + jets Cross-Sections

SM_invmass_new81101 SM_njets_new81101 Ana_Jpt0 Ana_Jpt1

Caption Figure 1: The distribution of the di-muon mass (a) and the inclusive jet multiplicity (b) for signal and backgrounds in the muon channel. In order to provide higher statistics for the background determination, background events in an invariant mass window of 51−131 GeV, are scaled down for an invariant mass window of 81−101 GeV. Also shown is the distribution of pT of the leading (c) and the next-to-leading (d) jet in the electron channel for Ldt = 1 fb-1. The vertical lines in (a), (c) and (d) indicate the kinematic cuts applied in the analysis.

AlpJpt0CorrLin AlpJpt1CorrLin

Caption Figure 2: Comparison of the distribution of the pT of the leading jet (a) and the next-to-leading jet (b) for the generated (hadron-level) Monte Carlo and for the reconstructed quantities without any correction, after the corrections for electron triggering and reconstruction and after applying in addition the jet-releated corrections.

10njetsmcfmtruth 11leadjettruthmcfm 11lead2jettruthmcfm

Caption Figure 3: Comparison of the inclusive jet cross-section (a) and the pT of the leading jet (b) and of the next-to-leading jet (c) for the Z -> m+m- +jets channel from PYTHIA and ALPGEN Monte Carlo with NLO (LO) MCFM predictions. The MCFM predictions have been corrected to the hadron level.

Res_Njet_Reco Res_Jpt0_Reco

Caption Figure 4: The inclusive jet cross-section (a) and the distribution of the pT of the leading jet (b), as predicted by NLO (LO) MCFM (corrected to the hadron-level) and by ALPGEN for the Z -> e+e- +jets process.

JES_Error_All JES_Pt_Error_All

Caption Figure 5: Uncertainty on the ratio of measurement and theory for the inclusive jet cross-section (a) and the pT of the leading jet (b) for the Z -> e+e- +jets process.

Results Tables

Process σ (fb) frac(%) σ (fb) frac(%) σ (fb) frac(%)
Z->ll+ >=1 jet Z->ll+ >=2 jet Z->ll+ >=3 jet
Z->e+e- + jets analysis
Z->e+e- 23520145 91.90.8 489445 87.91.3 90015 80.02.4
QCD jets 154589 6.00.4 33642 6.00.8 7820 6.91.8
ttbar 49628 1.90.1 33323 6.00.4 14615 13.01.4
W->eν (2813) (0.10.05) (5.92.6) (0.10.05) (1.10.5) (0.10.05)
Z->ττ 3.21.2 0.010.01 (0.670.25) (0.010.01) (0.10.05) (0.010.01)
Z->μ+μ- + jets analysis
Z->μ+μ- 59400650 96.21.0 12600300 90.11.9 2450100 89.73.7
QCD (bbar) 1230550 2.00.9 600300 4.32.2 0110 0.04.0
ttbar 1140110 1.81.8 79090 5.70.2 27550 10.21.9
W->μν 0180 0.00.3 030 0.00.2 05 0.00.2

Caption Table 1: The accepted cross-sections (σ , in fb) and the corresponding fraction of the total sample (in %) for signal and for the background channels in the Z->e+e- +jets and the Z->μ+μ- +jets analyses, after applying the cuts outlined in Section 3. The numbers in brackets are extrapolated from results obtained for a lower jet multiplicity. Errors shown are statistical only.


Major updates:
-- StefanTapprogge - 5 Dec 2008 -- AlessandroTricoli - 12 Jan 2009

Responsible: AlessandroTricoli
Last reviewed by: -- AlessandroTricoli - 12 Jan 2009

Topic attachments
I Attachment History Action Size Date Who Comment
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JPEGjpg Ana_Jpt0.jpg r1 manage 19.5 K 2008-12-19 - 16:01 AlessandroTricoli  
PNGpng Ana_Jpt0.png r1 manage 15.6 K 2008-12-19 - 12:47 AlessandroTricoli Zee pt 1st jet
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JPEGjpg Ana_Jpt1.jpg r1 manage 17.8 K 2008-12-19 - 16:35 AlessandroTricoli  
PNGpng Ana_Jpt1.png r1 manage 16.0 K 2008-12-19 - 12:50 AlessandroTricoli Zee pt 2nd jet
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JPEGjpg JES_Error_All.jpg r1 manage 21.6 K 2008-12-19 - 16:01 AlessandroTricoli  
PNGpng JES_Error_All.png r1 manage 20.7 K 2008-12-19 - 14:40 AlessandroTricoli Uncertainty on the inclusive jet cross-section
Unknown file formateps JES_Pt_Error_All.eps r1 manage 35.4 K 2008-12-19 - 14:43 AlessandroTricoli Uncertainty on the PT of the leading jet
JPEGjpg JES_Pt_Error_All.jpg r1 manage 27.0 K 2008-12-19 - 16:01 AlessandroTricoli  
PNGpng JES_Pt_Error_All.png r1 manage 27.7 K 2008-12-19 - 14:43 AlessandroTricoli Uncertainty on the PT of the leading jet
Unknown file formateps Res_Jpt0_Reco.eps r1 manage 15.2 K 2008-12-19 - 14:35 AlessandroTricoli Leading jet
JPEGjpg Res_Jpt0_Reco.jpg r1 manage 14.0 K 2008-12-19 - 16:02 AlessandroTricoli  
PNGpng Res_Jpt0_Reco.png r1 manage 15.7 K 2008-12-19 - 14:36 AlessandroTricoli Leading jet
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JPEGjpg Res_Njet_Reco.jpg r1 manage 13.5 K 2008-12-19 - 16:02 AlessandroTricoli  
PNGpng Res_Njet_Reco.png r1 manage 14.7 K 2008-12-19 - 14:32 AlessandroTricoli Inclusive jet multiplicity
JPEGjpg SM_invmass_new81101.jpg r1 manage 17.7 K 2008-12-19 - 16:59 AlessandroTricoli  
PNGpng SM_invmass_new81101.png r1 manage 13.4 K 2008-12-19 - 12:34 AlessandroTricoli Zmumu Invariant Mass
Unknown file formateps SM_njets_new81101.eps r1 manage 649.6 K 2008-12-19 - 17:00 AlessandroTricoli  
JPEGjpg SM_njets_new81101.jpg r1 manage 11.8 K 2008-12-19 - 17:00 AlessandroTricoli  
PNGpng SM_njets_new81101.png r1 manage 10.4 K 2008-12-19 - 12:40 AlessandroTricoli Zmumu njets
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Topic revision: r7 - 2009-10-23 - AlessandroTricoli
 
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