-- AnneCatherineLeBihan - 24-Apr-2012 -- CristinaFerro - 24-Apr-2012

TOP-11-004
Measurement of the ttbar production cross section in the tau-plus-jets channel in pp collisions at sqrt(s)=7 TeV

Abstract

This document presents a measurement of the top-antitop pair production cross section in proton-proton collisions at a center-of-mass energy of 7 TeV using data collected by the CMS experiment at the Large Hadron Collider. The measurement is performed in events with at least four energetic jets, at least one of them being b-tagged, and one hadronic tau candidate in the final state. The analysed data sample corresponds to an integrated luminosity of 3.9 fb−1 recorded by a dedicated multijet trigger including tau identification. A neural network has been developed to separate the top-antitop signal from the W-plus-jets and QCD multijet backgrounds. The measured value of σ(ttbar)=15612(stat.)33(sys.)3(lumi) pb is consistent with the standard model prediction.

Public Document

The document CMS-PAS-TOP-11-004 published on the CERN document server can be found here.

Figures

Neural network output variable

Figure Caption
NNoutput_log1_2.png Distribution of the neural network output variable after a fit of the signal and multijet processes to the data (logarithmic scale). [Get pdf version]
NNoutput_log0_2.png Distribution of the neural network output variable after a fit of the signal and multijet processes to the data (logarithmic scale). [Get pdf version]

Neural network input variables

Figure Caption
HT_2.png Distribution of the HT variable after a fit of the signal and multijet processes to the data. [Get pdf version]
Mtaujets.png Distribution of the invariant mass of the hadronic tau candidate and selected jets after a fit of the signal and multijet processes to the data. [Get pdf version]
Aplanarity.png Distribution of the aplanarity after a fit of the signal and multijet processes to the data. [Get pdf version]
qtauEta.png Distribution of the q*abs(eta(tau)) variable after a fit of the signal and multijet processes to the data. [Get pdf version]
Met.png Distribution of missing transverse energy after a fit of the signal and multijet processes to the data. [Get pdf version]
DeltaPhiTauMet.png Distribution of the Deltaphi(tau_h,MET) variable after a fit of the signal and multijet processes to the data. [Get pdf version]
Chi2KinFit.png Distribution of the chi2 returned by the semileptonic top kinematic fitter constraining the W and top masses after a fit of the signal and multijet processes to the data. [Get pdf version]

Multiplicity of the selected jets and M3 variable

Figure Caption
M3.png Distribution of the reconstructed M3 variable after a fit of the signal and multijet processes to the data. An additional cut on the NN output is applied, NN>0.5.[Get pdf version]
JetMultiplicity.png Multiplicity of the selected jets after a fit of the signal and multijet processes to the data. [Get pdf version]

Tables

Uncertainties on the final cross section measurement

Figure Caption
tab_N_evts.png Estimated number of signal and multijet events after a fit to the NN output distribution and expected contributions of the electroweak processes and ttbar backgrounds from simulation.[Get pdf version]
tab_sys_xsec.png Uncertainties on the final cross section measurement. [Get pdf version]

Topic attachments
I Attachment History Action Size Date Who Comment
PDFpdf Aplanarity.pdf r1 manage 21.2 K 2012-04-29 - 14:39 AnneCatherineLeBihan  
PNGpng Aplanarity.png r1 manage 78.7 K 2012-04-29 - 14:38 AnneCatherineLeBihan  
PDFpdf Chi2KinFit.pdf r1 manage 34.9 K 2012-04-29 - 14:39 AnneCatherineLeBihan  
PNGpng Chi2KinFit.png r1 manage 108.5 K 2012-04-29 - 14:39 AnneCatherineLeBihan  
PDFpdf DeltaPhiTauMet.pdf r1 manage 20.0 K 2012-04-29 - 14:40 AnneCatherineLeBihan  
PNGpng DeltaPhiTauMet.png r1 manage 73.2 K 2012-04-29 - 14:39 AnneCatherineLeBihan  
PDFpdf HT_2.pdf r1 manage 21.1 K 2012-04-27 - 22:49 AnneCatherineLeBihan  
PNGpng HT_2.png r1 manage 81.7 K 2012-04-27 - 22:49 AnneCatherineLeBihan  
PDFpdf JetMultiplicity.pdf r1 manage 17.4 K 2012-04-29 - 14:38 AnneCatherineLeBihan  
PNGpng JetMultiplicity.png r1 manage 68.5 K 2012-04-29 - 14:37 AnneCatherineLeBihan  
PDFpdf M3_zoom.pdf r1 manage 22.9 K 2012-04-29 - 15:25 AnneCatherineLeBihan  
PNGpng M3_zoom.png r1 manage 90.0 K 2012-04-29 - 15:26 AnneCatherineLeBihan  
PDFpdf Met.pdf r1 manage 30.8 K 2012-04-29 - 14:36 AnneCatherineLeBihan  
PNGpng Met.png r1 manage 102.2 K 2012-04-29 - 14:36 AnneCatherineLeBihan  
PDFpdf Mtaujets.pdf r1 manage 22.4 K 2012-04-29 - 15:49 AnneCatherineLeBihan  
PNGpng Mtaujets.png r1 manage 84.2 K 2012-04-29 - 15:49 AnneCatherineLeBihan  
PDFpdf NNoutput_log0_2.pdf r1 manage 23.3 K 2012-04-27 - 22:45 AnneCatherineLeBihan  
PNGpng NNoutput_log0_2.png r1 manage 82.7 K 2012-04-27 - 22:44 AnneCatherineLeBihan  
PDFpdf NNoutput_log1_2.pdf r1 manage 23.1 K 2012-04-27 - 22:47 AnneCatherineLeBihan  
PNGpng NNoutput_log1_2.png r1 manage 79.5 K 2012-04-27 - 22:46 AnneCatherineLeBihan  
PDFpdf qtauEta.pdf r1 manage 19.7 K 2012-04-29 - 14:35 AnneCatherineLeBihan  
PNGpng qtauEta.png r1 manage 72.7 K 2012-04-29 - 14:35 AnneCatherineLeBihan  
PDFpdf tab_N_evts.pdf r1 manage 43.5 K 2012-04-25 - 14:36 AnneCatherineLeBihan  
PNGpng tab_N_evts.png r1 manage 52.7 K 2012-04-25 - 14:35 AnneCatherineLeBihan  
PDFpdf tab_sys_xsec.pdf r1 manage 27.6 K 2012-04-25 - 14:25 AnneCatherineLeBihan  
PNGpng tab_sys_xsec.png r1 manage 77.9 K 2012-04-25 - 14:31 AnneCatherineLeBihan  
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Topic revision: r10 - 2012-06-29 - FelixHoehle
 
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