TOP-12-015: Measurement of W-Polarization in Di-Leptonic ttbar Events in pp collisions with sqrt(s)=7 TeV


We present a measurement of the W boson helicity fractions in ttbar events with the full dataset collected by the CMS detector in 2011 at a center-of-mass energy of sqrt(s) =7 TeV. This corresponds to an integrated luminosity of 4.6/fb . The analysis is based on the dilepton decay channel of top pair events , in which both W bosons decay leptonically. Only events containing electrons and/or muons in the final state are considered. We measure the fractions of left-handed, longitudinal, and right-handed W boson to be FL = 0.288 0.035(stat) 0.040(sys) , F0 = 0.698 0.057(stat) 0.063(sys) and FR = 0.014 0.027(stat) 0.042(sys). The results are consistent with the standard model predictions.


Tables Caption
cutFlowTable.png Table 1 : Event yields for MC samples and data after applying cut, simulated events are normalized to the integrated luminosity of the data sample. The last column represents the number of events with reconstructed top and anti-top. The quoted errors are statistical uncertainties.

sysTable.png Table 2 : Summary of the systematic uncertainties for combined channels using 3D fit.


Figure Caption
NBjets_beforeMET.png Distributions of the number of reconstructed b-tagged jets before applying the cut on MET. [pdf]

NBjets_afterMET.png Distributions of the number of reconstructed b-tagged jets after applying the cut on MET.[pdf]

ttbar_effectiveMass.png Distribution of the effective mass of reconstructed ttbar system.[pdf]

topPt.png Distributions of pT of the reconstructed top quark in the positive branch of top pair events.[pdf]

topEta.png Distributions of eta of the reconstructed top quark in the positive branch of top pair events.[pdf]

transferMatrix.png The response matrix which is relating the cosTheta* at gen level to the cosTheta* at reconstructed level.[pdf]

cosThetaErrors.png Data-Simulation comparison for the cosTheta* distribution with systematic uncertainties.[pdf]

data_simulation_reweighted_To_Fit3.png The distribution of cosTheta* found in data events is compared to the same distribution in re-weighted simulated signal events. Also shown is the distribution of cosTheta* reconstructed in all background events[pdf]

Topic attachments
I Attachment History Action Size Date Who Comment
PDFpdf NBjets_afterMET.pdf r1 manage 16.5 K 2013-03-05 - 23:10 BatoolSafarzadehSamani  
PNGpng NBjets_afterMET.png r1 manage 14.7 K 2013-02-26 - 15:19 MaryamZeinali  
PDFpdf NBjets_beforeMET.pdf r1 manage 16.6 K 2013-03-05 - 23:10 BatoolSafarzadehSamani  
PNGpng NBjets_beforeMET.png r1 manage 14.9 K 2013-02-26 - 15:19 MaryamZeinali  
PNGpng cosThetaErrors.png r1 manage 19.1 K 2013-02-26 - 15:30 MaryamZeinali  
PDFpdf cosTheta_errors.pdf r1 manage 18.7 K 2013-03-05 - 23:28 BatoolSafarzadehSamani  
PNGpng cutFlowTable.png r1 manage 58.3 K 2013-02-26 - 15:05 MaryamZeinali  
PDFpdf data_simulation_reweighted_To_Fit3.pdf r1 manage 17.4 K 2013-03-05 - 23:15 BatoolSafarzadehSamani  
PNGpng data_simulation_reweighted_To_Fit3.png r1 manage 17.1 K 2013-02-26 - 15:30 MaryamZeinali  
PNGpng sysTable.png r1 manage 25.6 K 2013-02-26 - 15:05 MaryamZeinali  
PDFpdf topEta.pdf r1 manage 18.4 K 2013-03-05 - 23:10 BatoolSafarzadehSamani  
PNGpng topEta.png r1 manage 17.8 K 2013-02-26 - 15:19 MaryamZeinali  
PDFpdf topPt.pdf r1 manage 29.6 K 2013-03-05 - 23:10 BatoolSafarzadehSamani  
PNGpng topPt.png r1 manage 20.3 K 2013-02-26 - 15:19 MaryamZeinali  
PDFpdf transferMatrix.pdf r1 manage 14.4 K 2013-03-05 - 23:10 BatoolSafarzadehSamani  
PNGpng transferMatrix.png r1 manage 20.0 K 2013-02-26 - 15:19 MaryamZeinali  
PDFpdf ttbar_effectiveMass.pdf r1 manage 30.0 K 2013-03-05 - 23:23 BatoolSafarzadehSamani  
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Topic revision: r3 - 2013-03-05 - BatoolSafarzadehSamani
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