Measurement of the mass difference between top and antitop quarks

Abstract

A measurement of the mass difference between the top quark and the antitop quark (Delta m_t = m_t - m_tbar) is performed using events with a muon and multi-jets in the final state produced at the LHC in pp collisions at √s=7 TeV. The data is collected in 2011 with the CMS detector and corresponds to an integrated luminosity of 1.09 fb-1. The value of Delta m_t = -1.2 1.2 (stat) 0.5 (syst) GeV is obtained.

Main Document

Detailed record in CDS, and the Fulltext in PDF. (to come soon ...)

Some further explanation about the analysis

In this analysis, ttbar events decaying in the muon+jets channel are used. These are events where one of the two top quarks decays hadronically (t -> bW ->bqqbar) and the other top quark decays in the muon channel (t -> bW -> b mu nu_{mu}). The muon charge allows us to split the data sample in two pieces, where top or antitop quarks decay hadronically. For each event category, the Ideogram method is used to measure the mass of the top quarks and finally both measured masses are subtracted from each other. The Ideogram method was already used before by the CMS experiment (and other experiments) to measure the top quark mass (link). The method is modified in this analysis as it incorporates a different kinematic fit and it uses only the hadronic portion of the ttbar decay in the kinematic fit.

Approved Results from TOP-11-019 ( click on plot to get .png )

Result Abbreviated Caption
finalResult.png Main top mass difference result.

Approved Data/MC comparison plots from TOP-11-019 ( click on plot to get .pdf )

Figure mu^{+}+jets Figure mu^{-}+jets Abbreviated Caption
Transverse Momentum of all the selected jets for an integrated luminosity of 1.09/fb after applying the event selection.
Number of selected jets for an integrated luminosity of 1.09/fb after applying the event selection.
Top quark mass before the kinematic fit for an integrated luminosity of 1.09/fb after applying the event selection. This is the invariant mass of the three hadronic jets (before kinematic fit) of the jet combination with the lowest chisquare of the kinematic fit.
Fitted top quark mass of the jet combination with the lowest chisquare for an integrated luminosity of 1.09/fb after applying the event selection.
Uncertainty on the fitted top quark mass of the jet combination with the lowest chisquare for an integrated luminosity of 1.09/fb after applying the event selection.
Minimum chisquare of the kinematic fit of the jet combination with the lowest chisquare for an integrated luminosity of 1.09/fb after applying the event selection.
Number of b-tagged jets for an integrated luminosity of 1.09/fb after applying the event selection.

Other Approved plots from TOP-11-019

Figure Abbreviated Caption
Example plot of the chisquare of the kinematic fit as a function of the top quark mass constraint
Distribution of the fitted top quark mass for good jet combinations, according to MC
Width of the pull distribution as a function of the generated top quark mass, for inclusive mu+jets events
Bias on the estimated top quark mass as a function of the generated top quark mass, for inclusive mu+jets events
Bias on the estimated top quark mass as a function of the generated top quark mass after calibration for mu^{+}+jets events
Bias on the estimated top quark mass as a function of the generated top quark mass after calibration for mu^{-}+jets events
Pull distribution after calibration for mu^{+}+jets events
Pull distribution after calibration for mu^{-}+jets events
Width of the pull distribution as a function of the generated top quark mass after calibration for mu^{+}+jets events
Width of the pull distribution as a function of the generated top quark mass after calibration for mu^{-}+jets events

Tables from TOP-11-019 ( click on plot to get .png )

Result Abbreviated Caption
dataMcTable.png Event yields in data and MC simulation for the various contributing processes after all selection steps for an integrated luminosity of 1.09/fb.
systematics.png Overview of the systematic uncertainties considered.

-- StijnBlyweert - 18-Aug-2011

Topic attachments
I Attachment History Action Size Date Who Comment
PDFpdf AllJets_pt_muMinus_StackAreaNorm.pdf r2 r1 manage 20.1 K 2011-08-18 - 22:36 StijnBlyweert  
PNGpng AllJets_pt_muMinus_StackAreaNorm.png r2 r1 manage 1231.5 K 2011-08-18 - 22:55 StijnBlyweert  
PDFpdf AllJets_pt_muPlus_StackAreaNorm.pdf r2 r1 manage 20.2 K 2011-08-18 - 22:35 StijnBlyweert  
PNGpng AllJets_pt_muPlus_StackAreaNorm.png r2 r1 manage 1231.5 K 2011-08-18 - 22:55 StijnBlyweert  
JPEGjpg Chi2_Combi.jpg r1 manage 104.8 K 2011-08-18 - 19:57 StijnBlyweert  
PDFpdf MinChi2ndf_Fit_muMinus_StackAreaNormLogY.pdf r3 r2 r1 manage 23.4 K 2011-08-19 - 13:51 StijnBlyweert  
PNGpng MinChi2ndf_Fit_muMinus_StackAreaNormLogY.png r3 r2 r1 manage 1231.5 K 2011-08-19 - 13:51 StijnBlyweert  
PDFpdf MinChi2ndf_Fit_muPlus_StackAreaNormLogY.pdf r3 r2 r1 manage 23.5 K 2011-08-19 - 13:51 StijnBlyweert  
PNGpng MinChi2ndf_Fit_muPlus_StackAreaNormLogY.png r3 r2 r1 manage 1231.5 K 2011-08-19 - 13:51 StijnBlyweert  
PDFpdf Nr_of_jets_muMinus_StackAreaNorm.pdf r2 r1 manage 15.1 K 2011-08-18 - 22:37 StijnBlyweert  
PNGpng Nr_of_jets_muMinus_StackAreaNorm.png r2 r1 manage 1231.5 K 2011-08-18 - 22:51 StijnBlyweert  
PDFpdf Nr_of_jets_muPlus_StackAreaNorm.pdf r2 r1 manage 15.1 K 2011-08-18 - 22:37 StijnBlyweert  
PNGpng Nr_of_jets_muPlus_StackAreaNorm.png r2 r1 manage 1231.5 K 2011-08-18 - 22:50 StijnBlyweert  
JPEGjpg bias_all.jpg r1 manage 88.0 K 2011-08-18 - 19:56 StijnBlyweert  
JPEGjpg bias_minus_calibrated.jpg r1 manage 89.1 K 2011-08-18 - 19:57 StijnBlyweert  
JPEGjpg bias_plus_calibrated.jpg r1 manage 89.6 K 2011-08-18 - 19:57 StijnBlyweert  
PNGpng dataMcTable.png r1 manage 708.4 K 2011-08-18 - 17:27 StijnBlyweert  
PNGpng finalResult.png r1 manage 225.0 K 2011-08-18 - 16:25 StijnBlyweert  
JPEGjpg logpullplot_minus.jpg r2 r1 manage 66.6 K 2011-08-18 - 23:01 StijnBlyweert  
JPEGjpg logpullplot_plus.jpg r2 r1 manage 66.0 K 2011-08-18 - 23:01 StijnBlyweert  
JPEGjpg mTopFitGoodCombi.jpg r1 manage 114.4 K 2011-08-18 - 19:57 StijnBlyweert  
PDFpdf mTop_Fit_muMinus_StackAreaNorm.pdf r2 r1 manage 24.0 K 2011-08-18 - 22:35 StijnBlyweert  
PNGpng mTop_Fit_muMinus_StackAreaNorm.png r2 r1 manage 1231.5 K 2011-08-18 - 22:54 StijnBlyweert  
PDFpdf mTop_Fit_muPlus_StackAreaNorm.pdf r2 r1 manage 24.3 K 2011-08-18 - 22:37 StijnBlyweert  
PNGpng mTop_Fit_muPlus_StackAreaNorm.png r2 r1 manage 1231.5 K 2011-08-18 - 22:53 StijnBlyweert  
PDFpdf mTop_UnFitted_muMinus_StackAreaNorm.pdf r2 r1 manage 24.3 K 2011-08-18 - 22:37 StijnBlyweert  
PNGpng mTop_UnFitted_muMinus_StackAreaNorm.png r2 r1 manage 1231.5 K 2011-08-18 - 22:53 StijnBlyweert  
PDFpdf mTop_UnFitted_muPlus_StackAreaNorm.pdf r2 r1 manage 24.5 K 2011-08-18 - 22:37 StijnBlyweert  
PNGpng mTop_UnFitted_muPlus_StackAreaNorm.png r2 r1 manage 1231.5 K 2011-08-18 - 22:53 StijnBlyweert  
PDFpdf nBtags_muMinus_StackAreaNorm.pdf r2 r1 manage 15.1 K 2011-08-18 - 22:36 StijnBlyweert  
PNGpng nBtags_muMinus_StackAreaNorm.png r2 r1 manage 1231.5 K 2011-08-18 - 22:52 StijnBlyweert  
PDFpdf nBtags_muPlus_StackAreaNorm.pdf r2 r1 manage 15.1 K 2011-08-18 - 22:49 StijnBlyweert  
PNGpng nBtags_muPlus_StackAreaNorm.png r2 r1 manage 1231.5 K 2011-08-18 - 22:51 StijnBlyweert  
JPEGjpg pull_all.jpg r1 manage 96.8 K 2011-08-18 - 19:56 StijnBlyweert  
JPEGjpg pull_minus_calibrated.jpg r1 manage 99.9 K 2011-08-18 - 19:58 StijnBlyweert  
JPEGjpg pull_plus_calibrated.jpg r1 manage 97.9 K 2011-08-18 - 19:57 StijnBlyweert  
PDFpdf sigmaMtop_Fit_muMinus_StackAreaNorm.pdf r2 r1 manage 25.0 K 2011-08-18 - 22:37 StijnBlyweert  
PNGpng sigmaMtop_Fit_muMinus_StackAreaNorm.png r2 r1 manage 1231.5 K 2011-08-18 - 22:50 StijnBlyweert  
PDFpdf sigmaMtop_Fit_muPlus_StackAreaNorm.pdf r2 r1 manage 25.3 K 2011-08-18 - 22:56 StijnBlyweert  
PNGpng sigmaMtop_Fit_muPlus_StackAreaNorm.png r2 r1 manage 1231.5 K 2011-08-18 - 22:49 StijnBlyweert  
PNGpng systematics.png r1 manage 2360.8 K 2011-08-18 - 17:30 StijnBlyweert  
Edit | Attach | Watch | Print version | History: r6 < r5 < r4 < r3 < r2 | Backlinks | Raw View | WYSIWYG | More topic actions
Topic revision: r6 - 2011-08-19 - FrankPeterSchilling
 
    • Cern Search Icon Cern Search
    • TWiki Search Icon TWiki Search
    • Google Search Icon Google Search

    CMSPublic All webs login

This site is powered by the TWiki collaboration platform Powered by PerlCopyright & 2008-2020 by the contributing authors. All material on this collaboration platform is the property of the contributing authors.
Ideas, requests, problems regarding TWiki? Send feedback