TOP-14-010 Public Summary

Abstract

This paper describes a measurement of the top quark mass with the full 2012 dataset captured by CMS at a center-of-mass energy of √s = 8 TeV, corresponding to an integrated luminosity of $19.7 \pm 0.5 $ /fb. The analysis is performed with dilepton ttbar decays, in which both W bosons decay to lν;, and uses the Analytical Matrix Weighting Technique (AMWT). This measurement was performed blind, and constitutes the first such blind top mass measurement performed by CMS. It is based on events with electron and muon final states, i.e. ee, eμ, μμ. The mass of the top quark is measured to be $m_t = 172.47(stat.) \pm1.40 (syst.)$ GeV.

Public Document

This analysis and its results are described in CMS PAS TOP-14-010, available publicly on the CERN Document Server.

Results

Figure Caption
result2.png The measured mass
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ll_1B2B_all.png -log(likelihood) for data. The continuous line is the parabolic fit to the points. The arrow indicates the uncalibrated measured mass of 172.418 GeV.
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Lep1Pt_2L_2J1BmetZ.pngJet1Pt_2L_2J1BmetZ.png Leading lepton pT (left), leading jet pT (right) for data and MC, summed over all channels. The vertical bars show the statistical uncertainty and the hatched bands show the statistical and systematic uncertainties added in quadrature.
Left figure: PNG PDF, right figure: PNG PDF
LepInvM_2L_2J1BmetZ.pngLep2Pt_2L_2J1BmetZ.png Dilepton invariant mass (left), second leading lepton pT (right) for data and MC, summed over all channels. The vertical bars show the statistical uncertainty and the hatched bands show the statistical and systematic uncertainties added in quadrature.
Left figure: PNG PDF, right figure: PNG PDF
Jet2Pt_2L_2J1BmetZ.pngMET_2L_2J1BmetZ.png Second leading jet pT (left) and missing transverse energy distributions (right) for data and MC, summed over all channels. The vertical bars show the statistical uncertainty and the hatched bands show the statistical and systematic uncertainties added in quadrature.
Left figure: PNG PDF, right figure: PNG PDF
amwt_2L_2J1BmetZ.png Distribution of the peak mass observed in data and in the simulation generated assuming a top mass of 172.5 GeV. The vertical bars show the statistical uncertainty and the hatched bands show the statistical and systematic uncertainties added in quadrature. The range of the histogram has been updated w.r.t. corresponding figure in the PAS document.
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meanMass_172_.png pullMass_172_.png cal_bias_.png Distributions of the mean measured mass values (left) and pulls (center) for pseudo-experiments drawn from an MC with mt = 172.5 GeV. The mean measured mass versus MC input mass with the straight line calibration fit superimposed (right).
Left: PNG PDF, Middle: PNG PDF, Right: PNG PDF
DYSF.png DY scale factors by number of b-tags and lepton flavor.
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Yield1b.png Expected number of events, scaled to the integrated luminosity of the data sample with 1 b-tag after all cuts. For DY production the uncertainty in the normalization to the data is quoted. For all others, the scale and pdf uncertainties in the cross sections, and the statistical uncertainty of the simulation, added in quadrature, are quoted. The data line gives the number of events observed and the last column gives the sum of all three channels.
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Yield2b.png Expected number of events, scaled to the integrated luminosity of the data sample with ≥2 b-tags after all cuts. For DY production the uncertainty in the normalization to the data is quoted. For all others, the scale and pdf uncertainties in the cross sections, and the statistical uncertainty of the simulation, added in quadrature, are quoted. The data line gives the number of events observed and the last column gives the sum of all three channels.
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expected.png Expected number of background events, number of simulated signal events for 172.5 GeV, and number of events observed in data that have 100 < mpeak < 400 GeV and are used in the final fit. For DY production the uncertainty in the normalization to the data is quoted. For all others, the scale and pdf uncertainties in the cross sections, and the statistical uncertainty of the simulation, added in quadrature, are quoted.
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syst.png List of systematic uncertainties for the combined fit to the entire dilepton data set.
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-- Main.Rechard Nally and Meenakshi Narain - 21 Oct 2014

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Topic revision: r10 - 2014-10-23 - AndreasMeyer
 
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