TOP-12-004
Measurement of Spin Correlations in top-antitop pair events in the dilepton channels in pp collisions at sqrt(s)=7 TeV

Abstract

We present a measurement of the top spin correlation in top-antitop pair production in the dilepton channels in pp collisions at . The data sample used for the measurement corresponds to an integrated luminosity of collected with the CMS detector at the LHC. The measurement is performed in events with two leptons (electrons or muons) in the final state, and at least two jets where at least one is identified as a b-jet. In addition the presence of missing transverse energy is required. The spin correlation in top-antitop pair events is extracted from a fit to the angular distribution between the two selected leptons. In the helicity basis, the correlation coefficient is found to be 0.240.020.08. The spin correlation is also investigated through other variables, for different top-antitop pair invariant masses. All measurements are found to be in agreement with the Standard Model predictions.

Public Document

Figures

Δ Φ Analysis

Figure Caption
spincorcomp distributions for top-antitop pair signal events with spin correlation compatible with the SM, and without correlation (uncorrelated). The and channels are summed after the event selection. [Get pdf version]
spincorcomp Result of the fit (solid line) performed on data (triangles) after the combination of the three channels. The data are also compared to the distribution oftop-antitop pair events with and without spin correlation. The background components are included in the plot. [Get pdf version]

Asymmetry Analysis

spincorcomp Reconstruction level asymmetry distributions for A_{ΔΦ } inclusively. The tt_ll component is taken from the POWHEG-PYTHIA top-antitop pair sample. The yields are normalized to match the data in the inclusive measurement. [Get pdf version]
spincorcomp Reconstruction level asymmetry distributions for in the region where . The component is taken from the POWHEG-PYTHIA top-antitop pair sample. The yields are normalized to match the data in the inclusive measurement. [Get pdf version]
spincorcomp Reconstruction level asymmetry distributions for A_{c1c2}, inclusively. The tt_ll component is taken from the \POWHEG-\PYTHIA sample. The yields are normalized to match the data in the inclusive measurement. [Get pdf version]
spincorcomp Reconstruction level asymmetry distributions for A_{c1c2}, in the region where . The component is taken from the POWHEG-PYTHIA top-antitop pair sample. The yields are normalized to match the data in the inclusive measurement.[Get pdf version]
spincorcomp Background-subtracted and unfolded asymmetry distributions in the inclusive region. [Get pdf version]
spincorcomp Background-subtracted and unfolded asymmetry distributions in the inclusive region. [Get pdf version]

Tables

Tables Caption
table1 Uncertainty on the fraction of events with spin correlation , as predicted by the fit.
table2 Reconstructed and simulated asymmetries, inclusively and in the region where . Uncertainties are statistical only.
table3 Uncertainty on the unfolded values of and .
-- FelixHoehle - 29-Jun-2012
Topic attachments
I Attachment History Action Size Date Who Comment
PDFpdf finalplot_lep_azimuthal_asymmetry2.pdf r1 manage 15.4 K 2012-06-29 - 16:03 FelixHoehle Asymmetry analysis
PNGpng finalplot_lep_azimuthal_asymmetry2.png r1 manage 177.6 K 2012-06-29 - 16:03 FelixHoehle Asymmetry analysis
PDFpdf finalplot_lep_azimuthal_asymmetry2Signal.pdf r1 manage 15.6 K 2012-06-29 - 16:03 FelixHoehle Asymmetry analysis
PNGpng finalplot_lep_azimuthal_asymmetry2Signal.png r1 manage 169.7 K 2012-06-29 - 16:03 FelixHoehle Asymmetry analysis
PDFpdf finalplot_top_spin_correlation.pdf r1 manage 15.7 K 2012-06-29 - 16:03 FelixHoehle Asymmetry analysis
PNGpng finalplot_top_spin_correlation.png r1 manage 188.3 K 2012-06-29 - 16:03 FelixHoehle Asymmetry analysis
PDFpdf finalplot_top_spin_correlationSignal.pdf r1 manage 15.9 K 2012-06-29 - 16:03 FelixHoehle Asymmetry analysis
PNGpng finalplot_top_spin_correlationSignal.png r1 manage 189.8 K 2012-06-29 - 16:03 FelixHoehle Asymmetry analysis
PDFpdf finalplot_unfolded_lep_azimuthal_asymmetry_v3.pdf r1 manage 16.3 K 2012-07-03 - 09:27 FelixHoehle DeltaPhi Analysis plots
PNGpng finalplot_unfolded_lep_azimuthal_asymmetry_v3.png r1 manage 97.5 K 2012-07-03 - 09:27 FelixHoehle DeltaPhi Analysis plots
PDFpdf finalplot_unfolded_top_spin_correlation.pdf r1 manage 16.1 K 2012-06-29 - 16:06 FelixHoehle Asymmetry analysis
PNGpng finalplot_unfolded_top_spin_correlation.png r1 manage 131.9 K 2012-06-29 - 16:06 FelixHoehle Asymmetry analysis
PDFpdf goodplot.pdf r1 manage 14.3 K 2012-06-29 - 16:02 FelixHoehle DeltaPhi Analysis plots
PNGpng goodplot.png r1 manage 112.7 K 2012-06-29 - 16:02 FelixHoehle DeltaPhi Analysis plots
PDFpdf spincorcomp_v2.pdf r1 manage 14.1 K 2012-06-30 - 10:40 FelixHoehle DeltaPhi Analysis plots
PNGpng spincorcomp_v2.png r1 manage 68.6 K 2012-06-30 - 10:38 FelixHoehle DeltaPhi Analysis plots
PNGpng table1.png r1 manage 130.5 K 2012-06-30 - 13:40 FelixHoehle PAS tables
PNGpng table2.png r1 manage 66.6 K 2012-06-30 - 13:40 FelixHoehle PAS tables
PNGpng table3.png r1 manage 119.8 K 2012-06-30 - 13:40 FelixHoehle PAS tables
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Topic revision: r11 - 2012-07-03 - FelixHoehle
 
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