Measurement of Top Polarization in Top-antitop Pair Events in the Dilepton Channels in pp Collisions at sqrt(s)=7 TeV


A measurement of the top quark polarization in $t\bar{t} \rightarrow \ell^+ \ell^-$ events is performed in a data sample corresponding to a total integrated luminosity of $5 fb^{-1}$ collected by the CMS experiment in pp collisions at a centre-of-mass energy of 7 TeV at the LHC. The measured value in the helicity basis is $P_{n} = -0.009 \pm 0.029 \pm 0.041$, in agreement with the standard model expectation.


Tables Caption
Table1 Table1: The observed and simulated yields after the event selection described in the text. Uncertainties are statistical only. Where the simulated yields are zero, upper limits are given based on the weighted yield, had one of the simulated events passed the selection.

Table2 Table2: Binning used in the distributions of $\cos(\theta_l^+)$.

Table3 Table3: Systematic uncertainties.


Figure Caption

preselection_nbtag.pdf preselection_nVtx.pdf Comparison of data and simulation for number of b tagged jets and number of vertices.

finalplot_lep_costheta_cms.pdf finalplot_lepMinus_costheta_cms.pdf The reconstruction level $\cos(\theta_l^+)$ and  $\cos(\theta_l^-)$ distributions, for data and the simulation.
The simulated events are divided into $t\bar{t} \rightarrow \ell^+ \ell^-$ and background,
where the background consists of the categories other than $t\bar{t} \rightarrow \ell^+ \ell^-$ in Table 1.

accept_lepPlusCosTheta.pdf Response_lep_costheta_cms.pdf Acceptance matrix bins (left) and smearing effects due to
the uncertainties of top reconstruction (right).

finalplot_unfolded_lep_costheta_cms_withsyst.pdf Background-subtracted and unfolded $\cos(\theta_l^+)$ distribution. The error bars represent statistical uncertainties only, while the systematic uncertainty band is represented by the hatched area. Note that the bin values are correlated due to the unfolding.

-- YanjunTu - 01-Jul-2012

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PDFpdf Response_lep_costheta_cms.pdf r1 manage 14.4 K 2012-07-01 - 03:40 YanjunTu  
PNGpng Response_lep_costheta_cms.png r1 manage 58.7 K 2012-07-01 - 03:40 YanjunTu  
PDFpdf Table1.pdf r1 manage 59.0 K 2012-07-01 - 04:13 YanjunTu  
PNGpng Table1.png r1 manage 64.9 K 2012-07-01 - 04:13 YanjunTu  
PDFpdf Table2.pdf r1 manage 13.7 K 2012-07-01 - 04:13 YanjunTu  
PNGpng Table2.png r1 manage 13.1 K 2012-07-01 - 04:13 YanjunTu  
PDFpdf Table3.pdf r1 manage 25.5 K 2012-07-01 - 04:13 YanjunTu  
PNGpng Table3.png r1 manage 25.7 K 2012-07-01 - 04:13 YanjunTu  
PDFpdf accept_lepPlusCosTheta.pdf r1 manage 14.1 K 2012-07-01 - 03:40 YanjunTu  
PNGpng accept_lepPlusCosTheta.png r1 manage 66.9 K 2012-07-01 - 03:40 YanjunTu  
PDFpdf finalplot_lepMinus_costheta_cms.pdf r1 manage 15.6 K 2012-07-01 - 03:40 YanjunTu  
PNGpng finalplot_lepMinus_costheta_cms.png r1 manage 212.4 K 2012-07-01 - 03:40 YanjunTu  
PDFpdf finalplot_lep_costheta_cms.pdf r1 manage 15.6 K 2012-07-01 - 03:40 YanjunTu  
PNGpng finalplot_lep_costheta_cms.png r1 manage 212.0 K 2012-07-01 - 03:40 YanjunTu  
PDFpdf finalplot_unfolded_lep_costheta_cms_withsyst.pdf r1 manage 15.7 K 2012-07-01 - 03:40 YanjunTu  
PNGpng finalplot_unfolded_lep_costheta_cms_withsyst.png r1 manage 105.3 K 2012-07-01 - 03:40 YanjunTu  
PDFpdf preselection_nVtx.pdf r1 manage 16.5 K 2012-07-01 - 03:16 YanjunTu  
PNGpng preselection_nVtx.png r1 manage 93.2 K 2012-07-01 - 03:12 YanjunTu  
PDFpdf preselection_nbtag.pdf r1 manage 15.0 K 2012-07-01 - 03:25 YanjunTu  
PNGpng preselection_nbtag.png r1 manage 86.0 K 2012-07-01 - 03:25 YanjunTu  
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Topic revision: r2 - 2012-07-02 - RobertoTenchini
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