Measurement of the ttbar production cross section in pp collisions at $\sqrt{s}$=8 TeV in the eτ and μτ dilepton final states


The top-quark pair production cross section is measured in final states with one electron or muon and one hadronically decaying τ-lepton from the process $t\bar{t}\rightarrow (\ell\nu_\ell) (\tau_\mathrm{h} \nu_\tau) {b\bar{b}}$, $\ell = {\rm e},\mu$. The data sample corresponds to an integrated luminosity of 19.6/fb collected with the CMS detector in proton-proton collisions at $\sqrt{s}$=8 TeV. The measured cross section $\sigma_{t\bar{t}} = 257\pm 3\,(\mathrm{stat.}) \pm 24\,(\mathrm{syst.}) \pm 7\,(\mathrm{lum.})~{\rm pb}$ assuming a top-quark mass of 172.5 GeV is consistent with the standard model prediction.


Figure Caption
The b-tagged jet multiplicity after the full event selection. The simulated contributions are normalized to the SM predicted values. The hatched area shows the total systematic uncertainty.

Figure (left) Figure (right) Caption
Distribution of the $\tau_h$ $p_T$ (left) and MET (right) after the full event selection, for the e$\tau$ and $\mu\tau$ channels combined. The simulated contributions are normalized to the SM predicted values. The shaded bands represent the total uncertainty. The last bins include the overflow.

Figure (left) Figure (right) Caption
Left: Minimum invariant mass reconstructed by pairing the $\tau_h$ with either a b-jet candidate or with the highest $p_T$ non b-tagged jet. Right: Distribution of the reconstructed top-quark mass m(top) for the $\tau_h$ dilepton candidate events after the full event selection. Data (points) are compared with the sum of signal and background yields, for the e$\tau_h$ and $\mu\tau_h$ channels combined. The simulated contributions are normalized to the SM predicted values. The hatched area shows the total uncertainty. The last bins include the overflow.

Table Caption
List of systematic uncertainties on the cross section measurement, and their combination. Lepton reconstruction uncertainties are uncorrelated, while all other uncertainties are assumed 100% correlated. The BLUE method is used to combine the cross section measurements in the e$\tau_h$ and $\mu\tau_h$ channels, with the corresponding weights of 0.47 and 0.53, respectively.

Table Caption
Number of expected events for signal assuming m(top)=172.5 GeV, and backgrounds. The background from misidentified $\tau_h$ is estimated from data, while the other backgrounds are estimated from simulation. Statistical and systematic uncertainties are shown.

Table Caption
Cross section results.

-- MicheleGallinaro - 26 Jun 2014

Topic attachments
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PDFpdf CCombDD_EndPoint.pdf r1 manage 51.3 K 2014-06-26 - 16:22 MicheleGallinaro  
PNGpng CCombDD_EndPoint.png r1 manage 157.1 K 2014-06-26 - 16:22 MicheleGallinaro  
PDFpdf CCombDD_btagmultiplicity_j.pdf r1 manage 37.5 K 2014-06-26 - 16:22 MicheleGallinaro  
PNGpng CCombDD_btagmultiplicity_j.png r1 manage 105.7 K 2014-06-26 - 16:22 MicheleGallinaro  
PDFpdf CCombDD_met.pdf r1 manage 46.3 K 2014-06-26 - 16:22 MicheleGallinaro  
PNGpng CCombDD_met.png r1 manage 145.4 K 2014-06-26 - 16:22 MicheleGallinaro  
PDFpdf CCombDD_mtop.pdf r1 manage 50.9 K 2014-06-26 - 16:22 MicheleGallinaro  
PNGpng CCombDD_mtop.png r1 manage 152.0 K 2014-06-26 - 16:22 MicheleGallinaro  
PDFpdf CCombDD_pt_t.pdf r1 manage 46.6 K 2014-06-26 - 16:22 MicheleGallinaro  
PNGpng CCombDD_pt_t.png r1 manage 141.9 K 2014-06-26 - 16:24 MicheleGallinaro  
PDFpdf ttab1.pdf r3 r2 r1 manage 84.3 K 2014-06-26 - 11:53 MicheleGallinaro  
PNGpng ttab1.png r2 r1 manage 131.2 K 2014-06-26 - 11:53 MicheleGallinaro  
PDFpdf ttab2.pdf r1 manage 62.2 K 2014-06-26 - 11:49 MicheleGallinaro  
PNGpng ttab2.png r1 manage 76.1 K 2014-06-26 - 11:50 MicheleGallinaro  
PDFpdf ttab3.pdf r1 manage 50.4 K 2014-06-26 - 12:00 MicheleGallinaro  
PNGpng ttab3.png r1 manage 37.7 K 2014-06-26 - 12:01 MicheleGallinaro  
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Topic revision: r4 - 2014-06-28 - AndreasMeyer
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