TOP-14-018 Measurement of the ttbar production cross section in the all-jets final state in pp collisions at √s = 8 TeV

Abstract

The cross section for ttbar production in the all-jets final state is measured in pp collisions at a centre-of-mass energy of 8 TeV at the LHC with the CMS detector, in data corresponding to an integrated luminosity of 18.4/fb. The inclusive cross section is found to be 275.6 ± 6.1 (stat) ± 37.8 (syst) ± 7.2 (lumi) pb. The normalized differential cross sections are measured as a function of the top quark transverse momenta, pT, and compared to predictions from quantum chromodynamics. The results are reported at detector, parton, and particle levels. In all cases, the measured top quark pT spectra are significantly softer than theoretical predictions.

Public Document

The paper is available on the arXiv:1509.06076.

Figures

Figure 1: Distribution of the reconstructed top quark mass after the kinematic fit. The normalizations of the ttbar signal and the QCD multijet background are taken from the template fit to the data. The bottom panel shows the fractional difference between the data and the sum of signal and background predictions, with the shaded band representing the MC statistical uncertainty.

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Figure 2a: Distribution of the kinematic fit probability. The normalization of the ttbar signal and the QCD multijet background are taken from the template fit to the data. The bottom panels show the fractional difference between the data and the sum of signal and background predictions, with the shaded band representing the MC statistical uncertainty.

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Figure 2b: Distribution of the distance between the reconstructed b partons at the eta-phi plane. The normalization of the ttbar signal and the QCD multijet background are taken from the template fit to the data. The bottom panels show the fractional difference between the data and the sum of signal and background predictions, with the shaded band representing the MC statistical uncertainty.

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Figure 3a: Distribution of the pT of the leading jet. The normalization of the ttbar signal and the QCD multijet background are taken from the template fit to the data. The bottom panels show the fractional difference between the data and the sum of signal and background predictions, with the shaded band representing the MC statistical uncertainty.

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Figure 3b: Distribution of the pT of the second leading jet. The normalization of the ttbar signal and the QCD multijet background are taken from the template fit to the data. The bottom panels show the fractional difference between the data and the sum of signal and background predictions, with the shaded band representing the MC statistical uncertainty.

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Figure 3c: Distribution of the pT of the third leading jet. The normalization of the ttbar signal and the QCD multijet background are taken from the template fit to the data. The bottom panels show the fractional difference between the data and the sum of signal and background predictions, with the shaded band representing the MC statistical uncertainty.

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Figure 3d: Distribution of the pT of the fourth leading jet. The normalization of the ttbar signal and the QCD multijet background are taken from the template fit to the data. The bottom panels show the fractional difference between the data and the sum of signal and background predictions, with the shaded band representing the MC statistical uncertainty.

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Figure 3e: Distribution of the pT of the fifth leading jet. The normalization of the ttbar signal and the QCD multijet background are taken from the template fit to the data. The bottom panels show the fractional difference between the data and the sum of signal and background predictions, with the shaded band representing the MC statistical uncertainty.

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Figure 3f: Distribution of the pT of the sixth leading jet. The normalization of the ttbar signal and the QCD multijet background are taken from the template fit to the data. The bottom panels show the fractional difference between the data and the sum of signal and background predictions, with the shaded band representing the MC statistical uncertainty.

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Figure 4a: Distribution of the leading reconstructed top quark pT . The normalizations of the ttbar signal and the QCD multijet background are taken from the template fit to the data. The bottom panels show the fractional difference between the data and the sum of signal and background predictions, with the shaded band representing the MC statistical uncertainty.

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Figure 4b: Distribution of the subleading reconstructed top quark pT. The normalizations of the ttbar signal and the QCD multijet background are taken from the template fit to the data. The bottom panels show the fractional difference between the data and the sum of signal and background predictions, with the shaded band representing the MC statistical uncertainty.

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Figure 5a: Distribution of the pT of the reconstructed top quark pair. The normalizations of the ttbar signal and the QCD multijet background are taken from the template fit to the data. The bottom panels show the fractional difference between the data and the sum of signal and background predictions, with the shaded band representing the MC statistical uncertainty.

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Figure 5b: Distribution of the rapidity of the reconstructed top quark pair. The normalizations of the ttbar signal and the QCD multijet background are taken from the template fit to the data. The bottom panels show the fractional difference between the data and the sum of signal and background predictions, with the shaded band representing the MC statistical uncertainty.

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Figure 6a: Distribution of the reconstructed top quark mass after the kinematic fit in the bin 0-150 GeV of the leading reconstructed top quark pT. The normalizations of the ttbar signal and the QCD multijet background are taken from the template fit to the data. The bottom panels show the fractional difference between the data and the sum of signal and background predictions, with the shaded band representing the MC statistical uncertainty.

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Figure 6b: Distribution of the reconstructed top quark mass after the kinematic fit in the bin 150-225 GeV of the leading reconstructed top quark pT. The normalizations of the ttbar signal and the QCD multijet background are taken from the template fit to the data. The bottom panels show the fractional difference between the data and the sum of signal and background predictions, with the shaded band representing the MC statistical uncertainty.

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Figure 6c: Distribution of the reconstructed top quark mass after the kinematic fit in the bin 225-300 GeV of the leading reconstructed top quark pT. The normalizations of the ttbar signal and the QCD multijet background are taken from the template fit to the data. The bottom panels show the fractional difference between the data and the sum of signal and background predictions, with the shaded band representing the MC statistical uncertainty.

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Figure 6d: Distribution of the reconstructed top quark mass after the kinematic fit in the bin 300-375 GeV of the leading reconstructed top quark pT. The normalizations of the ttbar signal and the QCD multijet background are taken from the template fit to the data. The bottom panels show the fractional difference between the data and the sum of signal and background predictions, with the shaded band representing the MC statistical uncertainty.

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Figure 6e: Distribution of the reconstructed top quark mass after the kinematic fit in the bin 375-500 GeV of the leading reconstructed top quark pT. The normalizations of the ttbar signal and the QCD multijet background are taken from the template fit to the data. The bottom panels show the fractional difference between the data and the sum of signal and background predictions, with the shaded band representing the MC statistical uncertainty.

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Figure 7a: Normalized fiducial differential cross section of the ttbar production as a function of the leading reconstructed top quark pT (detector level). The bottom panels show the fractional difference between various MC predictions and the data. Statistical uncertainties are shown with error bars, and systematic uncertainties with the shaded band.

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Figure 7b: Normalized fiducial differential cross section of the ttbar production as a function of the subleading reconstructed top quark pT (detector level). The bottom panels show the fractional difference between various MC predictions and the data. Statistical uncertainties are shown with error bars, and systematic uncertainties with the shaded band.

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Figure 8a: Normalized differential cross section of the ttbar production at parton level as a function of the leading top quark pT. The bottom panels show the fractional difference between various MC predictions and the data. Statistical uncertainties are shown with error bars, while theoretical (theo.) and experimental (exp.) systematic uncertainties with the shaded bands.

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Figure 8b: Normalized differential cross section of the ttbar production at parton level as a function of the subleading top quark pT. The bottom panels show the fractional difference between various MC predictions and the data. Statistical uncertainties are shown with error bars, while theoretical (theo.) and experimental (exp.) systematic uncertainties with the shaded bands.

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Figure 9a: Normalized differential cross section of the ttbar production at particle level as a function of the leading top quark pT. The bottom panels show the fractional difference between various MC predictions and the data. Statistical uncertainties are shown with error bars, while theoretical (theo.) and experimental (exp.) systematic uncertainties with the shaded bands.

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Figure 9b: Normalized differential cross section of the ttbar production at particle level as a function of the subleading top quark pT. The bottom panels show the fractional difference between various MC predictions and the data. Statistical uncertainties are shown with error bars, while theoretical (theo.) and experimental (exp.) systematic uncertainties with the shaded bands.

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Additional Material

Ratio of data over theory (Madgraph interfaced with Pythia 6) for the normalized differential cross section of the ttbar production at parton level as a function of the leading top pT in different decay channels. The error bars represent the total uncertainty. The measurements in the leptonic final states are taken from arXiv:1505.04480.

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Ratio of data over theory (Madgraph interfaced with Pythia 6) for the normalized differential cross section of the ttbar production at parton level as a function of the subleading top pT in different decay channels. The error bars represent the total uncertainty. The measurements in the leptonic final states are taken from arXiv:1505.04480.

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Tables

Fractional uncertainties in the inclusive ttbar production cross section.

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Normalized differential ttbar cross section as a function of the pT of the leading (pT(1)) and subleading (pT(2)) top quarks or antiquarks. The results are presented at detector level in the visible phase space.

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Normalized differential ttbar cross section as a function of the pT of the leading (pT(1)) and subleading (pT(2)) top quarks or antiquarks. The results are presented at parton level in the full phase space.

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Normalized differential ttbar cross section as a function of the pT of the leading (pT(1)) and subleading (pT(2)) top quarks or antiquarks. The results are presented at particle level.

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-- AndreasMeyer - 2015-09-10

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