CMS-TOP-17-001 ; CERN-EP-2018-317 | ||
Measurement of the $ \mathrm{t\bar{t}} $ production cross section, the top quark mass, and the strong coupling constant using dilepton events in pp collisions at $\sqrt{s} = $ 13 TeV | ||
CMS Collaboration | ||
27 December 2018 | ||
Eur. Phys. J. C 79 (2019) 368 | ||
Abstract: A measurement of the top quark-antiquark pair production cross section $ {\sigma_\mathrm{t\bar{t}}} $ in proton-proton collisions at a centre-of-mass energy of 13 TeV is presented. The data correspond to an integrated luminosity of 35.9 fb$^{-1}$, recorded by the CMS experiment at the CERN LHC in 2016. Dilepton events ($\mathrm{e}^{\pm}\mu^{\mp}$ , $\mu^{+}\mu^{-}$, $\mathrm{e^{+}e^{-}}$) are selected and the cross section is measured from a likelihood fit. For a top quark mass parameter in the simulation of $ {{m_{\mathrm{t}}} ^{\mathrm{MC}}} = $ 172.5 GeV the fit yields a measured cross section ${\sigma_\mathrm{t\bar{t}}} = $ 803 $\pm$ 2 (stat) $\pm$ 25 (syst) $\pm$ 20 (lumi) pb, in agreement with the expectation from the standard model calculation at next-to-next-to-leading order. A simultaneous fit of the cross section and the top quark mass parameter in the simulation is performed. The measured value of ${{m_{\mathrm{t}}} ^{\mathrm{MC}}} = $ 172.33 $\pm$ 0.14 (stat) $^{+0.66}_{-0.72}$ (syst) GeV is in good agreement with previous measurements. The resulting cross section is used, together with the theoretical prediction, to determine the top quark mass and to extract a value of the strong coupling constant with different sets of parton distribution functions. | ||
Links: e-print arXiv:1812.10505 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; CADI line (restricted) ; |
Figures | |
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Figure 1:
Distributions of the transverse momentum (left) and pseudorapidity (right) of the leading (upper) and subleading (middle) leptons in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel after the event selection for the data (points) and the predictions for the signal and various backgrounds from the simulation (shaded histograms). The lower row shows the jet (left) and b-tagged jet (right) multiplicity distributions. The vertical bars on the points represent the statistical uncertainties in the data. The hatched bands correspond to the systematic uncertainty in the $ {{\mathrm {t}\overline {\mathrm {t}}}} $ signal MC simulation. The uncertainties in the integrated luminosity and background contributions are not included. The ratios of the data to the sum of the predicted yields are shown in the lower panel of each figure. Here, the solid gray band represents the contribution of the statistical uncertainty in the MC simulation. |
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Figure 1-a:
Distribution of the transverse momentum of the leading lepton in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel after the event selection for the data (points) and the predictions for the signal and various backgrounds from the simulation (shaded histograms). The vertical bars on the points represent the statistical uncertainties in the data. The hatched bands correspond to the systematic uncertainty in the $ {{\mathrm {t}\overline {\mathrm {t}}}} $ signal MC simulation. The uncertainties in the integrated luminosity and background contributions are not included. The ratios of the data to the sum of the predicted yields are shown in the lower panel of each figure. Here, the solid gray band represents the contribution of the statistical uncertainty in the MC simulation. |
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Figure 1-b:
Distribution of the pseudorapidity of the leading lepton in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel after the event selection for the data (points) and the predictions for the signal and various backgrounds from the simulation (shaded histograms). The vertical bars on the points represent the statistical uncertainties in the data. The hatched bands correspond to the systematic uncertainty in the $ {{\mathrm {t}\overline {\mathrm {t}}}} $ signal MC simulation. The uncertainties in the integrated luminosity and background contributions are not included. The ratios of the data to the sum of the predicted yields are shown in the lower panel of each figure. Here, the solid gray band represents the contribution of the statistical uncertainty in the MC simulation. |
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Figure 1-c:
Distribution of the transverse momentum of the subleading lepton in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel after the event selection for the data (points) and the predictions for the signal and various backgrounds from the simulation (shaded histograms). The vertical bars on the points represent the statistical uncertainties in the data. The hatched bands correspond to the systematic uncertainty in the $ {{\mathrm {t}\overline {\mathrm {t}}}} $ signal MC simulation. The uncertainties in the integrated luminosity and background contributions are not included. The ratios of the data to the sum of the predicted yields are shown in the lower panel of each figure. Here, the solid gray band represents the contribution of the statistical uncertainty in the MC simulation. |
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Figure 1-d:
Distribution of the pseudorapidity of the subleading lepton in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel after the event selection for the data (points) and the predictions for the signal and various backgrounds from the simulation (shaded histograms). The vertical bars on the points represent the statistical uncertainties in the data. The hatched bands correspond to the systematic uncertainty in the $ {{\mathrm {t}\overline {\mathrm {t}}}} $ signal MC simulation. The uncertainties in the integrated luminosity and background contributions are not included. The ratios of the data to the sum of the predicted yields are shown in the lower panel of each figure. Here, the solid gray band represents the contribution of the statistical uncertainty in the MC simulation. |
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Figure 1-e:
Distribution of the jet multiplicity. The vertical bars on the points represent the statistical uncertainties in the data. The hatched bands correspond to the systematic uncertainty in the $ {{\mathrm {t}\overline {\mathrm {t}}}} $ signal MC simulation. The uncertainties in the integrated luminosity and background contributions are not included. The ratios of the data to the sum of the predicted yields are shown in the lower panel of each figure. Here, the solid gray band represents the contribution of the statistical uncertainty in the MC simulation. |
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Figure 1-f:
Distribution of the b-tagged jet multiplicity. The vertical bars on the points represent the statistical uncertainties in the data. The hatched bands correspond to the systematic uncertainty in the $ {{\mathrm {t}\overline {\mathrm {t}}}} $ signal MC simulation. The uncertainties in the integrated luminosity and background contributions are not included. The ratios of the data to the sum of the predicted yields are shown in the lower panel of each figure. Here, the solid gray band represents the contribution of the statistical uncertainty in the MC simulation. |
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Figure 2:
The same distributions as in Fig. 1, but for the ${{{\mu ^{+}}} {{\mu ^{-}}}}$ channel. |
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Figure 2-a:
The same distributions as in Fig. 1, but for the ${{{\mu ^{+}}} {{\mu ^{-}}}}$ channel. |
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Figure 2-b:
The same distributions as in Fig. 1, but for the ${{{\mu ^{+}}} {{\mu ^{-}}}}$ channel. |
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Figure 2-c:
The same distributions as in Fig. 1, but for the ${{{\mu ^{+}}} {{\mu ^{-}}}}$ channel. |
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Figure 2-d:
The same distributions as in Fig. 1, but for the ${{{\mu ^{+}}} {{\mu ^{-}}}}$ channel. |
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Figure 2-e:
The same distributions as in Fig. 1, but for the ${{{\mu ^{+}}} {{\mu ^{-}}}}$ channel. |
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Figure 2-f:
The same distributions as in Fig. 1, but for the ${{{\mu ^{+}}} {{\mu ^{-}}}}$ channel. |
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Figure 3:
The same distributions as in Fig. 1, but for the ${{\mathrm {e}^{+}} {\mathrm {e}^{-}}}$ channel. |
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Figure 3-a:
The same distributions as in Fig. 1, but for the ${{\mathrm {e}^{+}} {\mathrm {e}^{-}}}$ channel. |
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Figure 3-b:
The same distributions as in Fig. 1, but for the ${{\mathrm {e}^{+}} {\mathrm {e}^{-}}}$ channel. |
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Figure 3-c:
The same distributions as in Fig. 1, but for the ${{\mathrm {e}^{+}} {\mathrm {e}^{-}}}$ channel. |
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Figure 3-d:
The same distributions as in Fig. 1, but for the ${{\mathrm {e}^{+}} {\mathrm {e}^{-}}}$ channel. |
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Figure 3-e:
The same distributions as in Fig. 1, but for the ${{\mathrm {e}^{+}} {\mathrm {e}^{-}}}$ channel. |
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Figure 3-f:
The same distributions as in Fig. 1, but for the ${{\mathrm {e}^{+}} {\mathrm {e}^{-}}}$ channel. |
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Figure 4:
Distributions in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel after the fit to the data. In the left column events with zero or three or more b-tagged jets are shown. The middle (right) column shows events with exactly one (two) b-tagged jets. Events with zero, one, two, or three or more additional non-b-tagged jets are shown in the first, second, third, and fourth row, respectively. The hatched bands correspond to the total uncertainty in the sum of the predicted yields including all correlations. The ratios of the data to the sum of the simulated yields after the fit are shown in the lower panel of each figure. Here, the solid gray band represents the contribution of the statistical uncertainty in the MC simulation. |
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Figure 4-a:
Event yield in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel after the fit to the data for events with zero or three or more b-tagged jets, and zero additional non-b-tagged jet. The hatched band corresponds to the total uncertainty in the sum of the predicted yields including all correlations. The ratios of the data to the sum of the simulated yields after the fit are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty in the MC simulation. |
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Figure 4-b:
Event yield in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel after the fit to the data for events with exactly one b-tagged jets, and zero additional non-b-tagged jet. The hatched band corresponds to the total uncertainty in the sum of the predicted yields including all correlations. The ratios of the data to the sum of the simulated yields after the fit are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty in the MC simulation. |
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Figure 4-c:
Event yield in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel after the fit to the data for events with exactly two b-tagged jets, and zero additional non-b-tagged jet. The hatched band corresponds to the total uncertainty in the sum of the predicted yields including all correlations. The ratios of the data to the sum of the simulated yields after the fit are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty in the MC simulation. |
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Figure 4-d:
Distribution in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel after the fit to the data for events with zero or three or more b-tagged jets, and one additional non-b-tagged jet. The hatched band corresponds to the total uncertainty in the sum of the predicted yields including all correlations. The ratios of the data to the sum of the simulated yields after the fit are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty in the MC simulation. |
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Figure 4-e:
Distribution in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel after the fit to the data for events with exactly one b-tagged jets, and one additional non-b-tagged jet. The hatched band corresponds to the total uncertainty in the sum of the predicted yields including all correlations. The ratios of the data to the sum of the simulated yields after the fit are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty in the MC simulation. |
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Figure 4-f:
Distribution in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel after the fit to the data for events with exactly two b-tagged jets, and one additional non-b-tagged jet. The hatched band corresponds to the total uncertainty in the sum of the predicted yields including all correlations. The ratios of the data to the sum of the simulated yields after the fit are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty in the MC simulation. |
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Figure 4-g:
Distribution in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel after the fit to the data for events with zero or three or more b-tagged jets, and two additional non-b-tagged jets. The hatched band corresponds to the total uncertainty in the sum of the predicted yields including all correlations. The ratios of the data to the sum of the simulated yields after the fit are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty in the MC simulation. |
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Figure 4-h:
Distribution in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel after the fit to the data for events with exactly one b-tagged jets, and two additional non-b-tagged jets. The hatched band corresponds to the total uncertainty in the sum of the predicted yields including all correlations. The ratios of the data to the sum of the simulated yields after the fit are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty in the MC simulation. |
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Figure 4-i:
Distribution in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel after the fit to the data for events with exactly two b-tagged jets, and two additional non-b-tagged jets. The hatched band corresponds to the total uncertainty in the sum of the predicted yields including all correlations. The ratios of the data to the sum of the simulated yields after the fit are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty in the MC simulation. |
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Figure 4-j:
Distribution in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel after the fit to the data for events with zero or three or more b-tagged jets, and three or more additional non-b-tagged jets. The hatched band corresponds to the total uncertainty in the sum of the predicted yields including all correlations. The ratios of the data to the sum of the simulated yields after the fit are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty in the MC simulation. |
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Figure 4-k:
Distribution in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel after the fit to the data for events with exactly one b-tagged jets, and three or more additional non-b-tagged jets. The hatched band corresponds to the total uncertainty in the sum of the predicted yields including all correlations. The ratios of the data to the sum of the simulated yields after the fit are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty in the MC simulation. |
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Figure 4-l:
Event yield in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel after the fit to the data for events with exactly two b-tagged jets, and three or more additional non-b-tagged jets. The hatched band corresponds to the total uncertainty in the sum of the predicted yields including all correlations. The ratios of the data to the sum of the simulated yields after the fit are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty in the MC simulation. |
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Figure 5:
Distributions in the ${{{\mu ^{+}}} {{\mu ^{-}}}}$ channel after the fit to the data. The left (right) column shows events with exactly one (two) b-tagged jets. Events with zero, one, two, or three or more additional non-b-tagged jets are shown in the first, second, third, and fourth row, respectively. The hatched bands correspond to the total uncertainty in the sum of the predicted yields including all correlations. The ratios of the data to the sum of the simulated yields after the fit are shown in the lower panel of each figure. Here, the solid gray band represents the contribution of the statistical uncertainty in the MC simulation. |
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Figure 5-a:
Event yield in the ${{{\mu ^{+}}} {{\mu ^{-}}}}$ channel after the fit to the data for events with exactly one b-tagged jets and zero additional non-b-tagged jet. The hatched band corresponds to the total uncertainty in the sum of the predicted yields including all correlations. The ratios of the data to the sum of the simulated yields after the fit are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty in the MC simulation. |
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Figure 5-b:
Event yield in the ${{{\mu ^{+}}} {{\mu ^{-}}}}$ channel after the fit to the data for events with exactly two b-tagged jets and zero additional non-b-tagged jet. The hatched band corresponds to the total uncertainty in the sum of the predicted yields including all correlations. The ratios of the data to the sum of the simulated yields after the fit are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty in the MC simulation. |
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Figure 5-c:
Distribution in the ${{{\mu ^{+}}} {{\mu ^{-}}}}$ channel after the fit to the data for events with exactly one b-tagged jets and one additional non-b-tagged jet. The hatched band corresponds to the total uncertainty in the sum of the predicted yields including all correlations. The ratios of the data to the sum of the simulated yields after the fit are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty in the MC simulation. |
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Figure 5-d:
Distribution in the ${{{\mu ^{+}}} {{\mu ^{-}}}}$ channel after the fit to the data for events with exactly two b-tagged jets and one additional non-b-tagged jet. The hatched band corresponds to the total uncertainty in the sum of the predicted yields including all correlations. The ratios of the data to the sum of the simulated yields after the fit are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty in the MC simulation. |
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Figure 5-e:
Distribution in the ${{{\mu ^{+}}} {{\mu ^{-}}}}$ channel after the fit to the data for events with exactly one b-tagged jets and two additional non-b-tagged jets. The hatched band corresponds to the total uncertainty in the sum of the predicted yields including all correlations. The ratios of the data to the sum of the simulated yields after the fit are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty in the MC simulation. |
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Figure 5-f:
Distribution in the ${{{\mu ^{+}}} {{\mu ^{-}}}}$ channel after the fit to the data for events with exactly two b-tagged jets and two additional non-b-tagged jets. The hatched band corresponds to the total uncertainty in the sum of the predicted yields including all correlations. The ratios of the data to the sum of the simulated yields after the fit are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty in the MC simulation. |
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Figure 5-g:
Distribution in the ${{{\mu ^{+}}} {{\mu ^{-}}}}$ channel after the fit to the data for events with exactly one b-tagged jets and three or more additional non-b-tagged jets. The hatched band corresponds to the total uncertainty in the sum of the predicted yields including all correlations. The ratios of the data to the sum of the simulated yields after the fit are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty in the MC simulation. |
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Figure 5-h:
Event yield in the ${{{\mu ^{+}}} {{\mu ^{-}}}}$ channel after the fit to the data for events with exactly two b-tagged jets and three or more additional non-b-tagged jets. The hatched band corresponds to the total uncertainty in the sum of the predicted yields including all correlations. The ratios of the data to the sum of the simulated yields after the fit are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty in the MC simulation. |
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Figure 6:
Same distributions as in Fig. 5, but in the ${{\mathrm {e}^{+}} {\mathrm {e}^{-}}}$ channel. |
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Figure 6-a:
Same distributions as in Fig. 5, but in the ${{\mathrm {e}^{+}} {\mathrm {e}^{-}}}$ channel. |
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Figure 6-b:
Same distributions as in Fig. 5, but in the ${{\mathrm {e}^{+}} {\mathrm {e}^{-}}}$ channel. |
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Figure 6-c:
Same distributions as in Fig. 5, but in the ${{\mathrm {e}^{+}} {\mathrm {e}^{-}}}$ channel. |
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Figure 6-d:
Same distributions as in Fig. 5, but in the ${{\mathrm {e}^{+}} {\mathrm {e}^{-}}}$ channel. |
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Figure 6-e:
Same distributions as in Fig. 5, but in the ${{\mathrm {e}^{+}} {\mathrm {e}^{-}}}$ channel. |
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Figure 6-f:
Same distributions as in Fig. 5, but in the ${{\mathrm {e}^{+}} {\mathrm {e}^{-}}}$ channel. |
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Figure 6-g:
Same distributions as in Fig. 5, but in the ${{\mathrm {e}^{+}} {\mathrm {e}^{-}}}$ channel. |
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Figure 6-h:
Same distributions as in Fig. 5, but in the ${{\mathrm {e}^{+}} {\mathrm {e}^{-}}}$ channel. |
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Figure 7:
Normalized pulls and constraints of the nuisance parameters related to the modelling uncertainties for the cross section fit. The markers denote the fitted values, while the inner vertical bars represent the constraint and the outer vertical bars denote the additional uncertainty as determ $ {\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}} $ ined from pseudo-experiments. The constraint is defined as the ratio of the post-fit uncertainty to the pre-fit uncertainty of a given nuisance parameter, while the normalized pull is the difference between the post-fit and the pre-fit values of the nuisance parameter normalized to its pre-fit uncertainty. The horizontal lines at $\pm$1 represent the pre-fit uncertainty. |
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Figure 8:
Comparison of data (points) and pre-fit distributions of the expected signal and backgrounds from simulation (shaded histograms) used in the simultaneous fit of $ {\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}} $ and ${{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}}$ in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel. In the left column events with zero or three or more b-tagged jets are shown. The middle (right) column shows events with exactly one (two) b-tagged jets. Events with zero, one, two, or three or more additional non-b-tagged jets are shown in the first, second, third, and fourth row, respectively. The hatched bands correspond to the total uncertainty in the sum of the predicted yields. The ratios of data to the sum of the predicted yields are shown in the lower panel of each figure. Here, the solid gray band represents the contribution of the statistical uncertainty. |
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Figure 8-a:
Comparison of data (points) and pre-fit distribution of the expected signal and backgrounds from simulation (shaded histograms) used in the simultaneous fit of $ {\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}} $ and ${{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}}$ in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel for events with zero or three or more b-tagged jets and zero additional non-b-tagged jet. The hatched band corresponds to the total uncertainty in the sum of the predicted yields. The ratios of data to the sum of the predicted yields are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty. |
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Figure 8-b:
Comparison of data (points) and pre-fit distribution of the expected signal and backgrounds from simulation (shaded histograms) used in the simultaneous fit of $ {\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}} $ and ${{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}}$ in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel for events with exactly one b-tagged jets and zero additional non-b-tagged jet. The hatched band corresponds to the total uncertainty in the sum of the predicted yields. The ratios of data to the sum of the predicted yields are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty. |
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Figure 8-c:
Comparison of data (points) and pre-fit distribution of the expected signal and backgrounds from simulation (shaded histograms) used in the simultaneous fit of $ {\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}} $ and ${{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}}$ in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel for events with exactly two b-tagged jets and zero additional non-b-tagged jet. The hatched band corresponds to the total uncertainty in the sum of the predicted yields. The ratios of data to the sum of the predicted yields are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty. |
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Figure 8-d:
Comparison of data (points) and pre-fit distribution of the expected signal and backgrounds from simulation (shaded histograms) used in the simultaneous fit of $ {\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}} $ and ${{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}}$ in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel for events with zero or three or more b-tagged jets and one additional non-b-tagged jet. The hatched band corresponds to the total uncertainty in the sum of the predicted yields. The ratios of data to the sum of the predicted yields are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty. |
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Figure 8-e:
Comparison of data (points) and pre-fit distribution of the expected signal and backgrounds from simulation (shaded histograms) used in the simultaneous fit of $ {\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}} $ and ${{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}}$ in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel for events with exactly one b-tagged jets and one additional non-b-tagged jet. The hatched band corresponds to the total uncertainty in the sum of the predicted yields. The ratios of data to the sum of the predicted yields are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty. |
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Figure 8-f:
Comparison of data (points) and pre-fit distribution of the expected signal and backgrounds from simulation (shaded histograms) used in the simultaneous fit of $ {\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}} $ and ${{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}}$ in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel for events with exactly two b-tagged jets and one additional non-b-tagged jet. The hatched band corresponds to the total uncertainty in the sum of the predicted yields. The ratios of data to the sum of the predicted yields are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty. |
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Figure 8-g:
Comparison of data (points) and pre-fit distribution of the expected signal and backgrounds from simulation (shaded histograms) used in the simultaneous fit of $ {\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}} $ and ${{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}}$ in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel for events with zero or three or more b-tagged jets and two additional non-b-tagged jets. The hatched band corresponds to the total uncertainty in the sum of the predicted yields. The ratios of data to the sum of the predicted yields are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty. |
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Figure 8-h:
Comparison of data (points) and pre-fit distribution of the expected signal and backgrounds from simulation (shaded histograms) used in the simultaneous fit of $ {\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}} $ and ${{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}}$ in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel or events with exactly one b-tagged jets and two additional non-b-tagged jets. The hatched band corresponds to the total uncertainty in the sum of the predicted yields. The ratios of data to the sum of the predicted yields are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty. |
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Figure 8-i:
Comparison of data (points) and pre-fit distribution of the expected signal and backgrounds from simulation (shaded histograms) used in the simultaneous fit of $ {\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}} $ and ${{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}}$ in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel for events with exactly two b-tagged jets and two additional non-b-tagged jets. The hatched band corresponds to the total uncertainty in the sum of the predicted yields. The ratios of data to the sum of the predicted yields are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty. |
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Figure 8-j:
Comparison of data (points) and pre-fit distribution of the expected signal and backgrounds from simulation (shaded histograms) used in the simultaneous fit of $ {\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}} $ and ${{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}}$ in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel for events with zero or three or more b-tagged jets and three or more additional non-b-tagged jets. The hatched band corresponds to the total uncertainty in the sum of the predicted yields. The ratios of data to the sum of the predicted yields are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty. |
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Figure 8-k:
Comparison of data (points) and pre-fit distribution of the expected signal and backgrounds from simulation (shaded histograms) used in the simultaneous fit of $ {\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}} $ and ${{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}}$ in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel for events with exactly one b-tagged jets and three or more additional non-b-tagged jets. The hatched band corresponds to the total uncertainty in the sum of the predicted yields. The ratios of data to the sum of the predicted yields are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty. |
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Figure 8-l:
Comparison of data (points) and pre-fit distribution of the expected signal and backgrounds from simulation (shaded histograms) used in the simultaneous fit of $ {\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}} $ and ${{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}}$ in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel for events with exactly two b-tagged jets and three or more additional non-b-tagged jets. The hatched band corresponds to the total uncertainty in the sum of the predicted yields. The ratios of data to the sum of the predicted yields are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty. |
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Figure 9:
Comparison of data (points) and post-fit distributions of the expected signal and backgrounds from simulation (shaded histograms) used in the simultaneous fit of $ {\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}} $ and ${{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}}$ in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel. In the left column events with zero or three or more b-tagged jets are shown. The middle (right) column shows events with exactly one (two) b-tagged jets. Events with zero, one, two, or three or more additional non-b-tagged jets are shown in the first, second, third, and fourth row, respectively. The hatched bands correspond to the total uncertainty in the sum of the predicted yields and include the contribution from the top quark mass ($\Delta {{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}} $). The ratios of data to the sum of the predicted yields are shown in the lower panel of each figure. Here, the solid gray band represents the contribution of the statistical uncertainty. |
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Figure 9-a:
Comparison of data (points) and post-fit distributions of the expected signal and backgrounds from simulation (shaded histograms) used in the simultaneous fit of $ {\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}} $ and ${{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}}$ in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel for events with zero or three or more b-tagged jets and zero additional non-b-tagged jet. The hatched band corresponds to the total uncertainty in the sum of the predicted yields and include the contribution from the top quark mass ($\Delta {{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}} $). The ratios of data to the sum of the predicted yields are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty. |
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Figure 9-b:
Comparison of data (points) and post-fit distributions of the expected signal and backgrounds from simulation (shaded histograms) used in the simultaneous fit of $ {\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}} $ and ${{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}}$ in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel for events with exactly one b-tagged jets and zero additional non-b-tagged jet. The hatched band corresponds to the total uncertainty in the sum of the predicted yields and include the contribution from the top quark mass ($\Delta {{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}} $). The ratios of data to the sum of the predicted yields are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty. |
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Figure 9-c:
Comparison of data (points) and post-fit distributions of the expected signal and backgrounds from simulation (shaded histograms) used in the simultaneous fit of $ {\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}} $ and ${{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}}$ in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel for events with exactly two b-tagged jets and zero additional non-b-tagged jet. The hatched band corresponds to the total uncertainty in the sum of the predicted yields and include the contribution from the top quark mass ($\Delta {{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}} $). The ratios of data to the sum of the predicted yields are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty. |
png pdf |
Figure 9-d:
Comparison of data (points) and post-fit distributions of the expected signal and backgrounds from simulation (shaded histograms) used in the simultaneous fit of $ {\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}} $ and ${{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}}$ in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel for events with zero or three or more b-tagged jets and one additional non-b-tagged jet. The hatched band corresponds to the total uncertainty in the sum of the predicted yields and include the contribution from the top quark mass ($\Delta {{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}} $). The ratios of data to the sum of the predicted yields are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty. |
png pdf |
Figure 9-e:
Comparison of data (points) and post-fit distributions of the expected signal and backgrounds from simulation (shaded histograms) used in the simultaneous fit of $ {\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}} $ and ${{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}}$ in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel for events with exactly one b-tagged jets and one additional non-b-tagged jet. The hatched band corresponds to the total uncertainty in the sum of the predicted yields and include the contribution from the top quark mass ($\Delta {{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}} $). The ratios of data to the sum of the predicted yields are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty. |
png pdf |
Figure 9-f:
Comparison of data (points) and post-fit distributions of the expected signal and backgrounds from simulation (shaded histograms) used in the simultaneous fit of $ {\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}} $ and ${{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}}$ in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel for events with exactly two b-tagged jets and one additional non-b-tagged jet. The hatched band corresponds to the total uncertainty in the sum of the predicted yields and include the contribution from the top quark mass ($\Delta {{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}} $). The ratios of data to the sum of the predicted yields are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty. |
png pdf |
Figure 9-g:
Comparison of data (points) and post-fit distributions of the expected signal and backgrounds from simulation (shaded histograms) used in the simultaneous fit of $ {\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}} $ and ${{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}}$ in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel for events with zero or three or more b-tagged jets and two additional non-b-tagged jets. The hatched band corresponds to the total uncertainty in the sum of the predicted yields and include the contribution from the top quark mass ($\Delta {{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}} $). The ratios of data to the sum of the predicted yields are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty. |
png pdf |
Figure 9-h:
Comparison of data (points) and post-fit distributions of the expected signal and backgrounds from simulation (shaded histograms) used in the simultaneous fit of $ {\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}} $ and ${{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}}$ in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel for events with exactly one b-tagged jets and two additional non-b-tagged jets. The hatched band corresponds to the total uncertainty in the sum of the predicted yields and include the contribution from the top quark mass ($\Delta {{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}} $). The ratios of data to the sum of the predicted yields are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty. |
png pdf |
Figure 9-i:
Comparison of data (points) and post-fit distributions of the expected signal and backgrounds from simulation (shaded histograms) used in the simultaneous fit of $ {\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}} $ and ${{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}}$ in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel for events with exactly two b-tagged jets and two additional non-b-tagged jets. The hatched band corresponds to the total uncertainty in the sum of the predicted yields and include the contribution from the top quark mass ($\Delta {{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}} $). The ratios of data to the sum of the predicted yields are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty. |
png pdf |
Figure 9-j:
Comparison of data (points) and post-fit distributions of the expected signal and backgrounds from simulation (shaded histograms) used in the simultaneous fit of $ {\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}} $ and ${{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}}$ in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel for events with zero or three or more b-tagged jets and three or more additional non-b-tagged jets. The hatched band corresponds to the total uncertainty in the sum of the predicted yields and include the contribution from the top quark mass ($\Delta {{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}} $). The ratios of data to the sum of the predicted yields are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty. |
png pdf |
Figure 9-k:
Comparison of data (points) and post-fit distributions of the expected signal and backgrounds from simulation (shaded histograms) used in the simultaneous fit of $ {\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}} $ and ${{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}}$ in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel for events with exactly one b-tagged jets and three or more additional non-b-tagged jets. The hatched band corresponds to the total uncertainty in the sum of the predicted yields and include the contribution from the top quark mass ($\Delta {{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}} $). The ratios of data to the sum of the predicted yields are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty. |
png pdf |
Figure 9-l:
Comparison of data (points) and post-fit distributions of the expected signal and backgrounds from simulation (shaded histograms) used in the simultaneous fit of $ {\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}} $ and ${{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}}$ in the ${\mathrm {e}}^{\pm} {{\mu}}^{\mp}$ channel for events with exactly two b-tagged jets and three or more additional non-b-tagged jets. The hatched band corresponds to the total uncertainty in the sum of the predicted yields and include the contribution from the top quark mass ($\Delta {{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}} $). The ratios of data to the sum of the predicted yields are shown in the lower panel. Here, the solid gray band represents the contribution of the statistical uncertainty. |
png pdf |
Figure 10:
Normalized pulls and constraints of the nuisance parameters related to the modelling uncertainties for the simultaneous fit of ${\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}}$ and ${{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}}$. The markers denote the fitted value, while the inner vertical bars represent the constraint and the outer vertical bars denote the additional uncertainty as determined from pseudo-experiments. The constraint is defined as the ratio of the post-fit uncertainty to the pre-fit uncertainty of a given nuisance parameter, while the normalized pull is the difference between the post-fit and the pre-fit values of the nuisance parameter normalized to its pre-fit uncertainty. The horizontal lines at $\pm$1 represent the pre-fit uncertainty. |
png pdf |
Figure 11:
Left: $ {\chi ^2} $ versus $ {{\alpha _S}} $ obtained from the comparison of the measured ${\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}}$ value to the NNLO prediction in the ${\mathrm {\overline {MS}}}$ scheme using different PDFs (symbols of different styles). Right: ${{{\alpha _S}} ({m_\mathrm {{\mathrm {Z}}}})}$ obtained from the comparison of the measured ${\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}}$ value to the theoretical prediction using different PDF sets in the ${\mathrm {\overline {MS}}}$ scheme. The corresponding value of ${{m_\mathrm {{\mathrm {t}}}} ({m_\mathrm {{\mathrm {t}}}})}$ is given for each PDF set. The inner horizontal bars on the points represent the experimental and PDF uncertainties added in quadrature. The outer horizontal bars show the total uncertainties. The vertical line displays the world-average ${{{\alpha _S}} ({m_\mathrm {{\mathrm {Z}}}})}$ value [29], with the hatched band representing its uncertainty. |
png pdf |
Figure 11-a:
$ {\chi ^2} $ versus $ {{\alpha _S}} $ obtained from the comparison of the measured ${\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}}$ value to the NNLO prediction in the ${\mathrm {\overline {MS}}}$ scheme using different PDFs (symbols of different styles). |
png pdf |
Figure 11-b:
${{{\alpha _S}} ({m_\mathrm {{\mathrm {Z}}}})}$ obtained from the comparison of the measured ${\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}}$ value to the theoretical prediction using different PDF sets in the ${\mathrm {\overline {MS}}}$ scheme. The corresponding value of ${{m_\mathrm {{\mathrm {t}}}} ({m_\mathrm {{\mathrm {t}}}})}$ is given for each PDF set. The inner horizontal bars on the points represent the experimental and PDF uncertainties added in quadrature. The outer horizontal bars show the total uncertainties. The vertical line displays the world-average ${{{\alpha _S}} ({m_\mathrm {{\mathrm {Z}}}})}$ value [29], with the hatched band representing its uncertainty. |
png pdf |
Figure 12:
Values of $ {{m_\mathrm {{\mathrm {t}}}} ({m_\mathrm {{\mathrm {t}}}})} $ obtained from comparing the $ {\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}} $ measurement to the theoretical NNLO predictions using different PDF sets. The inner horizontal bars on the points represent the quadratic sum of the experimental, PDF, and $ {{{\alpha _S}} ({m_\mathrm {{\mathrm {Z}}}})} $ uncertainties, while the outer horizontal bars give the total uncertainties. |
png pdf |
Figure 13:
Values of $ {{{\alpha _S}} ({m_\mathrm {{\mathrm {Z}}}})} $ obtained in the comparison of the $ {\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}} $ measurement to the NNLO prediction using different PDFs, as a function of the $ {{m_\mathrm {{\mathrm {t}}}} ({m_\mathrm {{\mathrm {t}}}})} $ value used in the theoretical calculation. The results from using the different PDFs are shown by the bands with different shadings, with the band width corresponding to the quadratic sum of the experimental and PDF uncertainties in ${{{\alpha _S}} ({m_\mathrm {{\mathrm {Z}}}})}$. The resulting measured values of $ {{{\alpha _S}} ({m_\mathrm {{\mathrm {Z}}}})} $ are shown by the different style points at the $ {{m_\mathrm {{\mathrm {t}}}} ({m_\mathrm {{\mathrm {t}}}})} $ values used for each PDF. The inner vertical bars on the points represent the quadratic sum of the experimental and PDF uncertainties in ${{{\alpha _S}} ({m_\mathrm {{\mathrm {Z}}}})}$, while the outer vertical bars show the total uncertainties. |
Tables | |
png pdf |
Table 1:
The relative uncertainties in ${\sigma _{{{\mathrm {t}\overline {\mathrm {t}}}}}^{\text {vis}}}$ and ${\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}}$ and their sources, as obtained from the template fit. The uncertainty in the integrated luminosity and the MC statistical uncertainty are determined separately. The individual uncertainties are given without their correlations, which are however accounted for in the total uncertainties. Extrapolation uncertainties only affect ${\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}}$. For these uncertainties, the $\pm $ notation is used if a positive variation produces an increase in ${\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}}$, while the $\mp $ notation is used otherwise. |
png pdf |
Table 2:
The same as Table 1, but for the simultaneous fit of $ {\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}} $ and ${{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}}$. |
png pdf |
Table 3:
The absolute uncertainties in ${{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}}$ and their sources, from the simultaneous fit of $ {\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}} $ and ${{m_\mathrm {{\mathrm {t}}}} ^{\mathrm {MC}}}$. The MC statistical uncertainty is determined separately. The individual uncertainties are given without their correlations, which are however accounted for in the total uncertainties. |
png pdf |
Table 4:
Values of the top quark pole mass ${{m_\mathrm {{\mathrm {t}}}} ^{\text {pole}}}$ and strong coupling constant ${{{\alpha _S}} ({m_\mathrm {{\mathrm {Z}}}})}$ used in the different PDF sets. Also shown are the corresponding ${{m_\mathrm {{\mathrm {t}}}} ({m_\mathrm {{\mathrm {t}}}})}$ values obtained using the {RunDec} [82,83] conversion, the number of loops in the conversion, and the ${{\alpha _S}}$ range used to estimate the PDF uncertainties. |
png pdf |
Table 5:
Values of $ {{{\alpha _S}} ({m_\mathrm {{\mathrm {Z}}}})} $ with their uncertainties obtained from a comparison of the measured $ {\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}} $ value to the NNLO prediction in the $ {\mathrm {\overline {MS}}} $ scheme using different PDF sets. The first uncertainty is the combination of the experimental and PDF uncertainties, and the second is from the variation of the renormalization and factorization scales. |
png pdf |
Table 6:
Values of $ {{m_\mathrm {{\mathrm {t}}}} ({m_\mathrm {{\mathrm {t}}}})} $ obtained from the comparison of the $ {\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}} $ measurement with the NNLO predictions using different PDF sets. The first uncertainty shown comes from the experimental, PDF, and $ {{{\alpha _S}} ({m_\mathrm {{\mathrm {Z}}}})} $ uncertainties, and the second from the variation in the renormalization and factorization scales. |
png pdf |
Table 7:
Values of ${{m_\mathrm {{\mathrm {t}}}} ^{\text {pole}}}$ obtained by comparing the $ {\sigma _ {{\mathrm {t}\overline {\mathrm {t}}}}} $ measurement with predictions at NNLO+NNLL using different PDF sets. |
Summary |
A measurement of the top quark-antiquark pair production cross section $ {\sigma_\mathrm{t\bar{t}}} $ by the CMS Collaboration in proton-proton collisions at a centre-of-mass energy of 13 TeV is presented, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. Assuming a top quark mass in the simulation of ${{m_{\mathrm{t}}} ^{\mathrm{MC}}} = $ 172.5 GeV, a visible cross section is measured in the fiducial region using dilepton events ($\mathrm{e}^{\pm}\mu^{\mp}$ , $\mu^{+}\mu^{-}$, $\mathrm{e^{+}e^{-}}$) and then extrapolated to the full phase space. The total $ \mathrm{t\bar{t}} $ production cross section is found to be ${\sigma_\mathrm{t\bar{t}}} = $ 803 $\pm$ 2 (stat) $\pm$ 25 (syst) $\pm$ 20 (lumi) pb. The measurement is in good agreement with the theoretical prediction calculated to next-to-next-to-leading order in perturbative QCD, including soft-gluon resummation to next-to-next-to-leading logarithm. The measurement is repeated including $ {{m_{\mathrm{t}}} ^{\mathrm{MC}}} $ as an additional free parameter in the fit. This yields a cross section of ${\sigma_\mathrm{t\bar{t}}} = $ 815 $\pm$ 2 (stat) $\pm$ 29 (syst) $pm$ 20 (lumi) pb and a value of ${{m_{\mathrm{t}}} ^{\mathrm{MC}}} = $ 172.33 $\pm$ 0.14 (stat) $^{+0.66}_{-0.72}$ (syst) GeV, in good agreement with previous measurements. The value of $ {\sigma_\mathrm{t\bar{t}}} $ obtained in the simultaneous fit is further used to extract the values of the top quark mass and the strong coupling constant at next-to-next-to-leading order in the minimal subtraction renormalization scheme, as well as the value of the top quark pole mass for different sets of parton distribution functions. |
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Compact Muon Solenoid LHC, CERN |