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| CMS-PAS-TOP-15-006 | ||
| Measurement of the differential production cross section for top-quark pairs as a function of jet multiplicity in the lepton+jets final state at $\sqrt{s}= $ 8 TeV with the CMS detector | ||
| CMS Collaboration | ||
| July 2016 | ||
| Abstract: The top-quark pair differential production cross section in pp collisions at $ \sqrt{s} = $ 8 TeV as a function of the number of jets is measured in the lepton+jets ($\mathrm{e}$/$\mu$+jets) final state for an integrated luminosity of 19.7 fb$^{-1}$. The cross section is presented in the visible phase space of the measurement as well as extrapolated to the full phase space. The results are compared with theoretical predictions at next-to-leading order. The comparisons show good agreement between the data and the predictions within the experimental and theoretical uncertainties. | ||
| Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ; | ||
| Figures | |
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Figure 1-a:
Distribution of the number of selected jets (a), the missing transverse energy (b), the ${p_{\mathrm {T}}}$ and $\eta $ of all selected jets (c,d), and the ${p_{\mathrm {T}}}$ and $\eta $ of the leading jet (e,f), combining the $\mathrm{e}$+jets and $\mu $+jets channels. The lower part of each plot shows the ratio of the data to the MC predictions. The hashed areas represent the shape uncertainties affecting the MC signal and backgrounds. The normalization of the signal and background processes is discussed in the text. |
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Figure 1-b:
Distribution of the number of selected jets (a), the missing transverse energy (b), the ${p_{\mathrm {T}}}$ and $\eta $ of all selected jets (c,d), and the ${p_{\mathrm {T}}}$ and $\eta $ of the leading jet (e,f), combining the $\mathrm{e}$+jets and $\mu $+jets channels. The lower part of each plot shows the ratio of the data to the MC predictions. The hashed areas represent the shape uncertainties affecting the MC signal and backgrounds. The normalization of the signal and background processes is discussed in the text. |
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Figure 1-c:
Distribution of the number of selected jets (a), the missing transverse energy (b), the ${p_{\mathrm {T}}}$ and $\eta $ of all selected jets (c,d), and the ${p_{\mathrm {T}}}$ and $\eta $ of the leading jet (e,f), combining the $\mathrm{e}$+jets and $\mu $+jets channels. The lower part of each plot shows the ratio of the data to the MC predictions. The hashed areas represent the shape uncertainties affecting the MC signal and backgrounds. The normalization of the signal and background processes is discussed in the text. |
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Figure 1-d:
Distribution of the number of selected jets (a), the missing transverse energy (b), the ${p_{\mathrm {T}}}$ and $\eta $ of all selected jets (c,d), and the ${p_{\mathrm {T}}}$ and $\eta $ of the leading jet (e,f), combining the $\mathrm{e}$+jets and $\mu $+jets channels. The lower part of each plot shows the ratio of the data to the MC predictions. The hashed areas represent the shape uncertainties affecting the MC signal and backgrounds. The normalization of the signal and background processes is discussed in the text. |
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Figure 1-e:
Distribution of the number of selected jets (a), the missing transverse energy (b), the ${p_{\mathrm {T}}}$ and $\eta $ of all selected jets (c,d), and the ${p_{\mathrm {T}}}$ and $\eta $ of the leading jet (e,f), combining the $\mathrm{e}$+jets and $\mu $+jets channels. The lower part of each plot shows the ratio of the data to the MC predictions. The hashed areas represent the shape uncertainties affecting the MC signal and backgrounds. The normalization of the signal and background processes is discussed in the text. |
png pdf |
Figure 1-f:
Distribution of the number of selected jets (a), the missing transverse energy (b), the ${p_{\mathrm {T}}}$ and $\eta $ of all selected jets (c,d), and the ${p_{\mathrm {T}}}$ and $\eta $ of the leading jet (e,f), combining the $\mathrm{e}$+jets and $\mu $+jets channels. The lower part of each plot shows the ratio of the data to the MC predictions. The hashed areas represent the shape uncertainties affecting the MC signal and backgrounds. The normalization of the signal and background processes is discussed in the text. |
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Figure 2-a:
Combined differential visible $ {\mathrm{ t \bar{t} } } $ cross section as a function of the number of particle-level jets in the $\ell $+jets channel. The results are compared to predictions from various generators (a) or from MadGraph with various parameter sets (b). The vertical bars represent the total uncertainties and the intersecting horizontal bars represent the statistical uncertainties alone. In the ratio plot for mc@nlo and MadGraph with varied $Q^2$ value, the band represents the uncertainty of the measurement. |
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Figure 2-b:
Combined differential visible $ {\mathrm{ t \bar{t} } } $ cross section as a function of the number of particle-level jets in the $\ell $+jets channel. The results are compared to predictions from various generators (a) or from MadGraph with various parameter sets (b). The vertical bars represent the total uncertainties and the intersecting horizontal bars represent the statistical uncertainties alone. In the ratio plot for mc@nlo and MadGraph with varied $Q^2$ value, the band represents the uncertainty of the measurement. |
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Figure 3-a:
Combined differential visible $ {\mathrm{ t \bar{t} } } $ cross section as a function of the number of particle-level jets in the $\ell $+jets channel. The results are compared to predictions from various MC generators (a) and SHERPA $Q^{2}$ (b). The vertical bars represent the total uncertainties and the intersecting vertical bars represent the statistical uncertainties alone. In the ratio plot, the band represents the uncertainty of the measurement. |
png pdf |
Figure 3-b:
Combined differential visible $ {\mathrm{ t \bar{t} } } $ cross section as a function of the number of particle-level jets in the $\ell $+jets channel. The results are compared to predictions from various MC generators (a) and SHERPA $Q^{2}$ (b). The vertical bars represent the total uncertainties and the intersecting vertical bars represent the statistical uncertainties alone. In the ratio plot, the band represents the uncertainty of the measurement. |
| Tables | |
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Table 1:
Production cross section of $ {\mathrm{ t \bar{t} } } $ pairs versus the particle-level jet multiplicity in the $\ell $+jets channel. The relative statistical, experimental, theoretical and total uncertainties are also shown. Total uncertainties include the luminosity uncertainty of 2.6%. |
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Table 2:
Normalized production cross section of $ {\mathrm{ t \bar{t} } } $ pairs versus the particle-level jet multiplicity in the $\ell $+jets channel. The relative statistical, experimental, theoretical and total uncertainties are also shown. |
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Table 3:
Comparison between the measured differential production cross section and predictions from various generators. A $\chi ^{2}$ and a $p$-value are calculated using the covariance matrix of the measured cross sections. The number of degrees of freedom (NDF) are equal to the number of the jet multiplicity bins. |
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Table 4:
Associated production cross section of $ {\mathrm{ t \bar{t} } } $ pairs with 0-4 jets in the final state, from the combination of the $\mathrm{e}$+jets and $\mu $+jets channels, extrapolated to the full phase space. The relative statistical, experimental, theoretical and total uncertainties are also shown. Total uncertainties include the luminosity uncertainty of 2.6%. |
| Summary |
| The differential production cross section of a top-quark pair as a function of the number of jets is presented in the lepton+jet final state for an integrated luminosity of 19.7 fb$^{-1}$ at $\sqrt{s}= $ 8 TeV pp collisions. The cross section is presented in the visible phase space of the measurement for exactly 4-9 and 10 or more particle-level jets in the final state as well as to the extrapolated full phase space for equal or more than 0-4 additional jets. The results are compared with the theoretical predictions as well as other published experimental results. The comparisons show consistency with the predictions within the experimental and theoretical uncertainties. The measurement in the visible phase space have been performed in a way to be fully compatible with predictions at particle level for model testing purposes. |
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