CMS-PAS-TOP-23-005

CMS-PAS-TOP-23-005
Measurement of the inclusive $ \mathrm{t\bar{t}} $ cross section in final states with one lepton and additional jets at 5.02 TeV with 2017 data
CMS Collaboration
11 April 2024

Abstract: A measurement of the top quark pair production cross section in proton-proton collisions at a centre-of-mass energy of 5.02 TeV is presented. The data were collected in a low-energy and low-intensity LHC run in autumn 2017, and correspond to an integrated luminosity of 302 pb$^{-1}$. The measurement is performed using events with one electron or muon, and multiple jets. Events are classified based on the number of all reconstructed jets and of the b-tagged jets; the signal selection includes the usage of multivariate analysis techniques. The measured cross section is 61.4 $ \pm $ 1.6 (stat) $^{+2.7}_{-2.6}$ (syst) $\pm$ 1.2 (lumi) pb. A combination with the result in the dilepton channel based on the same data set results in a value of 61.2 $ ^{+1.6}_{-1.5} $ (stat) $^{+2.6}_{-2.3}$ (syst) $\pm$ 1.2 (lumi) pb, in agreement with the standard model prediction of 69.5 $ ^{+2.9}_{-3.1} $ pb (at next-to-next-to-leading-order in QCD).
Links: CDS record (PDF) ; Physics Briefing ; CADI line (restricted) ; These preliminary results are superseded in this paper, Submitted to JHEP. The superseded preliminary plots can be found here.

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Ranking of the input variables of the random forest. Importance in the horizontal axis is computed as the mean of accumulation of the impurity decrease within each tree [51].
png pdf	Figure 2: Distributions for data and expected signal and background contributions of the most discriminating input variables used for the random forest training, $ \Delta R_\mathrm{med}(\mathrm{j,j')} $ (left) and $ \mathit{m}(\mathrm{u},\mathrm{u'}) $ (right), in the 3j1b category, before the maximum likelihood fit. The vertical error bars represent the statistical uncertainty in the data, and the shaded band the experimental uncertainty in the prediction (not including MC statistics). The lower panels show the data-to-prediction ratio. The first and last bins in each distribution include underflow and overflow events, respectively.
png pdf	Figure 2-a: Distributions for data and expected signal and background contributions of the most discriminating input variables used for the random forest training, $ \Delta R_\mathrm{med}(\mathrm{j,j')} $ (left) and $ \mathit{m}(\mathrm{u},\mathrm{u'}) $ (right), in the 3j1b category, before the maximum likelihood fit. The vertical error bars represent the statistical uncertainty in the data, and the shaded band the experimental uncertainty in the prediction (not including MC statistics). The lower panels show the data-to-prediction ratio. The first and last bins in each distribution include underflow and overflow events, respectively.
png pdf	Figure 2-b: Distributions for data and expected signal and background contributions of the most discriminating input variables used for the random forest training, $ \Delta R_\mathrm{med}(\mathrm{j,j')} $ (left) and $ \mathit{m}(\mathrm{u},\mathrm{u'}) $ (right), in the 3j1b category, before the maximum likelihood fit. The vertical error bars represent the statistical uncertainty in the data, and the shaded band the experimental uncertainty in the prediction (not including MC statistics). The lower panels show the data-to-prediction ratio. The first and last bins in each distribution include underflow and overflow events, respectively.
png pdf	Figure 3: Distributions for data and expected signal and background contributions of the MVA score for the $ e $+jets (left) and $ \mu $+jets (right) channels in the 3j1b category, before the maximum likelihood fit. The vertical error bars represent the statistical uncertainty in the data, and the shaded band the experimental uncertainty in the prediction (not including MC statistics). The lower panels show the data-to-prediction ratio. The first and last bins in each distribution include underflow and overflow events, respectively.
png	Figure 3-a: Distributions for data and expected signal and background contributions of the MVA score for the $ e $+jets (left) and $ \mu $+jets (right) channels in the 3j1b category, before the maximum likelihood fit. The vertical error bars represent the statistical uncertainty in the data, and the shaded band the experimental uncertainty in the prediction (not including MC statistics). The lower panels show the data-to-prediction ratio. The first and last bins in each distribution include underflow and overflow events, respectively.
png	Figure 3-b: Distributions for data and expected signal and background contributions of the MVA score for the $ e $+jets (left) and $ \mu $+jets (right) channels in the 3j1b category, before the maximum likelihood fit. The vertical error bars represent the statistical uncertainty in the data, and the shaded band the experimental uncertainty in the prediction (not including MC statistics). The lower panels show the data-to-prediction ratio. The first and last bins in each distribution include underflow and overflow events, respectively.
png pdf	Figure 4: Observed and predicted number of events in each of the eight categories of the signal region, before the maximum likelihood fit. The vertical error bars represent the statistical uncertainty in the data, and the shaded band the experimental and theoretical uncertainty in the prediction. The lower panels show the data-to-prediction ratio.
png pdf	Figure 5: Distributions for the $ e $+jets final state after the maximum likelihood fit: MVA score bins for the 3j1b category and $ \Delta R_\mathrm{med}(\mathrm{j,j')} $ bins for the other categories. The vertical error bars represent the statistical uncertainty in the data, and the shaded band the uncertainty in the prediction. All uncertainties considered in the analysis are included in the uncertainty band. The lower panels show the data-to-prediction ratio. The first and last bins in each distribution include underflow and overflow events, respectively.
png pdf	Figure 6: Distributions for the $ \mu $+jets final state after the maximum likelihood fit: MVA score bins for the 3j1b category and $ \Delta R_\mathrm{med}(\mathrm{j,j')} $ bins for the other categories. The vertical error bars represent the statistical uncertainty in the data, and the shaded band the uncertainty in the prediction. All uncertainties considered in the analysis are included in the uncertainty band. The lower panels show the data-to-prediction ratio. The first and last bins in each distribution include underflow and overflow events, respectively.
png pdf	Figure 9: Summary of the most recent measurements from the ATLAS [3] and CMS Collaborations using data collected at 5 TeV.

Tables
png pdf	Table 1: Summary of MC samples used to model the signal and background processes. The last column corresponds to the QCD or electroweak (EW) precision used to normalize the distributions provided by the generators. The predictions for $ \mathrm{t} \overline{\mathrm{t}} $, $ t $ channel and $ \mathrm{t}\mathrm{W} $ are calculated using the PDF4LHC prescription [31].
png pdf	Table 2: Summary of the variables used for the MVA training.

Summary

A measurement of the top quark pair production cross section in proton-proton collisions at a centre-of-mass energy of 5.02 TeV is performed for events with one electron or one muon and multiple jets using data collected by the CMS experiment in 2017, corresponding to an integrated luminosity of 302 pb$^{-1}$. The dominant background sources in the analysis are W+jets and tW processes for which MC simulations are used to estimate their contribution. In addition, the contribution from QCD multijet events is estimated from data. The measurement is done via a maximum likelihood fit to eight event categories defined in terms of the number of jets and b-tagged jets. The cross section is found to be 61.4 $ \pm $ 1.6 (stat) $ ^{+2.7}_{-2.6} $ (syst) $ \pm $ 1.2 (lumi) pb. This measurement is combined with the result obtained in the dilepton channel, based on the same data set, resulting in a value of 61.2 $ ^{+1.6}_{-1.5} $ (stat) $ ^{+2.6}_{-2.3} $ (syst) $ \pm $ 1.2 (lumi) pb. In both cases, the dominant uncertainties are those associated with the luminosity and with the b tagging scale factors for heavy flavours. This result is in agreement with the standard model prediction and with previous measurements from CMS and ATLAS. A summary plot of previous CMS and ATLAS measurements, together with the ones presented in this analysis (as well as those for the $ e $+jets and $ \mu $+jets channels separately) can be seen in Fig. 9.

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