CMS-PAS-TOP-20-004

CMS-PAS-TOP-20-004
Measurement of the inclusive $\mathrm{t\bar{t}}$ production cross section in pp collisions at $\sqrt{s} = $ 5.02 TeV
CMS Collaboration
March 2021

Abstract: The top quark pair production cross section is measured in proton-proton collisions at a center-of-mass energy of 5.02 TeV. The data collected in 2017 by the CMS experiment at the LHC corresponding to an integrated luminosity of 304 pb$^{-1}$ are analyzed. The measurement is performed using events with one electron and one muon of opposite sign, and at least two jets. The measured cross section is found to be 60.3 $\pm$ 5.0 (stat) $\pm$ 2.8 (syst) $\pm$ 0.9 (lum) pb. To reduce the statistical uncertainty, a combination with the result in the $\ell+$jets channel, based on 27.4 pb$^{-1}$ of data collected in 2015 at the same center-of-mass energy of 5.02 TeV, is then performed, obtaining a value of 62.6 $\pm$ 4.1 (stat) $\pm$ 3.0 (syst+lumi) pb, with a total uncertainty of 7.9%, in agreement with the standard model.
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ; These preliminary results are superseded in this paper, Submitted to JHEP. The superseded preliminary plots can be found here.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: Leading lepton ${p_{\mathrm {T}}}$ (top-left), sub-leading lepton ${p_{\mathrm {T}}}$ (top-right), leading jet ${p_{\mathrm {T}}}$ (bottom-left) and jet multiplicity (bottom-right) in the selected events. The hatcheds band correspond to systematic and statistical errors.
png pdf	Figure 1-a: Leading lepton ${p_{\mathrm {T}}}$ (top-left), sub-leading lepton ${p_{\mathrm {T}}}$ (top-right), leading jet ${p_{\mathrm {T}}}$ (bottom-left) and jet multiplicity (bottom-right) in the selected events. The hatcheds band correspond to systematic and statistical errors.
png pdf	Figure 1-b: Leading lepton ${p_{\mathrm {T}}}$ (top-left), sub-leading lepton ${p_{\mathrm {T}}}$ (top-right), leading jet ${p_{\mathrm {T}}}$ (bottom-left) and jet multiplicity (bottom-right) in the selected events. The hatcheds band correspond to systematic and statistical errors.
png pdf	Figure 1-c: Leading lepton ${p_{\mathrm {T}}}$ (top-left), sub-leading lepton ${p_{\mathrm {T}}}$ (top-right), leading jet ${p_{\mathrm {T}}}$ (bottom-left) and jet multiplicity (bottom-right) in the selected events. The hatcheds band correspond to systematic and statistical errors.
png pdf	Figure 1-d: Leading lepton ${p_{\mathrm {T}}}$ (top-left), sub-leading lepton ${p_{\mathrm {T}}}$ (top-right), leading jet ${p_{\mathrm {T}}}$ (bottom-left) and jet multiplicity (bottom-right) in the selected events. The hatcheds band correspond to systematic and statistical errors.
png pdf	Figure 2: Inclusive ${\mathrm{t} {}\mathrm{\bar{t}}}$ cross section in pp collisions as a function of the center-of-mass energy; previous CMS measurements at $\sqrt{s} =$ 7, 8 [6,7], and 13 [11,2] TeV in the separate $\ell $+jets and dilepton channels are displayed, along with the combined measurement at 5.02 TeV presented in this analysis. The NNLO+NNLL theoretical prediction [26] using the NNPDF3.1 [22] PDF set with $ {\alpha _\mathrm {S}} (m_{\mathrm{Z}})=$ 0.118 and $m_{\mathrm{t}} = $ 172.5 GeV is shown in the main plot. In the inset, the combined measurement is shown together with previous measurements at 5.02 TeV [3], and additional predictions at $\sqrt{s} =$ 5.02 TeV using the MMHT14 [50], CT18 [51], and ABMP16 [52] NNLO PDF sets, the latter with $ {\alpha _\mathrm {S}} (m_{\mathrm{Z}})=$ 0.115 and $m_{\mathrm{t}} = $ 170.4 GeV, are compared, along with the NNPDF3.1 NNLO prediction, to the individual and combined results from this analysis. The vertical bars and bands represent the total uncertainties in the data and in the predictions, respectively.

Tables
png pdf	Table 1: Summary of MC samples used to model the signal and background processes. The column "cross section order'' corresponds to the QCD or electroweak ("EWK'') precision used to normalize the distributions provided by the generators. Where no reference is given, the precision of the MC simulation is kept.
png pdf	Table 2: Summary of the statistical and systematic uncertainty sources on the ${\mathrm{t} {}\mathrm{\bar{t}}}$ cross section measurement.
png pdf	Table 3: Event yields for all the processes at the final level of selection. The sources of uncertainty correspond to statistical and systematic uncertainty, respectively.

Summary

A measurement of the top quark pair production cross section at a center-of-mass energy of 5.02 TeV is presented for events with one electron and one muon of opposite sign, and at least two jets, using proton-proton collisions collected by the CMS experiment in 2017 and corresponding to an integrated luminosity of 304 pb$^{-1}$. The measured cross section is found to be $\sigma_\mathrm{t\bar{t}}=$ 60.3 $\pm$ 5.0 (stat) $\pm$ 2.8 (syst) $\pm$ 0.9 (lumi) pb. To reduce the statistical uncertainty in the result, a statistical combination with the $\ell+$jets result of Ref. [3], using a data set collected in 2015 corresponding to a luminosity of 27.4 pb$^{-1}$, is performed, obtaining a measurement of 62.6 $\pm$ 4.1 (stat) $\pm$ 3.0 (syst+lumi) pb, with a total uncertainty of 7.9%, in agreement with the prediction from the standard model.

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