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| CMS-PAS-SMP-19-001 | ||
| Measurement of the $\textrm{pp} \rightarrow \textrm{Z}\textrm{Z}$ production cross section at $\sqrt{s} = $ 13 TeV with the Run 2 data set | ||
| CMS Collaboration | ||
| March 2019 | ||
| Abstract: Four-lepton production in proton-proton collisions, $\textrm{pp} \rightarrow (\textrm{Z}/\gamma^*)(\textrm{Z}/\gamma^*) \rightarrow 4\ell$, where $\ell$ = e or $\mu$, is studied at a center-of-mass energy of 13 TeV with the CMS detector at the LHC. The data samples correspond to integrated luminosities of 41.5 and 59.7 fb$^{-1}$, collected in 2017 and 2018 running periods respectively. By combining the 2017 and 2018 results with the previously published 2016 results, the ZZ production cross section is measured, $\sigma_{tot} (\textrm{pp} \rightarrow \textrm{ZZ}) =$ 17.1 $\pm$ 0.3 (stat) $\pm$ 0.4 (syst) $\pm$ 0.4 (theo) $\pm$ 0.3 (lumi) pb, for events with two opposite-sign, same-flavor lepton pairs produced in the mass region 60 $ < m_{\ell^+\ell^-} < $ 120 GeV. The measured cross section value is consistent with standard model predictions. | ||
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Links:
CDS record (PDF) ;
CADI line (restricted) ;
These preliminary results are superseded in this paper, EPJC 81 (2021) 200. The superseded preliminary plots can be found here. |
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| Figures | |
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Figure 1:
Distributions of (a) $m_{\mathrm{Z} \mathrm{Z}}$ for ZZ events with 60 $ < m_{\mathrm{Z} _1, \mathrm{Z} _2} < $ 120 GeV; (b) mass of selected Z boson candidates; (c) transverse momentum of the ZZ system ; (d) transverse momentum of individual Z boson candidates. All decay channels for both 2017 and 2018 data taking periods are added together. The results correspond to an integrated luminosity of 101.2 fb$^{-1}$. Points represent the data, shaded histograms represent the expected standard model predictions and reducible background estimated from data. |
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Figure 1-a:
Distributions of (a) $m_{\mathrm{Z} \mathrm{Z}}$ for ZZ events with 60 $ < m_{\mathrm{Z} _1, \mathrm{Z} _2} < $ 120 GeV; (b) mass of selected Z boson candidates; (c) transverse momentum of the ZZ system ; (d) transverse momentum of individual Z boson candidates. All decay channels for both 2017 and 2018 data taking periods are added together. The results correspond to an integrated luminosity of 101.2 fb$^{-1}$. Points represent the data, shaded histograms represent the expected standard model predictions and reducible background estimated from data. |
png pdf |
Figure 1-b:
Distributions of (a) $m_{\mathrm{Z} \mathrm{Z}}$ for ZZ events with 60 $ < m_{\mathrm{Z} _1, \mathrm{Z} _2} < $ 120 GeV; (b) mass of selected Z boson candidates; (c) transverse momentum of the ZZ system ; (d) transverse momentum of individual Z boson candidates. All decay channels for both 2017 and 2018 data taking periods are added together. The results correspond to an integrated luminosity of 101.2 fb$^{-1}$. Points represent the data, shaded histograms represent the expected standard model predictions and reducible background estimated from data. |
png pdf |
Figure 1-c:
Distributions of (a) $m_{\mathrm{Z} \mathrm{Z}}$ for ZZ events with 60 $ < m_{\mathrm{Z} _1, \mathrm{Z} _2} < $ 120 GeV; (b) mass of selected Z boson candidates; (c) transverse momentum of the ZZ system ; (d) transverse momentum of individual Z boson candidates. All decay channels for both 2017 and 2018 data taking periods are added together. The results correspond to an integrated luminosity of 101.2 fb$^{-1}$. Points represent the data, shaded histograms represent the expected standard model predictions and reducible background estimated from data. |
png pdf |
Figure 1-d:
Distributions of (a) $m_{\mathrm{Z} \mathrm{Z}}$ for ZZ events with 60 $ < m_{\mathrm{Z} _1, \mathrm{Z} _2} < $ 120 GeV; (b) mass of selected Z boson candidates; (c) transverse momentum of the ZZ system ; (d) transverse momentum of individual Z boson candidates. All decay channels for both 2017 and 2018 data taking periods are added together. The results correspond to an integrated luminosity of 101.2 fb$^{-1}$. Points represent the data, shaded histograms represent the expected standard model predictions and reducible background estimated from data. |
png pdf |
Figure 2:
Distributions of (a) transverse momentum and (b) pseudorapidity for individual leptons. The results correspond to an integrated luminosity of 101.2 fb$^{-1}$. Points represent the data, shaded histograms represent the expected standard model predictions and reducible background estimated from data. |
png pdf |
Figure 2-a:
Distributions of (a) transverse momentum and (b) pseudorapidity for individual leptons. The results correspond to an integrated luminosity of 101.2 fb$^{-1}$. Points represent the data, shaded histograms represent the expected standard model predictions and reducible background estimated from data. |
png pdf |
Figure 2-b:
Distributions of (a) transverse momentum and (b) pseudorapidity for individual leptons. The results correspond to an integrated luminosity of 101.2 fb$^{-1}$. Points represent the data, shaded histograms represent the expected standard model predictions and reducible background estimated from data. |
png pdf |
Figure 3:
The total ZZ cross section as a function of the proton-proton center-of-mass energy. Results from the CMS and ATLAS experiments are compared to predictions from matrix at NNLO in QCD, and mcfm at NLO in QCD. The mcfm prediction also includes gluon-gluon initiated production at LO in QCD. Both predictions use NNPDF3.0 PDF sets and fixed scales $\mu _\mathrm {F} = \mu _\mathrm {R} = m_{\mathrm{Z}}$. Details of the calculations and uncertainties are given in the text. The ATLAS measurements were performed with a $\mathrm{Z} $ boson mass window of 66-116 GeV, instead of 60-120 GeV used by CMS, and are corrected for the resulting 1.6% difference in acceptance. Measurements at the same center-of-mass energy are shifted slightly along the horizontal axis for clarity. |
| Tables | |
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Table 1:
The contributions of each source of systematic uncertainty in the cross section measurements. The integrated luminosity uncertainty, and the PDF and scale uncertainties, are considered separately. All other uncertainties are added in quadrature into a single systematic uncertainty. Uncertainties that vary by decay channel are listed as a range. |
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Table 2:
The observed and expected yields of ZZ events, and estimated yields of background events, shown for each final state and summed in the total expected yield. First uncertainty is statistical, second is systematic. The uncertainties listed as 0.0 are less than 0.1. |
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Table 3:
The measured fiducial cross section for each data sample, and combined. The published result from Ref. [5] is also included. |
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Table 4:
The measured total $\sigma ({\mathrm{p}} {\mathrm{p}} \to {\mathrm{Z} \mathrm{Z}})$ cross section for each data sample, and combined. The published result from Ref. [5] is also included. |
| Summary |
| Four-lepton production in proton-proton collisions, ${\mathrm{p}}{\mathrm{p}} \to (\mathrm{Z} / \gamma^*)(\mathrm{Z} /\gamma^*) \to 4\ell$, where $\ell = $ e or $\mu$, was studied at a center-of-mass energy of 13 TeV with the CMS detector at the LHC. The data sample corresponds to an integrated luminosity of 41.5 fb$^{-1}$ and 59.7 fb$^{-1}$, collected in 2017 and 2018 running periods respectively. By combining the 2017 and 2018 results with the previously published 2016 results, the ZZ production cross section was measured, $\sigma_{tot} (\textrm{pp} \rightarrow \textrm{ZZ}) =$ 17.1 $\pm$ 0.3 (stat) $\pm$ 0.4 (syst) $\pm$ 0.4 (theo) $\pm$ 0.3 (lumi) pb, for events with two opposite-sign, same-flavor lepton pairs produced in the mass region 60 $ < m_{\ell^+\ell^-} < $ 120 GeV. Measured cross section value is consistent with the standard model predictions. |
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