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| CMS-PAS-SMP-21-013 | ||
| Observation of WW from double-parton scattering in proton-proton collisions at $\sqrt{s} = $ 13 TeV | ||
| CMS Collaboration | ||
| March 2022 | ||
| Abstract: The first observation of WW production from double-parton scattering processes using same-charge electron-muon and dimuon events in proton-proton collisions is reported. The data sample corresponds to an integrated luminosity of 138 fb$^{-1}$ recorded at a center-of-mass energy of 13 TeV using the CMS detector at the CERN LHC during 2016-2018. Multivariate classifiers are used to distinguish the signal process from the main backgrounds. A maximum likelihood fit is performed to extract the signal cross section. The observed significance of the signal is 6.2 standard deviations, where a significance of 6.7 standard deviations is expected based on the model of mutli-parton interactions as implemented in PYTHIA. Cross section measurements for leptocially decaying W bosons in an charge-inclusive phase space and in a $\mathrm{W}^{\pm}\mathrm{W}^{\pm}$ fiducial region are reported. The measured inclusive cross section is 0.16 $\pm$ 0.02 (stat) $\pm$ 0.02 (syst) $\pm$ 0.02 (model) pb, while the measured fiducial cross section is 6.27 $\pm$ 0.69 (stat) $\pm$ 0.78 (syst) fb. Sensitivity towards parton correlations is probed using the pseudorapidity-based lepton asymmetry variable. | ||
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Links:
CDS record (PDF) ;
CADI line (restricted) ;
These preliminary results are superseded in this paper, PRL 131 (2023) 091803. The superseded preliminary plots can be found here. |
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| Figures | |
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Figure 1:
Production diagrams for leptonically-decaying $\mathrm{W} ^{\pm}\mathrm{W} ^{\pm}$ via DPS (left) and via SPS (middle and right). |
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Figure 1-a:
Production diagrams for leptonically-decaying $\mathrm{W} ^{\pm}\mathrm{W} ^{\pm}$ via DPS (left) and via SPS (middle and right). |
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Figure 1-b:
Production diagrams for leptonically-decaying $\mathrm{W} ^{\pm}\mathrm{W} ^{\pm}$ via DPS (left) and via SPS (middle and right). |
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Figure 1-c:
Production diagrams for leptonically-decaying $\mathrm{W} ^{\pm}\mathrm{W} ^{\pm}$ via DPS (left) and via SPS (middle and right). |
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Figure 2:
Postfit distribution of the final BDT classifier output for the four lepton-flavor and charge categories. The SPS $\mathrm{W} ^{\pm}\mathrm{W} ^{\pm}$ and ${\mathrm{t}} {\mathrm{\bar{t}}}\mathrm{W} /\mathrm{Z}$ contributions are grouped as the "Rare'' background. The postfit uncertainty in the prediction is shown as the shaded band. The bottom panels show the ratio of data to the sum of all background contributions in the black markers along with the signal shown using a red line. The band represents the postfit background uncertainty, which includes both the statistical and systematic components. The vertical error bars on the data points represent the statistical uncertainty in the data. |
| Summary |
| The first observation of WW production from double-parton scattering processes in proton-proton collisions at $\sqrt{s}$ = 13 TeV has been reported. The analyzed data set corresponds to an integrated luminosity of 138 fb$^{-1}$, collected using the CMS detector at the LHC. Events are selected by requiring same-charge electron-muon or dimuon pairs with moderate missing transverse momentum and low jet multiplicity. Boosted decision tree classifiers are used to discriminate between the signal and the dominant background processes. The observed significance is 6.2 standard deviations, where a significance of 6.7 standard deviations is expected based on predictions from PYTHIA. A cross section measurement in the charge-inclusive WW phase space is extracted which leads to an effective cross section parameter of $\sigma_{\text{eff}}=$ 12.16$^{+ 2.88}_{- 2.17}$ mb. A cross section measurement in a fiducial region is also reported which is consistent with PYTHIA 8 predictions. |
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Compact Muon Solenoid LHC, CERN |
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