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| CMS-PAS-SMP-21-001 | ||
| First observation of the electroweak production of a leptonically decaying W$^{+}$W$^{-}$ pair in association with two jets in $\sqrt{s} = $ 13 TeV pp collisions. | ||
| CMS Collaboration | ||
| November 2021 | ||
| Abstract: The first observation of the electroweak production of a W$^{+}$W$^{-}$ pair in association with two jets, with both W bosons decaying leptonically, is reported. The data sample corresponds to 138 fb$^{-1}$ of proton-proton collisions at 13 TeV. Events are selected by requiring two leptons (electrons or muons) and two jets with large pseudorapidity separation and high invariant mass. Events are categorized based on the flavour of final state leptons. A signal is observed with a significance of 5.6 standard deviations and the measured fiducial cross section is 10.2 $\pm$ 2.0 fb. The fiducial volume is required to have two oppositely-charged leptons in the $ | \eta | < $ 2.5 region with $p_{\mathrm{T}} > $ 25 GeV and $p_{\mathrm{T}} > $ 13 GeV respectively, having an invariant mass greater than 50 GeV; additionaly, at least two jets in the $ | \eta | < $ 4.7 region with a cone size $\Delta R = $ 0.4 and $p_{\mathrm{T}} > $ 30 GeV are selected, having a pseudorapidity gap larger than 2.5 and an invariant mass greater than 300 GeV. | ||
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Links:
CDS record (PDF) ;
CADI line (restricted) ;
These preliminary results are superseded in this paper, Submitted to PLB. The superseded preliminary plots can be found here. |
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| Figures | |
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Figure 1:
Examples of Feynman diagrams for the EW (left, middle) and QCD (right) production of W$^{+}$W$^{-}$. |
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Figure 1-a:
Examples of Feynman diagrams for the EW (left, middle) and QCD (right) production of W$^{+}$W$^{-}$. |
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Figure 1-b:
Examples of Feynman diagrams for the EW (left, middle) and QCD (right) production of W$^{+}$W$^{-}$. |
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Figure 1-c:
Examples of Feynman diagrams for the EW (left, middle) and QCD (right) production of W$^{+}$W$^{-}$. |
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Figure 2:
Post-fit DNN output distributions in the e$\mu $ signal region for $ {Z_{\ell \ell}} < $ 1 (left) and $ {Z_{\ell \ell}} \geq $ 1 (right). |
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Figure 2-a:
Post-fit DNN output distributions in the e$\mu $ signal region for $ {Z_{\ell \ell}} < $ 1 (left) and $ {Z_{\ell \ell}} \geq $ 1 (right). |
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Figure 2-b:
Post-fit DNN output distributions in the e$\mu $ signal region for $ {Z_{\ell \ell}} < $ 1 (left) and $ {Z_{\ell \ell}} \geq $ 1 (right). |
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Figure 3:
Post-fit ${m_{\mathrm {jj}}}$ distribution for the signal regions in same-flavour categories (ee and $\mu \mu $ combined) for $ {Z_{\ell \ell}} < $ 1 (left) and $ {Z_{\ell \ell}} \geq $ 1 (right). For each plot, the first bin contains the number of events in the 300 $ < {m_{\mathrm {jj}}} [ GeV ] < $ 500 and 2.5 $ < {\Delta \eta _{\mathrm {jj}}} < $ 3.5 category, the second bin those in the 300 $ < {m_{\mathrm {jj}}} [ GeV ] < $ 500 and $ {\Delta \eta _{\mathrm {jj}}} > $ 3.5 category, and the third bin those in the $ {m_{\mathrm {jj}}} > $ 500 GeV and 2.5 $ < {\Delta \eta _{\mathrm {jj}}} < $ 3.5 category. The last five bins represent the ${m_{\mathrm {jj}}}$ distribution in the $ {m_{\mathrm {jj}}} > $ 500 GeV and $ {\Delta \eta _{\mathrm {jj}}} > $ 3.5 category normalized to the width of the bins. |
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Figure 3-a:
Post-fit ${m_{\mathrm {jj}}}$ distribution for the signal regions in same-flavour categories (ee and $\mu \mu $ combined) for $ {Z_{\ell \ell}} < $ 1 (left) and $ {Z_{\ell \ell}} \geq $ 1 (right). For each plot, the first bin contains the number of events in the 300 $ < {m_{\mathrm {jj}}} [ GeV ] < $ 500 and 2.5 $ < {\Delta \eta _{\mathrm {jj}}} < $ 3.5 category, the second bin those in the 300 $ < {m_{\mathrm {jj}}} [ GeV ] < $ 500 and $ {\Delta \eta _{\mathrm {jj}}} > $ 3.5 category, and the third bin those in the $ {m_{\mathrm {jj}}} > $ 500 GeV and 2.5 $ < {\Delta \eta _{\mathrm {jj}}} < $ 3.5 category. The last five bins represent the ${m_{\mathrm {jj}}}$ distribution in the $ {m_{\mathrm {jj}}} > $ 500 GeV and $ {\Delta \eta _{\mathrm {jj}}} > $ 3.5 category normalized to the width of the bins. |
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Figure 3-b:
Post-fit ${m_{\mathrm {jj}}}$ distribution for the signal regions in same-flavour categories (ee and $\mu \mu $ combined) for $ {Z_{\ell \ell}} < $ 1 (left) and $ {Z_{\ell \ell}} \geq $ 1 (right). For each plot, the first bin contains the number of events in the 300 $ < {m_{\mathrm {jj}}} [ GeV ] < $ 500 and 2.5 $ < {\Delta \eta _{\mathrm {jj}}} < $ 3.5 category, the second bin those in the 300 $ < {m_{\mathrm {jj}}} [ GeV ] < $ 500 and $ {\Delta \eta _{\mathrm {jj}}} > $ 3.5 category, and the third bin those in the $ {m_{\mathrm {jj}}} > $ 500 GeV and 2.5 $ < {\Delta \eta _{\mathrm {jj}}} < $ 3.5 category. The last five bins represent the ${m_{\mathrm {jj}}}$ distribution in the $ {m_{\mathrm {jj}}} > $ 500 GeV and $ {\Delta \eta _{\mathrm {jj}}} > $ 3.5 category normalized to the width of the bins. |
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Figure 4:
Post-fit number of events in the control regions for different-flavour (left) and same-flavour (right, with ee and $\mu \mu $ combined) categories. In the left-hand plot, the first bin contains the number of events in the ${\mathrm{t} {}\mathrm{\bar{t}}}$ + $\mathrm{t} \mathrm{W} $ different-flavour control region and the second bin those in the DY $\tau \tau $ control region. In the right-hand plot, the first bin contains the number of events in the ${\mathrm{t} {}\mathrm{\bar{t}}}$ + $\mathrm{t} \mathrm{W} $ same-flavour control region, the second bin those in the $ {\Delta \eta _{\mathrm {jj}}} < $ 5 DY control region, and the third bin those in the $ {\Delta \eta _{\mathrm {jj}}} > $ 5 DY control region. |
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Figure 4-a:
Post-fit number of events in the control regions for different-flavour (left) and same-flavour (right, with ee and $\mu \mu $ combined) categories. In the left-hand plot, the first bin contains the number of events in the ${\mathrm{t} {}\mathrm{\bar{t}}}$ + $\mathrm{t} \mathrm{W} $ different-flavour control region and the second bin those in the DY $\tau \tau $ control region. In the right-hand plot, the first bin contains the number of events in the ${\mathrm{t} {}\mathrm{\bar{t}}}$ + $\mathrm{t} \mathrm{W} $ same-flavour control region, the second bin those in the $ {\Delta \eta _{\mathrm {jj}}} < $ 5 DY control region, and the third bin those in the $ {\Delta \eta _{\mathrm {jj}}} > $ 5 DY control region. |
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Figure 4-b:
Post-fit number of events in the control regions for different-flavour (left) and same-flavour (right, with ee and $\mu \mu $ combined) categories. In the left-hand plot, the first bin contains the number of events in the ${\mathrm{t} {}\mathrm{\bar{t}}}$ + $\mathrm{t} \mathrm{W} $ different-flavour control region and the second bin those in the DY $\tau \tau $ control region. In the right-hand plot, the first bin contains the number of events in the ${\mathrm{t} {}\mathrm{\bar{t}}}$ + $\mathrm{t} \mathrm{W} $ same-flavour control region, the second bin those in the $ {\Delta \eta _{\mathrm {jj}}} < $ 5 DY control region, and the third bin those in the $ {\Delta \eta _{\mathrm {jj}}} > $ 5 DY control region. |
| Tables | |
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Table 1:
Set of variables used as inputs to the DNN for both ${Z_{\ell \ell}} < $ 1 and ${Z_{\ell \ell}} \geq $ 1 models. The order of the table does not correspond to variable importance. |
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Table 2:
Sources of systematic uncertainty affecting the signal yield by more than 1%. The total uncertainty is also reported, as well as the total systematic and statistical contributions. |
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Table 3:
Definition of the fiducial volume close to the reconstructed signal region. |
| Summary |
|
The first observation of the electroweak production of a pair of opposite-sign W bosons in association with two jets is reported. Selected events contain two opposite sign leptons (electrons or muons), missing transverse energy and two jets with high invariant mass and large separation in pseudorapidity. A data set corresponding to an integrated luminosity of 138 fb$^{-1}$ has been analyzed, collected by the CMS detector at the LHC during proton-proton collisions at a center-of-mass energy of 13 TeV. Machine learning techniques have been employed to deal with the irreducible background from the QCD-induced production of W bosons and the dominant background from the production of top quark pairs. The electroweak W$^{+}$W$^{-}$ production cross section has been measured in two fiducial volumes; in the more inclusive one the cross section is 99 $\pm$ 20 fb (89 $\pm$ 5 fb expected), whereas in the one closer to the reconstructed signal region, the measured cross section is 10.2 $\pm$ 2.0 fb (9.1 $\pm$ 0.6 fb expected). The measured signal corresponds to an observed (expected) significance of 5.6 (5.2) standard deviations with respect to the only-background hypothesis. |
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