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| CMS-PAS-SMP-22-018 | ||
| Measurement of $ \mathrm{WZ}\gamma $ production and constraints on new physics scenarios in proton-proton collisions at $ \sqrt{s}= $ 13 TeV | ||
| CMS Collaboration | ||
| 23 July 2024 | ||
| Abstract: A measurement of the $ \mathrm{WZ}\gamma $ triboson production predicted by the standard model is reported. The analysis uses a data sample of proton-proton collisions at a center-of-mass energy of $ \sqrt{s}= $ 13 TeV recorded with the CMS detector at the LHC, corresponding to an integrated luminosity of 138 fb$ ^{-1} $. The analysis uses the final state containing three charged leptons, $ \mathrm{WZ}\rightarrow\ell\nu\ell'\ell' $, where $ \ell, \ell' = \mathrm{e} $ or $ \mu $, plus an additional photon. The observed (expected) significance of the $ \mathrm{WZ}\gamma $ signal is 5.4 (3.8) standard deviations. The cross section is measured in a fiducial region to be 5.48 $ \pm $ 1.11 fb, which can be compared with the prediction of 3.69 $ \pm $ 0.15 $ \ (\mathrm{PDF}) \pm 0.19\ (\mathrm{scale}) $ fb at next-to-leading order in quantum chromodynamics. Exclusions limits at the 95% confidence level are placed on anomalous quartic gauge couplings and on the production of massive axion-like particles. | ||
| Links: CDS record (PDF) ; CADI line (restricted) ; | ||
| Figures | |
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Figure 1:
Representative Feynman diagrams for $ \mathrm{W}\mathrm{Z}\gamma $ production at LO in QCD, including production through QGCs (left), TGCs (second from left) and multiperipheral (third from left). The right plot shows the $ \mathrm{W}\mathrm{Z}\gamma $ production including an ALP which decays to a Z boson and a photon. |
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Figure 1-a:
Representative Feynman diagrams for $ \mathrm{W}\mathrm{Z}\gamma $ production at LO in QCD, including production through QGCs (left), TGCs (second from left) and multiperipheral (third from left). The right plot shows the $ \mathrm{W}\mathrm{Z}\gamma $ production including an ALP which decays to a Z boson and a photon. |
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Figure 1-b:
Representative Feynman diagrams for $ \mathrm{W}\mathrm{Z}\gamma $ production at LO in QCD, including production through QGCs (left), TGCs (second from left) and multiperipheral (third from left). The right plot shows the $ \mathrm{W}\mathrm{Z}\gamma $ production including an ALP which decays to a Z boson and a photon. |
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Figure 1-c:
Representative Feynman diagrams for $ \mathrm{W}\mathrm{Z}\gamma $ production at LO in QCD, including production through QGCs (left), TGCs (second from left) and multiperipheral (third from left). The right plot shows the $ \mathrm{W}\mathrm{Z}\gamma $ production including an ALP which decays to a Z boson and a photon. |
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Figure 1-d:
Representative Feynman diagrams for $ \mathrm{W}\mathrm{Z}\gamma $ production at LO in QCD, including production through QGCs (left), TGCs (second from left) and multiperipheral (third from left). The right plot shows the $ \mathrm{W}\mathrm{Z}\gamma $ production including an ALP which decays to a Z boson and a photon. |
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Figure 2:
The distributions of the kinematic variables used in the simultaneous fit for the nonprompt $ \ell $ CR (left top), nonprompt $ \gamma $ CR (right top), ZZ CR (left bottom), and SR (right bottom) after the fit to the data. The black points with error bars represent the data and their statistical uncertainties, whereas the shaded band represents the predicted uncertainties. The bottom panel in each figure shows the ratio of the number of events observed in data to that of the total SM prediction. The shaded bands represent the uncertainties in the predicted yields. The vertical bars on the filled circles represent the statistical uncertainties in the data. |
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Figure 2-a:
The distributions of the kinematic variables used in the simultaneous fit for the nonprompt $ \ell $ CR (left top), nonprompt $ \gamma $ CR (right top), ZZ CR (left bottom), and SR (right bottom) after the fit to the data. The black points with error bars represent the data and their statistical uncertainties, whereas the shaded band represents the predicted uncertainties. The bottom panel in each figure shows the ratio of the number of events observed in data to that of the total SM prediction. The shaded bands represent the uncertainties in the predicted yields. The vertical bars on the filled circles represent the statistical uncertainties in the data. |
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Figure 2-b:
The distributions of the kinematic variables used in the simultaneous fit for the nonprompt $ \ell $ CR (left top), nonprompt $ \gamma $ CR (right top), ZZ CR (left bottom), and SR (right bottom) after the fit to the data. The black points with error bars represent the data and their statistical uncertainties, whereas the shaded band represents the predicted uncertainties. The bottom panel in each figure shows the ratio of the number of events observed in data to that of the total SM prediction. The shaded bands represent the uncertainties in the predicted yields. The vertical bars on the filled circles represent the statistical uncertainties in the data. |
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Figure 2-c:
The distributions of the kinematic variables used in the simultaneous fit for the nonprompt $ \ell $ CR (left top), nonprompt $ \gamma $ CR (right top), ZZ CR (left bottom), and SR (right bottom) after the fit to the data. The black points with error bars represent the data and their statistical uncertainties, whereas the shaded band represents the predicted uncertainties. The bottom panel in each figure shows the ratio of the number of events observed in data to that of the total SM prediction. The shaded bands represent the uncertainties in the predicted yields. The vertical bars on the filled circles represent the statistical uncertainties in the data. |
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Figure 2-d:
The distributions of the kinematic variables used in the simultaneous fit for the nonprompt $ \ell $ CR (left top), nonprompt $ \gamma $ CR (right top), ZZ CR (left bottom), and SR (right bottom) after the fit to the data. The black points with error bars represent the data and their statistical uncertainties, whereas the shaded band represents the predicted uncertainties. The bottom panel in each figure shows the ratio of the number of events observed in data to that of the total SM prediction. The shaded bands represent the uncertainties in the predicted yields. The vertical bars on the filled circles represent the statistical uncertainties in the data. |
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Figure 3:
(left) Expected and observed 95% upper limits on the product of the cross section and branching fraction $ \sigma(pp\rightarrow Wa)\mathcal{B}(W\rightarrow \ell^+ \nu_\ell)\mathcal{B}(a\rightarrow \mathrm{Z}\gamma)\mathcal{B}(\mathrm{Z}\rightarrow \ell^+ \ell^-) $ as a function of the ALP mass. The red line corresponds to the theoretical prediction for 1$ /f_a= $ 2 TeV$^{-1} $. (right) Expected and observed 95% upper limits on the photophobic ALP model parameter 1$ /f_a $ as a function of ALP mass reinterpreted from 1$ /f_a= $ 2 TeV$^{-1} $. The blue line indicates the point at which the energy scale of $ f_a $ matches that of the ALP mass. |
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Figure 3-a:
(left) Expected and observed 95% upper limits on the product of the cross section and branching fraction $ \sigma(pp\rightarrow Wa)\mathcal{B}(W\rightarrow \ell^+ \nu_\ell)\mathcal{B}(a\rightarrow \mathrm{Z}\gamma)\mathcal{B}(\mathrm{Z}\rightarrow \ell^+ \ell^-) $ as a function of the ALP mass. The red line corresponds to the theoretical prediction for 1$ /f_a= $ 2 TeV$^{-1} $. (right) Expected and observed 95% upper limits on the photophobic ALP model parameter 1$ /f_a $ as a function of ALP mass reinterpreted from 1$ /f_a= $ 2 TeV$^{-1} $. The blue line indicates the point at which the energy scale of $ f_a $ matches that of the ALP mass. |
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Figure 3-b:
(left) Expected and observed 95% upper limits on the product of the cross section and branching fraction $ \sigma(pp\rightarrow Wa)\mathcal{B}(W\rightarrow \ell^+ \nu_\ell)\mathcal{B}(a\rightarrow \mathrm{Z}\gamma)\mathcal{B}(\mathrm{Z}\rightarrow \ell^+ \ell^-) $ as a function of the ALP mass. The red line corresponds to the theoretical prediction for 1$ /f_a= $ 2 TeV$^{-1} $. (right) Expected and observed 95% upper limits on the photophobic ALP model parameter 1$ /f_a $ as a function of ALP mass reinterpreted from 1$ /f_a= $ 2 TeV$^{-1} $. The blue line indicates the point at which the energy scale of $ f_a $ matches that of the ALP mass. |
| Tables | |
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Table 1:
Summary of the event selections in SR, nonprompt CRs, and the ZZ CR. The nonprompt CRs are used to validate and constrain the nonprompt lepton and photon contributions, and the ZZ CR is used to constrain the ZZ contribution. A ``$ \text{---} $'' indicates that no requirement is placed on the corresponding observable. The aQGC SR is similar to the SR with the exception that $ p_{\mathrm{T}}^{\gamma} > $ 60 GeV. |
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Table 2:
Expected yields after the combined fit for the relevant processes in the signal region and control regions. All analysis uncertainties are included. |
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Table 3:
Summary of the relative contributions of typical uncertainties to the value of the signal strength in the measurement of the SM $ \mathrm{W}\mathrm{Z}\gamma $ signal. |
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Table 4:
Exclusion limits at the 95% CL for each aQGC coefficient, assuming all other coefficients are set to zero. Unitarity bounds corresponding to each operator are also listed. |
| Summary |
| A measurement of the standard model (SM) production of $ \mathrm{W}\mathrm{Z}\gamma $ with both W and Z boson decay leptonically has been presented. Results are based on the data collected in proton-proton collisions at $ \sqrt{s}= $ 13 TeV in the CMS detector during 2016-2018, which corresponding to a integrated luminosity of 138 fb$ ^{-1} $. Events are selected by requiring an identified photon, missing transverse momentum, as well as three identified leptons, of which two correspond to an on-shell Z boson. The observed significance for the SM signal is 5.4 standard deviations, while a significance of 3.8 standard deviations is expected based on the SM prediction. The measured fiducial cross section of leptonic WZ$ \gamma $ production is $ \sigma_{\mathrm{p}\mathrm{p}\rightarrow\ell\nu\ell'\ell'\gamma}= $ 5.48 $ \pm $ 1.11 fb, where $ \ell = \mathrm{e} $ or $ \mu $, is in good agreement with the NLO QCD prediction. Constraints are placed on anomalous quartic gauge couplings in terms of dimension-eight operators in effective field theory. Upper limits on the photophobic axion-like particles (ALPs) are set as a function of ALPs mass. Equivalent limits for the ALPs mass and coupling parameters within the ALPs model are reported, including some of the most stringent constraints for mass points between $ m_a= $ 200 GeV and $ m_a= $ 400 GeV, as well as the first interpretation for masses between $ m_a= $ 110 GeV and $ m_a= $ 200 GeV. |
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