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| CMS-PAS-SMP-19-008 | ||
| Observation of the electroweak production of W$\gamma$ in association with two jets in proton-proton collisions at $\sqrt{s}= $ 13 TeV | ||
| CMS Collaboration | ||
| May 2020 | ||
| Abstract: A measurement of the electroweak (EW) production of a W boson and a photon in association with two jets in proton-proton collisions, where the W boson decays leptonically, is presented. Events are selected by requiring one identified electron or muon, missing transverse momentum, one photon, and two jets with a large dijet mass and a large rapidity separation. The measurement is based on data collected with the CMS detector in 2016 at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. The observed (expected) significance for this process is 4.9 (4.6) standard deviations. After combining with previously reported CMS results based on 8 TeV data, the observed (expected) significance is 5.3 (4.8) standard deviations. This constitutes the first observation of EW W$\gamma$ production in pp collisions. The cross section measured in the fiducial region is 20.4 $\pm$ 4.5 fb and the total cross section for EW + QCD W$\gamma$ production in association with 2 jets in the same fiducial region is measured to be 108 $\pm$ 16 fb. All measurements are in good agreement with recent theory predictions. We set the most stringent limits to date on the anomalous quartic gauge coupling parameters $F_\mathrm{M,2-5}$ and $F_\mathrm{T,6-7}$. | ||
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These preliminary results are superseded in this paper, PLB 811 (2020) 135988. The superseded preliminary plots can be found here. |
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| Figures | |
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Figure 1:
Representative diagrams for ${\ell \nu \gamma {\text {jj}}}$ production at the LHC: EW production (left), EW production with triple gauge boson coupling (middle left) and with quartic gauge boson coupling (middle right), and QCD-induced processes (right). |
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Figure 1-a:
Representative diagrams for ${\ell \nu \gamma {\text {jj}}}$ production at the LHC: EW production (left), EW production with triple gauge boson coupling (middle left) and with quartic gauge boson coupling (middle right), and QCD-induced processes (right). |
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Figure 1-b:
Representative diagrams for ${\ell \nu \gamma {\text {jj}}}$ production at the LHC: EW production (left), EW production with triple gauge boson coupling (middle left) and with quartic gauge boson coupling (middle right), and QCD-induced processes (right). |
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Figure 1-c:
Representative diagrams for ${\ell \nu \gamma {\text {jj}}}$ production at the LHC: EW production (left), EW production with triple gauge boson coupling (middle left) and with quartic gauge boson coupling (middle right), and QCD-induced processes (right). |
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Figure 1-d:
Representative diagrams for ${\ell \nu \gamma {\text {jj}}}$ production at the LHC: EW production (left), EW production with triple gauge boson coupling (middle left) and with quartic gauge boson coupling (middle right), and QCD-induced processes (right). |
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Figure 2:
Comparison of the photon ${p_{\mathrm {T}}}$ distribution from data and simulation in the low-$ {m_{{\text {jj}}}}$ control region. All events with photon $ {p_{\mathrm {T}}} > $ 193 GeV are included in the last bin. |
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Figure 3:
The 2D distributions used in the fit for the signal strength of EW ${{\mathrm{W} \gamma}}$+2 jets in the electron barrel (top left), electron endcap (top right), muon barrel (bottom left), and muon endcap (bottom right). |
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Figure 3-a:
The 2D distributions used in the fit for the signal strength of EW ${{\mathrm{W} \gamma}}$+2 jets in the electron barrel (top left), electron endcap (top right), muon barrel (bottom left), and muon endcap (bottom right). |
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Figure 3-b:
The 2D distributions used in the fit for the signal strength of EW ${{\mathrm{W} \gamma}}$+2 jets in the electron barrel (top left), electron endcap (top right), muon barrel (bottom left), and muon endcap (bottom right). |
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Figure 3-c:
The 2D distributions used in the fit for the signal strength of EW ${{\mathrm{W} \gamma}}$+2 jets in the electron barrel (top left), electron endcap (top right), muon barrel (bottom left), and muon endcap (bottom right). |
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Figure 3-d:
The 2D distributions used in the fit for the signal strength of EW ${{\mathrm{W} \gamma}}$+2 jets in the electron barrel (top left), electron endcap (top right), muon barrel (bottom left), and muon endcap (bottom right). |
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Figure 4:
The 2D distributions used in the fit for the signal strength of EW+QCD ${{\mathrm{W} \gamma}}$+2 jets in the electron barrel (top left), electron endcap (top right), muon barrel (bottom left) and muon endcap (bottom right). |
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Figure 4-a:
The 2D distributions used in the fit for the signal strength of EW+QCD ${{\mathrm{W} \gamma}}$+2 jets in the electron barrel (top left), electron endcap (top right), muon barrel (bottom left) and muon endcap (bottom right). |
png pdf |
Figure 4-b:
The 2D distributions used in the fit for the signal strength of EW+QCD ${{\mathrm{W} \gamma}}$+2 jets in the electron barrel (top left), electron endcap (top right), muon barrel (bottom left) and muon endcap (bottom right). |
png pdf |
Figure 4-c:
The 2D distributions used in the fit for the signal strength of EW+QCD ${{\mathrm{W} \gamma}}$+2 jets in the electron barrel (top left), electron endcap (top right), muon barrel (bottom left) and muon endcap (bottom right). |
png pdf |
Figure 4-d:
The 2D distributions used in the fit for the signal strength of EW+QCD ${{\mathrm{W} \gamma}}$+2 jets in the electron barrel (top left), electron endcap (top right), muon barrel (bottom left) and muon endcap (bottom right). |
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Figure 5:
The ${m_{{\mathrm{W} \gamma}}}$ distribution of events satisfying the aQGC region selection, which is used to set constraints on the anomalous coupling parameters. The orange line represents a nonzero ${F_{\text {T,0}}}$ setting. All events with $ {m_{{\mathrm{W} \gamma}}} > $ 990 GeV are included in the last bin. |
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Figure 6:
Observed 95% CL interval on the aQGC parameter ${F_{\text {T,0}}}$. |
| Tables | |
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Table 1:
Relative systematic uncertainties in the estimated signal and background yields in units of percent. The range of the uncertainty when varying ${m_{{\text {jj}}}}$ and ${m_{{\ell \gamma}}}$ is shown for the systematic uncertainty sources. |
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Table 2:
Signal, background, and data yields after the final selection for the SM measurement. The pre-fit statistical and systematic uncertainties are added in quadrature. |
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Table 3:
Parameterized by the W$\gamma$ mass, 95% CL shape-based exclusion limits on each aQGC parameter, no form factor is applied. The unitarity bounds are also listed. All coupling parameter limits are in TeV$ ^{-4}$, while the unitarity bounds are in TeV. |
| Summary |
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The production cross sections of electroweak production of W$\gamma$ in association with two jets are measured in proton-proton collisions at a center-of-mass energy of 13 TeV. The data sample corresponds to an integrated luminosity of 35.9 fb$^{-1}$ collected at $\sqrt{s} = $ 13 TeV with the CMS detector. Events are selected by requiring exactly one identified lepton (electron or muon), a moderate missing transverse momentum, one photon, and two jets with a large rapidity separation and a large dijet mass. The observed significance is 4.9 standard deviations ($\sigma$), where a significance of 4.6 $\sigma$ is expected based on the standard model. After combining with previously reported CMS results based on 8 TeV data, the observed (expected) signal significance is 5.3 (4.8) $\sigma$. This constitutes the first observation of electroweak W$\gamma$ production in pp collisions. A cross section measurement in a fiducial region is reported and is consistent with standard model predictions. Constraints are placed on anomalous quartic gauge couplings in terms of dimension-8 effective field theory operators. Results are competitive with or more stringent than previous results. |
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