CMS-PAS-SMP-22-009 | ||
Measurement of the $ Z(\nu\bar{\nu})+\gamma $ production cross section and search for anomalous neutral triple gauge couplings in pp collisions at 13 TeV | ||
CMS Collaboration | ||
12 April 2024 | ||
Abstract: The measurement of the production cross section of a Z boson and a photon in the final state with one photon and large missing transverse momentum, and a search for the presence of neutral anomalous triple gauge couplings are presented. The results are based on data collected by the CMS experiment in proton-proton collisions at $ \sqrt{s}= $ 13 TeV during the 2016, 2017, and 2018 LHC running periods, corresponding to an integrated luminosity of 138 fb$ ^{-1} $. The measured cross section is compatible with the theoretical predictions at the next-to-next-to-leading order in QCD. The study of the photon transverse momentum spectrum yields the most stringent limits on the anomalous triple gauge couplings provided by the CMS experiment to date. | ||
Links: CDS record (PDF) ; CADI line (restricted) ; |
Figures | |
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Figure 1:
The Feynman diagram for the ZV$ \gamma $ vertex, where V$ =\gamma^{*}/\mathrm{Z}^{*} $, in the presence of aNTGC. |
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Figure 2:
The Feynman diagram for the SM Z$\gamma$ production in the t-channel (left), and the additional diagram for the beyond SM s-channel (right) Z$\gamma$ production due to the presence of aNTGCs. |
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Figure 2-a:
The Feynman diagram for the SM Z$\gamma$ production in the t-channel (left), and the additional diagram for the beyond SM s-channel (right) Z$\gamma$ production due to the presence of aNTGCs. |
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Figure 2-b:
The Feynman diagram for the SM Z$\gamma$ production in the t-channel (left), and the additional diagram for the beyond SM s-channel (right) Z$\gamma$ production due to the presence of aNTGCs. |
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Figure 3:
The photon $ p_{\mathrm{T}} $ spectrum for various values of aNTGC couplings and the SM predictions. These samples were produced using MadGraph-5_aMC@NLO [34]. |
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Figure 4:
Measured and predicted differential cross sections as a function of $ p_{\mathrm{T}}^{\gamma} $ for the combined fiducial phase space. |
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Figure 5:
Confidence contours of the aNTGC parameters $ h_3^\gamma, h_4^\gamma $ (left) and $ h_3^Z, h_4^Z $ (right). |
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Figure 5-a:
Confidence contours of the aNTGC parameters $ h_3^\gamma, h_4^\gamma $ (left) and $ h_3^Z, h_4^Z $ (right). |
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Figure 5-b:
Confidence contours of the aNTGC parameters $ h_3^\gamma, h_4^\gamma $ (left) and $ h_3^Z, h_4^Z $ (right). |
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Figure 6:
Comparison of the predicted distribution of $ p_{\mathrm{T}}^{\gamma} $ under the SM-only hypothesis in the barrel (left), and in the endcaps phase space (right) with the predictions at the upper boundaries of the observed 1D confidence intervals of the coupling parameters. The bottom panels compare the SM (shown in red) and the aNTGC predictions, with the observed $ p_{\mathrm{T}}^{\gamma} $ distribution (shown in black). |
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Figure 6-a:
Comparison of the predicted distribution of $ p_{\mathrm{T}}^{\gamma} $ under the SM-only hypothesis in the barrel (left), and in the endcaps phase space (right) with the predictions at the upper boundaries of the observed 1D confidence intervals of the coupling parameters. The bottom panels compare the SM (shown in red) and the aNTGC predictions, with the observed $ p_{\mathrm{T}}^{\gamma} $ distribution (shown in black). |
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Figure 6-b:
Comparison of the predicted distribution of $ p_{\mathrm{T}}^{\gamma} $ under the SM-only hypothesis in the barrel (left), and in the endcaps phase space (right) with the predictions at the upper boundaries of the observed 1D confidence intervals of the coupling parameters. The bottom panels compare the SM (shown in red) and the aNTGC predictions, with the observed $ p_{\mathrm{T}}^{\gamma} $ distribution (shown in black). |
Tables | |
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Table 1:
Systematic uncertainties and their impact on the prediction for the signal. A checkmark indicates full correlation between years. |
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Table 2:
Post-fit event yields in the photon-$ p_{\mathrm{T}} $ spectrum for the combined phase space. |
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Table 3:
Measured and predicted cross sections (in femtobarns) evaluated in the barrel, the endcaps, and the combined fiducial phase spaces. The predicted cross sections are calculated at NLO and NNLO in QCD. |
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Table 4:
Measured and predicted cross sections (in fb) in bins of $ p_{\mathrm{T}}^{\gamma} $. |
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Table 5:
Expected and observed confidence intervals (95% confidence level) of the parameters of anomalous couplings. |
Summary |
We have measured the inclusive and differential cross sections of $ Z(\rightarrow\nu\bar{\nu})+\gamma $ at $ \sqrt{s} = $ 13 TeV in proton-proton collisions using 138 fb$ ^{-1} $ of data collected by the CMS detector. The inclusive cross section of $ Z(\rightarrow\nu\bar{\nu})+\gamma $ is measured to be 26.1 $ ^{+1.6}_{-1.5} $ fb, in agreement with the standard model predictions. The $ p_{\mathrm{T}} $ differential cross section has been measured for the photons and compared with the standard model predictions computed at next-to-leading and next-to-next-to-leading orders in perturbative quantum chromodynamics. With this data we have also placed constraints on the presence of anomalous couplings that affect the ZZ$\gamma $ vertex by using the $ p_{\mathrm{T}} $ spectrum of the photons as the sensitive variable. The observed 95% confidence level intervals for $ h_3^{\gamma} $ and $ h_4^{\gamma} $ are determined to be ($-$3.4, 3.5) $\times$ 10$^{-4} $ and ($-$6.8, 6.8) $\times$ 10$^{-7} $; and for $ h_3^{Z} $ and $ h_4^{Z} $ ($-$2.2, 2.2) $\times$ 10$^{-4} $ and ($-$4.1, 4.2) $ \times$ 10$^{-7} $ respectively. The sensitivities to CP-conserving and CP-violating couplings are comparable in the $ p_{\mathrm{T}} $ regime that we probe. |
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Compact Muon Solenoid LHC, CERN |
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