CMS-PAS-SMP-22-006

CMS-PAS-SMP-22-006
Observation of WW$ \gamma $ production and constraints on Higgs couplings to light quarks in proton-proton collisions at $ \sqrt{s}= $ 13 TeV
CMS Collaboration
23 March 2023

Abstract: The first observation of WW$ \gamma $ production with leptonic final states in proton-proton collisions at a center-of-mass energy of 13 TeV is presented. A data set corresponding to an integrated luminosity of 138 fb$ ^{-1} $ collected by the CMS experiment at the LHC in 2016-2018 is used. Events are selected by requiring exactly two leptons (one electron and one muon) of opposite charge, moderate missing transverse momentum, and a photon. The measured fiducial cross section for WW$ \gamma $ is $ \sigma = $ 6.0 $ \pm $ 1.7 fb, in good agreement with the next-to-leading order QCD prediction. The analysis is also extended to search for the associated production of a Higgs boson and a photon where the Higgs boson decays to W$ ^{+} $W$ ^{-} $, which is sensitive to the Higgs coupling to light quarks (the c, s, u, and d quarks), and limits on these couplings are reported at 95% confidence level.
Links: CDS record (PDF) ; Physics Briefing ; CADI line (restricted) ; These preliminary results are superseded in this paper, Accepted by PRL. The superseded preliminary plots can be found here.

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Representative Feynman diagrams for the WW$ \gamma $ process. From left to right, ISR, FSR, QGC, and Higgs associated production.
png pdf	Figure 1-a: Representative Feynman diagrams for the WW$ \gamma $ process. From left to right, ISR, FSR, QGC, and Higgs associated production.
png pdf	Figure 1-b: Representative Feynman diagrams for the WW$ \gamma $ process. From left to right, ISR, FSR, QGC, and Higgs associated production.
png pdf	Figure 1-c: Representative Feynman diagrams for the WW$ \gamma $ process. From left to right, ISR, FSR, QGC, and Higgs associated production.
png pdf	Figure 1-d: Representative Feynman diagrams for the WW$ \gamma $ process. From left to right, ISR, FSR, QGC, and Higgs associated production.
png pdf	Figure 2: The distributions of the invariant mass of the WW$ \gamma $ system (left) and the transverse mass of the WW system (right) after the signal region selection before the fit to data. The shaded band represents the statistical uncertainty.
png pdf	Figure 2-a: The distributions of the invariant mass of the WW$ \gamma $ system (left) and the transverse mass of the WW system (right) after the signal region selection before the fit to data. The shaded band represents the statistical uncertainty.
png pdf	Figure 2-b: The distributions of the invariant mass of the WW$ \gamma $ system (left) and the transverse mass of the WW system (right) after the signal region selection before the fit to data. The shaded band represents the statistical uncertainty.
png pdf	Figure 3: The 2D $ m_{\mathrm{T}}^{\mathrm{WW}}-m_{\ell\ell\gamma} $ distributions are used for the significance measurement with category 0 jet (left) and $ \geq $ 1 jet (right) after the fit to data. The data are compared to the signal and background in the predictions. The black points with error bars represent the data and their statistical+systematic uncertainties, whereas the hatched bands represent the total uncertainties of the predictions.
png pdf	Figure 3-a: The 2D $ m_{\mathrm{T}}^{\mathrm{WW}}-m_{\ell\ell\gamma} $ distributions are used for the significance measurement with category 0 jet (left) and $ \geq $ 1 jet (right) after the fit to data. The data are compared to the signal and background in the predictions. The black points with error bars represent the data and their statistical+systematic uncertainties, whereas the hatched bands represent the total uncertainties of the predictions.
png pdf	Figure 3-b: The 2D $ m_{\mathrm{T}}^{\mathrm{WW}}-m_{\ell\ell\gamma} $ distributions are used for the significance measurement with category 0 jet (left) and $ \geq $ 1 jet (right) after the fit to data. The data are compared to the signal and background in the predictions. The black points with error bars represent the data and their statistical+systematic uncertainties, whereas the hatched bands represent the total uncertainties of the predictions.

Tables
png pdf	Table 1: The number of events in data and predictions after the fit to data in the Top$ \gamma $ CR, SSWW$ \gamma $ CR, and signal region.
png pdf	Table 2: Upper limits on the cross section and reinterpreted Yukawa coupling limits for H$ \gamma $ production initiated by light quarks.

Summary

In summary, this note reports the first observation of WW$ \gamma $ production in proton-proton collisions at a center-of-mass energy of 13 TeV with an integrated luminosity of 138 fb$ ^{-1} $, collected by the CMS experiment at the LHC in 2016--2018. The measured fiducial cross section for WW$ \gamma $ is 6.0 $ \pm $ 1.7 fb, in good agreement with the next-to-leading order QCD prediction. A search for the associated production of a Higgs boson and a photon was also performed using the Higgs boson decay to W$ ^{+} $W$ ^{-} $. A set of 95% confidence level limits on the Higgs couplings with light quarks were reported, including some of the most stringent to date.

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