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| CMS-PAS-SMP-24-014 | ||
| Observation of 4$ \ell\gamma $ and evidence of $ ZZ\gamma $ production in proton-proton collisions at $ \sqrt{s} = $ 13 TeV | ||
| CMS Collaboration | ||
| 2025-05-21 | ||
| Abstract: The first measurement of the production cross section of four charged leptons and a photon in proton-proton collisions is presented. The analysis utilises data collected by the CMS experiment from 2016 to 2018 at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb$ ^{-1} $. The observed (expected) significance for the observation of $ \mathrm{pp} \rightarrow 4\ell \gamma $ in a phase space with $ p_{\mathrm{T}}^\gamma > $ 20 GeV, $ |\eta^\gamma| < $ 2.4 and $ \Delta R(\ell,\gamma) > $ 0.5 is 5.1 (4.1) standard deviations. The measured and expected fiducial cross sections are (0.16 $ \pm $ 0.06) fb and (0.10 $ \pm $ 0.03) fb respectively. The 4$ \ell\gamma $ events, with the additional requirement that the invariant mass of any of the two lepton pairs and the photon is greater than 100 GeV, are also used to search for the production of the triboson process, $ \mathrm{pp} \rightarrow ZZ\gamma $, with fully leptonic decays of the $ Z $ bosons, leading to the first evidence for this process, with an observed (expected) significance of 3.7 (3.0) standard deviations. The measured and expected fiducial cross sections for $ \mathrm{pp} \rightarrow ZZ\gamma \rightarrow 4\ell \gamma $ are (0.06 $ \pm $ 0.03) fb and (0.0 4$ \pm $ 0.02) fb , respectively. Both results are in agreement with the standard model prediction within one standard deviation. | ||
| Links: CDS record (PDF) ; CADI line (restricted) ; | ||
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Compact Muon Solenoid LHC, CERN |
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