Search for a Dark Photon and an Invisible Dark Higgs Boson in μ+μ− and Missing Energy Final States with the Belle II Experiment
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The decay has been observed with a statistical significance in excess of five standard deviations. The analysis is based on an event sample of proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the CMS experiment in 2018 and corresponding to an integrated luminosity of . Normalizing to the decay mode leads to a branching fraction of , a value that is consistent with the standard model prediction. © 2024 CERN, for the CMS Collaboration2024CERNmore » « less
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We report on a search for a resonance decaying to a pair of muons in events in the mass range, using of data collected by the Belle II experiment at the SuperKEKB collider at a center of mass energy of 10.58 GeV. The analysis probes two different models of beyond the standard model: a vector boson in the model and a muonphilic scalar. We observe no evidence for a signal and set exclusion limits at the 90% confidence level on the products of cross section and branching fraction for these processes, ranging from 0.046 fb to 0.97 fb for the model and from 0.055 fb to 1.3 fb for the muonphilic scalar model. For masses below , the corresponding constraints on the couplings of these processes to the standard model range from 0.0008 to 0.039 for the model and from 0.0018 to 0.040 for the muonphilic scalar model. These are the first constraints on the muonphilic scalar from a dedicated search. Published by the American Physical Society2024more » « less