Search for light pseudoscalar boson pairs produced from decays of the 125 GeV Higgs boson in final states with two muons and two nearby tracks in pp collisions at $\sqrt{s}=$ 13 TeV
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Abstract (data abstract)
CERN-LHC. The analysis searches for pairs of light pseudoscalar bosons, in the mass range from 4 to 15 GeV, produced from decays of the 125 GeV Higgs boson. The decay modes considered are final states that arise when one of the pseudoscalars decays to a pair of tau leptons, and the other one either into a pair of tau leptons or muons. The analysis employs a special analysis strategy to select and identify highly Lorentz-boosted muon or tau lepton pairs with overlapping decay products. This signature is sensitive to specific 2HD+1S models in which the lightest pseudoscalar boson (a) has a large singlet component, and therefore its couplings to SM particles are significantly reduced. The search is based on proton-proton collisions collected by the CMS experiment in 2016 at a center-of-mass energy of 13 TeV that correspond to an integrated luminosity of 35.9 fb-1. No significant excess is observed beyond the expectation from the SM. The table gives upper limits on the cross section times branching fraction for light pseudoscalars with masses between 4 and 15 GeV.