Search for exotic decays of the Higgs boson to a pair of pseudoscalars in the μ μ b b and τ τ b b final states

A search for exotic decays of the Higgs boson ( ) with a mass of 125 to a pair of light pseudoscalars is performed in final states where one pseudoscalar decays to two quarks and the other to a pair of muons or leptons. A data sample of proton-proton collisions at corresponding to an integrated luminosity of 138 recorded with the CMS detector is analyzed. No statistically significant excess is observed over the standard model backgrounds. Upper limits are set at 95% confidence level ( ) on the Higgs boson branching fraction to and to via a pair of s. The limits depend on the pseudoscalar mass and are observed to be in the range (0.17-3.3) and (1.7-7.7) in the and final states, respectively. In the framework of models with two Higgs doublets and a complex scalar singlet (2HDM+S), the results of the two final states are combined to determine upper limits on the branching fraction at 95% , with being a muon or a lepton. For different types of 2HDM+S, upper bounds on the branching fraction are extracted from the combination of the two channels. In most of the Type II 2HDM+S parameter space, values above 0.23 are excluded at 95% for values between 15 and 60 .