Search for exotic decays of the Higgs boson to a pair of pseudoscalars in the μμbb and ττbb final states.

A search for exotic decays of the Higgs boson (H ) with a mass of 125 Ge V to a pair of light pseudoscalars a 1 is performed in final states where one pseudoscalar decays to two b quarks and the other to a pair of muons or τ leptons. A data sample of proton–proton collisions at s = 13 Te V corresponding to an integrated luminosity of 138 fb - 1 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 (CL ) on the Higgs boson branching fraction to μ μ b b and to τ τ b b , via a pair of a 1 s. The limits depend on the pseudoscalar mass m a 1 and are observed to be in the range (0.17–3.3) × 10 - 4 and (1.7–7.7) × 10 - 2 in the μ μ b b and τ τ b b 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 B (H → a 1 a 1 → ℓ ℓ b b) at 95% CL , with ℓ being a muon or a τ lepton. For different types of 2HDM+S, upper bounds on the branching fraction B (H → a 1 a 1) are extracted from the combination of the two channels. In most of the Type II 2HDM+S parameter space, B (H → a 1 a 1) values above 0.23 are excluded at 95% CL for m a 1 values between 15 and 60 Ge V . [ABSTRACT FROM AUTHOR]