Search for light pseudoscalar Higgs bosons with boosted di-mu di-tau topologies

A search is performed for a light pseudoscalar Higgs boson (a) motivated by the theoretical framework of two Higgs doublet plus singlet models (2HDM+S). This search uses Run II LHC data collected at 13 TeV by the CMS experiment and analyzes the decay channel H->a a->mu mu tau tau, with H being either the 125 GeV state or a more massive Higgs boson. Final state taus have a boosted and collimated topology due to the large mass difference between the H and a. Thus, a novel algorithm for this non-standard final state is designed to increase the identification efficiency, and a dedicated machine learning technique is used for the case of overlapping hadronic tau decays. Limits are derived in the context of four types of 2HDM+S models.