Search for a Pseudoscalar Higgs Boson in the Context of Two-Higgs-Doublet Models

A search for a pseudoscalar Higgs boson A is performed, focusing on its decay into a standard model-like Higgs boson h and a Z boson. Decays of the h boson into a pair of tau leptons are considered along with Z boson decays into a pair of light leptons (electrons or muons). A data sample of proton-proton collisions collected by the CMS experiment at the LHC at √s= 13TeV is used, corresponding to an integrated luminosity of 35.9fb$^{−1}$. The search uses the reconstructed mass distribution of the A boson as the discriminating variable. This analysis is the first of its kind to utilise the SVFIT algorithm while exploiting the possibility to apply a mass constraint of 125 GeV in the h→ ττ four-vector reconstruction. The resolution of the reconstructed mass of the A boson is improved compared to the mass resolution obtained inprevious analyses targeting the same final state. No excess above the standard model expectation is observed in data. Model-independent as well as model-dependent upper limits in the m$_{A}$–tan β plane for two minimal supersymmetric standard model benchmark scenarios are set at 95% confidence level. The model-independent upper limit on the product of the gluon fusion production cross section and the branching fraction for the A→Zh→llττ decay ranges from 27 fb at 220 GeV to 5 fb at 400 GeV. The observed model-dependent limits on the process σ(gg→A+bbA)β(A→Zh→llττ) in case of the hMSSM (low-tb-high) scenario exclude tan β values from 1.6 (1.8) at m$_{A}$= 220 GeV to 3.7 (3.8) at m$_{A}$ = 300 GeV, respectively.