Abstract
Two Higgs Doublet Models (2HDM) provide a simple framework for new physics models with an extended Higgs sector. The current LHC results, including both direct searches for additional non-Standard Model (SM) Higgs bosons, as well as precision measurements of the SM-like Higgs couplings, already provide strong constraints on the 2HDM parameter spaces. In this paper, we examine those constraints for the neutral scalars in the Type-I and Type-II 2HDM. In addition to the direct search channels with SM final states: H/A → foverline{f} , VV, Vh, hh, we study in particular the exotic decay channels of H/A → AZ/HZ once there is a mass hierarchy between the non-SM Higgses. We found that H/A → AZ/H Z channel has unique sensitivity to the alignment limit region which remains unconstrained by conventional searches and Higgs precision measurements. This mode also extends the reach at intermediate tβ for heavy mA that are not covered by the other direct searches.
Highlights
H → AA, H+H− or H± → HW/AW open up and quickly dominate the decay branching fractions
In addition to the direct search channels with Standard Model (SM) final states: H/A → f f, V V, V h, hh, we study in particular the exotic decay channels of H/A → AZ/HZ once there is a mass hierarchy between the non-SM Higgses
We found that H/A → AZ/HZ channel has unique sensitivity to the alignment limit region which remains unconstrained by conventional searches and Higgs precision measurements
Summary
LHC Higgs coupling measurements favor the alignment limit, sβ−α ≈ 1, in which the couplings of the 125 GeV Higgs to fermions and gauge bosons are consistent with those predicted by the SM [3, 6,7,8,9]. In the alignment limit, the CP-odd Higgs will couple more strongly to the BSM Higgs H than its SM-like counterpart h This implies that A is more likely to decay to HZ than hZ, if kinematically possible. The corresponding couplings of the neutral scalar states to SM fermions normalized to their SM values, can be expressed in terms of the mixing angles α and β and are shown in table 1. For the remainder of this paper we focus on 2HDMs of Type-I and Type-II, and the main differences of the interpreted results come from the BSM Higgs couplings to fermion pairs
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