Abstract
The stringent constraints from the direct searches for exotic scalars at the LHC as well as indirect bounds from flavor physics measurements have imposed severe restrictions on the parameter space of new physics models featuring extended Higgs sectors. In the Type-II 2HDM, this implies a lower bound on the charged Higgs masses of $\cal O$(600 GeV). In this work we analyze the phenomenology of a Z3HDM in the alignment limit focusing on the impact of flavor physics constraints on its parameter space. We show that the couplings of the two charged Higgs bosons in this model feature an additional suppression factor compared to Type-II 2HDM. This gives rise to a significant relaxation of the flavor physics constraints in this model, allowing the charged Higgs masses to be as low as $\cal O$(200 GeV). We also consider the constraints coming from precision electroweak observables and the observed diphoton decay rate of the 125 GeV Higgs boson at the LHC. The bounds coming from the direct searches of nonstandard Higgs bosons at the LHC, particularly those from resonance searches in the ditau channel, prove to be very effective in constraining this scenario further.
Highlights
Two of the major tasks that will be undertaken in the upcoming runs of the LHC and beyond comprise of the precise determination of the properties of the 125 GeV Higgs boson as well as direct searches for additional scalar particles
We have analyzed a 3HDM with Z3 symmetry featuring natural flavor conservation (NFC), where the Z3 symmetry ensures a democratic Yukawa structure requiring each type of standard model (SM) fermion to be coupled to a particular Higgs scalar doublet, eliminating flavor changing neutral currents (FCNCs) at tree level
We have discussed the characteristics of the scalar and Yukawa sectors in detail, focusing on the alignment limit where the lightest CP-even Higgs boson of the model possesses SM-like tree-level couplings and can serve as a candidate for the 125 GeV scalar observed at the LHC
Summary
Two of the major tasks that will be undertaken in the upcoming runs of the LHC and beyond comprise of the precise determination of the properties of the 125 GeV Higgs boson as well as direct searches for additional scalar particles. It has been observed that a combination of flavor physics measurements can exclude the charged Higgs masses below Oð600 GeVÞ in the 2HDM of type II [9], where up- and down-type quarks obtain their masses from two different Higgs doublets. This bound on the charged scalar masses can be somewhat relaxed in type-I 2HDMs where a single. We show that the constraints on the parameter space stemming from the interplay of various flavor physics data are notably relaxed compared to those in the type-II 2HDM Such a relaxation of constraints transpires from the presence of an additional suppression in the couplings of the charged Higgs bosons in the model compared to the type-II 2HDM. The detailed analytical expressions for the scalar couplings translation to the physical mass and mixing parameters are given in Appendix A while the Z3HDM contributions to the B-physics flavor observables are presented in Appendix B
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