The 125 GeV Higgs in the context of four generations with 2 Higgs doublets

TL;DR

This paper explores a two Higgs doublet model with a heavy fourth fermion generation, showing it can explain the 125 GeV Higgs and predicts distinctive decay patterns and production rates, with some heavier Higgs states already constrained by data.

Contribution

It introduces a novel two Higgs doublet model with a 4th generation, explaining the 125 GeV Higgs and predicting unique phenomenological signatures.

Findings

The 125 GeV Higgs can be explained with tanβ ~ O(1) and 4th generation fermion masses 400-600 GeV.

The model predicts a large BR(t' -> t h), altering t' decay patterns.

Current data exclude heavier CP-even Higgs up to ~500 GeV, while pseudoscalar A can be as light as 130 GeV.

Abstract

We interpret the recent discovery of a 125 GeV Higgs-like state in the context of a two Higgs doublets model with a heavy 4th sequential generation of fermions, in which one Higgs doublet couples only to the 4th generation fermions, while the second doublet couples to the lighter fermions of the 1st-3rd families. This model is designed to accommodate the apparent heaviness of the 4th generation fermions and to effectively address the low-energy phenomenology of a dynamical electroweak symmetry breaking scenario. The physical Higgs states of the model are, therefore, viewed as composites primarily of the 4th generation fermions. We find that the lightest Higgs, h, is a good candidate for the recently discovered 125 GeV spin-zero particle, when tan\beta ~ O(1), for typical 4th generation fermion masses of M_{4G} = 400 -600 GeV, and with a large t - t' mixing in the right-handed quarks sector. This, in turn, leads to BR(t' -> t h) ~ O(1), which drastically changes the t' decay pattern. We also find that, based on the current Higgs data, this two Higgs doublet model generically predicts an enhanced production rate (compared to the SM) in the pp -> h -> tau tau channel and a reduced VV -> h -> gamma gamma and pp -> V -> Vh -> Vbb ones. Finally, the heavier CP-even Higgs is excluded by the current data up to m_H ~ 500 GeV, while the pseudoscalar state, A, can be as light as 130 GeV. These heavier Higgs states and the expected deviations from the SM in some of the Higgs production channels can be further excluded or discovered with more data.