Is the LHC observing the pseudoscalar state of a two-Higgs-doublet model?

Abstract

The ATLAS and CMS collaborations have recently shown data suggesting the presence of a Higgs boson in the vicinity of 125 GeV. We show that a two-Higgs doublet model spectrum, with the pseudo-scalar state being the lightest, could be responsible for the diphoton signal events. In this model, the other scalars are considerably heavier and are not excluded by the current LHC data. If this assumption is correct, future LHC data should show a strengthening of the γγ signal, while the signals in the ZZ ( * ) → 4 and W W ( * ) → 2 2ν channels should diminish and eventually disappear, due to the absence of diboson tree-level couplings of the CP-odd state. The heavier CP-even neutral scalars can now decay into channels involving the CP-odd light scalar which, together with their larger masses, allow them to avoid the existing bounds on Higgs searches. We suggest additional signals to confirm this scenario at the LHC, in the decay channels of the heavier scalars into AA and AZ. Finally, this inverted two-Higgs doublet spectrum is characteristic in models where fermion condensation leads to electroweak symmetry breaking. We show that in these theories it is possible to obtain the observed diphoton signal at or somewhat above of the prediction for the standard model Higgs for the typical values of the parameters predicted.

Probing the charged Higgs boson at the LHC in the CP-violating type-II 2HDM

“…The crucial LHC constraint is the quantity R γγ . Others [25,26] have argued for an interpretation of the 125 GeV excess in terms of a pseudoscalar, but we are not able to confirm this. We find points which satisfy all other constraints, but not the LHC constraints.…”

“…We will show that very little CP-conserving parameter space survives these data. This exploration of the allowed parameter space has been addressed recently by several authors, from different points of view [24][25][26][27][28]. Where there is overlap, we compare our results with those obtained by these authors.…”

Two-Higgs-doublet model in light of the standard modelH→τ+τ−search at the LHC

“…Taking into account that tan β is already constrained to be above 1, the present results are close to exclude all values of tan β if the pseudo-scalar is in the mass range considered. The study recently performed in [57] concludes that if the excess observed at the LHC comes from A → γγ, tan β ≈ O(1), which is still allowed within experimental and theoretical errors in all four models. …”

Left-right twin Higgs model confronted with the latest LHC Higgs data

“…The LHC diphoton signal has been studied in various new physics models, such as some popular supersymmetry models [13], the two Higgs doublet model [14], the Higgs triplet model [15], the models with extra-dimensions [16], the little Higgs models [17], and the other extensions of Higgs models [18,19]. In the LRTH model, the diphoton decay of the SM-like Higgs boson was studied even before the LHC Higgs data [20].…”