Limiting two-Higgs-doublet models

Abstract

Abstract:We update the constraints on two-Higgs-doublet models (2HDMs) focusing on the parameter space relevant to explain the present muon g − 2 anomaly, ∆a µ , in four different types of models, type I, II, "lepton specific" (or X) and "flipped" (or Y). We show that the strong constraints provided by the electroweak precision data on the mass of the pseudoscalar Higgs, whose contribution may account for ∆a µ , are evaded in regions where the charged scalar is degenerate with the heavy neutral one and the mixing angles α and β satisfy the Standard Model limit β − α ≈ π/2. We combine theoretical constraints from vacuum stability and perturbativity with direct and indirect bounds arising from collider and B physics. Possible future constraints from the electron g − 2 are also considered. If the 126 GeV resonance discovered at the LHC is interpreted as the light CP-even Higgs boson of the 2HDM, we find that only models of type X can satisfy all the considered theoretical and experimental constraints.

Minimal muon anomalous magnetic moment

“…In ref. [33] they consider four two-Higgs-doublet models and conclude that in one of them ∆a µ can be obtained, thanks to the enhanced two-loops contribution of the pseudoscalar Higgs. In order for this to be realized, all the scalars must be lighter than ∼ 200 GeV, and therefore this option is testable at the LHC.…”

Study of lepton flavor violation in flavor symmetric models for lepton sector

“…As pointed out in ref. [71,72], the discrepancy of muon anomalous magnetic moment may be explained if tan β is quite large and pseudo scalar is rather small. Let us also survey the parameter region in the next section.…”

“…This type of scalars with the interactions in eq. (2.20) have been well investigated so far, motivated by, for instance, the deviation of muon anomalous magnetic moment [71,72]. The lower bound on the charged Higgs mass comes from the direct search for charged Higgs at the LHC and it is given by top mass to evade the exotic top decay: m H ± 172 GeV [73,74].…”

“…This is quite strong, compared to the bound from e + e − → τ + τ − in figure 1. We may require large tan β, for instance, to enhance the muon anomalous magnetic moment [71,72], but the ratio of the squared mass difference to m 2 φ 2 , (δm 2 H ) 22 /m 2 φ 2 , should be much smaller than O(10 −2 ).…”

“…In ref. [71,72], very light pseudo-scalar is introduced to achieve the anomaly in the leptophilic 2HDM. In our model, we could find new contributions to (g − 2) µ according to the tree-level FCNCs [76],…”