Axion-Higgs interplay in the two-Higgs-doublet model

Abstract

The Zhitnitsky and Dine, Fischler and Srednicki (DFSZ) model is a natural extension of the two-Higgsdoublet model containing an additional singlet, endowed with a Peccei-Quinn symmetry, and leading to a physically acceptable axion. In this paper we reexamine this model in the light of some new developments. For generic couplings the model reproduces the minimal Standard Model showing only tiny deviations (extreme decoupling scenario) and all additional degrees of freedom (with the exception of the axion) are very heavy. Recently it has been remarked that the limit where the coupling between the singlet and the two doublets becomes very small is technically natural. Combining this limit with the requirement of exact or approximate custodial symmetry, we may obtain an additional 0 þ Higgs at the weak scale, accompanied by relatively light charged and neutral pseudoscalars. The mass spectrum would then resemble that of a generic two-Higgs-doublet model, with naturally adjustable masses in spite of the large scale that the axion introduces. However, the couplings are nongeneric in this model. We use the recent constraints derived from the Higgs-WW coupling together with oblique corrections to constrain the model as much as possible.As an additional result, we work out the nonlinear parametrization of the DFSZ model in the generic case where all scalars except the lightest Higgs and the axion have masses at or beyond the TeV scale.

Leptogenesis from oscillations and dark matter

“…leading naturally to type II two-Higgs-doublet models without FCNC [88,89]. The most general scalar potential of the model compatible with a global U (1) P Q is the following…”

Neutrino-axion-dilaton interconnection

“…In this section we shall discuss the conditions under which the scalar spectrum is phenomenologically viable and the vacuum structure of the model is stable. A necessary prerequisite to that is the analysis of the constraints on the scalar couplings coming from the measured value of the Higgs mass (125.09 ± 0.21 ± 0.11 GeV [37]) and the allowed deviations of its couplings to matter and gauge fields (for a recent study of the Higgs LHC physics and the electroweak precision observables in the DFSZ ultraweak setup see [38]). We shall give a benchmark setting of the model parameters that satisfies all the present LHC constraints with the heavier scalars possibly below the TeV scale, and thus accessible to the collider searches.…”

Oblique corrections in the Dine-Fischler-Srednicki axion model

“…The rotation matrix can be different form the identity. However, experimentally the parameter cos θ, appearing on the diagonal of the rotation matrix, is known [6] to be very close to one. We present a range of masses allowed by the constraints on ΔT in Fig.…”

“…The mass matrix can be diagonalized in the limit of large v φ , which is astrophysically constrained to be at least of order 10 7 GeV. In the paper [6] an expansion in v/v φ is carried out to the second order to get the masses of h i . It is argued that the nominal expansion in powers of v/v φ is applicable in a number of cases.…”

“…Having defined the fields we proceed with the description of the mass spectrum of the model (following [6]). We have two doublets and a singlet, so a total of 4 + 4 + 2 = 10 spin-zero particles.…”