We investigate the feasibility of electroweak baryogenesis in a two-Higgs doublet model with lepton flavor violation. By scrutinizing the heavy Higgs boson mass spectrum, regions satisfying both ...strong first-order electroweak phase transition and the muon g−2 anomaly are identified. We also estimate the baryon number density by exploiting extra Yukawa couplings in the μ-τ sector. It is found that a CP-violating source term can be enhanced by the μ-τ flavor-violating coupling together with the extra τ coupling. With O(1) Yukawa couplings and CP-violating phases, the observed baryon number density is marginally produced under a generous assumption for the bubble wall profile.
We study the feasibility of strong first-order electroweak phase transition (EWPT) in a degenerate-scalar scenario of a complex singlet extension of the Standard Model, in which a mass of an ...additional scalar is nearly degenerate with that of the Higgs boson, 125 GeV. This scenario is known to provide an exquisite solution for circumventing constraints from dark matter direct detection experiments due to cancellations between two scattering amplitudes mediated by two scalars. In the analysis of EWPT, we employ two gauge-invariant calculation schemes on the scalar potential and two familiar resummation methods in evaluating one-loop (gauge dependent) effective potential. We point out that one of the conditions for the strong first-order EWPT is incompatible with the known suppression mechanism of a dark matter cross-section scattering off the nucleons. Nevertheless, we find that strong first-order EWPT is still possible in the degenerate-scalar scenario by dodging dark matter constraints differently.
We revisit the electroweak phase transition in the standard model with a real scalar, utilizing several calculation methods to investigate scheme dependences. We quantify the numerical impacts of ...Nambu–Goldstone resummation, required in one of the schemes, on the strength of the first-order electroweak phase transition. We also employ a gauge-independent scheme to make a comparison with the standard gauge-dependent results. It is found that the effect of the Nambu–Goldstone resummation is typically ∼1%. Our analysis shows that both gauge-dependent and -independent methods give qualitatively the same result within theoretical uncertainties. In either methods, the scale uncertainties in the ratio of critical temperature and the corresponding Higgs vacuum expectation value are more than 10%, which signifies the importance of higher-order corrections.
We study general aspects of the CP-violating effects on the baryon asymmetry of the Universe (BAU) and electric dipole moments (EDMs) in models extended by an extra Higgs doublet and a singlet, ...together with electroweak-interacting fermions. In particular, the emphasis is on the structure of the CP-violating interactions and dependences of the BAU and EDMs on masses of the relevant particles. In a concrete mode, we investigate a relationship between the BAU and the electron EDM for a typical parameter set. As long as the BAU-related CP violation predominantly exists, the electron EDM has a strong power in probing electroweak baryogenesis. However, once a BAU-unrelated CP violation comes into play, the direct correlation between the BAU and electron EDM can be lost. Even in such a case, we point out that verifiability of the scenario still remains with the help of Higgs physics.
A
bstract
We consider the issue of vacuum stability and triviality bound of the singlet extension of the Standard Model (SM) with a singlet fermion dark matter (DM). In this model, the singlet scalar ...plays the role of a messenger between the SM sector and the dark matter sector. This model has two Higgs-like scalar bosons, and is consistent with all the data on electroweak precision tests, thermal relic density of DM and its direct detection constraints. We show that this model is stable without hitting Landau pole up to Planck scale for 125 GeV Higgs boson. We also perform a comprehensive study of vacuum structure, and point out that a region where electroweak vacuum is the global minimum is highly limited. In this model, both Higgs-like scalar bosons have reduced couplings to the SM weak gauge bosons and the SM fermions, because of the mixing between the SM Higgs boson and the singlet scalar. There is also a possibility of their invisible decay(s) into a pair of DM’s. Therefore this model would be disfavored if the future data on the (
σ B
)
VV
or
with
V
= γ
, W, Z
and
f
=
b,
τ turn out larger than the SM predictions.
We study phenomenology of electroweak-interacting fermionic dark matter (DM) with a mass of O(100) GeV. Constructing the effective Lagrangian that describes the interactions between the Higgs boson ...and the SU(2)L isospin multiplet fermion, we evaluate the electric dipole moment (EDM) of electron, the signal strength of Higgs boson decay to two photons and the spin-independent elastic-scattering cross section with proton. As representative cases, we consider the SU(2)L triplet fermions with zero/nonzero hypercharges and SU(2)L doublet fermion. It is found that the electron EDM gives stringent constraints on those model parameter spaces. In the cases of the triplet fermion with zero hypercharge and the doublet fermion, the Higgs signal strength does not deviate from the standard model prediction by more than a few % once the current DM direct detection constraint is taken into account, even if the CP violation is suppressed. On the contrary, O(10–20)% deviation may occur in the case of the triplet fermion with nonzero hypercharge. Our representative scenarios may be tested by the future experiments.
A phenomenological consequence of electroweak baryogenesis is studied in connection with the Higgs physics. In a two Higgs doublet model, the first-order phase transition can be strong enough to ...allow the electroweak baryogenesis due to the effect of extra Higgs bosons. We investigate the quantum correction to the triple coupling of the lightest Higgs boson in such a scenario, and find that the condition of the strong first-order phase transition necessarily leads to the deviation of at least 10% from the Standard Model prediction. Such magnitude of the deviation can be identified in future e+e− linear collider experiments. We also discuss the minimal supersymmetric standard model with the light stop scenario, and point out that a sizable correction appears in the triple coupling for successful electroweak baryogenesis.
We investigate an electroweak interacting dark matter (DM) model in which the DM is the neutral component of the SU(2)L triplet fermion that couples to the standard model (SM) Higgs sector via an SM ...singlet Higgs boson. In this setup, the DM can have a CP-violating coupling to the singlet Higgs boson at the renormalizable level. As long as the nonzero Higgs portal coupling (singlet-doublet Higgs boson mixing) exists, we can probe CP violation of the DM via the electric dipole moment of the electron. Assuming the O(1) CP-violating phase in magnitude, we investigate the relationship between the electron EDM and the singlet-like Higgs boson mass and coupling. It is found that for moderate values of the Higgs portal couplings, current experimental EDM bound is not able to exclude the wide parameter space due to a cancellation mechanism at work. We also study the spin-independent cross section of the DM in this model. It is found that although a similar cancellation mechanism may diminish the leading-order correction, as often occurs in the ordinary Higgs portal DM scenarios, the residual higher-order effects leave an O(10−47) cm2 correction in the cancellation region. It is shown that our benchmark scenarios would be fully tested by combining all future experiments of the electron EDM, DM direct detection and Higgs physics.
A
bstract
We discuss a strongly-coupled extended Higgs sector with the 126 GeV Higgs boson, which is a low-energy effective theory of the supersymmetric SU(2)
H
gauge thoery that causes confinement. ...In this effective theory, we study the parameter region where electroweak phase transition is of strongly first order, as required for successful electroweak baryogenesis. In such a parameter region, the model has a Landau pole at the order of 10 TeV, which corresponds to the confinement scale of the SU(2)
H
gauge theory. We find that the large coupling constant which blows up at the Landau pole results in large non-decoupling loop effects on low-energy observables, such as the Higgs-photon-photon vertex and the triple Higgs boson vertex. As phenomenological consequences of electroweak baryogenesis in our model, the Higgs-to-diphoton branching ratio is about 20% smaller while the triple Higgs boson coupling is more than about 20% larger than the standard model predictions. Such deviations may be detectable in future collider experiments.
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