We discuss whether a multi-step electroweak phase transition (EWPT) occurs in two Higgs doublet models (2HDMs). The EWPT is related to interesting phenomena such as baryogenesis and a gravitational wave from it. We examine parameter regions in CP-conserving 2HDMs and find certain areas where the multi-step EWPTs occur. The parameter search shows the multi-step EWPT prefers the scalar potential with the approximate $Z_2$ symmetry and a mass hierarchy between the neutral CP-odd and CP-even extra scalar bosons $m_A<m_H$. By contrast, the multi-step EWPT whose first step is strongly first order favors a mass hierarchy $m_A>m_H$. In addition, we compute the Higgs trilinear coupling in the parameter region where the multi-step EWPTs occur, which can be observed at future colliders. We also discuss a multi-peaked gravitational wave from a multi-step EWPT.
We use transport equations to compute the evolution of the quark plasma at the electroweak phase transition in the two-doublet Higgs model, obtaining in a more rigorous and quantitatively accurate way results consistent with previous work. We discuss the model in connection with the electroweak baryogenesis scenario, and claim that the observed baryon asymmetry of the universe can be obtained within this model with a suitable choice of parameters.
The electroweak symmetry is nonlinearly realized in an extension of the minimal supersymmetric standard model (MSSM) through an additional pair of constrained Higgs doublet superfields. The superpotential couplings of this constrained Higgs doublet pair to the MSSM Higgs doublet pair catalyze their vacuum expectation values. The Higgs and Higgsino-gaugino mass spectrum is presented for several choices of supersymmetry (SUSY) breaking and Higgs superpotential mass parameters. The additional vacuum expectation values provided by the constrained fields can produce a phenomenology quite different …
The manner in which the parameters of a two-Higgs-doublet model can be chosen so that no Higgs boson is discovered at a $\sqrt{s}\leq 800\gev$ $\epem$ collider, while maintaining consistency with current precision electroweak measurements, is described. The importance of a Giga-$Z$ factory and higher collider energies for such a scenario is emphasized.
We calculate both the cubic and the quartic self-couplings of the lighter scalar Higgs boson without assuming the decoupling limit in the two-Higgs-doublet model (THDM). In some regions of parameter space of the THDM where the electroweak phase transition is strongly first order, it is possible that the quartic self-coupling of the lighter scalar Higgs boson might be deviated by at least 40 % from the standard model prediction.
The minimal supersymmetric standard model (MSSM) is extended by including an additional pair of constrained Higgs doublet superfields through which the electroweak symmetry is nonlinearly realized. The superpotential couplings of this constrained Higgs doublet pair to the MSSM Higgs doublet pair catalyze the later nontrivial vacuum expectation values. The mass spectrum of the Higgs scalars and Higgsino-gaugino sector is presented for several choices of supersymmetry (SUSY) breaking and Higgs superpotential mass parameters. The effect of the the additional constrained fields and multiple vacuum…
The electroweak radiative correction, which turned out to be marginal within the standard electroweak model having the minimal Higgs sector in view of the present experimental information, fits well the experiment when the Higgs sector is extended to have two Higgs doublets. We predict the range where the charged and CP odd Higgs boson masses would lie, taking the two CP even neutral Higgs boson masses to be degenerate which makes the analysis in multiparameter space feasible. It is shown that the mass of neutral Higgs doublet boson can arbitrarily be large consistently with the $W$ mass, if t…
We study the stability of neutral electroweak vacua in two Higgs doublet models, and calculate the lifetime of these states when the parameters are such that they are false vacua. As the two Higgs doublet model is invariant under a sign change of both doublets, degenerate true vacua exist. It is shown that this degeneracy, despite the fact that each of these minima locally describes the same physics, can immensely affect their lifetime. We apply these calculations to the parameter space of the models which is allowed by recent LHC searches, and infer combinations of parameters which should be …
We use the left-right symmetry model based on SU(2)_{L}xSU(2)_{R}xU(1)_{B-L} gauge group with two bidoublets and one doublet Higgs field for electroweak interaction. The lepton fields are represented as a doublet of SU(2)for both left and right fields. By using the pattern of symmetry breaking emerges as the minimum of the Higgs potential for a range of parameters, we show that the domination of the V-A over V+A interactions is natural at low energy. The symmetry breaking is the responsible mechanism for the up-down lepton doublet mass difference
We study the Electric Dipole moment of b quark in the general two Higgs Doublet model (model III) and three Higgs Doublet model with O(2) symmetry in the Higgs sector. We analyse the dependency of this quantity to the new phase coming from the complex Yukawa couplings and masses of charged and neutral Higgs bosons. We see that the Electric Dipole moment of b quark is at the order of 10^{-20} e cm, which is an extremely large value compared to one calculated in the SM and also two Higgs Doublet model (model II) with real Yukawa couplings.
The existence of a second Higgs doublet in Nature could lead to a cosmological first order electroweak phase transition and explain the origin of the matter-antimatter asymmetry in the Universe. We explore the parameter space of such a two-Higgs-doublet-model and show that a first order electroweak phase transition strongly correlates with a significant uplifting of the Higgs vacuum w.r.t. its Standard Model value. We then obtain the spectrum and properties of the new scalars $H_0$, $A_0$ and $H^{\pm}$ that signal such a phase transition, showing that the decay $A_0 \rightarrow H_0 Z$ at the L…
We study some implications of the presence of two inert scalar doublets which are charged under a dark Abelian gauge symmetry. Specifically, we investigate the effects of the new scalars on oblique electroweak parameters and on the interactions of the 125 GeV Higgs boson, especially its decay modes $h\toγγ,γZ$, and trilinear coupling, all of which will be probed with improved precision in future Higgs measurements. Moreover, we explore how the inert scalars may give rise to strongly first-order electroweak phase transition and also show its correlation with sizable modifications to the Higgs t…
We extend the so-called singlet doublet dark matter model, where the dark matter is an admixture of a Standard Model singlet and a pair of electroweak doublet fermions, by a singlet scalar field. The new portal coupling of it with the dark sector not only contributes to the dark matter phenomenology (involving relic density and direct detection limits), but also becomes important for generation of dark matter mass through its vacuum expectation value. While the presence of dark sector fermions affects the stability of the electroweak vacuum adversely, we find this additional singlet is capable…
We study the lepton electric dipole moments in the split fermion scenario, in the two Higgs doublet model, where the new Higgs scalars are localized around the origin in the extra dimension, with the help of the localizer field. We observe that the numerical value of the electron (muon, tau) electric dipole moment is at the order of the magnitude of 10^{-31} (10^{-24}, 10^{-22}) (e-cm) and this quantity is sensitive the new Higgs localization in the extra dimension.
Electroweak baryogenesis fails in the SM because of too small CP violation and the lack of a strong first-order phase transition. It has been shown that supersymmetric models allow for successful baryogenesis, where the Higgsinos play an important role in the transport processes that generate the asymmetry. I will demonstrate that also non-supersymmetric models can provide the observed baryon asymmetry. The top quark takes the role of the Higgsinos. Focusing on the two-Higgs doublet model, I will discuss details of the phase transition and consequences for Higgs physics and EDM searches.
We study the predictions of the left-right model of electroweak interaction based on $SU(2)_{L}\otimes SU(2)_{R}\otimes U(1)$ gauge group by using one bidoublet and one doublet Higgs fields. We can reproduce the low energy phenomenology of electroweak interaction by choosing the appropriate values of vacuum expectation values of Higgs fields. Leptons can obtain a mass via two scenarios, first via Higgs mechanism with non-zero 'hypercharge-like' $I$ in Lagrangian density mass termms and put the Yukawa couplings $G_{l}>>G_{l}^{*}$, and the second via Higgs mechanism followed by a seesaw mechanis…
A two-component scalar DM scenario comprising an additional scalar doublet and a $Y$ = 0 scalar triplet is proposed. Key features of the ensuing dark matter phenomenology are highlighted with emphasis on inter-conversion between the two dark matter components. For suitable choices of the model parameters, we show that such inter-conversion can explain the observed relic abundance when the doublet dark matter component has mass in the \emph{desert} region while the triplet component has sub-TeV mass. This finding is important in the context of such mass regions known to predict under-abundant r…
Pseudoscalar and charged Higgs bosons production in the processes $μ^+ μ^-\to P^0_i Z^0$, $μ^+μ^- \to H^{\pm}W^{\mp}$ within the models with several Higgs doublets and singlets is considered.
We consider beyond the standard model embedding of inert Higgs doublet fields. We argue that inert Higgs doublets can arise naturally in grand unified theories where the necessary associated $Z_2$ symmetry can occur automatically. Several examples are discussed.
We catalogue and study three-Higgs-doublet models in terms of all possible allowed symmetries (continuous and discrete, Abelian and non-Abelian), where such symmetries may be identified as flavour symmetries of quarks and leptons. We analyse the potential in each case, and derive the conditions under which the vacuum alignments (0,0,v), (0,v,v) and (v,v,v) are minima of the potential. For the alignment (0,0,v), relevant for dark matter models, we calculate the corresponding physical Higgs boson mass spectrum. Motivated by supersymmetry, we extend the analysis to the case of three up-type Higgs…
In this talk, we report unitarity constraints and phenomenological studies at the Large Hadron Collider for the extra Higgs bosons of a Composite 2-Higgs Doublet Model.
We discuss the realization of two Higgs doublets model in the framework of 6 dimensional Gauge-Higgs Unification model with a simple Lie group G_M. Two Higgs SU(2)_L doublets can emerge at the low energy effective theory, and the quartic coupling terms in the scalar potential, essential for the electroweak symmetry breaking, are now G_M gauge invariant and permissive. A realistic two Higgs doublets model can possibly be obtained only when two of the root vectors associated with the would-be Higgs doublets and the root vector for SU(2)_L form an isosceles triangle with vertex angle either of Pi…
We reconsider top condensate models from the perspective that not only two quark composite fields can form but also four quark ones. We obtain a model which contains a Higgs doublet and a Higgs triplet, where one of the neutral components of the Higgs triplet identifies with the Higgs boson found at the LHC. We discuss some of the phenomenological consequences.
We derive the complete set of continuous maximal symmetries for Standard Model (SM) alignment that may occur in the tree-level scalar potential of multi-Higgs Doublet Models, with $n > 2$ Higgs doublets. Our results generalize the symmetries of SM alignment, without decoupling of large mass scales or fine-tuning, previously obtained in the context of two-Higgs Doublet Models.
We consider the Higgs sector of multi-Higgs-doublet models in the presence of simple symmetries relating the various fields. We construct basis invariant observables which may in principle be used to detect these symmetries for any number of doublets. A categorization of the symmetries into classes is required, which we perform in detail for the case of two and three Higgs doublets.
We consider a three Higgs doublet model with an $S_3$ symmetry in which beside the SM-like doublet there are two fermiophobic doublets. Due to the new charged scalars there is an enhancement in the two-photon decay while the other channels have the same decay widths that the SM neutral Higgs. The fermiophobic scalars are mass degenerated unless soft terms breaking the $S_3$ symmetry are added.
Within multi-Higgs-doublet models, one can impose symmetries on the Higgs potential, either discrete or continuous, that mix several doublets. In two-Higgs-doublet model any such symmetry can be conserved or spontaneously violated after the electroweak symmetry breaking (EWSB), depending on the coefficients of the potential. With more than two doublets, there exist symmetries which are always spontaneously violated after EWSB. We discuss the origin of this phenomenon and show its similarity to geometric frustration in condensed-matter physics.
Non-decoupling properties of additional heavy degrees of freedom in the Higgs sector of the Two-Higgs-doublet extension of the Standard model are discussed in a particular case of production of a pair of longitudinaly polarized W-bosons in the e^+e^- annihilation.
We investigate the new contributions to the parameters $g_L$ and $g_R$ of the $Z b \bar b$ vertex in a multi-Higgs-doublet model (MHDM). We emphasize that those contributions generally worsen the fit of those parameters to the experimental data. We propose a solution to this problem, wherein $g_R$ has the opposite sign from the one predicted by the Standard Model; this solution, though, necessitates light scalars and large Yukawa couplings in the MHDM.
The possibility of having relatively large non-decoupling effects of the heavy Higgs particles within the two-Higgs doublet extension of the electroweak standard model is briefly discussed and demonstrated on an example of the one-loop amplitude of the process e^+e^- -> W^+W^-
In this paper, we propose a scheme for neutrino mass generation. A Higgs singlet is introduced in the Standard Model of particle physics (SM). All of this new singlet and the charged and neutral Higgs fields in the original Higgs doublet are assumed to have nonzero vacuum expectation values (VEVs). The normal hierarchy of neutrino masses is evidently preferred in our scheme. The neutrino masses are explicitly calculated.
It is well-known that type II two Higgs doublet models (2HDMs) can struggle to facilitate a strong first-order electroweak phase transition in the early universe whilst remaining theoretically appealing scenarios for many reasons. We analyse this apparent shortfall from the perspective of additional new physics. Starting from a consistent dimension-6 effective field theory Higgs potential extension, we identify the Higgs potential extensions that provide the necessary additional contributions required to achieve a strong first-order electroweak phase transition and trace their phenomenological…
The two Higgs bi-doublet left-right symmetric model (2HBDM) as a simple extension of the minimal left-right symmetric model with a single Higgs bi-doublet is motivated to realize both spontaneous P and CP violation while consistent with the low energy phenomenology without significant fine tuning. By carefully investigating the Higgs potential of the model, we find that sizable CP-violating phases are allowed after the spontaneous symmetry breaking. The mass spectra of the extra scalars in the 2HBDM are significantly different from the ones in the minimal left-right symmetric model. In particu…
A neutrinophilic Higgs model has tiny vacuum expectation value (VEV), which can naturally explain tiny masses of neutrinos. There is a large energy scale hierarchy between a VEV of the neutrinophilic Higgs doublet and that of usual standard model-like Higgs doublet. In this paper we at first analyze vacuum structures of Higgs potential in both supersymmetry (SUSY) and non-SUSY neutrinophilic Higgs models, and next investigate a stability of this VEV hierarchy against radiative corrections. We will show that the VEV hierarchy is stable against radiative corrections in both Dirac neutrino and Ma…
We investigate the differential branching ratio, branching ratio, differential forward-backward asymmetry, the forward-backward asymmetry of the lepton pair and the lepton polarization asymmetry of the exclusive $B\to τ^+ τ^- γ$ decay in the general two Higgs doublet model including the neutral Higgs boson effects. We analyse the dependencies of these quantities on the model parameters and also on the neutral Higgs boson effects. We found that they get considerable enhancement from the two Higgs doublet model compared to the standard model and neutral Higgs boson effects are quite sizable.
We study the radiative lepton flavor violating l_1->l_2γdecays in the two Higgs doublet model with localized new Higgs doublet in the Randall Sundrum background. We estimate the contributions of the KK modes of new Higgs bosons and left (right) handed charged lepton doublets (singlets) on the branching ratios of the decays considered. We observe that there is an enhancement in the branching ratios with the addition of new Higgs boson and lepton KK modes.
We calculate masses, production cross sections, and decay rates in the Two Higgs Doublet Model of type II. We also discuss running coupling constants and Grand Unification.
With no conclusive signal till date of the minimal supersymmetric and extra dimensional models at the Large Hadron Collider (LHC), the issue of fine-tuning of the Higgs mass still calls for some attention. It could be very possible that the observed Higgs boson of mass 125 GeV has its origin in a non-supersymmetric extended scalar sector, and, it still has properties strikingly similar to the Standard Model Higgs. In such cases, however, one relies upon possible cancellations in the quadratic divergence of the Higgs mass to uphold naturalness. In this work, we have investigated this possibilit…
Spontaneous CP violation motivates the introduction of two Higgs doublets in the electroweak theory, such a simple extension of the standard model has five physical Higgs bosons and rich CP-violating sources. Exploration on more than one Higgs boson is a direct evidence for new physics beyond the standard model. The neutral Higgs production at LHC is investigated in such a general two Higgs doublet model with spontaneous CP violation, it is shown that the production cross section and decays of the neutral Higgs boson can significantly be different from the predictions from the standard model.
We write down the renormalization-group equations for the Yukawa-coupling matrices in a general multi-Higgs-doublet model. We then assume that the matrices of the Yukawa couplings of the various Higgs doublets to right-handed fermions of fixed quantum numbers are all proportional to each other. We demonstrate that, in the case of the two-Higgs-doublet model, this proportionality is preserved by the renormalization-group running only in the cases of the standard type-I, II, X, and Y models. We furthermore show that a similar result holds even when there are more than two Higgs doublets: the Yuk…
The two-Higgs-doublet model provides a simple, yet interesting, generalization of the SM Higgs sector. We study the CP-conserving version of this model with general, flavor-diagonal, Yukawa couplings. Indirect constraints are obtained from flavor physics on the charged Higgs boson mass and couplings. The relation of these bounds to those for the more specialized two-Higgs-doublet model types with a $Z_2$ symmetry is discussed.
The radiative B ->τ^+ τ^- γdecay is investigated in the framework of the two Higgs doublet model . The dependence of the differential branching ratio on the photon energy and the branching ratio on the two Higgs doublet model parameters, m_{H^\pm} and \tan β, are studied. It is shown that there is an enhancement in the predictions of the two Higgs doublet model compared to the Standard model case. We also observe that contributions of neutral Higgs bosons to the decay are sizable when \tanβis large.
Using the experimental data on meson decay rates, mixing and CP violation we set competitive upper and lower limits to the parameter tan(beta) as a function of the mass of the charged Higgs m_H in the Two Higgs Doublet Model (Model II).
We study the electroweak phase transition in the framework of scalar singlet-doublet mixed dark matter model, where the particle dark matter candidate is the lightest neutral Higgs that comprised of the CP-even component of inert doublet and a singlet scalar. The dark matter can be dominated by the inert doublet or singlet scalar depending on the mixing. We present several benchmark models to investigate the two situations after imposing several theoretical and experimental constraints. An additional singlet scalar and the inert doublet drive the electroweak phase transition to be strongly fir…
We study the strength of a first-order electroweak phase transition in the Inert Doublet Model (IDM), where particle dark matter (DM) is comprised of the lightest neutral inert Higgs boson. We improve over previous studies in the description and treatment of the finite-temperature effective potential and of the electroweak phase transition. We focus on a set of benchmark models inspired by the key mechanisms in the IDM leading to a viable dark matter particle candidate, and illustrate how to enhance the strength of the electroweak phase transition by adjusting the masses of the yet undiscovere…
We report the recent progress in understanding of symmetries which can be implemented in the scalar sector of electroweak symmetry breaking models with several Higgs doublets. In particular we present the list of finite reparametrization symmetry groups which can appear in the three-Higgs-doublet models.
