We discuss the implications of assuming a four-zero Yukawa texture for the properties of the charged Higgs boson within the context of the general 2-Higgs Doublet Model of Type III. We begin by presenting a detailed analysis of the charged Higgs boson couplings with heavy quarks and the resulting pattern for its decays. The production of charged Higgs bosons is also sensitive to the modifications of its couplings, so that we also evaluate the resulting effects on the top decay $t \to b H^{+}$ as well as on `direct' $c\bar{b}\to H^++c. c.$ and `indirect' $q\bar q,gg\to \bar t b H^++c. c.$ production. Significant scope exists at the Large Hadron Collider for several $H^\pm$ production and decay channels combined to enable one to distinguish between such a model and alternative 2-Higgs doublet scenarios.
We discuss the Yukawa coupling unification, a very interesting prediction of the grand unified theory, in the context of scenarios with more than one pair of Higgs doublet since the current LHC constraint has become a problem for the Yukawa unification scenarios with just one pair of Higgs doublet. More than one pair of Higgs doublets can easily arise in missing partner mechanism which solves the doublet-triplet splitting problem. In such a scenario, the Yukawa unification occurs at a medium $\tanβ$ value, e.g., $\sim$ 30, which corresponds to much smaller threshold corrections compared to usu…
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…
In multi-Higgs-doublet models the alignment in flavour space of the relevant Yukawa matrices guarantees the absence of tree-level flavour-changing couplings of the neutral scalar fields. We analyze the consequences of this condition within the two-Higgs-doublet model and show that it leads to a generic Yukawa structure which contains as particular cases all known specific implementations of the model based on Z_2 symmetries. All possible freedom in the Yukawa sector gets parametrized in terms of three complex couplings. In spite of having flavour conservation in the neutral scalar couplings, t…
In the two Higgs doublet model, natural flavour conservation can be achieved through the use of a discrete Z2 symmetry. A less restrictive condition is the requirement of alignment in the Yukawa sector. So far, alignment has been an anzatz, not rooted in a specific model. In this letter we present a model for alignment, which starts with 2+N Higgs doublets, with natural flavour conservation imposed by a discrete symmetry. Only two of these scalars couple to the fermions, the other N scalars are in a hidden sector. Assuming that the two scalar doublets coupled to fermions are heavy, their decou…
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 study how general two Higgs doublet models can be constrained by considering their properties under renormalization group evolution of the Yukawa couplings. We take into account both the appearance of a Landau pole as well as off-diagonal Yukawa couplings leading to flavour changing neutral currents in violation with experimental constraints at the electroweak scale. We find that the latter condition can be used to limit the amount of Z2 symmetry breaking allowed in a given model.
We present new variants of the Two Higgs-Doublet Model where all Yukawa couplings with physical Higgs bosons are controlled by the quark mixing matrices of both chiralities, as well as, in one case, the ratio between the two scalar doublets' vacuum expectation values. We obtain these by imposing approximate symmetries on the Lagrangian which, in one of the cases, clearly reveals the model to be the electroweak remnant of the Minimal Left-Right Symmetric Model. We also argue for the benefits of the bidoublet notation in the Two Higgs-Doublet Model context for uncovering new models.
The O(alpha m_t^2/m_W^2) corrections to top quark pair production by gluon-gluon fusion at the LHC are calculated in two-Higgs-doublet models. We find that the correction to the cross-section can exceed about -10% for certain parameter values.
In multi-Higgs-doublet models, the alignment in flavour space of all Yukawa matrices coupling to a given right-handed fermion guarantees the absence of tree-level flavour-changing neutral couplings, while introducing new sources of CP violation. With N Higgs doublets (and no right-handed neutrinos) the Yukawa Lagrangian is characterized by the fermion masses, the CKM quark mixing matrix and 3(N-1) complex couplings. Quantum corrections break the alignment, generating a minimal-flavour-violation structure with flavour-blind phases. The aligned multi-Higgs-doublet models lead to a rich and viabl…
With discovery of the 125 GeV boson $h^0$, the existence of a second doublet is very plausible. We show that the "alignment" phenomenon, that $h^0$ is found to resemble closely the Standard Model Higgs boson, may correspond to Higgs quartic couplings $η_i$ that are ${\cal O}(1)$ in strength. If the exotic bosons of the second doublet possess extra top Yukawa couplings, which are the least constrained by data, such a two Higgs doublet model could drive electroweak baryogenesis, as well as further "protect" the apparent alignment. The exotic Higgs bosons can be sub-TeV in mass while remaining we…
We compute the beta functions for the three gauge couplings and the Yukawa matrices of a general two-Higgs-doublet model in the modified minimal subtraction scheme to three loops. The calculations are performed using Lorenz gauge in the unbroken phase. We discuss in detail the occurence of poles in anomalous dimensions and propose practical prescriptions to avoid them. We provide explicit results for the often used $\mathbb{Z}_2$-symmetric versions of the two-Higgs-doublet model of type I, II, X and Y. Furthermore, we provide the first independent cross-check of the three-loop Yukawa coupling …
The effect of $Z_3$ symmetry on the general Two Higgs Doublet Model is explored. Of particular interest is the question of what can a $Z_3$ symmetry do beyond the usual case with $Z_2$. There are two independent scenarios that give some interesting results: first, by giving non-trivial charges to the Standard Model fermions, it is possible to use the $Z_3$ symmetry of the scalar potential to generate potentially useful Yukawa textures. This is not possible with $Z_2$. A series of possibilities is presented where their viability is addressed and a specific example in the quark sector is given f…
We investigate the production of Higgs bosons $A/h$ via the Yukawa process $Z\ra f\bar{f} \ra f\bar{f} A/h $ taking into account QCD corrections and fermion mass effects. We estimate the discovery reach of this process and/or bounds on the parameter space of two-Higgs doublet models which can be derived from the analysis of $b {\bar b} τ^+ τ^-$ events at LEP1. These limits have important consequences for extended models of electroweak interactions and their experimental verification/improvement are welcome.
A general method for classifying the possible quark models of a multi-Higgs-doublet model, in the presence of Abelian symmetries, is presented. All the possible sets of textures that can be present in a given sector are shown, thus turning the determination of the flavor models into a combinatorial problem. Several symmetry implementations are studied for two and three Higgs doublet models. Some models implementations are explored in great detail, with a particular emphasis on models known as Branco-Grimus-Lavoura and nearest-neighbour-nnteraction. Several considerations on the flavor changing…
We calculate Yukawa corrections of order $α_{ew} M_t^2/M_W^2$ to single top quark production via $q \bar q'\rightarrow t \bar b$ at the Fermilab Tevatron in the two-Higgs-doublet models. In our calculation we also keep the terms proportional to $ M_b^2 \tan^2 β$ since their effects may become rather important for large $\tanβ$. The corrections can amount to more than a 15\% reduction in the production cross section relative to the tree level result in the general two-Higgs-doublet model, and a 10\% enhancement in the minimal supersymmetric model, which might be observable at a high-luminosity …
There are theoretical speculations that the top quark may have different properties from that predicted by the standard model. We use an effective Lagrangian technique to model such a non-standard top quark scenario and study its effects on the electroweak baryogenesis, low and high energy physics.
The quark mass matrices ansatze proposed by Fritzsch, Du-Xing and Fukuyama-Nishiura in the framework of the general two Higgs doublet model are studied. The corresponding Yukawa matrices in the flavor basis in the different cases considered are discussed. The corresponding Cabbibo-Kobayashi-Maskawa matrix elements are computed in all cases and compared with their experimental values. The complex phases of the ansatze are taken into account and the CP violating phase $δ$ is computed. Finally, in order to observe the influence of the different kind of textures of Yukawa coupling matrices conside…
Unitarity constraints for Yukawa couplings are considered in the Two Higgs Doublet Model type III, by using a general expansion in partial waves for fermionic scattering processes. Constraints over general Flavor Changing Neutral Currents are found from that systematic, such bounds compete with those coming from Lagrangian perturbativity requirement but are weaker than those imposed from phenomenological processes and precision tests. Nevertheless, for bounds based on unitarity the number of assumptions is the lowest among phenomenological and theoretical limits. Indeed, these new theoretical …
The most general two Higgs doublet model contains new sources of flavour violation that are usually in conflict with the experimental constraints. One possibility to suppress the exotic contribution to the flavour changing neutral currents consists on imposing the alignment of the Yukawa couplings. This condition presumably holds at a high-energy scale and is spoiled by the radiative corrections. We compute in this letter the size of the radiatively induced flavour violating Higgs couplings at the electroweak scale. These also yield the absolute lower bound on the size of the exotic contributi…
We study the Two Higgs Doublet Model of type II, set limits to the parameter $\tanβ$ as a function of the mass of the charged Higgs $m_{H}$, and find interesting discovery channels in hadron colliders or muon colliders. We also obtain the running coupling constants and discuss Grand Unification. A dissertation submitted to the University of San Francisco-Quito in partial fulfillment of the requirements for the degree of Doctor of Phylosophy.
In the simplest examples of models with a discrete quark-lepton symmetry, an electroweak symmetry breaking sector with more than one Higgs doublet is necessary to obtain the correct mass relations between quarks and leptons. A two Higgs doublet model has flavour-nonconserving Yukawa couplings, which are proportional to the masses of the quark-lepton symmetric partners of the fermions. We describe how flavour changing leptonic decays can occur, with branching ratios not far beyond that currently measureable, enabling investigation of the phenomenology of such models.
The exact alignment of the Yukawa structures on multi-Higgs doublet models provides cancellation of tree-level flavour changing couplings of neutral scalar fields. We show that family symmetries can provide a suitable justification for the Yukawa alignment.
Smallness of neutrino masses can be explained by introducing a tiny vacuum expectation value of an extra-Higgs doublet which couples to right-handed neutrinos ($N_R$). This situation is naturally realized in $ν$-Two Higgs Doublet Model ($ν$THDM), where a TeV-scale seesaw mechanism can work well. We investigate observable phenomenology of $ν$THDM at LHC and ILC experiments. Charged Higgs boson ($H^\pm$) in $ν$THDM is almost originated from the extra-Higgs doublet and its coupling strength to neutrinos are not small. Then this model induces rich phenomenology at the LHC, for example, when $m_{H^…
We discuss possible signatures of the $CP$-odd scalar of two-doublet models at the LHC. We find that the inclusive two-photon decay mode and the decay sequence $A^0 \rightarrow Zh, h \rightarrow γγ$, where $h$ is a $CP$-even neutral scalar, can give viable signals in fairly large and complementary regions of parameter space.
We study flavor violating processes in the production or decay of a neutral pseudoscalar meson $P^0$ in the framework of a general two Higgs Doublet Model type III (2HDM-III). We use a version of the model where Yukawa interactions of neutral Higgs bosons allow for flavor change at the tree-level, but conserves CP symmetry. We focus on all possible $τ^{\pm} \to l^{\pm}P^0 $ and $P^0 \to l^+l'^-$ decay channels, where $l,l'$ are charged leptons. We find that these processes provide complementary information on quark and lepton FCNC Yukawa couplings. In particular flavor violating parameters in …
It is tempting to interpret the minuscule scale of neutrino masses as a symptom of its radiative origin. In light of the notable leap in precision expected at the Future Circular Collider, we explore areas of the parameter space that can simultaneously support the detectable Higgs-strahlung signal with parallel ones from forthcoming measurements in low-energy observables. We pinpoint the role that the extra fermions have in shaping a signal distinct from the pure Inert Doublet one. The details of the full one-loop computation and on-shell renormalization are presented. Both normal and inverted…
Baryogenesis at the electroweak scale depends on divers but identifiable details of bubble wall dynamics and the particle physics. We show that inclusion of the dynamics of relative phase in two-Higgs-doublet model (2HDM) enhances the adiabatic order of the mechanism proposed by McLerran-Shaposhnikov-Turok-Voloshin where the scalar-scalar-vector triangle diagram with top quark in the loop gives rise to a significant contribution to the effective chemical potential biasing the Chern-Simons number. We also show that in 2HDM with less stringent constraints on Yukawa couplings than those imposed b…
We study the most general Multi-Higgs-Doublet Model (MHDM) with Natural Flavor Conservation (NFC). The couplings of a charged scalar $H_i^{\pm}$ to up quarks, down quarks and charged leptons depend on three new complex parameters, $X_i$, $Y_i$ and $Z_i$, respectively. We prove relations among these parameters. We carry out a comprehensive analysis of phenomenological constraints on the couplings of the lightest charged scalar: $X$, $Y$ and $Z$. We find that the general MHDM may differ significantly from its minimal version, the Two-Higgs-Doublet Model (2HDM).
We consider two Higgs doublet models with a softly broken U(1) symmetry, for various limiting values of the scalar mixing angles $α$ and $β$. These correspond to the Standard Model Higgs particle being the lighter CP-even scalar (alignment) or the heavier CP-even scalar (reverse alignment), and also the limit in which some of the Yukawa couplings of this particle are of the opposite sign from the vector boson couplings (wrong sign). In these limits we impose a criterion for naturalness by demanding that quadratic divergences cancel at one loop. We plot the allowed masses of the remaining physi…
We calculate one-loop corrected Yukawa coupling constants $hf\bar{f}$ for the standard model like Higgs boson $h$ in two Higgs doublet models. We focus on the models with the softly-broken $Z_2$ symmetry, which is imposed to avoid the flavor changing neutral current. Under the $Z_2$ symmetry, there are four types of Yukawa interactions. We find that one-loop contributions from extra Higgs bosons modify the $hf\bar{f}$ couplings to be maximally about $5\%$ under the constraint from perturbative unitarity and vacuum stability. Our results show that the pattern of tree-level deviations by the mix…
The scotogenic model is well known for accommodating small neutrino mass and dark matter. Here, we have realized the scotogenic model with the help of discrete flavor symmetry $A_{4}\otimes Z_{4}$. We have obtained three one zero textures of Yukawa coupling matrices from the model and have studied its impact on neutrino phenomenology and related aspects of cosmology. On the basis of $μ-τ$ symmetry, we have further discarded two structures of one zero texture Yukawa coupling matrix. We further analyze if the effective mass of active neutrinos obtained by the virtue of the Yukawa coupling matrix…
We investigate finite abelian groups which can represent symmetries of the N-Higgs-doublet models with quarks. We build a general formalism based on the powerful method of the Smith normal form and obtain an analytic upper bound on the order of abelian symmetry groups for any N. We investigate in detail the case N=2 and rederive known results in a more compact and intuitive fashion. We also study the NHDM with the maximal finite abelian symmetry for all small N cases up to N=5, and show that in each case all Yukawa textures compatible with such symmetry originate from a unique basic structure.…
A pattern of deviations in coupling constants of Standard Model (SM)-like Higgs boson from their SM predictions indicates characteristics of an extended Higgs sector. In particular, Yukawa coupling constants can deviate in different patterns in four types of Two Higgs Doublet Models (THDMs) with a softly-broken Z_2 symmetry. We can discriminate types of THDMs by measuring the pattern of these deviations. We calculate Yukawa coupling constants of the SM-like Higgs boson with radiative corrections in all types of Yukawa interactions in order to compare to future precision data at the Internation…
We study the charged Higgs couplings to fermions in the "democratic" three-Higgs-doublet model, in which one doublet couples to down-type quarks, one to up-type quarks, and one to charged leptons. Flavor-changing neutral Higgs couplings are absent because the Glashow-Weinberg-Paschos condition for natural flavor conservation is in effect. We show that this model reproduces the coupling structure of the charged Higgs boson in the recently-proposed Yukawa-aligned two-Higgs-doublet model, with two subtle constraints that arise from the unitarity of the charged Higgs mixing matrix. Adding a fourth…
Scalar sector offers a valuable avenue to explore its implications in the particle physics phenomenology for new physics and several model dependent phenomena. Two Higgs doublet models are among the promising models for such explorations. In the presence of a standard model Higgs, a two Higgs doublet model is studied in which the two Higgs fields are connected with each other via a scalar singlet field. The study is conducted using Dyson Schwinger equations under the Yukawa vertices set at their tree level form up to certain constants. Among the field propagators, the two Higgs propagators are…
We study the inclusion of new heavy fermions on complex scalar dark matter (DM) phenomenology within gauged two Higgs doublet model (G2HDM). We find that for DM mass above 1 TeV, heavy quarks coannihilations into the Standard Model (SM) quarks and gluons dominate the thermally-averaged cross section relevant for the relic abundance of complex scalar DM. We demonstrate that the effects of QCD Sommerfeld correction as well as QCD bound state formation in determining the DM relic are negligible. We show that the allowed parameter space is significantly constrained by the current PLANCK relic dens…
We study the alignment of Yukawa couplings in the framework of general two Higgs doublet models (2HDMs) considering a scenario in which the lightest neutral Higgs boson is purely CP even while the two heavier neutral Higgs bosons are allowed to mix in the presence of nontrivial CP-violating phases in the Higgs potential. Identifying the lightest neutral Higgs boson as the 125 GeV one discovered at the LHC, we find that the alignment of Yukawa couplings without decoupling could be easily achieved in the type-I 2HDM with no much conflict with the current LHC Higgs precision data. Otherwise, we o…
We study the phenomenology of the charged Higgs boson in the "flipped" two Higgs doublet model, in which one doublet gives mass to up-type quarks and charged leptons and the other gives mass to down-type quarks. We present the charged Higgs branching ratios and summarize the indirect constraints. We extrapolate existing LEP searches for H+H- and Tevatron searches for t tbar with t --> H+ b into the flipped model and extract constraints on MH+ and the parameter tan(beta). We finish by reviewing existing LHC charged Higgs searches and suggest that the LHC reach in this model could be extended fo…
We examine the phenomenology of the $CP$-odd scalar $A^0$ of two-Higgs-doublet models. We explore the parameter space determined by triviality bounds and identify the regions where the $A^0$ can be detected at the LHC in each of the following modes: the inclusive two-photon decay mode, the $l^{\pm}γγX$ mode from $t\overline{t}A^0$ production and the $A^0\rightarrow Zh$ channel with the subsequent decay of the $CP$-even scalar $h$ to two photons. We find that, while the $l^{\pm}γγX$ mode is of limited usefulness, the other two modes can give viable signals in fairly large, and complementary, re…
Two-Higgs-doublet models (2HDM) are simple extensions of the Standard Model (SM) where the scalar sector is enlarged by adding a weak doublet. As a result, the Higgs potential depends in general on several free parameters which have to be carefully chosen to give predictions consistent with the current precision data. We consider a 2HDM invariant under a twisted custodial symmetry and depending only on three extra parameters beyond the SM ones. This model naturally features an inverted mass spectrum with a light pseudoscalar state and a heavy SM-like Higgs boson. We thoroughly analyze direct a…
The processes proton + antiproton -> gamma + heavy-flavour jet(s) + X and proton + proton -> gamma + heavy-flavour jet(s) + X are studied in the framework of a special two-Higgs-doublet model, the MCPM. As distinguishing feature of this model we find that radiative Higgs-boson production and decay lead to heavy flavour c jets but no b jets in the above processes. Thus, the prediction is that b jets should be given by the normal QCD processes whereas for c jets an excess over the QCD expectation should occur. We present results both for Tevatron and LHC energies.
The single Higgs doublet in the standard model (SM) may be the simplest way of introducing electroweak symmetry breaking, but SM extensions with more scalar doublets are not excluded. A special case of the two Higgs doublet models is the inert doublet model - a minimalistic version with interesting phenomenology. These proceedings reviews the inert doublet model's theoretical setup, constraints, collider prospects and its dark matter phenomenology.
In this paper various constraints for the parameter spaces of two variants of the Two Higgs Doublet Model with a Z_2-symmetric potential are reconsidered, including the LHC data on existence of a 125 GeV Higgs-like boson. We analyze the model in which only one of the doublets develops a nonzero vacuum expectation value (VEV) -- the Inert Doublet Model (IDM) and the Mixed Model where both of the doublets have nonzero VEVs. Positivity constraints, conditions determining the type of the vacuum, perturbative unitarity condition, constraints following from electroweak precision tests together with …
The alignment in flavour space of the Yukawa matrices of a general two-Higgs-doublet model results in the absence of tree-level flavour-changing neutral currents. In addition to the usual fermion masses and mixings, the aligned Yukawa structure only contains three complex parameters, which are potential new sources of CP violation. For particular values of these three parameters all known specific implementations of the model based on discrete Z_2 symmetries are recovered. One of the most distinctive features of the two-Higgs-doublet model is the presence of a charged scalar. In this work, we …
We make a phenomenological study of a model with two inert doublets plus one Higgs doublet (I(2+1)HDM) which is symmetric under a Z$_2$ group, preserved after Electro-Weak Symmetry Breaking (EWSB) by the vacuum alignment $(0,0,v)$. This model may be regarded as an extension to the model with one inert doublet plus one Higgs doublet (I(1+1)HDM), by the addition of an extra inert scalar doublet. The neutral fields from the two inert doublets provide a viable Dark Matter (DM) candidate which is stabilised by the conserved $Z_2$ symmetry. We study the new Higgs decay channels offered by the scalar…
In the two-Higgs-Doublet model the alignment of the Yukawa flavour matrices of the two scalar doublets guarantees the absence of tree-level flavour-changing neutral couplings. The resulting fermion-scalar interactions are parameterized in terms of three complex parameters, leading to a generic Yukawa structure which contains as particular cases all known specific implementations of the model based on Z2 symmetries. These three complex parameters are potential new sources of CP violation.
We study the dark matter phenomenology of scotogenic frameworks through a rather illustrative model extending the Standard Model by scalar and fermionic singlets and doublets. Such a setup is phenomenologically attractive since it provides the radiative generation of neutrino masses, while also including viable candidates for cold dark matter. We employ a Markov Chain Monte Carlo algorithm to explore the associated parameter space in view of numerous constraints stemming from the Higgs mass, the neutrino sector, dark matter, and lepton-flavour violating processes. After a general discussion of…
The most general two-Higgs doublet model (2HDM) includes potentially large sources of flavor changing neutral currents (FCNCs) that must be suppressed in order to achieve a phenomenologically viable model. The flavor alignment ansatz postulates that all Yukawa coupling matrices are diagonal when expressed in the basis of mass-eigenstate fermion fields, in which case tree-level Higgs mediated FCNCs are eliminated. In this work, we explore models with the flavor alignment condition imposed at a very high energy scale, which results in the generation of Higgs-mediated FCNCs via renormalization gr…
The new round of experiments, MEG II, COMET/Mu2e, and Mu3e, would soon start to push the $μ\to eγ$, $μN \to eN$ conversion, and $μ\to 3e$ frontier, while Belle II would probe $τ\to μγ$ and $τ\to 3μ$. In the general two Higgs doublet model with extra Yukawa couplings, we show that all these processes probe the lepton flavor violating (LFV) dipole transition that arises from the two loop mechanism, with scalar-induced contact terms subdominant. This is because existing data suggest the extra Yukawa couplings $ρ_{μe},\, ρ_{ee} \lesssim λ_e$, while $ρ_{τμ},\, ρ_{ττ} \lesssim λ_τ$ and $ρ_{tt} \less…
We study the Electric Dipole moment of b quark in the general two Higgs Doublet model (model III) and three Higgs Doublet model with O(2) symmetry in the Higgs sector. We analyse the dependency of this quantity to the new phase coming from the complex Yukawa couplings and masses of charged and neutral Higgs bosons. We see that the Electric Dipole moment of b quark is at the order of 10^{-20} e cm, which is an extremely large value compared to one calculated in the SM and also two Higgs Doublet model (model II) with real Yukawa couplings.
We discuss possible parallel textures of the Yukawa coupling matrices in the generaltwo-Higgs-doublet model (2HDM). In those textures the flavor changing neutral currentsare naturally suppressed. Motivated by a phenomenologically successful texturewith four texture zeros in the standard model, we propose a predictive ansatz for the Yukawa coupling matrices with the same texture in the general 2HDM. Compared with the six texture-zero based ansatz proposed by Cheng and Sher, it is in a better agreement with the data of quark mixings and CP violation. The four texture-zero based ansatz predicts a…
We investigate the deviation in the couplings of the standard model (SM) like Higgs boson ($h$) with a mass of 125 GeV from the prediction of the SM in multi-doublet models within the framework where flavour changing neutral currents at the tree level are naturally forbidden. After we present the general expressions for the modified gauge and Yukawa couplings for $h$, we show the correlation between the deviation in the Yukawa coupling for the tau lepton $hτ^+τ^-$ and that for the bottom quark $hb\bar{b}$ under the assumption of a non-zero deviation in the $hVV$ $(V=W,Z)$ couplings in two Higg…
The present upper bound on $κ_e$, the ratio between the electron Yukawa coupling and its Standard Model value, is of ${\cal O}(600)$. We ask what would be the implications in case that $κ_e$ is close to this upper bound. The simplest extension that allows for such enhancement is that of two Higgs doublet models (2HDM) without natural flavor conservation. In this framework, we find the following consequences: (i) Under certain conditions, measuring $κ_e$ and $κ_V$ would be enough to predict values of Yukawa couplings for other fermions and for the $H$ and $A$ scalars. (ii) In the case that the …
Possible models of Yukawa interaction are discussed in the two Higgs doublet model (THDM) under the discrete symmetry imposed to avoid the flavor changing neutral current at the leading order. It is known that there are four types of such models corresponding to the possible different assignment of charges for the discrete symmetry on quarks and leptons. We first examine decay properties of Higgs bosons in each type of the models, and summarize constraints on the models from current experimental data. We then shed light on the differences among these models in collider phenomenology. In partic…
We discuss how charged-lepton masses can be induced in multi-Higgs doublet models (NHDMs) through renormalization group running of Yukawa couplings. Examples of electron and muon mass generation are presented within scenarios with two- and three-Higgs-doublet models. We also show that quantum corrections to the Yukawa couplings can be naturally of the same order as the tree-level values. The impact of such corrections in NHDMs with right-handed neutrinos is briefly commented.
