In this paper the triple Higgs production in a general two Higgs doublet model (2HDM) is studied. The production process is e+e- -> H+H-H0 followed by the charged Higgs decay to a pair of tau nu and the neutral Higgs decay to bb. The alternative process H+W-H0 is also included as a source of charged Higgs signal in the analysis. The focus is on a future e+e- linear collider operating at sqrt(s) = 1.5 TeV. The final state under consideration (tau tau bb ETmiss) is suitable for electroweak background rejection using the b-tagging tools. It is shown that although the signal cross section is small, with a reasonable background suppression, high signal significance values are achievable at an integrated luminosity 500 fb-1 depending on the charged Higgs mass, tanbeta and the CP-odd neutral Higgs mass. Finally results are quoted in terms of the signal significance for charged Higgs in the mass range 170 < mH+ < 400 GeV.
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.
A novel mechanism to realize the triplet-doublet splitting in supersymmetric SU(5) grand unified theories is proposed in the framework of higher dimensional theories where chiral multiplets are localized due to kink configuration of a SU(5) singlet. An adjoint Higgs field which spontaneously breaks the SU(5) gauge symmetry is assumed to be involved with the localization process, splitting the wave functions of the color-triplet Higgs from its doublet counterpart. The resulting effective four-dimensional theory does not possess manifest SU(5) invariance. By adjusting couplings, the doublet mass…
We propose a new mechanism towards the solution to the doublet-triplet Higgs mass splitting problem in the supersymmetric grand unified theory. Our model is based on the gauge group $SU(5)_H \times SU(5)_{GUT}$, where $SU(5)_H$ and $SU(5)_{GUT}$ are a new strong gauge interaction and the ordinary grand unified gauge group, respectively. The doublet-triplet Higgs mass splitting is realized through the quantum deformation of moduli space caused by the strong $SU(5)_H$ gauge dynamics. The low energy description of our model is given by the minimal supersymmetric standard model.
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…
If the minimal standard model of particle interactions is extended to include a scalar triplet with lepton number $L=-2$ and a scalar doublet with $L=-1$, neutrino masses $m_ν\sim μ_{12}^4 v^2/M^5 \sim 10^{-2}$ eV is possible, where $v \sim 10^2$ GeV is the electroweak symmetry breaking scale, $M \sim 1$ TeV is the typical mass of the new scalars, and $μ_{12} \sim 1$ GeV is a soft lepton-number-violating parameter.
The anomalous U(1)_A symmetry provides a generic method of getting accidental symmetries. Therefore, it can play a crucial role in solving the doublet-triplet splitting and the μ-problems via the `pseudo-Goldstone' mechanism: U(1)_A can naturally uncorrelate the two grand unified Higgs sectors in the superpotential and simultaneously induce the desired expectation values through the Fayet-Iliopoulos D-term. The zero modes of the resulting compact vacuum degeneracy can be identified with the massless electroweak Higgs doublets. This automatically solves the doublet-triplet splitting and the μ-p…
It is well known that a Weinberg dimension-5 operator for small neutrino masses can be realized at tree level in three types of renormalizable models: (i) the type-I seesaw mediated by fermion singlets, (ii) the type-II seesaw mediated by Higgs triplets, (iii) the type-III seesaw mediated by fermion triplets. We here point out such operator can be also induced at tree level by vector-like lepton doublets in association with unusual fermion singlets, Higgs triplets or fermion triplets. If these unusual fermion singlets, Higgs triplets or fermion triplets are heavy enough, their decays can gener…
In the case of minimal supersymmetric extension of the Standard Model (MSSM), when the pseudoscalar Higgs boson mass is less than the supersymmetry energy scale, the effective theory at the electroweak scale is a two-Higgs-doublet model. We diagonalize the mass matrix of the general two-Higgs-doublet model, expressing Higgs boson self-couplings in terms of two mixing angles and four Higgs boson masses, and derive in a compact form the complete set of Feynman rules, including quartic couplings in the Higgs sector, for the case of CP-violating potential. Some processes of double and triple Higgs…
In this paper, we consider the possibility of generating the observed baryon asymmetry of the Universe via leptogenesis in the context of triplet fermion mediated type-III seesaw model of neutrino mass. With a hierarchical spectrum of the additional fermions, the lower bound on the lightest triplet mass is $\sim 10^{10} {\rm~GeV}$ for successful leptogenesis, a couple of orders higher than that of the type-I case. We investigate the possibility of lowering this bound in the framework of two-Higgs-doublet models. We find that the bounds can be lowered down to $10^7$ GeV for a hierarchical spect…
We consider a dark matter (DM) model that arises from the interplay of two simplified dark matter models, namely the doublet-triplet fermion model and the doublet-triplet scalar model. Despite being excellent exponents of the WIMP paradigm, the physics related to DM in each of these models fails at the same time to account for neutrino masses. It turns out that from the combination of these two models it is possible to generate neutrino masses at one-loop level in the four topologies that are realizations of the Weinberg operator for neutrino masses at one-loop. In this work, we combine both m…
A simple higher dimensional mechanism of the doublet-triplet splitting is presented in a five dimensional supersymmetric SU(5) GUT on $S^1/Z_2$. The splitting of multiplets is realized by a mass term of Higgs hypermultiplet which explicitly breaks SU(5) gauge symmetry. Depending on the sign of mass, zero mode Higgs doublets and triplets are localized on the either side of the fixed points. The mass splitting is realized due to the difference of magnitudes of the overlap with a brane localized or a bulk singlet field. No unnatural fine-tuning of parameters is needed. The proton stability is ens…
We consider the quark sector of theories containing three scalar SU(2)_L doublets in the triplet representation of A4 (or of S4) and three generations of quarks in arbitrary A4 (or S4) representations. We show that, for all possible choices of quark field representations and for all possible alignments of the Higgs vacuum expectation values that can constitute global minima of the scalar potential, it is not possible to obtain simultaneously non-vanishing quark masses and a non-vanishing CP-violating phase in the CKM quark mixing matrix. As a result, in this minimal form, models with three sca…
We study double Higgs production at the future Linear Collider in the framework of the Two Higgs Doublet Models through the following channels: $e^+e^- \to Φ_i Φ_j Z$, $Φ_i=h^0, H^0, A^0, H^\pm$. All these processes are sensitive to triple Higgs couplings. Hence observations of them provide information on the triple Higgs couplings that help reconstructing the scalar potential. We also discuss the double Higgs-strahlung $e^+e^- \to h^0 h^0 Z$ in the decoupling limit where $h^0$ mimics the SM Higgs boson. The processes $e^+e^- \to h^0 h^0 Z$ and $e^+e^- \to h^0 H^0 Z$ are also discussed in the …
We present a new solution to the doublet-triplet splitting problem which also works in a supersymmetric SU(5) grand unified theory and is testable at TeV-scale collider experiments. In our model, the SU(5) symmetry is broken through the Hosotani mechanism. Thanks to the phase nature of the Hosotani-breaking, the "missing VEV" can be realized even in an SU(5) model. A general and distinctive prediction of this solution is the existence of light adjoint chiral supermultiplets with masses of the supersymmetry breaking scale. Though these disturb the gauge coupling unification, it can be recovered…
We studied the signatures at the LHC of the electroweak SU(2) lepton doublet which embeds a doubly charged lepton. The doubly charged lepton pair and single production rates, which are different from the triplet case, are studied and all the detectable decay modes are considered. We also applied the same kinematic cuts as in triplet case to reduce the background at LHC and the needed integrated luminosities to find the doubly charged leptons with different masses are analyzed. We also suggested a method to distinguish the exotic lepton doublet and triplet.
The production of triple Higgs $(H^+H^-H^0)$, $(H^+H^-h^0)$ and pair wise charged Higgs boson $(H^+H^-)$ is studied in the context of future linear colliders within the Two-Higgs Doublet Model (2HDM) type II. The aim is to compare sources of charged Higgs pair through the above processes, i.e., double and triple Higgs production. Cross-sections are calculated at the leading order in 2HDM type II and Minimal Supersymmetric Standard Model (MSSM). Several orders of magnitude ($\sim 10^{4}$) enhancement is observed in 2HDM compared to MSSM, while no sizable enhancement is seen in muon collider ver…
By extending the Standard Model with singlet-doublet fermions and triplet scalars, all odd under a new $Z_2$ symmetry, we introduce a radiative seesaw model that can simultaneously account for dark matter, explain the existence of neutrino masses and allow for gauge coupling unification. We explore the viable parameter space of the model after imposing collider, Higgs mass, dark matter, neutrino mass and lepton flavour violation constraints. We find that dark matter in this model is fermionic for masses below about 1 TeV and scalar above and observe a high degree of complementarity between dir…
Matter-Higgs unification in string-inspired supersymmetric Grand Unified Theories predicts the existence of colored states in the Higgs multiplets and calls for two extra generations of Higgs-like fields ('unhiggses'). If these states are present near the TeV scale, gauge-coupling unification points to the existence of two distinct scales, 10^15 GeV where right-handed neutrinos and a Pati-Salam symmetry appear, and 10^18 GeV where complete unification is achieved. Baryon-number conservation, while not guaranteed, can naturally emerge from an underlying flavor symmetry. Collider signatures and …
We discuss how the double missing partner mechanism solution to the doublet-triplet splitting problem in four-dimensional supersymmetric SU(5) Grand Unified Theories (GUTs) can be combined with predictive models for the quark-lepton Yukawa coupling ratios at the GUT scale. It is argued that towards this goal a second SU(5) breaking Higgs field in the adjoint representation is very useful and we discuss all possible renormalizable superpotentials with two adjoint Higgs fields and calculate the constraints on the GUT scale and effective triplet mass from a two-loop gauge coupling unification ana…
We investigate the implication of the recent discovery of a Higgs-like particle in the first phase of the LHC Run 1 on the Inert Higgs Doublet Model (IHDM). The determination of the Higgs couplings to SM particles and its intrinsic properties will get improved during the new LHC Run 2 starting this year. The new LHC Run 2 would also shade some light on the triple Higgs coupling. Such measurement is very important in order to establish the details of the electroweak symmetry breaking mechanism. Given the importance of the Higgs couplings both at the LHC and $e^+e^-$ Linear Collider machines, ac…
We present a new approach to realizing the Dimopoulos-Wiczek mechanism for doublet-triplet splitting in supersymmetric SO(10). The method can be used to achieve strong suppression of proton decay in a straightforward manner and is relatively economical; in particular the particle spectrum required for its implementation is consistent with the constraints from string compactification at Kac-Moody level two. We construct two examples of realistic models based on this idea. These models have no unwanted flat directions and do not make use of any nonrenormalizable operators to stabilize the vacuum…
We present a solution to the doublet-triplet splitting problem in supersymmetric $SU(5)$ by enlarging the group to $SU(5)\times SU(5)$ and by introducing two supermultiplets in the $(5,5)$ and $(\bar{5},\bar{5})$ representations of the extended group. The non-perturbative superpotential associated to this gauge group provides not only the correct gauge symmetry breaking but also the large mass for the Higgs triplets associated to massless Higgs doublet. The method has all the advantages of the sliding singlet model but without the drawbacks.
In this article we consider a comparative study between Type-I 2HDM and $Y=0$, $SU(2)$ triplet extensions having one $Z_2$-odd doublet and triplet that render the desired dark matter(DM). For the inert doublet model (IDM) either a neutral scalar or pseudoscalar can be the DM, whereas for inert triplet model (ITM) it is a CP-even scalar. The bounds from perturbativity and vacuum stability are studied for both the scenarios by calculating the two-loop beta functions. While the quartic couplings are restricted to $0.1-0.2$ for a Planck scale perturbativity for IDM, these are much relaxed ($0.8$ )…
The excess of top quark forward-backward asymmetry ($A^t_{FB}$) reported by the Tevatron and the enhancement of the Higgs decay to diphoton observed by the LHC may point to a same origin of new physics. In this note we examined such anomalies in the two-Higgs-doublet model with a color-triplet scalar. We found that under current experimental constraints this model can simultaneously explain both anomalies at $1σ$ level. Also, we examined the Higgs decay $h\to Zγ$ and displayed its correlation with $h\to γγ$. We found that unlike other models, this model predicts a special correlation between $…
The supersymmetric $SU(6)$ model equipped by the flavour-blind discrete gauge symmetry $Z_3$ is considered. It provides simultaneous solution to the doublet-triplet splitting problem, $μ$-problem and leads to natural understanding of fermion flavour. The Higgs doublets arise as Goldstone modes of the spontaneously broken {\em accidental} global symmetry $SU(6)\times U(6)$ of the Higgs superpotential. Their couplings to fermions have peculiarities leading to the consistent picture of the quark and lepton masses and mixing, without invoking the horizontal symmetry or zero texture concepts. In pa…
We consider the two-Higgs-doublet model with explicit CP-violation, where the effective Higgs potential is not CP-invariant at the tree-level. Three neutral Higgs bosons of the model are the mixtures of CP-even and CP-odd bosons which exist in the CP-conserving limit of the theory. The mass spectrum and tree-level couplings of the neutral Higgs bosons to gauge bosons and fermions are significantly dependent on the parameters of the Higgs boson mixing matrix. We calculate the Higgs-gauge boson, Higgs-fermion, triple and quartic Higgs self-interactions in the MSSM with explicit CP-violation in t…
We investigate a simple variant of type-II seesaw, responsible for neutrino mass generation, where the particle spectrum is extended with one singlet right-handed neutrino and an inert Higgs doublet, both odd under an additional $Z_2$ symmetry. While the role of the dark matter is played by the lightest neutral component of the inert Higgs doublet, its interaction with the Standard Model lepton doublets and the right-handed neutrino turns out to be crucial in generating the correct baryon abundance of the Universe through flavored leptogenesis from the decay of the $SU(2)_L$ scalar triplet, in…
I present a list of minima for 3 Higgs doublet models and 6 Higgs doublet models that are invariant under the discrete symmetries $Δ(3n^2)$ and $Δ(6n^2)$. I use the invariant approach formalism on the scalar sector and, with relevant Spontaneous CP-odd invariants, determine if the minima lead to Spontaneous CP violation. I identify in which cases the VEVs have calculable phases, finding several new cases of Spontaneous Geometrical CP Violation, including the first cases for 6 Higgs doublet models.
We perform an exclusive study on the Feebly Interacting Massive Particle (FIMP) dark matter candidate in an extended hyperchargeless ($Y=0$) Higgs triplet model. The additional $Z_2$ odd neutral fermion singlet plays the role of dark matter with support from two other vector-like fermion doublets. The mixing between the neutral component of a doublet and singlet fermions controls the current relic density through the Freeze-in mechanism, whereas the additional doublet fermion helps to get the neutrino mass and mixing angles. We obtain a broad region of the parameter spaces satisfying the curre…
We propose a scalar Triplet extension of the standard model (SM) to unify the origin of neutrino mass with the visible and dark matter component of the Universe. We assume that the scalar triplet is super heavy, so that its CP-violating out-of-equilibrium decay in the early Universe not only produce asymmetric dark matter which is the neutral component of an additional vector like fermion doublet, but also give rise to lepton asymmetry. The latter gets converted to observed baryon asymmetry via B+L violating sphaleron processes. Below electroweak phase transition the scalar triplet acquires a …
We present a study of triple Higgs boson (3H) production at the International Linear Collider (ILC) within the general Two-Higgs-Doublet Model (2HDM). We compute the production cross-sections at the leading-order for the 3H final states and find values up to sigma ~ 0.1 pb. This result represents a large enhancement with respect to the corresponding MSSM cross-sections, which stay typically at the level of sigma ~ 10^(-6) pb or less. Furthermore, since the 3H cross-sections in the general 2HDM can be of the order of the double Higgs production cross-sections, such 3H processes could be a compe…
The determination of the Higgs self-coupling in the Standard Model is one of the primary motivations among all the future lepton colliders. Extending the scalar sector of the Standard Model by a new Higgs doublet with a quadratic Higgs potential gives many new features to the model, and most importantly additional Higgs self-couplings emerge. Measuring these couplings is the only way to reconstruct the shape of the scalar potential. In this study, the numerical analysis of several scattering processes is carried out for the two-Higgs-doublet model to determine all these Higgs self-couplings. T…
To solve the doublet-triplet splitting problem in SU(5) grand unified theories, we propose a four dimensional orbifold grand unified theory by acting Z2 on the SU(5) gauge group. Without an adjoint Higgs, the orbifold procedure breaks the SU(5) gauge symmetry down to the standard model gauge group, and removes the triplet component of the fundamental SU(5) Higgs. In the supersymmetric framework, we show that the orbifold procedure removes two triplet superfields of the Higgs multiplets and leaves us with the minimal supersymmetric standard model, which also solves the hierarchy problem and rea…
We propose a natural Higgs sector in E_6 grand unified theory (GUT) with anomalous U(1)_A gauge symmetry. In the scenario, the doublet-triplet splitting can be realized while the proton decay via dimension 5 operator is suppressed. The gauge coupling unification is also realized without finetuning. The GUT scale is generally lower than the usual GUT scale 2\times 10^{16} GeV, the proton decay via dimension 6 operator can be seen in near future experiment. The lifetime of nucleon in the model is roughly estimated as τ_p(p\to e^+π^0)\sim 3\times 10^{33} years. It is shown that the Higgs sector i…
It is usually assumed that the proton stability requires the coloured triplet partner of the electroweak Higgs doublet to be superheavy (with a mass $\sim M_{GUT}$). We show that this is a very model-dependent statement and the colour triplet can be as light as the weak doublet without leading to the proton decay problem: instead of using the mass difference the splitting can occur between the doublet and triplet Yukawa coupling constants. In this scenario the GUT symmetry breaking automatically induces an extremely strong suppression $\sim M_W/M_{GUT}$ of the coloured Higgs effective Yukawa c…
We extend the Standard Model (SM) by adding a pair of fermionic SU(2)-doublets with opposite hypercharge and a fermionic SU(2)-triplet with zero hypercharge. We impose a discrete Z_2-symmetry that distinguishes the SM fermions from the new ones. Then, gauge invariance allows for two renormalizable Yukawa couplings between the new fermions and the SM Higgs field, as well as for direct masses for the doublet (M_D) and the triplet (M_T). After electroweak symmetry breaking, this model contains, in addition to SM particles, two charged Dirac fermions and a set of three neutral Majorana fermions, t…
In this study the charged Higgs signal through triple or double Higgs production in a general two Higgs doublet model (2HDM) is investigated. The main production process is $e^+e^- \rightarrow H^+H^-H^0$ followed by the charged Higgs decay to a pair of $τν$ and the neutral Higgs decay to $b\bar{b}$. The alternative process $H^+W^-H^0$ is also included as a source of charged Higgs signal in the analysis having comparable cross-section. The focus is on a future $e^+e^-$ linear collider operating at $\sqrt{s}=1.5$ TeV. The final state under consideration ($τ^+ τ^- b \bar{b} E^{\textnormal{miss}}_…
We present a class of realistic unified models based on supersymmetric SO(10) wherein issues related to natural doublet-triplet (DT) splitting are fully resolved. Using a minimal set of low dimensional Higgs fields which includes a single adjoint, we show that the Dimopoulos--Wilzcek mechanism for DT splitting can be made stable in the presence of all higher order operators without having pseudo-Goldstone bosons and flat directions. The μterm of order TeV is found to be naturally induced. A Z_2-assisted anomalous U(1)_A gauge symmetry plays a crucial role in achieving these results. The thresh…
In supersymmetric models the presence of Higgs triplets introduce new quartic interactions for the doublets that may raise the mass of the lightest CP-even field up to 205 GeV. We show that the complete effect of the triplets can be understood by decoupling them from the minimal sector and then analyzing the vacuum and the spectrum of the two-Higgs doublet model that results. We find that the maximum value of m_h is only achieved in a very definite region of the parameter space. In this region, however, radiative corrections decrease the bound to 190 GeV.
We investigate the constraints on the leptoquark Yukawa couplings and Higgs-leptoquark quartic couplings for scalar doublet leptoquark $\tilde{R}_2$, scalar triplet leptoquark $\vec S_3$ and their combination with both three generations and one generation from perturbative unitarity and vacuum stability. Perturbative unitarity of all the dimensionless couplings have been studied via one- and two-loop beta-functions. Introduction of new $SU(2)$ multiplets in terms of these leptoquarks fabricate Landau poles at two-loop level in the gauge coupling $g_2$ at $10^{19.7}$ GeV and $10^{14.4}$ GeV, re…
We find if a Higgs triplet with hypercharge has a special dimension-6 operator with the standard model Higgs doublet, i.e. a square of the trilinear triplet-doublet coupling, its scalar(pseudo-scalar) component can obtain a small quadratic term while its pseudo-scalar(scalar) and charged-scalar components can hold their masses heavy enough. Such split Higgs triplet can spontaneously develop a small vacuum expectation value to realize a Majorana neutrino mass generation without causing any high-dimensional lepton number violations including the well-known Weinberg dimension-5 operator. Alternat…
We analyze the Higgs doublet-triplet mass splitting problem in the version of flipped SU(5) derived from string theory. Analyzing non-renormalizable terms up to tenth order in the superpotential, we identify a pattern of field vev's that keeps one pair of electroweak Higgs doublets light, while all other Higgs doublets and all Higgs triplets are kept heavy, with the aid of the economical missing-doublet mechanism found in the field-theoretical version of flipped SU(5). The solution predicts that second-generation charge -1/3 quarks and charged leptons are much lighter than those in the third g…
We revisit the long-standing problem of supersymmetric grand unified theory (GUT), the doublet-triplet splitting problem. We discuss whether symmetry which controls the μ term in the minimal supersymmetric standard model is compatible with GUT. We find that the symmetry must be broken at the GUT scale. A similar argument also shows that the R symmetry, which is important for low energy supersymmetry, must be broken down to a Z2R symmetry at the GUT scale. We propose a new prescription to achieve the doublet-triplet splitting by symmetry. There, the symmetry which controls the μ term is spontan…
Matter-Higgs unification in string-inspired supersymmetric Grand Unified Theories predicts the existence of colored states in the Higgs multiplets and calls for two extra generations of Higgs-like fields ('unhiggses'). If these states are present near the TeV scale, gauge-coupling unification points to the existence of two distinct scales, 10^15 GeV where right-handed neutrinos and a Pati-Salam symmetry appear, and 10^18 GeV where complete unification is achieved. Baryon-number conservation, while not guaranteed, can naturally emerge from an underlying flavor symmetry. Collider signatures and …
We consider the minimum extension of the SM denominated 2HDM-III, in which,it new coupling constants to the new Higgs field in the Lagrangian of Yukawa are added furtheremore a Majorana mass in generated via See-Saw mechanism SSM-I thus, the effective masses of the Dirac and Majorana neutrinos will be sensitive to te VEV of Higgs doublets and to the structure of the Yukawa constants. Then we consider the MSS-III,in which a $Z_{2}$ symmetry is imposed to Lagrangian 2HDM-III to attach a doublet to the particles of the SM, and the other doublet to the triplet of fermions included in this mechanis…
We study collider signatures of electroweak baryogenesis in the two Higgs doublet model and the minimal supersymmetric standard model. It is found that the trilinear coupling of the lightest Higgs boson receives large quantum corrections if the electroweak phase transition is strongly first order for successful baryogenesis. In the two Higgs doublet model, the magnitude of the deviation from the standard model value is shown to be larger than 10 percent. Such a deviation can be detected at a future electron-positron linear collider.
We construct a supersymmetric grand unified model in which a dynamical symmetry breaking of SU(5)$_{GUT}$ generates large masses for color-triplet Higgs multiplets while keeping SU(2)$_L$-doublet Higgs multiplets naturally light. The vanishing masses for the Higgs doublets are guaranteed by the Peccei-Quinn symmetry. We also show that the Peccei-Quinn symmetry suppresses the dangerous dimension 5 operators for the nucleon decay.
Assuming two Higgs doublet model (2HDM) at SM-like scenario as the theoretical framework, this study addresses the question of observability of heavy neutral CP-even and CP-odd Higgs bosons $H$ and $A$ at a linear collider operating at $\sqrt{s}=1$ TeV. The signal production channel is $e^- e^+ \rightarrow A H \rightarrow ZHH$ with subsequent leptonic decay of the $Z$ boson and Higgs bosons decays into $b$ quark pairs. Therefore, to be specific, type-I 2HDM is used to allow dominant Higgs boson decay to b-quark pairs below the top quark pair production threshold. Two benchmark points with mass…
We consider a supersymmetric hypercolor gauge theory with six flavors of quarks interacting strongly at the grand unification scale. This model solves the most serious problem -- doublet-triplet splitting in the grand unified theories. We also show that the dangerous dimension-five operators for nucleon decays are suppressed simultaneously, which makes our model yet more attractive.
We calculate the one--loop contribution from the $H^+ W^- Z$ coupling to the static electromagnetic properties of the W boson. Although this coupling is absent at the tree--level in all Higgs--doublet models, it can be induced at this order in models including Higgs--triplet representations. It is found that the $H^+ W^- Z$ contribution can be as important as those arising from other couplings including Higgs bosons, such as the standard model coupling WWH or the two--Higgs--doublet model couplings $H^+ W^- ϕ^0$ and $W W ϕ^0$, with $ϕ^0=h$, $H$ and $A$.
We have considered a model, originally proposed by Ma and Wegman, where the mixing pattern in neutrino sector is explained with three Higgs doublets, six Higgs triplets and $A_4$ symmetry. The mixing pattern is explained with the help of vacuum expectation values (VEVs) of the above mentioned doublets and triplets. In order to study about the VEVs of the scalar fields, we construct the full invariant scalar potential of this model. After minimizing this scalar potential, we have found that two Higgs triplets can acquire zero VEVs. In order to generate non-zero VEVs to all the six Higgs triplet…
