The Large Hadron Collider (LHC) has measured the Higgs boson couplings with the heavier particles of the Standard Model (SM), and they seem to lay on a single line as function of the particle mass, as predicted in the SM. However a complete test of this property must involve the lighter generations, and the coming measurements at LHC, or future colliders, may reveal hidden patterns associated with physics beyond the SM. In renormalizable multi-Higgs models, the Higgs-fermion couplings could still be linear, but they could lay on multiple lines. Then, the angle subtended by these lines, with respect to the SM line, can be used to characterize different models, as it is shown here for the Two-Higgs doublet Model (2HDM). Models where fermion masses arise from higher-dimensional operators, may also result in large deviations from the SM values for the Higgs couplings, which would show an irregular pattern as a function of the fermion masses. In the case of neutrino masses, when they arise from the see-saw mechanism, one finds that the Higgs Yukawa couplings will show a non-linear mass relation.
We study the deviation of yukawa coupling in the gauge-Higgs unification scenario from the Standard Model one. Applying the obtained results to the tau and bottom yukawa couplings, we numerically calculate the signal strength of $gg \to H \to \bar b b, \bar τ τ$in the gauge-Higgs unification.
We study the deviation of yukawa coupling in the gauge-Higgs unification scenario from the Standard Model one. Taking into account the brane mass terms necessary for generating the flavor mixing and removing the exotic massless fermions, we derive an analytic formula determining the KK mass spectrum and yukawa coupling. Applying the obtained results to the tau and bottom yukawa couplings, we numerically calculate the ratio of the yukawa couplings in the gauge-Higgs unification and in the Standard Model.
We investigate the inclusive production of the Higgs boson with a heavy quark pair, $t {\bar t}$ or $b {\bar b}$, in e^+e^- collisions at high energy. The ${\cal O}(α_s)$ QCD corrections are included.
The wave functions and Yukawa couplings of the top and bottom quarks in the SO(5) x U(1) gauge-Higgs unification model are determined. The result is summarized in the effective interactions for \hat θ_H(x) = θ_H + H(x)/f_H where θ_H is the Wilson line phase and H(x) is the 4D Higgs field. The Yukawa, WWH and ZZH couplings vanish at θ_H = \onehalf π. There emerges the possibility that the Higgs particle becomes stable.
Extensions of the MSSM generically feature gauge singlet Higgs bosons. These singlet Higgs bosons have tan(beta)-enhanced Yukawa couplings to down-type quarks and leptons at the one-loop level. We present an effective Lagrangian incorporating these Yukawa couplings and use it to study their effect on singlet Higgs boson phenomenology within both the mnSSM and NMSSM. It is found that the loop-induced couplings represent an appreciable effect for the singlet pseudoscalar in particular, and may dominate its decay modes in some regions of parameter space.
We study a possibility of a measurement of muon Yukawa couplings in s-channel Higgs boson production at a muon collider with transversely polarized beams. We investigate sensitivity to the relative size of the CP-odd and CP-even muon Yukawa couplings. Provided the event rate observed justify the operation of the $μ^+μ^-$ Higgs boson factory, we have found that polarization degree 40% is sufficient to resolve the CP nature of a single resonance as well as disentangle it from two overlapping CP conserving resonances.
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…
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…
Three-loop renormalization group equations for the Higgs self-coupling and Higgs mass parameter are recalculated in the case of complex Yukawa matrices, which encompass general flavour structure of the Standard Model. In addition, the anomalous dimensions both for the quantum Higgs field and its vacuum expectation value are presented in the $\overline{MS}$-scheme. A numerical study of the latter quantities is carried out for a certain set of initial parameters.
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…
We analytically compute two-loop Yukawa corrections to Higgs boson pair production in the high-energy limit. Such corrections are generated by an exchange of a Higgs boson between the virtual top quark lines. We propose two approaches to obtain expansions of the massive two-loop box integrals and show that precise results are obtained for transverse momenta of the Higgs bosons above about 150 GeV. We discuss in detail the computation of all 140 master integrals and present analytic results.
Singlet Higgs bosons present in extensions of the MSSM can have sizable Yukawa couplings to the b quark and the tau lepton for large values of tan(beta) at the 1-loop level. We present an effective Lagrangian which incorporates these tan(beta)-enhanced Yukawa couplings and which enables us to study their effect on singlet Higgs-boson phenomenology within the context of both the mnSSM and the NMSSM. In particular, we find that the loop-induced coupling can be a significant effect for the singlet pseudoscalar, and may dominate its decay modes. Further implications of the tan(beta)-enhanced Yukaw…
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 consider the possibility that the Yukawa couplings depend on the Higgs field, with the motivation of generating the fermion mass hierarchy through appropriate powers of the Higgs vacuum expectation value. This leads to drastic modifications of the Higgs branching ratios, new Higgs contributions to various flavor-violating processes, and observable rates for the top quark decay t-> hc. The underlying flavor dynamics must necessarily appear at the TeV scale and is within the reach of the LHC.
We present a non-trivial correlation between the enhancement of the Higgs-fermion couplings and the Higgs pair production cross section in two Higgs doublet models with a flavour symmetry. This symmetry suppresses flavour-changing neutral couplings of the Higgs boson and allows for a partial explanation of the hierarchy in the Yukawa sector. After taking into account the constraints from electroweak precision measurements, Higgs coupling strength measurements, and unitarity and perturbativity bounds, we identify an interesting region of parameter space leading to enhanced Yukawa couplings as w…
We compute the leading logarithmic radiative corrections to the lightest Higgs mass in the NMSSM involving the electroweak gauge couplings and in the NMSSM specific Yukawa couplings lambda and kappa (including all mixed combinations), which are induced by chargino, neutralino and Higgs boson loops. The effect of the NMSSM specific Yukawa couplings lambda and kappa is to increase the upper bound on the lightest Higgs mass by up to ~2 GeV, but they can also decrease the lightest Higgs mass by up to ~-20 GeV.
A feasibility study of the measurement of the top-Higgs Yukawa coupling at a future linear e+e- collider operating at sqrt(s)=800 GeV is presented. As compared to previous existing studies, much effort has been put in a ``realistic simulation'' by including irreducible+reducible backgrounds, realistic detector effects and reconstruction procedures and finally, a multivariate analysis. Both hadronic and semileptonic decay channels have been considered.
We investigate a model that the Yukawa coupling form is constructed by two kinds of matrix (M_0 and M_1). For example, in the SO(10) GUT model, M_0 and M_1 are Yukawa couplings generated by the 10 and 126 Higgs scalars. We study how this model can give the observed mass and mixings of quarks and leptons. Parameter fitting is fully scanned by assuming all the input data to be normally distributed around the center value.
Higgs production from gluon fusion is sensitive to the properties of heavy colored fermions and to the Yukawa couplings, (Y_F M_F)/v, of these particles to the Higgs boson. We compute the two--loop, ${\cal O}((Y_F M_F)^3/v^3)$ contributions of new high mass fermions to Higgs production. In the Standard Model, these contributions are part of the well-known electroweak corrections and are negligible. However, in models with TeV scale fermions, such as top partner or composite models, Yukawa corrections are enhanced by effects of ${\cal O}((Y_F M_F)^3/v^3)$ and are potentially significant due to …
Understanding the mechanism of electroweak symmetry breaking and the origin of boson and fermion masses is among the most pressing questions raised in contemporary particle physics. If these issues involve one (several) Higgs boson(s), a precise measurement of all its (their) properties will be of prime importance. Among those, the Higgs coupling to matter fermions (the Yukawa coupling). At a Linear Collider, the process e+e- -> ttH will allow in principle a direct measurement of the top-Higgs Yukawa coupling. We present a realistic feasibility study of the measurement in the context of the TE…
We find that the one-loop correction to the ratio of Yukawa coupling and gauge coupling in the gauge-Higgs unification, "gauge-Yukawa universality violation", is finite and calculable in any space-time dimension. Applying this result to the ratio of top quark and W-boson masses, we show that the order one correction required to generate a viable top quark mass is indeed possible if the fermion embedding top quark belongs to the large dimensional representation of the gauge group and a vacuum expectation value of Higgs scalar field is very small comparing to the compactification scale.
We implement a comprehensive and detailed study of the alignment of Yukawa couplings in the so-called Higgs basis taking the framework of general two Higgs doublet models (2HDMs). We clarify the model input parameters and derive the Yukawa couplings considering the two types of CP-violating sources: one from the Higgs potential and the other from the three complex alignment parameters $ζ_{f=u,d,e}$. We consider the theoretical constraints from the perturbative unitarity and for the Higgs potential to be bounded from below as well as the experimental ones from electroweak precision observables.…
In this talk we assume SO(10) boundary conditions at the GUT scale, including unification for the third generation Yukawa couplings $λ_t = λ_b = λ_τ$. We find that this assumption is only consistent with the low energy data in a narrow region of soft SUSY breaking parameter space. We discuss the consequences of this result for Higgs and SUSY searches.
We show that the normalized Higgs production $p_T$ and $y_h$ distributions are sensitive probes of Higgs couplings to light quarks. For up and/or down quark Yukawa couplings comparable to the SM $b$ quark Yukawa the $\bar u u$ or $\bar d d$ fusion production of the Higgs could lead to appreciable softer $p_T$ distribution than in the SM. The rapidity distribution, on the other hand, becomes more forward. We find that, owing partially to a downward fluctuation, one can derive competitive bounds on the two couplings using ATLAS measurements of normalized $p_T$ distribution at 8\,TeV. With 300 fb…
We study the implications of non-standard Higgs Yukawa couplings to light quarks on Higgs-portal dark matter phenomenology. Saturating the present experimental bounds on up-quark, down-quark, or strange-quark Yukawa couplings, the predicted direct dark matter detection scattering rate can increase by up to four orders of magnitude. The effect on the dark matter annihilation cross section, on the other hand, is subleading unless the dark matter is very light -- a scenario that is already excluded by measurements of the Higgs invisible decay width. We investigate the expected size of corrections…
We use $t, b, τ$ Yukawa unification to constrain SUSY parameter space. We find a narrow region survives for $μ> 0$ (suggested by \bsgam and the anomalous magnetic moment of the muon) with $A_0 \sim - 1.9 m_{16}$, $m_{10} \sim 1.4 m_{16}$, $m_{16} \sim 1200 -3000$ \gev and $μ, M_{1/2} \sim 100 - 500$ \gev. Demanding Yukawa unification thus makes definite predictions for Higgs and sparticle masses.
In the scenarios with heavy top squarks, mass parameters of the Higgs field must be fine-tuned due to a large logarithmic correction to the soft scalar mass. We consider a new possibility that the top Yukawa coupling is small above TeV scale. The large top mass is induced from strong Yukawa interaction of the Higgs with another gauge sector, in which supersymmetry breaking parameters are given to be small. Then it is found that the logarithmic correction to the Higgs soft scalar mass is suppressed in spite of the strong coupling and the fine-tuning is ameliorated. We propose an explicit model …
The top-Yukawa-coupling enhanced two-loop corrections to the charged Higgs-boson mass in the real MSSM are presented. The contributing two-loop self-energies are calculated in the Feynman- diagrammatic approach in the gaugeless limit with vanishing external momentum and bottom mass, within a renormalization scheme comprising on-shell and $\overline{\text{DR}}$ conditions. Numerical results illustrate the effect of the $\mathcal{O}{(α_t^2)}$ contributions and the importance of the two-loop corrections to the mass of the charged Higgs bosons.
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.
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…
We discuss ways to probe t-b-tau Yukawa coupling unification condition at the Energy and Intensity frontiers. We consider non-universal soft supersymmetry breaking mass terms for gauginos related by the SO(10) grand unified theory (GUT). We have previously shown that t-b-tau Yukawa coupling unification prefers a mass of around 125 GeV for the Standard Model-like Higgs boson with all colored sparticle masses above 3 TeV. The well-known MSSM parameter tan(beta) is about 47-48 and neutralino-stau coannihilation yields the desired relic dark matter density.
We discuss the Yukawa couplings in 6D gauge-Higgs unification models on $T^2/Z_N$ in the presence of magnetic fluxes. We provide general formulae for them, and numerically evaluate their magnitude in a specific model on $T^2/Z_3$. Thanks to the nontrivial profiles of the zero-mode wave functions, the top quark Yukawa coupling can be reproduced without introducing a large representation of the gauge group for matter fields. However, it is difficult to realize small Yukawa couplings only by the magnetic fluxes and the Wilson-line phases because of the complicated structure of the mode functions …
We investigate the leading one-loop Yukawa corrections to the process pp-> b anti-b H in the Standard Model. We find that the next-to-leading order correction to the cross section is small about -4% if the Higgs mass is 120GeV. However, the appearance of leading Landau singularity when $M_H > 2M_W$ can lead to a large correction at the next-to-next-to-leading order level for a Higgs mass around 160GeV.
The framework of Higgs-dependent Yukawa couplings allows one to eliminate small couplings from the Standard Model, which can be tested at the LHC. In this work, I study the conditions for CP violation to occur in such models. I identify a class of weak basis invariants controlling CP violation. The invariant measure of CP violation is found to be more than 10 orders of magnitude greater than that in the Standard Model, which can be sufficient for successful electroweak baryogenesis.
We extend the already existing two-loop calculation of the effective bottom-Yukawa coupling in the MSSM. In addition to the resummation of the dominant corrections for large values of tg$β$, we include the subleading terms related to the trilinear Higgs coupling $A_b$ and contributions induced by the electroweak gauge couplings. This calculation has been extended to the NNLO corrections to the MSSM strange-Yukawa coupling. Our analysis leads to residual theoretical uncertainties of the effective Yukawa couplings at the per-cent level.
We explore the Higgs and sparticle spectroscopy of supersymmetric SU(4)_c x SU(2)_L x SU(2)_R models in which the three MSSM gauge couplings and third family (t-b-tau) Yukawa couplings are all unified at M_GUT. This class of models can be obtained via compactification of a higher dimensional theory. Allowing for opposite sign gaugino masses and varying m_t within 1 sigma of its current central value yields a variety of gauge-Yukawa unification as well as WMAP compatible neutralino dark matter solutions. They include mixed bino-Higgsino dark matter, stau and gluino coannihilation scenarios, and…
We calculate the Yukawa corrections of order $O(α_{ew}m_{t(b)}^{2}/m_{W}^{2})$ to charged Higgs boson production in association with a top quark at the Tevatron and the LHC. The corrections are not very sensitive to the mass of the charged Higgs boson and can exceed -20% for low values of $\tanβ$, where the contribution of the top quark is large, and high values of $\tanβ$ where the contribution of the bottom quark becomes large. These Yukawa corrections could be significant for charged Higgs boson discovery searches based on this production process, particularly at the LHC where the cross sec…
In this paper, we investigate the decay of Higgs boson to $h_c$ plus a photon in the NRQCD theoretical framework. Comparing with the Higgs decay to $J/ψ$ plus a photon channel, this process has not indirect contribution, can be used to detect the Yukawa coupling of Higgs and charm quarks. The results show that the decay branch ratio of this process is about $10^{-8}$. If we takes into account the $10^{-3}$ efficiency in the $h_c$ detection, no events will be available even in the case of $30ab^{-1}$ luminosity at FCC-pp with 100 TeV center of mass energy. However, if the detection efficiency o…
Considering the large value of the top Yukawa coupling, we investigate the leading one-loop Yukawa electroweak corrections that can be induced by the top quark in a process such as Higgs production in association with a tagged bottom anti-bottom pair at the LHC. At NLO these contributions are found to be small at the LHC both for the total cross section and for the distributions. In the limit of vanishing bottom Yukawa coupling where the LO contribution vanishes, the process can still be induced at one-loop through the top quark transition. Though this contribution which can be counted as part…
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…
I present results for the two-loop self-energy functions for neutral and charged Higgs scalar bosons in minimal supersymmetry. The contributions given here include all terms involving the QCD coupling, and those following from Feynman diagrams involving Yukawa couplings and scalar interactions that do not vanish as the electroweak gauge couplings are turned off. The impact of these contributions on the computation of pole masses of the neutral and charged Higgs scalar bosons is studied in a few examples.
Results for the leading two-loop corrections of $\mathcal{O}{\left(α_t^2\right)}$ from the Yukawa sector to the Higgs-boson masses of the MSSM with complex parameters are presented. The corresponding self-energies and their renormalization have been obtained in a Feynman-diagrammatic approach. A numerical analysis of the new contributions is performed for the mass of the lightest Higgs boson, supplemented by the full one-loop result and the $\mathcal{O}{\left(α_t α_s\right)}$ terms including complex phases. In the limit of the real MSSM a previous result is confirmed.
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…
Extra vector-like matter with both electroweak-singlet masses and large Yukawa couplings can significantly raise the lightest Higgs boson mass in supersymmetry through radiative corrections. I consider models of this type that involve a large Yukawa coupling between weak isotriplet and isodoublet chiral supermultiplets. The particle content can be completed to provide perturbative gauge coupling unification, in several different ways. The impact on precision electroweak observables is shown to be acceptably small, even if the new particles are as light as the current experimental bounds of ord…
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…
We review some properties of Bilinear R-Parity Violating models: simple extensions of the Minimal Supersymmetric Standard Model motivated by spontaneous breaking of R-Parity. We concentrate on the relaxation of the bounds on the charged Higgs mass imposed by the measurement of B(b -> s gamma), the effect on the mass of the lightest neutral Higgs boson, the radiative breaking of the electroweak symmetry, the unification of bottom and tau Yukawa couplings, and the relation of these phenomena to the radiatively generated tau-neutrino mass.
Results for the two-loop corrections to the Higgs-boson masses of the MSSM with complex parameters of $\mathcal{O}{\left(α_t^2+α_tα_b+α_b^2\right)}$ from the Yukawa sector in the gauge-less limit are presented. The corresponding self-energies and their renormalization have been obtained in the Feynman-diagrammatic approach. The impact of the new contributions on the Higgs spectrum is investigated. Furthermore, a comparison with an existing result in the limit of the MSSM with real parameters is carried out. The new results will be included in the public code $\texttt{FeynHiggs}$.
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' $q\bar q,gg\to \bar t b H^++c. c.$ produ…
If one removes any \emph{ad hoc} symmetry assumptions, the general two Higgs doublet model should have additional Yukawa interactions independent from fermion mass generation, in general involving flavor changing neutral Higgs couplings. These extra couplings can affect the discovered Higgs boson $h$ through fermion loop contributions. We calculate the renormalized $hZZ$ coupling at one-loop level %by on-shell and minimal subtraction scheme, and evaluate the dependence on heavy Higgs boson mass and extra Yukawa coupling $ρ_{tt}$. Precision measurements at future colliders can explore the param…
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.
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 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…
We investigate the inclusive production of a Higgs boson with a pair of heavy quarks (t-tbar b-bbar), in e^+e^- collisions at high energies, sqrt(s)=500 GeV and sqrt(s)=1 TeV. We consider both the Standard Model and the supersymmetric case. In both cases O(alpha_s) QCD corrections are included. The associated production of a Higgs boson with a t-tbar pair is extremely sensitive to the top-Higgs Yukawa coupling and may allow the precision measurement of this coupling. In some regions of the supersymmetric parameter space the associated production of a Higgs boson with a b-bbar pair receives lar…
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.
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 …
