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A two Higgs doublet model with special Yukawa interactions for the top quark and a softly broken discrete symmetry in the Higgs potential is proposed. In this model, the top quark is much heavier than the other quarks and leptons because it…
In Quantum Field Theory models of electro-weak interactions with spontaneously broken gauge invariance, renormalizability limits to four the degree of the Higgs potential, whose minima determine the possible vacuum states in tree…
We perform in the type II seesaw setting, a detailed study of the dynamical features of the corresponding general renormalizable doublet/triplet Higgs potential that depends on five dimensionless couplings and two mass parameters after…
We analyze a model for the Higgs sector with two scalar doublets and a $Z_2$ symmetry that is manifest in the Yukawa sector but broken in the potential. Thus, one of the doublets breaks the electroweak symmetry and has tree-level Yukawa…
We study the "lepton-specific" two Higgs doublet model, in which one doublet Phi_l gives mass to charged leptons and the other Phi_q gives mass to both up- and down-type quarks. We examine the existing experimental constraints on the…
Composite Higgs models provide an attractive solution to the hierarchy problem. However, many realistic models suffer from tuning problems in the Higgs potential. There are often large contributions from the UV dynamics of the composite…
We discuss the features of a two-Higgs doublet model exhibiting a two stage phase transition. At finite temperatures electric charge violating stationary points are developed. In conjunction with {\em CP} violation in the Higgs or the…
We study several aspects of supersymmetric models with a $U(1)_R$ symmetry where the Higgs doublet is identified with the superpartner of a lepton. We derive new, stronger bounds on the gaugino masses based on current measurements, and also…
We study the constraints on the doublet left-right symmetric model (DLRSM) arising due to the Higgs data. The $SU(2)_L$ symmetry of this model is broken by three vacuum expectation values, $\kappa_1$, $\kappa_2$, and $v_L$. Most studies of…
I present a model with two scalar doublets and a softly broken $\ztwo$ symmetry, where only one of the doublets gets a vacuum expectation value and couples to fermions at tree-level. The softly broken $\ztwo$ symmetry leads to interesting…
New models have recently been proposed in which a second Higgs doublet couples only to the lepton doublets and right-handed neutrinos, yielding Dirac neutrino masses. The vacuum value of this second "nu-Higgs" doublet is made very small by…
The measurement of the triple Higgs coupling is one of the main tasks of the (HL-)LHC and future lepton colliders. Similarly, triple Higgs couplings involving BSM Higgs bosons are of high interest. Within the framework of Two Higgs Doublet…
We investigate the phenomenology of a model based on the $SU(3)_c\times SU(3)_L\times U(1)_X$ gauge theory, the so-called 331 model. In particular, we focus on the Higgs sector of the model which is composed of three $SU(3)_L$ triplet Higgs…
We consider the Two Higgs Doublet Model (2HDM) of type III which leads to Flavour Changing Neutral Currents (FCNC) at tree level. In the framework of this model we can use an appropriate form of the Yukawa Lagrangian that makes the type II…
We investigate an extension of the Minimal Supersymmetric Standard Model (MSSM) containing a $SU(2)$ Higgs triplet of zero hypercharge and a gauge singlet. We focus on a scenario of this model which allows a light pseudoscalar and/or a…
We study the extension of the Standard Model (SM) by introducing a scalar multiplet with arbitrary isospin $J$ and hypercharge $Y$. We explicitly consider various possible values of the weak isospin $J$, up to and including $J=7/2$. The…
The minimal supersymmetric standard model, and extensions, have stringent upper bounds on the mass of the lightest Higgs boson if perturbativity up to the Planck scale is assumed. We argue that these bounds are softened tremendously if the…
We update phenomenological constraints on a Two Higgs Doublet Model with lepton flavour non-conserving Yukawa couplings. We review that $\tan \beta$ is ambiguous in such "Type III" models, and define it from the $\tau$ Yukawa coupling. The…
Discovering CP-violating effects in the Higgs sector would constitute an indisputable sign of physics beyond the Standard Model. We derive constraints on the CP-violating Higgs-boson couplings to top and bottom quarks as well as to tau…
We analyze the ultraviolet stability of the Higgs mass in recently proposed Kaluza-Klein models compactified on S_1/Z_2 or S_1/(Z_2\times Z_2'), both at the field theory and string theory level. Fayet-Iliopoulos terms of U(1) hypercharge…