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A minimal SO(10) Higgs structure involving a single adjoint field along with spinors, vectors and singlets has been shown to break the SO(10) gauge symmetry to the standard model while stabilizing the F-flat directions and solving the…
We study an SU(2) supersymmetric gauge model in a framework of gauge-Higgs unification. Multi-Higgs spectrum appears in the model at low energy. We develop a useful perturbative approximation scheme for evaluating effective potential to…
Scale invariance supplemented by the requirement of the absence of new heavy particles may play an important role in addressing the hierarchy problem. We discuss how the Standard Model may become scale invariant at the quantum level above a…
Gauge singlet extensions of the Standard Model (SM) scalar sector may help remedy its theoretical and phenomenological shortcomings while solving outstanding problems in cosmology. Depending on the symmetries of the scalar potential, such…
We study the Higgs-boson mass spectrum of a classical scale-invariant realization of the two-Higgs-doublet model (SI-2HDM). The classical scale symmetry of the theory is explicitly broken by quantum loop effects due to gauge interactions,…
We study the scalar sector of the most general multi Higgs doublet model satisfying explicitly an exact symmetry. We prove that such a model will exhibit decoupling if and only if the vacuum also satisfies the same symmetry. This general…
In this thesis, we investigate the implications of the LHC Higgs data on different BSM scenarios. Since the data seem to agree with the SM expectations, any nonstandard couplings will be strongly constrained. First we investigate, in a…
Because of the existence of cubic scalar couplings, there are in general nondecoupling effects at tree level in the scalar sector of any theory with two or more very different mass scales. We show this explicitly in the minimal…
The minimal extension of the scalar sector of the standard model contains an additional real scalar field with no gauge quantum numbers. Such a field does not couple to the quarks and leptons directly but rather through its mixing with the…
A large class of two- and three-Higgs-doublet models with discrete symmetries has been employed in the literature to address various aspects of flavor physics. We analyse how the precision measurement of the Higgs to diphoton signal…
The quadratic divergences in the scalar sector of the standard model are considered. Since the divergences are present also in the unbroken theory, a natural scale for the divergence formula is proposed to be at the scale of new physics.…
Simple scalar-singlet extensions of the Standard Model with a (spontaneously broken) $Z_2$ symmetry allow for a strong first order electroweak phase transition, as sought in order to realize electroweak baryogenesis. However they…
In general electroweak models with weakly coupled (and otherwise arbitrary) Higgs sector there always exists in the spectrum a scalar state with mass controlled by the electroweak scale. A new and simple recipe to compute an analytical…
We present the first complete next-to-next-to-leading order analysis of the Standard Model Higgs potential. We computed the two-loop QCD and Yukawa corrections to the relation between the Higgs quartic coupling (lambda) and the Higgs mass…
We perform a phenomenological study of the scalar sector of two models that generate neutrino mass at the three-loop level and contain viable dark matter candidates. Both models contain a charged singlet scalar and a larger scalar multiplet…
We investigate the standard model (SM) with the extension of a charged scalar having fractional electromagnetic charge of $-1/3$ unit and with lepton and baryon number violating couplings at tree level. Without directly taking part in the…
We analyse effective potential around the electroweak (EW) scale in the Standard Model extended with a heavy scalar doublet. We show that the additional scalars can have a strong impact on vacuum stability. Although the additional heavy…
We investigate Planck scale boundary conditions on the Higgs sector of the standard model with a gauge singlet scalar dark matter. We will find that vanishing self-coupling and Veltman condition at the Planck scale are realized with the 126…
In spite of its many successes, the Standard Model makes many empirical assumptions in the Higgs and fermion sectors for which a deeper theoretical basis is sought. Starting from the usual gauge symmetry $u(1) \times su(2) \times su(3)$…
Simplified models provide a useful tool to conduct the search and exploration of physics beyond the Standard Model in a model-independent fashion. In this work we consider the complementarity of indirect searches for new physics in Higgs…