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We consider the possibility to observationally differentiate the Standard Model (SM) Higgs driven inflation with non-minimal couplingto gravity from other variants of SM Higgs inflation based on the scalar field theories with non-canonical…
In general, there can be mass differences among scalar bosons of the Higgs triplet field with the hypercharge of Y=1. In the Higgs triplet model, when the vacuum expectation value $v_\Delta$ of the triplet field is much smaller than that…
The recent discovery of the Higgs-like particle at around 126 GeV has given us a big hint towards the origin of the Higgs potential. Especially the running quartic coupling vanishes near the Planck scale, which indicates a possible link…
I present comprehensive analyses of the viable parameter regions of the Standard Model of particle physics and two of its extensions: the Standard Model with four fermion generations and the Two-Higgs-Doublets model of type II. Applying…
The standard model is a remarkably consistent and complete quantum field theory but its coupling to gravity and the Higgs field remain problematic, as reflected in the cosmological constant problem, the Weyl anomaly, and the hierarchy…
We show that in the absence of trilinear terms in the scalar potential of Georgi-Machacek model, heavy charged scalars do not necessarily decouple from the $h \to \gamma \gamma$ decay amplitude. In such scenarios, measurement of the Higgs…
We consider the conditions for the validity of a two-Higgs doublet model at high energy scales, together with all other low- and high-energy constraints. The constraints on the parameter space at low energy, including the measured value of…
The observed Higgs boson mass poses a new puzzle in addition to the longstanding problem of the origin of the electroweak scale; the shallowness of the Higgs potential. The Higgs quartic coupling even seems to vanish at around the Planck…
If the Standard Model is valid up to very high energies it is known that the Higgs potential can develop a local minimum at field values around $10^{15}-10^{17}$ GeV, for a narrow band of values of the top quark and Higgs masses. We show…
If the gauge fields of the Standard Model propagate in TeV-size extra dimensions, they rapidly become strongly coupled and can form scalar bound states of quarks and leptons. If the quarks and leptons of the third generation propagate in 6…
We investigate the vacuum stability in a scale invariant local $U(1)_\chi$ model with vanishing scalar potential at the Planck scale. We find that it is impossible to realize the Higgs mass of 125\,GeV while keeping the Higgs quartic…
Supersymmetric extensions of the Standard Model have been in vogue for over half a century. They have many interesting theoretical properties like calculability, absence of quadratic divergences, and phenomenologically impactful features…
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…
Both the ATLAS and CMS experiments at the LHC have reported the observation of the particle of mass around 125GeV which is consistent to the Standard Model (SM) Higgs boson, but with an excess of events beyond the SM expectation in the…
In the Higgs portal framework, the Higgs field generally mixes with the Standard Model singlet leading to the existence of two states, one of which is identified with the 125 GeV scalar observed at the LHC. In this work, we analyse direct…
An extension of the Standard Model with three right-handed neutrinos and a simple invisible axion model can account for all experimentally confirmed signals of new physics (neutrino oscillations, dark matter and baryon asymmetry) in…
We study the parametrization and gauge dependences in the Higgs field coupled to gravity in the context of asymptotic safety. We use the exponential parametrization to derive the fixed points for the cosmological constant, Planck mass,…
Sogami recently proposed the new idea to express Higgs particle as a kind of gauge particle by prescribing the generalized covariant derivative with gauge and Higgs fields operating on quark and lepton fields. The field strengths for both…
It is pointed out that mixing effects in the CP-even scalar sector of the NMSSM can give 6-8 GeV correction to the SM-like Higgs mass in moderate or large $\tan\beta$ regions with a small value of the singlet-higgs-higgs superfields…
Imposing the theoretical constraints from vacuum stability, unitarity and perturbativity as well as the experimental constraints from the electroweak precision data, flavor observables and the non-observation of additional Higgs at…