Gautam Bhattacharyya

Power law scaling in universal extra dimension scenarios

We study the power law running of gauge, Yukawa and quartic scalar couplings in the universal extra dimension scenario where the extra dimension is accessed by all the standard model fields. After compactifying on an S1/Z2 orbifold, we compute one-loop contributions of the relevant Kaluza-Klein (KK) towers to the above couplings up to a cutoff scale �. Beyond the scale of inverse radius, once the KK states are excited, these couplings exhibit power law dependence on �. As a result of faster running, the gauge couplings tend to unify at a relatively low scale, and we choose our cutoff also around that scale. For example, for a radius R ∼ 1 TeV 1 , the cutoff is around 30 TeV. We then examine the consequences of power law running on the triviality and vacuum stability bounds on the Higgs mass. We also comment that the supersymmetric extension of the scenario requires R 1 to be larger than ∼ 10 10 GeV in order that the gauge couplings remain perturbative up to the scale where they tend to unify.

Common origin of fermion mixing and geometrical CP violation, and its test through Higgs physics at the LHC

We construct for the first time a flavor model, based on the smallest discrete symmetry Δ(27) that implements spontaneous CP violation with a complex phase of geometric origin, which can actually reproduce all quark masses and mixing data. We show that its scalar sector has exotic properties that can be tested at the LHC.

R-parity violating trilinear couplings and recent neutrino data

The nontrivial structure of the neutrino mass matrix, suggested by the recent Super-Kamiokande results and data from other neutrino experiments, can be reproduced in

Scalar sector properties of two-Higgs-doublet models with a global U(1) symmetry

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A pedagogical review of electroweak symmetry breaking scenarios

-parity-violating supersymmetric theories. This requires sets of products of

Feasibility of light scalars in a class of two-Higgs-doublet models and their decay signatures

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Modified Higgs couplings and unitarity violation

-parity-violating trilinear couplings to take appropriately chosen values. It is shown that the existing constraints on these couplings are satisfied by these choices.

Exotic Higgs boson decay modes as a harbinger of

A bstractWe analyze the scalar sector properties of a general class of two-Higgs-doublet models which has a global U(1) symmetry in the quartic terms. We find constraints on the parameters of the potential from the considerations of unitarity of scattering amplitudes, the global stability of the potential and the ρ-parameter. We concentrate on the spectrum of the non-standard scalar masses in the decoupling limit which is preferred by the Higgs data at the LHC. We exhibit charged-Higgs induced contributions to the diphoton decay width of the 125 GeV Higgs boson and its correlation with the corresponding Zγ width.

S_3

We review different avenues of electroweak symmetry breaking explored over the years. This constitutes a timely exercise as the worlds largest and the highest energy particle accelerator, namely, the Large Hadron Collider (LHC) at CERN near Geneva, has started running whose primary mission is to find the Higgs or some phenomena that mimic the effects of the Higgs, i.e. to unravel the mysteries of electroweak phase transition. In the beginning, we discuss the Standard Model Higgs mechanism. After that we review the Higgs sector of the minimal supersymmetric Standard Model. Then we take up three relatively recent ideas: little Higgs, gauge–Higgs unification and Higgsless scenarios. For the latter three cases, we first present the basic ideas and restrict our illustration to some instructive toy models to provide an intuitive feel of the underlying dynamics, and then discuss, for each of the three cases, how more realistic scenarios are constructed and how to decipher their experimental signatures. Wherever possible, we provide pedagogical details, which beginners might find useful.

flavor symmetry

We demonstrate that light charged and extra neutral scalars in the (100-200) GeV mass range pass the potentially dangerous flavor constraints in a particular class of two-Higgs-doublet model which has appropriately suppressed flavor-changing neutral currents at tree level. We study their decay branching ratios into various fermionic final states and comment on the possibility of their detection in the collider experiments. We also remark on how their trademark decay signatures can be used to discriminate them from the light nonstandard scalars predicted in other two-Higgs-doublet models.