We construct a model based on the electroweak gauge group SU(2)L×SU(2)R×U(1)B-L augmented by an S3 symmetry. We assign nontrivial S3 transformation properties to the quarks, and consequently we need two scalar bidoublets. Despite the extra bidoublet, we have only six Yukawa couplings thanks to the discrete symmetry. Diagonalization of the quark mass matrices shows that at the leading order only th

In a truly model-independent approach, we reexamine a minimal extension of the Standard Model (SM) through the introduction of an additional U(1) symmetry leading to a new neutral gauge boson (Z′), allowing its kinetic mixing with the hypercharge gauge boson. An SM neutral scalar is used to spontaneously break this extra symmetry, leading to the mass of the Z′. Except for three right-handed neutri

We propose an alternative method of constructing two Higgs-doublet models free from scalar mediated FCNC couplings at the tree-level. In a toy scenario, we have presented semi realistic textures for the Yukawa matrices, which can reproduce the approximate flavor structure in the quark sector. Presence of flavor diagonal but nonuniversal Yukawa couplings emerges as a distinguishing feature of such

Two-Higgs-doublet models (2HDMs) are minimal extensions of the Standard Model (SM) that may still be discovered at the LHC. The quartic couplings of their potentials can be determined from the measurement of the masses and branching ratios of their extended scalar sectors. We show that the evolution of these couplings through renormalization group equations can determine whether the observed 2HDM

Contrary to common perception, we show that the current Higgs data does not eliminate the possibility of a sequential fourth generation that get their masses through the same Higgs mechanism as the first three generations. The inability to fix the sign of the bottom-quark Yukawa coupling from the available data plays a crucial role in accommodating a chiral fourth generation which is consistent wi

Flavor symmetries à la Froggatt-Nielsen provide a compelling way to explain the hierarchies of fermionic masses and mixing angles in the Yukawa sector. In supersymmetric (SUSY) extensions of the Standard Model where the mediation of SUSY breaking occurs at scales larger than the breaking of flavor, this symmetry must be respected not only by the Yukawas of the superpotential but also by the soft-b

We propose a model where neutrino masses are generated at three loop order but neutrinoless double beta decay occurs at one loop. Thus we can have large neutrinoless double beta decay observable in the future experiments even when the neutrino masses are very small. The model receives strong constraints from the neutrino data and lepton flavor violating decays, which substantially reduces the numb

A vast literature on the theory and phenomenology of two-Higgs-doublet models (2HDM) exists since long. However, the present situation demands a revisit of some 2HDM properties. Now that a 125 GeV scalar resonance has been discovered at the LHC, with its couplings to other particles showing increasing affinity to the Standard Model Higgs-like behaviour, the 2HDM parameter space is more squeezed th

We show that in the Higgs triplet model, after the Higgs discovery, the mixing angle in the CP-even sector can be strongly constrained from unitarity. We also discuss how large quantum effects in h→γγ may arise in a Standard-Model-like scenario and a certain part of the parameter space can be ruled out from the diphoton signal strength. Using T-parameter and diphoton signal strength measurements,

We impose an S3 symmetry on the quark fields under which two of three quarks transform like a doublet and the remaining one as singlet, and use a scalar sector with the same structure of SU(2) doublets. After gauge symmetry breaking, a Z2 subgroup of the S3 remains unbroken. We show that this unbroken subgroup can explain the approximate block structure of the CKM matrix. By allowing soft breaking

In two-Higgs-doublet models with exact Z2 symmetry, putting mh ≃ 125 GeV at the alignment limit, the following limits on the heavy scalar masses are obtained from the conditions of unitarity and stability of the scalar potential: mH, mA, mH+ < 1 TeV and 1/8 < tan β < 8. The constraints from b → sγ and neutral meson mass differences, when superimposed on the unitarity constraints, put a tighter low

We show that the 2.4σ signal of the leptonic flavor violating (LFV) Higgs boson decay h→μτ, as observed by the CMS Collaboration recently, can be explained by a certain class of two-Higgs doublet models that allow controllable flavor-changing neutral current with a minimal number of free parameters. We postulate that (i) the alignment limit is maintained, which means the lightest neutral scalar (h

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We study the conditions required to make the two-Higgs-doublet-model (2HDM) scalar potential stable up to the Planck scale. The lightest CP-even scalar is assumed to have been found at the LHC and the alignment limit is imposed in view of the LHC Higgs data. We find that ensuring stability up to scales 1010GeV necessitates the introduction of a soft breaking parameter in the theory. Even then, som

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 analyze how the precision measurement of the Higgs to diphoton signal strength would severely constrain these scenarios due to the nondecoupling behavior of the charged scalars, to the extent that in the presence of exact discrete symmet