arXiv subjects
Publications and source records attributed to N. H. Thao.
We will show that the 3-4-1 model with heavy right-handed neutrinos can explain the recent experimental data of $(g-2)_{e, μ}$ anomalies of charged leptons and neutrino oscillations through the inverse seesaw mechanism. In addition, the model can predict large lepton flavor violating decay rates $μ\to eγ$ and $τ\to μγ, eγ$ up to the recent experimental sensitivities.
We propose a predictive model based on the $SU(3)_C\times SU(3)_L\times U(1)_X$ gauge symmetry, which is supplemented by the $D_4$ family symmetry and several auxiliary cyclic symmetries whose spontaneous breaking produces the observed SM fermion mass and mixing pattern. The masses of the light active neutrinos are produced by an inverse seesaw mechanism mediated by three right handed Majorana neutrinos. To the best of our knowledge the model corresponds to the first implementation of the $D_4$ family symmetry in a $SU(3)_C\times SU(3)_L\times U(1)_X$ theory with three right handed Majorana neutrinos and inverse seesaw mechanism. Our proposed model successfully accommodates the experimental values of the SM fermion mass and mixing parameters, the muon anomalous magnetic moment as well as the Higgs diphoton decay rate and meson oscillations constraints. The consistency of our model with the muon anomalous magnetic moment requires charged exotic vector like leptons at the TeV scale.
We perform a comprehensive analysis of several phenomenological aspects of the renormalizable extension of the inert 3-3-1 model with sequentially loop-generated SM fermion mass hierarchy. Special attention is paid to the study of the constraints arising from the experimental data on the $ρ$ parameter, as well as those ones resulting from the charged lepton flavor violating process $μ\to eγ$ and dark matter. We also study the single $Z'$ production via Drell-Yan mechanism at the LHC. We have found that $Z'$ gauge bosons heavier than about $4$ TeV comply with the experimental constraints on the oblique $ρ$ parameter as well as with the collider constraints. In addition, we have found that the constraint on the charged lepton flavor violating decay $μ\rightarrow eγ$ sets the sterile neutrino masses to be lighter than about $1.12$ TeV. In addition the model allows charged lepton flavor violating processes within reach of the forthcoming experiments. The scalar potential and the gauge sector of the model are analyzed and discussed in detail. Our model successfully accommodates the observed Dark matter relic density.
The lepton flavor violating decay of the Standard Model-like Higgs boson (LFVHD), h->μτ, is discussed in seesaw models at the one-loop level. Based on particular analytic expressions of Passarino-Veltman functions, the two unitary and 't Hooft Feynman gauges are used to compute the branching ratio of LFVHD and compare with results reported recently. In the minimal seesaw (MSS) model, the branching ratio was investigated in the whole valid range 10^{-9}-10^{15} GeV of new neutrino mass scale m_{n_6}. Using the Casas-Ibarra parameterization, this branching ratio enhances with large and increasing m_{n_6}. But the maximal value can reach only order of 10^{-11}. Interesting relations of LFVHD predicted by the MSS and inverse seesaw (ISS) model are discussed. The ratio between two LFVHD branching ratios predicted by the ISS and MSS is simply m^2_{n_6}μ^{-2}_X, where μ_X is the small neutrino mass scale in the ISS. The consistence between different calculations is shown precisely from analytical approach.
Masses and signals of the production of Doubly charged Higgses(DCH) in the framework of the supersymmetric reduced minimal 3-3-1 model(SUSYRM331) are investigated. In the DCH sector, weprove that there always exists a region of the parameter space where the mass of the lightest DCH is in order of $\mathcal{O}(100)$ GeV even when all other new particles are very heavy.The lightest DCH mainly decays to two same-sign leptons while the dominated decay channels of the heavy DCHs are those decay to heavy particles. We analyze each production cross section for $e^+e^- \rightarrow H^{++} H^{--}$ as a function of a few kinematic variables, which are useful to discuss the creation of the DCHs in the $e^+e^-$ colliders as a signal of new physics beyond the Standard Model. The numerical study shows that the cross sections for creating the lightest DCH can reach values of few pbs. The two other DCHs are too heavy, beyond the observable range of experiments. The lightest DCH may be detected by the International Linear Collider (ILC) or the Compact LInear Collider (CLIC) by searching its decay to a same-sign charged lepton pair.
We analyze the potential of Compact Linear Colliders based on the γ-e collisions to search for the radion in the Randall-Sundrum model, where compactification radius of the extra dimension is stabilized by the radion, which is a scalar field lighter than the graviton Kaluza-Klein states. The radion production in the high energy γ-e colliders with the polarization of the electron beams are calculated in detail. Numerical evaluation shows that if the radion mass is not too heavy with the mass order of GeV then the reaction can give observable cross section in future colliders at the high degree of polarization.
An attempt is made to present some experimental predictions of the Randall-Sundrum model, where compactification radius of the extra dimension is stabilized by the radion, which is a scalar field lighter than the graviton Kaluza-Klein states. We calculate the conversion cross-sections of the photons into the radions in the external electromagnetic fields, namely, in the static fields and in a periodic field of the wave guide. Numerical evaluations of the total cross-sections are also given. Our result shows that the conversion cross-section in the static electric field is quite small. But, in the static magnetic and periodic fields, the radion productions are much enhanced.
The symmetry factor of Feynman diagrams for real and complex scalar fields is presented. Being analysis of Wick expansion for Green functions, the mentioned factor is derived in a general form. The symmetry factor can be separated into two ones corresponding to that of connected and vacuum diagrams. The determination of symmetry factors for the vacuum diagrams is necessary as they play a role in the effective action and phase transitions in cosmology. In the complex scalar theory the diagrams different in topology may give the same contribution, hence inverse of the symmetry factor (1/S) for total contribution is a summation of each similar ones (1/S_i), i.e., 1/S = \sum_i (1/S_i).