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We study previously unconsidered 3-3-1 models which are characterized by each lepton generation having a different representation under the gauge group. Flavor-changing neutral currents in the lepton sector occur in these models. To satisfy constraints on mu to 3e decays, the Z must be heavier than 2 to 40 TeV, depending on the model and assignments of the leptons. These models can result in very unusual Higgs decay modes. In most cases the mu-tau decay state is large (in one case, it is the dominant mode), and in one case, the Higgs to s-sbar rate dominates.
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We study radion phenomenology in an warped extra-dimension scenario with Standard Model fields in the bulk, with and without an additional fourth family of fermions. The radion couplings with the fermions will be generically misaligned with respect to the Standard Model fermion mass matrices, therefore producing some amount of flavor violating couplings and potentially influencing production and decay rates of the radion. Simple analytic expressions for the radion-fermion couplings are obtained with three or four families. We also update and analyze the current experimental limits on radion couplings and on the model parameters, again with both three and four families scenarios. We finally present the modified decay branching ratios of the radion with an emphasis on the new channels involving flavor diagonal and flavor violating decays into fourth generation quarks and leptons.
The one loop contribution to the lepton flavor violating decay $h^0rightarrow mutau$ of the SM-like neutral Higgs (LFVHD) in the 3-3-1 model with neutral lepton is calculated using the unitary gauge. We have checked in detail that the total contribution is exactly finite, and the divergent cancellations happen separately in two parts of active neutrinos and exotic heavy leptons. By numerical investigation, we have indicated that the one-loop contribution of the active neutrinos is very suppressed while that of exotic leptons is rather large. The branching ratio of the LFVHD strongly depends on the Yukawa couplings between exotic leptons and $SU(3)_L$ Higgs triplets. This ratio can reach $10^{-5}$ providing large Yukawa couplings and constructive correlations of the $SU(3)_L$ scale ($v_3$) and the charged Higgs masses. The branching ratio decreases rapidly with the small Yukawa couplings and large $v_3$.
We consider the minimal 3-3-1 model with three sterile neutrinos transforming as singlet under the $SU(3)_Lotimes U(1)_X$ symmetry. This model, with or without sterile neutrinos, predicts flavor violating interactions in both quark and lepton sectors, since all the charged fermions mass matrices can not be assumed diagonal in any case. Here we accommodate the lepton masses and the Pontecorvo-Maki-Nakawaga-Sakata matrix at the same time, and as consequence the Yukawa couplings and the unitary matrices which diagonalize the mass matrices are not free parameters anymore. We study some phenomenological consequences, i.e., $l_ito l_jl_k bar{l}_k$ and $l_ito l_jgamma$ which are induced by neutral and doubly charged particles present in the model. In particular we find that if the decay $muto eebar{e}$ is observed in the future, the only particle in the model that could explain this decay is the doubly charged vector bilepton.
We propose two 3-3-1 models (with either neutral fermions or right-handed neutrinos) based on S_3 flavor symmetry responsible for fermion masses and mixings. The models can be distinguished upon the new charge embedding (mathcal{L}) relevant to lepton number. The neutrino small masses can be given via a cooperation of type I and type II seesaw mechanisms. The latest data on neutrino oscillation can be fitted provided that the flavor symmetry is broken via two different directions S_3 rightarrow Z_2 and S_3 rightarrow Z_3 (or equivalently in the sequel S_3 rightarrow Z_2 rightarrow Identity), in which the second direction is due to a scalar triplet and another antisextet as small perturbation. In addition, breaking of either lepton parity in the model with neutral fermions or lepton number in the model with right-handed neutrinos must be happened due to the mathcal{L}-violating scalar potential. The TeV seesaw scale can be naturally recognized in the former model. The degenerate masses of fermion pairs (mu, tau), (c, t) and (s, b) are respectively separated due to the S_3 rightarrow Z_3 breaking.
The stellar energy-loss rates $mathcal{Q}$ due to the production of neutrino pair in the framework of 3-3-1 models are presented. The energy loss rate $mathcal{Q}$ is evaluated for different values of $beta=pmfr{1}{sqrt{3}},pmfr{2}{sqrt{3}},pmsqrt{3}$ in which $beta$ is a parameter used to define the charge operator in the 3-3-1 models. The correction to the rate which is compared with that of the Standard Model ($de mathcal{Q}$) is also evaluated. We show that the correction does not exceed 14% and %is gets the highest with $beta=-sqrt{3}$. The contribution of dipole moment to the energy loss rate is small compared to the contribution of new natural gauge boson $Z$ and this sets constraints for the mass of Z $m_{Z} leq 4000$ GeV. This mass range is within the searching range for $Z$ boson at LHC.
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