We consider the minimal 3-3-1 model with a heavy scalar sextet and realize, at the tree level, an effective dimension-five interaction that contributes to the mass of the charged leptons. In this case the charged leptons masses arise from a sort of t
ype-II seesawlike mechanism while the neutrino masses are generated by a type-I mechanism. We also show that the parameters giving the correct lepton masses also accommodate the Pontecorvo-Maki-Nakawaga-Sakata matrix. We give the scalar mass spectra of the model and analyze under which conditions the fields in the scalar sextet are heavy even with small or zero vacuum expectation values. We also show the conditions under which it is possible to have a stable (bounded from below) potential and also a global minimum.
We consider the decays $htogammagamma,gamma Z$ in the context of an extension of the standard model with two inert doublets and an additional $S_3$ symmetry. This model has contributions for these processes through new charged scalar-loops. Comparing
our $htogammagamma$ with the more precise available experimental data we can predict the behaviour of $htogamma Z$ due that they depend on the same parameters, our estimation for this channel is 1.05 times the standard model value, but can be up to 1.16 if consider the $+1sigma$ uncertainty from the $htogammagamma$ data, and down to 0.96 if consider $-1sigma$.
In this work we present the characterization of the mixing matrix when the mass matrix is considered, without seesaw, for 3+2 models like.
We study a two scalar inert doublet model (IDMS$_3$) which is stabilized by a $S_3$ symmetry. We consider two scenarios: i) two of the scalars in each charged sector are mass degenerated due to a residual $Z_2$ symmetry, ii) there is no mass degenera
cy because of the introduction of soft terms that break the $Z_2$ symmetry. We show that both scenarios provide good dark matter candidates for some range of parameters.
The recent detection of the cosmic microwave background polarimeter experiment BICEP2 of tensor fluctuations in the B-mode power spectrum basically excludes all plausible axion models where its decay constant is above $10^{13}$ GeV. Moreover, there a
re strong theoretical, astrophysical, and cosmological motivations for models involving, in addition to the axion, also axion-like particles (ALPs), with decay constants in the intermediate scale range, between $10^9$ GeV and $10^{13}$ GeV. Here, we present a general analysis of models with an axion and further ALPs and derive bounds on the relative size of the axion and ALP photon (and electron) coupling. We discuss what we can learn from measurements of the axion and ALP photon couplings about the fundamental parameters of the underlying ultraviolet completion of the theory. For the latter we consider extensions of the Standard Model in which the axion and the ALP(s) appear as pseudo Nambu-Goldstone bosons from the breaking of global chiral $U(1)$ (Peccei-Quinn (PQ)) symmetries, occuring accidentally as low energy remnants from exact discrete symmetries. In such models, the axion and the further ALP are protected from disastrous explicit symmetry breaking effects due to Planck-scale suppressed operators. The scenarios considered exploit heavy right handed neutrinos getting their mass via PQ symmetry breaking and thus explain the small mass of the active neutrinos via a seesaw relation between the electroweak and an intermediate PQ symmetry breaking scale. We show some models that can accommodate simultaneously an axion dark matter candidate, an ALP explaining the anomalous transparency of the universe for $gamma$-rays, and an ALP explaining the recently reported 3.55 keV gamma line from galaxies and clusters of galaxies, if the respective decay constants are of intermediate scale.
We show that in the minimal 3-3-1 model the flavor changing neutral currents (FCNCs) do not impose necessarily strong constraints on the mass of the $Z^prime$ of the model if we also consider the neutral scalar contributions to such processes, like t
he neutral mesons mass difference and rare semileptonic decays. We first obtain numerical values for all the mixing matrices of the model i.e., the unitary matrices that rotate the left- and right-handed quarks in each charge sector which give the correct mass of all the quarks and the CKM mixing matrix. Then, we find that there is a range of parameters in which the neutral scalar contributions to these processes may interfere with those of the $Z^prime$, implying this vector boson may be lighter than it has been thought.
We present an analysis of the solar neutrino data in the context of a quasi-Dirac neutrino model in which the lepton mixing matrix is given at tree level by the tribimaximal matrix. When radiative corrections are taken into account, new effects in ne
utrino oscillations, as $ u_e to u_s$, appear. This oscillation is constrained by the solar neutrino data. In our analysis, we have found an allowed region for our two free parameters $epsilon$ and $m_1$. The radiative correction, $epsilon$, can vary approximately from $5times 10^{-9}$ to $10^{-6}$ and the calculated fourth mass eigenstate, $m_4$, 0.01 eV to 0.2 eV at 2$sigma$ level. These results are very similar to the ones presented in the literature.
We consider a three Higgs doublet model with an $S_3$ symmetry in which beside the SM-like doublet there are two fermiophobic doublets. Due to the new charged scalars there is an enhancement in the two-photon decay while the other channels have the s
ame decay widths that the SM neutral Higgs. The fermiophobic scalars are mass degenerated unless soft terms breaking the $S_3$ symmetry are added.
We propose a simple extension of the electroweak standard model based on the discrete $S_3$ symmetry that is capable of realizing a nearly minimal Fritzsch-type texture for the Dirac mass matrices of both charged leptons and neutrinos. This is achiev
ed with the aid of additional $Z_5$ and $Z_3$ symmetries, one of which can be embedded in $U(1)_{B-L}$. Five complex scalar singlet fields are introduced in addition to the SM with right-handed neutrinos. Although more general, the modified texture of the model retains the successful features of the minimal texture without fine-tuning; namely, it accommodates the masses and mixing of the leptonic sector and relates the emergence of large leptonic mixing angles with the seesaw mechanism. For large deviations of the minimal texture, both quasidegenerate spectrum or inverted hierarchy are allowed for neutrino masses.
We consider an extension of the standard model (SM) with three $SU(2)$ scalar doublets and a discrete $S_3otimes mathbb{Z}_2$ symmetries. The irreducible representation of $S_3$ has a singlet and a doublet, and here we show that the singlet correspon
ds to the SM-like Higgs and the two additional $SU(2)$ doublets forming a $S_3$ doublet are inert. In general, in a three scalar doublet model, with or without $S_3$ symmetry, the diagonalization of the mass matrices implies arbitrary unitary matrices. However, we show that in our model these matrices are of the tri-bimaximal type. We also analyzed the scalar mass spectra and the conditions for the scalar potential is bounded from below at the tree level. We also discuss some phenomenological consequences of the model.
