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Register a new userNatural neutrino sector in a 331-model with Froggatt-Nielsen mechanism
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The extensions of the Standard Model based on the $SU(3)_ctimes SU(3)_Ltimes U(1)_X$ gauge group (331-models) have been advocated to explain the number of fermion families in nature. It has been recently shown that the Froggatt-Nielsen mechanism, a popular way to explain the mass hierarchy of the charged fermions, can be incorporated into the 331-setting in an economical fashion (FN331). In this work we extend the FN331-model to include three right-handed neutrino singlets. We show that the seesaw mechanism is realized in this model. The scale of the seesaw mechanism is near the $SU(3)_Ltimes U(1)_X$-breaking scale. The model we present here simultaneously explains the mass hierarchy of all the fermions, including neutrinos, and the number of families.
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We present a doubly parametric extension of the standard Froggatt--Nielsen (FN) mechanism. As is well known, mass matrices of the up- and down-type quark sectors and the charged lepton sector in the standard model can be parametrized well by a parameter $lambda$ which is usually taken to be the sine of the Cabibbo angle ($lambda = sintheta_text{C} simeq 0.225$). However, in the neutrino sector, there is still room to realize the two neutrino mass squared differences $Delta m_text{sol}^2$ and $Delta m_text{atm}^2$, two large mixing angles $theta _{12}$ and $theta _{23}$, and non-zero $theta _{13}$. Then we consider an extension with an additional parameter $rho$ in addition to $lambda$. Taking the relevant FN charges for a power of $lambda~(=0.225)$ and additional FN charges for a power of $rho$, which we assume to be less than one, we can reproduce the ratio of the two neutrino mass squared differences and three mixing angles. In the normal neutrino mass hierarchy, we show several patterns for taking relevant FN charges and the magnitude of $rho$. We find that if $sin theta_{23}$ is measured more precisely, we can distinguish each pattern. This is testable in the near future, for example in neutrino oscillation experiments. In addition, we predict the Dirac CP-violating phase for each pattern.
We study Froggatt-Nielsen (FN) like flavor models with modular symmetry. The FN mechanism is a convincing solution to the flavor puzzle in quark sector. The FN mechanism requires an extra $U(1)$ gauge symmetry which is broken at high energy. Alternatively, in the framework of modular symmetry the modular weights can play the role of the FN charges of the extra $U(1)$ symmetry. Based on the FN-like mechanism with modular symmetry we present new flavor models for quark sector. Assuming that the three generations have a common representation under modular symmetry, our models simply reproduce the FN-like Yukawa matrices. We also show that the realistic mass hierarchy and mixing angles, which are related each other through the modular parameters and a scalar vev, can be realized in models with several finite modular groups (and their double covering groups) without unnatural hierarchical parameters.
The models with the gauge group $SU(3)_ctimes SU(3)_L times U(1)_X$ (331-models) have been advocated to explain why there are three fermion generations in Nature. As such they can provide partial understanding of the flavour sector. The hierarchy of Yukawa-couplings in the Standard Model is another puzzle which remains without compelling explanation. We propose to use Froggatt-Nielsen -mechanism in a 331-model to explain both fundamental problems. It turns out that no additional representations in the scalar sector are needed to take care of this. The traditional 331-models predict scalar flavour changing neutral currents at tree-level. We show that they are strongly suppressed in our model.
In the model of gauge mediation of SUSY breaking in the presence of tree-level mediation, the Froggatt-Nielsen mechanism provides a different hierarchy of sparticle masses. We study the spectra and show the results to be like those in an effective supersymmetric model.
We discuss the Dirac CP violating phase $delta_{CP}$ in the Froggatt-Nielsen model for a neutrino mass matrix $M_ u$ imposing a condition ${rm det} [M_ u]=0$. This additional condition restricts the CP violating phase $delta_{CP}$ drastically. We find that the phase $delta_{CP}$ is predicted in the region of $pm (0.4- 2.9)$ radian, which is consistent with the recent T2K and NO$ u$A data. There is a remarkable correlation between $delta_{CP}$ and $sin^2theta_{23}$. The phase $delta_{CP}$ converges on $sim pm pi/2$ if $sin^2theta_{23}$ is larger than $0.5$. Thus, accurate measurements of $sin^2theta_{23}$ are important for a test of our model. The effective mass $m_{ee}$ for the neutrinoless double beta decay is predicted in the rage of $3.3-4.0$ meV.
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