Flavor Dependent $U(1)$ Symmetric Zee Model with a Vector-like Lepton

TL;DR

This paper proposes an extended Zee model with a flavor-dependent $U(1)$ symmetry and a vector-like lepton, addressing neutrino oscillations, CP violation, and electroweak baryogenesis while predicting distinctive Higgs decay patterns.

Contribution

The model introduces a flavor-dependent $U(1)$ symmetry and vector-like leptons, successfully explaining neutrino data, suppressing quark FCNCs, and enabling electroweak baryogenesis with unique Higgs decay signatures.

Findings

Neutrino oscillation data can be explained within the model.

A parameter space exists for a strongly first order electroweak phase transition.

Characteristic Higgs decay patterns like $H o AZ$ or $H o AA$ are predicted.

Abstract

We extend the Zee model by introducing a vector-like lepton doublet and a flavor dependent global $U(1)$ symmetry. Flavor changing neutral currents in the quark sector can be naturally forbidden at tree level due to the $U(1)$ symmetry, while sufficient amount of lepton flavor violation is provided to explain current neutrino oscillation data. In our model, additional sources of CP-violation appear in the lepton sector, but their contribution to electric dipole moments is much smaller than current experimental bounds due to the Yukawa structure constrained by the $U(1)$ symmetry. We find that there is a parameter region where the strongly first order electroweak phase transition can be realized, which is necessary for the successful scenario of the electroweak baryogenesis in addition to new CP-violating phases. In the benchmark points satisfying neutrino data, lepton flavor violation data and the strongly first order phase transition, we show that an additional CP-even Higgs boson $H$ mainly decays into a lighter CP-odd Higgs boson $A$, i.e., $H \to AZ$ or $H \to AA$ with a characteristic pattern of lepton flavor violating decays of $A$.