Broken S_3L×S_3R flavor symmetry and leptonic CP violation

Abstract: In the framework of the canonical seesaw model, we present a simple but viable scenario to explicitly break an S_3L×S_3R flavor symmetry in the leptonic sector. It turns out that the leptonic flavor mixing matrix is completely determined by the mass ratios of the charged leptons (i.e., m_e/m_μ and m_μ/m_τ) and those of light neutrinos (i.e., m₁/m₂ and m₂/m₃). The latest global-fit results of the three neutrino mixing angles θ₁₂, θ₁₃, θ₂₃ and two neutrino mass-squared differences △ m₂₁², △ m₃₁² at the 3σ level are used to constrain the parameter space of m₁/m₂, m₂/m₃. The predictions for the mass spectrum and flavor mixing are highlighted:(1) the neutrino mass spectrum shows a hierarchical pattern and a normal ordering, e.g., m₁ ≈ 2.2 meV, m₂ ≈ 8.8 meV and m₃ ≈ 52.7 meV; (2) only the first octant of θ₂₃ is allowed, namely, 41.8° ≤ θ₂₃ ≤ 43.3° (3) the Dirac CP-violating phase δ ≈ -22° deviates significantly from the maximal value -90°. All these predictions are ready to be tested in ongoing and forthcoming neutrino oscillation experiments. Moreover, we demonstrate that the cosmological matter-antimatter asymmetry can be explained via resonant leptogenesis, including the individual lepton-flavor effects. In our scenario, leptonic CP violation at low-and high-energy scales is closely connected.