On the Breaking of μ-τ Flavor Symmetry

In light of the observation of a relatively large θ₁₃, one has to consider breaking the μ-τ symmetry properly which would otherwise result in a vanishing θ₁₃ (as well as θ₂₃ = π/4). Therefore, we investigate various symmetry-breaking patterns and accordingly identify those that are phenomenologically viable. Furthermore, the symmetry-breaking effects arising from some specific physics (e.g., the renormalization group equation running effect) are discussed as well.