Identifying a minimal flavor symmetry of the seesaw mechanism behind neutrino oscillations

Abstract

Abstract In the canonical seesaw framework flavor mixing and CP violation in weak charged-current interactions of light and heavy Majorana neutrinos are correlated with each other and described respectively by the 3 × 3 matrices U and R. We show that the very possibility of |U μi | = |U τi | (for i = 1, 2, 3), which is strongly indicated by current neutrino oscillation data, automatically leads to a novel prediction |R μi | = |R τi | (for i = 1, 2, 3). We prove that behind these two sets of equalities and the experimental evidence for leptonic CP violation lies a minimal flavor symmetry — the overall neutrino mass term keeps invariant when the left-handed neutrino fields transform as ν eL → (ν eL) c , ν μL → (ν τL) c , ν τL → (ν μL) c and the right-handed neutrino fields undergo an arbitrary unitary CP transformation. Such a generalized μ-τ reflection symmetry may help constrain the flavor textures of active and sterile neutrinos to some extent in the seesaw mechanism.

Keywords

• CP Violation
• Discrete Symmetries
• Neutrino Mixing
• Sterile or Heavy Neutrinos