Speaker
Description
In the canonical seesaw framework flavor mixing and CP violation in weak charged-current interactions of {\it light} and {\it heavy} Majorana neutrinos are correlated with each other and described respectively by the $3\times 3$ matrices $U$ and $R$. We show that the very possibility of $\big|U^{}_{\mu i}\big| = \big|U^{}_{\tau i}\big|$ (for $i = 1, 2, 3$), which is strongly indicated by current neutrino oscillation data, automatically leads to a novel prediction $\big|R^{}_{\mu i}\big| = \big|R^{}_{\tau i}\big|$ (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 $\nu^{}_{e \rm L} \to (\nu^{}_{e \rm L})^c$, $\nu^{}_{\mu \rm L} \to (\nu^{}_{\tau \rm L})^c$, $\nu^{}_{\tau \rm L} \to (\nu^{}_{\mu \rm L})^c$ and the right-handed neutrino fields undergo an arbitrary unitary CP transformation. Such a generalized $\mu$-$\tau$ reflection symmetry can greatly help constrain the flavor textures of active and sterile neutrinos and hence enhance predictability and testability of the seesaw mechanism.
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