Atmospheric Neutrino octant from flavor symmetry

The binary tetrahedral group ([Formula: see text]) has provided the most successful flavor symmetry in understanding simultaneously the three mixing angles both for quarks in the CKM matrix and for neutrinos in the PMNS matrix. One prediction, invariant under leptonic CP violation, relates the atmospheric and reactor neutrino mixings [Formula: see text] and [Formula: see text], respectively. We study sedulously this relation using the latest neutrino data. It is natural to focus on the frustrating experimental octant ambiguity of [Formula: see text]. We conclude that the flavor symmetry requires that [Formula: see text] is in the second octant [Formula: see text], not in the first one [Formula: see text], and eagerly await experimental confirmation of this prediction.