Revisiting Quark-Lepton Complementarity in the Precision Neutrino Era

Abstract

We revisit three-generation quark-lepton complementarity in the non-trivial correlation-matrix formulation using the 2026 Particle Data Group quark-mixing inputs and the NuFIT 6.1 oscillation likelihood release. First, we perform a retrospective test of the narrow atmospheric-angle prediction published in 2016. Its central value receives likelihood penalties of 17.99 and 20.43 for normal and inverted ordering, respectively, whereas later ordering-dependent predictions lie close to the current likelihood minima. We then reconstruct a projection-weighted ensemble of the full complex correlation matrix, retaining unrestricted quark-lepton mismatch phases and exact sample-wise unitarity. The first row remains comparatively stable, while the lower two rows account for about 99% of the decade-long mean-texture evolution. The strongest normal-inverted differences occur in the third-row elements, with distribution-overlap coefficients of about 0.41 and 0.42 for the first two entries. Approximately 72% of the present ensemble remains closer to a tribimaximal than to a bimaximal reference texture. The results show that the broad quark-lepton correlation structure is substantially more persistent than the most restrictive atmospheric-angle prediction derived from it.