An SO(10)×S4×Zn model of Quark-Lepton Complementarity

The present observations of Cabibbo angle and solar mixing angle satisfy the empirical relation called Quark-Lepton Complementarity (QLC), namely θ12l∼π/4−θC. It suggests the existence of correlation between quarks and leptons which is supported by the idea of grand unification. We propose a specific ansatz for the structure of Yukawa matrices in SO(10) unified theory which leads to similar relation if neutrinos get masses through type-II seesaw mechanism. Viability of this ansatz is discussed through detailed analysis of fermion masses and mixing angles all of which can be explained in a model which uses three Higgs fields transforming as 10 and one transforming as 126¯ representations under SO(10). It is shown that the proposed ansatz can be derived from an extended model based on the two pairs of 16-dimensional vector-like fermions and an S4×Zn flavor symmetry. The model leads to the lepton mixing matrix that is dominantly bimaximal with O(θC) corrections related to quark mixings. A generic prediction of the model is the reactor angle θ13l∼θC/2 which is close to its present experimental upper bound.