Minimal spontaneous CP-violating GUT and predictions for leptonic CP phases

A nonsupersymmetric renormalizable SO(10) model, with CP invariant Yukawa sector consisting of Lorentz scalars in 10 and (126) over bar dimensional representations, is proposed. The elemental Yukawa couplings are real due to CP symmetry. The latter is broken in the low energy effective theory through the standard model Higgs which is a complex linear combination of electroweak doublets residing in 10 and (126) over bar scalars. As a result, the mass matrices in the quark and lepton sectors, including those of heavy and light neutrinos, depend only on three phases which in turn determine CP violation in both sectors. The model is comprehensively analyzed for its viability and predictions including the possibility to generate baryon asymmetry through thermal leptogenesis. It predicts relatively small values for CP phases in the lepton sector. Successful leptogenesis further restricts the ranges to -0.4 <= sin delta <= 0.4 for the Dirac phase and -0.3 <= sin eta(1) <= 0.2, -0.5 <= sin eta(2) <= 0.5 for the Majorana phases.