Predicting δPMNS, θ23PMNS and fermion mass ratios from flavour GUTs with CSD2

Constrained Sequential neutrino Dominance of type 2 (referred to as CSD2) is an attractive building block for flavour Grand Unified Theories (GUTs) because it predicts a non-zero leptonic mixing angle θ13PMNS, a deviation of θ23PMNS from π/4, as well as a leptonic Dirac CP phase δPMNS which is directly linked to the CP violation relevant for generating the baryon asymmetry via the leptogenesis mechanism. When embedded into GUT flavour models, these predictions are modified in a specific way, depending on which GUT operators are responsible for generating the entries of fermion Yukawa matrices. In this paper, we systematically investigate and classify the resulting predictions from supersymmetric SU(5) based flavour models by fitting the known fermion mass and mixing data, in order to provide a roadmap for future model building. Interestingly, the promising models predict the lepton Dirac CP phase δPMNS between 230° and 290°, and the quark CP phase δCKM in accordance with a right-angled unitarity triangle (αUT = 90°). Also, our model setup predicts the quantities θ23PMNS and md/ms with less uncertainty than current experimental precision, and allowing with future sensitivity to discriminate between them.