Predicting δPMNS, θPMNS23 and fermion mass ratios from flavour GUTs with CSD2

Abstract

Abstract 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 θ 13 PMNS , a deviation of θ 23 PMNS from π/4, as well as a leptonic Dirac CP phase δ PMNS 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 δ PMNS between 230° and 290°, and the quark CP phase δ CKM in accordance with a right-angled unitarity triangle (α UT = 90°). Also, our model setup predicts the quantities θ 23 PMNS and m d /m s with less uncertainty than current experimental precision, and allowing with future sensitivity to discriminate between them.