Top-Down Analysis of Leptogenesis and Dirac Neutrino Masses in an Extended CP-Violating Standard Model

We analytically investigate the charge parity (CP) violation, neutrino masses, and leptogenesis in the Standard Model (SM) with an extension to Dirac neutrinos, building on our previous quark sector analysis. Using systematic top-down diagonalization of fermion mass matrices and experimental neutrino mass-squared differences, we predict the complete neutrino mass spectrum and assess leptogenesis viability. We find that our analysis yields specific mass predictions: mh≈5.01×10−2 eV, ml≈6.09×10−3 eV, and a bimodal middle mass (mm≈4.97×10−2 eV for inverted ordering, mm≈1.05×10−2 eV for normal ordering). Four viable scenarios emerge with parameter constraints ranging from highly restrictive (1<g<1.01512) to moderately broad (1<g<5.9). Crucially, Dirac neutrino leptogenesis is about 71 orders of magnitude weaker than baryogenesis, indicating that Standard Model leptogenesis is negligible and Beyond Standard Model physics is needed for significant leptogenesis contributions. CP violation emerges through SN symmetry breaking, with mass degeneracies controlled by model parameters. Remarkably, while mass-squared differences are small, individual neutrino masses can be significantly larger, potentially addressing dark matter mass requirements and enhancing cosmological significance. This work provides testable predictions for neutrino experiments and establishes a unified analytical approach to CP violation across fermion sectors.