The mass hierarchies of quarks and charged leptons as well as a large $\n_\m$-$\n_\t$ mixing angle are naturally explained by the Frogatt-Nielsen mechanism with a nonparallel family structure of chiral charges. We extend this mechanism to right-handed neutrinos. Their out-of-equilibrium decay generates a cosmological baryon asymmetry whose size is quantized in powers of the hierarchy parameter $\e^2$. For the simplest hierarchy pattern the neutrino mass $\bar{ m}_\n= (m_{ \n_\m}m_{ \n_\t})^{ 1/2} \sim 10^{ -2}$ eV, which is inferred from present indications for neutrino oscillations, implies a baryon asymmetry $n_B/s \sim 10^{ -10}$. The corresponding baryogenesis temperature is $T_B \sim 10^{ 10}$ GeV.
Categories: hep-ph