Quark lepton mass hierarchies and the baryon asymmetry

The mass hierarchies of quarks and charged leptons as well as a large nu(mu )-nu(tau) mixing angle are naturally explained by the Frogatt-Nielsen mecha nism with a nonparallel family structure of chiral charges. We extend this mechanism to right-handed neutrinos. Their out-of-equilibrium decay generat es a cosmological baryon asymmetry whose size is quantized in powers of the hierarchy parameter epsilon(2). For the simplest hierarchy pattern the neu trino mass (m) over bar(nu) = (m(nu mu) m(nu tau))(1/2) similar to 10(-2) e V, which is inferred from present indications for neutrino oscillations, im plies a baryon asymmetry n(B)/s similar to 10(-10). The corresponding baryo genesis temperature is T-B similar to 10(10) GeV. (C) 1999 Elsevier Science B.V. All rights reserved.