BARYON ASYMMETRY AND NEUTRINO MIXING

In theories where B - L is a spontaneously broken local symmetry, the cosmological baryon asymmetry can be generated by the out-of-equilibri um decay of heavy Majorana neutrinos. We study this mechanism assuming a similar pattern of mixings and masses for leptons and quarks, as su ggested by SO(10) unification. This implies that B - L is broken at th e unification scale Lambda(GUT) similar to 10(16) GeV, if m(nu mu) sim ilar to 3.10(-3) eV as preferred by the MSW explanation of the solar n eutrino deficit. The observed value of the baryon asymmetry, n(B)/s si milar to 10(-10), is then obtained without any fine tuning of paramete rs.