Baryon Asymmetry and Neutrino Mixing

Abstract

In theories where $B-L$ is a spontaneously broken local symmetry, the cosmological baryon asymmetry can be generated by the out-of-equilibrium decay of heavy Majorana neutrinos. We study this mechanism assuming a similar pattern of mixings and masses for leptons and quarks, as suggested by SO(10) unification. This implies that $B-L$ is broken at the unification scale ${\Lambda }_{\text{mbox}GUT}\sim 10^{16}$ GeV, if $m_{{\text{n}}_{\text{m}}}\sim 3\cdot 10^{-3}$eV as preferred by the MSW explanation of the solar neutrino deficit. The observed value of the baryon asymmetry, $n_B/s\sim 10^{-10}$, is then obtained without any fine tuning of parameters.

Comments: latex2e, 10 pages, 3 figures, uses epsfig