Asymmetric lepton production in a universe with non-zero baryon number

Abstract

Due to processes occurring during different stages of stellar evolution, a universe with a net baryon number develops an excess of neutrinos and positrons over antineutrinos of the same order as the observed relative strength of CP violation, over the course of a Hubble age. Since the neutrinos have a left-handed helicity, an initially symmetric universe would become weakly left-handed after a period of about 10 to the 10th years.