On the baryon, lepton-flavour and right-handed electron asymmetries of the universe

Abstract

Non-perturbative electroweak effects, in thermal equilibrium in the early universe, have the potential to erase the baryon asymmetry of the universe, unless it is encoded in a B - L asymmetry, or in some “accidentally” conserved quantity. We first consider the possibility that the BAU may be regenerated from lepton flavour asymmetries even when initially B - L = 0. We show that provided some, but not all the lepton flavours are violated by ΔL ≠ 0 interactions in equilibrium, the BAU may be regenerated without lepton mass effects. We next examine the possibility of encoding the baryon asymmetry in a primordial asymmetry for the right-handed electron, which due to its weak Yukawa interaction only comes into chemical equilibrium as the sphalerons are falling out of equilibrium. This would also raise the possibility of preserving an initial baryon asymmetry when B - L = 0.