Decimation and survival at baryon violating gauntlet

Abstract

We find that for second and weakly first order electroweak phase transition (EWPT) the mere presence of non-zero Majorana masses for left-handed neutrinos is sufficient to ensure the destruction of any existing baryon (lepton) asymmetry. Even if the EWPT is strongly first order, a baryon asymmetry generated before EWPT is seen to only barely survive, to the present, for cosmologically interesting values of neutrino masses and mixing angles; the scenario for survival being particularly bleak in the presence of an $SU(2)_R$ gauge symmetry at intermediate scales. Two sets of models, presented by us earlier, that can avert the destruction of baryon asymmetry for any value of neutrino masses and mixing angles and any order of EWPT are briefly discussed and their relevance, in the light of latest observations, is pointed out.