Neutrino Majorana Mass and Baryon Number of the Universe below the   Electroweak Symmetry breaking Scale
  If the neutrino is Majorana type and the electroweak phase transition is second or weak first order, neutrino-induced interactions together with sphaleron transitions have the potential to erase a previously generated baryon asymmetry of the universe. Taking correctly into account the evolution of the vacuum expectation of the Higgs field the effective light neutrino masses are constrained to be lighter than order 10 MeV, while the effective heavy masses are constrained to be heavier than order 10^7 GeV. 
H.V. Klapdor-Kleingrothaus, St. Kolb, U. Sarkar