Neutrino spin flavor precession and leptogenesis

Abstract

We argue that $\ensuremath{\Delta}L=2$ neutrino spin flavor precession, induced by the primordial magnetic fields, could have a significant impact on the leptogenesis process that accounts for the baryon asymmetry of the Universe. Although the extragalactic magnetic field is extremely weak at the present time (about ${10}^{\ensuremath{-}9}\text{ }\text{ }\mathrm{Gauss}$), the primordial magnetic field at the electroweak scale could be quite strong (of order ${10}^{17}\text{ }\text{ }\mathrm{Gauss}$). Therefore, at this scale, the effects of the spin flavor precession are not negligible. We show that the lepton asymmetry may be reduced by 50% due to the spin flavor precession. In addition, the leptogenesis will have different features from the standard scenario of leptogenesis, where the lepton asymmetry continues to oscillate even after the electroweak phase transition.