Cosmological Bounds to the Magnetic Moment of Heavy Tau Neutrinos

Abstract

The magnetic moment of tau neutrinos in the MeV mass range may be large enough to modify the cosmological freeze-out calculation and determine the tau-neutrino relic density. In this paper we revisit such a possibility. We calculate the evolution and freeze-out of the tau neutrino number density as a function of its mass and magnetic moment. We then determine its relic density, then calculate its effect upon primordial nucleosynthesis including previously neglected effects.