Leptogenesis with Dirac Neutrinos

We describe a “neutrinogenesis” mechanism whereby, in the presence of right-handed neutrinos with sufficiently small pure Dirac masses, $(B+L)$-violating sphaleron processes create the baryon asymmetry of the Universe, even when $B=L=0\mathrm{}$ initially. It is shown that the resulting neutrino mass constraints are easily fulfilled by the neutrino masses suggested by current experiments. We present a simple toy model which uses this mechanism to produce the observed baryon asymmetry of the Universe.