The importance of flavor in leptogenesis

Abstract

We study leptogenesis from the out-of-equilibrium decays of the lightest heavy neutrino N1 in the medium (low) temperature regime, T≲1012 GeV (109 GeV), where the rates of processes mediated by the τ (and μ) Yukawa coupling are non negligible, implying that the effects of lepton flavors must be taken into account. We find important quantitative and qualitative differences with respect to the case where flavor effects are ignored: (i) The cosmic baryon asymmetry can be enhanced by up to one order of magnitude; (ii) The sign of the asymmetry can be opposite to what one would predict from the sign of the total lepton asymmetry ε1; (iii) Successful leptogenesis is possible even with ε1 ≤ 0. © SISSA 2006.