On the “Low” and “High” Energy CP Violation in Leptogenesis

Abstract

The CP violation necessary for the generation of the baryon asymmetry of the Universe YB in the “flavoured” leptogenesis scenario, based on the simplest type I see-saw model of ν -mass generation, can arise from the “low energy” neutrino mixing matrix U and/or from the “high energy” part of neutrino Yukawa couplings. The latter can mediate CP-violating phenomena only at some high energy scale. We review briefly some of the results on the the interplay between the contributions in Y B due to these two sources of CP violation in thermal leptogenesis with three heavy right-handed Majorana neutrinos having hierarchical mass spectrum.