A bridge between CP violation at low energies and leptogenesis

We discuss the possibility of relating the size and sign of the observed ba ryon asymmetry of the universe to CP violation observable at low energies, in a framework where the observed baryon asymmetry is produced by leptogene sis through the out of the equilibrium decay of heavy Majorana neutrinos. W e identify the CP violating phases entering in leptogenesis as well as thos e relevant for CP violation at low energies in the minimal seesaw model. We show that although in general there is no relation between these two sets of phases, there are specific frameworks in which such a connection may be established and we give a specific grand unification inspired example where such a connection does exist. We construct weak-basis invariants related t o CP violation responsible for leptogenesis, as well as those relevant for CP violation at low energies. (C) 2001 Elsevier Science B.V. All rights res erved.