A bridge between CP violation at low energies and leptogenesis

Abstract

We discuss the possibility of relating the size and sign of the observed baryon asymmetry of the universe to CP violation observable at low energies, in a framework where the observed baryon asymmetry is produced by leptogenesis through the out of the equilibrium decay of heavy Majorana neutrinos. We identify the CP violating phases entering in leptogenesis as well as those 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 to CP violation responsible for leptogenesis, as well as those relevant for CP violation at low energies. * gbranco@thwgs.cern.ch and

Algebraic structure of lepton and quark flavor invariants andCPviolation

“…For three generations, even the Hilbert series proved too difficult to compute. For this case, we make some general remarks, and discuss some invariants considered previously by Branco et al [26,27], and by Davidson and Kitano [15].…”

Insensitivity of Leptogenesis with Flavor Effects to Low Energy LeptonicCPViolation

“…The answer was ''no'' for unflavored leptogenesis in the standard model seesaw [3]. This was not surprising; the seesaw contains more phases than the PMNS matrix, and many unmeasurable real parameters which can be adjusted to obtain a big enough asymmetry.…”

“…10 12 GeV, the final baryon asymmetry depends separately on the lepton asymmetry in s, and on the lepton asymmetry in muons and electrons. So in this Letter, we revisit the question addressed in [3], but with the inclusion of flavor effects. Our analysis differs from recent discussions [7] (2RHN model), [8,9] (CP as a symmetry of the N sector), [10] (sequential N dominance) in that we wish to do a bottom-up analysis of the three generation seesaw.…”

“…It was shown in [3] that the BAU produced by thermal leptogenesis in the type 1 seesaw, without ''flavor effects,'' is insensitive to PMNS phases. That is, the PMNS phases can be zero while leptogenesis works, and the CP asymmetry of leptogenesis can vanish for arbitrary values of the PMNS phases.…”

Four-zero neutrino Yukawa textures in the minimal seesaw framework

“…The scenario of baryogenesis through leptogenesis has been rendered especially appealing by the discovery of neutrino oscillations, which provides evidence for nonvanishing neutrino masses. In general, there is no direct connection between CP violation at low energies and that entering in leptogenesis [22,23]. It has been shown, however, that such a connection arises in models with texture zeros in m D [1,13,24,25].…”