Leptogenesis and the Violation of Lepton Number and CP at Low Energies

John Ellis; Martti Raidal

doi:10.1016/S0550-3213(02)00753-8

paper

Leptogenesis and the Violation of Lepton Number and CP at Low Energies

arXiv:hep-ph/0206174 · doi:10.1016/S0550-3213(02)00753-8

Abstract

In the context of the minimal supersymmetric seesaw model, we study the implications of the current neutrino data for thermal leptogenesis, $β β_{0 ν}$ decay, and leptonic flavour- and CP-violating low-energy observables. We express the heavy singlet-neutrino Dirac Yukawa couplings $(Y_{ν})_{ij}$ and Majorana masses $M_{N_{i}}$ in terms of the light-neutrino observables and an auxiliary hermitian matrix $H$ , which enables us to scan systematically over the allowed parameter space. If the lightest heavy neutrino $N_{1}$ decays induce the baryon asymmetry, there are correlations between the $M_{N_{1}}$ , the lightest active neutrino mass and the primordial lepton asymmetry $ε_{1}$ on the one hand, and the $β β_{0 ν}$ decay parameter $m_{ee}$ on the other hand. {\it However, leptogenesis is insensitive to the neutrino oscillation phase}. We find lower bounds $M_{N_1}\gsim 10^{10}$ GeV for the normal light-neutrino mass hierarchy, and $M_{N_1}\gsim 10^{11}$ GeV for the inverted mass hierarchy, respectively, indicating a potentially serious conflict with the gravitino problem. Depending on $M_{N_{1}}$ , we find upper (upper and lower bounds) on the lightest active neutrino mass for the normal (inverted) mass hierarchy, and a lower bound on $m_{ee}$ even for the normal mass ordering. The low-energy lepton-flavour- and CP-violating observables induced by renormalization are almost independent of leptogenesis. The electron electric dipole moment may be close to the present bound, reaching $d_{e} \sim 1 0^{- (27 - 28)}$ e cm in our numerical examples, while $d_{μ}$ may reach $d_{μ} \sim 1 0^{- 25}$ e cm.

23 pages, 12 postscript figures

Leptogenesis and the Violation of Lepton Number and CP at Low Energies

Abstract

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