The Seesaw with Many Right-Handed Neutrinos

Abstract

There are no upper limits on the possible number of massive, singlet (right--handed) neutrinos that may participate in the seesaw mechanism, and some string constructions motivate seesaw models with up to O(100) right--handed neutrinos. In this case, the seesaw mass scale can be significantly higher than that in the traditional scheme with just 3 right--handed neutrinos. We consider the possible phenomenological implications of such models, in particular, for lepton-flavour violation and electric dipole moments. Since the neutrino masses depend on the Majorana mass scale linearly, while supersymmetric loop corrections depend on it logarithmically, the magnitude of lepton-flavour- and CP-violating transitions may increase with the multiplicity of the right--handed neutrinos and may be enhanced by orders of magnitude. We also point out that, in the context of leptogensis, the bounds on the reheating temperature and the lightest neutrino mass get relaxed compared to those in the case of 3 right--handed neutrinos.

14 pages; refs. added, published version

References in corpus (6)

• Neutrino physics overview
• Neutrino Mass and New Physics
• Seesaw Neutrinos from the Heterotic String
• Supersymmetric Jarlskog Invariants: the Neutrino Sector
• Leptogenesis With Many Neutrinos
• Observable Electron EDM and Leptogenesis

Cited by in corpus (10)

• Leptogenesis
• SU(N) gauge theories at large N
• The Heterotic Road to the MSSM with R parity
• From strings to the MSSM
• Monochromatic neutrinos generated by dark matter and the see-saw mechanism
• Seesaw parametrization for n right-handed neutrinos
• Effective Lagrangian approach to fermion electric dipole moments induced by a CP--violating $WW\gamma$ vertex
• Sterile neutrino dark matter: relativistic freeze-out
• Branon stabilization from fermion-induced radiative corrections
• Stringy surprises