Neutrino masses from new generations

Abstract

We reconsider the possibility that Majorana masses for the three known neutrinos are generated radiatively by the presence of a fourth generation and one right-handed neutrino with Yukawa couplings and a Majorana mass term. We find that the observed light neutrino mass hierarchy is not compatible with low energy universality bounds in this minimal scenario, but all present data can be accommodated with five generations and two right-handed neutrinos. Within this framework, we explore the parameter space regions which are currently allowed and could lead to observable effects in neutrinoless double beta decay, $\mu -e$ conversion in nuclei and $\mu \to e\gamma$ experiments. We also discuss the detection prospects at LHC.

28 pages, 4 figures. Version to be published. Some typos corrected. Improved figures 3 and 4

References in corpus (11)

• Massive neutrinos and cosmology
• Double Beta Decay, Majorana Neutrinos, and Neutrino Mass
• Phenomenology with Massive Neutrinos
• Unitarity of the Leptonic Mixing Matrix
• Signatures for Majorana neutrinos at hadron colliders
• Heavy Majorana Neutrinos in the Effective Lagrangian Description: Application to Hadron Colliders
• pi/K -> e nu branching ratios to O(e^2 p^4) in Chiral Perturbation Theory
• The smallest neutrino mass
• Long Lived Fourth Generation and the Higgs
• Tau Physics: Theory Overview
• Fourth Family Neutrinos and the Higgs Boson