Radiative Majorana Neutrino Masses

Abstract

We present new radiative mechanisms for generating Majorana neutrino masses, within an extension of the standard model that successfully generates radiative charged lepton masses, order by order, from heavy sequential leptons. Only the new sequential neutral lepton has a right-handed partner, and its Majorana mass provides the seed for Majorana neutrino mass generation. Saturating the cosmological bound of $50$ eV with $m_{\nu_\tau}$, we find that $m_{\nu_\mu}$ and $m_{\nu_e}$ could be at most $10^{-2}$, and $10^{-3}$ eV, respectively. The electron neutrino mass may vanish in the limit of degenerate charged Higgs bosons. Unfortunately, $\nu_e - \nu_\tau$ mixing is also radiatively induced, and is too small for sake of solving the solar neutrino problem via the Mikheyev--Smirnov--Wolfenstein effect.