Generic lepton mass matrices and neutrino oscillations

Abstract

Several intriguing aspects of neutrino oscillation phenomenology like the origin of small neutrino masses, the absolute neutrino mass scale, the neutrino mass hierarchy, i.e., normal or inverted, and the nature of neutrinos, i.e., Dirac or Majorana, etc. have been addressed from a general perspective. We show how the fundamental considerations of unitary transformations, naturalness, and the seesaw mechanism suffice to determine the texture structure of fermion Yukawa couplings and discuss the significance of the effective mass in $0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$ decay for the texture structure of these couplings.