Dirac neutrino masses with Planck scale lepton number violation
PHYSICAL REVIEW LETTERS | AMER PHYSICAL SOC | Published : 2004
It is shown how pure Dirac neutrino masses can naturally occur at low energies even in the presence of Planck scale lepton number violation. In a 5D setting this is achieved by explicitly breaking the lepton number on the Planck brane while the right-handed neutrino is localized on the TeV brane. A small wave function overlap then naturally leads to a small Dirac Yukawa coupling. In the 4D dual description the right-handed neutrino is identified as a composite CFT bound state and lepton number violation is highly suppressed by CFT operators with large anomalous dimensions.