Enhancement of the Transition Magnetic Moments of a Neutrino by Degenerate Electrons

The one-loop induced magnetic dipole moments of a neutrino are examined in a background of degenerate electrons in the standard model. For the nonrelativistic neutrino, these moments are enhanced by a factor (8p F /3m ν), where p F is the electron Fermi momentum and m ν the neutrino mass. For the relativistic neutrino, they enhance the flavor-changing but helicity-conserving process due to the absence of the GIM cancellation.