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, they are enhanced by a factor \( (8\pF/3\mnu) \), where \pF\ is the electron Fermi momentum and \mnu\ the neutrino mass. For the relativistic neutrino, they enhance the flavor-changing but helicity-conserving process because of the absence of the GIM cancellation.