Flavor-Changing Magnetic Dipole Moment and Oscillation of a Neutrino in a Degenerate Electron Plasma

The standard model prediction for a magnetic dipole moment of a neutrino is proportional to the neutrino mass and extremely small. It also generates a flavor-changing process, but the GIM mechanism reduces the corresponding amplitude. These properties of a neutrino magnetic moment change drastically in a degenerate electron plasma. We have shown that an electron-hole excitation gives a contribution proportional to the electrons' Fermi momentum. Since this effect is absent in \(\mu\) and \(\tau\) sector, the GIM cancellation does not work. The magnetic moment induces a neutrino oscillation if a strong enough magnetic field exists in the plasma. The required magnitude of the field strength that affects the \nue\ burst from a supernova is estimated to be the order of \(10^8 \) Gauss.