Resonant spin-flavor precession of solar and supernova neutrinos

Abstract

The combined effect of matter and magnetic fields on neutrino spin and flavor precession is examined. We find a potential new kind of resonant or (for Dirac neutrinos) or ${\ensuremath{\nu}}_{e}$\ensuremath{\rightarrow}\ensuremath{\nu}${\ifmmode\bar\else\textasciimacron\fi{}}_{\ensuremath{\mu}}$ or \ensuremath{\nu}${\ifmmode\bar\else\textasciimacron\fi{}}_{\ensuremath{\tau}}$ (for Majorana neutrinos). Such a resonance could help account for the lower than expected solar-neutrino ${\ensuremath{\nu}}_{e}$ flux and/or indications of an anticorrelation between fluctuations in the ${\ensuremath{\nu}}_{e}$ flux and sunspot activity. Consequences of spin-flavor precession for supernova neutrinos are also briefly discussed.