Bound on the neutrino magnetic moment from chirality flip in supernovae

Abstract

For neutrinos with a magnetic moment, we show that the collisions in a hot and dense plasma act as an efficient mechanism for the conversion of ${\ensuremath{\nu}}_{L}$ into ${\ensuremath{\nu}}_{R}.$ The production rate for right-handed neutrinos is computed in terms of a resummed photon propagator which consistently incorporates the background effects. Assuming that the entire energy in a supernova collapse is not carried away by the ${\ensuremath{\nu}}_{R},$ our results can be used to place an upper limit on the neutrino magnetic moment ${\ensuremath{\mu}}_{\ensuremath{\nu}}<(0.1--0.4)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}{\ensuremath{\mu}}_{B}.$