P - PH - 9 50 63 85 Cerenkov radiation by neutrinos in a supernova core

Neutrinos with a magnetic dipole moment propagating in a medium with a velocity larger than the phase velocity of light emit photons by the Cerenkov process. The Cerenkov radiation is a helicity ip process via which a lefthanded neutrino in a supernova core may change into a sterile right-handed one and free-stream out of the core. Assuming that the luminosity of the sterile right-handed neutrinos is less than 10 ergs/sec gives an upper bound on the neutrino magnetic dipole moment < 0:5 10 13 B . This is two orders of magnitude more stringent than the previously established bounds on from considerations of supernova cooling rate by right-handed neutrinos. E-mail:[email protected] E-mail:[email protected] PRL-TH-95/10 June 1995