Neutrino mass spectrum from gravitational waves generated by double neutrino spin-flip in supernovae

Abstract

The supernova (SN) neutronization phase produces mainly electron ($\nu_e$) neutrinos, the oscillations of which must take place within a few mean-free-paths of their resonance surface located nearby their neutrinosphere. The state-of-the-art on the SN dynamics suggests that a significant part of these $\nu_e$ can convert into right-handed neutrinos in virtue of the interaction of the electrons and the protons flowing with the SN outgoing plasma, whenever the Dirac neutrino magnetic moment be of strength $\mu_\nu < 10^{-11} \mu_{\rm B}$, with $\mu_{\rm B}$ being the Bohr magneton. In the supernova envelope, part of these neutrinos can flip back to the left-handed flavors due to the interaction of the neutrino magnetic moment with the magnetic field in the SN expanding plasma (Kuznetsov & Mikheev 2007; Kuznetsov, Mikheev & Okrugin 2008), a region where the field strength is currently accepted to be $B \gtrsim 10^{13}$ ~G. This type of $\nu$ oscillations were shown to generate powerful gravitational wave (GW) bursts (Mosquera Cuesta 2000, Mosquera Cuesta 2002, Mosquera Cuesta & Fiuza 2004, Loveridge 2004). If such double spin-flip mechanism does run into action inside the SN core, then the release of both the oscillation-produced $\nu_\mu$s, $\nu_\tau$s and the GW pulse generated by the coherent $\nu$ spin-flips provides a unique emission offset $\Delta T^{emission}_{\rm GW} \leftrightarrow \nu = 0$ for measuring the $\nu$ travel time to Earth. As massive $\nu$s get noticeably delayed on its journey to Earth with respect to the Einstein GW they generated during the reconversion transient, then the accurate measurement of this time-of-flight delay by SNEWS + LIGO, VIRGO, BBO, DECIGO, etc., might readily assess the absolute $\nu$ mass spectrum.