Neutrino signatures of supernova forward and reverse shock propagation

Abstract

A few seconds after bounce in a core-collapse supernova, the shock wave passes the densityregion corresponding to resonant neutrino oscillations with the ‘atmospheric’ neutrino massdifference. The transient violation of the adiabaticity condition manifests itself in anobservable modulation of the neutrino signal from a future galactic supernova. In additionto the shock wave propagation effects that were previously studied, a reverse shock formswhen the supersonically expanding neutrino-driven wind collides with the slower earliersupernova ejecta. This implies that for some period the neutrinos pass two subsequentdensity discontinuities, giving rise to a ‘double-dip’ feature in the average neutrino energyas a function of time. We study this effect both analytically and numerically and findthat it allows one to trace the positions of the forward and reverse shocks. Weshow that the energy dependent neutrino conversion probabilities allow one todetect oscillations even if the energy spectra of different neutrino flavours are thesame as long as the fluxes differ. These features are observable in the signal for an inverted and in theνe signal for a normal neutrino mass hierarchy, provided the 13-mixing angle is ‘large’ ().