Identifying Earth matter effects on supernova neutrinosat a single detector

Abstract

The neutrino oscillations in Earth matter introduce modulations in thesupernova neutrino spectra. These modulations can be exploited toidentify the presence of Earth effects on the spectra, which wouldenable us to put a limit on the value of the neutrino mixing angleθ13 and to identify whether the mass hierarchy is normal orinverted. We demonstrate how the Earth effects can be identified at asingle detector without prior assumptions about the flavour-dependentsource spectra, using the Fourier transform of the `inverse-energy'spectrum of the signal. We explore the factors affecting theefficiency of this method, and find that the energy resolution of thedetector is the most crucial one. In particular, whereas waterCherenkov detectors may need a few ten thousand events to identify theEarth effects, a few thousand may be enough at scintillationdetectors, which generically have a much better energy resolution. Asuccessful identification of the Earth effects through this method canalso provide Δm2⊙ to a good accuracy. The relativestrength of the detected Earth effects as a function of time providesa test for supernova models.