Tuesday, July 24, 2012

1207.5049 (Enrico Borriello et al.)

(Down-to-)Earth matter effect in supernova neutrinos    [PDF]

Enrico Borriello, Sovan Chakraborty, Alessandro Mirizzi, Pasquale Dario Serpico, Irene Tamborra
Neutrino oscillations in the Earth matter may introduce peculiar modulations in the supernova (SN) neutrino spectra. The detection of this effect has been proposed as diagnostic tool for the neutrino mass hierarchy at "large" 1-3 leptonic mixing angle theta13. We perform an updated study on the observability of this effect at large next-generation underground detectors (i.e., 0.4 Mton water Cherenkov, 50 kton scintillation and 100 kton liquid Argon detectors) based on neutrino fluxes from state-of-the-art SN simulations. The average energies predicted by recent simulations are lower than previously expected and a tendency towards the equalization of the neutrino fluxes of the different flavors during the SN cooling phase appears. As a consequence, the detection of the Earth matter effect should be more challenging than expected from previous studies. In particular, for a typical galactic SN at 10 kpc, none of the proposed detectors may be able to detect the Earth modulation in the SN neutrino signal. Due to larger differences in neutrino (as opposed to antineutrino) energies and fluxes, in a 100 kton liquid Argon detector the Earth effect becomes observable at few kpc. Only for very close-by stars, that could evolve in SNe (like Betelgeuse at 0.2 kpc) all three detectors would clearly see the Earth signature. Finally, taking Icecube as co-detector together with a Mton water Cherenkov detector to monitor the Earth effect, it is not able to detect any sizable variation in the SN neutrino event rate for any galactic supernova.
View original: http://arxiv.org/abs/1207.5049

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