(Down-to-)Earth matter effect in supernova neutrinos

TL;DR

This study assesses the detectability of Earth matter effects in supernova neutrino spectra using next-generation detectors, finding that such effects are challenging to observe except for very nearby supernovae due to lower neutrino energies and flux equalization.

Contribution

The paper provides an updated analysis of the observability of Earth matter effects in supernova neutrinos with next-generation detectors, considering recent flux predictions and statistical fluctuations.

Findings

Detection is unlikely for typical galactic supernovae at 10 kpc.

Earth effects could be observed in a 100 kton liquid Argon detector for supernovae within a few kpc.

Detection is feasible only for very close supernovae (~0.2 kpc) across all considered detectors.

Abstract

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 and accounting for statistical fluctuations via Montecarlo simulations. Since the average energies predicted by recent simulations are lower than previously expected and a tendency towards the equalization of the neutrino fluxes appears during the SN cooling phase, the detection of the Earth matter effect will be more challenging than expected from previous studies. We find that none of the proposed detectors shall be able to detect the Earth modulation for the neutrino signal of a typical galactic SN at 10 kpc. It should be observable in a 100 kton liquid Argon detector for a SN at few kpc and all three detectors would clearly see the Earth signature for very close-by stars only (d ~ 0.2 kpc). Finally, we show that adopting IceCube as co-detector together with a Mton water Cherenkov detector is not a viable option either.