Detecting the neutrino mass hierarchy with a supernovaat IceCube

Abstract

IceCube, a future km3 antarctic ice Cherenkov neutrino telescope,is highly sensitive to a galactic supernova (SN) neutrino burst. TheCherenkov light corresponding to the total energy deposited by the SNneutrinos in the ice can be measured relative to backgroundfluctuations with a statistical precision much better than 1%. If theSN is viewed through the Earth, the matter effect on neutrinooscillations can change the signal by more than 5%, depending on theflavour-dependent source spectra and the neutrino mixing parameters.Therefore, IceCube together with another high-statistics experimentlike Hyper-Kamiokande can detect the Earth effect, an observation that would identify specific neutrino mixing scenarios that are difficult to pin down with long-baseline experiments. In particular, the normal mass hierarchy can be clearly detected if the third mixing angle is not too small, sin2θ13≳10−3. The small flavour-dependentdifferences of the SN neutrino fluxes and spectra that are found instate-of-the-art simulations suffice for this purpose. Although theabsolute calibration uncertainty at IceCube may exceed 5%, the Eartheffect would typically vary by a large amount over the duration of theSN signal, obviating the need for a precise calibration. Therefore,IceCube with its unique geographic location and expected longevity canplay a decisive role as a `co-detector' to measure SN neutrinooscillations. It is also a powerful stand-alone SN detector that canverify the delayed-explosion scenario.