Decoupling supernova and neutrino oscillation physics with LAr TPC detectors

Abstract

Core collapse supernovae are a huge source of all flavour neutrinos. The flavourcomposition, energy spectrum and time structure of the neutrino burst from a galacticsupernova can provide information about the explosion mechanism and the mechanisms ofproto neutron star cooling. Such data can also give information about the intrinsicproperties of the neutrino such as flavour oscillations. One important question isto understand to what extent the supernova and the neutrino physics can bedecoupled in the observation of a single supernova. On one hand, the understandingof the supernova explosion mechanism is still plagued by uncertainties whichhave an impact on the precision with which one can predict time-, energy- andflavour-dependent neutrino fluxes. On the other hand, the neutrino mixing propertiesare not fully known, since the type of mass hierarchy and the value of theθ13 angle are unknown, and in fact large uncertainty still exists on the prediction ofthe actual effect of neutrino oscillations in the event of a supernova explosion.In this paper we discuss the possibility of probing the neutrino mixing angleθ13 and the type of mass hierarchy from the detection of supernova neutrinos with a liquidargon TPC detector. Moreover, describing the supernova neutrino emission by a set of fiveparameters (average energy of the different neutrino flavours, their relative luminosity andthe total supernova binding energy), we quantitatively study how it is possible to constrainthese parameters. A characteristic feature of the liquid argon TPC is the accessibility tofour independent detection channels ((1) elastic scattering off electrons, (2) chargedneutrino and (3) antineutrino and (4) neutral currents on argon nuclei) which have differentsensitivities to electron neutrino, anti-electron neutrino and other neutrino flavours (muonand tau (anti)neutrinos). This allows us to over-constrain the five supernova andthe flavour mixing parameters and to some extent disentangle neutrino fromsupernova physics. Numerically, we find that a very massive liquid argon detector(O(100 kton)) is needed to perform accurate measurements of these parameters, speciallyin supernova scenarios where the average energies of electron and non-electronneutrinos are similar (almost degenerate neutrinos) or if no information about theθ13 mixing angle and type of mass hierarchy is available.