Supernova relic neutrinos and observational implications for neutrino oscillation

Abstract

We investigate the flux of supernova relic neutrinos (SRN) for several neutrino oscillation models with parameters inferred from recent experimental results. In the calculation, we adopt the realistic {\it time-dependent} supernova density profile, which is very different from the static progenitor profile owing to shock propagation. The Earth matter effect is also included appropriately using realistic density profile of the Earth. As a result, these two effects are found to induce the flux difference by a few % in the detection energy range ($E_\nu > 19.3$ MeV). We also set 90% C.L. upper limit on SRN flux for various oscillation models using the recently released observational result by Super-Kamiokande (SK). In the near future, further reduced upper limit is actually expected, when the current SK data are reanalyzed using some technique to reduce background events against SRN signals. It is expected that the reduced upper limit is sufficient to provide useful implications for neutrino oscillation.