Detecting the diffuse supernova neutrino background with LENA

Low energy neutrino astronomy (LENA) has been proposed as a next generation 50 kt liquid scintillator detector. Its large target mass allows us to search for the diffuse supernova neutrino background (DSNB), which was generated by the cumulative emissions of all core-collapse supernovae throughout the Universe. Indistinguishable background from reactor and atmospheric electron antineutrinos limits the detection window to the energy range between 9.5 MeV and 25 MeV. Depending on the mean supernova neutrino energy, about 5 to 10 events per year are expected in this energy window. The background from neutral current reactions of atmospheric neutrinos surpasses the DSNB by more than one order magnitude, but can be suppressed by pulse shape discrimination. Assuming that the residual background is known with 5% uncertainty, the DSNB can be detected with 3σ significance after 10 years of data taking. In case no hint for a signal is seen, the allowed parameter space of DSNB models would be substantially constrained and the currently favored predictions for spectral mean energy and supernova rate would be excluded with more than 90% C.L.