Upper limits on the diffuse supernova neutrino flux from the SuperKamiokande data

We analyze the 1496 days of SuperKamiokande data to put limits on the νe, ν̄e, νμ + ντ and ν̄μ + ν̄τ components of the diffuse flux of supernova neutrinos, in different energy intervals and for different neutrino energy spectra. By considering the presence of only one component at a time, we find the following bounds at 90% C.L. and for neutrino energy E > 19.3 MeV: Φνe < 73.3 − 154 cm−2s−1, Φν̄e < 1.4 − 1.9 cm−2s−1, Φνμ+ντ < (1.0 − 1.4) · 103 cm−2s−1 and Φν̄μ+ν̄τ < (1.3 − 1.8)·103 cm−2s−1, where the intervals account for varying the neutrino spectrum. In the interval E = 22.9− 36.9 MeV, we find Φνe < 39− 54 cm−2s−1, which improves on the existing limit from SNO in the same energy window. Our results for νμ + ντ and ν̄μ + ν̄τ improve by about four orders of magnitude over the previous best constraints from LSD.