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 nu(e), (nu) over bar (e), nu(mu) + nu(tau) and (nu) over bar (mu) + (nu) over bar (tau) 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% CL and for neutrino energy E > 19.3 MeV: Phi(nu e) < 73.3-154 cm(-2) s(-1), Phi((nu) over bare) < 1.4-1.9 cm(-2) s(-1), Phi(nu mu +nu tau) < (1.0-1.4) x 10(3) cm(-2) s(-1) and Phi((nu) over bar mu+($) over bar tau) < (1.3-1.8) x 10(3) cm(-2) s(-1), where the intervals account for varying the neutrino spectrum. In the interval E = 22.9-36.9 MeV, we find Phi(nu e) < 39-54 cm(-2) s(-1), which improves on the existing limit from SNO in the same energy window. Our results for nu(mu)+nu(tau) and (nu) over bar (mu) + (nu) over bar (tau) improve by about four orders of magnitude the previous best constraints from LSD.