| A search for the relic neutrinos from all past core-collapse supernovae was conducted using 1496 days of data from the Super-Kamiokande-I detector. This analysis searched for electron-type anti-neutrino interactions that produce a positron with an energy greater than 18 MeV. No appreciable signal for such interactions was found. In the absence of a signal, 90% C.L. upper bounds on the total flux were set for several theoretical models; the limits ranged from 20 to 130 νe cm −2 s−1. These results are a factor of 40 times better than the best limits set in previous experiments, and they can eliminate certain models. Additionally, a modelinsensitive upper bound of 1.2 νe cm −2 s−1 was obtained for the supernova relic neutrino flux in the energy region Eν > 19.3 MeV. This limit is two orders of magnitude more stringent than the best previous limit. |
