Supernova Relic Neutrino search with neutron tagging at Super-Kamiokande-IV

A search for Supernova Relic Neutrinos ν¯e’s is first conducted via inverse-beta-decay by tagging neutron capture on hydrogen at Super-Kamiokande-IV. The neutron tagging efficiency is determined to be (17.74±0.04stat.±1.05sys.)%(17.74±0.04stat.±1.05sys.)%, while the corresponding accidental background probability is (1.06±0.01stat.±0.18sys.)%(1.06±0.01stat.±0.18sys.)%. Using 960 days of data, we obtain 13 inverse-beta-decay candidates in the range of Eν¯e between 13.3 MeV and 31.3 MeV. All of the observed candidates are attributed to background. Upper limits at 90% C.L. are calculated in the absence of a signal.