Diffuse supernova neutrino background search at Super-Kamiokande

We have conducted a new search for the diffuse supernova neutrino background (DSNB) flux at Super-Kamiokande (SK), with 22.5×2970?kton·day exposure from its fourth operational phase IV. With analysis we improve on existing reduction techniques and systematic uncertainties take advantage of an improved neutron tagging algorithm to lower energy threshold compared previous phases SK. This allows setting world’s most stringent upper limit extraterrestrial ?¯e flux, energies below 31.3 MeV. The SK-IV results are combined ones first three SK perform joint using 22.5×5823 kton·days data. has best sensitivity DSNB comparable predictions various models. For larger than 17.3 MeV, 90% CL limits lie around 2.7 cm?2·sec?1, strongly disfavoring optimistic predictions. Finally, potentialities gadolinium future Hyper-Kamiokande experiment discussed.30 MoreReceived 24 September 2021Accepted 2 November 2021DOI:https://doi.org/10.1103/PhysRevD.104.122002© 2021 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasExtrasolar astronomyParticles & FieldsGravitation, Cosmology Astrophysics