Diffuse supernova neutrino background (DSNB), which is an integrated flux of neutrinos from all past core-collapse supernovae (CCSNe), are eagerly studied in the worldwide experiment because the detection of DNSB flux makes investigation about the star formation history as well as the neutrino emission from CCSNe.
Since 2020, Super-Kamiokande (SK) detector has been updated by loading gadolinium (Gd) as a new experimental phase, “SK-Gd”. In the SK-Gd experiment, neutrons can be efficiently identified due to high cross-section and high energy gamma-ray emission of thermal neutron capture on Gd. This enables to search low-energy electron antineutrinos such as a signal of DSNB via inverse-beta decay.
Until July 2022, the observation was operated with the 0.01% Gd mass concentration, termed as SK-VI. The neutron capture fraction on Gd is about 50% at that time. In this period, we operated neutron source calibration and obtained characteristics about the neutron identification in SK-Gd detector.
Using the whole period of SK-VI, we searched for astrophysical electron antineutrinos with the energy of O(10) MeV in SK-Gd with a 22.5×552 kton·day exposure at 0.01% Gd mass concentration for a first time in SK-Gd experiment.
This seminar provides the result of the search and prospects for future observation.