When searching for supernova relic neutrinos (SRN), the candidate neutrino event can be detected through an inverse beta decay (IBD) reaction in a water Cherenkov detector, such as the Super-Kamiokande experiment. The signal from this reaction consists of a prompt signal from the positron and the delayed neutron capture signal. Neutral current quasi-elastic (NCQE) interactions of atmospheric neutrinos form a significant background for this SRN search, as the prompt and delayed signal of the NCQE interaction mimics that of the SRN.
Previously the NCQE neutron tag has searched for the 2.2 MeV photon from neutron capture on hydrogen. With the recent addition of 0.026% gadolinium sulphate octahydrate to Super-Kamiokande, this allows for improved neutron detection due to the higher energy gamma cascade signal of neutron capture on gadolinium of 8 MeV.
At energies close to the atmospheric peak, the NCQE interaction cross sections can be evaluated using T2K beam neutrinos. This poster will present the status of the improved neutron tag from SK-Gd, its impact on the measurement of NCQE in T2K and the improvements to the SRN background measurement.