Profiling calibration devices and simulating cosmic-ray muon spallation for Hyper-Kamiokande

Neutrinos are produced in many places, with the most explosive being core-collapse supernovae. Owing to their low chance of interacting, it is expected that the majority of the neutrinos produced in this way still exist and should be able to be detected by modern neutrino observatories such as Super- and Hyper-Kamiokande. However, efforts to detect such a signal have been hampered by overwhelming backgrounds.
One such background is the low-energy events caused by the spallation of nuclei by cosmic-ray muon interactions. A spallation simulation chain has been developed for the Hyper-Kamiokande experiment, which uses FLUKA to simulate the complex spallation interactions and the water Cherenkov simulation (WCSim) framework to simulate the detector’s response to these interactions.
The result of the simulations is a machine learning classification which classifies between DSNB events and spallation-induced low-energy events. The results of this classification are a promising indication of the best possible performance of a classifier being approximately 98% in both background rejection and signal efficiency.
An underwater profiling system used to measure precision profiles of calibration devices for use in Hyper-Kamiokande has also been developed. Two types of calibration devices have been developed: collimators and diffusers. The system has successfully measured the profiles of a number of both types of calibration devices and has contributed towards the development of the devices by investigating their compatibility with long-term submersion in ultra-pure water.
Finally, an updated analysis of data collected with a high-purity germanium detector was developed to aid in the 2023 linear accelerator calibration campaign of the Super-Kamiokande detector. This included the calibration of the germanium detector using multiple radioactive sources, the simulation of the detector’s response to sub-20MeV electrons, and a χ2 analysis to determine the energy of electrons produced by the linear accelerator.