Proposal for A Water Cherenkov Test Beam Experiment for Hyper-Kamiokande andFuture Large-scale Water-based Detectors

Here we propose a 50 ton scale Water Cherenkov test experiment (WCTE) to be deployed in an East Area test beam line. The experiment will include a secondary target located just upstream of the experiment in order to produce very low energy particle fluxes, including charged pions. The WCTE program will be carried out with the following objectives. We will operate and understand the performance of new detector technologies such as multi-PMTs, and in a possible future phase, dichroicon wavelength-separating cones and water-based liquid scintillator in a fully integrated detector. We will study the performance of a <1 kiloton scale water Cherenkov detector with known particle fluxes, and test and develop calibration systems necessary for accurate modeling of a detector of this size. We will measure important physics processes for the modeling of water Cherenkov detector responses, including high-angle Cherenkov light production, pion scattering and absorption, and secondary neutron production in hadron scattering. We aim to start operation of the water Cherenkov test experiment in 2022.