A Water Cherenkov Test Beam Experiment for Hyper-Kamiokande and Future Large-scale Water-based Detectors

Water Cherenkov and water-based particle detector technologies are used to realize multi-kiloton scale experiments such as the currently operating Super-Kamiokande experiment, the planned Hyper-Kamiokande experiment and the proposed THEIA detector and ESSnuSB detectors. These experiments are operated or proposed to study a broad range of physics including neutrino oscillations, nucleon decay, dark matter and neutrinoless double beta decay. The neutrino oscillations program will also include kiloton scale near or intermediate detectors used to study neutrino production and interactions in the absence of neutrino oscillations, such as the Hyper-K Intermediate Water Cherenkov Detector (IWCD). Realization of these physics programs will require new detector technologies and percent level calibration of detector responses and models of physics processes within the detector. Here we describe our intent to propose a 50~ton scale Water Cherenkov test experiment (WCTE) to be deployed in a North or East test beam experimental area. 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: - Operate and understand the performance of new detector technologies such as multi-PMTs, dichroicon wavelength-separating cones and water-based liquid scintillator in a fully integrated detector. - 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. - 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 2021-2022

Introducing the CTA concept

The Cherenkov Telescope Array (CTA) is a new observatory for very high-energy (VHE) gamma rays. CTA has ambitions science goals, for which it is necessary to achieve full-sky coverage, to improve the sensitivity by about an order of magnitude, to span about four decades of energy, from a few tens of GeV to above 100 TeV with enhanced angular and energy resolutions over existing VHE gamma-ray observatories. An international collaboration has formed with more than 1000 members from 27 countries in Europe, Asia, Africa and North and South America. In 2010 the CTA Consortium completed a Design Study and started a three-year Preparatory Phase which leads to production readiness of CTA in 2014. In this paper we introduce the science goals and the concept of CTA, and provide an overview of the project