Hyper-Kamiokande (HK) is the next generation water Cherenkov detector being constructed in Japan, following in the footsteps of the very successful Kamiokande, Super-Kamiokande and T2K experiments. The HK far detector (258\,kton) is planned to be instrumented with 20,000 50\,cm diameter photomultiplier tubes (PMTs) and about 1,000 multi-PMT optical sensors (each containing 19 7.6\,cm PMTs) looking inwards at the detector and around 3,600 PMTs of 7.6\,cm diameter looking outwards to veto cosmic radiation and other backgrounds. The design and construction of the detector is at an advanced stage. HK is expected to be commissioned in 2027. The experiment will also count with an Intermediate Water Cherenkov Detector (IWCD) at a site approximately 900\,m from the target used to produce neutrino beams at the J-PARC accelerator facility, while the HK far detector is located 295\,km away. The main physics goals of the experiment are to significantly improve the precision of neutrino oscillation measurements using the upgraded J-PARC neutrino beam, including the potential discovery of CP violation in the leptonic sector of the Standard Model, measurement of neutrino oscillation parameters, neutrinos from astrophysical sources, such as cosmic rays, solar neutrinos and neutrinos originating from supernovae, and a world-leading search for proton decay. The design of the HK far and intermediate water Cherenkov detectors, the status of their construction and the expected physics capabilities of the experiment will be described.

Research supported by a Leverhulme Trust Research Fellowship