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Figure 3: Super-Kamiokande Detector. Super Kamiokande is the worldʼs largest underground neutrino detector, and is located 1000 metres underground in Kamioka Mine, Hida, Gifu Precture, Japan. It is affiliated with the Kamioka Observatory of the Institute of Cosmic Ray Research at the University of Tokyo. In addition to detecting T2K neutrinos, Super Kamiokande observes neutrinos produced by collisions between cosmic rays and molecules in the Earthʼs upper atmosphere. It is also searching for proton decays, which have never been observed to date. Super Kamiokande consists of a large cylinder 39.3 metres in diameter and 41 metres high that contains 50,000 tons of ultra-pure water. The inner walls of the cylinder are lined with about 11,200 photomultiplier tubes to detect Cerenkov light, which is emitted when a charged particle travels faster than the speed of light in water (this is three quarters of its speed in vacuum).