Super-Kamiokande is the world largest water Cherenkov detector which diameter and height are about 40 meter, and located under the Ikeno-Yama mountain in Gifu prefecture of Japan. Since the experiment started in 1996, it has brought significant progress in several fields of neutrino physics (solar neutrino, atmospheric neutrino, accelerator neutrino, super-nova neutrino) and nucleon decay search.
Our group has participated mainly in the analysis group of the atmospheric neutrinos, and produced several physics results such as neutrino oscillation analysis. In future, we are aiming at determining the hierarchy of neutrino mass by means of the atmospheric neutrinos.
T2K (Tokai-To-Kamioka) experiment aims at precise measurement of muon neutrino disappearance, and electron neutrino appearance driven by non-zero theta_13 mixing angle in neutrino oscillation parameter. Muon neutrino beam is produced at J-PARC accerlerator facility in Tokai village of Ibaraki prefecture, and its oscillation effect is measured at Super-Kamiokande detector which is located 295 kilo meter away from J-PARC. Using narrow band beam, it is possible to measure electron appearance events with high sensitivity by reducing hadronic backgrounds due to high energy interactions.
Our group is contributing to the analysis of beam events detected at Super-Kamiokande detector, and also oscillation analysis especially for electron appearance.
We have not yet revealed the whole feature of neutrino. Especially, CP (Charge and Parity) violation in lepton sector is one of the most important subjects to be solved in particle physics. Hyper-Kamiokande project, which detector can measure more neutrino events using its huge mass by factor of 25 compared to Super-Kamiokande, is expected to make progress in revealing the unknown properties of neutrino.
Several R&D works are going, such as detector design, simulations, etc. Our group also takes part in Hyper-Kamiokande project, and contributes to, for example, photo-sensors development.