T2K is an accelerator based long baseline neutrino oscillation experiment taking data since 2010 in Japan. The neutrino beam is produced at the J-PARC accelerator complex and neutrinos are detected in a Near Detector complex (ND280) before the oscillations and at the Far Detector (Super-Kamiokande) after the oscillations.
T2K was the first experiment to measure oscillations in the appearance channel and, as it will be shown in this seminar, is now observing first hints of CP violation in the leptonic sector by comparing appearance probabilities of electron neutrinos and antineutrinos.
Such hints are currently limited by statistical uncertainties and T2K is now entering its second phase (T2K-II) consisting in an upgrade of the accelerator complex and of ND280. Such upgrades are expected to be operational in 2022 and will allow to establish CP violation at more than 3 sigma with T2K-II if CP is maximally violated in neutrino oscillations.
T2K-II will be followed by Hyper-K, a Water Cherenkov detector 8 times larger than Super-K. Hyper-K will use the same accelerator complex and near detectors of T2K and it is expected to start data taking in 2027.
Thanks to its large size, Hyper-K will have unprecedented sensitivity to CP violation and to the proton decay and it will be a powerful observatory for atmospheric and solar neutrinos and for neutrinos emitted in supernovae explosions.