Neutrino is one of the elementary particles, but its basic properties, like mass, are not fully understood yet. Since the 1970s , neutrino has been considered as a mass-less particle in the standard model of elementary particle physics. However, the Super-Kamiokande experiment found the first experimental evidence of the finite neutrino mass in 1988, by observing “neutrino oscillation” phenomena precisely, which only massive neutrinos can provide. Then, theoretical and experimental researches on neutrino drew attention, and active researches on neutrino are still on going in the world today. In the field of experimental neutrino oscillation research, Japanese projects have continued to lead the world so far, through Super-Kamiokande, K2K, KamLAND, and T2K experiments.
Currently, neutrino is one of important clues to build the new particle physics theory beyond the standard model, to unravel the mystery of the creation of our present matter dominant Universe, and so on. In our Particle Physics group, we are trying to understand the basic properties of the neutrinos, then to contribute to understand these mysteries in physics and astrophysics, through the Super-Kamiokande, T2K, and Double Chooz experiments.