Dr. Takaaki Kajita

Dr. Takaaki Kajita studied about "Atmospheric Neutrino" born from collision between cosmic rays and the atmosphere using Super Kamiokande, then, received the Nobel Prize in Physics.
The research team that Dr. Kajita participated proved that the atmosphere neutrino oscillates for the first time in the world. The fact that the neutrino oscillates indicates that its properties periodically change. In other words, it means that the neutrino has mass. It is a phenomenon which can not be explained by the knowledge of physics so far.
The discovery proving the neutrino oscillation contributed to greatly widening human knowledge about nature and the universe.