Takaaki Kajita
Early life and education. Kajita was born in 1959 in Higashimatsuyama, Saitama, Japan. He liked studying thought rather than memorizing, especially with interest in physics, biology, world history, Japanese history, and earth science in high school. He studied physics at Saitama University and graduated in 1981. He received his doctorate in 1986 at the University of Tokyo. At the University of Tokyo, he joined Masatoshi Koshiba's research group because neutrinos "seemed like they might be interesting." Career and research. Since 1988, Kajita has been at the Institute for Cosmic Radiation Research, University of Tokyo, where he became  an assistant professor in 1992 and professor in 1999. He became director of the Center for Cosmic Neutrinos at the Institute for Cosmic Ray Research (ICRR) in 1999. , he is a Principal Investigator at the Institute for the Physics and Mathematics of the Universe in Tokyo, and Director of ICRR. In 1998, Kajita's team at the Super-Kamiokande found that when cosmic rays hit the Earth's atmosphere, the resulting neutrinos switched between two flavours before they reached the detector under Mt. Kamioka. This discovery helped prove the existence of neutrino oscillation and that neutrinos have mass. In 2015 , Kajita shared the Nobel Prize in Physics with Canadian physicist Arthur McDonald, whose Sudbury Neutrino Observatory discovered similar results. Kajita's and McDonald's work solved the longstanding Solar neutrino problem, which was a major discrepancy between the predicted and measured Solar neutrino fluxes, and indicated that the Standard Model, which required neutrinos to be massless, had weaknesses. In a news conference at the University of Tokyo, shortly after the Nobel announcement, Kajita said, "I want to thank the neutrinos, of course. And since neutrinos are created by cosmic rays, I want to thank them, too." One of the first  people Kajita called after receiving the Nobel Prize was 2002 Nobel physics laureate Masatoshi Koshiba, his former mentor and a fellow neutrino researcher. Kajita is currently the principal investigator of another ICRR project located at the Kamioka Observatory, the KAGRA gravitational wave detector.