Takaaki Kajita is a Japanese physicist, known for neutrino experiments at the Kamiokande and its successor, Super-Kamiokande. In 2015, he was awarded the Nobel Prize in Physics jointly with Canadian physicist Arthur B. McDonald.

Kajita was born in 1959 in Higashimatsuyama, Saitama, Japan. He studied physics at the Saitama University and graduated in 1981. He received his doctorate in 1986 at the University of Tokyo.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.

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.

Takaaki Kajita received the G.P. Birla Award for Life Time Achievement in Science and delivered the G.P. Birla Distinguished Lecture “Atmospheric Neutrinos and Neutrino Oscillations” on December 26, 2017.