Takaaki Kajita

Biosketch

Takaaki Kajita is a physicist recognized for his work on neutrinos, small subatomic particles. He is known particularly for his studies on neutrinos that are produced by cosmic ray interactions in the atmosphere, and neutrino oscillations. He is currently studying gravitational waves.
Kajita was born in Higashimatsuyama City, Japan and grew up there. He received PhD in physics at the University of Tokyo in 1986. He was a research associate at the International Center for Elementary Particle Physics of the University of Tokyo. In 1988, he moved to the Institute for Cosmic Ray Research (ICRR) of the University of Tokyo. He was the director of ICRR between 2008 and 2022. He is a Council Member of the Science Council of Japan since 2017 and the President since 2020, both until 2023. He is a member of the Japan Academy since 2019. In May 2022, Kajita was elected as an International Member of the U.S. National Academy of Sciences.

Research Interests

Takaaki Kajita has been researching at Kamiokande and Super-Kamiokande neutrino detectors at Kamioka in central Japan. In particular, he has been studying neutrinos that are produced by cosmic ray interactions in the atmosphere (atmospheric neutrinos). The detailed studies of atmospheric neutrinos led to the discovery of neutrino oscillations in 1998.
Around 2008, Kajita changed his research to gravitational waves. He and his team constructed the KAGRA gravitational wave detector in Kamioka. KAGRA is a large laser interferometer with the arm lengths of 3km. The key features of KAGRA are the deep underground location to minimize the seismic noises and the cryogenic mirrors to minimize the thermal noises. KAGRA had a short, initial observation in the spring of 2020 and is expected to carry out the second observation in 2023 and 2024. Kajita and his team would like to study gravitational waves produced by mergers of heavy compact stars in collaboration with LIGO in USA and Virgo in Europe.