Kajita, Takaaki 1959–, Japanese physicist, Ph.D. Univ. of Tokyo, 1986. In 1988 he joined the faculty at the Univ. of Tokyo, where he is now professor and director of the Institute for Cosmic Ray Research. Kajita shared the 2015 Nobel Prize in Physics with Arthur McDonald for the discovery of neutrino flavor oscillation, which showed that neutrinos have mass. In the late 1990s, working with Super-Kamiokande detector, an underground research facility that can detect subtle changes in neutrinos, Kajita and his team found evidence that the neutrino oscillated among three different types, or flavors. This finding also indicated that, contrary to the Standard Model of particle physics, neutrinos must have mass. The discovery that neutrinos have mass provided the foundation for a better understanding of the evolution of the universe, the workings of the sun, and the mechanism of supernova explosions.
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