Масатоси Кошиба: пионер нейтринной астрономии и лауреат Нобелевской премии

Japanese physicist (1926–2020)

was a Japanese physicist and one of the founders of neutrino astronomy. His work with the neutrino detectors Kamiokande and Super Kamiokande was instrumental in detecting solar neutrinos, providing experimental evidence for the solar neutrino problem. Koshiba won the Nobel Prize in Physics in 2002 (jointly with Raymond Davis Jr.) "for pioneering contributions to astrophysics, in particular for the detection of cosmic neutrinos". He was a senior counselor at the International Center for Elementary Particle Physics (ICEPP) and professor at the University of Tokyo.

Koshiba was born in Toyohashi in central Japan on September 19, 1926, to Toshio and Hayako Koshiba. His father was a military officer. His mother died when he was three, leading to his father marrying his wife's elder sister. He grew up in Yokosuka, and completed his high school in Tokyo. It is mentioned that his initial interest was in studying German literature, but, ended up studying physics, spurred by a teacher's denigrating comments. At the University of Tokyo he became associate professor in March 1963 and then professor in March 1970 in the Department of Physics, Faculty of Science, and emeritus professor there in 1987. From 1987 to 1997, Koshiba taught at Tokai University. Koshiba's initial research was in cosmic rays. In 1969, he shifted into electron positron collider physics, and was involved with the JADE detector in Germany, which helped confirm the Standard Model. Along with Masayuki Nakahata and Atsuto Suzuki, Koshiba designed the Kamiokande experiment to detect proton decay, a prediction of grand unified theories. No proton decay was detected, but Koshiba realized the detector could be made to detect neutrinos, and adapted the project accordingly, following the pioneering U. S. work of Davis. In the early 1970s, Koshiba collaborated with Gersh Budker (1918 1977), the particle accelerator electron cooling pioneer in the Soviet Union. This collaboration was cut short for unknown reasons but Budker died of heart attack a few years later. Through this experiment, he (and Davis in the U. S.) were able to confirm the prediction that neutrinos are generated during the nuclear fusion reaction in the sun. However, these experiments detected fewer neutrinos than had been expected. This deficit was called the solar neutrino problem. Koshiba was a member of the Board of Sponsors of the Bulletin of the Atomic Scientists, and also a foreign fellow of Bangladesh Academy of Sciences. He was a founding member of the Edogawa NICHE Prize Steering committee.

Koshiba married Kyoto Kato, an art museum curator, when he returned to Japan in the late 1950s. The couple had a son and a daughter.