Masatoshi Koshiba

Masatoshi Koshiba
Koizumi Cabinet E-mail Magazine, No.74, December 12, 2002
Born	(1926-09-19)September 19, 1926 Toyohashi, Aichi, Japan
Died	November 12, 2020(2020-11-12) (aged 94) Tokyo, Japan
Nationality	Japan
Alma mater	University of Tokyo University of Rochester
Known for	Astrophysics, neutrinos
Awards	Humboldt Prize (1997) Wolf Prize in Physics (2000) Nobel Prize in Physics (2002)
Scientific career
Fields	Physics
Institutions	University of Chicago University of Tokyo Tokai University
Thesis	High energy electron-proton cascade in cosmic radiation  (1955)
Doctoral advisor	Morton F. Kaplon
Other academic advisors	Shin'ichirō Tomonaga Takahiko Yamanouchi
Doctoral students	Yoji Totsuka Atsuto Suzuki
Other notable students	Takaaki Kajita

Masatoshi Koshiba (小柴 昌俊, Koshiba Masatoshi, September 19, 1926 – November 12, 2020) was a Japanese physicist, known as one of the founders of Neutrino astronomy and jointly won the Nobel Prize in Physics in 2002.

He was Senior Counselor of International Center for Elementary Particle Physics (ICEPP) and Emeritus Professor of University of Tokyo. He was also the chief patron of the Edogawa NICHE Prize Steering Committee

Life

with Jun'ichirō Koizumi and Kōichi Tanaka (at the Prime Minister's Official Residence on October 11, 2002)

with Jun'ichirō Koizumi (at Kamioka Observatory, Institute for Cosmic Ray Research, University of Tokyo on August 27, 2003)

He graduated from the University of Tokyo in 1951 and received a Ph.D. in physics at the University of Rochester, New York, in 1955. From July 1955 to February 1958 he was Research Associate, Department of Physics, University of Chicago; from March 1958 to October 1963, he was Associate Professor, Institute of Nuclear Study, University of Tokyo, although from November 1959 to August 1962 he was on leave from the above as Senior Research Associate with the honorary rank of Associate Professor and as the Acting Director, Laboratory of High Energy Physics and Cosmic Radiation, Department of Physics, University of Chicago. 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. In 2002, he jointly won the Nobel Prize in Physics "for pioneering contributions to astrophysics, in particular for the detection of cosmic neutrinos". (The other shares of that year's Prize were awarded to Raymond Davis Jr. and Riccardo Giacconi of the U.S.A.)

Koshiba's award-winning work centred on neutrinos, subatomic particles that had long perplexed scientists. Since the 1920s it had been suspected that the Sun shines because of nuclear fusion reactions that transform hydrogen into helium and release energy. Later, theoretical calculations indicated that countless neutrinos must be released in these reactions and, consequently, that Earth must be exposed to a constant flood of solar neutrinos. Because neutrinos interact weakly with matter, however, only one in a trillion is stopped on its way to Earth. Neutrinos thus developed a reputation as being undetectable.

In the 1980s, Koshiba, drawing on the work done by Raymond Davis Jr, constructed an underground neutrino detector in a zinc mine in Japan. Called Kamiokande II, it was an enormous water tank surrounded by electronic detectors to sense flashes of light produced when neutrinos interacted with atomic nuclei in water molecules. Koshiba was able to confirm Davis's results—that the Sun produces neutrinos and that fewer neutrinos were found than had been expected (a deficit that became known as the solar neutrino problem). In 1987 Kamiokande also detected neutrinos from a supernova explosion outside the Milky Way. After building a larger, more sensitive detector named Super-Kamiokande, which became operational in 1996, Koshiba found strong evidence for what scientists had already suspected—that neutrinos, of which three types are known, change from one type into another in flight; this resolves the solar neutrino problem, since early experiments could only detect one type, not all three.

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 and also a founding patron of Edogawa NICHE Prize Steering committee . He died on November 12, 2020 in Tokyo at the age of 94.

Awards

• 1987 – Asahi Prize
• 1987 – Nishina Memorial Prize
• 1997 – Humboldt Prize
• 2000 – Wolf Prize in Physics
• 2002 – Nobel Prize in Physics
• 2002 – Panofsky Prize
• 2003 – Benjamin Franklin Medal in Physics

Honors

• 1985 – Order of Merit of the Federal Republic of Germany
• 1997 – Order of Culture
• 2002 – Honorary citizenship of Suginami
• 2002 – Honorary doctor of Meiji University
• 2002 - Elected Fellow of the American Physical Society.
• 2003 – Grand Cordon of the Order of the Rising Sun
• 2003 – In commemoration of the Nobel Prize-winning by Masatoshi Koshiba, Koshiba hall was established at the University of Tokyo's School of science.
• 2003 – Honorary citizenship of Tokyo
• 2003 – Emeritus Professor of the University of Tokyo

Publications

• Koshiba, M.; Fukuda, Y; et al. (1998). "Evidence for Oscillation of Atmospheric Neutrinos". Physical Review Letters. 81 (8): 1562–1567. arXiv:hep-ex/9807003. Bibcode:1998PhRvL..81.1562F. doi:10.1103/PhysRevLett.81.1562.
• Koshiba, M.; Fukuda, Y; et al. (1999). "Constraints on Neutrino Oscillation Parameters from the Measurement of Day-Night Solar Neutrino Fluxes at Super-Kamiokande". Physical Review Letters. 82 (9): 1810–1814. arXiv:hep-ex/9812009. Bibcode:1999PhRvL..82.1810F. doi:10.1103/PhysRevLett.82.1810.

See also

• Kamioka Observatory
• Institute for Cosmic Ray Research
• List of Japanese Nobel laureates
• List of Nobel laureates affiliated with the University of Tokyo
• List of Nobel Laureates affiliated with the University of Rochester
• University of Rochester

External links

• Prof. Koshiba has won the Nobel prize.
• Masatoshi Koshiba on Nobelprize.org including the Nobel Lecture December 8, 2002 Birth of Neutrino Astrophysics
• Freeview video 'An Interview with Masatoshi Koshiba' by the Vega Science Trust