Takaaki Kajita

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Takaaki Kajita
Takaaki Kajita 5171-2015.jpg
Takaaki Kajita, Nobel Laureate in physics in Stockholm December 2015
Native name梶田 隆章
Born (1959-03-09) 9 March 1959 (age 59)
Higashimatsuyama, Saitama, Japan
EducationSaitama Prefectural Kawagoe High School
Alma mater Saitama University (B.S.)
University of Tokyo (M.S., Ph.D.)
Awards Asahi Prize (1988)
Bruno Rossi Prize (1989)
Nishina Memorial Prize (1999)
Panofsky Prize (2002)
Japan Academy Prize (2012)
Nobel Prize in Physics (2015)
Fundamental Physics Prize (2016)
Scientific career
Institutions Institute for Cosmic Ray Research, University of Tokyo
Doctoral advisor Masatoshi Koshiba
Other academic advisors Yoji Totsuka

Takaaki Kajita(梶田 隆章,Kajita Takaaki, Japanese pronunciation:  [kadʑita takaːki] , born 9 March 1959) 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.

Physicist scientist who does research in physics

A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate causes of phenomena, and usually frame their understanding in mathematical terms. Physicists work across a wide range of research fields, spanning all length scales: from sub-atomic and particle physics, through biological physics, to cosmological length scales encompassing the universe as a whole. The field generally includes two types of physicists: experimental physicists who specialize in the observation of physical phenomena and the analysis of experiments, and theoretical physicists who specialize in mathematical modeling of physical systems to rationalize, explain and predict natural phenomena. Physicists can apply their knowledge towards solving practical problems or to developing new technologies.

Neutrino Elementary particle with very low mass that interacts only via the weak force and gravity

A neutrino is a fermion that interacts only via the weak subatomic force and gravity. The mass of the neutrino is much smaller than that of the other known elementary particles. Although only differences of squares of the three mass values are known as of 2016, cosmological observations imply that the sum of the three masses must be less than one millionth that of the electron. The neutrino is so named because it is electrically neutral and because its rest mass is so small (-ino) that it was long thought to be zero. The weak force has a very short range, the gravitational interaction is extremely weak, and neutrinos, as leptons, do not participate in the strong interaction. Thus, neutrinos typically pass through normal matter unimpeded and undetected.

Super-Kamiokande architectural structure

Super-Kamiokande is a neutrino observatory located under Mount Ikeno near the city of Hida, Gifu Prefecture, Japan. It is located 1,000 m (3,300 ft) underground in the Mozumi Mine in Hida's Kamioka area. The observatory was designed to detect high-energy neutrinos to search for proton decay, study solar and atmospheric neutrinos, and keep watch for supernovae in the Milky Way Galaxy.


Early life and education

Kajita was born in 1959 in Higashimatsuyama, Saitama, Japan. [1] He liked studying thought rather than memorizing, especially with interest in physics, organism, world history, Japanese history, and earth science in high school. He studied physics at the Saitama University and graduated in 1981. He received his doctorate in 1986 at the University of Tokyo. [2] In UTokyo, he joined Masatoshi Koshiba's laboratory because they were "somehow interested".

Higashimatsuyama, Saitama City in Kantō, Japan

Higashimatsuyama is a city located in Saitama Prefecture, Japan. As of 1 February 2016, the city had an estimated population of 91,520, with a population density of 1,400 persons per km². The total area is 65.33 km2 (25.22 sq mi).

Rote learning A memorization technique based on repetition

Rote learning is a Memorization technique based on repetition. The idea is that one will be able to quickly recall the meaning of the material the more one repeats it. Some of the alternatives to rote learning include meaningful learning, associative learning, and active learning.

Physics study of matter and its motion, along with related concepts such as energy and force

Physics is the natural science that studies matter and its motion and behavior through space and time and that studies the related entities of energy and force. Physics is one of the most fundamental scientific disciplines, and its main goal is to understand how the universe behaves.

Career and research

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. [3]

He became director of the Center for Cosmic Neutrinos at the Institute for Cosmic Ray Research (ICRR) in 1999. As of 2017, he is a Principal Investigator at the Institute for the Physics and Mathematics of the Universe in Tokyo, and Director of ICRR. [4]

The Institute for Cosmic Ray Research (ICRR) of the University of Tokyo was established in 1976 for the study of cosmic rays.

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. [2] [5] 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. [5] Kajita's and McDonald's work solved the longstanding Solar neutrino problem, which was a major discrepancy between the predicted and measured Solar neutrino fluxes, and indicated that the Standard Model, which required neutrinos to be massless, had weaknesses. [5] In a news conference at the University of Tokyo, shortly after the Nobel announcement, Kajita said, "I want to thank the neutrinos, of course. And since neutrinos are created by cosmic rays, I want to thank them, too." [6]

Cosmic ray High-energy particle, mainly originating outside the Solar system

Cosmic rays are high-energy radiation, mainly originating outside the Solar System and even from distant galaxies. Upon impact with the Earth's atmosphere, cosmic rays can produce showers of secondary particles that sometimes reach the surface. Composed primarily of high-energy protons and atomic nuclei, they are originated either from the sun or from outside of our solar system. Data from the Fermi Space Telescope (2013) have been interpreted as evidence that a significant fraction of primary cosmic rays originate from the supernova explosions of stars. Active galactic nuclei also appear to produce cosmic rays, based on observations of neutrinos and gamma rays from blazar TXS 0506+056 in 2018.

Neutrino oscillation phenomenon in which a neutrino changes lepton flavor as it travels

Neutrino oscillation is a quantum mechanical phenomenon whereby a neutrino created with a specific lepton family number can later be measured to have a different lepton family number. The probability of measuring a particular flavor for a neutrino varies between 3 known states, as it propagates through space.

Nobel Prize in Physics One of the five Nobel Prizes established in 1895 by Alfred Nobel

The Nobel Prize in Physics is a yearly award given by the Royal Swedish Academy of Sciences for those who have made the most outstanding contributions for humankind in the field of physics. It is one of the five Nobel Prizes established by the will of Alfred Nobel in 1895 and awarded since 1901; the others being the Nobel Prize in Chemistry, Nobel Prize in Literature, Nobel Peace Prize, and Nobel Prize in Physiology or Medicine.

One of the first people Kajita called after receiving the Nobel Prize was 2002 Nobel physics laureate Masatoshi Koshiba, his former mentor and a fellow neutrino researcher. [2]

Masatoshi Koshiba physicist

Masatoshi Koshiba is a Japanese physicist, known as one of the founders of Neutrino astronomy and jointly won the Nobel Prize in Physics in 2002.

Kajita is currently the principal investigator of another ICRR project located at the Kamioka Observatory, the KAGRA gravitational wave detector. [7]


Takaaki Kajita at a press conference at the Royal Swedish Academy of Sciences Takaaki Kajita 0195.jpg
Takaaki Kajita at a press conference at the Royal Swedish Academy of Sciences



See also

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In particle physics, a massless particle is an elementary particle whose invariant mass is zero. The two known massless particles are both gauge bosons: the photon and the gluon. However, gluons are never observed as free particles, since they are confined within hadrons. Neutrinos were originally thought to be massless. However, because neutrinos change flavor as they travel, at least two of the types of neutrinos must have mass. The discovery of this phenomenon, known as neutrino oscillation, led to Canadian scientist Arthur B. McDonald and Japanese scientist Takaaki Kajita sharing the 2015 Nobel prize in physics.

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  1. "Takaaki Kajita - Facts". Nobel Foundation. 6 October 2015. Retrieved 6 October 2015.
  2. 1 2 3 "Japan's Takaaki Kajita shares Nobel in physics". Japan Times. 6 October 2015. Retrieved 7 October 2015.
  3. "2015 Nobel Prize in Physics: Canadian Arthur B. McDonald shares win with Japan's Takaaki Kajita". CBC News. 6 October 2015. Retrieved 6 October 2015.
  4. "About ICRR". Institute for Cosmic Ray Research, University of Tokyo.
  5. 1 2 3 Randerson, James and Ian Sample (6 October 2015). "Kajita and McDonald win Nobel physics prize for work on neutrinos". The Guardian . Retrieved 6 October 2015.
  6. Overbye, Dennis (6 October 2015). "Takaaki Kajita and Arthur McDonald Share Nobel in Physics for Work on Neutrinos". New York Times . Retrieved 6 October 2015.
  7. "Professor Kajita won the novel prize in physics !!" (Press release). KAGRA collaboration. 7 October 2015. Professor Kajita, who is the PI of KAGRA, won the Nobel prize in physics !!
  8. "Recipients of the Asahi Prize". Asahi Shimbun . Retrieved 12 August 2016.
  9. "HEAD AAS Rossi Prize Winners". Home High Energy Astrophysics Division . Retrieved 12 August 2016.
  10. "Recipients of the Asahi Prize". Asahi Shimbun . Retrieved 12 August 2016.
  11. "Recipients of Nishina Memorial Prizes". Nishina Memorial Foundation . Retrieved 12 August 2016.
  12. "2002 W.K.H. Panofsky Prize in Experimental Particle Physics Recipient". American Physical Society . Retrieved 12 August 2016.
  13. "第1回「戸塚洋二賞」選考結果". Heisei Foundation for Basic Science. 24 February 2012. Archived from the original on 6 March 2016. Retrieved 17 November 2015.(in Japanese)
  14. "The Imperial Prize, Japan Academy Prize, Duke of Edinburgh Prize Recipients". Japan Academy. 4 June 2012. Retrieved 12 August 2016.
  15. "Japan Academy Prize to – Takaaki Kajita" (PDF). Japan Academy. 4 June 2012. Retrieved 12 August 2016.
  16. "Julius Wess Award to Takaaki Kajita". Kavli Institute for the Physics and Mathematics of the Universe. 27 November 2013. Retrieved 17 November 2015.
  17. "The Nobel Prize in Physics 2015".. Nobelprize.org. Nobel Media AB 2014. Web. 6 October 2015.
  18. "Breakthrough Prize Awarded $22 Million In Science Prizes" (Press release). San Francisco: Fundamental Physics Prize. November 8, 2015.
  19. Azeem, Ahmad. "Nobel Laureate Takaaki Kajita conferred DSc at AMU's 64th convocation". India Today. Retrieved November 1, 2016.
  20. http://www.paginasiete.bo/sociedad/2016/5/3/kajita-emociones-ciencia-esperan-jovenes-bolivianos-95234.html
  21. http://www.ilmattino.it/napoli/cultura/federico_ii_laurea_honors_causa_al_premio_nobel_takaaki_kajita-2227113.html
  22. http://www.unibe.ch/university/university_for_everyone/dies_academicus/dies_academicus_2017/honors/index_eng.html