Takaaki Kajita

Takaaki Kajita is a Japanese physicist whose leadership in experiments at Kamiokande and Super-Kamiokande helped establish that neutrinos change flavor, implying they have mass.

Masatoshi Koshiba: Masatoshi Koshiba was a Japanese physicist who led the Kamiokande experiment and shared the 2002 Nobel Prize in Physics. Koshiba led the observatory where Kajita began studying neutrinos.
Neutrino oscillation: Neutrino oscillation is the periodic change of a neutrino from one flavor into another during propagation. This is the phenomenon Kajita’s atmospheric-neutrino measurements established.
Kamiokande: Kamiokande was a Japanese water-Cherenkov detector built to study proton decay and later used to observe neutrinos. Kajita’s early work there identified an atmospheric-neutrino discrepancy.
Standard Model: The Standard Model is the theory describing known elementary particles and three of the four fundamental interactions. Neutrino mass requires physics beyond the Standard Model’s original massless-neutrino formulation.
Neutrino: A neutrino is a neutral, weakly interacting elementary particle that exists in three known flavors. Kajita’s work revealed that these elusive particles have nonzero mass and change flavor.
Yoji Totsuka: Yoji Totsuka was a Japanese physicist who led the Super-Kamiokande collaboration before Kajita. Totsuka guided the experiment through the period when its atmospheric-neutrino anomaly became decisive.
Neutrino mixing: Neutrino mixing is the relationship between neutrino flavor states and neutrino mass states. Mixing lets neutrinos born as muon neutrinos later be detected as other flavors.
Super-Kamiokande: Super-Kamiokande is a large underground water-Cherenkov detector in Japan for neutrino and proton-decay research. Its 1998 atmospheric-neutrino result supplied the decisive evidence associated with Kajita.
Neutrino mass hierarchy: The neutrino mass hierarchy is the ordering of the three neutrino mass states by mass. Oscillation experiments measure mass-squared differences but have not fully settled their ordering.
Particle physics: Particle physics studies the fundamental constituents of matter and their interactions. The discovery forced a revision to a basic assumption within this field.

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Kyoto UniversityRelated: He completed doctoral research at Kyoto University.