How can a detector establish that an unseen particle changes identity? The Super-Kamiokande atmospheric-neutrino experiment compares different travel paths; the Sudbury Neutrino Observatory compares different interaction channels. Both infer neutrino flavor from reaction products and calibrated responses. Their complementarity connects particle detection to neutrino oscillation, neutrino mass and neutrino astronomy.
Takaaki Kajita and Arthur B. McDonald shared the 2015 physics Nobel Prize. These were collaboration achievements: Yoichiro Suzuki's Super-Kamiokande work included the solar neutrino analysis, and George Ewan helped establish and lead the Sudbury Neutrino Observatory.[ref]
ICRR’s Takaaki Kajita to share Breakthrough Prize in Fundamental Physics by Institute for Cosmic Ray Research, University of Tokyo. Research contributions of Kajita and Suzuki; shared 2015 prize
[ref]https://www.queensu.ca/gazette/stories/queen-s-remembers-professor-emeritus-george-ewan/. 17 December 2020: founding and joint leadership of SNO
The older Kamiokande account explains water Cherenkov neutrino reconstruction; Raymond Davis Jr.'s Homestake experiment explains why a deficit in an electron neutrino channel alone leaves a source-versus-propagation ambiguity. Complementary channels can break that ambiguity.
Takaaki Kajita Created 2026-10-18 Updated 2026-11-05
Takaaki Kajita contributed to the Super-Kamiokande observation of atmospheric neutrino oscillations. Muon neutrinos arriving from below had crossed a much longer path through the Earth than those produced overhead. The direction-dependent deficit therefore tested propagation, while comparisons with electron-like events helped constrain possible production or detector explanations. The 1998 report found the pattern consistent with conversion between muon neutrinos and tau neutrinos.[ref]
Evidence for oscillation of atmospheric neutrinos by Y. Fukuda and others. 1998 abstract and zenith-angle analysis; oscillation interpretation and checks on flux/detector uncertainties
A physicist researching atmospheric neutrinos and neutrino oscillations.[ref]
ICRR’s Takaaki Kajita to share Breakthrough Prize in Fundamental Physics by Institute for Cosmic Ray Research, University of Tokyo. Independent professional identity
Portrait of Takaaki Kajita
. Holger Motzkau. CC BY-SA 3.0, via Wikimedia Commons. Source.
Yoichiro Suzuki Created 2026-10-18 Updated 2026-11-05
Yoichiro Suzuki worked on water-based Cherenkov radiation detection of neutrinos, including solar and atmospheric measurements. The Super-Kamiokande method classifies the visible rings made by secondary electrons and muons and compares their rates with the direction through the Earth. A directional deficit carries information about propagation distance as well as production. This makes the apparatus a test of neutrino oscillations, rather than simply a counter of weakly interacting particles.[ref]
Evidence for oscillation of atmospheric neutrinos by Y. Fukuda and others. 1998, event classification and zenith-angle-dependent muon-neutrino deficit
A physicist researching solar neutrinos and neutrino detection.[ref]
ICRR’s Takaaki Kajita to share Breakthrough Prize in Fundamental Physics by Institute for Cosmic Ray Research, University of Tokyo. Independent professional identity