= Kajita-McDonald neutrino flavor-conversion experiments
{c}
{title2=1998, 2001–2002}
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>.<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]{ref}
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.
\Image[/water-cherenkov-neutrino-readout-comparison.png]
{title=Two functional routes from a <neutrino> interaction to a recorded light pattern}
{description=Original schematics, not scale drawings or event photographs. Left: directional ring classification in <Super-Kamiokande>. Right: the pure-<heavy water> phase of the <Sudbury Neutrino Observatory>, including the indirect <neutron> channel. Sparse dots stand for <photomultipliers>.}
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