2015
Neutrino Oscillations
Takaaki Kajita & Arthur B. McDonald
About This Prize
The 2015 Nobel Prize in Physics was awarded to Takaaki Kajita and Arthur B. McDonald “for the discovery of neutrino oscillations, which shows that neutrinos have mass.” The Standard Model originally assumed neutrinos were massless, but experiments at Super-Kamiokande in Japan and the Sudbury Neutrino Observatory (SNO) in Canada demonstrated that neutrinos change flavor as they travel, a phenomenon only possible if they possess non-zero mass. This discovery resolved the long-standing solar neutrino problem and opened a window into physics beyond the Standard Model.
Takaaki Kajita
“Discovery of Atmospheric Neutrino Oscillations”
Arthur B. McDonald
“The Sudbury Neutrino Observatory: Observation of Flavor Change for Solar Neutrinos”
Key Concepts
- • Neutrino Flavor Oscillations: Neutrinos transition between electron (νe), muon (νμ), and tau (ντ) flavors as they propagate through space
- • Super-Kamiokande Atmospheric Neutrino Anomaly: A deficit of upward-going muon neutrinos revealed that atmospheric neutrinos oscillate during their journey through the Earth
- • SNO Measurement of Total Solar Neutrino Flux: Using heavy water (D2O), SNO detected all three neutrino flavors, confirming solar neutrino flavor conversion
- • Neutrino Mass — Beyond the Standard Model: Oscillations require non-degenerate masses, proving neutrinos are massive and extending the Standard Model