(c) University of Tokyo
I’d like to offer my most heartfelt congratulations to Professor Takaaki Kajita for winning the Nobel Prize in physics for“the discovery of neutrino oscillations, which indicates the existence of the neutrino’s mass.”
There are three types of neutrinos (also known as interaction eigenstates), the electron neutrino, the muon neutrino, and the tau neutrino. The phenomenon in which these neutrinos change type midflight is called “neutrino oscillations.” However, in order for these oscillations to occur neutrinos must be massive and additionally their interaction eigenstates must be a mixture of states whose individual masses differ.
Professor Kajita raised the issue of the“atmospheric neutrino anomaly” based on the observation that the ratio of the electron neutrino and muon neutrino components of the Kamiokande experiment’s atmospheric neutrino data did not agree with expectations.
Using the Super-Kamiokande detector, which is 20 times larger, he showed in 1998 that the cause of the anomaly is neutrino oscillations. Though the neutrino is massless in the standard model of elementary particles, Professor Kajita’s discovery indicates that there are deficiencies in this theory. Through further neutrino research I hope that we can reveal what theory lies beyond the standard model and unravel the mystery of matter’s preponderance in today’s universe.
Director Kamioka Observatory
The University of Tokyo Institute for Cosmic Ray Research