AsianScientist (Oct. 7, 2015) – Japan took the scientific community by storm this week with two of its fraternity winning Nobel Prizes back to back. Part of the 2015 Nobel Prize in Physiology or Medicine went to Satoshi Omura earlier this week while half of the 2015 Nobel Prize in Physics was awarded to Takaaki Kajita yesterday.
Kajita, born 1959 in Japan, received his PhD in 1986 from the University of Tokyo. He is the director of the Institute for Cosmic Ray Research and professor at the University of Tokyo, Kashiwa, Japan. Together with Professor Arthur B. McDonald, the duo received the Nobel honor for their “discovery of neutrino oscillations, which shows that neutrinos have mass.”
After photons, which are particles of light, neutrinos are the most numerous in the entire cosmos. Neutrinos are created in reactions between cosmic radiation and the Earth’s atmosphere, as well as in nuclear reactions inside the stars. The Earth is constantly bombarded by them.
Around the turn of the millennium, Kajita, working at the Super-Kamiokande detector in Japan, discovered that neutrinos from the atmosphere switch between two identities as they make their way to Earth. Meanwhile, McDonald’s research group at the Sudbury Neutrino Observatory in Canada demonstrated that the neutrinos from the Sun do not disappear on their way to Earth. Instead, they are captured with a different identity upon arrival on Earth.
With the knowledge that neutrinos change their identities as they reach the Earth, physicists could now resolve a decades-long puzzle: they could explain why two-thirds of neutrinos go missing during experimental calculations. It also led to the far-reaching conclusion that neutrinos, which for a long time were considered massless, must have some mass, however small.
For particle physics this was a historic discovery. The Standard Model of the innermost workings of matter had been incredibly successful, having resisted all experimental challenges for more than twenty years. However, as it requires neutrinos to be massless, the new observations had clearly showed that the Standard Model cannot be the complete theory of the fundamental constituents of the universe.
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Source: Nobel Foundation.
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