Nobel Prize in Physics goes to discoverers of ‘identity switching’ neutrinos

This year’s Nobel Prize in Physics goes to Japan’s Takaaki Kajita and Canadian Arthur B. McDonald for demonstrating the ‘identity change’ of neutrinos, also known as ‘ghost particles’. The interchange shows that neutrinos also have mass.

The award was announced on Tuesday, but the scientists discovered the neutrino oscillation or neutrino oscillation as early as the year 2000. Kajita then showed that neutrinos from the atmosphere switch between two ‘identities’. The discovery was made using the Super-Kamiokande detector in Japan. At about the same time, a research group in Canada led by McDonald found that neutrinos from the sun did not disappear on their way to Earth, but that they arrived on Earth and could be observed with a different “identity” at the Sudbuy Neutrino Observatory.

Both observations confirmed long-held suspicions, which in turn led to the conclusion that neutrinos do have mass. This is in contrast to theories that were common until then, in which neutrinos have no mass. The latter led to headaches within the standard model.

Neutrinos are formed by reactions between the cosmic rays and the Earth’s atmosphere. Other neutrinos are created by nuclear reactions in the sun. Every second, trillions of neutrinos pass through a person at once. Because virtually nothing can stop them, they are difficult to observe and examine. To detect them, various institutes around the world built detectors in underground mines. Both the Japanese and Canadian detectors consist of a water-filled chamber deep below in old mines. The Japanese look at neutrinos entering the atmosphere on their opposite side of the Earth, while the Canadians look at neutrinos directly from the atmosphere from the sun. For example, a neutrino from the sun appears to change from an electron neutrino to a muon or tau neutrino.

Sudbuy Neutrino Observatory – Super Kamiokande Detector