Ghostly particle mystery 'solved'
Posted: Monday, June 18, 2001
(BBC) An international team of physicists claims to have solved a 30-year-old mystery: the puzzle of the missing solar neutrinos.
In the past scientists detected only about a third of the expected quantity of these tiny particles coming from the powerhouse at the Sun's core. It was a major flaw in our understanding of matter and energy.
New observations made by a giant underground neutrino detector in Canada show that the solution lies not with the Sun, but with the neutrinos, which change as they travel from the core of the Sun to the Earth.
The finding raises new questions about the so-called Standard Model of Particle Physics, which seeks to explain the basic building blocks of matter.
The research was carried out at the Sudbury Neutrino Observatory (SNO), Ontario, in collaboration with Oxford University, UK.
"We now have high confidence that the discrepancy is not caused by problems with the models of the Sun but by changes in the neutrinos themselves as they travel from the core of the Sun to the Earth," says Dr Art McDonald, SNO project director and professor of physics at Queen's University in Kingston, Ontario, Canada.
"It's taken longer than we thought, but it's all been well worthwhile," says Dr Steve Biller, of Oxford University. "We've pushed the limits of engineering, chemistry... and patience, in order to push the limits of physics."
Neutrinos are fundamental particles of matter. They are often called 'ghostly' because they interact so weakly with other forms of matter.
They come in three types: the electron-neutrino, the muon-neutrino and the tau-neutrino. Electron-neutrinos are emitted in vast numbers by the nuclear reactions that power the Sun. More
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