SNO and the mystery of the missing solar neutrinos

20 June 2001

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Just two years after the physicists working on the Sudbury Neutrino Observatory (SNO) first observed interactions, they have announced results that appear to solve the 30-year old mystery of the "missing solar neutrinos". SNO finds 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.

This week's image shows a probable solar neutrinos detected by SNO, with the detector seen from the side. The white lines indicate the geodesic support structure for the 10,000 photomultiplier tubes (PMTs) that detect light (Cherenkov radiation) emitted by charged particles produced in the interactions of neutrinos in the 1000 tonnes of heavy water within the detector. This light is emitted in a cone around the particle's path, and so forms a circular pattern when it strikes walls of the detector.

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Credit: SNO collaboration
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