The Neutrino problem


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Neutrino Problem

Question: Where do you build a telescope to see inside the sun?

Answer: Two miles down a disused goldmine!

One of the by-products of a nuclear reaction is the neutrino, a particle which may be massless like the photon but which interacts with matter very rarely. In any second there will be billions of neutrinos passing through the Earth leaving no trace of their presence. Within this vast number, however, there are some which do interact with matter resulting in nuclear transmutation.

The Sun may be regarded as a huge nuclear fusion reactor and hence a source of neutrinos. In order to detect these a detector has been built at the bottom of the Homestake mine in South Dakota. The reason for burying the detector so deep is that nuclear transmutation can also occur when cosmic rays interact with matter, but these are absorbed by the intervening rock leaving neutrinos as the only candidate for the transmutation. The detector is full of industrial cleaning fluid since Chlorine 37 is converted to Argon by the occasional neutrino; measuring the Argon content gives a measure of the neutrino flux through the detector.

Unfortunately the measured neutrino flux is only a third of that predicted by nuclear physics. Possible causes of this conflict are that models of the solar interior (see Temperature Structure) are in error, or the fact that the neutrinos detected are of low energy and not from the main proton-proton fusion reactions. A further suggestion is that if neutrinos possess mass they may alternate between their three types (electron, tauon and muon neutrinos) with only one form being detected.


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AWH/JOC Sep 95