Solar neutrino problem

The solar neutrino problem was a major discrepancy between measurements of the neutrinos flowing through the Earth and theoretical models of the solar interior, lasting from the mid-1960s to about 2002. The discrepancy has since been resolved by new understanding of neutrino physics, requiring a modification of the Standard Model of particle physics. Essentially, if neutrinos do have mass, then they can change from the type that had been expected to be produced in the sun's interior into a type that would not be caught by the detectors in use at the time.

Experimental evidence for neutrino mass

The supernova 1987a produced an indication that neutrinos might have mass, because of the difference in time of arrival of the neutrinos detected at Kamiokande, and the small number detected versus the convective overturn model of supernovae. However, the data was insufficient to draw any conclusions with certainty.

Related Topics:
Supernova - Convective overturn

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The first strong evidence for neutrino oscillation came in 1998 from the Super-Kamiokande collaboration in Japan. It produced observations consistent with muon-neutrinos (produced in the upper atmosphere by cosmic rays) changing into tau-neutrinos. Actually all that was proved was that less neutrinos were detected coming through the Earth than could be detected coming directly above the detector. Not only that, their observations only concerned muon neutrinos coming from the interaction of cosmic rays with the Earth's atmosphere. NO tau neutrinos were observed at Super-Kamiokande. More direct evidence came in 2002 from the Sudbury Neutrino Observatory (SNO) in Canada. It detected all types of neutrinos coming from the sun, and was able to distinguish between electron-neutrinos and the other two flavors. After extensive statistical analysis, it was found that about 35% of the arriving solar neutrinos are electron-neutrinos, with the others being muon- or tau-neutrinos. The total number of detected neutrinos agrees quite well with the earlier predictions from nuclear physics based on the fusion reactions inside the sun.

Related Topics:
Neutrino oscillation - 1998 - Super-Kamiokande - 2002 - Sudbury Neutrino Observatory - Canada

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In 2002 Raymond Davis Jr. and Masatoshi Koshiba won part of the Nobel Prize in Physics for experimental work that found the number of solar neutrinos was around a third of the number predicted by the Standard Model.

Related Topics:
2002 - Raymond Davis Jr. - Masatoshi Koshiba - Nobel Prize in Physics - Standard Model

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