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Solar neutrino
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Electron neutrinos are produced in the Sun as a product of nuclear fusion.
The main contribution comes from the so-called proton-proton chain reaction. The net reaction is:
- ,
or in words:
- 4 protons + 2 electrons = Helium + 2 electron neutrinos.
Neutrinos from the proton-proton process have energy up to 400 keV. There are also several other significant production mechanisms, with energies up to 10 MeV.
The number of neutrinos can be predicted by the Standard Solar Model. The detected number of electron neutrinos was only 1/3 of the predicted number, and this was known as the solar neutrino problem. It led to the idea of neutrino oscillations and the fact that neutrinos can change flavour. This was confirmed when the total flux of solar neutrinos of all types was measured and it agreed with the earlier predictions of expected electron neutrino flux, as seen by Sudbury Neutrino Observatory, and thus confirmed that neutrinos have mass.
See also
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