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Solar neutrino

How did they solve the solar neutrino problem?

To answer this, first we have to review what exactly was the solar neutrino problem. The story begins somewhere in the past as early as 1920 when Sir Arthur Eddington proposed that the stars were powered by nuclear fusion, a process in which four hydrogen atoms fuse together to form a helium atom. In this process 2 netrinos of the electron type are emitted with about 26 MeV of energy. The neutrinos produced in the core of Sun escapes and reaches Earth. Neutrinos are weakly interacting particles and are very hard to detect. In order to test the nuclear fusion inside the Sun, experiments were conducted to detect the neutrinos reaching the Earth. Various techniques were utilised but only a third of the trotal neutrinos emitted from the Sun were detected. These missing neutrinos is the solar neutrino problem. These experiments are capable of detecting only the electron neutrinos.

Sudbury Neutrino Observatory (SNO) in Ontario, Canada, makes use of heavy water (D2O, deuterium instead of hydrogen) to detect neutrinos. The advantage of this facility is that it is capable of detecting all three flavors of neutrinos, the electron, the muon and the tau neutrinos, associated with the respective leptons, electrons, muons and tau leptons. The experiments conducted in 2001 detected all the solar neutrinos suggesting that on their way from Sun to Earth neutrinos change their flavor, a phenomenon known as neutrino oscillation.