Solar Neutrinos. I. Theoretical

The principal energy source for main-sequence stars like the sun is believed to be the fusion, in the deep interior of the star, of four protons to form an alpha particle. The fusion reactions are thought to be initiated by the sequence ^1H(p, e^(+)v)^2H(p,γ)^(3)He and terminated by the following sequences: (i) ^(3)He(^(3)He, 2p)^(4)He; (ii) ^(3)He(α,γ)^(7)Be(e^(-)v)^(7)Li(p,α)^(4)He; and (iii) ^(3)He(α,γ)^(7)Be(p,γ)^(8)B(e^(+)v)^(8)Be*(α)^(4)He. No direct evidence for the existence of nuclear reactions in the interiors of stars has yet been obtained because the mean free path for photons emitted in the center of a star is typically less than 10^(-10) of the radius of the star. Only neutrinos, with their extremely small interaction cross sections, can enable us to see into the interior of a star and thus verify directly the hypothesis of nuclear energy generation in stars.