Neutrino Masses and Oscillations
The Old Enigma.
The most enigmatic of elementary particles, neutrinos were postulated in 1930, but were not observed until a quarter of a century later. It took another forty years to determine that they are not massless.
Neutrinos are a ubiquitous if imperceptible part of our environment. Neutrinos created in the Big Bang together with the cosmic background radiation pervade the entire Universe. The Sun is a poweful source of MeV neutrinos. Neutrinos in the GeV range are created when cosmic rays strike the atmosphere, 15 kilometers or so above the Earth’s surface. Every nuclear reactor emits antineutrinos copiously. High-energy neutrinos are regularly produced at accelerators through particle decay and carefully ...