ABSTRACT

In a nuclear beta decay, a neutron decays into a proton, an electron and a neutrino. In the beginning neutrinos were not observed in the beta decay; they were postulated to satisfy conservation laws. Since the electrons emitted in a beta decay are not monoenergetic, energy and momentum conservation ruled out the possibility of a twobody decay of neutrons into a proton and an electron. Pauli postulated [48] the new particle, the neutrino, to explain the energy distribution of electrons. Conservation of angular momentum implied that the neutrinos are spin-1/2 fermions.