The oscillating neutrinos

We know that ordinary matter consists of electrons, protons and neutrons. The protons and the neutrons constitute the atomic nucleus. However not all atomic nuclei are stable and undergo radioactive decays. If the neutron to proton ratio is higher than that required for stability, a nucleus can undergo beta decay in which a neutron in a nucleus was initially thought to be getting converted to a proton and an electron: p →+e^-. This being a two body process, the electron was expected to be emitted with a fixed energy given by the difference between the neutron and the proton energy. But in practice electrons of all possible energies were observed