"Beta decay was…like a dear old friend. There would always be a special place in my heart reserved especially for it."
In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which an atomic nucleus emits a beta particle, transforming into an isobar of that nuclide. For example, beta decay of a neutron transforms it into a proton by the emission of an electron accompanied by an antineutrino; or, conversely a proton is converted into a neutron by the emission of a positron with a neutrino in what
"In beta decay experiments it is generally some properties of the emitted , the electron and neutrino, that are measured, such as their energy, polarization or angular distribution. ...In beta decay, angular momentum is conserved but it is now known that parity is not conserved. The leptons are emitted in states of indefinite parity."
Beta decay