Beta decay

In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which a proton is transformed into a neutron, or vice versa, inside an atomic nucleus. This process allows the atom to move closer to the optimal (more stable) ratio of protons and neutrons. As a result of this transformation, the nucleus emits a detectable beta particle, which is an electron or positron.

Quotes

• In beta decay experiments it is generally some properties of the emitted leptons, 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.
  • Harry J. Lipkin, Beta Decay for Pedestrians (2012) pp. 3-4

• Beta decay was…like a dear old friend. There would always be a special place in my heart reserved especially for it.
  • Chien-Shiung Wu, In H. B. Newman and T. Ypsilantis (eds.) History of Original Ideas and Basic Discoveries in Particle Physics (1996)