Systematics of beta decay

The Feynman diagram for the beta decay of a neutron into a proton, electron, and electron antineutrino via an intermediate heavy W- boson

Beta decay is quite a bit more subtle and complex than the other two common forms of radioactivity—alpha decay and gamma decay. In alpha decay, nucleons fall out of a nucleus because they are electrically repelled by the other protons and can go into a lower energy state by leaving, while in gamma decay nucleons fall down into a lower energy state (under the rules of quantum mechanics) in a similar manner to the drop in electron energy levels in an atom, albeit at a much more energetic level.

Beta decay, unlike the other two, involves actual transmutation of nucleons, typically among protons, neutrons, and electrons/positrons. This has far-reaching consequences involving electric charge and various conservation laws. This article will attempt to peel back the layers of complexity one at a time.

Beta decay involves the "weak force", unlike alpha decay, which involves the "strong force". Nevertheless, beta decay has some extremely far-reaching consequences for radioactivity, nucleosynthesis, and supernovas.