Wiktionary
n. (context physics English) A nuclear reaction in which a beta particle (electron or positron) is emitted
WordNet
n. radioactive decay of an atomic nucleus that is accompanied by the emission of a beta particle
Wikipedia
In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which a beta ray (an energetic electron or positron) and an associated antineutrino or neutrino are emitted from an atomic nucleus. By beta decay, a proton within the nucleus is transformed into a neutron, or vice versa, changing the nuclide type. The beta particle and its associated neutrino do not exist within the nucleus prior to beta decay, but are created. By the process of beta decay an unstable atom obtains a more stable ratio of protons and neutrons. The stability of this ratio forms the nuclear valley of stability.
Beta decay is a consequence of the weak force, which is characterized by relatively lengthy decay times. Nucleons are composed of up or down quarks, and the weak force allows a quark to change type by the exchange of a W boson and the creation of an electron/antineutrino or positron/neutrino pair. A neutron composed of two down quarks and an up quark, decays to a proton composed of a down quark and two up quarks, for example. Decay times for many nuclides that are subject to beta decay can be thousands of years.
Usage examples of "beta decay".
Which causes a small proportion of the long neutrons here to undergo beta decay, even if they're in supposedly stable nuclei.
Jayme thought it was fascinating the way the medics traced the exact amplitude of the beta decay, comparing the magnetic polarization of the nucleus against the spin vector of the electrons.
But un-neutrinos exhibit antidecay and assemble themselves into elementary particles, in the reverse of beta decay.
Among them one can distinguish particles generated in stars (therefore in the sun as well) through natural processes such as beta decay and other nuclear reactions, and particles produced from collisions between neutrinos and the nuclei of atoms in Earth's atmosphere or in the crust of the globe.
There are four known forces in modern physics: two sub-nuclear forces responsible respectively for alpha and beta decay.