Beta particle

  Beta particles are high-energy, high-speed beta decay. They are designated by the Greek letter beta (β). There are two forms of beta decay, β⁻ and β⁺, which respectively give rise to the positron.

β⁻ decay (electron emission)

An unstable atomic nucleus with an excess of neutrino):

This process is mediated by the weak interaction. The neutron turns into a proton through the emission of a virtual W⁻ boson. At the quark level, W⁻ emission turns a down-type quark into an up-type quark, turning a neutron (one up quark and two down quarks) into a proton (two up quarks and one down quark). The virtual W⁻ boson then decays into an electron and an antineutrino.

Beta decay commonly occurs among the neutron-rich fission byproducts produced in nuclear reactors. Free neutrons also decay via this process. This is the source of the copious amount of electron antineutrinos produced by fission reactors.

β⁺ decay (positron emission)

  Unstable atomic nuclei with an excess of positron and an electron-type neutrino:

Beta plus decay can only happen inside nuclei when the absolute value of the binding energy of the daughter nucleus is higher than that of the mother nucleus.

Inverse beta decay is one of the steps in nuclear fusion processes that produce energy inside stars.

See also

• Electron
• Particle physics
• α (alpha) particles
• β (beta) particles
• Rays:
  • γ (gamma) rays
  • n (neutron) rays
  • δ (delta) rays
  • ε (epsilon) rays