Annihilation
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- For other senses of this word, see annihilation (disambiguation).
Annihilation is defined as "total destruction" or "complete obliteration" of a particular object. Usually, annihilation of an atomic or subatomic particle, occurs when such a particle collides with its respective antiparticle. Since antiparticles have exactly opposite quantum numbers from particles, their total quantum numbers are zero. Hence, any set of particles may be produced whose total quantum numbers are also zero; this could include any particles (if accompanied by their antiparticles) as long as conservation of energy and conservation of momentum are obeyed.
During a low-energy annihilation, photon production is favored, since these particles have no rest mass. However, high-energy particle colliders produce annihilations where a wide variety of exotic heavy particles are created.
Examples of annihilation
- When a low-energy electron annihilates a low-energy positron (anti-electron), it yields gamma rays only, since these particles do not carry enough mass-energy to produce heavier particles. See electron-positron annihilation.
- The single-photon annihilation of an electron-positron pair, e+ + e- → γ cannot occur because it is impossible to conserve energy and momentum together in this process. The reverse reaction is also impossible for this reason. However, in quantum field theory this process is allowed as an intermediate quantum state for times short enough that the violation of energy conservation can be accommodated by the uncertainty principle. This opens the way for virtual pair production or annihilation in which a one particle's quantum state may fluctuate into a two particle state and back again. These processes are important in the vacuum state and renormalization of a quantum field theory. It also opens the way for neutral particle mixing through processes such as the one pictured on the right: which is a complicated example of mass renormalization.cs:Anihilace
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