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Annihilation

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	Annihilation
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	Topics Annihilation Topic Home Annihilation is defined as "total destruction" or "complete obliteration" of an object; having its root in the Latin nihil (nothing). A literal translation is "to make into nothing". Annihilation is the opposite of exnihilation, which means "to create something out of nothing". In physicsPhysics Physics , the most fundamental physical science, is concerned with the underlying principles of the natural world.... , the word is used to denote the process that occurs when a subatomic particleSubatomic particle A subatomic particle is a particle smaller than an atom: it may be elementary or composite.... collides with its respective antiparticleAntiparticle Corresponding to each kind of particle, there is an associated antiparticle with the same mass and opposite charges.... . Since energy and momentum must be conserved, the particles are not actually made into nothing, but rather into new particles. Antiparticles have exactly opposite additive quantum numberFacts About Quantum number A quantum number describes the energies of electrons in atoms.... s from particles, so the sums of all quantum numbers of the original pair are zero. Hence, any set of particles may be produced whose total quantum numbers are also zero as long as conservation of energyConservation of energy Conservation of energy states that the total amount of energy in an isolated system remains constant.... and conservation of momentum are obeyed. During a low-energy annihilation, photonPhoton In modern physics, the photon is the elementary particle responsible for electromagnetic phenomena.... production is favored, since these particles have no mass. However, high-energy particle colliders produce annihilations where a wide variety of exotic heavy particles are created. Examples of annihilation This is an example of renormalizationRenormalization In quantum field theory and the statistical mechanics of fields, renormalization refers to a collection of techniques used t... in quantum field theoryQuantum field theory Quantum field theory is the quantum theory of fields.... — the field theory being necessary because the number of particles changes from one to two and back again. When a low-energy electronElectron The electron is a fundamental subatomic particle that carries an electric charge.... annihilates a low-energy positronPositron The positron is the antiparticle or the antimatter counterpart of the electron.... (anti-electron), they can only produce two or more gamma rayGamma ray Gamma rays are an energetic form of electromagnetic radiation produced by radioactive decay or other nuclear or subatomic p... photonPhoton Summary In modern physics, the photon is the elementary particle responsible for electromagnetic phenomena.... s, since the electron and positron do not carry enough mass-energy to produce heavier particles. However, if one or both particles carry a larger amount of kinetic energy, various other particle pairs can be produced. See electron-positron annihilationElectron-positron annihilation Electron-positron annihilation occurs when an electron and a positron collide.... . The annihilation (or decay) of an electron-positron pair into a single photon, e⁺ + e^- ? ?, cannot occur because energy and momentum would not be conserved in this process. The reverse reaction is also impossible for this reason, except in the presence of another particle that can carry away the excess energy and momentum. However, in quantum field theoryQuantum field theory Quantum field theory is the quantum theory of fields.... this process is allowed as an intermediate quantum state. Some authors justify this by saying that the photon exists for a time which is short enough that the violation of energy conservationConservation of energy Conservation of energy states that the total amount of energy in an isolated system remains constant.... can be accommodated by the uncertainty principleUncertainty principle In quantum physics, the Heisenberg uncertainty principle or the Heisenberg indeterminacy principle the latter name give... . Others choose to assign the intermediate photon a non-zero mass. (The mathematics of the theory are unaffected by which view is taken.) This opens the way for virtual pair production or annihilation in which a one-particle quantum state may fluctuate into a two-particle state and back again (coherent superposition). These processes are important in the vacuum stateVacuum state In quantum field theory, the vacuum state is the quantum state with the lowest possible energy.... and renormalizationRenormalization In quantum field theory and the statistical mechanics of fields, renormalization refers to a collection of techniques used t... of a quantum field theory. It also allows neutral particle mixing through processes such as the one pictured here. Notations See also Pair productionPair production Pair production refers to the creation of an elementary particle and its antiparticle, usually from a photon....