Electron-positron annihilation

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Electron-positron annihilation is the process that occurs when an electron (which is matter) and a positron (which is antimatter) collide. If they are both relatively at rest (which happens in an exotic but not uncommon form of matter called positronium), they destroy each other upon contact, and produce two gamma ray photons of 511 keV each which are emitted in opposite directions. If they are moving at different relative velocities, the energies of the photons emitted will be higher, in accordance with the conservation of 4-momentum (see below for important details). At higher relative velocities, other particle-antiparticle pairs can also be produced, since there is enough kinetic energy in the relative velocities to provide for the masses of those particles. At much higher relative velocities, there may be enough energy to produce a single neutral Z boson.

Photon pair production

Momentum-energy conservation dictates that at least two photons must be produced, and their 4-momentum must be the same as the 4-momentum of the colliding electron and positron.

The opposite process is known as pair production or matter creation.

See also

• Annihilation
• Electromagnetic spectrum (shows that the photons are in the high-energy range)ar:إبادة إلكترون-بوزيترون

es:Aniquilación positrón-electrón it:Annichilazione elettrone-positrone sl:anihilacija para