Editing Electron–positron annihilation (section)

{{Short description|Collision causing gamma ray emission}}
[[File:Annihilation.png|thumb|330px|class=skin-invert-image|Naturally occurring electron-positron annihilation as a result of beta plus decay]]
{{Antimatter}}
'''Electron–positron annihilation''' occurs when an [[electron]] ({{SubatomicParticle|Electron}}) and a [[positron]] ({{SubatomicParticle|Positron}}, the electron's [[antiparticle]]) collide. At low energies, the result of the collision is the [[annihilation]] of the electron and positron, and the creation of energetic [[photon]]s:
:{{SubatomicParticle|Electron}}&nbsp;+&nbsp;{{SubatomicParticle|Positron}}&nbsp;→&nbsp;{{SubatomicParticle|Photon}}&nbsp;+&nbsp;{{SubatomicParticle|Photon}}

At high energies, other particles, such as [[B meson]]s or the [[W and Z bosons]], can be created. All processes must satisfy a number of [[Conservation law (physics)|conservation law]]s, including:
*[[Charge conservation|Conservation of electric charge]]. The net [[electric charge|charge]] before and after is zero.
*Conservation of [[momentum|linear momentum]] and total [[energy]]. This forbids the creation of a single photon. However, in [[quantum field theory]] this process is allowed; see [[annihilation#Examples|examples of annihilation]].
*Conservation of [[angular momentum]].
*Conservation of total (i.e. net) [[lepton number]], which is the number of leptons (such as the electron) minus the number of antileptons (such as the positron); this can be described as a [[matter#Conservation of matter|conservation of (net) matter]] law.

As with any two charged objects, electrons and positrons may also interact with each other without annihilating, in general by [[elastic scattering]].