Electron–positron annihilation

Electron–positron annihilation occurs when an electron (
e⁻
) and a positron (
e⁺
, 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 photons:

e⁻
 + 
e⁺
 → 
γ
 + 
γ

At high energies, other particles, such as B mesons or the W and Z bosons, can be created. All processes must satisfy a number of conservation laws, including:

• Conservation of electric charge. The net charge before and after is zero.
• Conservation of linear momentum and total energy. This forbids the creation of a single photon. However, in quantum field theory this process is allowed; see 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 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.