Electron-positron annihilation

Electron-positron annihilation is the process in which a positron (from B+ decay) collides with an electron resulting in their annihilation. Being of opposite charges and same mass they act as a collision of subatomic particle and anti-particle.

According to the law of conservation of energy, their masses are converted to 2 annihilation photons of energy (gamma rays) each of energy about 511 keV and moving in 2 opposite directions.

e− + e+ ------>  γ + γ

Where e− is the electron, e+ is the positron and γ are gamma rays emitted.

511 keV is the approximate amount of energy equivalent for the electron mass according to Einstein's famous equation:

E = mc2

Where E = energy , m = particle mass and c = velocity of light.

This process is of particular importance as it is the basis of positron emission tomography.

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Article information

rID: 16448
Section: Physics
Tags: refs, rewrite
Synonyms or Alternate Spellings:
  • Positron-electron annihilation

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