Positron

Positron, elementary antimatter particle having a mass equal to that of an electron and a positive electrical charge equal in magnitude to the charge of the electron. The positron is sometimes called a positive electron or anti-electron. Electron-positron pairs can be formed if gamma rays with energies of more than 1 million electronvolts strike particles of matter. The reverse of the pair-production process, called annihilation, occurs when an electron and a positron interact, destroying each other and producing gamma rays.

The existence of the positron was first suggested in 1928 by the British physicist P. A. M. Dirac as a necessary consequence of his quantum-mechanical theory of electron motion. In 1932 the American physicist Carl Anderson confirmed the existence of the positron experimentally. See Atom; Elementary Particles.