Positron

:This article is about the positron particle. For the computer game, see Positron (game).

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The positron is the antiparticle or the antimatter counterpart of the electron. The positron has an electric charge of +1, a spin of 1/2, and the same mass as an electron. When a positron annihilates with an electron, their mass is converted into energy in the form of two gamma ray photons. (See electron-positron annihilation)

Related Topics:
Antiparticle - Antimatter - Electron - Electric charge - Spin - Annihilate - Energy - Gamma ray - Photon - Electron-positron annihilation

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A positron may be generated by positron emission radioactive decay, or the interaction of photon with a charged particle (such as an atom's nucleus) with energy greater than 2 mec2 = 2×0.511 MeV = 1.022 MeV with matter (me represents the mass of one electron and c is the speed of light in vacuum). This process is called pair production, as it generates one electron and one positron from the energy of the photon.

Related Topics:
Positron emission - Photon - MeV - Speed of light - Pair production

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The existence of positrons was first postulated in 1928 by Paul Dirac as an inevitable consequence of the Dirac equation. In 1932, positrons were observed by Carl D. Anderson, who gave the positron its name. Anderson also unsuccessfully suggested renaming electrons "negatrons." The positron was the first evidence of antimatter and was discovered by passing cosmic rays through a gas chamber and a lead plate surrounded by a magnet to distinguish the particles by bending differently charged particles in different directions.

Related Topics:
1928 - Paul Dirac - Dirac equation - 1932 - Carl D. Anderson - Electrons - Antimatter

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Today, positrons are produced in enormous numbers in accelerator physics laboratories and used in electron-positron colliders.

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