Counterparts of ordinary subatomic particles, which have the same mass and spin but opposite charge, magnetic moment, and any other internal attributes (including lepton, baryon, strangeness, and charm quantum numbers). Each particle has a corresponding antiparticle, although certain purely neutral particles, such as photons and π° mesons, are their own antiparticles. The antiparticles of the electron, proton, and neutron are the positron, antiproton, and antineutron, respectively.
An encounter between an electron and a positron results in the instantaneous total conversion of the mass of both – annihilation – into energy in the form of gamma rays. When a proton and an antiproton meet, however, the outcome is more complicated. Pions are produced, some of which decay to produce gamma radiation and others of which decay to produce muons and neutrinos plus electrons and positrons, which make more gamma rays.
Related entry• antimatter
Related category• PARTICLE PHYSICS
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