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the operation of exchanging all particles that participate in any interaction for their corresponding antiparticles. Experience shows that strong interactions and electromagnetic interactions do not change upon charge conjugation; that is, strong and electromagnetic interactions between particles and corresponding antiparticles in the same state are identical. For example, the electromagnetic interaction of two positrons (or antiprotons) is exactly the same as that between two electrons (or protons). This means that for any process that takes place with some particles under the influence of strong or electromagnetic interaction, there exists exactly the same process for their antiparticles.
Weak interactions, in contrast to strong and electromagnetic interactions, change on charge conjugation. Symmetry between “right” and “left” directions in space (mirror symmetry) is also absent in processes of weak interaction. On violation of charge and mirror symmetry taken separately, there exists in weak interactions (at least to an accuracy of 0.1 percent) a symmetry with respect to the simultaneous accomplishment of both operations—charge conjugation and specular reflection: a process that transpires with some antiparticles as a result of weak interaction is a sort of mirror image of the analogous process that takes place with the particles.
S. S. GERSHTEIN