Antiparticle

Corresponding to each kind of particle, there is an associated antiparticle with the same mass and spin. Some particles, such as the photon, are identical to their antiparticle; such particles must have no electric charge, but not all charge-neutral particles are of this kind. The laws of nature were thought to be symmetric between particles and antiparticles until CP violation experiments found that time-reversal symmetry is violated in nature. The observed excess of baryons over anti-baryons in the universe is one of the primary unsolved problems in cosmology.

Related Topics:
Particle - Mass - Spin - Photon - Electric charge - CP violation - Time-reversal symmetry - Baryon - Cosmology

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Particle-antiparticle pairs can annihilate each other if they are in appropriate quantum states. They can also be produced in various processes. These processes are used in today's particle accelerators to create new particles and to test theories of particle physics. High energy processes in nature can create antiparticles. These are visible in cosmic rays and in certain nuclear reactions. The word antimatter properly refers to (elementary) antiparticles, composite antiparticles made with them (such as antihydrogen) and to larger assemblies of either.

Related Topics:
Quantum state - Particle accelerator - Particle physics - Cosmic ray - Nuclear reaction - Antimatter - Antihydrogen

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