Antiparticle

An antiparticle is the counterpart of a particle, with the same mass and opposite values for certain additive quantum numbers. When particle and antiparticle meet, they can annihilate into other particles.

Pair production: The creation of a particle and its antiparticle from energy or another interaction. It produces antiparticles while conserving energy, momentum, and quantum numbers.
Quantum number: A value specifying a measurable or conserved property of a quantum system. Antiparticles are identified by reversals of selected additive quantum numbers.
Positron: The positively charged antiparticle of the electron. It was the first antiparticle identified experimentally.
Majorana fermion: A fermion that is identical to its own antiparticle. It is the exception to the usual distinction between a particle and its antiparticle.
Matter–antimatter asymmetry: The observed excess of matter over antimatter in the universe. The scarcity of surviving antiparticles is a central cosmological puzzle.
Annihilation: A process in which particles and antiparticles transform into other particles or radiation. It is the characteristic interaction between a particle and its antiparticle.
Electric charge: A property of matter that determines its electromagnetic interactions. Electric charge reverses sign between charged particles and their antiparticles.
Antiproton: The negatively charged antiparticle of the proton. Its discovery established that composite particles also have antiparticles.
Photon: The electrically neutral quantum of the electromagnetic field. A photon is its own antiparticle, unlike an electron and positron.
Baryogenesis: The set of proposed processes that generated the universe’s excess of baryons over antibaryons. It seeks to explain why antiparticles did not survive in equal abundance.

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