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antiparticle
subject			fact

antiparticle	has definition An elementary particle of opposite charge but otherwise identical to its partner. Most of the observable universe consists of particles and matter, as opposed to antiparticles and antimatter.
	has definition For every known type of particle, there exists an antiparticle with exactly the same mass, but with the opposite electric charge. When a particle and its antiparticle come together, they can always annihilate to form gamma rays. The antiparticle of an electrically neutral particle is sometimes the same as the original particle (e.g., photons) and sometimes it is distinct (e.g., neutrons).
	has definition Particles predicted by combining the theories of special relativity and quantum mechanics. For each particle, there must exist an antiparticle with the opposite charge, magnetic moment and other internal quantum numbers (e.g., lepton number, baryon number, strangeness, charm, etc.), but with the same mass, spin and lifetime. Note that certain neutral particles (such as the photon and π0) are their own antiparticles.
	has definition Atomic particles that have the same mass as, but opposite charge and orbital direction to, an ordinary particle. Thus, instead of negatively charged electrons, atoms of antimatter have positrons. A quantity of antimatter coming into contact with matter would "cancel out" - annihilate, with total conversion of mass to energy - an exact proportion of matter corresponding to the original quantity of antimatter, provided that the elements in the matter also corresponded with the "elements" in the antimatter, i.e., that the atoms were equivalent but opposite.
	has definition Particles with identical mass and spin as those of ordinary matter, but with opposite charge. Antimatter has been produced experimentally, but little of it is found in nature. Why this should be so is one of the questions that must be answered by any adequate theory of the early universe.
	is a kind of particle
particle	obeys uncertainty principle
	has frequency inversely proportional to the wavelength
	has wavelength inversely proportional to its momentum
	has charge
	has mass
physical object	has location or center of gravity
	has angular momentum
	has velocity
	has momentum
	has temperature
	has volume
	has extent
	has material

Kinds of antiparticle :

• antineutrino (5 facts) - The antiparticle of a neutrino.
• antineutron (6 facts) - The antiparticle of a neutron. A neutron and antineutron both have the same mass and zero electric charge, but can be differentiated by their interactions: a neutron and an antineutron can annihilate into gamma rays, while two neutrons cannot.
• antiproton (7 facts) - The antiparticle of a proton, identical in mass and spin but of opposite (negative) charge.
• antiquark (5 facts) - The antiparticle of the quark.
• positron (10 facts) (antielectron) - The antiparticle of the electron, discovered by Anderson in 1934. It has the same mass and spin as the electron, but opposite charge and magnetic moment.

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