Antiproton

Antiproton

The quark content of the antiproton.
Classification	Antibaryon
Composition	2 up antiquarks, 1 down antiquark
Statistics	Fermionic
Family	Hadron
Interactions	Strong, weak, electromagnetic, gravity
Symbol	p
Antiparticle	Proton
Theorised	Paul Dirac (1933)
Discovered	Emilio Segrè & Owen Chamberlain (1955)
Mass	1.67262192595(52)×10−27 kg[1] 938.27208943(29) MeV/c2[2]
Electric charge	−1 e
Magnetic moment	−2.7928473441(42) μN [3]
Spin	1⁄2
Isospin	−1⁄2

Antimatter
Antiparticles Positron Antiproton Antineutron Antihydrogen Antihelium Onia Antiprotonic hydrogen Antiprotonic helium Muonium True muonium Pionium Positronium Quarkonium
Concepts and phenomena Annihilation Baryogenesis Baryon asymmetry Comet CP violation Gravitational interaction Positron emission
Devices Cloud chamber Particle accelerator Antiproton decelerator Relativistic Heavy Ion Collider Penning trap
Uses Positron emission tomography Fuel Weapon
People and bodies Carl David Anderson Paul Dirac Andrei Sakharov CERN
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The antiproton,
p
, (pronounced p-bar) is the antiparticle of the proton. Antiprotons are stable, but they are typically short-lived, since any collision with a proton will cause both particles to be annihilated in a burst of energy.

The existence of the antiproton with electric charge of −1 e, opposite to the electric charge of +1 e of the proton, was predicted by Paul Dirac in his 1933 Nobel Prize lecture.^[4] Dirac received the Nobel Prize for his 1928 publication of his Dirac equation that predicted the existence of positive and negative solutions to Einstein's energy equation (${\displaystyle E=mc^{2}}$) and the existence of the positron, the antimatter analog of the electron, with opposite charge and spin.

The antiproton was first experimentally confirmed in 1955 at the Bevatron particle accelerator by University of California, Berkeley, physicists Emilio Segrè and Owen Chamberlain, for which they were awarded the 1959 Nobel Prize in Physics.

In terms of valence quarks, an antiproton consists of two up antiquarks and one down antiquark (
u

u

d
). The properties of the antiproton that have been measured all match the corresponding properties of the proton, with the exception that the antiproton has electric charge and magnetic moment that are the opposites of those in the proton, which is to be expected from the antimatter equivalent of a proton. The questions of how matter is different from antimatter, and the relevance of antimatter in explaining how our universe survived the Big Bang, remain open problems—open, in part, due to the relative scarcity of antimatter in today's universe.