What does antiproton mean?
An antiproton is the antimatter counterpart of the proton, one of the fundamental particles that make up ordinary atomic nuclei. It has exactly the same mass as a proton but carries a negative rather than a positive electric charge, along with opposite values for other quantum properties such as baryon number. When an antiproton encounters a proton, the two annihilate each other, converting their combined mass into energy in the form of other particles and radiation. Antiprotons do not occur naturally on Earth except fleetingly from cosmic-ray collisions, so virtually all antiprotons studied by scientists must be created in high-energy particle accelerators and stored using magnetic traps. The word belongs to the technical vocabulary of particle physics, appearing in research literature, textbooks, and science reporting. Its study has been central to tests of symmetry between matter and antimatter, one of the deepest questions in modern physics.
nounThe antiparticle of the proton, having the same mass as a proton but a negative electric charge.
- The antiparticle of the proton: a subatomic particle with the same mass as a proton but a negative electric charge.
"When an antiproton meets a proton, the two annihilate in a burst of energy."
"Physicists at CERN slowed antiprotons in a magnetic trap to study their properties with unprecedented precision."
"The collision of a single antiproton with a hydrogen nucleus releases energy as both particles are annihilated."
Regular plural; typically used when discussing beams, storage rings, or populations of the particle in experimental contexts.
"The storage ring held billions of antiprotons circulating at nearly the speed of light."
Antiprotons don't occur naturally in any meaningful amount on Earth — every one used in experiments must be manufactured in particle accelerators, making them among the rarest and most expensive substances ever produced.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of antiproton
The term combines 'anti-', from Greek meaning 'against' or 'opposite', with 'proton', itself coined in the 1920s from the Greek 'protos' ('first'). The antiproton was predicted by Dirac's relativistic quantum theory and was experimentally discovered in 1955 at the University of California, Berkeley, by Owen Chamberlain and Emilio Segrè, who received the Nobel Prize in Physics for the work. Related 'anti-' coinages include antineutron, positron (the antiparticle of the electron), and the broader term antimatter.
How antiproton is actually used
Strictly a technical term of particle physics; it appears almost exclusively in scientific writing and journalism about physics research rather than everyday conversation.
Easily confused with antiproton
A proton carries a positive charge, whereas an antiproton is its antimatter counterpart with the same mass but a negative charge.