object

antiproton

The antiproton is the antimatter counterpart of the proton, with the same mass but negative charge.
32 related articles

Description

The antiproton is the antimatter counterpart of the proton: it has the same mass and spin, but carries a negative electric charge. When an antiproton meets a proton, they annihilate, converting their entire mass into energy in the form of other particles, typically pions. This makes antiprotons a key player in understanding the fundamental asymmetry between matter and antimatter in the universe — why we observe a universe made almost entirely of matter, when the Big Bang should have produced equal amounts of both.

History

The antiproton was predicted by Paul Dirac in 1933 as a consequence of his relativistic equation for the electron, which implied the existence of positively charged electrons (positrons) and, by extension, antiprotons. It was first observed experimentally in 1955 by Owen Chamberlain, Emilio Segrè, and colleagues at the University of California, Berkeley, using the Bevatron particle accelerator.

How it works

Antiprotons are produced in high-energy collisions, such as those at CERN's Antiproton Decelerator, where protons are smashed into a metal target. The resulting antiprotons are slowed down and can be trapped using electric and magnetic fields. Their properties are studied by comparing them directly with protons, for example by measuring their mass and charge with extreme precision. In experiments like ALPHA, antiprotons are combined with positrons to form antihydrogen atoms, allowing tests of whether antimatter behaves identically to matter under gravity and spectroscopy.

In practice

Antiprotons are used in particle physics research to test fundamental symmetries, and are also explored for potential medical applications, such as in antiproton therapy for cancer treatment, where their annihilation could deposit energy more precisely than conventional proton therapy.

Fun fact

When an antiproton and a proton annihilate, the energy released is about 1.9 gigaelectronvolts, which is roughly the rest energy of two protons, and this energy appears as a burst of pions that can be detected.

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Related articles · 32

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HEP Experiment2026-08-122 minarXiv:2608.11795express
Antiprotons: Bounce or Annihilate?
The antiproton is the mirror twin of the proton: same mass, but negative charge. When it hits matter, it usually annihilates instantly — disappearing in a burst of energy upon colliding with an atomic nucleus.
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Antimatter in Galaxies: An Unexpected Trace from the Early Universe
In the first moments after the Big Bang, matter and antimatter should have been created in equal amounts. But today, everything around us is ordinary matter, and antimatter is almost nowhere to be found. Where did it all go? The standard answer: a tiny imbalance in favor of matter wiped out almost all antimatter.
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Cosmic Light Changes Polarization
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Dark Matter Speaks in Gamma-Ray Light
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How to Spot Hidden Magnetism by Symmetry
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A giant tank of ultrapure water sits deep underground in Japan. Its walls are lined with thousands of light-sensitive sensors that catch faint flashes — the traces of ghostly particles passing through the water.
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HEP Phenomenology2026-05-182 minarXiv:2605.18944express
The Invisible Particle Conductor
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Dark Matter Changes the Face of Neutrinos
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Magnetic charge hides in layers of matter
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HEP Phenomenology2026-04-231 minarXiv:2604.21968express
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A Mirror for Antiprotons
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