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


















