[an-tee-proh-ton, an-tahy-] 
| an elementary particle having negative charge equal in magnitude to that of the electron and having the same mass and spin as a proton; the antiparticle of the proton. |
| an·ti·pro·ton (ān'tē-prō'tŏn', ān'tī-) n. The antiparticle of the proton. |
| antiproton (ān'tē-prō'tŏn', ān'tī-) Pronunciation Key
The antiparticle that corresponds to the proton. |
antiproton
subatomic particle of the same mass as a proton but having a negative electric charge and oppositely directed magnetic moment. It is the proton's antiparticle. Antiprotons were first produced and identified in 1955 by Emilio Segre, Owen Chamberlain (for which they received the Nobel Prize for Physics in 1959), and coworkers by bombarding a copper target with high-energy protons from the proton synchrotron at the University of California at Berkeley. Antiprotons were predicted in the early 1930s, but their discovery had to wait for the technology of high-energy particle accelerators to reach the 6 billion electron-volt range. A collision of an antiproton with a proton results in mutual annihilation, but a near miss may produce by charge exchange an antineutron-neutron pair
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tiˌproʊ