Antiprotons and Antineutrons

Proton is the nucleus of hydrogen. What are the features of antiproton and where to look for it?

Emilio SegrŠ- looked for negatively charged particles with mass similar to that of a proton among particles generated from the bombardment of high-energy protons. They observed a starburst, resulting from annihilation.

proton + antiproton ® 4 pions-plus + 4 pions-minus.

Today, antiprotons are routinely produced by first accelerated to an energy of 120 billion electron volts (120 GeV) in the Main Injector, extracted and transported to a target area. The protons collide with a nickel target. The collisions in the target produce a wide range of secondary particles including many antiprotons. The antiprotons are focused using a lithum lens and are transported to the Debuncher ring where they are reduced in size by a process known as stochastic cooling. They are then transferred to the Accumulator ring for storage. Finally, when a sufficient number has been produced, the antiprotons are reinjected into the Main Injector and passed down into the Tevatron where they are accelerated simultaneously with a counterrotating beam of protons to an energy of nearly one trillion electron volts (1 TeV).

A year after the discovery of antiproton, found another reaction for proton antiproton,

proton + antiproton ® neutron + antineutron

 

Antihydrogen

A system consisting of an antielectron and an antiproton is an anti-hydrogen atom. As long as these atoms do not contact normal hydrogen atoms and they are stable theoretically.

The decays of antiparticles and antimatter are complicated, and we just begin to have a glimpse of the asymmetry between matter and antimatter. Charge-parity violation may be one of the reasons. See Matter and Antimatter for further information.

Web Resource Regarding Antimatter

E-mail: cchieh@uwaterloo.ca