The role of antiprotons in cosmic-ray physics

Cosmic-ray antiprotons are studied, and the results of experiments to measure the energy spectrum of antiprotons from about 200 MeV to about 15 GeV are presented. The observed spectrum appears to be very hard. Upper limits to the fraction of antiprotons in cosmic-rays are derived. Possible mechanisms for the production of antiprotons are described, such as high-energy interactions, neutron oscillations, and the decay of super symmetric particles. Many of the propagation models considered can explain the present data at relativisitic energies. Implications of these models for other cosmic X-ray components such as positrons, deuterium, and He are also considered.