Antiproton Annihilations in Propane

An experiment to study the p̄ annihilation process at 1.05 Bev/c was performed with the Lawrence Radiation Laboratory 30-in. propane bubble chamber. It was observed that the K-meson production in annihilation events rises sharply with the increase in energy, namely from 4±{}1% for annihilations at or near "rest" to 8±{}1%. On the other hand, the pion multiplicity was not observed to increase appreciably with the increase of available energy. We have found a pion multiplicity of 5.0±{}0.2. These numbers are discussed in this paper and compared with existing models for the p̄ annihilation process. It is pointed out that with further increase in bombarding energy different models may differ appreciably in the above quantities.We have observed a p̄-H annihilation cross section of 51±{}10 mb and a p̄-C annihilation cross section of 368±{}60 mb at a p̄ momentum of 1.05 Bev/c. Crude determinations of the p̄ charge-exchange process---which turns out to be forward peaked--- and of p̄ inelastic-scattering events leading to pion production are also discussed.