Hyperon and antihyperon production in p̄-p collisions at 7 BeV/c

Production of hyperons and antihyperons in the interactions of 6.935 BeV/c antiprotons with protons has been studied. A total of 80 000 pictures taken with the Brookhaven National Laboratory 80-in. liquid-hydrogen bubble chamber have been analyzed for all possible final states involving the production of a hyperon and/or an antihyperon. The total cross section for events in this category is 1.3±0.1 mb. Reactions leading to two-, three-, or four-body final states involving Λ or hyperons (or their antiparticles) were produced highly peripherally. The angular distribution of the ΛΛ̄ final state can be fitted to K* (888) exchange when the absorptive effect of competing channels is taken into account. Ratios among cross sections of various hyperon-antihyperon pair states agree with predictions from SU3 symmetry, assuming a dominant K or K* exchange and an F-type coupling. Charge ratios of events with ± and Y1*± (1385) are also consistent with single-particle-exchange models. We have examined the mass spectra of all possible mass combinations of all possible final states. The Y1* (1385) was by far the most prominent resonance produced, and production of Y0* (1405) and Y0* (1520) was also observed. Although the energy available in the production center-of-mass system is 3.86 BeV, there was no statistically significant evidence for the production of any new meson or baryon resonance. A thorough search has been made for Ω- and Ω̄+ particles, but no event was found to be consistent with their production and decay.