Double strangeness production in [formula omitted] annihilation at low energy

Abstract

The final results of the search of double strangeness final states, i.e. the production of two strange quarks and two antistrange quarks, the latter carried by the produced strange hadrons, from the analysis of a sample of 7.8·10 5 low energy ( P≤0.9 GeV/c ) antiproton annihilations on Xenon nuclei, are presented. An overall number of 33 double strangeness events were found and are discussed. The corresponding yields are all at the level of 10 −4, a value unexpectedly high with respect a naive expectation based on measurements of simple strangeness production on a free nucleon. However, conventional processes in nuclear matter described by the intranuclear cascade models seem to be able to explain this apparent strangeness enhancement. Two mechanisms play a special role, as checked also by a Monte Carlo calculation: the p ̄ N→K K ̄ ω reaction, followed by the associated strangeness production ωN→ KY, and the Ξ-formation process, followed by ΞN→ ΛΛ.