Observation Of Subthreshold Double Strangeness Production In (P)Over-Bar Annihilations On Xe Nuclei - Search For Stable H-Dibaryon

The double strangeness production has been observed in two final states of annihilation of antiprotons at momentum less than 0.9 GeV/c on Xe nuclei: K+K+X (8 events) and K+K0LAMBDAX (6 events). The probabilities of the reaction pXeBAR --> K+K+X vary from 2. 10(-5) (at rest) up to 7. 10(-5) (in flight). The reaction pXeBAR --> K+K0LAMBDAX is observed only in flight with probability 3 . 10(-4). The properties of the observed reactions are similar to those resulting from the cascade process with production of XI hyperon: pNBAR --> K*K*BAR, K* --> Kpi, K*NBAR --> XIK, XIN --> LAMBDALAMBDA. The new upper limit on the production probability of the stable H(S = -2) dibaryon in the reaction pXeBAR --> K+K+H(H --> SIGMA-p)X was obtained to be < 2 . 10(-5) (90%C.L.).