NEW UPPER LIMITS FOR H-PARTICLE PRODUCTION IN (P)OVER-BAR-XE ANNIHILATION AT LOW-ENERGY

A study of the reactions (p) over bar Xe --> K(+)K(+)X, (p) over bar X e --> K+H(H --> Sigma(-)p)X and (p) over bar Xe --> K+K+H(H --> Sigma( -)p)X was performed using the 700-litre xenon bubble chamber DIANA, ex posed to the 1 GeV/c antiproton beam of ITEP (Moscow). From a sample o f 7.8 . 10(5) antiproton annihilations at low energy in xenon nuclei 4 events were observed for the reaction (p) over bar Xe\ --> K(+)K(+)X at rest (P-(p over bar) less than or equal to 400 MeV/c) and 8 for the same reaction in flight (400 less than or equal to P-(p over bar) les s than or equal to 900 MeV/c). The corresponding probabilities turned out to be 3.1 . 10(-5) and 3.4 . 10(-5), respectively. No H-event was found in the two semi-inclusive reactions (p) over bar Xe --> K(+)HX a nd (p) over bar Xe --> K(+)K(+)HX. This lead to the upper limits 6 . 1 0(-6) and 8 . 10(-6) (90% C.L.), respectively. The corresponding upper limit for the fully inclusive reaction (p) over bar Xe --> HX turned out to be 1.2 . 10(-5) (90% C.L.), which is about one order of magnitu de lower than the actual value reported in the literature.