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We search for strange-pentaquark states that have been previously reported by other experiments--the Theta (1540)(+), Xi(5)(1860)(--), and Xi(5)(1860)(0)--in 123 fb(-1) of data recorded with the BABAR detector at the PEP-II e(+)e(-) storage ring. We find no evidence for these states and set 95% confidence level upper limits on the number of Theta(1540)(+) and Xi(5)(1860)(--) pentaquarks produced per e(+)e(-) annihilation into qq and Gamma(4S) decay. For qq events the Theta(1540)(+) [Xi(5)(1860)(--)] limit is about 8 [4] times lower than the rates measured for ordinary baryons of similar mass.  相似文献   

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Results on event and single particle characteristics are presented for the three most successful perturbative QCD+fragmentation models in the c.m. energy range 12.0≦W≦200 GeV. The models were optimised to describe the properties of the large sample of hadronic events obtained by TASSO atW=35 GeV. The energy evolution of the observables across the range spanned by the PETRA and PEP data, 12.0≦〈W〉≦41.5 GeV, is reasonably well described by all the models. However, for some quantities the predictions of the different models diverge at higher energies; distributions of observables are shown at c.m. energies of 93 and 200 GeV, where data are expected from thee + e ? colliders currently under construction. The ability to describe simultaneously, with the same parameter values, hadronic event features both at PETRA/PEP and LEP/SLC energies will provide a severe test of the models. The effects of top quark production on the event properties are illustrated for a top mass of 60 GeV/c2. Predictions are given for the rates of multijet events up toW=200 GeV, where ≧4-jet events dominate the cross section and will form a background to events containing heavy states which decay into hadron jets.  相似文献   

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