We report the first direct observation of the strange b baryon (). We reconstruct the decay J/-, with J/µ+µ-, and --p-- in p collisions at =1.96 TeV. Using 1.3 fb-1 of data collected by the D0 detector, we observe 15.2±4.4(stat)(syst) candidates at a mass of 5.774±0.011(stat)±0.015(syst) GeV. The significance of the observed signal is 5.5, equivalent to a probability of 3.3×10-8 of it arising from a background fluctuation. Normalizing to the decay bJ/, we measure the relative rate =0.28±0.09(stat)(syst).
Borissov developed and implemented a special version of his offline tracking algorithm in the search for Xi_b which considerably increased the efficiency of the signal selection and was crucial for its observation. This is the first observation of a baryon containing quarks from all three families. RAE_import_type : Journal article RAE_uoa_type : Physics
