Measurement of the production fraction times branching fraction f(b --> Λ_b)B(Λ_b --> J/ψΛ)

Abstract

The Λ_b(udb) baryon is observed in the decay Λ_b --> J/ψΛusing 6.1 fb^{-1} of p\bar{p} collisions collected with the D0 detector at \sqrt{s}=1.96 TeV. The production fraction multiplied by the branching fraction for this decay relative to that for the decay B^0 --> J/ψK^0_s is measured to be 0.345 \pm 0.034 (stat.) \pm 0.033 (syst.) \pm 0.003 (PDG). Using the world average value of f(b --> B^0)B(B^0 --> J/ψK^0_s) = (1.74 \pm 0.08) \times 10^{-5}, we obtain f(b --> Λ_b)B(Λ_{b} --> J/ψΛ) = (6.01 \pm 0.60 (stat.) \pm 0.58 (syst.) \pm 0.28 (PDG)) \times 10^{-5}. This measurement represents an improvement in precision by about a factor of three with respect to the current world average.

Submitted to PRD-RC