Measurement of the production fraction times branching fraction f(b→Λb)•B(Λb→J/ψΛ)

The Λb(udb) baryon is observed in the decay Λb→J/ψΛ using 6.1fb-1 of pp̄ collisions collected with the D0 detector at √s=1.96TeV. The production fraction multiplied by the branching fraction for this decay relative to that for the decay B0→J/ψKs0 is measured to be 0.345±0.034(stat) ±0.033(syst)±0.003(PDG). Using the world average value of f(b→B0)•B(B0→J/ψKs0)=(1.74±0.08)×10 -5, we obtain f(b→Λb) •B(Λb→J/ψΛ)=(6.01±0.60(stat) ±0.58(syst)±0.28(PDG))×10-5. This measurement represents an improvement in precision by about a factor of 3 with respect to the current world average. © 2011 American Physical Society.