A measurement of the Λb0 lifetime

The lifetime of the Λb0 baryon has been measured using 3.6 million hadronic Z0 decays recorded by the OPAL detector at LEP from 1990 to 1994. A sample of Λb0 decays is obtained using partially reconstructed semileptonic decays involving Λc+ℓ− combinations, where the Λc+ is reconstructed from its decay to a pK−π+ final state. From the 69 ± 13Λc+ℓ− combinations attributed to Λb0 decays in this data sample, we measure τ(Λb0) = 1.14−0.19+0.22 ± 0.07 ps, where the errors are statistical and systematic, respectively.