Measurement of the Lambda(b) lifetime in the exclusive decay Lambda(b) ---> J/psi Lambda

We have measured the λb lifetime using the exclusive decay λb→J/ψλ, based on 1.2 fb-1 of data collected with the D0 detector during 2002-2006. From 171 reconstructed λb decays, where the J/ψ and λ are identified via the decays J/ψ→μ+μ- and λ→pπ, we measured the λb lifetime to be τ(λb)=1.218-0.115+0.130(stat)±0.042(syst) ps. We also measured the B0 lifetime in the decay B0→J/ψ(μ+μ-)KS0(π+π-) to be τ(B0)=1.501-0.074+0.078(stat)±0.050(syst) ps, yielding a lifetime ratio of τ(λb)/τ(B0)=0.811-0.087+0.096(stat)±0.034(syst)