Measurement of the Λ b 0 Lifetime in the Decay Λ b 0 → J /ψΛ 0 with the D0 Detector

We present measurements of the Λ b 0 lifetime in the exclusive decay channel Λ b 0 →J/ψ Λ 0 , with J/ψ→μ + μ - and Λ 0 →p π- , the B 0 lifetime in the decay B 0 →J/ψ K S 0 with J/ψ→μ + μ - and K S 0 →π + π - , and the ratio of these lifetimes. The analysis is based on approximately 250 pb -1 of data recorded with the D0 detector in pp‾ collisions at √s=1.96 TeV. The Λ b 0 lifetime is determined to be t(Λ b 0 )=1.22 -0.18 +0.22 (stat)±0.04(syst) ps, theB 0 lifetime t(B 0 )=1.40 -0.10 +0.11 (stat) ±0.03(syst) ps, and the ratio t(Λ b 0 ) t(B 0 )=0.87 -0.14 +0.17 (stat)±0.03(syst). In contrast with previous measurements using semileptonic decays, this is the first determination of the Λ b 0 lifetime based on a fully reconstructed decay channel.