Measurements of the Bs0 and Λb0 lifetimes

Abstract This paper presents updated measurements of the lifetimes of the B s 0 meson and the Λ b 0 baryon using 4.4 million hadronic Z 0 decays recorded by the OPAL detector at LEP from 1990 to 1995. A sample of B s 0 decays is obtained using D s − l + combinations, where the D s − is fully reconstructed in the φπ − , K ∗0 K − and K − K 0 S decay channels and partially reconstructed in the φl − ν X decay mode. A sample of Λ b 0 decays is obtained using Λ c + l − combinations, where the Λ c + is fully reconstructed in its decay to a pK − π + final state and partially reconstructed in the Λ l + ν X decay channel. From 172±28 D s − l + combinations attributed to B s 0 decays, the measured lifetime is τ(B s 0 ) =1.50 +0.16 −0.15 ±0.04 ps , where the errors are statistical and systematic, respectively. From the 129±25 Λ c + l − combinations attributed to Λ b 0 decays, the measured lifetime is τ( Λ b 0 ) =1.29 +0.24 −0.22 ±0.06 ps , where the errors are statistical and systematic, respectively.