Measurement of τL using the Bs0→J/ψη decay mode

Using a proton–proton collision data sample collected by the LHCb detector and corresponding to an integrated luminosity of 5.7 fb - 1 , the lifetime of the light B s 0 mass eigenstate, τ L , is measured using the B s 0 → J / ψ η decay mode to be τ L = 1.445 ± 0.016 (stat) ± 0.008 (syst) ps . A combination of this result with a previous LHCb analysis using an independent dataset corresponding to 3 fb - 1 of integrated luminosity gives τ L = 1.452 ± 0.014 ± 0.007 ± 0.002 ps , where the first uncertainty is statistical, the second due to the uncorrelated part of the systematic uncertainty and the third due to the correlated part of the systematic uncertainty.