Measurement of $$\tau _\text {L}$$ using the $${B} _s^0 \rightarrow J/\psi \eta $$ decay mode

Abstract

AbstractUsing a proton–proton collision data sample collected by the LHCb detector and corresponding to an integrated luminosity of $$5.7~\text {fb}^{-1}$$ 5.7 fb - 1 , the lifetime of the light $${{B} ^0_{s}} $$ B s 0 mass eigenstate, $$\tau _{L}$$ τ L , is measured using the $$B^0_s \rightarrow J/\psi \eta $$ B s 0 → J / ψ η decay mode to be $$\begin{aligned} \tau _{\text {L}} = 1.445 \pm 0.016 \text {(stat)} \pm 0.008 \text {(syst)} \,\text {ps}. \end{aligned}$$ 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$$^{-1}$$ - 1 of integrated luminosity gives $$\begin{aligned} \tau _{\text {L}} = 1.452 \pm 0.014 \pm 0.007 \pm 0.002 \,\text {ps}, \end{aligned}$$ 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.