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

Abstract

Abstract Using 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.