LHCb: Tagged time-dependent angular analysis of $B^0_s \to J/\psi K^+ K^-$ at LHCb

The time-dependent CP-violating asymmetry in $B^0_s\to J/\psi K^{+}K^{-}$ decays is measured using $1.0^{-1}$ of $pp$ of collisions at $\sqrt{s}=7$ TeV collected with the LHCb detector. The decay time distribution of $B^0_s\to J/\psi K^{+}K^{-}$ is characterized by the decay widths $\Gamma_{\mathrm{H}}$ and $\Gamma_{\mathrm{L}}$ of the heavy and light mass eigenstates of the $B^0_s - \bar{B^0_s}$ system and by a CP-violating phase $\phi_s$. In a sample of approximately 27600 $B^0_s\to J/\psi K^{+}K^{-}$ events we measure $\phi_s \: = \: 0.068 \: \pm \: 0.091 \: \text{(stat)} \: \pm \: 0.011 \: \text{(syst)} \: \text{rad}$. We also find an average $B^0_s$ decay width $\Gamma_s \equiv (\Gamma_{\mathrm{L}}+\Gamma_{\mathrm{H}})/2 \: = \: 0.671 \: \pm \: 0.005 \: \text{(stat)} \: \pm \: 0.006 \: \text{(syst)} \: ps^{-1}$ and a decay width difference $\Delta \Gamma_s \equiv \Gamma_{\mathrm{L}} - \Gamma_{\mathrm{H}} \: = \: 0.100 \: \pm \: 0.016 \: \text{(stat)} \: \pm \: 0.003 \: \text{(syst)} \: ps^{-1}$. We present the combined fit result with $B_s^{0} \rightarrow J/\psi \pi^{+}\pi^{-}$ decays, giving the most precise single determination of $ \phi_s$, $\Delta\Gamma_{s}$ and $\Gamma_{s}$.