Lifetime, Mixing and CPV in ATLAS

The latest results measured by the ATLAS experiment on lifetime, mixing and $CP$ violation in the $B^0$ and $B_s^0$ systems are presented. First, the measurement of the $B_s^0 \to J/\psi \phi$ decay parameters using 4.9 fb$^{-1}$ and 14.3$^{-1}$ of integrated luminosity collected by the ATLAS detector at the LHC in $p p$ collisions at $\sqrt{s} = 7$ TeV and $\sqrt{s} = 8$ TeV respectively is given. The measured values include the $CP$-violating phase $\phi_s$ and the width difference of the mass eigenstates $\Delta\Gamma_s$. The measurements for the 7 and 8 TeV data samples are combined, giving values of $\phi_s = -0.098 \pm 0.084~\mbox{(stat.)} \pm 0.040~\mbox{(syst.)}$ and $\Delta\Gamma_s = 0.083 \pm 0.011~\mbox{(stat.)} \pm 0.007~\mbox{(syst.)}$. The measured values agree with the Standard Model predictions. Second, the measurement of the relative width difference $\Delta \Gamma_d / \Gamma_d$ of the $B^0$--$\bar B^0$ system at $\sqrt{s} = 7$ TeV and $\sqrt{s} = 8$ TeV, corresponding to an integrated luminosity of 25.2 fb$^{-1}$ is presented. The measured value is $\Delta \Gamma_d / \Gamma_d = (-0.1 \pm 1.1~\mbox{(stat.)} \pm 0.9~\mbox{(syst.)}) \times 10^{-2}$. Currently, this is the most precise single measurement of $\Delta \Gamma_d / \Gamma_d$. It agrees with the Standard Model prediction and measurements by other experiments.