CP Violation in the $B^0_s$ system in LHCb

Latest LHCb measurements of $CP$ violation in the interference between mixing and decay are presented based on $pp$ collision data collected in 2011 at centre-of-mass energy $\sqrt{s}$ = 7TeV, corresponding to an integrated luminosity of 1.0fb$^{-1}$. A combination of about $27.6k$ $B_s^0\to J/\psi \phi$ and $7.4k$ $B_s^0\to J/\psi \pi\pi$ signal events yield the most accurate measurement of the $CP$-violating phase, $\phi_s^{c\overline{c}s}$. This is found to be $\phi_s^{c\overline{c}s}=0.01\pm0.07 {\rm \, (stat.)}\pm0.01 {\rm \, (syst.)}$ rad. The combination also yields the most accurate measurements of the average $B_s^0$ decay width and decay width difference. These are found to be $\Gamma_s=0.661\pm0.004 {\rm \, (stat.)}\pm0.006 {\rm \, (syst.)}$ps$^{-1}$ and $\Delta\Gamma_s=0.106\pm0.011 {\rm \, (stat.)}\pm0.007 {\rm \, (syst.)}$ps$^{-1}$, respectively. The first measurement of the $CP$-violating phase in the $B_s^0 \to \phi\phi$ decay, $\phi_s^{s\overline{s}s}$, is found to be in the interval $[-2.46,-0.76]$rad at 68 % confidence level.