CERN Accelerating science

On the poster three LHCb results on B meson mixing using a datasample of 1 fb$^{-1}$ of $pp$ collisions at $\sqrt{s} =$ 7 TeV are presented. The B meson oscillation frequencies are measured as $\Delta m_d = 0.5156 \pm 0.0051 (\text{stat}) \pm 0.0033 (\text{syst}) \text{ps}^{-1}$ and $\Delta m_s = 17.768 \pm 0.023 (\text{stat}) \pm 0.006 (\text{syst}) \text{ps}^{-1}$. The CP violation observables in the decay channel $B^0 \rightarrow J/\psi K^0_S$ are determined as $S_{J/\psi K^0_S} = 0.73 \pm 0.07 (\text{stat})\pm 0.04 (\text{syst})$ and $C_{J/\psi K^0_S} = 0.03 \pm 0.09 (\text{stat})\pm 0.01 (\text{syst})$.