Flavour Tagging at LHCb

The identification of the flavour of reconstructed Bd and Bs mesons at production is necessary for the measurements of oscillations and time-dependent CP asymmetries. The calibration and performance of opposite-side flavour tagging algorithms have been developed using simulated events and optimized and calibrated with different flavour specific B decays with $\sim$1 fb$^{–1}$ of data collected in pp collisions at $\sqrt{s}$ = 7 TeV during the 2011 physics run. Using flavour tagging LHCb has performed, among others, new measurements of Delta m_s, of the CP violating Bs mixing phase $\varphi_{s}$ and of direct and mixing-induced CP violation in $B \to hh$ decays.