Time-dependent asymmetries in Bs decays at LHCb

The LHCb experiment will search for New Physics in Bs mixing. The Bs mixing phase will be extracted from the measurement of the time-dependent CP asymmetry in exclusive Bs decays governed by the $b \to c\bar{c}s$ quark level transition. Large New Physics effects can be discovered or excluded with the data collected during the very first physics run of LHC. Based on Monte Carlo simulations of the LHCb detector, the expected sensitivity with 2 fb$^{-1}$ on the CP-violation parameter $\phi_s$, is $\sigma(\phi_s)$ = 0.022.