LHCb: Direct CP-asymmetries in $B^0K\pi$and $B_s\pi\pi K$ decays at LHCb

The LHCb experiment is designed to perform flavour physics measurements at the Large Hadron Collider. Using data collected during the 2010 run, we reconstructed a sample of $H_b \to h^+h^{'-}$ decays, where $H_b$ can be either a $B^0$ meson, a $B^s_0$ meson or a $\Lambda_b$ baryon, while h and $h^’$ stand for $\pi$, K or p. Such decays are sensitive probes of the Cabibbo-Kobayashi-Maskawa matrix and have the potential to reveal the presence of New Physics. We present preliminary measurements of the direct CP asymmetries in the $B^0 \to K^+\pi^-$ and $B_s^0 \to \pi^+ K^-$ decays.