Measurement of direct $\mathcal{CP}$ violation in charmless charged two-body $B$ decays at LHCb

Using data collected by the LHCb detector during the 2010 run, we reconstruct a sample of the main charmless charged two-body $B$ hadron decay modes, namely $B^0 \rightarrow \pi^+\pi^-$, $B^0 \rightarrow K^+\pi^-$, $B^0_s \rightarrow K^+K^-$, $B^0_s \rightarrow \pi^+K^-$, $\Lambda_b \rightarrow p K^-$ and $\Lambda_b \rightarrow p \pi^-$. We provide preliminary values of the direct $\mathcal{CP}$ asymmetries $A_{CP}(B^0 \rightarrow K^+\pi^-)=-0.074 \pm 0.033 \pm 0.008$ and $A_{CP}(B^0_s \rightarrow \pi^+K^-)=0.15 \pm 0.19 \pm 0.02$, where the first uncertainty is statistical and the second is systematic.