Determination of the angle γ from nonleptonic B_c to D_s D⁰ decays

We note that the two body nonleptonic pure tree decays $B_c^\pm \to D_s^\pm D^0(\bar D^0)$ and the corresponding vector-vector modes $B_c^\pm \to D_s^{* \pm} D^{*0}(\bar D^{* 0}) $ are well suited to extract the weak phase $\gamma$ of the unitarity triangle. The CP violating phase $\gamma$ can be determined cleanly as these decay modes are free from the penguin pollutions.