B_s \to \rho(\omega) K^* with Perturbative QCD approach
  $B_s \to \rho(\omega) K^{\ast}$ are useful to determine the $B_s$ distribution amplitude, as well as constrain the CKM phase angle $\alpha$. We study these decays within the Perturbative QCD (PQCD) picture. In this approach, we calculate factorizable, non-factorizable, as well as annihilation diagrams. We find the branching ratio for $B_s \to \rho^+ K^{*-}$ is big to order $10^{-5}$, we also find there's large direct CP violation in $B_s(\bar B_s) \to \rho^0(\omega) \bar K^{*0}(K^{*0})$. Our predictions are consistent with those from other methods and current experiments. 
Jin Zhu, Yue-Long Shen, Cai-Dian Lu