Polarizations of two vector mesons in B decays
  Inspired by the small longitudinal polarizations (LPs) of $B\to K^* \phi$ decays observed by BELLE and BABAR, we revise the theoretical uncertainties of perturbative QCD approach for determining hard scales of B decays, we find that the LPs of $B\to K^* \phi$ could approach to 60% while the branching ratios (BRs) could be around $9\times 10^{-6}$. In addition, we also study the BRs and polarization fractions of $B\to \rho (\omega) \rho (\omega)$ and $B\to \rho (\omega) K^*$ decays. For those tree dominant and color-allowed processes in $B\to \rho (\omega) \rho (\omega)$ decays, we get that the BRs of $(\rho^{+} \rho^{-}, \rho^{0} \rho^{+}, \omega \rho^{+})$ are $(23.06, 11.99, 14.78)\times 10^{-6}$ while their LPs are close to unity. Interestingly, due to significant tree contributions, we find that the BR(LP) of $\rho^{-} K^{*+}$ could be around $10.13 \times 10^{-6}(60%)$; and due to the tree and electroweak penguin, the BR(LP) of $\omega K^{*+}$ could be around $5.67 \times 10^{-6}(61%)$. 
Chuan-Hung Chen