Branching Ratios and Polarization in B-> VV,VA,AA Decays
  We present a detailed study of charmless two-body B decays into final states involving two vector mesons (VV) or two axial-vector mesons (AA) or one vector and one axial-vector meson (VA), within the framework of QCD factorization, where $A$ is either a $^3P_1$ or $^1P_1$ axial-vector meson. The main results are as follows. (i) In the presence of NLO nonfactorizable corrections, effective Wilson coefficients $a_i^h$ are helicity dependent. For some penguin-dominated modes, the constructive (destructive) interference in the negative-helicity (longitudinal-helicity) amplitude of the $B\to VV$ decay will render the former comparable to the latter and push up the transverse polarization. (ii) In QCD factorization, the transverse polarization fraction can be large for penguin-dominated charmless $VV$ modes by allowing for sizable penguin annihilation contributions. (iii) Using the measured $\bar K^{*0}\rho^-$ channel as an input, we predict the branching ratios and polarization fractions for other $\ov B\to \bar K^*\rho$ decays. (iv) The smallness of the axial-vector decay constant of the $^1P_1$ axial vector meson can be tested by measuring various $b_1\rho$ modes to see if $\Gamma(\bar B^0\to b_1^-\rho^+)\ll \Gamma(\bar B^0\to b_1^+\rho^-)$ and $\Gamma(B^-\to b_1^-\rho^0)\ll \Gamma(B^-\to b_1^0\rho^-)$. (v) For the penguin-dominated modes $a_1K^*$ and $b_1K^*$, it is found that the former are dominated by transverse polarization amplitudes, whereas the latter are governed by longitudinal polarization states. 
Hai-Yang Cheng, Kwei-Chou Yang