Branching fractions, polarisation and asymmetries of B→VV decays

Abstract We calculate the hard-scattering kernels relevant to the negative-helicity decay amplitude in B decays to two vector mesons in the framework of QCD factorisation. We then perform a comprehensive analysis of the 34 B → V V decays, including B s decays and the complete set of polarisation observables. We find considerable uncertainties from weak annihilation and the non-factorisation of spectator-scattering. Large longitudinal polarisation is expected with certainty only for a few tree-dominated colour-allowed modes, which receive small penguin and spectator-scattering contributions. This allows for an accurate determination of the CKM angle α (or γ) from S L ρ ρ resulting in α = ( 85.6 −7.3 +7.4 ) ° . We also emphasize that the ρ K ∗ system is ideal for an investigation of electroweak penguin effects.