Charmless B -> VV decays in QCD factorization implications of recent B -> phi K* measurement

In the heavy quark limit, both vector mesons in the charmless B --> VV deca y should have zero helicity and the corresponding amplitude is proportional to the form factor difference (A(1) - A(2)). The first observed charmless B --> VV mode, B --> phiK* indicates that the form factors A(1)(q(2)) and A (2)(q(2)) cannot be very similar at low q(2) as shown in some form-factor m odels. The approach of QCD-improved factorization implies that the nonfacto rizable correction to each partial-wave or helicity amplitude is not the sa me: the effective parameters oi vary for different helicity amplitudes. The leading-twist nonfactorizable corrections to the transversely polarized am plitudes vanish in the chiral limit and hence it is necessary to take into account twist-3 distribution amplitudes of the vector meson in order to hav e renormalization scale and scheme independent predictions. Branching ratio s of B --> VV decays are calculated in two different models for form factor s, and the predicted decay rates are different by a factor of 1.5 similar t o 2. Owing to the absence of (S - P)(S + P) penguin contributions to the W- emission amplitudes, tree-dominated decays tend to have larger branching ra tios than the penguin-dominated ones. (C) 2001 Published by Elsevier Scienc e B.V.