Decays in QCD Factorization

The hadronic decay B → J/ψK∗ is analyzed within the framework of QCD factorization. The spin amplitudes A0, A‖ and A⊥ in the transversity basis and their relative phases are studied using various different form-factor models for B −K∗ transition. The effective parameters a2 for helicity h = 0,+,− states receive different nonfactorizable contributions and hence they are helicity dependent, contrary to naive factorization where a2 are universal and polarization independent. QCD factorization breaks down even at the twist-2 level for transverse hard spectator interactions. Although a nontrivial strong phase for the A‖ amplitude can be achieved by adjusting the phase of an infrared divergent contribution, the present QCD factorization calculation cannot say anything definite about the phase φ‖. Unlike B → J/ψK decays, the longitudinal parameter a2 for B → J/ψK∗ does not receive twist-3 corrections and is not large enough to account for the observed branching ratio and the fraction of longitudinal polarization. Possible enhancement mechanisms for a2 are discussed.