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B → J / ψ K * decays in QCD factorization

2002; American Physical Society; Volume: 65; Issue: 9 Linguagem: Inglês

10.1103/physrevd.65.094023

1538-4500

Hai-Yang Cheng, Yong-Yeon Keum, Kwei-Chou Yang,

High-Energy Particle Collisions Research

The hadronic decay $\stackrel{\ensuremath{\rightarrow}}{B}J/\ensuremath{\psi}{K}^{*}$ is analyzed within the framework of QCD factorization. The spin amplitudes ${A}_{0},{A}_{\ensuremath{\Vert}},$ and ${A}_{\ensuremath{\perp}}$ in the transversity basis and their relative phases are studied using various different form-factor models for the $B\ensuremath{-}{K}^{*}$ transition. The effective parameters ${a}_{2}^{h}$ for helicity $h=0,+,\ensuremath{-}$ states receive different nonfactorizable contributions and hence they are helicity-dependent, contrary to naive factorization where ${a}_{2}^{h}$ 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 ${A}_{\ensuremath{\Vert}}$ 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 ${\ensuremath{\varphi}}_{\ensuremath{\Vert}}.$ Unlike $\stackrel{\ensuremath{\rightarrow}}{B}J/\ensuremath{\psi}K$ decays, the longitudinal parameter ${a}_{2}^{0}$ for $\stackrel{\ensuremath{\rightarrow}}{B}J/\ensuremath{\psi}{K}^{*}$ does not receive twist-3 corrections and is not large enough to account for the observed branching ratio and the fraction of the longitudinal polarization. Possible enhancement mechanisms for ${a}_{2}^{0}$ are discussed.