Charmless B decays to η′ and η

Exclusive charmless B decays to η′ and η are studied in the standard effective Hamiltonian approach. The effective coefficients that take into account nonfactorizable effects in external and internal W-emission amplitudes are fixed by experiment. Factorization is applied to the matrix elements of QCD, electroweak penguin operators and next-to-leading corrections to penguin Wilson coefficients, which are renormalization-scheme dependent, are included, but the resultant amplitude is renormalization-scheme and -scale independent. We show that the unexpectedly large branching ratio of B± → η′K± measured by CLEO can be explained by the Cabibbo-allowed internal W-emission process b → ccs followed by a conversion of the cc pair into the η′ via gluon exchanges characterized by a decay constant of order −50 MeV. Implications are discussed. The mechanism of the transition cc → η′, if correct, will enhance the decay rates of B → η′K∗ by more than an order of magnitude. However, it plays only a minor role to the rare decays B → η′(η)π(ϱ). The predicted branching ratio of B± → ηπ± for positive ϱ is marginally ruled out by experiment, indicating that the favored Wolfenstein parameter ϱ is negative.