B→K1γ and tests of factorization for two-body non-leptonic B decays with axial-vector mesons

The large branching ratio for B→K1γ recently measured at Belle implies a large B→K1 transition form factor and large branching ratios for non-leptonic B decays involving an axial-vector meson. In this Letter we present an analysis of two-body B decays with an axial-vector meson in the final state using naive factorization and the B→K1 form factors obtained from the measured radiative decays. We find that the predicted B→J/ψK1 branching ratio is in agreement with experiment. We also suggest that the decay rates of B→K1π, B→a1K and B→b1K could be used to test the factorization ansatz.