B→K transition form factor up to $\mathcal{O}(1/m^2_b)$ within the k_T factorization approach

Abstract

We apply the k_T factorization approach to deal with the B→K transition form factor F^B→K _+,0(q²) in the large recoil regions. The B-meson wave functions Ψ_B and Ψ̄_B that include the 3-particle Fock states’ contributions are adopted to give a consistent PQCD analysis of the form factor up to $\mathcal{O} (1/m^2_b)$. It has been found that the two wave functions Ψ_B and Ψ̄_B can give sizable contributions to the form factor and should be kept for a better understanding of the B-meson decays. Next the contributions from different twist structures of the kaon wave function are discussed, including SU_f(3)-breaking effects. A sizable contribution from the twist-3 wave function Ψ_p is found, whose model dependence is discussed by taking two groups of parameters that are determined by different distribution amplitude moments obtained in the literature. It is also shown that F^B→K _+,0(0)=0.30±0.04 and [F^B→K _+,0(0)/F^B→π _+,0(0)]=1.13±0.02, which are more reasonable and consistent with the light-cone sum rule results in the large recoil regions.