## SU{sub f}(3)-symmetry breaking effects of the B{yields}K transition form factor in the QCD light-cone sum rules

We present an improved calculation of the B{yields}K transition form factor with a chiral current in the QCD light-cone sum rule approach. Under the present approach, the most uncertain twist-3 contribution is eliminated. And the contributions from the twist-2 and the twist-4 structures of the kaon wave function are discussed, including the SU{sub f}(3)-breaking effects. One-loop radiative corrections to the kaonic twist-2 contribution together with the leading-order twist-4 corrections are studied. The SU{sub f}(3)-breaking effect is obtained, (F{sub +}{sup B{r_reversible}}{sup K}(0)/F{sub +}{sup B{r_reversible}}{sup {pi}}(0))=1.16{+-}0.03. By combining the light-cone sum rule results with the newly obtained perturbative QCD results that havemore »