SU_f(3)-Symmetry Breaking Effects of the B\to K Transition Form Factor in the QCD Light-Cone Sum Rules

Abstract

We present an improved calculation of the $B\to K$ transition form factor with chiral current in the QCD light-cone sum rule (LCSR) 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 $S{U}_f(3)$-breaking effects. One-loop radiative corrections to the kaonic twist-2 contribution together with the leading-order twist-4 corrections are studied. The $S{U}_f(3)$ breaking effect is obtained, $\frac{F_{+}^{B\to K}(0)}{F_{+}^{B\to \pi }(0)}=1.16\pm 0.03$. By combining the LCSR results with the newly obtained perturbative QCD results that have been calculated up to $\mathcal{O}(1/m_b^2)$ in Ref.\cite{hwf0}, we present a consistent analysis of the $B\to K$ transition form factor in the large and intermediate energy regions.

Comments: 21 pages, 7 figures, some typo errors are corrected, to be published in PRD