Kaon distribution amplitude from QCD sum rules

We present a new calculation of the first Gegenbauer moment a₁K of the kaon light cone distribution amplitude. This moment is determined by the difference between the average momenta of strange and nonstrange valence quarks in the kaon. To calculate a₁K, QCD sum rule for the diagonal correlation function of local and nonlocal axial-vector currents is used. Contributions of condensates up to dimension six are taken into account, including O(αₛ)-corrections to the quark-condensate term. We obtain a₁K=0.05±0.02, differing by the sign and magnitude from the recent sum rule estimate from the nondiagonal correlation function of pseudoscalar and axial-vector currents. We argue that the nondiagonal sum rule is numerically not reliable. Furthermore, an independent indication for a positive a₁K is given, based on the matching of two different light cone sum rules for the K→π form factor. With the new interval of a₁K, we update our previous numerical predictions for SU(3)-violating effects in B₍ₛ₎→K form factors and charmless B decays.