SU(3) breaking of leading-twist K and K∗ distribution amplitudes-a reprise

We present new QCD sum rules for the leptonic decay constants fK and fK∥,⊥ of the K and K∗, respectively, and the SU(3) breaking quantities a1∥,⊥(K∗), the first Gegenbauer-moments of the leading-twist distribution amplitudes of K∗, including SU(3) breaking effects up to second order; we also confirm existing results for the sum rule for a1(K). The results for fK and fK∥ agree with experiment. Our predictions for fK⊥ and a1∥,⊥(K∗) are relevant for the calculation of K and K∗ form factors, for instance T1B→K∗, which determines the decay B→K∗γ, and for QCD factorisation calculations of nonleptonic B decays into strange mesons, for instance B→Kπ.