Perturbative QCD correction to the B → π transition form factor

We report on the perturbative O(αs) correction to the light-cone QCD sum rule for the B → π transition form factor f+. The correction to the product fBf+ in leading twist approximation is found to be about 30%, that is similar in magnitude to the corresponding O(αs) correction in the two-point sum rule for fB. The resulting cancellation of large QCD corrections in f+ eliminates one important uncertainty in the sum-rule prediction for this form factor.