Perturbative QCD correction to the B → π transition form factor

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