Testing QCD sum rules on the light-cone in D→(π,K)ℓν decays

Abstract We compare the predictions for the form factors f + D → π , K ( 0 ) from QCD sum rules on the light-cone with recent experimental results. We find f + D → π ( 0 ) = 0.63 ± 0.11 , f + D → K ( 0 ) = 0.75 ± 0.12 and f + D → π ( 0 ) / f + D → K ( 0 ) = 0.84 ± 0.04 in very good agreement with experiment. Although the uncertainties of the form factors themselves are larger than the current experimental errors and difficult to reduce, their ratio is determined much more accurately and with an accuracy that matches that of experiment.