D-ASTERISK-D-PI AND B-ASTERISK-B-PI COUPLINGS IN QCD

We calculate the D*D and B*B couplings using QCD sum rules on the light cone. In this approach, the large-distance dynamics is incorporated in a set of pion wave functions. We take into account two-particle and three-particle wave functions of twist 2, 3, and 4. The resulting values of the coupling constants are gD*D=12.5 1 and gB*B =29 3. From this we predict the partial width (D*+ D0 +)=32 5 keV. We also discuss the soft-pion limit of the sum rules which is equivalent to the external axial field approach employed in earlier calculations. Furthermore, using gB*B and gD*D the pole dominance model for the B and D semileptonic form factors is compared with the direct calculation of these form factors in the same framework of ligh-cone sum rules. © 1995 The American Physical Society.