The J/ψDD vertex in QCD sum rules

The J/psiDD form factor is evaluated in a QCD sum rule calculation for both D and J/psi off-shell mesons. We study the double Borel sum rule for the three point function of two pseudoscalar and one vector meson current. We find that the momentum dependence of the form factors is different if the D or the J/psi meson is off-shell, but they lead to the same coupling constant in the J/psiDD vertex. (C) 2002 Published by Elsevier Science B.V.