A QCD sum rules calculation of the ηcD⁎D and ηcDs⁎Ds form factors and strong coupling constants

We use the QCD sum rules for the three point correlation functions to compute the strong coupling constants of the meson vertices ηcD⁎D and ηcDs⁎Ds. We consider perturbative and non-perturbative contributions, working up to dimension five on the OPE. The vertices were studied considering that each one of its three mesons are off-shell alternately. The vertex coupling constant is evaluated through the extrapolation of the three different form factors. The results obtained for the coupling constants are gηcD⁎D=5.23−1.38+1.80 and gηcDs⁎Ds=5.55−1.55+1.29.