ρD∗D∗ vertex from QCD sum rules

We calculate the form factors and the coupling constant in the ρD∗D∗ vertex in the framework of QCD sum rules. We evaluate the three point correlation functions of the vertex considering both ρ and D∗ mesons off-shell. The form factors obtained are very different but give the same coupling constant: gρD∗D∗=6.60±0.31. This number is 50% larger than what we would expect from SU(4) estimates.