\rho D^*D^* vertex from QCD sum rules

TL;DR

This paper uses QCD sum rules to calculate the form factors and coupling constant of the rho D* D* vertex, revealing a larger coupling than SU(4) estimates, with implications for meson interaction models.

Contribution

It provides the first detailed QCD sum rule calculation of the rho D* D* vertex form factors and coupling constant considering off-shell mesons.

Findings

Coupling constant g_{rho D* D*} = 6.6 ± 0.31

Form factors differ significantly for different off-shell mesons

Coupling constant exceeds SU(4) predictions by 50%

Abstract

We calculate the form factors and the coupling constant in the $\rho D^* D^*$ vertex in the framework of QCD sum rules. We evaluate the three point correlation functions of the vertex considering both $\rho$ and $D^*$ mesons off--shell. The form factors obtained are very different but give the same coupling constant: $g_{\rho D^* D^*} = 6.6 \pm 0.31$. This number is 50% larger than what we would expect from SU(4) estimates.