Analysis of the strong coupling constant

In this article, we calculate the form factors and the coupling constant of the vertex $$D_{s}^{*}D_{s}\phi $$ using the three-point QCD sum rules. We consider the contributions of the vacuum condensates up to dimension 7 in the operator product expansion. And all possible off-shell cases are considered, $$\phi $$, $$D_{s}$$ and $$D_{s}^{*}$$, resulting in three different form factors. Then we fit the form factors into analytical functions and extrapolate them into time-like regions, which giving the coupling constant for the process. Our analysis indicates that the coupling constant for this vertex is $$G_{D_{s}^{*}D{_{s}}\phi }=4.12\pm 0.70\,\mathrm{GeV}^{-1}$$. The results of this work are very useful in the other phenomenological analysis. As an application, we calculate the coupling constant for the decay channel $$D_{s}^{*}\rightarrow D_{s}\gamma $$ and analyze the width of this decay with the assumption of the vector meson dominance of the intermediate $$\phi (1020)$$. Our final result about the decay width of this decay channel is $$\Gamma =0.59\pm 0.15\,\mathrm{keV}$$