A QCD sum rules calculation of the ${\eta }_c{D}^{\ast }D$ and ${\eta }_c{D}_s^{\ast }{D}_s$ form factors and strong coupling constants

Abstract

We use the QCD sum rules for the three point correlation functions to compute the strong coupling constants of the meson vertices ${\eta }_c{D}^{\ast }D$ and ${\eta }_c{D}_s^{\ast }{D}_s$. 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 $g_{{\eta }_c{D}^{\ast }D}=5.23_{-1.38}^{+1.80}$ and $g_{{\eta }_c{D}_s^{\ast }{D}_s}=5.55_{-1.55}^{+1.29}$.

Comments: 22 pages, 3 figures