A QCD sum rules calculation of the $J/psi D_s^* D_s$ strong coupling constant

In this work, we calculate the form factors and the coupling constant of the strange-charmed vertex $J/psi D_s^* D_s$ in the framework of the QCD sum rules by studying their three-point correlation functions. All the possible off-shell cases are considered, $D_s$, $D_s^*$ and $J/psi$, resulting in three different form factors. These form factors are extrapolated to the pole of their respective off-shell mesons, giving the same coupling constant for the process. Our final result for the $J/psi D_s^* D_s$ coupling constant is $g_{J/psi D^*_s D_s} = 4.30^{+0.42}_{-0.37}text{GeV}^{-1}$.

$B_s B^* K $ and $B_s B K^*$ vertices using QCD sum rules

The form factors and the coupling constant of the $B_s B^* K $ and $B_s B K^*$ vertices are calculated using the QCD sum rules method. Three point correlation functions are computed considering both the heavy and light mesons off-shell in each vertex, from which, after an extrapolation of the QCDSR results at the pole of the off-shell mesons, we obtain the coupling constant of the vertex. The form factors obtained have different behaviors but their simultaneous extrapolation reach the same value of the coupling constant $g_{B_s B^* K}=8.41 pm 1.23 $ and $g_{B_s BK^*}=3.3 pm 0.5$. We compare our result with other theoretical estimates and compute the uncertainties of the method.

Obtaining the strong coupling constants g_{J/psi D_s D_s} and g_{phi D_s D_s} from QCD Sum Rules

The form factors and coupling constants of the meson vertices J/psi D_s D_s and phi D_s D_s were calculated using three point correlation functions within the QCD Sum Rules formalism. We have considered the cases where phi, D_s and J/psi mesons are off-shell obtaining, for each vertex, two different form factors and its corresponding coupling constants, namely g_{J/psi D_s D_s} = 6.20^{+0.97}_{-1.15} and g_{phi D_s D_s} = 1.85^{+0.22}_{-0.23}.