B^(ast)_(s1)B^(ast)K form factor from QCD sum rules

In this article, we calculate the form factors and the coupling constant of the $g_{B^{\ast}_{s1}B^{\ast} K}$ vertex in the framework of the three-point QCD sum rules. Three point correlation functions responsible for the vertex are evaluated by considering both $B^{\ast}$ and $K$ mesons as off-shell states. The form factors obtained are different if the $B^{\ast}$ or the $K$ meson is off-shell but give the same coupling constant.