Bs⁎BK vertex from QCD sum rules

The form factors and the coupling constant of the Bs⁎BK vertex are calculated using the QCD sum rules method. Three-point correlation functions are computed considering both K and B mesons off-shell and, after an extrapolation of the QCDSR results, we obtain the coupling constant of the vertex. We study the uncertainties in our result by calculating a third form factor obtained when the Bs⁎ is the off-shell meson, considering other acceptable structures and computing the variations of the sum rules' parameters. The form factors obtained have different behaviors but their simultaneous extrapolations reach to the same value of the coupling constant gBs⁎BK=10.6±1.7. We compare our result with other theoretical estimates.