Fine-tuning in scalar meson decay with bound-state corrections

The glueball-quarkonia mixture decay amplitude has been evaluated, in the literature, by diagrammatic techniques for drawing quark lines and the quark-gluon vertex. In this paper we use an alternative approach which consists in a mapping technique, the Fock-Tani formalism, in order to obtain an effective Hamiltonian starting from microscopic interactions. An extra effect is present in this formalism associated to the extended nature of mesons: bound-state corrections, which introduces an additional decay amplitude and sets a fine-tuning procedure for general meson decay calculations. The $f_0(1500) \to \pi \pi$ channel shall be considered as numerical example of the procedure.