Strong decays of the glueball in a scaled effective Lagrangian

We calculate the scalar glueball decays into pipi, etaeta, etaeta' and KK within a modified version of the NJL model which implements the QCD trace anomaly. The glueball is assumed to be the f0(1500). It is coupled to the quarks due to its mixing with the scalar isoscalar mesons. The decay widths then contain a contribution coming from the triangle Feynman diagram. Moreover, they contain two additional contributions corresponding to the local decay of the glue component of the f0(1500): one comes from the process of regularization of the quark loop, the other from the interaction term a2chi2phgr2. Except for the etaeta' case, this local decay reduces the value of the width. The axial anomaly is introduced via a mass term for the eta'. As far as the lightest scalar glueball is identified with the f0(1500), the model cannot reproduce at the same time the dynamical properties of scalars and pseudoscalars. Since we do not include a model of confinement, we need to use a large quark mass (725 MeV) in our calculations. This leads to unphysical results for the two-pion decay width. A definitive test of our model awaits the introduction of a model of confinement, which we hope to include in a future work.