Light scalar mesons in QCD sum rules with inclusion of instantons

The light scalar meson nonet above 1 GeV (i.e., the a0, K0* and f0) are studied within the framework of QCD sum rules. In conventional QCD sum rules, the calculated masses of this nonet are degenerate, and the mass of K0* is always larger than the a0 in contradiction with the observed spectrum. After improving the correlation function by including instanton effects, the masses are well separated from each other. In particular, our results show glueball content plays an important role in the underlying structure of f0(1500). The sensitivity of the results on the instanton density is also discussed.