Abstract
The impact of QCD instantons on scalar glueball properties is studied in the framework of an instanton-improved operator product expansion (IOPE) for the ${0}^{++}$ glueball correlation function. Direct instanton contributions are found to strongly dominate over those from perturbative fluctuations and soft vacuum fields. All IOPE sum rules, including the one involving a subtraction constant, show a high degree of stability and are, in contrast to previous glueball sum rules, consistent with the low-energy theorem for the zero-momentum correlator. The predicted glueball mass ${m}_{G}=1.53\ifmmode\pm\else\textpm\fi{}0.2 \mathrm{GeV}$ is less sensitive to the instanton contributions then the glueball coupling (residue) ${f}_{G}=1.01\ifmmode\pm\else\textpm\fi{}0.25 \mathrm{GeV},$ which increases by about half an order of magnitude. Both glueball properties are shown to obey scaling relations as a function of the average instanton size and density.
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