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 $m_G=1.53\mathrm{}\pm 0.2\hspace{0.5em}\mathrm{GeV}$ is less sensitive to the instanton contributions then the glueball coupling (residue) $f_G=1.01\mathrm{}\pm 0.25\hspace{0.5em}\mathrm{GeV},$ 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.

• Received 1 May 2000

DOI:https://doi.org/10.1103/PhysRevD.64.034015