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HK: Physik der Hadronen und Kerne
HK 16: Theory II
HK 16.1: Group Report
Tuesday, March 12, 2002, 16:45–17:15, A
Glueballs and Instantons — •Hilmar Forkel — Institut für Theoretische Physik, Uni Heidelberg, Philosophenweg 19, 69120 Heidelberg
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 mG=1.53± 0.2 GeV is less sensitive to the instanton contributions then the glueball coupling (residue) fG=1.01± 0.25 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.