Freiburg 1999 – scientific programme
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HK: Physik der Hadronen und Kerne
HK 18: Theorie III
HK 18.8: Talk
Tuesday, March 23, 1999, 15:45–16:00, A
Nucleon Magnetism and Instantons — •Hilmar Forkel1, Mountaga Aw2, and Manoj Banerjee2 — 1Inst. fuer Theor. Physik, Philosophenweg 19, D-69120 Heidelberg — 2Center for Theor. Physics, University of Maryland, College Park, MD 20742-4111, U.S.A.
We report on recent progress in understanding the impact of QCD instantons on the electromagnetic structure of the nucleon in the framework of a generalized operator product expansion (GOPE). The latter contains the leading direct-instanton contributions to the nucleon correlator at short distances in a magnetic background field. We use the resulting expression for the correlator to set up improved QCD sum rules for the nucleon magnetic moments. Remarkably, the instanton contributions are found to affect exactly those sum rules which had previously been considered unstable. The new sum rules show excellent stability and reproduce the experimental values of the nucleon magnetic moments for values of χ, the quark condensate magnetic susceptibility, consistent with other estimates.