1,558 research outputs found
Direct Instantons and Nucleon Magnetic Moments
We calculate the leading direct-instanton contributions to the operator
product expansion of the nucleon correlator in a magnetic background field and
set up improved QCD sum rules for the nucleon magnetic moments. Remarkably, the
instanton contributions are found to affect only those sum rules which had
previously been considered unstable. The new sum rules show good stability and
reproduce the experimental values of the nucleon magnetic moments with values
of , the quark condensate magnetic susceptibility, consistent with other
estimates.Comment: 15 pages, 2 figure
Instantons and Nucleon Magnetism
We construct improved QCD sum rules for the nucleon magnetic moments by
implementing direct-instanton contributions to the operator product expansion
of the nucleon correlator in a magnetic background field. The instanton
contributions are found to affect only those sum rules which had previously
been considered unstable. The new sum rules show a high degree of stability and
reproduce the experimental values of the nucleon magnetic moments for values of
the magnetic quark condensate susceptibility which are consistent with other
estimates.Comment: 10 pages, 2 figures. Invited talk given at "Hadron Physics 2000",
Caraguatatuba, Sao Paulo, Brazil (April 10-15, 2000
QCD Vacuum Topology and Glueballs
We outline a comprehensive study of spin-0 glueball properties which, in
particular, keeps track of the topological gluon structure. Specifically, we
implement (semi-hard) topological instanton physics as well as topological
charge screening in the QCD vacuum into the operator product expansion (OPE) of
the glueball correlators. A realistic instanton size distribution and the
(gauge-invariant) renormalization of the instanton contributions are also
implemented. Predictions for 0^{++} and 0^{-+} glueball properties are
presented.Comment: 3 pages, no figure
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