Zusammenfassung
We estimate the twist-4 spin-1 nucleon matrix element f(2) in an instanton-based description of the QCD vacuum. In addition to the flavor-non singlet we compute also the flavor-singlet matrix element, which appears in next-to-leading order of the 1/N-c-expansion. The corresponding twist-3 spin-2 matrix elements d(2) are suppressed in the packing fraction of the instanton medium, (rho) over ...
Zusammenfassung
We estimate the twist-4 spin-1 nucleon matrix element f(2) in an instanton-based description of the QCD vacuum. In addition to the flavor-non singlet we compute also the flavor-singlet matrix element, which appears in next-to-leading order of the 1/N-c-expansion. The corresponding twist-3 spin-2 matrix elements d(2) are suppressed in the packing fraction of the instanton medium, (rho) over bar/(R) over bar << 1. We use our results to estimate the leading 1/Q(2) power corrections to the first moment of the proton and neutron spin structure functions G(1), as well as the intrinsic charm contribution to the nucleon spin.
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