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Spin-dependent twist-4 matrix elements from the instanton vacuum: Flavor-singlet and nonsinglet

Nam-Young Lee·K. Goeke·C. Weiss
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Abstract

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-nonsinglet 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, (\bar ρ)/(\bar R) << 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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Nam-Young Lee, K. Goeke, C. Weiss. 2001-05-17. Spin-dependent twist-4 matrix elements from the instanton vacuum: Flavor-singlet and nonsinglet. https://doi.org/10.1103/physrevd.65.054008

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