Twist-4 contribution to unpolarized structure functions F and F from instantons

1999/06/23 by B. Dressler, M. Maul, C. Weiss
Physics and Astronomy · #Black Holes and Theoretical Physics #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions #hep-ph

paper · pdf · doi:10.1016/s0550-3213(00)00024-9

published as Nucl.Phys. B578 (2000) 293-325 · 38 pages, LaTeX. 4 figures included using epsf

arxiv created 1999/06/23 · openalex publication_date 2000/07/01 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28

Abstract

We compute in the instanton vacuum the nucleon matrix elements of the twist-4 QCD operators describing power corrections to the second moments of the unpolarized structure functions, F_L and F₂. Our approach takes into account the leading contribution in the packing fraction of the instanton medium, rho / R << 1. Parametrically leading are the matrix elements of a twist-4 quark-gluon operator, which are of the order of the inverse instanton size, 1/rho² = (600 MeV)². The matrix elements of the four-fermion (diquark) operators are suppressed by a factor (rho / R)⁴ and numerically small. These results are in agreement with the pattern of phenomenological 1/Q²-corrections to R = sigma_L / sigma_T and F₂ found in QCD fits to the data. In particular, the rise of R at low Q² can be obtained from instanton-type vacuum fluctuations at a low scale.

Citations

• Power corrections in the longitudinal and transverse structure functions of proton and deuteron
• Lattice calculation of point-to-point Hadron current correlation functions in the QCD vacuum
• Renormalon model predictions for power corrections to flavor-singlet deep-inelastic structure functions
• Nucleon parton distributions at low normalization point in the large Nc limit
• Instantons in QCD