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HK: Hadronen und Kerne

HK 68: Structure of Baryons, Mesons X, Theory

HK 68.2: Group Report

Thursday, March 19, 1998, 14:30–15:00, J

Quark Wavefunctions for the Nucleon — •R. Eckardt, J. Hansper, and M.F. Gari — Arbeitsgruppe Mittelenergiephysik, Inst. f"ur Theoretische Physik, Ruhr-Universit"at Bochum, D-44780 Bochum

After investigating the methods for constructing quark distribution amplitudes (QDAs) from QCD sum-rule moments, it was found that the determination of expansion coefficients of a polynomial expansion from sum rule moments is practically impossible. The freedom from the errors of the QCD sum-rule moments leads to a complete indeterminacy of the QDA with higher order coefficients becoming more and more sensitive to small errors so that the expansion does not converge [1].

We construct quark distribution amplitudes with a minimal number of parameters avoiding unphysical oscillations, thus leading to simpler and reliable models. The importance of higher twist effects is investigated. Results for form factors with effectively included higher twist effects are presented.

[1] R. Eckardt, J. Hansper, M.F. Gari, Phys.Rev. D50(1994)R26; R. Eckardt, J. Hansper, M.F. Gari, Phys.Lett. B329(1994)345; R. Eckardt, J. Hansper, M.F. Gari, Phys.Rev. D51(1995)3593.