Abstract
Electromagneticp δ(1232) andp−S 11(1535) transition form factors in the momentum transfer range 3 ≲Q 2≲ 20 GeV2 are investigated within the scope of perturbative QCD. Thereby baryons are considered as built up by quarks and spatially extended diquarks. The diquark parameters and the quark-diquark distribution amplitude of the nucleon are adopted from a previous study which already led to a consistent description of electromagnetic nucleon form factors and Compton scattering off nucleons. Results are presented for several choices of the resonance distribution amplitudes and confronted with data. Most noteworthy, we find that the diquark model may account for the experimentally observed strong deviation ofp−δ electric and magnetic transition form factors from the asymptotic Q−4 behaviour.
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Sponsored in part by the Bundesministerium für Forschung und Technologie under contract number 06 Wü 765
We would like to thank Prof. P. Stoler for providing us with the numerical values of his resonance analysis results. One of us (W.S.) would like to thank the Theory Group at the University of Wuppertal for the kind hospitality extended to him.