Resonance–parton duality in off nucleons

Regge-pole-based descriptions of pion-electroproduction on nucleons have given a very good description of the longitudinal components of the cross sections. However, these very same models grossly underestimate the transverse components. A related problem appears in QCD-based scaling arguments that predict the predominance of longitudinal over transverse electroproduction of pions by terms ∝ Q 2 . However, data from JLAB, Cornell, and DESY, covering a wide kinematical range 1 < Q 2 < 11 GeV 2 and 2 GeV < W < 4 GeV , do not show this expected behavior. We address here this issue of the transverse response in pion-electroproduction by considering the contributions of high-lying ( W > 2 GeV ) nucleon resonances to pion production. The coupling strengths and form factors are obtained through resonance–parton duality. We show that in a wide range of electron energies and four-momentum transfers such a model describes all the available data very well.