Direct-Channel Resonance Model of Deep-Inelastic Electron Scattering. I. Scattering on Unpolarized Targets

We construct a resonance model of deep-inelastic electron scattering. Using semiempirical rules for the form of the nucleon spectrum and a universality hypothesis for the transition form factors, we obtain explicit expressions for the structure functions $W_1$ and $W_2$ in the Bjorken limit. The ratio of the longitudinal to transverse photoabsorption cross sections vanishes for large momentum transfers, and $\nu W_2$ becomes scale invariant. A one-parameter fit is obtained to $\nu W_2$ (proton), and a zero-parameter prediction is made of $\nu W_2$ (proton)-$\nu W_2$ (neutron). There is good agreement between the theory and experiment in the region where scale invariance is well established.