Diffractive Lepton-Hadron Scattering

It is emphasized that the photon-dissociation mechanism, according to the present data in the large-$\omega$ region, may be the dominant mechanism at large $\omega$. The physical characteristics of the lepton-hadron scattering at large $\omega$ may therefore be quite different from those at small $\omega$. By identifying incoherence as the main physical reason for the scaling observed in the small-$\omega$ region, we conclude that there is no basis for expecting scaling in the large-$\omega$ region. Scaling may still hold there, but a breakdown of scaling should not be surprising. Speculations along this line are ventured.