Parton distribution within a virtual photon and diffractive photoproduction in deep-inelastic scattering

A simple relativistic model that elucidates qualitatively the quark-antiquark distribution within a virtual photon is proposed. Diffractive hadroproduction in deep-inelastic scattering (DIS) initiated by a highly virtual photon γ*(Q2) is discussed in more detail. The main result is that the contribution of large-transverse-scale qq-bar fluctuations of the photon is sufficient to produce the cross section for its hadron-like strong interaction (in particular, its diffraction into hadrons) of the same Q2 dependence as the total cross section for γ*p interaction. This is the reason why, in DIS, the observed fraction of photon diffraction hadroproduction in γ*p interaction is quite large and does not vary with Q2