Total γ* p cross section

This paper shows that the approach based on Gribov's ideas for photon-proton interaction is able to describe the experimental data over a wide range of photon virtualities Q² = 0-100 GeV² and energies √s = W = 3-300 GeV. A simple model is suggested which provides a quantitative way of describing the matching between short and long distances (between "soft" and "hard" processes) in photon-proton interaction at high energy. The main results of our analysis are: (i) the values of the separation parameters differentiating the soft and hard interactions are determined; (ii) the additive quark model can be used to calculate the soft contribution to the photon-proton interaction; (iii) a good description of the ratio σ_L/σ_T is obtained; and (iv) a onsiderable contribution of the soft process at large Q², and of hard processes at small Q² was found.