Comprehensive approach to structure functions

We present a model based on a dipole picture with a hard and a soft Pomeron in which large dipoles couple to the soft Pomeron and small dipoles couple to the hard Pomeron. The parameters in the model are fixed by proton-proton scattering and the proton structure function F₂(x,Q²). The model is then applied successfully to the proton charm structure function F₂ᶜ(x,Q²), the proton longitudinal structure function F₂L(x,Q²), J/ψ photoproduction, deep virtual Compton scattering γ*p→γp, the real photon-proton total cross section σ_γpᵗᵒᵗ(s), the real photon-photon total cross section σ_γγᵗᵒᵗ(s), and the photon structure function F₂^γ(x,Q²). Differences between our predictions and data on charm production in real photon-photon interactions and the γ*γ* cross section σ_γγᵗᵒᵗ(s) are discussed.