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 y*p→γp, the real photon-proton total cross section σγptot(s), the real photon-photon total cross section σγγ tot(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. © 2001 The American Physical Society.