Nonperturbative γ^* p Interaction in the Diffractive Regime

One of the challenging aspects of electroproduction at high-energy is the understanding of the transition from real photons to virtual photons in the GeV^2 region. We study inclusive electroproduction on the proton at small x_B using a nonperturbative dipole-proton cross section calculated from the gauge invariant gluon field correlators as input. By quark-hadron duality, we construct a photon light cone wave function which links the ``hadronic'' behavior at small Q^2 to the ``perturbative'' behavior at large Q^2. It contains quark masses which implement the transition from constituent quarks at low Q^2 to current quarks at high Q^2. Our calculation gives a good description of the structure function at fixed energy for Q^2<=10 GeV^2. Indications for a chiral transition may already have been seen in the photon-proton cross section.