Nonperturbativeγ*pinteraction in the diffractive regime

Abstract

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 ${Q}^{2}l~10$ GeV${}^{2}$. Indications for a chiral transition may already have been seen in the photon-proton cross section.