High-energy photoproduction and scattering of leptons in the field of extended nuclei - art. no. 064901

We consider the deviations from electromagnetic high-energy scattering and photoproduction of leptons in the field of pointlike nuclei, generated by a nuclear charge distribution. The concept of the eikonal form factor for th e description of scattering is briefly reviewed. In the region of small mom entum transfers a coherence phenomenon of multiphoton exchange is discussed . The strong dependence of the non-Coulomb corrections to the photoproducti on cross section of light lepton pairs upon the nuclear charge and the lept on mass can be traced back to this coherence effect. The higher-order corre ctions found for photoproduction are used to estimate the higher-order corr ections to lepton pair production in ultrarelativistic heavy-ion collisions in logarithmic accuracy.