Coulomb effects on electromagnetic pair production in ultrarelativistic heavy-ion collisions

We calculate the asymptotic high-energy amplitude for electrons scattering at one ion, as well as at two colliding ions, by means of perturbation theo ry. We show that the interaction with one ion eikonalizes and that the inte raction with two ions causally decouples. We are able to put previous resul ts on perturbative grounds and propose further applications for the obtaine d rules for interactions on the light cone. We discuss the implications of the eikonal amplitude on the pair production probability in ultrarelativist ic peripheral heavy-ion collisions. In this context the Weizsacker-Williams method is shown to be exact in the ultrarelativistic limit, irrespective o f the produced particles' mass. A new equivalent single-photon distribution is derived, which correctly accounts for Coulomb distortions. The impact o n single-photon induced processes is discussed. [S1050-2947(99)00602-2].