Coherent particle production in relativistic heavy ion collisions

Coherent particle production via the γ-γ mechanism occurs in disruptive as well as non-disruptive relativistic heavy ion collisons. Due to the enhancement factor of Z4, relativistic heavy ion colliders may compete with e+e- colliders in the study of γ-γ physics. To reduce the strong background, non-disruptive collisions must be selected. In disruptive collisions, the dilepton production via coherent γ-γ processes is calculated, as a function of the impact parameter. Cross-sections are large, comparable to those expected from thermal and Drell-Yan mechanisms. However, the very low pperpendicularto-values will allow a discrimination. (orig.)