Applications of the Equivalent Photon Approximation to Heavy Ion Collisions

Two of the main research tools in High Energy Physics- electron and proton colliders are often described as having complementary roles. But their roles have changed in the last 30 years. For example the term "electron collider physics" connotes a broader topic today than the original purpose- to study the electromagnetic structure of the proton. The Relativistic Heavy Ion Collider (RHIC) which started operation a year ago will be joined by the Large Hadron Collider (LHC) in 2007 with a 30-fold increase in center-of-mass energy. In many respects these instruments are complementary. The heavy ion community anticipates a full program for both machines which focuses on the study hot hadronic matter and search for the quark-gluon plasma. Nevertheless, it is likely that the term "Heavy Ion Collider Physics" will come to include other areas of research as techniques with the colliders evolve- particularly in those areas where the energy increase from RHIC to the LHC are most important.