γγ physics at relativistic heavy-ion colliders

Relativistic heavy-ion colliders like the Brookhaven Relativistic Heavy Ion Collider or CERN Large Hadron Collider open up the possibilities for {γ}{γ} physics. This provides tests of the standard model, possible extensions and especially QCD in the resonance and the continuum regime. The model independent quantity to study these processes is the {γ}{γ} luminosity function due to the experimentally limited detector acceptance. Due to irreducible {γ}-hadron interactions, there are serious background problems at such colliders. We discuss this background due to {γ}A and especially {γ}g reactions.