PHOTON-HADRON INTERACTIONS IN RELATIVISTIC HEAVY-ION COLLISIONS

High-energy photon-hadron interactions in relativistic heavy ion collisions are studied in the impulse approximation. This leads to an explicit treatment of the spatial distribution of the constituents in the volume of the nucleus struck by the equivalent photon. Relevant changes in the high-energy tail of the equivalent photon spectrum compared to the conventional method are obtained. Total fragmentation cross sections due to photon-hadron interactions which contribute to the luminosity decrease at colliders like the Brookhaven Relativistic Heavy Ion Collider or the CERN Large Hadron Collider (heavy ions) are also studied. As an important application we study the gammag fusion into quark-antiquark pairs. This gives a handle to determine the gluon distribution function of nucleons inside the nucleus.