Nuclear distintegration induced by virtual photons at heavy-ion colliders

Abstract

Photonuclear reaction data obtained in experiments with real monoenergetic photons and appropriate theoretical models describing photonuclear reactions may be used to predict the properties of electromagnetic dissociation process. A variety of fragmentation mechanisms takes place in the electromagnetic dissociation of ultrarelativistic heavy ions, namely the coalescence, Fermi break-up, evaporation, fission and multifragmentation. A partial or complete disintegration of the colliding nuclei is possible despite the absence of geometrical overlap of the nuclear densities. This chapter provides an introduction to a model of electromagnetic interaction of relativistic heavy ions, which makes it possible to calculate the inclusive and exclusive characteristics of such interactions. The multistep model includes the single and double virtual photon absorption by a nucleus, intranuclear cascades of produced hadrons, and statistical decay of excited residual nuclei described by evaporation, fission and multifragmentation mechanisms. Components of the model are verified by comparison of calculation results with experimental data obtained with monoenergetic photons and heavy ions at KEK-Tanashi Synchrotron and CERN SPS accelerator, respectively.