Coherent photon bremsstrahlung and dynamics of heavy-ion collisions: Comparison of different models - art. no. 044902

Differential spectra of coherent photon bremsstrahlung in relativistic heav y-ion collisions are calculated within various schematic models of the proj ectile-target stopping. Two versions of the degradation length model, based on a phenomenological deceleration law, are considered. The simple shock w ave model is studied analytically. The predictions of these models agree in the soft photon limit, where the spectrum is determined only by the final velocity distribution of charged particles. The results of these models in the case of central Au+Au collisions at the AGS bombarding energy are compa red with the predictions of the microscopic transport model UrQMD. The latt er model is also used to calculate photon spectra at SIS, SPS, and RHIC ene rgies. It is shown that at the AGS energy the coherent photon bremsstrahlun g exceeds the photon yield from pi(0) decays at c.m. photon energies omega less than or similar to 50 MeV.