Abstract
A calculation of sources of inclusive photons in ultrarelativistic O-W and Pb-Pb collisions at 200 GeV/u is presented. The production of thermal photons in a quark-gluon plasma, a deconfined state of nuclear matter at high energy density, is addressed. In events with a large amount of energy deposited in the target the thermal contribution to the inclusive spectrum is found to be ∼5%, quadratically increasing with particle multiplicity, but only weakly dependent on the size of the projectile nucleus. These photons are predominantly produced in a coexistence phase of plasma and hadronic matter. Hadronic bremsstrahlung is investigated including the spatial and temporal coherence due to the large space-time extension of heavy-ion systems. For small photon momenta there is a coherent signal in the fragmentation regions proportional to the squared number of participant protons.
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Neubert, M. Photon production in ultrarelativistic heavy-ion collisions at 200 GeV/u. Z. Phys. C - Particles and Fields 42, 231–242 (1989). https://doi.org/10.1007/BF01555862
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DOI: https://doi.org/10.1007/BF01555862