Photon Emission In Heavy Ion Collisions Research Articles

Calculations of direct photon emission in heavy ion collisions at = 200 GeV

Direct photon emission in heavy-ion collisions is calculated within a relativistic micro+macro hybrid model and compared to the microscopic transport model UrQMD. In the hybrid approach, the high-density part of the collision is calculated by an ideal 3+1-dimensional hydrodynamic calculation, while the early (pre-equilibrium-) and late (rescattering-) phase are calculated with the transport model. We study both models with Au + Au-collisions at = 200 GeV and compare the results to experimental data published by the PHENIX collaboration.

Hybrid model calculations of direct photons in high-energy nuclear collisions

Direct photon emission in heavy-ion collisions is calculated within a relativistic micro $+$ macro hybrid model and compared to the microscopic transport model, the Ultra-relativistic Quantum Molecular Dynamics model. In the hybrid approach, the high-density part of the evolution is replaced by an ideal three-dimensional hydrodynamic calculation. This allows the effects of viscosity and full local thermalization, in comparison with the transport model of the ideal fluid dynamics, to be examined. The origin of high-${p}_{\ensuremath{\perp}}$ photons as well as the impact of elementary high-$\sqrt{s}$ collisions is studied. The contribution of different production channels and nonthermal radiation to the spectrum of direct photons is further explored. Detailed comparisons to the measurements by the WA98 Collaboration are also undertaken.

Direct photon emission from hadronic sources: hydrodynamics vs. transport theory

Direct photon emission in heavy-ion collisions is calculated within the relativistic microscopic transport model UrQMD. We compare the results from the pure transport calculation to a hybrid-model calculation, where the high-density part of the evolution is replaced by an ideal 3-dimensional fluid-dynamic calculation. The effects of viscosity, present in the transport model but neglected in ideal fluid dynamics, are examined. We study the contribution of different production channels and non-thermal collisions to the spectrum of direct photons. Detailed comparisons to the measurements by the WA 98 collaboration are undertaken.