Emission of electromagnetic radiation from the early stages of relativistic heavy-ion collisions

Abstract

We estimate the production of electromagnetic radiation (real and virtual photons) from the early, pre-equilibrium stage of relativistic heavy-ion collisions. The parton dynamics are obtained as a solution of the Boltzmann equation in the Fokker-Planck diffusion limit. The photon and dilepton rates are integrated and the obtained yields are compared with those from standard sources and with available experimental data. The nonequilibrium electromagnetic contribution can be nonnegligible at the current LHC energies, depending on the saturation scale. Predictions are made for $\mathrm{Pb}+\mathrm{Pb}$ at $\sqrt{{s}_{\mathrm{NN}}}=5.02\phantom{\rule{0.16em}{0ex}}\mathrm{TeV}$.

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