Photons from the Early Stages of Relativistic Heavy Ion Collisions

Abstract

We present results about photons production in relativistic heavy ion collisions. The main novelty of our study is the calculation of the contribution of the early stage photons to the photon spectrum. The initial stage is modeled by an ensemble of classical gluon fields which decay to a quark-gluon plasma via the Schwinger mechanism, and the evolution of the system is studied by coupling classical field equations to relativistic kinetic theory; photons production is then computed by including the pertinent collision processes into the collision integral. We find that the contribution of the early stage photons to the direct photon spectrum is substantial for $p_T\approx 2$ GeV and higher, the exact value depending on the collision energy; therefore we identify this part of the photon spectrum as the sign of the early stage. Moreover, the amount of photons produced during the early stage is not negligible with respect to those produced by a thermalized quark-gluon plasma: we support the idea that there is no dark age in relativistic heavy ion collisions.

11 pages, 9 figures. Matches published version

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Cited by in corpus (14)

• QCD thermalization: Ab initio approaches and interdisciplinary connections
• Multi-messenger heavy-ion collision physics
• Direct real photons in relativistic heavy ion collisions
• The Present and Future of QCD
• Relativistic Fluid Dynamics In and Out of Equilibrium -- Ten Years of Progress in Theory and Numerical Simulations of Nuclear Collisions
• The emission of electromagnetic radiation from the early stages of relativistic heavy-ion collisions
• Photon production and elliptic flow from momentum-anisotropic quark-gluon plasma
• Ballistic diffusion of heavy quarks in the early stage of relativistic heavy ion collisions at RHIC and LHC
• Prompt, pre-equilibrium, and thermal photons in relativistic nuclear collisions
• Probing the evolution of heavy-ion collisions using direct photon interferometry
• Probing the spacetime evolution of heavy ion collisions with photons and dileptons
• Photon production from Pb+Pb collisions at {$\sqrt{s_{\mathrm{NN}}}$} = 5.02 TeV at LHC and at {$\sqrt{s_{\mathrm{NN}}}$} = 39 TeV at FCC
• Direct Photons in Hydrodynamic Modeling of Relativistic Nuclear Collisions
• Thermal dilepton production within conformal viscous Gubser flow