Thermal photons in QGP and non-ideal effects

Abstract

We investigate the thermal photon production-rates using one dimensional boost-invariant second order relativistic hydrodynamics to find proper time evolution of the energy density and the temperature. The effect of bulk-viscosity and non-ideal equation of state are taken into account in a manner consistent with recent lattice QCD estimates. It is shown that the \textit{non-ideal} gas equation of state i.e $\epsilon -3P\ne 0$ behaviour of the expanding plasma, which is important near the phase-transition point, can significantly slow down the hydrodynamic expansion and thereby increase the photon production-rates. Inclusion of the bulk viscosity may also have similar effect on the hydrodynamic evolution. However the effect of bulk viscosity is shown to be significantly lower than the \textit{non-ideal} gas equation of state. We also analyze the interesting phenomenon of bulk viscosity induced cavitation making the hydrodynamical description invalid. We include the viscous corrections to the distribution functions while calculating the photon spectra. It is shown that ignoring the cavitation phenomenon can lead to erroneous estimation of the photon flux.

11 pages, 13 figures; accepted for publication in JHEP

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• Onset of cavitation in the quark-gluon plasma
• Bulk viscosity for pion and nucleon thermal fluctuation in the hadron resonance gas model
• Second order hydrodynamics based on effective kinetic theory and electromagnetic signals from QGP
• Hydrodynamical attractor and thermal particle production in heavy-ion collision
• Thermal dilepton production within conformal viscous Gubser flow
• Cosmological QCD phase transition in steady non-equilibrium dissipative Hořava-Lifshitz early universe
• Formulation of relativistic dissipative fluid dynamics and its applications in heavy-ion collisions
• Finite-Density Dynamics of Chemically Equilibrating QGP in Conformal Gubser Flow and Hard Thermal Photon Production