Thermal radiation from an expanding viscous medium

The effects of viscosity on the space time evolution of QGP produced in nuclear collisions at RHIC energies have been studied. The entropy generated due to the viscous motion of the fluid has been taken into account in constraining the initial temperature by the final multiplicity (measured at the freeze-out point). The viscous effects on the photon spectra has been introduced consistently through the evolution dynamics and phase space factors of the particles participating in the production process. We notice a stronger effect on the photon spectra originating from QGP than hadronic matter. A detectable shift is observed in the space-time integrated p_T distribution of photons due to dissipative effects.

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