Chemical equilibration in a viscous quark-gluon plasma and electromagneticsignals

We have investigated the chemical equilibration of the parton distributions in collisions of two heavy nuclei assuming the partonic fluid to be ideal as well as viscous. The initial conditions are taken from HIJING calculatio ns for Au + Au collisions at RHIC and LHC energies. It is seen that when th e viscous drag is taken into account, the lifetime of the the plasma is inc reased by a factor of nearly two. The temperature as well as fugacities evo lve more slowly than their ideal counterpart. Photon and lepton pair produc tion are also investigated. With viscosity, there is a twofold increase in the photon and lepton pair production. The increase in the large p(T) photo ns or large invariant mass lepton pairs is due to the slower rate of temper ature evolution.