Shear viscosity and chemical equilibration of the QGP

Abstract

We have investigated, in the frame work of the transport approach, different aspects of the QGP created in Heavy Ion Collisions at RHIC and LHC energies. The shear viscosity $\eta$ has been calculated by using the Green-Kubo relation at the cascade level. We have compared the numerical results for $\eta$ obtained from the Green-Kubo correlator with the analytical formula in both the Relaxation Time Approximation (RTA) and the Chapman-Enskog approximation (CE). From this comparison we show that in the range of temperature explored in a Heavy Ion collision the RTA underestimates the viscosity by about a factor of 2, while a good agreement is found between the CE approximation and Gree-Kubo relation already at first order of approximation. The agreement with the CE approximation supplies an analytical formula that allows to develop kinetic transport theory at fixed shear viscosity to entropy density ratio, $\eta /s$. We show some results for the build up of anisotropic flows $v_2$ in a transport approach at fixed shear viscosity to entropy density ratio, $\eta /s$. We study the impact of a T-dependent $\eta /s(T)$ on the generation of the elliptic flows at both RHIC and LHC. We show that the transport approach provides, in a unified way, a tool able to naturally describe the $v_2(p_T)$ in a wide range of $p_T$, including also the description of the rise and fall and saturation of the $v_2(p_T)$ observed at LHC. Finally, we have studied the evolution of the quark-gluon composition employing a Boltzmann-Vlasov transport approach that include: the mean fields dynamics, associated to the quasi-particle model, and the elastic and inelastic collisions for massive quarks and gluons. Following the chemical evolution from an initial gluon dominated plasma we predict a quark dominance close to $T_C$ paving the way to an hadronization via quark coalescence.

15 pages, 10 figures, Invited Talk given by S. Plumari at the 11th International Conference on Nucleus-Nucleus Collisions (NN2012), San Antonio, Texas, USA, May 27-June 1, 2012. To appear in the NN2012 Proceedings in Journal of Physics: Conference Series (JPCS)

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• Photons from the Early Stages of Relativistic Heavy Ion Collisions
• Modelling Early Stages of Relativistic Heavy Ion Collisions: Coupling Relativistic Transport Theory to Decaying Color-electric Flux Tubes
• Relativistic Boltzmann transport approach with Bose-Einstein statistics and the onset of gluon condensation
• Directed flow of D mesons at RHIC and LHC: non-perturbative dynamics, longitudinal bulk matter asymmetry and electromagnetic fields
• Viscous corrections to anisotropic flow and transverse momentum spectra from transport theory
• Quarks Production in the Quark-Gluon Plasma Created in Relativistic Heavy Ion Collisions
• On the contribution of plasminos to the shear viscosity of a hot and dense Yukawa-Fermi gas
• Transport properties from Charm to Bottom: $p_T$ suppression, anisotropic flow $v_n$ and their correlations to the bulk dynamics
• The Rayleigh Bubble in Quark Matter under a Strong Magnetic Field
• Elliptic Flow and Shear Viscosity of the Shattered Color Glass Condensate
• Event shape Engineering analysis of D meson in ultrarelativistic heavy ion collisions