Abstract
This work investigates the first correction to the equilibrium phase-space distribution and its effects on spectra and elliptic flow in heavy-ion collisions. We show that the departure from equilibrium on the freeze-out surface is the largest part of the viscous corrections to . However, the momentum dependence of the departure from equilibrium is not known a priori, and it is probably not proportional to as has been assumed in hydrodynamic simulations. At high momentum in weakly coupled plasmas, it is determined by the rate of radiative energy loss and is proportional to . The weaker dependence leads to straighter curves at the same value of viscosity. Furthermore, the departure from equilibrium is generally species dependent. A species-dependent equilibration rate, with baryons equilibrating faster than mesons, can explain “constituent quark scaling” without invoking coalescence models.
4 More- Received 16 October 2009
DOI:https://doi.org/10.1103/PhysRevC.81.034907
©2010 American Physical Society