Applying Bayesian parameter estimation to relativistic heavy-ion   collisions: simultaneous characterization of the initial state and   quark-gluon plasma medium
  We quantitatively estimate properties of the quark-gluon plasma created in ultra-relativistic heavy-ion collisions utilizing Bayesian statistics and a multi-parameter model-to-data comparison. The study is performed using a recently developed parametric initial condition model, TRENTO, which interpolates among a general class of particle production schemes, and a modern hybrid model which couples viscous hydrodynamics to a hadronic cascade. We calibrate the model to multiplicity, transverse momentum, and flow data and report constraints on the parametrized initial conditions and the temperature-dependent transport coefficients of the quark-gluon plasma. We show that initial entropy deposition is consistent with a saturation-based picture, extract a relation between the minimum value and slope of the temperature-dependent specific shear viscosity, and find a clear signal for a nonzero bulk viscosity. 
Jonah E. Bernhard, J. Scott Moreland, Steffen A. Bass, Jia Liu, Ulrich   Heinz
nucl-th hep-ph nucl-ex