J. Scott Moreland

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 ultrarelativistic heavy-ion collisions utilizing Bayesian statistics and a multiparameter 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.

Constraints on rapidity-dependent initial conditions from charged particle pseudorapidity densities and two-particle correlations

We study the initial three-dimensional spatial configuration of the quark-gluon plasma produced in relativistic heavy-ion collisions using centrality and rapidity-dependent measurements of charged particle pseudorapidity densities and two-particle correlations. A cumulant-generating function is used to parametrize the rapidity dependence of local entropy deposition and extend arbitrary boost-invariant initial conditions to nonzero beam rapidities. The model is compared to p+Pb and Pb+Pb single-particle distributions and systematically optimized using Bayesian parameter estimation to extract high-probability initial condition parameters. The optimized initial conditions are then compared to a number of experimental observables including two-particle rapidity correlations, the rapidity dependence of anisotropic flow, and event-plane decorrelations.

Determination of Quark-Gluon-Plasma Parameters from a Global Bayesian Analysis

Abstract The quality of data taken at RHIC and LHC as well as the success and sophistication of computational models for the description of ultra-relativistic heavy-ion collisions have advanced to a level that allows for the quantitative extraction of the transport properties of the Quark-Gluon-Plasma. However, the complexity of this task as well as the computational effort associated with it can only be overcome by developing novel methodologies: in this paper we outline such an analysis based on Bayesian Statistics and systematically compare an event-by-event heavy-ion collision model to data from the Large Hadron Collider. We simultaneously probe multiple model parameters including fundamental quark-gluon plasma properties such as the temperature-dependence of the specific shear viscosity η / s , calibrate the model to optimally reproduce experimental data, and extract quantitative constraints for all parameters simultaneously. The method is universal and easily extensible to other data and collision models.

Hydrodynamic simulations of relativistic heavy-ion collisions with different lattice quantum chromodynamics calculations of the equation of state

Hydrodynamic calculations of ultra-relativistic heavy ion collisions are performed using the iEBE-VISHNU 2+1D code with fluctuating initial conditions and three different parameterizations of the Lattice QCD equations of state: continuum extrapolations for stout and HISQ/tree actions, as well as the s95p-v1 parameterization based upon calculations using the p4 action. All parameterizations are matched to a hadron resonance gas equation of state at T = 155 MeV, at which point the calculations are continued using the UrQMD hadronic cascade. Calculations for

Flow in small and large quark-gluon plasma droplets: the role of nucleon substructure

\sqrt{s_{NN}}=200

Alternative ansatz to wounded nucleon and binary collision scaling in high-energy nuclear collisions

GeV Au+Au collisions in three centrality classes are compared to experimental data for final state particle spectra and anisotropic flow coefficients

Characterization of the initial state and QGP medium from a combined Bayesian analysis of LHC data at 2.76 and 5.02 TeV

v_2

Estimating nucleon substructure properties in a unified model of p-Pb and Pb-Pb collisions

and

Estimating initial state and quark-gluon plasma medium properties using a hybrid model with nucleon substructure calibrated to

v_3

p

as well as for pion HBT radii. Experimental observables for the stout and HISQ/tree equations of state are observed to differ by less than a few percent for all observables, while the s95p-v1 equation of state generates spectra and flow coefficients which differ by ~10-20%. Calculations in which the HISQ/tree equation of state is sampled from the published error distribution are also observed to differ by less than a few percent.