Mapping the hydrodynamic response to the initial geometry in heavy-ion collisions

We investigate how the initial geometry of a heavy-ion collision is transformed into final flow observables by solving event-by-event ideal hydrodynamics with realistic fluctuating initial conditions. We study quantitatively to what extent anisotropic flow (nu(n)) is determined by the initial eccentricity epsilon(n) for a set of realistic simulations, and we discuss which definition of epsilon(n) gives the best estimator of nu(n). We find that the common practice of using an r(2) weight in the definition of epsilon(n) in general results in a poorer predictor of nu(n) than when using r(n) weight, for n > 2. We similarly study the importance of additional properties of the initial state. For example, we show that in order to correctly predict nu(4) and nu(5) for noncentral collisions, one must take into account nonlinear terms proportional to epsilon(2)(2) and epsilon(2)epsilon(3), respectively. We find that it makes no difference whether one calculates the eccentricities over a range of rapidity or in a single slice at z = 0, nor is it important whether one uses an energy or entropy density weight. This knowledge will be important for making a more direct link between experimental observables and hydrodynamic initial conditions, the latter being poorly constrained at present.Agence Nationale de la RechercheAgence Nationale de la Recherche [ANR-08-BLAN-0093-01]Cofecub [Uc Ph 113/08Cofecub [Uc Ph 113/082007.1.875.43.9]2007.1.875.43.9]FAPESP [09/50180-0, 09/16860-3]FAPESPCNPqCNPq [301141/2010-0]European Research CouncilEuropean Research Council [ERC-AD-267258

Particle abundances and spectra in the hydrodynamical description of relativistic nuclear collisions with light projectile

We show that a hydrodynamical model with continuous particle emission instead of sudden freeze out may explain both the observed strange particle and pion abundances and transverse mass spectra for light projectile at SPS energy. We found that the observed enhancement of pion production corresponds, within the context of continuous emission, to the maximal entropy production

A closer look at the influence of tubular initial conditions on two-particle correlations

In a recent paper, the hydrodynamic code NEXSPheRIO was used in conjunction with STAR analysis methods to study two-particle correlations as a function of Delta(eta) and Delta phi. The various structures observed in the data were reproduced. In this work, we discuss the origin of these structures as well as present new results

Comparison between classification using impact parameter and using number of participants in relativistic nuclear collisions

Using the hydrodynamical code NeXSPheRIO, we compare predictions as usually done in hydrodynamics, using centrality windows defined through the impact parameter, and as obtainable experimentally, using windows in participant number

Guidelines for sound design in computer games

The inconsequential exploitation of sound in most computer games, both in extent and nature, contrasts with its prominence in our daily lives and with the kind of associations that have been explored in domains such as music and cinema. Sound design remains the craft of a talented minority and the unavailability of a public body of knowledge on the subject has greatly contributed to this state of affairs. This leads to a mix of alienation and best-judgment improvisation in the broader development community. A sensitivity to the potential of sound for the enrichment of the experience—with emphasis on game specifics—is, therefore, necessary. This study presents a contribution to the practice of sound design for computer games. An approach to intentional sound design, informed by multi-disciplinary interpretations of concepts including emotion, context, acoustic ecology, soundscape, resonance, and entrainment, is distilled into a set of design guidelines that holistically address the different sound layers

FLUCTUATIONS AND INITIAL STATE GRANULARITY IN HEAVY ION COLLISIONS AND THEIR EFFECTS ON OBSERVABLES FROM HYDRODYNAMICS

A comparison is made between results obtained using smooth initial conditions and event-by-event initial conditions in the hydrodynamical description of relativistic nuclear collisions. Some new results on directed flow are also included