# Quark Matter 2012

12-18 August 2012
US/Eastern timezone

## Initial conditions for fluid dynamics from a parton cascade model

16 Aug 2012, 16:00
2h
Regency 1/3 and Ambassador ()

### Regency 1/3 and Ambassador

Poster Global and collective dynamics

### Speaker

Ioannis Bouras (University of Frankfurt a.M.)

### Description

The initial conditions play a fundamental role in the fluid-dynamical modeling of the quark-gluon plasma (QGP) created in ultrarelativistic heavy-ion collisions. Many observables that are important in determining the properties of the QGP, such as elliptic flow (v2) and triangular flow (v3), appear to be generated mainly from the initial geometry of the energy density profile. Since the initial conditions remain undetermined, it introduces a large uncertainty in the extraction of the properties of the QGP. Typically it is assumed that the matter thermalizes and fluid dynamics can be applied after time of the order of $1$ fm/c after the initial nuclear collision. However, the matter itself can be created much earlier, and it undergoes pre-equilibrium evolution before fluid dynamics can be applied. In this work, we estimate the impact of the pre-equilibrium evolution of the QGP on the initial conditions for fluid dynamics using a parton cascade model. For the initial conditions for the pre-equilibrium evolution we use a realistic 6--dimensional parametrization of the initial single-particle distribution function $f(x, p)$ that reflect, e.g. the observed rapidity and multiplicity distributions at RHIC and LHC. Then, we solve the time evolution of this distribution using the relativistic Boltzmann equation, up to times of the order of 1 fm/c, for various values of partonic cross sections. The relativistic Boltzmann equation is solved using the BAMPS algorithm Ref. [1]. The main advantage of our approach is that we are able to compute, not only the energy density distribution at $t=1$ fm, but also the velocity and shear-stress tensor profiles, which, so far, are mostly unknown. [1] Z. Xu and C. Greiner, Phys. Rev. C 71 (2005) 064901; Phys. Rev. C 76, 024911 (2007).

### Primary author

Ioannis Bouras (University of Frankfurt a.M.)

### Co-authors

Andrej El (University of Frankfurt) Carsten Greiner (University of Frankfurt) Dirk Rischke (U) Gabriel Denicol (Frankfurt University) Harri Niemi (Frankfurt Institute for Advanced Studies)

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