# (2+1)-dimensional viscous fluid dynamics (VISH2+1 with EOSL-PCE, Shen, Huovinen et al.)

**Essential profiles for jet quenching in viscous hydro**

To unzip the tarball type "tar -jxvf forjetprofile.tar.bz2".

The attached results were computed with VISH2+1 (arXiv:0709.0742, arXiv:0712.3715, and arXiv:0805.1756), a viscous hydro code in (2+1) dimensions assuming longitudinal boost invariance.

The simulations use the equation of state s95p-PCE developed by Pasi Huovinen and Peter Petreczky that matches lattice QCD data above T_C to a chemically frozen-out hadron resonance gas below T_C. A detailed description of EOS s95p-PCE is given in arXiv:1010.1856.

Unpacking of the tarball generates a directory "forjetprofile" with files that are named by the initial condition model and the impact parameter. "CGC" stands for Color Glass Condensate initial conditions from the fKLN model and "Glb" stands for Glauber initial conditions.

Each file includes the local flow vector (Vx,Vy), the energy density epsilon, and the temperature T
inside the 4-volume enclosed by the freeze-out surface.

Each file has 7 columns which are ordered as follows:

tau(longitudinal proper time in fm/c), x(fm), y(fm), Vx, Vy, epsilon (energy density in fm^(-4)), T (temperature in fm^(-1))

One can multiply epsilon and T by \hbar*c = 0.19733 GeV*fm to get energy density in GeV/fm^3 and temperature in GeV.

Initial conditions for the hydro evolution are adjusted to roughly reproduce experimental
pion and proton spectra from the 5% most central 200 A GeV Au+Au collisions, using EOS s95p-PCE:

s_0 = 86.667 fm^-3 [peak entropy density at \tau_0 for b = 2.33 fm (5% most central collisions)]

\tau_0 = 0.4 fm/c

T_dec = 130 MeV

\eta/s = 0.2

**Important note:** These parameters do **not** provide a "best fit" to experimental data (in particular, the measured differential elliptic flow v2(pT) of charged particles is underpredicted,
especially so for Glauber initial conditions). The above files should only be used for qualitative studies that do not require precise reproductions of the soft hadron spectra and elliptic flow,
but for which a semi-realistic model of the evolution of the fireball medium is sufficient. A comparison of the spectra and elliptic flow
from the attached calculations with experimental data is shown in arXiv:1010.1635.

NB: The combination of an early start time (required to generate sufficient radial flow to describe the proton spectra) and a "large" eta/s (about 2.5 times the KSS bound) leads to significant viscous entropy production,
reflected in the relatively low s_0 value for the initial peak entropy density.

The attached results are for the following impact parameters:

b = 3.16, 5.78, 7.49, 8.87, 10.1, and 11.1 fm

using the same T_dec, \tau_0, and \eta/s as above for all b.

**All users of these output files must give proper credit** to Chun Shen
who performed the calculations, to Pasi Huovinen who provided the EOS, and
to Huichao Song and U. Heinz who developed VISH2+1. Please refer to the following
two papers:

C. Shen, U. Heinz, P. Huovinen and H. Song, *Systematic parameter study of hadron spectra and elliptic flow from viscous hydrodynamic simulations of Au+Au collisions at sqrt(s_NN) = 200 GeV* (arXiv:1010.1856)

T. Renk, H. Holopainen, U. Heinz and C. Shen,
*A systematic comparison of jet quenching in different fluid-dynamical models* (arXiv:1010.1635) (this paper uses the attached profiles for jet quenching studies).

Back to Hydrodynamic output from various (ideal and viscous) hydro codes

*Posted by U. Heinz on 30 April 2010, 18:45; updated by UH on 15 Oct. 2010, 2:25am*