# Quark Matter 2014 - XXIV International Conference on Ultrarelativistic Nucleus-Nucleus Collisions

19-24 May 2014
Europe/Zurich timezone

## Constraining initial stages of heavy-ion collisions from RHIC and LHC data

20 May 2014, 16:30
2h

### spectrum

Board: H-30
Poster Collective Dynamics

### Speaker

Ekaterina Retinskaya (CEA)

### Description

We propose a systematic approach for constraining models of initial conditions using a combined analysis of elliptic $v_2$ and triangular $v_3$ flow data with viscous hydrodynamic calculations. For $v_2$ and $v_3$ harmonics the hydrodynamic response to the initial state is dominated by linear response, which means $v_2$ is proportional to the ellipticity $\varepsilon_2$ and $v_3$ is proportional to the triangularity $\varepsilon_3$, i.e. $v_n = C_n\varepsilon_n$, where $C_n$ is the linear response coefficient. Experimental data on elliptic and triangular flow, combined with the calculation of $C_n$ in relativistic hydrodynamics, provide us with rms values of initial anisotropies $\varepsilon_2$ and $\varepsilon_3$. By varying free parameters in hydrodynamic calculations, we get an allowed region in the (rms $\varepsilon_2$, rms $\varepsilon_3$) plane. Thus we are able to compare Monte Carlo models of the initial state with the allowed region and exclude several of these models. We provide a simple test that can be performed on any candidate model to determine its compatibility with data. We also illustrate that the effect of changing the granularity of the initial state is similar to changing the medium properties, making these effects difficult to disentangle using only these data. [Reference: E. Retinskaya, M. Luzum and J. -Y. Ollitrault, Phys. Rev. C 89, 014902 (2014)]

### Primary author

Ekaterina Retinskaya (CEA)

### Co-authors

Dr Jean-Yves Ollitrault (CNRS) Matthew Luzum (MCGill, LBNL)

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