Constraining models of initial state with $v_2$ and $v_3$ data from LHC and RHIC

Abstract

We present a combined analysis of elliptic and triangular flow data from LHC and RHIC using viscous relativistic hydrodynamics. Elliptic flow $v_2$ in hydrodynamics is proportional to the participant eccentricity ${\epsilon }_2$ and triangular flow is proportional to the participant triangularity ${\epsilon }_3$, which means $v_n=C_n{\epsilon }_n$, where $C_n$ is the linear response coefficient in harmonic n. Experimental data for $v_2$ and $v_3$ combined with hydrodynamic calculations of $C_n$ thus provide us with the rms values of initial anisotropies ${\epsilon }_2$ and ${\epsilon }_3$. By varying free parameters in the hydro calculation (in particular the shear viscosity), we obtain an allowed band in the (rms ${\epsilon }_2$, rms ${\epsilon }_3$) plane. Comparison with Monte-Carlo models of the initial state allows us to exclude several of these models. We 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.

6 pages, plenary talk at the International Conference on the Initial Stages in High-Energy Nuclear Collisions 2013 (IS2013), 8-14 September 2013, Illa da Toxa, Spain

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• Constraining models of initial conditions with elliptic and triangular flow data
• Constraining the viscous freeze-out distribution function with data obtained at the BNL Relativistic Heavy Ion Collider (RHIC)
• Constraining the initial temperature and shear viscosity in a hybrid hydrodynamic model of $\sqrt{s_{NN}}$=200 GeV Au+Au collisions using pion spectra, elliptic flow, and femtoscopic radii

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• Collective nuclear vibrations and initial state shape fluctuations in central Pb+Pb collisions: resolving the $v_2$ to $v_3$ puzzle
• Elliptic and Triangular Flow of Identified Particles from the AMPT Model at RHIC Energies
• Influence of collective nuclear vibrations on initial state eccentricities in Pb+Pb collisions
• Probing Nuclear Geometry through Multi-Particle Azimuthal Correlations and Rapidity-Even Dipolar Flow in ${}^{16}$O+${}^{16}$O Collisions
• Flow harmonic correlations via multi-particle symmetric and asymmetric cumulants in Au+Au collisions at \(\sqrt{s_{NN}}\) = 200 GeV