Scaling of the higher-order flow harmonics: implications for initial-eccentricity models and the "viscous horizon"

Abstract

The scaling properties of the flow harmonics for charged hadrons $v_n$ and their ratios $[v_n/(v_2{)}^{n/2}{]}_{n\ge 3}$, are studied for a broad range of transverse momenta ($p_T$) and centrality selections in Au+Au and Pb+Pb collisions at $\sqrt{s_{NN}}=0.2\text{and}2.76$ TeV respectively. At relatively low $p_T$, these scaling properties are found to be compatible with the expected growth of viscous damping for sound propagation in the plasma produced in these collisions. They also provide important constraints for distinguishing between the two leading models of collision eccentricities, as well as a route to constrain the relaxation time and make estimates for the ratio of viscosity to entropy density $\eta /s$, and the "viscous horizon" or length-scale which characterizes the highest harmonic which survives viscous damping.

5 pages 4 figs: Modifications made for added transparency

Cited by in corpus (8)

• Energy dependence and fluctuations of anisotropic flow in Pb-Pb collisions at $\sqrt{{\text{s}}_{\text{NN}}}=5.02$ and $2.76$ TeV
• Measurement of the higher-order anisotropic flow coefficients for identified hadrons in Au$+$Au collisions at $\sqrt{s_{{}_{NN}}}$ = 200 GeV
• Azimuthal anisotropy in Cu+Au collisions at $\sqrt{s_{{}_{NN}}}$ = 200 GeV
• A systematic study of the sensitivity of triangular flow to the initial state fluctuations in relativistic heavy-ion collisions
• A first estimate of $\eta /s$ in Au+Au reactions at E${}_{\mathrm{lab}}=1.23$ $A$GeV
• Beam energy dependence of the expansion dynamics in relativistic heavy ion collisions: Indications for the critical end point?
• Harmonic moments of the gluon density distribution in AA collisions
• Effects of causality on the fluidity and viscous horizon of quark-gluon plasma