v4,v5,v6,v7: Nonlinear hydrodynamic response versus LHC data

• DOI: 10.1016/j.physletb.2015.03.040
• Publication Date: 2015-03-28T00:18:47Z
• Authors: Li Yan; Jean-Yves Ollitrault
• Keywords: [PHYS.NUCL]Physics [physics]/Nuclear Theory [nucl-th]; Nuclear Theory; Physics; QC1-999; FOS: Physical sciences; [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex]; 01 natural sciences; Nuclear Theory (nucl-th); High Energy Physics - Phenomenology; High Energy Physics - Phenomenology (hep-ph); [PHYS.HPHE]Physics [physics]/High Energy Physics - Phenomenology [hep-ph]; 0103 physical sciences; Nuclear Experiment (nucl-ex); Nuclear Experiment

Higher harmonics of anisotropic flow ($v_n$ with $n\ge 4$) in heavy-ion collisions can be measured either with respect to their own plane, or with respect to a plane constructed using lower-order harmonics. We explain how such measurements are related to event-plane correlations. We show that CMS data on $v_4$ and $v_6$ are compatible with ATLAS data on event-plane correlations. If one assumes that higher harmonics are the superposition of non-linear and linear responses, then the linear and non-linear parts can be isolated under fairly general assumptions. By combining analyses of higher harmonics with analyses of $v_2$ and $v_3$, one can eliminate the uncertainty from initial conditions and define quantities that only involve nonlinear hydrodynamic response coefficients. Experimental data on $v_4$, $v_5$ and $v_6$ are in good agreement with hydrodynamic calculations. We argue that $v_7$ can be measured with respect to elliptic and triangular flow. We present predictions for $v_7$ versus centrality in Pb-Pb collisions at the LHC.<br/>7 pages and 3 figures<br/>