Abstract
We demonstrate that measurements of rapidity differential anisotropic flow in heavy-ion collisions can constrain the temperature dependence of the shear viscosity to entropy density ratio of QCD matter. Comparing results from hydrodynamic calculations with experimental data from the RHIC, we find evidence for a small in the QCD crossover region and a strong temperature dependence in the hadronic phase. A temperature independent is disfavored by the data. We further show that measurements of the event-by-event flow as a function of rapidity can be used to independently constrain the initial state fluctuations in three dimensions and the temperature dependent transport properties of QCD matter.
- Received 15 December 2015
DOI:https://doi.org/10.1103/PhysRevLett.116.212301
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