Article

# The QGP shear viscosity -- elusive goal or just around the corner?

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(Impact Factor: 2.78). 06/2011; 38(12). DOI: 10.1088/0954-3899/38/12/124045
Source: arXiv

ABSTRACT

With the new viscous hydrodynamic + hadron cascade hybrid code VISHNU, a
rather precise (O(25%)) extraction of the QGP shear viscosity (eta/s)_QGP from
heavy-ion elliptic flow data is possible if the initial eccentricity of the
collision fireball is known with <5% accuracy. At this point, eccentricities
from initial state models differ by up to 20%, leading to an O(100%)
uncertainty for (eta/s)_QGP. It is shown that a simultaneous comparison of
elliptic and triangular flow, v_2 and v_3, puts strong constraints on initial
state models and can largely eliminate the present uncertainty in (eta/s)_QGP.
The variation of the differential elliptic flow v_2(p_T) for identified hadrons
between RHIC and LHC energies provides additional tests of the evolution model.

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• "Refs. [1] [2] and references therein), its first principles determination has proved notoriously challenging. As lattice QCD is limited to the Euclidean formulation of the theory and weak coupling expansions of transport constants are tedious to perform and display slow convergence [3], much attention has lately shifted to gauge gravity calculations. "
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