Elliptic Flow from a Beam Energy Scan: a signature of a phase transition to the Quark-Gluon Plasma

2013/04/24 by S. Plumari, Plumari, S., V. Greco +3
Physics and Astronomy · #FOS: Physical sciences #High Energy Physics - Phenomenology (hep-ph) #Nuclear Experiment (nucl-ex) #Nuclear Theory (nucl-th) #hep-ph #nucl-ex #nucl-th

paper · pdf · doi:10.48550/arxiv.1304.6566

5 pages, 3 figures

arxiv created 2013/04/24 · arxiv updated 2013/04/25

Abstract

We employ a relativistic transport theory to describe the fireball expansion of the matter created in ultra-relativistic heavy-ion collisions (uRHICs). Developing an approach to fix locally the shear viscosity to entropy density η/s, we study the impact of a temperature dependent η/s(T) on the build-up of the elliptic flow, v₂, a measure of the angular anisotropy in the particle production. Beam Energy Scan from √s_NN= \rm 62.4 GeV at RHIC up to 2.76 TeV at LHC has shown that the v₂(p_T) as a function of the transverse momentum p_T appears to be nearly invariant with energy. We show that such a surprising behavior is determined by a rise and fall of η/s(T) with a minimum at T∼ T_c, as one would expect if the matter undergoes a phase transition or a cross-over. This provides an evidence for phase transition occurring in the uRHIC's and a first constraint on the temperature dependence of η/s. In particular, a constant η/s at all temperatures or a too strong T-dependence would cause a breaking of the scaling of v₂(p_T) with the energy.

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