Charged Particle’s elliptic flow in 2+1D viscous hydrodynamics at LHC (√s=2.76 TeV) Energy in Pb+Pb collision. and QGP viscosity

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Théâtre National (Centre Bonlieu)

Théâtre National

Centre Bonlieu

Poster Global and collective dynamics


Dr Asis Chaudhuri (Variable Energy Cyclotron Centre)


The azimuthal correlation of produced particles in the reaction plane or elliptic flow in heavy ion collision is a sensitive probe to (i) degree of thermalization (ii) transport coefficient and (iii) the equation of state (EoS) of the medium. Recently, ALICE collaboration measured (differential) elliptic flow in √s=2.76 TeV Pb-Pb collision [1]. We have analyzed the elliptic flow data to obtain an estimate of viscosity to entropy ratio $\eta$/s at LHC energy. Details can be found in [2]. In Israel-Stewart's second order theory of hydrodynamics, we have simulated elliptic flow in 2.76 TeV Pb+Pb collisions. We have assumed that initial Pb+Pb collisions produces a QGP fluid which thermalizes in the time scale, $\tau_i$=0.6 fm/c. Hydrodynamical evolution of the fluid is governed by a lattice motivated equation of state with confinement-deconfinement cross-over transition at Tc=174 MeV. The initial condition of the fluid was fixed to reproduce ALICE measurements for charged particles multiplicity in 0-5% collisions. Ideal QGP fluid require rather large initial energy density, ei=90 GeV/fm^3. Initial energy density is reduced if the fluid is viscous, e.g. ei =78, 70, 60 GeV/fm^3 for viscosity to entropy ratio η/s=0.08, 0.12 and 0.16 respectively. ALICE data for charged particles elliptic flow in 20-30%, 30-40% and 40-50% collision are best explained for fluid viscosity η/s=0.08. In very central 10-20% collisions however, ALICE data prefer ideal fluid rather than a viscous fluid. We conclude that nearly perfect fluid is consistent with the ALICE data for elliptic flow in 2.76 TeV Pb+Pb collisions. [1] K.Aamodt et al. arXiv: 1011.3914[nucl-ex]. [2] Victor Roy and A.K. Chaudhuri , [arXiv: 1103.2870[nucl-th]].

Primary author

Dr Asis Chaudhuri (Variable Energy Cyclotron Centre)


Mr Victor Roy (Variable Energy Cyclotron Centre)

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