Multiplicity, mean $p_T$, $p_T$-spectra and elliptic flow of identified particles in Pb+Pb collisions at LHC

Abstract

Israel-Stewart's causal theory of dissipative hydrodynamics, with the ADS/CFT lower limit of shear viscosity to entropy ratio ($\eta/s$=0.08), give consistent description of a number of experimental observables in Au+Au collisions at RHIC (c.m. energy $\sqrt{s}$=200 GeV) \cite{Chaudhuri:2008sj}. Assuming that in Pb+Pb collisions at LHC (c.m. energy $\sqrt{s}$=5.5 TeV), except for the initial temperature, other parameters of the fluid remain unchanged, we have predicted for the centrality dependence of multiplicity, mean $p_T$, $p_T$-spectra, elliptic flow. The central temperature of the fluid is adjusted to $T_i$=421 MeV such that in a Pb+Pb collision, with participant number $N_{part}$=350, average charge particle multiplicity is $\sim$ 900 and is consistent with the experimental trend observed at lower energies. Compare to Au+Au collisions at RHIC, in Pb+Pb collisions at LHC, on the average, particle multiplicity increases by a factor of $\sim$1.6, the mean $p_T$ is increased by $\sim$10% only. The elliptic flow on the other hand decreases by $\sim$15%.