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

TL;DR

This paper predicts particle multiplicity, mean transverse momentum, spectra, and elliptic flow in Pb+Pb collisions at LHC energies using hydrodynamic models calibrated on RHIC data, highlighting expected differences at higher energies.

Contribution

It extends hydrodynamic predictions from RHIC to LHC energies, assuming unchanged parameters except initial temperature, providing specific forecasts for observables in Pb+Pb collisions.

Findings

Particle multiplicity increases by ~1.6 times at LHC.

Mean p_T increases by ~10%.

Elliptic flow decreases by ~15%.

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%.