Elliptic flow of charged particles in Pb-Pb collisions at 2.76 TeV

TL;DR

This paper reports the first measurement of elliptic flow of charged particles in Pb-Pb collisions at 2.76 TeV at the LHC, showing a significant increase compared to RHIC energies and aligning with viscous hydrodynamic models.

Contribution

It provides the first elliptic flow measurement at LHC energies and compares the results with lower energy data and hydrodynamic predictions.

Findings

Elliptic flow v2 is approximately 0.087 in 40-50% centrality.

Maximum v2(pT) reaches about 0.2 near 3 GeV/c.

Elliptic flow increases by about 30% compared to RHIC results.

Abstract

We report the first measurement of charged particle elliptic flow in Pb-Pb collisions at 2.76 TeV with the ALICE detector at the CERN Large Hadron Collider. The measurement is performed in the central pseudorapidity region (|$\eta$|<0.8) and transverse momentum range 0.2< $p_{\rm T}$< 5.0 GeV/$c$. The elliptic flow signal v$_2$, measured using the 4-particle correlation method, averaged over transverse momentum and pseudorapidity is 0.087 $\pm$ 0.002 (stat) $\pm$ 0.004 (syst) in the 40-50% centrality class. The differential elliptic flow v$_2(p_{\rm T})$ reaches a maximum of 0.2 near $p_{\rm T}$ = 3 GeV/$c$. Compared to RHIC Au-Au collisions at 200 GeV, the elliptic flow increases by about 30%. Some hydrodynamic model predictions which include viscous corrections are in agreement with the observed increase.