Higher harmonic anisotropic flow measurements of charged particles in Pb-Pb collisions at 2.76 TeV

TL;DR

This paper presents the first measurements of higher harmonic flow coefficients (v3, v4, v5) in Pb-Pb collisions at 2.76 TeV, providing insights into initial state fluctuations and their effects on particle correlations.

Contribution

It reports novel measurements of higher harmonic flow coefficients and links them to initial spatial anisotropies, enhancing understanding of the collision dynamics.

Findings

Triangular flow v3 correlates with initial spatial anisotropy.

Double peaked azimuthal correlations explained by measured flow coefficients.

Flow measurements constrain models of initial state fluctuations.

Abstract

We report on the first measurement of the triangular $v_3$, quadrangular $v_4$, and pentagonal $v_5$ charged particle flow in Pb-Pb collisions at 2.76 TeV measured with the ALICE detector at the CERN Large Hadron Collider. We show that the triangular flow can be described in terms of the initial spatial anisotropy and its fluctuations, which provides strong constraints on its origin. In the most central events, where the elliptic flow $v_2$ and $v_3$ have similar magnitude, a double peaked structure in the two-particle azimuthal correlations is observed, which is often interpreted as a Mach cone response to fast partons. We show that this structure can be naturally explained from the measured anisotropic flow Fourier coefficients.