Measurement of the azimuthal anisotropy of neutral pions in PbPb collisions at sqrt(s(NN)) = 2.76 TeV

TL;DR

This paper reports the first measurement of the azimuthal anisotropy (v2) of neutral pions in PbPb collisions at 2.76 TeV, revealing insights into the quark-gluon plasma's properties at high energies.

Contribution

It provides the first measurement of neutral pion azimuthal anisotropy at LHC energies, extending previous results from RHIC to higher collision energies.

Findings

v2 values are similar to RHIC results despite higher energy

Neutral pion anisotropies are smaller than charged particle anisotropies in the studied range

Results suggest consistent collective behavior across different energies

Abstract

First measurements of the azimuthal anisotropy of neutral pions produced in PbPb collisions at a center-of-mass energy of sqrt(s(NN)) = 2.76 TeV are presented. The amplitudes of the second Fourier component (v2) of the neutral pion azimuthal distributions are extracted using an event-plane technique. The values of v2 are studied as a function of the neutral pion transverse momentum (pt) for different classes of collision centrality in the kinematic range 1.6 < pt < 8.0 GeV, within the pseudorapidity interval abs(eta) < 0.8. The CMS measurements of v2(pt) are similar to previously reported neutral pion azimuthal anisotropy results from sqrt(s(NN)) = 200 GeV AuAu collisions at RHIC, despite a factor of about 14 increase in the center-of-mass energy. In the momentum range 2.5 < pt < 5.0 GeV, the neutral pion anisotropies are found to be smaller than those observed by CMS for inclusive charged particles.