Measurement of the azimuthal anisotropy of neutral pions in Pb-Pb collisions at root S-NN=2.76 TeV

Abstract

irst measurements of the azimuthal anisotropy of neutral pions produced in Pb-Pb collisions at a center-of-mass energy of root S-NN = 2.76 TeV are presented. The amplitudes of the second Fourier component (upsilon(2)) of the pi(0) azimuthal distributions are extracted using an event-plane technique. The values of upsilon(2) are studied as a function of the neutral pion transverse momentum (p(T)) for different classes of collision centrality in the kinematic range 1.6< p(T)<8.0 GeV/c, within the pseudorapidity interval vertical bar eta vertical bar < 0.8. The CMS measurements of upsilon(2)(p(T)) are similar to previously reported pi(0) azimuthal anisotropy results from root S-NN = 200 GeV Au-Au collisions at RHIC, despite a factor of similar to 14 increase in the centerof-mass energy. In the momentum range 2.5<p(T)<5.0 GeV/c, the neutral pion anisotropies are found to be smaller than those observed by CMS for inclusive charged particles.