Neutral pion production at midrapidity in pp and Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV

TL;DR

This paper reports measurements of neutral pion production in proton-proton and lead-lead collisions at 2.76 TeV, revealing significant suppression in central heavy-ion collisions consistent with quark-gluon plasma formation.

Contribution

It provides the first detailed measurement of neutral pion yields and nuclear modification factors at this energy, extending previous results to higher energies and centralities.

Findings

Neutral pions are suppressed by a factor of 8-10 in central Pb-Pb collisions.

The suppression varies with transverse momentum, peaking around 5-7 GeV/c.

Results are consistent with theoretical models of parton energy loss.

Abstract

Invariant yields of neutral pions at midrapidity in the transverse momentum range $0.6 < p_{T} < 12 GeV/c$ measured in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV are presented for six centrality classes. The pp reference spectrum was measured in the range $0.4 < p_{T} < 10 GeV/c$ at the same center-of-mass energy. The nuclear modification factor, $R_{\rm AA}$, shows a suppression of neutral pions in central Pb-Pb collisions by a factor of up to about $8-10$ for $5 \lesssim p_{T} \lesssim 7 GeV/c$. The presented measurements are compared with results at lower center-of-mass energies and with theoretical calculations.