Neutral pion and η meson production at midrapidity in Pb-Pb collisions at √sNN=2.76 TeV

Abstract

Neutral pion and η meson production in the transverse momentum range 1 < p_T < 20 GeV/c have been measured at midrapidity by the ALICE experiment at the Large Hadron Collider (LHC) in central and semicentral Pb-Pb collisions at √sNN = 2.76 TeV. These results were obtained using the photon conversion method as well as the Photon Spectrometer (PHOS) and Electromagnetic Calorimeter detectors. The results extend the upper p_T reach of the previous ALICE π^0 measurements from 12 to 20 GeV/c and present the first measurement of η meson production in heavy-ion collisions at the LHC. The η/π^0 ratio is similar for the two centralities and reaches at high p_T a plateau value of 0.457 ± 0.013^[stat] ± 0.018^[syst]. A suppression of similar magnitude for π^0 and η meson production is observed in Pb-Pb collisions with respect to their production in pp collisions scaled by the number of binary nucleon-nucleon collisions. We discuss the results in terms of Next to Leading Order (NLO) pQCD predictions and hydrodynamic models. The measurements show a stronger suppression than observed at lower center-of-mass energies in the p_T range 6 < p_T < 10 GeV/c. For p_T < 3 GeV/c, hadronization models describe the π^0 results while for the η some tension is observed.