Neutral pion and η meson production in p–Pb collisions at √sNN = 5.02 TeV

Abstract

Neutral pion and η meson invariant differential yields were measured in non-single diffractive p–Pb colli- sions at √sNN = 5.02 TeV with the ALICE experiment at the CERN LHC. The analysis combines results from three complementary photon measurements, utilizing the PHOS and EMCal calorimeters and the Photon Conversion Method. The invariant differential yields of π0 and η meson inclu- sive production are measured near mid-rapidity in a broad transverse momentum range of 0.3 < pT < 20 GeV/c and 0.7 < pT < 20 GeV/c, respectively. The measured η/π0 ratio increases with pT and saturates for pT > 4 GeV/c at 0.483 ± 0.015stat ± 0.015sys . A deviation from m T scaling is observed for pT < 2 GeV/c. The measured η/π0 ratio is consistent with previous measurements from proton-nucleus and pp collisions over the full pT range. The measured η/π0 ratio at high pT also agrees within uncertainties with measure- ments from nucleus–nucleus collisions. The π 0 and η yields in p–Pb relative to the scaled pp interpolated reference, RpPb, arepresentedfor0.3< pT <20GeV/cand0.7< pT <20 GeV/c, respectively. The results are compared with theoreti- cal model calculations. The values of RpPb are consistent with unity for transverse momenta above 2 GeV/c. These results support the interpretation that the suppressed yield of neutral mesons measured in Pb–Pb collisions at LHC energies is due to parton energy loss in the hot QCD medium.