Energy dependence of π±, p and over(p, ̄) transverse momentum spectra for Au + Au collisions at sqrt(sNN) = 62.4 and 200 GeV

Abstract

We study the energy dependence of the transverse momentum (pT) spectra for charged pions, protons and anti-protons for Au + Au collisions at sqrt(sNN) = 62.4 and 200 GeV. Data are presented at mid-rapidity (| y | < 0.5) for 0.2 < pT < 12 GeV / c. In the intermediate pT region (2 < pT < 6 GeV / c), the nuclear modification factor is higher at 62.4 GeV than at 200 GeV, while at higher pT (pT > 7 GeV / c) the modification is similar for both energies. The p / π+ and over(p, ̄) / π- ratios for central collisions at sqrt(sNN) = 62.4 GeV peak at pT ≃ 2 GeV / c. In the pT range where recombination is expected to dominate, the p / π+ ratios at 62.4 GeV are larger than at 200 GeV, while the over(p, ̄) / π- ratios are smaller. For pT > 2 GeV / c, the over(p, ̄) / π- ratios at the two beam energies are independent of pT and centrality indicating that the dependence of the over(p, ̄) / π- ratio on pT does not change between 62.4 and 200 GeV. These findings challenge various models incorporating jet quenching and/or constituent quark coalescence. © 2007 Elsevier B.V. All rights reserved.