M ar 2 00 7 Energy dependence of π ± , p and p̄ transverse momentum spectra for Au + Au collisions at √ s NN = 62 . 4 and 200 GeV
نویسندگان
چکیده
We study the energy dependence of the transverse momentum (pT) spectra for charged pions, protons and anti-protons for Au+Au collisions at √ 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 p̄/π ratios for central collisions at √ 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 p̄/π ratios are smaller. For pT > 2 GeV/c, the p̄/π − ratios at the two beam energies are independent of pT and centrality indicating that the dependence of the p̄/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.
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