In this Letter we report the first results on π±, K±, p, and p(bar) production at midrapidity (|y| < 0.5) in central Pb-Pb collisions at √s_NN = 2.76 TeV, measured by the ALICE experiment at the LHC. The pT distributions and yields are compared to previous results at √s_NN = 200 GeV and expectations from hydrodynamic and thermal models. The spectral shapes indicate a strong increase of the radial flow velocity with √s_NN, which in hydrodynamic models is expected as a consequence of the increasing particle density. While the K/π ratio is in line with predictions from the thermal model, the p/π ratio is found to be lower by a factor of about 1.5. This deviation from thermal model expectations is still to be understood.
Pion, Kaon, and Proton Production in Central Pb-Pb Collisions at √s_NN =2.76 TeV
BREGANT, MARCO;CAMERINI, Paolo;CONTIN, GIACOMO;FRAGIACOMO, ENRICO;GROSSO, Raffaele;LEA, RAMONA;MARGAGLIOTTI, GIACOMO;RUI, RINALDO;VENARUZZO, MASSIMO;ZACCOLO, VALENTINA;
2012-01-01
Abstract
In this Letter we report the first results on π±, K±, p, and p(bar) production at midrapidity (|y| < 0.5) in central Pb-Pb collisions at √s_NN = 2.76 TeV, measured by the ALICE experiment at the LHC. The pT distributions and yields are compared to previous results at √s_NN = 200 GeV and expectations from hydrodynamic and thermal models. The spectral shapes indicate a strong increase of the radial flow velocity with √s_NN, which in hydrodynamic models is expected as a consequence of the increasing particle density. While the K/π ratio is in line with predictions from the thermal model, the p/π ratio is found to be lower by a factor of about 1.5. This deviation from thermal model expectations is still to be understood.Pubblicazioni consigliate
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