Centrality dependence of Pion, Kaon, and Proton Production in Pb-Pb Collisions at snn = 2.76 TeV

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2.76 TeV
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In this paper the measurements of $\pi^{\pm}$, K$^{\pm}$, p and $\bar{\rm p}$   production at mid-rapidity ($\left|y\right|<0.5$), in Pb-Pb  collisions at $\snn=2.76$ TeV as a function of centrality, are presented. The  measured $\pt$ distributions and extracted yields are compared with expectations based on  hydrodynamic, thermal and recombination models.  The spectral  shapes of central collisions show a stronger radial flow than  measured at lower energies, which  can be described in hydrodynamic models. In peripheral  collisions, the $\pt$ distributions are not well reproduced by  hydrodynamic models.   Ratios of integrated particle yields are found to be nearly independent of centrality. The yield of protons  normalized to pions is a factor $\sim 1.5$ lower than the  expectation from thermal models.