Centrality dependence of π , K , and p production in Pb-Pb collisions at s N N = 2.76 TeV

In this paper measurements are presented of ${ensuremath{pi}}^{ifmmodepmelsetextpmfi{}}$, ${K}^{ifmmodepmelsetextpmfi{}}$, $p$, and $overline{p}$ production at midrapidity ($|y|<0.5$), in Pb-Pb collisions at $sqrt{{s}_{NN}}=2.76$ TeV as a function of centrality. The measurement covers the transverse-momentum (${p}_{T}$) range from 100, 200, and 300 MeV/$c$ up to 3, 3, and 4.6 GeV/$c$ for $ensuremath{pi}$, $K$, and $p$, respectively. The measured ${p}_{T}$ distributions and yields are compared to 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 ${p}_{T}$ 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 $ensuremath{sim}$1.5 lower than the expectation from thermal models.