Centrality dependence of $\pi$, K, p production in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV

In this paper measurements are presented of $\pi^\pm, K^\pm$, p and $\bar p$ production at mid-rapidity (|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, 300 MeV/c up to 3, 3, 4.6 GeV/c, for $\pi$, 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 ~ 1.5 lower than the expectation from thermal models.