Centrality dependence of hadronization and chemical freeze-out conditions in heavy ion collisions at $\sqrt s_{NN}$ = 2.76 TeV

We present an analysis of hadronic multiplicities measured in Pb-Pb collisions at ${\sqrt{s}}_{NN}=2.76$ TeV as a function of the collision centrality within the statistical hadronization model. Evidence is found of a dependence of the chemical freeze-out temperature as a function of centrality, with a slow rise from central to peripheral collisions, which we interpret as an effect of posthadronization inelastic scatterings. Using correction factors calculated by means of a simulation based on the urqmd model, we are able to obtain a significant improvement in the statistical model fit quality and to reconstruct the primordial chemical equilibrium configuration. This is characterized by a nearly constant temperature of about 164 MeV, which we interpret as the actual hadronization temperature.