Centrality dependence of thermal freeze-out conditions at LHC in Pb plus Pb collisions at √SNN=2.76 TeV

We have analyzed the available midrapidity (vertical bar y vertical bar <0.5) transverse momentum spectra of o identified particles such as protons (p), kaons (k), k(s)(0), Lambda, Omega and Xi for different centralities of Pb+Pb collisions at the LHC energy. root(NN)-N-s = 2.76 TeV. We have used our earlier ct (7,1 proposed unified statistical thermal freeze-out model. The model incorporates the effect of nuclear transparency in such energetic collisions and the resulting asymmetry in the collective-flow profile along the longitudinal and the transverse directions. Our calculated results are found to be in good agreement with the experimental data measured by the ALICE experiment. The model calculation fits the experimental data for different particle species which provide thermal freeze-out conditions in terms of temperature and collective-flow parameters. The analysis shows a rise in the thermal freeze-out temperac.) ture and a mild decrease in the transverse collective-flow velocity as we go from central to the peripheral collisions. The baryon chemical potential is assumed to be nearly zero for the bulk of the matter (mu(B) approximate to 0), a situation expected in the heavy ion collisions at LHC energies in the Bjorken approach owing to nearly complete nuclear transparency. The contributions from the decay of the heavier resonances are also taken into account in our calculations.