Thermodynamic analysis of transverse momentum spectra in Pb–Pb collisions at 2.76 TeV: centrality dependence of temperature, freezeout parameters and non-extensitivity

We study properties of Pb–Pb collisions at 2.76 TeV in mid-rapidity, |y|<0.5, based on data by the ALICE Collaboration. In particular, we examine the transverse momentum (pT) spectra of positively charged (identified) hadrons, π+,K+ and p, generated in various centrality intervals. We perform individual fits using the thermodynamically consistent Tsallis distribution to extract the following quantities: the non-extensitivity parameter, q, the effective temperature, Teff, the kinetic freezeout volume, V, the mean transverse flow velocity, βT, the mean kinetic freezeout temperature, ⟨T0⟩, the thermal temperature, Tth, and the parameter ζ, which characterizes the fluctuating number of generated particles. From peripheral to central collision, and from lower to higher charged particle multiplicity per pseudorapidity unit, ⟨dNch/dη⟩, all these quantities are observed to increase, with the exception of q, which has the opposite behavior. The parameters Teff,q, and V depend on the hadron mass in a way that supports the scenarios of volume differential freezeout and multiple kinetic freezeout. Furthermore, we extracted ⟨Teff⟩ and ⟨q⟩ for different collisions and energies at LHC and RHIC, and compare their dependencies on ⟨dNch/dη⟩ and ⟨Npart⟩.