Evolution of transverse momentum spectra of primary charged particles produced in high-energy Pb+Pb collisions at the LHC with changing collision centrality

The evolution of mid-rapidity pT spectra of primary charged particles in Pb+Pb collisions at √sNN = 2.76 and 5.02 TeV, measured by ALICE up to 15 GeV/c, has been analyzed using a thermodynamically consistent Tsallis distribution with transverse flow. Comparisons with earlier low-pT analyses show that transverse flow is absent at low and begins to emerge around 40–50% centrality at 2.76 TeV and 50–60% at 5.02 TeV. The kinetic freeze-out temperature T0 decreases noticeably with increasing centrality. The estimated crossover boundary occurs at = 109 ± 8 and 71 ± 7 for 2.76 TeV and 5.02 TeV, respectively. The non-extensivity parameter q systematically decreases with , indicating stronger thermalization. Strong negative correlations are found between q and as well as . Moreover, T0 is anticorrelated with the average transverse flow velocity . Results agree with earlier studies and with p+p and p+Pb data.