Exploring thermalization and multi-freeze-out effects in Pb-Pb collisions based on Tsallis p T distributions*

Abstract This study investigates the transverse momentum ( ) distributions of , , p ( ), , and Λ in various centrality classes of Pb-Pb collisions at TeV. The experimental spectra were analyzed using the Tsallis non-extensive distribution, from which the effective temperature ( T ), non-extensive parameter ( q ), and mean transverse momentum ( ) were extracted for each particle species and centrality bin. To disentangle thermal and collective effects, the mean kinetic freeze-out temperature ( ) was obtained from the intercept of the T versus mass relation, and the average transverse flow velocity ( ) was extracted from the slope of versus mean moving mass for pions, kaons, and protons. The results show that T increases and q decreases with centrality, indicating a hotter and more equilibrated system in central collisions. A clear mass dependence of T supports the presence of a multi-freeze-out scenario, with heavier particles decoupling earlier. Both and arise from peripheral to mid-central collisions before saturating toward central events, which may suggest the onset of collective behavior or changes in freeze-out dynamics. These observations provide new insights into the thermal and dynamical properties of the medium created in heavy-ion collisions at the LHC.