Speaker
Description
Soft hadron production in heavy-ion collisions is sensitive to the degree of equilibration and to the strength of collective expansion, both of which vary strongly with collision centrality. We study identified-hadron transverse-momentum (pT) spectra in Pb–Pb collisions at √sNN = 2.76 TeV over centralities from 0–5% to 80–90% using a Tsallis-type parameterization to extract the effective temperature T, the non-extensivity parameter q, and the mean transverse momentum ⟨pT⟩ for each species (π±, K±, p, p̄; and, where available, K0S and Λ). Clear and systematic centrality trends are observed. For π+ the extracted q increases from 1.1180 ± 0.0047 (0–5%) to 1.1607 ± 0.0027 (80–90%), while T decreases from 0.1173 ± 0.0044 GeV to 0.0723 ± 0.0019 GeV, indicating larger deviations from an exponential-like shape and a cooler effective slope toward peripheral events. For protons, q is near unity in the most central bin (1.0003 ± 0.0044) and rises to 1.0909 ± 0.0041 in 80–90%, with T decreasing from 0.4185 ± 0.0088 GeV to 0.1452 ± 0.0066 GeV. Using linear mass-scaling systematics, we define a kinetic freeze-out proxy ⟨T0⟩ that decreases from 0.0617 ± 0.0031 GeV (0–5%) to 0.0352 ± 0.0071 GeV (80–90%), and a transverse-flow proxy ⟨βT⟩ that increases from 0.0865 ± 0.0063 c (80–90%) to 0.3771 ± 0.0087 c (central). Overall, the mass ordering and the strong centrality evolution of ⟨βT⟩ are consistent with substantially stronger collective expansion in central Pb–Pb collisions, while peripheral events show weaker flow and larger non-extensive features.
| Track | Heavy Ions |
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