Simultaneous Analysis of Midrapidity pT Spectra of Identified Particle Species in Pb + Pb Collisions at snn = 2.76 TeV Using Tsallis Distribution with Transverse Flow

Abstract

The midrapidity transverse momentum distributions of the charged pions, kaons, protons, and antiprotons in ten groups of centrality of Pb+Pb collisions at snn = 2.76 TeV, measured by the ALICE Collaboration, have been analyzed successfully using both thermodynamically consistent and non-consistent Tsallis distribution functions with transverse flow. The collision centrality dependencies of the extracted parameters of two kinds of Tsallis functions with transverse flow have been investigated. The significantly different behavior (growth rates) of ⟨βT⟩ in regions ⟨Npart⟩ < 71 and ⟨Npart⟩ > 71 with the temperature T0 becoming constant in region ⟨Npart⟩ > 71 has been observed. This could indicate that ⟨Npart⟩ = 71±5 (corresponding to ⟨dNch/dη⟩ = 205 ± 15) is a threshold border value of collision centrality for crossover phase transition from the dense hadronic state to the QGP state (or a mixed state of QGP and hadrons) in Pb + Pb collisions at snn = 2.76 TeV. This conjecture is supported further by the observed, significantly different correlations between T0 and ⟨βT⟩ parameters in the corresponding ⟨βT⟩ < 0.44 and ⟨βT⟩ > 0.44 ranges. The strong positive linear correlation between non-extensivity parameter q for pions and kaons, between q for pions and (anti)protons, and between q for kaons and (anti)protons has been obtained. The parameter q for all studied particle species has proven to be strongly anticorrelated with the average transverse flow velocity, ⟨βT⟩. Quite a large positive linear correlation has been obtained between the q of the studied particle species and temperature parameter T0. Analysis of q versus ⟨Npart⟩ dependencies for the studied particle species suggests that the highly thermalized and equilibrated QGP is produced in central Pb + Pb collisions at snn = 2.76 TeV with ⟨Npart⟩ > 160.