Description of Midrapidity pT Spectra of Primary Charged Particles with Changing Centrality and Energy of Pb+Pb and Xe+Xe Collisions at the LHC with a Two-Component Model

A two-component model, which is the sum of thermodynamically consistent Tsallis function with embedded transverse flow and inverse power-law function (which is asymptotic of Hagedorn function at very high pT), has been proposed to reproduce accurately the measured long pT ranges of midrapidity transverse momentum spectra of primary charged particles at various centralities of high-energy heavy-ion collisions at the LHC. This two-component model function, called Tsallis-Hagedorn model with transverse flow (THMTF), has described quite well the experimental midrapidity transverse momentum spectra of primary charged particles in the whole pT range, measured by ALICE Collaboration in minimum bias p+p collisions at √s=2.76 and 5.02 TeV, minimum bias p+Pb collisions at √snn=5.02 TeV, and various collision centrality intervals of Xe+Xe collisions at √snn=5.44 TeV and Pb+Pb collisions at √snn =2.76 and 5.02 TeV. Dependencies of non-extensivity parameter q, kinetic freeze-out temperature parameter, T0, momentum scale parameter, P0, and power-index n of the two-component THMTF function on the average number of participant nucleons ( ) as well as mean charged-particle multiplicity density ( ) in the analyzed Xe+Xe and Pb+Pb collisions at the LHC have been established. The probable border (threshold) values of collision centrality (values of ) for crossover phase transition from the dense hadronic state to that of QGP in Pb+Pb collisions at √snn= 2.76 and 5.02 TeV, and in Xe+Xe collisions at √snn=5.44 TeV have been estimated. The average number of partons participating in a scattering, nα=5, has been estimated from extracted average value of power-index n in the analyzed collisions. This has suggested that g+q→meson+q and g+g→meson+g gluon fragmentation reactions are the dominant mechanism for high pT hadron production in the analyzed p+p, p+Pb, Xe+Xe, and Pb+Pb collisions at the LHC.