https://doi.org/10.1140/epjp/s13360-025-06511-w
Regular Article
Centrality and energy dependencies of kinetic freeze-out parameters in high-energy p + Pb, Xe + Xe, and Pb + Pb collisions at the LHC
1
Physical-Technical Institute of Uzbekistan Academy of Sciences, Chingiz Aytmatov Str. 2b, 100084, Tashkent, Uzbekistan
2
New Uzbekistan University, Tashkent, Uzbekistan
3
National University of Science and Technology MISIS (NUST MISIS), Almalyk Branch, Almalyk, Uzbekistan
4
Institute of Physics and Technology, Satbayev University, Almaty, Kazakhstan
5
Institute of Nuclear Physics, Almaty, Kazakhstan
6
Institute of Theoretical Physics, Shanxi University, 030006, Taiyuan, China
7
Samarkand State University named after Sh. Rashidov, Samarkand, Uzbekistan
a khkolimov@gmail.com, kh.olimov@uzsci.net
b fuhuliu@163.com, fuhuliu@sxu.edu.cn
Received:
25
March
2025
Accepted:
2
June
2025
Published online:
18
June
2025
Centrality and energy dependencies of kinetic freeze-out parameters of the collision system have been studied analyzing the low pT ≤ 2 GeV/c range of the midrapidity experimental transverse momentum distributions of identified particle species, measured by the ALICE Collaboration in Pb + Pb collisions at (snn)1/2 = 2.76 and 5.02 TeV, Xe + Xe collisions at (snn)1/2 = 5.44 TeV, and in p + Pb collisions at (snn)1/2 = 5.02 TeV, with the help of thermodynamic Maxwell–Boltzmann distribution function with embedded transverse flow. The average transverse flow velocity, < βT > , demonstrates the similar dependencies on the average number of participant protons, < Npart > , in Pb + Pb collisions at (snn)1/2 = 2.76 and 5.02 TeV, and Xe + Xe collisions at (snn)1/2 = 5.44 TeV: firstly < βT > increases at a high rate in the lower < Npart > range, then the degree of increase of < βT > decreases significantly with an increase in < Npart > , showing an almost plateau-like behavior in the region of the large < Npart > . In case of p + Pb collisions at (snn)1/2 = 5.02 TeV, < βT > also increases with an increase in < Npart > . However, no plateau-like region of < βT > is observed for p + Pb collisions at large < Npart > values. This is likely due to the narrow < Npart > range in p + Pb collisions at (snn)1/2 = 5.02 TeV as compared to much larger < Npart > range in Pb + Pb collisions at (snn)1/2 = 2.76 TeV and 5.02 TeV, and Xe + Xe collisions at (snn)1/2 = 5.44 TeV. The central Pb + Pb, Xe + Xe, and p + Pb collisions at the LHC have been characterized by the significantly smaller values of the kinetic freeze-out temperature, T0, as compared to the significantly larger values of T0 in peripheral collisions. The values of the kinetic freeze-out temperature, T0, in most peripheral collisions have proved to be approximately equal to the chemical freeze-out temperature, Tch, of about 150–160 MeV. On the other hand, the T0 values have been significantly smaller than Tch in central Pb + Pb, Xe + Xe, and p + Pb collisions at the LHC. It is concluded that the fireball produced in central heavy-ion collisions at the LHC lives significantly longer time and decays at significantly lower temperature, T0, as compared to the significantly shorter lifetime (and, hence, significantly larger T0) of the fireball produced in more peripheral collisions. The kinetic freeze-out temperatures, T0, have coincided in Pb + Pb collisions at (snn)1/2 = 5.02 TeV and Xe + Xe collisions at (snn)1/2 = 5.44 TeV, being noticeably and consistently larger than T0 in Pb + Pb collisions at (snn)1/2 = 2.76 TeV. Parameters T0 and 
have been strongly anticorrelated in all analyzed p + Pb collisions at (snn)1/2 = 5.02 TeV, Pb + Pb collisions at (snn)1/2 = 2.76 and 5.02 TeV, and Xe + Xe collisions at (snn)1/2 = 5.44 TeV at the LHC with the value of linear correlation coefficient being very close to − 1.
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© The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2025
Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
