Identified particle spectra in Pb-Pb, Xe-Xe and p-Pb collisions with Tsallis blast-wave model

TL;DR

This study applies the Tsallis-blast wave model to analyze identified hadron spectra in various heavy-ion collisions at LHC energies, revealing insights into system temperature, flow, and non-equilibrium behavior across different centralities and particle types.

Contribution

It introduces a combined fit approach using the Tsallis-blast wave model with different velocity profiles to describe particle spectra in heavy-ion collisions, comparing results across energies and collision systems.

Findings

Model describes spectra well up to 3 GeV/c.

Transverse flow decreases from central to peripheral collisions.

Non-equilibrium parameter q increases from central to peripheral collisions.

Abstract

We investigate the identified hadrons transverse momentum ($p_{\rm T}$) spectra in Pb-Pb (Pb-Pb, Xe-Xe, p-Pb) collisions at $\sqrt{s_{\rm NN}}=$ 2.76 (5.02, 5.44, 5.02) TeV in the framework of Tsallis-blast wave (TBW) model with a linear transverse velocity profile and with a constant velocity profile. In this model, the Tsallis temperature ($T$), the average radial flow velocity ($\langle \beta \rangle$) and the degree of non-equilibrium ($q$) of the system are common for all hadrons when a combined fit is performed to the $p_{\rm T}$ spectra of different particles at a given centrality. It is found that the model can describe the particle spectra well up to 3 GeV/c. For both profiles, the transverse flow velocity decreases from central to peripheral collisions while the non-extensive parameter $q$ exhibits the opposite behavior, indicating a more rapid expansion and less off-equilibrium of the system in more central collisions. Moreover, we observe that in central collisions $\langle \beta \rangle$ and $q$ ($T$) from the fit with the linear profile are smaller (is slightly larger) than those (that) with the constant profile, while in peripheral collisions $\langle \beta \rangle$, $T$ and $q$ from the former are compatible with those from the latter. We also derived and discussed the relation between the Tsallis temperature and the thermal temperature. In addition, to check whether a scenario of an early freeze-out of strange particles at the LHC exists, the particle spectra are investigated by grouping them into strange and non-strange hadrons. The combined fit gives an insight on the degree of non-equilibrium, the radial flow and the Tsallis temperature of the system at the kinetic decoupling. It provides a comparison between the results at different energies in the same collision system and the results in different collision systems at the same or similar energy.