Extracting kinetic freeze-out temperature and radial flow velocity from an improved Tsallis distribution

We analyze the transverse-momentum (p_T) spectra of identified particles (π^±, K^±, p, and p¯) produced in gold-gold (Au-Au) and lead-lead (Pb-Pb) collisions over a sNN (center-of-mass energy per nucleon pair) range from 14.5 GeV (one of the Relativistic Heavy Ion Collider (RHIC) energies) to 2.76 TeV (one of the Large Hadron Collider (LHC) energies). For the spectra with a narrow p_T range, an improved Tsallis distribution which is in fact the Tsallis distribution with radial flow is used. For the spectra with a wide p_T range, a superposition of the improved Tsallis distribution and an inverse power law is used. Both the extracted kinetic freeze-out temperature (T₀) and radial flow velocity (β_T) increase with the increase of sNN, which indicates a higher excitation and larger expansion of the interesting system at the LHC. Both the values of T₀ and β_T in central collisions are slightly larger than those in peripheral collisions, and they are independent of isospin and slightly dependent on mass.