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 s N N (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 (T 0 ) and radial flow velocity ( β T ) increase with the increase of s N N , which indicates a higher excitation and larger expansion of the interesting system at the LHC. Both the values of T 0 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.