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

Abstract

We analyze the transverse momentum ($p_T$) spectra of identified particles ($π^{\pm}$, $K^{\pm}$, $p$, and $\bar p$) produced in gold-gold (Au-Au) and lead-lead (Pb-Pb) collisions over a $\sqrt{s_{NN}}$ (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 $\sqrt{s_{NN}}$, 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.

We have corrected the pseudorapidity ranges of the data quoted in this paper. The PHENIX data should be in the pseudorapidity range $|η|<0.35$, but not the rapidity range $|y|<0.5$; and the ALICE data should be in $|η|<0.8$ for high transverse momentum region and $|y|<0.5$ for low transverse momentum region, but not only $|y|<0.5$. These do not affect the results of the publication