Excitation function of thermal freeze-out parameters and their correlations from strange hadrons spectra in Au–Au collision at 54.4 GeV

Abstract

We present a systematic study of Gold–Gold (Au–Au) collision system at 54.4 GeV conducted by the STAR Collaboration at RHIC. The transverse momentum spectra of the strange hadrons, namely KS0, Λ, Λ̄, Ξ̄+ and Ξ− are studied at mid-rapidity |y|<0.5 for seven centrality classes. We applied the blast wave model with Tsallis statistics (TBW) with two flow profiles (n0 = 1 and n0 = 2) in order to compare the results and to check the sensitivity of n0 to the freeze-out parameters. It is found that the TBW model with both the flow profiles can describe the particle spectra. In addition, the bulk properties in terms of kinetic freeze-out temperature (T0), transverse flow velocity (βT), the non-extensive parameter (q), the kinetic freeze-out volume (V), the mean transverse momentum (〈pT〉), and the multiplicity parameter (N0) are also extracted. All the parameters decrease with decreasing the event centrality, however, the non-extensive parameter q has the opposite behavior. There is an abrupt decrease seen in 0–5% to 30–40% centrality, while a slight decrease appears in 40–60% and 60–80% centrality in T0, βT, V, and 〈pT〉. On the other hand, the parameter q follows the same scenario with an opposite trend with centrality. T0 and 〈pT〉 are larger for massive particles while βT, q, V and N0 are larger for lighter particles. The larger T0 and 〈pT〉, and smaller βT, V, and q for the massive particles affirm that the heavy particles freeze-out early. Moreover, the multiple kinetic freeze-out and volume differential freeze-out scenarios are reported, as the former increase while the latter decrease with particle mass. In addition, T0, q, V, and N0 obtained from TBW model with n0 = 1 are compatible to that of n0 = 2. On the other hand, βT is slightly larger in n0 = 2, while 〈pT〉 is slightly larger in n0 = 1. Furthermore, we also reported some important correlations among the extracted parameters. Among these correlations, the positive correlation exist between T0 and βT, T0 and V, T0 and 〈pT〉, T0 and N0, βT and 〈pT〉, βT and V, βT and N0, V and N0, and 〈pT〉 and N0, while the negative correlation of T0 and q, and 〈pT〉 and q.