Transverse Dynamics of Strange Hadrons in Relativistic Heavy-Ion Collisions

We present a study of the mean transverse momentum pT of identified strange hadrons (KS0,Λ,Λ¯,Ξ−,Ξ¯+,ϕ,Ω−,Ω¯+) produced in Au+Au collisions at RHIC-BES energies (the nucleon–nucleon center-of-mass energy sNN=7.7 GeV,11.5 GeV,19.6 GeV,27 GeV and 39 GeV). The mean transverse momentum is obtained from transverse momentum spectra of the strange hadrons as measured by the STAR experiment and its dependence on the number of participants Npart is studied. For RHIC-BES energies, experimental data indicate a centrality dependence of pT, with an increase towards central collisions. This dependency is described using a power-law function to fit the data. The power-law exponent α is used to characterize the degree of flattening of pT with respect to Npart and its dependency on the collision energy and particle mass is studied. Special emphasis is placed on ϕ-meson that has a smaller interaction cross-section, thus reflecting the properties of the early stages of the system’s evolution. The pT of ϕ-mesons produced in Au+Au collisions at RHIC-BES energies are compared with the results obtained in Au+Au collisions at higher RHIC energies and in Pb+Pb collisions at SPS and LHC energies. A distinct energy dependence of ϕpT values is identified. Furthermore, data indicate, when comparing peripheral and central heavy-ion collisions, that ϕ-meson pT increases with system size, following two distinct trends. The results are compared with the predictions of the default and string-melting versions of the AMPT generator. We observe that the string-melting AMPT version describes the strange meson pT, but underpredicts the strange baryon pT centrality dependence. The default AMPT overpredicts the KS0 and ϕ meson pT centrality dependence, while the strange baryon data are in general better described by this version of the model. The exponent α obtained from AMPT-simulated results does not describe the measurements satisfactorily.