Probing rotational dynamics of quark gluon plasma via global vorticity

Abstract

The findings on the spin polarization of Λ, Ξ, and Ω hyperons and spin alignment of K ⁎0, ϕ , and D*+ mesons in relativistic heavy-ion collision experiments at the RHIC and LHC facilities propose the emergence of a strong vorticity field produced in these collisions. Contemplating the potential impact of vorticity on the space-time evolution of deconfined QCD matter and its freeze-out properties, we aim to investigate its characteristics within the medium. We introduce a complementary and data-driven approach to quantify the global vorticity field by extracting it directly from the transverse momentum spectra of produced hadrons. Employing the experimental data for Λ, Ξ, Ω, K ⁎0, K * ±, ϕ, ρ , and D*+ at mid-rapidity in Au+Au and Pb+Pb collisions over a wide range of beam energies, sNN=7.7 GeV-5.02 TeV, and centrality classes, we systematically examine spin-vorticity coupling in the medium. Our finding on the magnitude of the extracted vorticity is consistent with values deduced from Λ and Λ¯ polarization measurements using statistical thermal models under the non-relativistic limit. Notably, we observe a prominent particle-species dependence of the vorticity, as well as a non-trivial variation with collision centrality and beam energy. These results indicate that vorticity-driven spin phenomena are sensitive to hadron structure and freeze-out dynamics, providing new constraints on the rotational properties of the QCD matter.