Correlation between global polarization, angular momentum and flow in heavy-ion collisions

Abstract

Possible correlations of the global polarization of $\Lambda$ hyperons with the angular momentum and transverse flow in the central region of colliding nuclei are studied based on refined estimate of the global polarization. Simulations of Au+Au collisions at collision energies $\sqrt{s_{NN}}=$ 6-40 GeV are performed within the model of the three-fluid dynamics. Within the crossover and first-order-phase-transition scenarios this refined estimate quite satisfactorily reproduces the experimental STAR data. Hadronic scenario fails at high collision energies, $\sqrt{s_{NN}}>$ 10 GeV, and even predicts opposite sign of the global polarization. It is found that the global polarization correlates with neither the angular momentum accumulated in the central region nor with directed and elliptic flow. At the same time we observed correlation between the angular momentum and directed flow in both their time and collision-energy dependence. These results suggest that, although initially the angular momentum is the driving force for the vortex generation, later the angular momentum and vortex motion become decorrelated in the midrapidity region. Then the midrapidity angular momentum is determined by the pattern of the directed flow and even becomes negative when the antiflow occurs. At the freeze-out stage, the dominant part of the participant angular momentum is accumulated in the fragmentation regions.

8 pages, 9 figures. Title changed, two figures and their discussion added, version published in Phys. Rev. C

References in corpus (12)

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• Chiral anomaly and local polarization effect from quantum kinetic approach
• Polarization and Vorticity in the Quark Gluon Plasma
• Global $\Lambda$ Polarization in high energy collisions
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• Examination of the directed flow puzzle in heavy-ion collisions
• Lattice QCD Constraints on the Nuclear Equation of State
• Directed Flow Indicates a Crossover Deconfinement Transition in Relativistic Nuclear Collisions
• Different space-time freeze-out picture -- an explanation of different $\Lambda$ and $\bar{\Lambda }$ polarization?
• Dynamical Freeze-out in 3-Fluid Hydrodynamics
• On freeze-out problem in relativistic hydrodynamics
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• Anti-flow of Mesons in the High Baryon Density Region
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