Abstract
Global polarization of hyperons has been measured to be of the order of a few tenths of a percentage in Au+Au collisions at = 200 GeV, with no significant difference between and . These new results reveal the collision energy dependence of the global polarization together with the results previously observed at = 7.7–62.4 GeV and indicate noticeable vorticity of the medium created in noncentral heavy-ion collisions at the highest Relativistic Heavy Ion Collider collision energy. The signal is in rough quantitative agreement with the theoretical predictions from a hydrodynamic model and from a multi-phase transport model. The polarization is larger in more peripheral collisions, and depends weakly on the hyperon's transverse momentum and pseudorapidity within . An indication of the polarization dependence on the event-by-event charge asymmetry is observed at the level, suggesting a possible contribution to the polarization from the axial current induced by the initial magnetic field.
1 More- Received 13 May 2018
DOI:https://doi.org/10.1103/PhysRevC.98.014910
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