Global polarization of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi mathvariant="normal">Λ</mml:mi></mml:math> hyperons in Au + Au collisions at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msqrt><mml:msub><mml:mi>s</mml:mi><mml:mrow><mml:mi>N</mml:mi><mml:mi>N</mml:mi></mml:mrow></mml:msub></mml:msqrt><mml:mo>=</mml:mo><mml:mn>200</mml:mn></mml:mrow></mml:math> GeV

Global polarization of $\mathrm{\ensuremath{\Lambda}}$ hyperons has been measured to be of the order of a few tenths of a percentage in Au+Au collisions at $\sqrt{{s}_{{}_{NN}}}$ = 200 GeV, with no significant difference between $\mathrm{\ensuremath{\Lambda}}$ and $\overline{\mathrm{\ensuremath{\Lambda}}}$. These new results reveal the collision energy dependence of the global polarization together with the results previously observed at $\sqrt{{s}_{{}_{NN}}}$ = 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 ${\ensuremath{\eta}}^{H}$ within $|{\ensuremath{\eta}}^{H}|&lt;1$. An indication of the polarization dependence on the event-by-event charge asymmetry is observed at the $2\ensuremath{\sigma}$ level, suggesting a possible contribution to the polarization from the axial current induced by the initial magnetic field.