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تسجيل مستخدم جديدGlobal $Lambda$-hyperon polarization in Au+Au collisions at $sqrt{s_mathrm{NN}}=3$ GeV
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Global hyperon polarization, $overline{P}_mathrm{H}$, in Au+Au collisions over a large range of collision energy, $sqrt{s_mathrm{NN}}$, has recently been measured and successfully reproduced by hydrodynamic and transport models with intense fluid vorticity of the Quark-Gluon Plasma (QGP). While na{i}ve extrapolation of data trends suggests a large $overline{P}_mathrm{H}$ as the collision energy is reduced, the behavior of $overline{P}_mathrm{H}$ at small $sqrt{s_mathrm{NN}}<7.7$ GeV is unknown. Operating the STAR experiment in fixed-target mode, we have measured the polarization of $Lambda$ hyperons along the direction of global angular momentum in Au+Au collisions at $sqrt{s_mathrm{NN}}=3$ GeV. The observation of substantial polarization of $4.91pm0.81(rm stat.)pm0.15(rm syst.)$% in these collisions may require a reexamination of the viscosity of any fluid created in the collision, the thermalization timescale of rotational modes, and of hadronic mechanisms to produce global polarization.
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