Search

We present the global polarization of Lambda and Anti-Lambda hyperons in Au+Au collisions at √s = 7.682, 11.454, 14.546, 19.564, 26.994, and 38.996GeV. The global polarization is a measure of the alignment of final state particle spin with total collision system angular momentum, and is given as a percentage. Averaging over √s the values of the polarization for these particles is P(Lambda) = 1.08 ± 0.15(stat) ± 0.11(sys)% and P(Anti-Lambda) = 1.38 ± 0.30(stat) ± 0.13(sys)%. This represents the first non-trivial measurement of this type. The data was recorded by the STAR collaboration. Positive polarization represents positive vorticity in the fireball. We also present a method for extracting this vorticity from the data while accounting for polarized particle feed down. The extracted vorticity is ω = (9 ± 1) 1021 s-1 with a systematic scaling uncertainty of 2, primarily due to uncertainty in the temperature. Such a vorticity far exceeds any other known vorticity lending a new superlative to the QGP: “the most vortical fluid”.