Measurement of global polarization of ? hyperons in few-GeV heavy-ion collisions

The global polarization of ? hyperons along the total orbital angular momentum a relativistic heavy-ion collision is presented based on high statistics data samples collected in Au+Au collisions at sNN=2.4 GeV and Ag+Ag 2.55 with High-Acceptance Di-Electron Spectrometer (HADES) GSI, Darmstadt. This first measurement below strangeness production threshold nucleon-nucleon collisions. Results are reported as function centrality well hyperon's transverse (pT) rapidity (yCM) for range 0–40%. We observe strong dependence an increasing signal towards peripheral For mid-central (20 – 40%) magnitudes ?P??(%)=6.8±1.3(stat.)±2.1(syst.) ?P??(%)=6.2±0.4(stat.)±0.6(syst.) Ag+Ag, which largest values observed so far. observation thus provides continuation trend previously by STAR contrasts expectations from recent theoretical calculations predicting maximum region energies about 3 GeV. similar magnitude predicted 3D-fluid-dynamics UrQMD plus thermal vorticity model significantly above results AMPT model.