Hyperons polarization in heavy-ion collisions

Abstract

Abstract. We study the structure of vorticity and hydrodynamic helicity fields in peripheral heavy-ion collisions using the kinetic Quark-Gluon Strings Model. The angular momentum which is a source of P-odd observables is preserved within this model with a good accuracy. We observe the formation of specific toroidal structures of vorticity field. Their existence is mirrored in the polarization of hyperons of the percent order. The observed qualitative energy dependence of polarization was predicted earlier and is quantified now.

Vortex rings in fragmentation regions in heavy-ion collisions at sNN=39 GeV

“…It was concluded that the observed rotational fluid has the largest vorticity, of the order of ∼10 22 s −1 , that ever existed in the universe. The measured polarization quantitatively agrees with the hydrodynamic [5,6] and kinetic [7][8][9][10] model calculations.…”

“…This enhancement at peripheral rapidities was illustrated in Ref. [8] at the example of Au+Au colli- * e-mail: Y.Ivanov@gsi.de sion at √ s N N = 5 GeV. Although not all models predict the polarization minimum at the midrapidity [14].…”

“…This type of the vorticity is directly relevant to the hadron polarization due to the chiral vortical effect [28] that was used in Refs. [7,8]. Another type of the vorticity is so-called thermal vorticity…”