Helicity and vorticity in heavy-ion collisions at NICA energies

Abstract

Heavy-ion collisions at center-of-mass nucleon collision energies 4.5--11.5 GeV are analyzed within the PHSD transport model. Spectator nucleons are separated, and the transfer of the initial angular momentum of colliding nuclei to the fireball formed by participants is studied. The maximal angular momentum is carried by the fireball in gold-gold collisions with the impact parameter about 5 fm corresponding to centrality class 10--20\%. The obtained participant distributions were fluidized and the energy and baryon number densities, temperature, and velocity fields are obtained in the Landau frame. It is shown that the velocity field has dominantly Hubble-like transversal and longitudinal expansion with the vortical motion being only a small correction on top of it. The vorticity field is calculated and illustrated in detail. The formation of two oppositely-rotating vortex rings moving in opposite directions along the $z$ axis is demonstrated. Other characteristics of the vortical motion such as the Lamb vector field and the kinematic vorticity number are considered. The magnitude of the latter one is found to be smaller than that for the Poiseuille flow and close to the pure shear deformation corresponding to just a flattening of fluid cells. The field of hydrodynamic helicity, which is responsible for the axial vortex effect, is calculated. The separation of positive and negative helicities localized upper and lower semi-planes with respect to the reaction plane is shown. It is proved that the areas with various helicity signs can be probed by the selection of $\Lambda$ hyperons with positive and negative projections of their momenta orthogonal to the reaction plane.

22 pages, 23 figures. Figure labels are corrected, references added, figure labels are rescaled

References in corpus (13)

• Angular momentum conservation in heavy ion collisions at very high energy
• Quantum Anomalies in Dense Matter
• Chiral anomaly and local polarization effect from quantum kinetic approach
• Global $\Lambda$ Polarization in high energy collisions
• Lambda hyperon polarization in relativistic heavy ion collisions from the chiral kinetic approach
• Evolution of transverse flow and effective temperatures in the parton phase from a multi-phase transport model
• Chiral vortaic effect and neutron asymmetries at NICA
• Different space-time freeze-out picture -- an explanation of different $\Lambda$ and $\bar{\Lambda }$ polarization?
• Global $\Lambda$ polarization in moderately relativistic nuclear collisions
• Correlation between global polarization, angular momentum and flow in heavy-ion collisions
• Properties of the QGP created in heavy-ion collisions
• Global $\Lambda$ polarization in heavy-ion collisions at energies 2.4--7.7 GeV: Effect of Meson-Field Interaction
• Global polarization in heavy-ion collisions based on axial vortical effect

Cited by in corpus (10)

• Probing the holographic model of $\mathcal{N}=4$ SYM rotating quark-gluon plasma
• Anti-flow of Mesons in the High Baryon Density Region
• Examination of STAR fixed-target data on directed flow at $\sqrt{s_{NN}}=$ 3 and 4.5 GeV
• Hyperon global polarization in heavy-ion collisions at NICA energies. Feed-down effects and the role of ${\Sigma }^0$ hyperons
• Hyperon Production in Bi+Bi Collisions at NICA and Angular Dependence of Hyperon Spin Polarization
• Measurement of Kaon Directed Flow in Au+Au Collisions in the High Baryon Density Region
• Global $\Lambda$ polarization in heavy-ion collisions at high baryon density
• Hubble's Law in Heavy Ion Collisions
• The Static Heavy Quark-Antiquark Potential within String Theory in Arbitrary Stationary Backgrounds
• Helicity conservation in perfect electromagnetic and chiral fluids