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

Abstract

Vorticity generated in heavy-ion collisions at energy of √ sNN = 39 GeV is studied. Simulations are performed within a model of the three-fluid dynamics. A peculiar structure consisting of two vortex rings is found: one ring in the target fragmentation region and another one in the projectile fragmentation region. These rings are also formed in central collisions. The matter rotation is opposite in this two rings. These vortex rings are already formed at the early stage of the collision together with primordial fragmentation regions. The average vorticity, responsible for the global polarization of the observed Λ andΛ, is also studied. In the semi-central collisions the average vorticity in the midrapidity region turns out to be more than an order of magnitude lower than the total one. The total vorticity is dominated by the contributions of the fragmentation regions and is produced because of asymmetry of the vortex rings in noncentral collisions. This suggests that in semi-central collisions the global polarization in the fragmentation regions should be at least an order of magnitude higher than that observed by the STAR collaboration in the midrapidity. This polarization should be asymmetrical in the reaction plain and correlate with the corresponding directed flow.

Polarization and Vorticity in the Quark–Gluon Plasma

“…Numerical calculations with transport-hybrid codes (96,99,102) also indicate a forward migration of vorticity, especially as the collision energy increases (99). Finally, hydrodynamic models predict much higher vorticity in the beam fragmentation region at both NICA (97, 146) and RHIC (92,147) energies. Exploring vorticity away from midrapidity in fixed-target experiments (discussed above) is relatively straightforward.…”

“…For particles emitted at forward rapidity, symmetry permits an average polarization projection alongn =b. In fact, so-called vortex rings or cyclones are predicted (100,147) at forward rapidity at RHIC (100) and NICA (97, 147) energies (4 GeV √ s NN 11 GeV) as well as at midrapidity in nonsymmetric systems (149). In this case,n p ×ẑ.…”

Probing vorticity structure in heavy-ion collisions by local Λ polarization

“…See Refs. [22,23,[31][32][33][34][35] for other calculations of the quadrupole structure of ω y . Figure 4 shows the distribution of ω ⊥ = (ω x , ω y ) as functions of x and y at two values of space-time rapidity η s = −1 and 1.…”

“…However, the local vorticity field has much richer information than the global one. In the numerical simulations [22,23,[31][32][33][34][35], it is observed that ω y shows a quadrupole pattern in the reaction plane (xz plane): ω y is negative and positive in the regions xz > 0 and xz < 0, respectively. This novel structure is mainly due to the fact that the transverse velocity |v x | decreases with rapidity or ∂|v x |/∂|z| < 0 [33].…”

Quantized vortices in pionic superfluid

“…In HIC this corresponds to the hadronic beams [15] (being most close to the discussed liquid helium example) and jets [16]. One may also consider the rings appearance and evolution in the case of HIC, where 3-fluid hydro [19] or kinetic model [20] can be applied.…”