Vorticity and hydrodynamic helicity in heavy-ion collisions in the hadron-string dynamics model

The hydrodynamic helicity separation effect in noncentral heavy-ion collisions is investigated using the hadron-string dynamics (HSD) model. Computer simulations are done to calculate velocity and hydrodynamic helicity on a mesh in a small volume around the center of the reaction. The time dependence of hydrodynamic helicity is observed for various impact parameters and different calculation methods. Comparison with a similar earlier work is carried out. A new quantity related to jet handedness is used to probe for $p$-odd effects in the final state.

Figure 1

weighted $y$ component of the vorticity ($\mathrm{c}/\mathrm{fm}$) averaged over all $x\text{−}z$ layers at $7.5\mathrm{fm}/\mathrm{c}$, impact parameter $b=8$ fm. Average value is $-4.4395\times {10}^{-2}\mathrm{c}/\mathrm{fm}$.

Figure 2

weighted $y$ component of the vorticity ($\mathrm{c}/\mathrm{fm}$) averaged over all $x\text{−}z$ layers at $10.5\mathrm{fm}/\mathrm{c}$, impact parameter $b=8$ fm. Average value is $-2.28\times {10}^{-2}\mathrm{c}/\mathrm{fm}$.

Figure 3

Weighted $y$ component of the vorticity ($\mathrm{c}/\mathrm{fm}$) averaged over all $x\text{−}z$ layers at $14\mathrm{fm}/\mathrm{c}$, impact parameter $b=8$ fm. Average value is $-1.2452\times {10}^{-2}\mathrm{c}/\mathrm{fm}$.

Figure 4

Weighted $y$ component of the vorticity ($\mathrm{c}/\mathrm{fm}$) averaged over all $x\text{−}z$ layers at $10.5\mathrm{fm}/\mathrm{c}$, impact parameter $b=0$ fm. Average value is $-1.2\times {10}^{-5}\mathrm{c}/\mathrm{fm}$.

Figure 5

Hydrodynamic helicity: $H_{\uparrow }$ and $H_{\downarrow }$, impact parameter $b=4\mathrm{fm}/\mathrm{c}$ (a) and $b=8\mathrm{fm}/\mathrm{c}$ (b).

Figure 6

Results for new derivative formulas parameter $b=4\mathrm{fm}/\mathrm{c}$.

Figure 7

Integral values calculated for impact parameter $b=8$ fm.

Figure 8

Dependence of $\overline{\eta }$ on $1/\sqrt{N}$, for impact parameter $b=7$ fm. Octants 1, 3, 4, and 6.

Figure 9

Dependence of $\overline{\eta }$ on $1/\sqrt{N}$, for impact parameter $b=7$ fm. Octants 0, 2, 5, and 7.