Anomalous transport model study of chiral magnetic effects in heavy ion collisions

Using an anomalous transport model for massless quarks and antiquarks, we study the effect of a magnetic field on the elliptic flows of quarks and antiquarks in relativistic heavy ion collisions. With initial conditions from a blast wave model and assuming that the strong magnetic field produced in noncentral heavy ion collisions can last for a sufficiently long time, we obtain an appreciable electric quadrupole moment in the transverse plane of a heavy ion collision. The electric quadrupole moment subsequently leads to a splitting between the elliptic flows of quarks and antiquarks. The slope of the charge asymmetry dependence of the elliptic flow difference between positively and negatively charged particles is positive, which is expected from the chiral magnetic wave formed in the produced QGP and observed in experiments at the BNL Relativistic Heavy Ion Collider, only if the Lorentz force acting on the charged particles is neglected and the quark-antiquark scattering is assumed to be dominated by the chirality changing channel.

Figure 1

Effects of chiral kinetic motion (CKM) and chirality changing scattering between quark and antiquark (CCS) on the distribution of massless quarks and antiquarks in the transverse plane of a heavy ion collision with initial positive charge chemical potential $\mu >0$ and vanishing axial charge chemical potential ${\mu }_5=0$.

Figure 2

Elliptic flow of all kinetically freeze-out pions as a function of their transverse momentum for the three cases of chiral kinetic motion with Lorentz force and chirality changing scattering (CKM+LF+CCS), without chirality changing scattering (CKM+LF), and without Lorentz force (CKM+CCS). Experimental data (solid circles) are from Ref. [41].

Figure 3

Eccentricity difference between positively and negatively charged particles as a function of time for different scenarios of parton dynamics as in Fig. 2 when the total charge asymmetry of the quark matter is $A_{\pm }=0.16$.

Figure 4

Same as Fig. 3 for the elliptic flow difference $\mathrm{\Delta }{v}_2$ between negatively and positively charged particles.

Figure 5

Charge chemical potential $\mu /T$ distribution in the transverse plane $z=0$ at time $t=5$ fm/$c$ for events with charge asymmetry $A_{\pm }=0.16$ for the case of including chiral kinetic motion and chirality changing scattering but no Lorentz force.

Figure 6

Same as Fig. 5 for the axial charge ${\mu }_5/T$.

Figure 7

Elliptic flow difference $\mathrm{\Delta }{v}_2$ as a function of charge asymmetry $A_{\pm }$ for different scenarios of parton dynamics as in Fig. 2.