# Out-of-Equilibrium Chiral Magnetic Effect from Chiral Kinetic Theory

## TL;DR

This paper investigates the chiral magnetic effect (CME) during the out-of-equilibrium pre-thermal stage in heavy ion collisions using chiral kinetic theory, highlighting its sensitivity to magnetic field dynamics and initial conditions.

## Contribution

It provides the first phenomenological study of CME-induced charge separation in a non-equilibrium setting with chiral kinetic theory.

## Key findings

- CME charge separation during pre-thermal stage is modest.
- Charge separation is highly sensitive to magnetic field time dependence.
- Initial quark momentum spectrum and relaxation time influence CME effects.

## Abstract

Recently there has been significant interest in the macroscopic manifestation of chiral anomaly in many-body systems of chiral fermions. A notable example is the Chiral Magnetic Effect (CME). Enthusiastic efforts have been made to search for the CME in the quark-gluon plasma created in heavy ion collisions. A crucial challenge is that the extremely strong magnetic field in such collisions may last only for a brief moment and the CME current may have to occur at so early a stage that the quark-gluon matter is still far from thermal equilibrium. This thus requires modeling of the CME in an out-of-equilibrium setting. With the recently developed theoretical tool of chiral kinetic theory, we make a first phenomenological study of the CME-induced charge separation during the pre-thermal stage in heavy ion collisions. The effect is found to be very sensitive to the time dependence of the magnetic field and also influenced by the initial quark momentum spectrum as well as the relaxation time of the system evolution toward thermal equilibrium. Within the present approach, such pre-thermal charge separation is found to be modest.