Is the Chiral Magnetic Effect fast enough?

TL;DR

This paper investigates the real-time development of the chiral magnetic effect in strongly coupled gauge theories using holography, revealing how magnetic field lifetime impacts the effect's buildup in heavy ion collisions.

Contribution

It provides a holographic analysis of the out-of-equilibrium evolution of the chiral magnetic effect, including magnetic field backreaction and parameter matching to QCD.

Findings

At small magnetic fields, pressure builds faster than the chiral magnetic current.

At strong magnetic fields, the chiral magnetic current builds faster than pressure.

Equilibration time is approximately 0.35 fm/c at relevant plasma temperatures.

Abstract

It depends: While we find within holography that the lifetime of the magnetic field for collider energies like the ones achieved at RHIC is long enough to build up the chiral magnetic current, the lifetime of the magnetic field at LHC seems to be too short. We study the real time evolution of the chiral magnetic effect out-of-equilibrium in strongly coupled holographic gauge theories. We consider the backreaction of the magnetic field onto the geometry and monitor pressure and chiral magnetic current. Our findings show that generically at small magnetic field the pressure builds up faster than the chiral magnetic current whereas at strong magnetic field the opposite is true. At large charge we also find that equilibration is delayed significantly due to long lived oscillations. We also match the parameters of our model to QCD parameters and draw lessons of possible relevance to the realization of the chiral magnetic effect in heavy ion collisions. In particular, we find an equilibration time of about $\sim0.35$ fm/c in presence of the chiral anomaly for plasma temperatures of order $T\sim300-400$ MeV.