Magnetohydrodynamics and charged currents in heavy ion collisions

TL;DR

This paper investigates how magnetic fields in non-central heavy ion collisions induce charge-dependent currents, affecting the azimuthal distributions of charged hadrons, and proposes a method to detect these effects through rapidity correlations.

Contribution

It introduces a model of magnetic field-induced charged currents in heavy ion collisions and predicts observable charge-dependent directed flow signatures.

Findings

Charged currents induce a charge-dependent directed flow $v_1$.

The directed flow $v_1$ is odd in rapidity and charge exchange.

Correlations between $v_1$ at different rapidities can reveal magnetic effects.

Abstract

The hot QCD matter produced in any heavy ion collision with a nonzero impact parameter is produced within a strong magnetic field. We study the imprint the magnetic fields produced in non-central heavy ion collisions leave on the azimuthal distributions and correlations of the produced charged hadrons. The magnetic field is time-dependent and the medium is expanding, which leads to the induction of charged currents due to the combination of Faraday and Hall effects. We find that these currents result in a charge-dependent directed flow $v_1$ that is odd in rapidity and odd under charge exchange. It can be detected by measuring correlations between the directed flow of charged hadrons at different rapidities, $\langle v_1^\pm (y_1) v_1^\pm (y_2) \rangle$.