Magnetohydrodynamics, charged currents and directed flow in heavy ion collisions

TL;DR

This paper investigates how strong magnetic fields in heavy ion collisions induce charge-dependent directed flow of charged hadrons through Faraday and Hall effects, providing a potential observable for experimental detection.

Contribution

It introduces a model for how time-dependent magnetic fields induce charge-dependent flow patterns in heavy ion collisions, highlighting a novel observable for experimental verification.

Findings

Magnetic fields induce charge-dependent directed flow v1 in heavy ion collisions.

The induced v1 is odd in rapidity and charge exchange.

Correlations between v1 at different rapidities can reveal magnetic field 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 that these fields 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 v1 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, $\langle v_1^\pm(y_1)v_1^\pm(y_2)\rangle$.