Charge-dependent directed flows in heavy-ion collisions by Boltzmann-Maxwell equations

TL;DR

This study calculates charge-dependent directed flows in heavy-ion collisions using coupled Boltzmann-Maxwell equations, revealing different electromagnetic and medium effects on pions and protons.

Contribution

It introduces a self-consistent numerical approach to analyze charge-dependent flow differences in heavy-ion collisions.

Findings

$v_1$ for pions and protons are negative at positive mid rapidity.

$ riangle v_1$ for protons mainly from pressure gradients.

$ riangle v_1$ for pions primarily from electromagnetic fields.

Abstract

We have calculated the directed flow $v_{1}$ and charge-dependent directed flow $\Delta v_{1}$ for pions and protons in Au+Au collisions at $\sqrt{s_{NN}}=200$GeV by solving the coupled Boltzmann-Maxwell equations self-consistently. Our numerical results show that $v_{1}$ for pions and protons are all negative in the positive mid rapidity region and have similar behavior and magnitude. In contrast we find a quite different behavior in $\Delta v_{1}$ for pions and protons. The difference lies in that $\Delta v_{1}$ for protons mainly comes from pressure gradients of the medium, while the dominant contribution to $\Delta v_{1}$ for pions is from electromagnetic fields. Our results indicate that the effect of the electric field will slightly exceed that of the magnetic and lead to a small negative slope of $\Delta v_{1}$ for pions