Directed flow in relativistic resistive magneto-hydrodynamic expansion for symmetric and asymmetric collision systems

TL;DR

This paper develops a relativistic resistive magneto-hydrodynamic model to study electromagnetic effects on directed flow in high-energy heavy-ion collisions, revealing conductivity's significant impact especially in asymmetric systems.

Contribution

It introduces a new (3+1)-D resistive MHD simulation with realistic electromagnetic initial conditions for symmetric and asymmetric collisions.

Findings

Finite electrical conductivity significantly affects directed flow in asymmetric collisions.

Energy transfer via Ohmic conduction flattens pressure gradients, reducing directed flow growth.

Asymmetry in colliding nuclei causes notable electromagnetic dissipation effects.

Abstract

We construct a dynamical model for high-energy heavy-ion collision based on the relativistic resistive magneto-hydrodynamic framework. Using our newly developed (3+1)-dimensional relativistic resistive magneto-hydrodynamics code, we investigate magneto-hydrodynamic expansion in symmetric and asymmetric collision systems as a first application to high-energy heavy-ion collisions. As a realistic initial condition for electromagnetic fields, we consider the solutions of the Maxwell equations with the source term of point charged particles moving in the direction of the beam axis, including finite constant electrical conductivity of the medium. We evaluate the directed flow in the symmetric and asymmetric collisions at RHIC energy. We find a significant effect of finite electrical conductivity on the directed flow in the asymmetric collision system. We confirm that a certain amount of energy transfer by dissipation associated with Ohmic conduction occurs in the asymmetric collision system because of asymmetry of the electric field produced by two different colliding nuclei. Because this energy transfer makes the pressure gradient of the medium flatter, the growth of directed flow decreases.