Charge-dependent flow induced by magnetic and electric fields in heavy ion collisions

Abstract

We investigate the charge-dependent flow induced by magnetic and electric fields in heavy-ion collisions. We simulate the evolution of the expanding cooling droplet of strongly coupled plasma hydrodynamically, using the iEBE-VISHNU framework, and add the magnetic and electric fields as well as the electric currents they generate in a perturbative fashion. We confirm the previously reported effect of the electromagnetically induced currents [Gursoy et al., Phys. Rev. C 89, 054905 (2014)], that is a charge-odd directed flow Δv1 that is odd in rapidity, noting that it is induced by magnetic fields (à laFaraday and Lorentz) and by electric fields (the Coulomb field from the charged spectators). In addition, we find a charge-odd Δv3 that is also odd in rapidity and that has a similar physical origin. We furthermore show that the electric field produced by the net charge density of the plasma drives rapidity-even charge-dependent contributions to the radial flow ⟨pT⟩ and the elliptic flow Δv2. Although their magnitudes are comparable to the charge-odd Δv1 and Δv3, they have a different physical origin, namely the Coulomb forces within the plasma.