Tracing Electromagnetic Response through Charge Splitting of Directed Flow in the Quark-Gluon Plasma
Abstract
Experimentally observed charge splitting of directed flow, Δv1≡ v1(h+)−v1(h-), exhibits both a sign reversal at midrapidity and the amplitude change from Au+Au collisions at √(sNN)=200 GeV to Pb+Pb at √(sNN)=5.02 TeV. We study this behavior within a unified (3+1)-dimensional viscous hydrodynamic model that incorporates an electromagnetic source term in the bulk evolution of the quark-gluon plasma (QGP) and an electromagnetic correction to the Cooper--Frye particlization. The beam-energy dependence of Δv1 can be described by varying the effective electrical conductivity between RHIC and LHC energies, with values consistent with the conductivity scale indicated by lattice-QCD calculations. We find that the sign reversal emerges from the competition between momentum distortions induced by the electric and magnetic field which is controlled by the conductivity during the QGP evolution. The model further predicts the mass-dependent charge splittings for identified pions, kaons, and protons, providing further constraints on their respective relaxation times and the corresponding electromagnetic interaction. These results establish the charge splitting of directed flow as a quantitative probe of the electromagnetic response and the space-time evolution of the QGP.
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BibTeX
@misc{panda2026tracing,
title = {{Tracing Electromagnetic Response through Charge Splitting of Directed Flow in the Quark-Gluon Plasma}},
author = {Ankit Kumar Panda and Zhu Meng and Long-Gang Pang and Xin-Nian Wang},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.38363},
eprint = {2610.38363},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.38363},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Tracing Electromagnetic Response through Charge Splitting of Directed Flow in the Quark-Gluon Plasma
AU - Ankit Kumar Panda
AU - Zhu Meng
AU - Long-Gang Pang
AU - Xin-Nian Wang
PY - 2026
DA - 2026/10/28
PB - arXiv
DO - 10.48550/arxiv.2610.38363
UR - https://arxiv.org/abs/2610.38363
AB - Experimentally observed charge splitting of directed flow, Δv_1≡ v_1(h^+)−v_1(h^-), exhibits both a sign reversal at midrapidity and the amplitude change from Au+Au collisions at √(s_NN)=200 GeV to Pb+Pb at √(s_NN)=5.02 TeV. We study this behavior within a unified (3+1)-dimensional viscous hydrodynamic model that incorporates an electromagnetic source term in the bulk evolution of the quark-gluon plasma (QGP) and an electromagnetic correction to the Cooper--Frye particlization. The beam-energy dependence of Δv_1 can be described by varying the effective electrical conductivity between RHIC and LHC energies, with values consistent with the conductivity scale indicated by lattice-QCD calculations. We find that the sign reversal emerges from the competition between momentum distortions induced by the electric and magnetic field which is controlled by the conductivity during the QGP evolution. The model further predicts the mass-dependent charge splittings for identified pions, kaons, and protons, providing further constraints on their respective relaxation times and the corresponding electromagnetic interaction. These results establish the charge splitting of directed flow as a quantitative probe of the electromagnetic response and the space-time evolution of the QGP.
ER -