Systematic study of the Chiral Magnetic Effect with the AVFD model at LHC energies

TL;DR

This study uses the AVFD model to analyze the Chiral Magnetic Effect in heavy-ion collisions at LHC energies, identifying parameters that match experimental correlator data and suggesting a CME signal in Pb--Pb but not in Xe--Xe collisions.

Contribution

It provides a systematic parametrization of correlators related to the CME, linking them to axial current density and local charge conservation, and compares model predictions with experimental data.

Findings

Xe--Xe collisions are consistent with background only.

Pb--Pb collisions require a non-zero CME signal.

The model accurately describes the centrality dependence of correlators.

Abstract

We present a systematic study of the correlators used experimentally to probe the Chiral Magnetic Effect (CME) using the Anomalous Viscous Fluid Dynamics (AVFD) model in Pb--Pb and Xe--Xe collisions at LHC energies. We find a parametrization that describes the dependence of these correlators on the value of the axial current density ($n_5/\mathrm{s}$), which dictates the CME signal, and on the parameter that governs the background in these measurements i.e., the percentage of local charge conservation (LCC) within an event. This allows to deduce the values of $n_5/\mathrm{s}$ and the LCC percentage that provide a quantitative description of the centrality dependence of the experimental measurements. We find that the results in Xe--Xe collisions at $\sqrt{s_{\mathrm{NN}}} = 5.44$~TeV are consistent with a background only scenario. On the other hand, the model needs a significant non-zero value of $n_5/\mathrm{s}$ to match the measurements in Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02$~TeV.