Importance of isobar density distributions on the chiral magnetic effect search

TL;DR

This paper investigates how differences in isobar density distributions affect the search for the chiral magnetic effect in heavy-ion collisions, highlighting potential challenges in distinguishing the effect from background signals.

Contribution

It demonstrates that variations in isobar density distributions can significantly influence the expected signals and backgrounds in CME searches, complicating the interpretation of experimental results.

Findings

Isobar density differences can alter eccentricity and flow measurements.

Uncertainties in magnetic field differences impact CME detection.

Density distributions affect background and signal separation.

Abstract

Under the approximate chiral symmetry restoration, quark interactions with topological gluon fields in quantum chromodynamics can induce chirality imbalance and parity violation in local domains. An electric charge separation ({\sc cs}) could be generated along the direction of a strong magnetic field ({\bf B}), a phenomenon called the chiral magnetic effect ({\sc cme}). {\sc cs} measurements by azimuthal correlators are contaminated by a major background from elliptic flow anisotropy ($v_2$). Isobaric $^{96}_{44}$Ru+$^{96}_{44}$Ru and $^{96}_{40}$Zr+$^{96}_{40}$Zr collisions have been proposed to identify the {\sc cme} (expected to differ between the two systems) out of the background (expected to be almost the same). We show, by using the density-functional calculated proton and neutron distributions, that these expectations may not hold as originally anticipated, because the two systems may have sizable differences in eccentricity and $v_2$ and because their difference in {\bf B} may suffer from large uncertainties.