Scaling properties of background- and chiral-magnetically-driven charge separation: Implications for detecting and characterizing the chiral magnetic effect in heavy-ion collisions.

The scaling properties of the Δγ correlator, inferred from the Anomalous Viscous Fluid Dynamics (AVFD) model, are used to investigate a possible chiral-magnetically-driven (CME) charge separation in p+Au, d+Au, Ru+Ru, Zr+Zr, and Au+Au collisions at 200 GeV, and in p+Pb (5.02 TeV) and Pb+Pb collisions at 2.76 and 5.02 TeV. The results indicate that the values of the quotient Δγ/v₂ with the elliptic flow coefficient v₂ for p+Au, d+Au, p+Pb, and Pb+Pb collisions, scale as 1/N_ch consistent with background-driven charge separation. By contrast, the Δγ/v₂ values for Ru+Ru, Zr+Zr, and Au+Au collisions show scaling violations consistent with the presence of background plus a CME-driven contribution. Quantifying this CME-driven component indicates that in mid-central collisions, the fraction of the measured Δγ/v₂ attributable to the CME is approximately 27 % for Au+Au and roughly a factor of two smaller for Ru+Ru and Zr+Zr, which show similar magnitudes.