Background evaluations for the chiral magnetic effect with normalized correlators using a multiphase transport model

The chiral magnetic effect (CME) induces an electric charge separation in a chiral medium along the magnetic field that is mostly produced by spectator protons in heavy-ion collisions. The experimental searches for the CME, based on the charge-dependent angular correlations (γ), however, have remained inconclusive, because the non-CME background contributions are not well understood. Experimentally, the γ correlators have been measured with respect to the second-order (Ψ${}_2$) and the third-order (Ψ${}_3$) symmetry planes, defined as γ${}_{112}$ and γ${}_{123}$, respectively. The expectation was that with a proper normalization, γ${}_{123}$ would provide a data-driven estimate for the background contributions in γ${}_{112}$. In this work, we calculate different harmonics of the γ correlators using a charge-conserving version of a multiphase transport (AMPT) model to examine the validity of the said assumption. We find that the pure-background AMPT simulations do not yield an equality in the normalized γ${}_{112}$ and γ${}_{123}$, quantified by κ${}_{112}$ and κ${}_{123}$, respectively. Furthermore, we test another correlator, γ${}_{132}$, within AMPT, and discuss the relation between different γ correlators.