# Sensitivity analysis of the chiral magnetic effect observables using a multiphase transport model

## TL;DR

This paper investigates the sensitivity of the new $R_{\\Psi_{m}}$ observable to the chiral magnetic effect (CME) using a multiphase transport model, demonstrating its potential to distinguish CME signals from background effects.

## Contribution

It introduces a method to calculate $R_{\Psi_{m}}$ in a transport model and compares its response to traditional observables, highlighting its effectiveness in detecting small CME signals.

## Key findings

- $R_{\Psi_{2}}$ shape is flat without CME and concave with CME.
- $R_{\Psi_{2}}$ is more sensitive to small CME signals than traditional observables.
- The shape of $R_{\Psi_{2}}$ can help identify CME presence despite background effects.

## Abstract

Because the traditional observable of charge-dependent azimuthal correlator $\gamma$ contains both contributions from the chiral magnetic effect (CME) and its background, a new observable of $R_{\Psi_{m}}$ has been recently proposed which is expected to be able to distinguish the CME from the background. In this study, we apply two methods to calculate $R_{\Psi_{m}}$ using a multiphase transport model without or with introducing a percentage of CME-induced charge separation. We demonstrate that the shape of final $R_{\Psi_{2}}$ distribution is flat for the case without the CME, but concave for that with an amount of the CME, because the initial CME signal survives from strong final state interactions. By comparing the responses of $R_{\Psi_{2}}$ and $\gamma$ to the strength of the initial CME, we observe that two observables show different nonlinear sensitivities to the CME. We find that the shape of $R_{\Psi_{2}}$ has an advantage in measuring a small amount of the CME, although it requires large event statistics.