# Probe Chiral Magnetic Effect with Signed Balance Function

## TL;DR

This paper proposes two new observables based on signed balance functions to detect the Chiral Magnetic Effect in heavy ion collisions, demonstrating their effectiveness through simulations including various backgrounds.

## Contribution

The paper introduces a novel pair of observables that are sensitive to CME signals and resilient against certain backgrounds, validated with realistic collision models.

## Key findings

- Both observables respond positively to CME signals.
- They show limited responses to resonance flow and spin alignment backgrounds.
- Simulations with AMPT and AVFD models confirm their effectiveness.

## Abstract

In this paper a pair of observables are proposed as alternative ways, by examining the fluctuation of net momentum-ordering of charged pairs, to study the charge separation induced by the Chiral Magnetic Effect (CME) in relativistic heavy ion collisions. They are, the out-of-plane to in-plane ratio of fluctuation of the difference between signed balance functions measured in pair's rest frame, and the ratio of it to similar measurement made in the laboratory frame. Both observables have been studied with simulations including flow-related backgrounds, and for the first time, backgrounds that are related to resonance's global spin alignment. The two observables have similar positive responses to signal, and opposite, limited responses to identifiable backgrounds arising from resonance flow and spin alignment. Both observables have also been tested with two realistic models, namely, a multi-phase transport (AMPT) model and the anomalous-viscous fluid dynamics (AVFD) model. These two observables, when cross examined, will provide useful insights in the study of CME-induced charge separation.