Utilization of Event Shape in Search of the Chiral Magnetic Effect in Heavy-ion Collisions

TL;DR

This paper explores a new event-shape engineering method to enhance the detection of the chiral magnetic effect in heavy-ion collisions by reducing flow-related background, using simulations with AMPT and EBE-AVFD models.

Contribution

It introduces a novel approach to isolate CME signals by projecting correlators onto low-flow events, improving sensitivity and statistical significance in heavy-ion collision experiments.

Findings

Event-shape engineering reduces flow background in CME observables.

The method enhances the statistical significance of CME detection.

Simulations show improved sensitivity in Au+Au, Ru+Ru, and Zr+Zr collisions.

Abstract

The search for the chiral magnetic effect (CME) has been a subject of great interest in the field of high-energy heavy-ion collision physics, and various observables have been proposed to probe the CME. Experimental observables are often contaminated with background contributions arising from collective motions (specifically elliptic flow) of the collision system. We present a method study of event-shape engineering (ESE) that projects the CME-sensitive $\gamma_{112}$ correlator and its variations ($\gamma_{132}$ and $\gamma_{123}$) to a class of events with minimal flow. We discuss the realization of the zero-flow mode, the sensitivity on the CME signal, and the corresponding statistical significance for Au+Au, Ru+Ru, and Zr+Zr collisions at $\sqrt{s_{\rm NN}} = 200$ GeV with a multiphase transport (AMPT) model, as well as a new event generator, Event-By-Event Anomalous-Viscous Fluid Dynamics (EBE-AVFD).