Signatures of Chiral Magnetic Effect in the Collisions of Isobars

TL;DR

This paper develops advanced theoretical tools to detect the Chiral Magnetic Effect in isobar nuclear collisions, proposing a background-robust observable and providing quantitative predictions to aid experimental discovery.

Contribution

It introduces a novel isobar subtraction strategy and a new observable for CME detection, enhancing the analysis of relativistic nuclear collision experiments.

Findings

Predicted the ratio of isobar-subtracted correlators for CME signatures.

Proposed an isobar subtraction method to improve background removal.

Provided quantitative predictions for CME signals in isobar collisions.

Abstract

Quantum anomaly is a fundamental feature of chiral fermions. In chiral materials the microscopic anomaly leads to nontrivial macroscopic transport processes such as the Chiral Magnetic Effect (CME), which has been in the spotlight lately across disciplines of physics. The quark-gluon plasma (QGP) created in relativistic nuclear collisions provides the unique example of a chiral material consisting of intrinsically relativistic chiral fermions. Potential discovery of CME in QGP is of utmost significance, with extensive experimental searches carried out over the past decade. A decisive new collider experiment, dedicated to detecting CME in the collisions of isobars, was performed in 2018 with analysis now underway. In this paper, we develop the state-of-the-art theoretical tool for describing CME phenomenon in these collisions and propose an appropriate isobar subtraction strategy for best background removal. Based on that, we make quantitative predictions for signatures of CME in the collisions of isobars. A new and robust observable that is independent of axial charge uncertainty -- the ratio between isobar-subtracted $\gamma-$ and $\delta-$ correlators, is found to be $- ( 0.41 \pm 0.27 )$ for event-plane measurement and $ - ( 0.90 \pm 0.45 )$ for reaction-plane measurement.