Signatures of Chiral Magnetic Effect in the Collisions of Isobars

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 several branches 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 and extensive experimental searches have been carried out over the past decade. A decisive new collider experiment, dedicated for possibly detecting CME in the collisions of isobars, has been performed in 2018 with analysis underway. In this paper, we develop the necessary and state-of-the-art theoretical tool for describing CME phenomenon in these collisions and propose an appropriate isobar subtraction strategy for the best background removal. Based on that, we make quantitative predictions for signatures of CME in the collisions of isobars.

Investigation of Experimental Observables in Search of the Chiral Magnetic Effect in Heavy-ion Collisions in the STAR experiment

“…Potentially the δ correlator could also contain the CME signal as Eq. 5 suggests, which should be manifested in the ∆δ ratio between Ru+Ru and Zr+Zr [59]. Figure 5 depicts the EBE-AVFD results of δ OS(SS) (a) and ∆δ (b) as functions of n 5 /s for 30-40% isobaric collisions at √ s NN = 200 GeV.…”

“…We shall describe the toy model that undertakes simple Monte Carlo calculations, as well as the more realistic event generator, EBE-AVFD [57][58][59].…”

“…The EBE-AVFD model [57][58][59] is a comprehensive simulation framework that dynamically describes the CME in heavy-ion collisions. This state-of-the-art tool has been developed over the past few years as an important part of the efforts within the Beam Energy Scan Theory (BEST) Collaboration, aiming to address the needs of the ongoing experimental program at RHIC collision energies.…”

“…More discussions of the hydrodynamics equations and relevant details can be found in Refs. [57][58][59].…”

“…We shall uncover the relations among them. Section III describes the simple Monte Carlo calculations, as well as a more realistic event generator: Event-By-Event Anomalous-Viscous Fluid Dynamics (EBE-AVFD) [57][58][59]. These simulations are deployed in Sec.…”