Chiral Magnetic Effect in Isobaric Collisions from Anomalous-Viscous Fluid Dynamics (AVFD)

Abstract

The isobaric collision experiment at RHIC provides the unique opportunity to detect the possible signal of Chiral Magnetic Effect (CME) in heavy ion collisions. The idea is to contrast the correlation observables of the two colliding systems that supposedly have identical flow-driven background contributions while quite different CME signal contributions due to the 10% variation in their nuclear charge and thus magnetic field strength. With the recently developed quantitative simulation tool for computing CME signal, the Anomalous-Viscous Fluid Dynamics (AVFD), we demonstrate that a joint (multiplicity + elliptic-flow) event selection is crucial for this purpose. We further propose to use the absolute difference between RuRu and ZrZr events (after using identical event selection) for detecting CME signal and make predictions for the correlation observables.

Mapping the phases of quantum chromodynamics with beam energy scan

“…To address the difficulty in the experimental detection of CME signals, it is imperative to develop a quantitative modeling framework that simulates the anomalous chiral transport while accurately accounts for the realistic environment in heavy ion collisions. In the past few years a matured framework, called the Anomalous-Viscous Fluid Dynamics (AVFD), has been developed [133,134,338]. We note in passing that there have been phenomenological study of CME based on kinetic transport models as well [151,[339][340][341][342][343][344][345].…”

“…More recently this framework has been further developed into event-by-event simulations (EBE-AVFD) [338], which is the state-of-the-art tool for quantifying anomalous chiral transport in heavy ion collisions. The EBE-AVFD includes fluctuating initial conditions as well as a hadronic cascade stage via UrQMD after the hydrodynamic evolution which accounts for the influence of hadronic re-scatterings and resonance decays.…”

“…Sine the CME signal in the γ-correlator is expected to be rather small, this presents a serious problem which needs to be controlled. As shown in [338], this problem can be overcome by selecting events on both multiplicity and elliptic-flow. Event-by-event simulations [338] for both initial conditions and for the final state observables have demonstrated that the joint-multiplicity-ellipticity cut would be effective and sufficient for this purpose.…”

Signatures of Chiral Magnetic Effect in the Collisions of Isobars

“…It turns out that such assumption may not be entirely true. Recent simulations of initial geometry in these collisions suggest potential difference at a few percent level in their elliptic eccentricity (even within the same centrality class) due to uncertainty in the nucleon distributions in the isobar pair of nuclei [50,51]. This presents enough of concern which may complicate the supposedly "clean" comparison between the isobars at quantitative level, especially given the rather small CME signal.…”

“…This presents enough of concern which may complicate the supposedly "clean" comparison between the isobars at quantitative level, especially given the rather small CME signal. To address this important issue and to ensure a successful isobar contrast, we propose a new strategy for comparing the isobaric systems, namely to use a joint (multiplicity + elliptic flow) event selection method [51]. We demonstrate the effectiveness of this strategy with event-by-event simulations of initial conditions.…”