Quantifying the chiral magnetic effect from anomalous-viscous fluid dynamics

Abstract

The Chiral Magnetic Effect (CME) is a macroscopic manifestation of fundamental chiral anomaly in a many-body system of chiral fermions, and emerges as anomalous transport current in the fluid dynamics framework. Experimental observation of CME is of great interest and has been reported in Dirac and Weyl semimetals. Significant efforts have also been made to look for CME in heavy ion collisions. Critically needed for such search, is the theoretical prediction for CME signal. In this paper we report a first quantitative modeling framework, the Anomalous Viscous Fluid Dynamics (AVFD), which computes the evolution of fermion currents on top of realistic bulk evolution in heavy ion collisions and simultaneously accounts for both anomalous and normal viscous transport effects. The AVFD allows a quantitative understanding of the generation and evolution of CME-induced charge separation during hydrodynamic stage as well as its dependence on theoretical ingredients. With reasonable estimates of key parameters, the AVFD simulations provide the first phenomenologically successful explanation of the measured signal in 200AGeV AuAu collisions.Introduction.-The importance of electricity for modern society cannot be overemphasized. From the physics point of view, lies at the heart of electricity is the conducting transport (of electric charge carriers). In normal materials, conducting transport generates an electric current J Q along the electric field E (or voltage) applied to the system. This can be described by the usual Ohm's law J Q = σ e E where the conductivity σ e arises from competition between "ordered" electric force and "disordered" thermal scatterings, henceforth involving dissipation and typically dependent upon specific dynamics of the system. More recently there have been significant interests, from both high energy and condensed matter physics communities, in a new category of anomalous chiral transport in quantum materials containing chiral fermions. A notable example is the Chiral Magnetic Effect (CME) [1-5] -the generation of an electric current J Q along the magnetic field B applied to the system, i.e. J Q = σ 5 B(1)

QCD phase diagram in chiral imbalance with self-consistent mean field approximation

“…[43], which uses three different regularization schemes to study the effects of chiral chemical potential. In relativistic heavy-ion collisions, the chiral chemical potential is estimated to be about 10~100 MeV [44][45][46]. As shown in Fig.…”

Experimental searches for the chiral magnetic effect in heavy-ion collisions

“…The measured γ magnitudes of the order of 10 −4 therefore agree with the predictions of the CME signal of the order of a 1 = 10 −2 in Refs. [28,45,46,47,48]. Meanwhile, other predictions [33,55] are significantly smaller.…”

“…The authors of Refs. [46,47,48] estimated the initial axial charge density in heavy ion collisions and applied it to their Anomalous Viscous Fluid Dynamics (AVFD) on top of a realistic hydrodynamic evolution. They found the CME signal to be also on the order of 10 −2 .…”

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].…”

“…All densities in panels (b)-(c) are taken at a time τ = 3 fm/c. The figure is adapted from[133,134].…”