7 research outputs found
The Chiral Magnetic Effect in Heavy Ion Collisions From Hydrodynamic Simulations
The quark-gluon plasma created in heavy ion collisions is an exotic state of matter in which many unusual phenomena are manifested. One such phenomenon is the Chiral-Magnetic Effect (CME), wherein the powerful magnetic fields generated by colliding ions spin-polarize chiral quarks, causing a net transport effect in the direction of the fields. The CME predicts specific charge-dependent correlation observables, for which experimental evidence was reported, although the evidence is subject to background contamination. Isobaric collision experiments have been planned for 2018 at RHIC, which will study this effect by comparing 96Ru-96Ru and 96Zr-96Zr collisions. The two colliding systems are expected to have nearly identical bulk properties (including background contamination), yet about 10% difference in their magnetic fields due to different nuclear charges. This provides a unique opportunity to disentangle the CME observable and background effects. By simulating this effect using anomalous hydrodynamic simulations, we make a quantitative prediction for the CME-induced signal for several centralities in each of these two colliding systems. Our results suggest a significant enough difference in the signal to be experimentally detected- on the order of 15-20%
Anomalous Chiral Transport in Heavy Ion Collisions from Anomalous-Viscous Fluid Dynamics
Chiral anomaly is a fundamental aspect of quantum theories with chiral
fermions. How such microscopic anomaly manifests itself in a macroscopic
many-body system with chiral fermions, is a highly nontrivial question that has
recently attracted significant interest. As it turns out, unusual transport
currents can be induced by chiral anomaly under suitable conditions in such
systems, with the notable example of the Chiral Magnetic Effect (CME) where a
vector current (e.g. electric current) is generated along an external magnetic
field. A lot of efforts have been made to search for CME in heavy ion
collisions, by measuring the charge separation effect induced by the CME
transport. A crucial challenge in such effort, is the quantitative prediction
for the CME signal. In this paper, we develop the Anomalous-Viscous Fluid
Dynamics (AVFD) framework, which implements the anomalous fluid dynamics to
describe the evolution of fermion currents in QGP, on top of the neutral bulk
background described by the VISH2+1 hydrodynamic simulations for heavy ion
collisions. With this new tool, we quantitatively and systematically
investigate the dependence of the CME signal to a series of theoretical inputs
and associated uncertainties. With realistic estimates of initial conditions
and magnetic field lifetime, the predicted CME signal is quantitatively
consistent with measured change separation data in 200GeV Au-Au collisions.
Based on analysis of Au-Au collisions, we further make predictions for the CME
observable to be measured in the planned isobaric (Ru-Ru v.s. Zr-Zr ) collision
experiment, which could provide a most decisive test of the CME in heavy ion
collisions.Comment: 28 pages, 13 figures; published versio
Quantification of Chiral Magnetic Effect from Event-by-Event Anomalous-Viscous Fluid Mechanics
Chiral Magnetic Effect (CME) is the macroscopic manifestation of the
fundamental chiral anomaly in a many-body system of chiral fermions, and
emerges as anomalous transport current in hydrodynamic framework. Experimental
observation of CME is of great interest and significant efforts have been made
to look for its signals in heavy ion collisions. Encouraging evidence of
CME-induced charge separation has been reported from both RHIC and LHC, albeit
with ambiguity due to potential background contributions. Crucial for
addressing such issue, is the need of quantitative predictions for both CME
signal and the non-CME background consistently, with sophisticated modeling
tool. In this contribution we report a recently developed Anomalous Viscous
Fluid Dynamics (AVFD) framework, which simulates the evolution of fermion
currents in QGP on top of the data-validated VISHNU bulk hydro evolution. In
particular, this framework has been extended to event-by-event simulations with
proper implementation of known flow-driven background contributions. We report
quantitative results from such simulations and evaluate the implications for
interpretations of current experimental measurements. Finally we give our
prediction for the CME signal in upcoming isobaric collisions.Comment: 5 pages, 7 figures; plenary talk at CPOD 2017 conference, Stony Brook
University, Stony Brook, NY. arXiv admin note: substantial text overlap with
arXiv:1704.05531; text overlap with arXiv:1611.0458
Quantifying the Chiral Magnetic Effect from Anomalous-Viscous Fluid Dynamics
In this contribution we report a recently developed Anomalous-Viscous Fluid
Dynamics (AVFD) framework, which simulates the evolution of fermion currents in
QGP on top of the bulk expansion from data-validated VISHNU hydrodynamics. With
reasonable estimates of initial conditions and magnetic field lifetime, the
predicted CME signal is quantitatively consistent with change separation
measurements in 200GeV Au-Au collisions at RHIC. We further develop the
event-by-event AVFD simulations that allow direct evaluation of two-particle
correlations arising from CME signal as well as the non-CME backgrounds.
Finally we report predictions from AVFD simulations for the upcoming isobaric
(Ru-Ru v.s. Zr-Zr ) collisions that could provide the critical test of the CME
in heavy ion collisions.Comment: Contribution to the Proceedings of the XXVIth International
Conference on Ultrarelativistic Nucleus-Nucleus Collisions (Quark Matter
2017), Feb 5-11, Chicago, U.S.A. 4 pages, 6 figure
Lights illuminate surfaces superluminally
© 2016 IOP Publishing Ltd. When a light bulb is turned on, light moves away from it at speed c, by definition. When light from this bulb illuminates a surface, however, this illumination front is not constrained to move at speed c. A simple proof is given that this illumination front always moves faster than c. Generalized, when any compact light source itself varies, this information spreads across all of the surfaces it illuminates at speeds faster than light