Numerical evidence of chiral magnetic effect in lattice gauge theory

Abstract

The chiral magnetic effect is the generation of electric current of quarks along external magnetic field in the background of topologically nontrivial gluon fields. There is a recent evidence that this effect is observed by the STAR Collaboration in heavy ion collisions at RHIC. In our paper we study qualitative signatures of the chiral magnetic effect using quenched lattice simulations. We find indications that the electric current is indeed enhanced in the direction of the magnetic field both in equilibrium configurations of the quantum gluon fields and in a smooth gluon background with nonzero topological charge. In the confinement phase the magnetic field enhances the local fluctuations of both the electric charge and chiral charge densities. In the deconfinement phase the effects of the magnetic field become smaller, possibly due to thermal screening. Using a simple model of a fireball we obtain a good agreement between our data and experimental results of the STAR Collaboration.Comment: 14 pages, 14 figures, uses RevTeX 4.0; revision: references and comments added, figures corrected, published versio

Local violation effects and thermalization in QCD: Views from quantum field theory and holography

“…in drastic contrast with low energy relation (17). It poses no problem for the correlation function (16) when the physical dilaton saturates the negative sign in eq.…”

“…At the same time the positive physical mass m 2 η > 0 for the η meson requires the positive sign for the topological susceptibility (17), see the original reference [39] for a thorough discussion. Therefore, there must be a contact contribution to χ, which is not related to any propagating physical degrees of freedom, and it must have a "wrong sign" (in comparison with (18) representing the conventional dispersive contribution) to saturate the positive sign for topological susceptibility (17). In different words, it must be a non-dispersive contribution to χ which is not associated with any asymptotical physical states in conventional dispersion relations.…”

“…The effect was coined as "chiral magnetic effect" (CME) [14,15]. Formula (1) has been also derived a numerous number of times using varies techniques such as: effective lagrangian approach developed in [23]; explicit mode's summation [24]; direct lattice computations [17,18]. In addition, the effect has been studied in holographic models of QCD [25,26].…”

“…There is a number of different manifestations of this local P and CP violation, see [14][15][16][17][18] and many additional references therein. In particular, in the presence of an external magnetic field B or in case of the rotating system with angular velocity Ω there will be induced electric current directed along B or Ω correspondingly, resulting in separation of charges along those directions as mentioned above.…”

Quark Matter in a Strong Magnetic Background

“…For example, at the energy scale for RHIC it is found eB max ≈ 5m 2 π ; for collisions at the LHC energy scale eB max ≈ 15m 2 π . In this case, it has been argued that the nontrivial topological structure of thermal QCD, namely the excitation of the strong sphalerons [103], locally changes the chirality of quarks; this is reflected to eventby-event charge separation, a phenomenon which is dubbed Chiral Magnetic Effect (CME) [39,41,42]. The possibility that the CME is observed in heavy ion collision experiments has motivated the study of strong interactions in presence of a chirality imbalance and a magnetic background, see [42,104,105,106,107,108] and references therein.…”