Nonequilibrium axial charge production in expanding glasma flux tubes

Naoto Tanji

doi:10.1103/physrevd.98.014025

Abstract

Axial charge production at the early stage of heavy-ion collisions is investigated within the framework of real-time lattice simulations at leading order in QCD coupling. Starting from color glass condensate initial conditions, the time evolution of quantum quark fields under classical color gauge fields is computed on a lattice in longitudinally expanding geometry. We consider simple color charge distributions in Lorentz contracted nuclei that realize flux tube-like configurations of color fields carrying nonzero topological charge after a collision. By employing the Wilson fermion extended to the longitudinally expanding geometry, we demonstrate the realization of the axial anomaly on the real-time lattice.

Highlights

In relativistic heavy-ion collisions, CP-violating configurations of color gauge fields can be generated locally either by gauge field dynamics at the instant of a collision or sphaleron transitions at later times [1,2,3,4,5]
As a simple test for the real-time lattice computations of the axial charge production in the expanding geometry, we first consider the uniform glasma configuration introduced in Sec
In this paper we have investigated the axial charge production in the early stage of heavy-ion collisions by using the real-time lattice simulation method for classical gauge fields and quantum quark fields

Summary

Introduction

In relativistic heavy-ion collisions, CP-violating configurations of color gauge fields can be generated locally either by gauge field dynamics at the instant of a collision or sphaleron transitions at later times [1,2,3,4,5] Quarks interacting with such gauge fields induce the imbalance of axial charge due to the quantum phenomenon of axial anomaly. In presence of a strong U(1) magnetic field, which may be generated in off-central collisions, the axial charge asymmetry can be converted to a flow of electric current along the magnetic field [6] This phenomenon is called chiral magnetic effect (CME) [7,8,9]. The observation of the CME in heavy-ion collisions still remains inconclusive due to large backgrounds [14]

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Conclusion