Title:“Tallying Gauge Field Topology with Chiral Magnetic Effect”

Abstract: Gauge fields provide the fundamental interactions in the Standard Model of particle physics. Gauge field configurations with nontrivial topological windings are known to play crucial roles in many important phenomena, from matter-antimatter asymmetry of today’s universe to the permanent quark confinement. Their presence is however elusive for direct detection in experiments. In this talk, I will discuss how recent measurements of the so-called chiral magnetic effect (CME) in heavy ion collisions can be used for counting the topological windings of the non-Abelian gauge fields in the Quantum Chromodynamics (QCD). The CME is a nontrivial macroscopic transport process arising from microscopic quantum anomaly of underlying chiral fermions in a chiral material (e.g. Dirac or Weyl semimetal), which has been in the spotlight lately across disciplines of physics. Potential discovery of CME in heavy ion collisions is of utmost significance, with extensive experimental searches carried out over the past decade. Some twelve years after the first hint of a possible CME signal, excitement is mounting toward finding it at long last from a decisive isobar collision experiment. I will briefly recount aspects of this effort and discuss how an state-of-the-art theoretical tool, developed through the Beam Energy Scan Theory (BEST) Collaboration, has allowed us to quantitatively extract, for the first time, the initial topological windings Qw from the CME experimental data, revealing a universal scaling relation between Qw and the particle multiplicity produced in the corresponding collision events.

Host: Vladimir Skokov