Seminar in Hadronic Physics

Soft and Hard Probes of Topological Properties in Relativistic Heavy-Ion Collisions

Shuzhe Shi

McGill University

In relativistic heavy-ion collision experiments, a new phase of matter - the QCD Plasma - is created. In such QCD Plasma the color degrees of freedom, e.g. quarks and gluons, are deconfined and the chiral symmetry is restored. This talk contains two parts focusing on both soft (particles with transverse momentum p_T<2 GeV) and hard (p_T>10 GeV) probes of the QCD Plasma, especially its topological properties.

On one hand, we perform a quantitative, precise study of the Chiral Magnetic Effect (CME), which reflects the topological charge transition. 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. We developed 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 systematically investigate the dependence of the CME signal to a series of theoretical inputs and associated uncertainties.

On the other hand, a systematic analysis of jet quenching observables is performed, based on the CUJET3.1 and CIBJET simulation frameworks to probe the chromo-magnetic degree of freedom. The CUJET3.1 framework consistently combines viscous hydrodynamic fields predicted by smooth VISHNU2+1 and the DGLV jet energy loss theory generalized to sQGMP fluids with color structure including both electric and magnetic components. Based on a global, quantitative comparison with a comprehensive set of experimental data, we find that recent correlation data favor a temperature dependent color composition including bleached chromo-electric components, i.e. quark and gluon, and an emergent chromo-magnetic degrees of freedom. Furthermore, a comprehensive dynamical framework - CIBJET - is developed to calculate, on an event-by-event basis, the dependence of correlations between soft and hard azimuthal flow angle harmonics on the color composition of near-perfect QCD fluids.