NPA Zoom Seminar, Jean-Francois Paquet, Duke, “Constraining the Viscosities of QCD with Relativistic Heavy Ion Collisions”

Fluids can be characterized by macroscopic properties such as viscosities or an equation of state. While the macroscopic properties of everyday fluids are determined by the electromagnetic interaction, an ensemble of fluids encountered in astrophysics and nuclear physics is dominated by the strong nuclear interaction. Relativistic collisions of heavy nuclei, performed at the Large Hadron Collider and the Relativistic Heavy Ion Collider, concentrate sufficient energy at the point of impact to produce a strongly-coupled plasma of deconfined nuclear matter. The viscosity of this nuclear plasma can be studied with a systematic analysis of data from heavy ion collision experiments. In this work, I will review how the shear and bulk viscosities of deconfined nuclear matter can be related to the species and momentum distribution of hadrons produced in heavy ion collisions. I will discuss recent results by the JETSCAPE Collaboration [arXiv:2010.03928], which used Bayesian inference to provide systematic constraints on the shear and bulk viscosities of a deconfined nuclear plasma at temperatures of ~150-300 MeV and zero net baryon density. I will also present the status of photon production in heavy ion collisions. I will discuss how photons could be used to provide stronger constraints on the viscosities of QCD, and validate our general understanding of the many-body physics of heavy ion collisions.
Zoom info: https://yale.zoom.us/j/93903961284?pwd=empxRWhzdkY5SXpuQ2U2NmR1aWlpZz09