# Ultra-Relativistic Heavy-Ion Physics Recent Results and a Future Perspective.

Harris J.W.

Relazione generale
I - Fisica nucleare e subnucleare
Aula A101 - Mercoledì 13 h 14:30 - 15:30
Collisions of ultra-relativistic heavy nuclei at the Large Hadron Collider (LHC) at CERN and the Relativistic Heavy-Ion Collider (RHIC) in the US create energy densities where nuclear matter melts into a quark-gluon plasma (QGP). Thousands of particles and anti-particles are created in a single event with temperatures reaching $T \sim 2 \times 10^{12}$ K, expected only within the first microseconds after the Big Bang. Normal hadrons cannot exist at these temperatures. The QGP is observed to flow easily, with extremely low viscosity approaching that of a nearly perfect liquid. New results have extended the study of the QGP to higher temperatures, smaller systems, and use of penetrating probes. Measurements of very energetic jets, large transverse momentum particles, and heavy flavors indicate a very dense and highly interacting system that is opaque to energetic probes. I will present a motivation for physics in this field, an overview and interpretation of results, and elucidate the "big questions" remaining to be answered. I will then present a perspective on how to pursue answers and elucidate further properties of the high-density QCD matter these collisions create.