Heavy Ion Physics

In the strong interaction sector of the SM, there is the challenge to understand the properties of hadronic matter: the matter that comprises almost the entire visible universe, from protons and neutrons to extremely dense stellar objects. The basic building blocks of hadronic matter at its most fundamental level are quarks and gluons, which are described by the theory of Quantum Chromodynamics (QCD). Quarks and gluons are not observed in isolation, they are bound inside the hadrons, as a consequence of a property of QCD known as confinement. Understanding the confinement of quarks and gluons is one of the greatest challenges of contemporary physics.

Asymptotic freedom is another prominent property of QCD: the strength of the interactions among quarks and gluons decrease when they come close together. As a consequence, it was suggested that matter at densities much higher than the density of normal nuclei consists of a soup of freely moving quarks and gluons, the so-called quark-gluon plasma (QGP).  Such a state of matter is conjectured to have existed at the birth of the Universe, and the best way to recreate QGP in the laboratory is through high energy collisions of heavy ions (HI), large nuclei stripped off their electron content. High energy HI collisions can produce systems where large amounts of energy are concentrated in a small volume, expecting to recreate small samples of this primordial matter.