Abstract
Quarks – the tiny building blocks that make up protons, neutrons and other hadrons – are normally locked deep inside larger nuclear particles. But a new state of matter made up of freely moving quarks and gluons, known as the "quark-gluon plasma", is thought to have existed just moments after the big bang. Experiments at several accelerator laboratories around the world are attempting to recreate that moment by colliding large atomic nuclei with each other at velocities close to the speed of light. The nuclear matter that is created from the different types of collision and at different energies allows theorists to test their predictions against experimental data.