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 together.
Recently Jean Cleymans of Cape Town University in South Africa and Krzysztof Redlich of Wroclaw University in Poland proposed that the data from the different experiments can be described in a universal way, despite being obtained under widely differing conditions (Phys. Rev. Lett. 1998 81 5284). Their results add to the debate of whether collisions at different accelerators have any universal properties, independent of both the type of particles involved and the collision energy used. If such features are confirmed this may substantiate theories that predict a novel mechanism of particle creation and the existence of the quark-gluon plasma.
In the March issue of Physics World, Johann Rafelski of the University of Arizona and Berndt Müller of Duke University in the US review the latest research into quark-gluon plasmas.