Back to the beginning - exploring quark-gluon matter

9 February 2000

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Experiments looking at collisions between lead nuclei, and collisions of lead with gold, have together gathered compelling evidence for a new state of matter - the quark-gluon plasma. Seven experiments at CERN, the European Laboratory for Particle Physics, have reported their work in a special seminar this week. The aim of the experiments, in which lead nuclei were accelerated to high energies, was to create extreme densities in matter to break down the strong force that normally locks quarks within protons and neutrons, the more familiar constituents of nuclei. At such high densities, theory implies that matter should form a quark-gluon plasma - a "soup" of quarks and gluons of the kind that would have existed before the quarks and gluons clumped together as the universe cooled down. In this image from the experiment code-named NA49, hundreds of particle tracks emanate from the "little bang" created in a collision of lead nuclei. (For further information, more images and animations, see CERN's Press Release.)

Credit: CERN / NA49