Brookhaven Nuclear Physics

Historically, nuclear physicists have studied the structure, characteristics, and behavior of the atomic nucleus and the nature of the nuclear force. More recently, the study of nuclear matter under a variety of extreme conditions of temperature and energy density has become a major focus in this field. Today, the search for a never-before-seen form of hot, dense nuclear matter known as quark-gluon plasma, at Brookhaven’s Relativistic Heavy Ion Collider (RHIC), is the Laboratory’s largest physics research activity.

Photo of the Relativistic Heavy Ion ColliderCommissioned in 2000, RHIC (shown at right) is the world’s newest and largest accelerator for nuclear physics research. It collides gold nuclei head-on at energies of 100 billion electron volts per proton or neutron. These energetic collisions replicate, on a tiny scale, the hot, dense conditions thought to have existed immediately following the “Big Bang” that is believed to have created the universe. Under these conditions, it is predicted that quarks and gluons are liberated from within nucleons to form the hot, dense quark-gluon plasma.

At the Quark Matter 2004 conference, RHIC collaborations presented new evidence that gold-ion collisions in RHIC appear to be producing an extremely hot, dense form of matter with some properties predicted for quark-gluon plasma, but others that were unexpected. Data already in hand and additional data now being collected will allow the characteristics of this fascinating new form of matter to be explored in detail in RHIC experiments.

RHIC also serves as the world’s first and only collider of polarized protons for “spin physics.” In 2001 and again in 2003, RHIC was employed to investigate what quark and gluon substructure is responsible for the “spin,” or intrinsic angular momentum, of protons. Initial results have been generating great interest among physicists, who, from these experiments, hope to gain a more complete understanding of the spin structure of matter and the strong nuclear force that holds the quark and gluon components of protons together.

The polarized proton experiments at RHIC are successfully proceeding in a special partnership with RIKEN, the Japanese Institute of Physical and Chemical Research, through the RIKEN-BNL Research Center, along with many other collaborating institutions around the world.

> High Energy Physics

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Last Modified: January 4, 2006