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RHIC and the new state of matter

The Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory is an international scientific research facility that began operation in 2000, following 10 years of development and construction. Thousands of physicists from around the world use RHIC to study what the universe may have looked like in the first few moments after its creation. They do this by colliding ions at very high energies to recreate the hot, dense conditions of the early universe, and studying what comes out. While many RHIC collisions will produce interesting results, a rare few are expected to create something even more special: a new form of matter. Actually, it's not new to the universe, just to human eyes. It's thought to have existed ten millionths of a second after the Big Bang at the dawn of the universe (15 to 20 billion years ago). It may also exist in the cores of very dense stars called neutron stars. This form of matter is called quark-gluon plasma or QGP. What physicists learn from these collisions may help us understand more about why the physical world works the way it does, from the smallest subatomic particles, to the largest stars.

At the moment, experimental physicists have constructed four large experiments at RHIC, with more planned for the future. The two largest experiments, STAR and PHENIX, have more than 500 members each. The two smaller ones, BRAHMS and PHOBOS, have dozens of members.

RHIC's ion beams travel at 99.995% of the speed of light (186,000 miles per second, or 300,000,000 meters per second) on a collision course and, for a fleeting instant when they collide, heat the matter to more than a billion times the temperature of the sun. In so doing, thousands of particles are created, each leaving a telltale trace electrical charge along its path as it passes through the experimental detectors. The beam is usually composed of heavy gold ions: in 20 years of running, RHIC will use less than one gram of gold for its research program.

The STAR experiment
STAR is an acronym for Solenoidal Tracker At RTracker refers to STAR's ability to reconstruct (or "track") particle trajectories over a large distance, providing particle identification and momentum determination capabilities.

As big as a house and weighting 1,200 tons, the STAR detector records collision events. The main tracking device in STAR is a large three dimensional "camera" called a Time Projection Chamber (TPC). It has 137,000 active sensors leading to collision “images” of about the same size as an image recorded by a hand-held digital camera like the one you might have at home. Hundreds of such images are recorded per second. It takes up to six minutes for powerful computers to reconstruct a single event, that is, re-trace the path taken by each particle in the detector. To face the enormous challenge of reconstructing such vast amount of potential “QGP pictures” , the computing resources and strategy evolved toward a distributed computing model known as Grid-computing. With this technology, the reconstruction and analysis of such events can be seamlessly distributed to remotely located students and collaborators all over the world with the computing resources needed to analyze them accessible as a “virtual cluster”.

STAR-Events:

Links:
STAR-Homepage
STAR Lite (Education and Outreach)
STAR Live Events
Max-Planck-Institut für Physik, Munich

Special Thanks to: 
Dr. Jerome Lauret (BNL) & Valeri Fine (BNL)