Latest RHIC Results Make News Headlines at Quark Matter 2004
At the recent Quark Matter 2004 conference, new evidence
was presented that gold-ion collisions at the Relativistic Heavy Ion
Collider are producing an extremely dense form of matter — which may,
quite possibly, be the long-sought quark-gluon plasma. There was also
animated discussion about other intriguing RHIC results, including the
likelihood that RHIC’s experiments have detected the existence of an
“anti-pentaquark,” an exotic type of particle containing five quarks, and
may have uncovered signs of another dense form of matter called color
glass condensate.
by Karen McNulty Walsh
Dominating the agenda of Quark Matter 2004, presentations of analyses from recent runs of the four experiments at the Relativistic Heavy Ion Collider (RHIC) created quite a media buzz during the week-long, 17th international conference on ultra-relativistic nucleus-nucleus collisions. For this meeting, more than 600 nuclear physicists from around the world gathered this January in Oakland, California.
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A computer image of RHIC particle events generated by the STAR experiment. |
Located at Brookhaven Lab and funded primarily by the U.S. Department of Energy’s Office of Science, RHIC was built to collide gold ions at nearly the speed of light, to recreate hot, dense conditions that existed at the dawn of the universe. Under those conditions, quarks and gluons are expected to be free of the strong force which holds them confined within protons and neutrons within the atomic nucleus. Freed, they are expected to form a state of matter called quark-gluon plasma, which scientists think last existed a few microseconds after the Big Bang.
Studying the freed quarks and gluons within the plasma will help scientists develop an understanding of how matter evolved over time since the Big Bang. It will also provide more insight into the strong force, which is one of the four forces in nature and the short-range attraction responsible for holding the atomic nucleus together.
At the Quark Matter conference, new evidence was presented that gold-ion collisions at RHIC are producing an extremely dense form of matter — which may, quite possibly, be the long-sought quark-gluon plasma. There was also animated discussion about other intriguing RHIC results, including the likelihood that RHIC experiments have detected the existence of an exotic type of particle containing five quarks, and may have uncovered signs of another dense form of matter called color glass condensate. “We have intriguing results, but it may take some time to sort out their significance in relation to the search for quark-gluon plasma or other new discoveries,” says Sam Aronson, Chair of Brookhaven’s Physics Department and a collaborator on PHENIX, one of the two larger RHIC experiments.
As reporters covering Quark Matter discovered, however, not all those at the conference were quite so circumspect. After the first day of the conference, for instance, stories in the Oakland Tribune and The New York Times, respectively, quoted scientists who all but declared that discoveries of quark gluon plasma and color glass condensate have already been made.
