'Hubble Telescope' of nuclear physics will attempt to create primordial matter
COLLEGE PARK, Maryland, June 13, 2000 -- Physicists in Long Island, New York have just started what many researchers consider to be one of the most important experiments yet envisioned in modern science. Striving to gain a deeper understanding of the nature of matter, these physicists, at Brookhaven National Laboratory, have begun their efforts to create a long-lost soup of particles called the "quark-gluon plasma."
These efforts are taking place at a new Brookhaven machine known as the Relativistic Heavy Ion Collider (RHIC). Smashing together the cores of heavy atoms such as gold at near-light speed, researchers at RHIC are aiming to produce a state of matter that scientists think last existed briefly after the Big Bang, when the universe was much hotter and denser than it is today.
To learn more about what RHIC plans to achieve, Inside Science News Service asked nuclear physicists both connected with the experiments and independent of them about the new facility. Here is what they said.
"By means of extraordinarily high energy nuclear collisions, RHIC will act as a giant pressure cooker," says Brookhaven physicist Tom Ludlam, "producing temperatures and densities tens of thousands of times greater than exist now even at the centers of stars."
"This in itself is a worthy achievement, since we make advances in science by exploring the frontiers of possibility," adds Columbia University's William Zajc, who is also the spokesperson for the PHENIX Collaboration, one of the large experiments being planned for RHIC.
"The goal of RHIC is to recreate the conditions of the universe when it was only one millionth of a second old," explains Joe Kapusta, a theoretical high energy nuclear physicist at the University of Minnesota.
In this fraction of a second after the universe began, scientists believe that an exotic substance, called a "quark-gluon plasma," could exist. Quarks and gluons are the objects that make up the material out of which most of our world is constructed -- particles such as protons, neutrons, and atomic nuclei. A "quark-gluon" plasma is nothing more than a soup of individual quarks and gluons.
However, in the present universe, quarks are never found by themselves in ordinary matter. They come in packages of twos and threes -- and they are always held together by gluons.
By smashing together sufficiently dense bunches of heavy nuclei at high enough energies, scientists expect that the nuclei will dissolve into the coveted soup of free quarks and gluons -- which can potentially tell us not only about yesterday's universe, but the matter that we observe today.
Previous accelerator facilities at Brookhaven and elsewhere have been unable to create the quark-gluon plasma, at least in unambiguous terms, since they are only able to collide heavy nuclei at much lower energies. Recent experimental results at Europe's CERN facility have provided signs of an exotic form of nuclear matter, but no one could tell for sure if it was a quark-gluon plasma. "While many results remain provocative, the fact is that not a single property of the quark-gluon plasma state, if formed, could be directly measured thus far," says Miklos Gyulassy, a theorist at Columbia.
Producing collisions 10 times more powerful than those at CERN, "RHIC will solve this problem by sheer brute force," says Gyulassy.
"Discovering the quark-gluon plasma will be like a murder trial without a smoking gun," says Xin-Nian Wang of Lawrence Berkeley Lab. "It has to be a conviction beyond a reasonable doubt. We have to convince ourselves that the signals we see are caused only by the formation of the quark-gluon plasma and nothing else."
The collisions will be studied with four of the most advanced detectors for high energy particles yet designed. Named BRAHMS, PHENIX, PHOBOS, and STAR, these devices have been designed and built by scientific collaborations involving nearly 100 universities and laboratories worldwide.
"It is a nice example demonstrating that science has no borders," says Itzhak Tserruya of the Weizmann Institute of Technology, who leads the Israeli team working on the PHENIX detector.
Physicists expect that RHIC will shed new light on the theory of quarks and gluons, known as quantum chromodynamics, or QCD for short. QCD is a very accurate theory, but many of its details remain to be filled in.
Nuclear physicists are uniformly positive about the new facility.
"RHIC will be as revolutionary to the understanding of nuclear physics and strong interactions as the Hubble telescope was to astronomy," says Columbia's Gyulassy.
"Why should we care?" Joe Kapusta of the University of Minnesota asks rhetorically. "Anyone who struggles to understand the world wants to know 'What's out there?' and 'Where did we come from?' Mankind now has the ability to figuratively go back 12 billion years to within that one microsecond of when it all began."
From the Inside Science news service of the American Institute of Physics and American Physical Society
Contact information for outside experts:
Miklos Gyulassy, Columbia University
212-854-8152
gyulassy@nt3.phys.columbia.edu
Joseph Kapusta, University of Minnesota
612-624-0506
kapusta@physics.spa.umn.edu
Xin-Nian Wang, Lawrence Berkeley National Laboratory
510-486-5239
xnwang@lbl.gov
For the scientists affiliated with Brookhaven, please contact Karen McNulty 631-344-8350, kmcnulty@bnl.gov; Mona Rowe 631-344-5056, mrowe@bnl.gov; or call 631-344-2345.
Brookhaven news release at http://www.pubaf.bnl.gov/pr/bnlpr060800.html