By Peter Weiss
From Washington, D.C., at the American Physical Society’s April Meeting 2001
It’s easy to see when water boils, but it’s much harder to discern the roiling transitions of matter and space in particle accelerators.
As it turns out, little bits of space may have reached a coveted cosmic boil years ago in some of the world’s highest-energy particle collision–only researchers didn’t know it.
John G. Cramer of the University of Washington in Seattle presented a new analysis of the conditions created last year by powerful collisions between gold ions in the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory in Upton, N.Y. “There are some surprises that come out of this,” he says.
In millions of fiery impacts last year at RHIC, and during accelerator experiments in Europe in the past 2 decades, physicists have sought to create tiny blazing clouds of protoatomic stuff called the quark-gluon plasma. In such clouds, the fundamental constituents of matter–quarks and gluons–roam freely instead of being bound as protons and neutrons.
Theorists have proposed that RHIC’s gold-gold collisions should heat up a tiny bit of space so much that the region would undergo a phase transition–akin to melting or boiling–that would produce the plasma (SN: 2/26/00, p. 135). Cramer reports evidence of the fireballs’ behaviors that suggests the presence of a plasma.
In their analysis of data from one of RHIC’s four detectors, Cramer and his coworkers have found indications, for instance, that the fireballs at RHIC expand to only about the same size as those produced by European collisions at much lower energy. Cramer concludes from this and other comparisons that the phase transition for the plasma may unwittingly have been achieved years earlier.
“It’s quite possible,” accedes Brookhaven’s Thomas W. Ludlam. To confirm the claim, he cautions, scientists need to find yet more signatures of the quark-gluon plasma.
