Scientists working in Europe claimed yesterday to have achieved a key goal of modern physics, the re-creation of a form of matter that briefly filled the universe 10 millionths of a second after its birth.
Other physicists questioned the announcement, saying they want to see more evidence. "My initial reaction is somewhere between skepticism and doubt," said Thomas Cohen, a nuclear physicist at the University of Maryland.
The European Laboratory for Particle Physics, called CERN, said in a news release that one of its teams had found "compelling evidence" that it had created a quark-gluon plasma, a hot soup of what are believed to be the fundamental constituents of matter.
Standard theories hold that the universe consisted of such a plasma shortly after the Big Bang, the fireball of matter that occurred 15 billion years ago and gradually cooled to create the cosmos.
Quarks are the particles that make up ordinary matter, including protons and neutrons. Gluons are force-carrying particles that bind quarks together.
In Geneva the director-general of CERN, Luciano Maiani, sounded more cautious yesterday than the earlier written statement.
"This is a step in research," he said. " This is not the last word." CERN officials said more work was needed to approximate the conditions of the infant universe.
About 500 scientists from 20 countries have been working at CERN since 1994 in an effort to create the plasma. In their experiments, they've smashed the nuclei of lead atoms together at nearly the speed of light. This generates temperatures 100,000 times hotter than those found in the center of the sun and densities 10 times greater than those found in an atomic nucleus.
But the plasma, if it forms at all, can't be seen directly. It quickly cools back into ordinary matter. Its existence can be inferred only by analyzing the debris thrown off by the collisions.
No one knows for certain, Cohen said, what kind of debris to look for.
"If you ask me the question do you think they have evidence they have created a quark-gluon plasma, than the answer would probably be no," he said.
A team of scientists at the Brookhaven National Laboratory in Upton, N.Y., plans to try to create the plasma at a new facility, the Relativistic Heavy Ion Collider, where work is expected to begin this spring. Brookhaven will study matter at higher temperatures and densities than CERN, in effect looking at the state of the universe at earlier times.
CERN plans to shut down its plasma research until 2005, when it will complete construction of a new atom-smasher, the Large Hadron Collider, that will be even more powerful than the Brookhaven machine.
Scott Friedman, an astrophysicist at the Johns Hopkins University, said these high-energy experiments could help confirm current views of how the galaxies, stars and planets formed. "It puts the theories of astrophysics on a firmer footing than they otherwise would have been," he said.
Maiani, an Italian physics professor, said the study of fundamental questions in physics has led to the creation of the laser, the transistor and computer.
Reuters contributed to this article.