Keay Davidson, Chronicle Science Writer
Particle physicists are on the brink of a fabulous new discovery about the birth of the universe.
There's just one catch: They're not sure what it is. It could be the same discovery they've sought for two decades -- an eerie entity called the "quark-gluon plasma," the hypothetical mother of all cosmic matter. Or it could be something radically different, something so strange they can't even precisely define it.
The confusion stems from experiments on the eastern edge of Long Island, at an "atom smasher" big enough to be seen from outer space. There, at the Brookhaven National Laboratory, physicists collide gold ions traveling at almost the speed of light. The resulting collisions briefly generate a temperature hundreds of millions of times higher than the surface of the sun.
In that flash of primordial heat, they hope to reproduce the conditions that existed microseconds after the birth of the universe in the Big Bang, 14 billion years ago. Within this "Little Bang," as some call it, the fierce heat, extreme density and unbelievable pressure -- akin to more than 100 sun-size stars resting on your fingernail -- should "melt" ordinary matter into its primal building blocks: quarks and the particles that bind them, gluons.
Ever since early experiments at Lawrence Berkeley National Laboratory 1n 1984, physicists using Brookhaven's Relativistic Heavy Ion Collider (RHIC) and others in Europe have tried to create such a "quark-gluon plasma" within particle accelerators.
But the effort has proved more difficult than many expected. In recent years, the research has generated considerable dispute over the interpretation of results.
Last week, almost 700 quark-gluon seekers gathered at the Oakland Marriott for a week of debate and self-scrutiny. To a lay outsider who stumbled into the giant meeting hall, where speakers waved laser pointers at PowerPoint projections of data charts, the meeting might have resembled a gathering of comptrollers scrutinizing supply-demand curves.
"Tremendous progress has been made over the past three years, and a staggering volume of new data have been recorded," a leading quark researcher, Miklos Gyulassy of Columbia University, told The Chronicle. "There is great excitement that a large number of new phenomena have in fact been discovered. These are discoveries of the exploration kind, just like what the Mars rover is now making on the red planet.
"Many never-before-seen pictures of a new world have been recorded in both cases, but no one is yet sure just what they all mean," he said.
With luck, future historians might record the Oakland conference as one of those glorious moments of confusion that dot the history of science, moments followed by a sudden "paradigm shift" that revolutionizes our view of reality. A parallel might be the geological congresses of the early and mid- 1960s. Back then, Earth scientists excitedly reported new evidence for hypothetical phenomena such as continental drift. At the time, speculation ran rife on the true cause of continental drift: Was it because continents are truly drifting atop geological plates, or because Earth itself is expanding like a balloon?
The turning point came in American Geophysical Union meetings of 1966 and 1967, where, somehow, a consensus emerged: Continents really do drift, and their drift is explained by "plate tectonics" on a nonexpanding Earth.
For particle physicists, their magic moment hasn't come yet. But it's getting close, many think.
"If you want a proof (for quark-gluon plasma) based entirely on experimental facts, we are not yet there entirely," said Hans-Georg Ritter, a Lawrence Berkeley physicist who helped pioneer the research in the early 1980s. For now, the best evidence is convincing only if one accepts theoretical models based on certain unproven assumptions. A more aggressive view is taken by Gyulassy, who thinks the evidence for quark-gluon plasma is overwhelming and has worked hard to convince his colleagues of this. It's been an uphill battle, though, because the data are so complex and are subject to so many different interpretations.
"I will try to convince more of the many skeptics in the audience," Gyulassy assured The Chronicle before his speech to the conference.
According to the latest cosmological theory and observations, the Big Bang occurred about 14 billion years ago. In the extremely hot, dense conditions of the first microseconds of the universe, quarks and gluons flew about madly.
Quickly thereafter -- unimaginably faster than the blink of an eye -- the quarks cooled and formed into the first atomic nuclei. These proto-atoms gradually merged into molecules, then larger clumps of matter -- the seeds of the first galaxies.
Particle physicists sometimes bless newly discovered particles with offbeat names. For example, there are six types of quarks: up, down, charm, strange, top and bottom.
An extremely odd property of quarks is that they are bound together by a strong nuclear force that grows stronger -- not weaker -- the farther quarks are separated. It's like a dog on an elastic chain that must tug harder to escape the farther it moves away from its owner. For this reason, quarks have been locked inside atomic nuclei for billions of years, unable to escape.
With a few possible exceptions. For one thing: Physicists suspect that quark-gluon plasmas might be fizzing away within the extremely dense cores of neutron stars, collapsed stars that are made mainly of neutrons. On a neutron star, a teaspoon of matter would weigh many tons.
The other exception is that according to the theory of quantum chromodynamics, which explains quark interactions, high-speed collisions of heavy ions such as gold or lead inside particle accelerators should briefly mimic conditions within the Big Bang, breeding a transient quark-gluon plasma that would last less than 0.00000000000000000000001 second.
How long will it take physicists to decide what they've actually discovered, if anything? Xin-Nian Wang, a theorist at Lawrence Berkeley, said it will take no more than five to 10 more years of research. "I would bet my money on that," he said.
Sam Aronson, head of the physics department at Brookhaven, said: "Either way, (Brookhaven's heavy ion collider) has discovered a new form of matter. It remains to be seen if it is the predicted quark-gluon plasma or something different."
Gyulassy said: "So much new data have been taken (from accelerators) with so many interesting, previously unseen phenomena that the community is a bit overwhelmed. There has not been enough (data for physicists) to converge to a consensus on the broader implications of the data.
"This is why international conferences of the size in Oakland are so important. It gives the whole (quark-gluon physics) community a chance to mull over and think about the broader issues at hand.
"There is no end to this wonderful world of experimental
discovery and mental constructions and reconstructions of realities
as new facts become known," Gyulassy said. "That is why
we physicists have more fun than most people."