Scientists who think they have come tantalizingly close to discovering a long-sought subatomic particle have decided to press ahead for another month rather than immediately leave the field — and a probable Nobel prize — to their main American rival.

When CERN, the European Laboratory for Particle Physics, halts experiments on the Large Electron-Positron collider, it will have to sit and watch for five years as the Fermi National Accelerator Laboratory in Batavia, Ill., has free rein to discover the so-called Higgs boson.

“It would be one of the greatest landmark achievements of physics,” said Chris Tully, a Princeton University professor who has been working on the search for the Higgs boson at CERN.

A ‘Specialized Craziness’

Scientists at CERN have recorded three subatomic collisions where they think they have seen “shadows” of the particle, theorized to be responsible for all mass — or weight — in the universe.

CERN decided Thursday to keep the Large Electron-Positron running through October, postponing for one month contracts to start the changeover to the Large Hadron Collider, which will take five years to bring online.

But it decided against a longer run, even though one extra month is unlikely to be enough to find the particle.

Being able to claim the “discovery” of the Higgs will be a feather in the cap of the successful laboratory.

“Mass is a very important property of matter, and we have nothing in our current theory that says even a word about it,” said Claude Detraz, one of two research directors at CERN.

“I’m sure history will consider it a major step in the understanding of matter,” even if “it sounds like a little specialized craziness — ‘Higgs boson, Higgs boson, Higgs boson.’”

A Fundamental Question

Tully said the mass of subatomic particles can make objects hard to break or fragile, determine whether they are a conducting metal or an insulator, even create their color.

“For us it’s one of the most fundamental questions we can ask, and that’s why we’ve spent our lives looking for this,” Tully said.

CERN has long planned to start Oct. 2 with construction to replace the LEP, the world’s largest nuclear accelerator, with the more powerful LHC, much desired by the scientific community.

The dilemma resulted from the Higgs-like signals detected as the CERN physicists — who come from all over the world — were pushing the LEP to its outside limits in its final months.

“We do have some strong evidence for this signature,” Tully told The Associated Press. But, he conceded, CERN is far from having enough occurrences to be able to claim “discovery” even if it makes more during October.

But, said Tully, in the give-and-take world of physics, that would “give” Fermilab even more of a boost in its own search, helping it to pinpoint where to look.

Judy Jackson, spokeswoman for Fermilab, said it was “a little premature” to speculate that the accelerator outside Chicago would benefit.

But, she conceded, Fermilab scientists were “watching with interest” to see what CERN decides.

Not only is Fermilab a rival for the Higgs discovery, it — like the U.S. government — also has a stake in seeing the Large Hadron Collider start up on time.

“The U.S. and in particular Fermilab are contributing major elements to the LHC construction,” Jackson said.

Washington is giving about a half billion dollars toward the European project. About one-third of the 7,000 scientists who will work on the LHC will be from the United States.

Worthy of the Nobel Prize

Originally CERN planned to put the LHC on top of the 11-year-old LEP inside its circular, 17-mile tunnel under the Swiss-French border area.

But the engineering problems were too difficult and the decision was made to remove the LEP and install the $1.8 billion LHC in its place.

CERN would encounter massive extra costs in delaying construction of the LHC and risk angering physicists who will have to defer their experiments they have long dreamed of starting in 2005.

Fermilab, which has been undergoing its own upgrade for four years, is due to start its Higgs experiments next spring on the refurbished Tevatron, which found another particle — the top quark — in 1996.

CERN has designed the LHC precisely to discover the Higgs particle, but Detraz said it will have plenty to do even if Fermilab wins the discovery race.

“When Christopher Columbus saw the coast, it was discovering America, but it was not studying America.”

The long-sought particle was named for British physicist Peter Higgs, who postulated its existence more than 30 years ago at the University of Edinburgh to explain how atoms — and everything else in the universe — have weight.

Without the particle, the basic physics theory — the “standard model” — was lacking a crucial element, because it fails to explain how other elements have mass.

The Higgs theory is that the usually invisible bosons create a field through which subatomic particles — such as quarks and electrons — pass.

The particles that find passing through the field to be slow going — like going through molasses — pick up more inertia, and mass. The ones that pass through easily remain lighter.

Detraz agreed that the discovery will likely win the Nobel Prize for physics, but he said the prize should really go to the person who can figure out who will be responsible for discovering the Higgs because so many scientists have contributed.

“Hundreds of people have dedicated their lives for years to the search,” he said.