CHICAGO The powering down of Fermilab's Tevatron particle accelerator on Friday marked the end of a quarter-century of U.S. dominance in high-energy particle physics.
The Tevatron, which accelerates and collides protons and antiprotons in a four-mile-long underground ring, has been replaced by the Large Hadron Collider under the French-Swiss border, which began operating in March 2010.
Physicists at the U.S. lab will now turn to smaller, more focused projects -- such as building the most intense proton beam -- as they pass the high-energy physics baton to the European Organization for Nuclear Research's (CERN) bigger, better atom smasher.
"Nothing lasts forever at the edge of science," said Pier Oddone, director of the Fermi National Accelerator Laboratory (Fermilab) in Batavia, Illinois. "We need to move on to those aspects of physics where we can put our mark."
Oddone said Europe has outspent the United States by a factor of three, and the United States now has to be very clever and define very carefully how it uses its resources.
"I think we can maintain a leadership position in the world. We are going to not be where we were 30 years ago where we led in every domain of particle physics, but we are going to lead in a narrower domain," he said in a telephone interview.
The highest-profile project on that front is an effort to confirm the startling discovery last week at CERN of particles that move faster than the speed of light.
It now falls to scientists at Fermilab to confirm or disprove that as part of its MINOS experiment (Main Injector Neutrino Oscillation Search).
That will use Fermilab's Main Injector to hurl an intense beam of neutrinos 455 miles through the Earth to the Soudan Mine in northern Minnesota.
If it can be verified, it will turn modern physics on its head.
LACK OF FUNDING
In its near 26-year run, the Tevatron has taught many lessons about how to build and manage an accelerator of its size and complexity, and these have played a major role in the construction of the 16.7-mile LHC ring at CERN.
"We built this machine to discover how the world is put together," Oddone said.
"It was a very daring machine in its time."
Tevatron's shining achievement was the discovery in 1995 of the top quark, the heaviest elementary particle known to exist.
Though it is as heavy as an atom of gold, the top quark's mass is crammed into an area far smaller than a single proton.
"Many machines were built around the world with the mission of discovering the top quark. It was only at the highest energy here that we found it," Oddone said.
The building of the Tevatron made contributions to the U.S. economy by bolstering the fledgling industry for superconducting cable to meet the Tevatron's need for 150,000 pounds (68,000 kg) of superconducting wire.
And while scientists largely believe the machine has outlived its useful life, lack of funding was the final blow for the Tevatron after the U.S. Department of Energy decided not to spend the $35 million needed to extend the Tevatron's operation through 2014.
As a result, many top U.S. physicists will continue research at a remote operation center that Fermilab has set up for scientists to monitor experiments at CERN.
Others will relocate to Europe.
"We are whores to the machines. We will go to wherever the machines are to do our science," said Rob Roser, co-spokesman for CDF, one of the two detectors that used the Tevatron.
"I personally will move to Europe to work on the next machine because we haven't finished answering the questions we're after, and I still find them very interesting and compelling. We've made good progress, but we are not done yet."
While the Tevatron will no longer be running experiments, Fermilab scientists have not given up hope of making a major contribution to finding the Higgs boson -- thought to be the agent which turned mass into solid matter soon after the Big Bang that created the universe 13.7 billion years ago.
Fermilab engineers and physicists have been furiously smashing particles together in the past several months, recreating the primal chaos of flying matter a tiny fraction of a second after the Big Bang.
The hope is that they will have accumulated enough data before the Tevatron shutdown to establish if the elusive Higgs boson exists in its long-predicted form.
If the particle does exist, scientists say it is running out of places to hide.
"We have cornered the Higgs into this particular space. By the time we analyze all the data, if it is not there, we will be able to say it is not there," Oddone said.
If the answer is no, scientists around the globe will have to rethink the 40-year-old Standard Model of particle physics which describes how they believe the cosmos works.
But if it is found, it will be up to the larger collider at CERN to confirm it.
(Editing by Eric Beech)