BATAVIA, Illinois — High-energy particle physicists around the world are collectively holding their breath waiting for the Large Hadron Collider to come online and start unlocking the most elusive secrets of the universe. It's as if time is standing still until their shiny new toy is ready to play with.
But not at Fermilab. Here, physicists are in the scientific equivalent of an all-out sprint, still clinging to the ever-thinning hope that before the LHC ramps up to full power, their own 28-year old particle collider, the Tevatron, will catch the coveted Higgs boson, a theoretical particle that is at the heart of the Standard Model of physics.
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"It's a worthy fight," said physicist Roy Schwitters of the University of Texas at Austin. "Their chances are certainly not zero, but they're not great."
The race for the Higgs boson is loaded with the history of competition between American and European particle physics, and symbolizes scientific prowess and national pride. For the United States, finding this particle would be the perfect final chapter to a book filled with major scientific achievements. Failing to find it would be the latest in a long string of missed opportunities and heartbreak.
The advantage in this rivalry has swung back and forth across the Atlantic for more than seven decades. The Tevatron, capable of generating a trillion electron volts (1 TeV), still reigns as the most powerful accelerator on Earth, and is performing better than ever. But somehow the impending swing feels more permanent, adding an extra weight to the already laden quest for the next great discovery.
The Standard Model unifies all the forces in the universe and explains why the symmetry believed to exist just after the Big Bang no longer exists, why matter is far more abundant than antimatter and why some particles have more mass than others. The Higgs boson is a remnant of that early symmetrical universe, and finding it would provide the strongest evidence yet for the Model.
As Europe's new machine approached its start up last year, physicists estimated it would be producing results by the end of 2009. The Higgs was thought to be one of its first potential big finds.
But a breakdown just days after the first beam circulated through the LHC in September 2008, and another In July, forced scientists to set back the collider's start to November. And it will happen at a slower pace than originally hoped, which means it will be even longer before it reaches its estimated maximum power of 7 TeV.
This has given Fermilab a reprieve, perhaps a year or more, to reach the finish line.
"That’s an important lease on life for them," said Schwitters. "I applaud what they are doing, trying to get as much science as they can before it is eclipsed."
Fermilab's Tevatron is running better, producing more particle collisions per second and generating results faster than ever. And in its waning moments of glory, its scientists aren't giving up on their aging machine, even if the rest of the world has.
The Tevatron lies beyond the Chicago suburbs, beneath a wind-ridden field that appears to have no purpose. From afar, the storied laboratory is marked solely by the administrative building, a strangely swooping structure rising from the plain, designed to capture the essence of a French cathedral. The rest of the campus is primarily a collection of low, boxy buildings that look completely utilitarian and mostly gray.
Standing in front of the nondescript building that houses the Tevatron's D-Zero detector with physicist Dmitri Denisov, it's hard not to be caught up in his optimism about the Higgs.
"We are lucky here at Fermilab because everything is pointing to the mass region of this particle which could be covered by the Tevatron," he said. "It's at the edges, but we think we could."
The Tevatron's four-mile long ring has a second detector, the CDF, and the intentional sibling rivalry between the two groups of scientists that work on the detectors has kept the pace of discovery high. They race each other to find new particles and nail down their characteristics, feed on each other's successes and confirm each other's findings.
Based on theory and work done so far at the Tevatron and other machines including the Large Electron-Positron Collider at CERN, the mass of the Higgs is expected to be between 114 and 185 GeV. In March, Fermilab announced it had ruled out another chunk of masses between 160 and 170 GeV.
"If really there is no Standard Model Higgs in the mass range which we expect it to be, if it is much heavier — and there are some theories which predict it much heavier — then of course it is a different story," Denisov said. "But if it's really around 200, 180 or 190 GeV, then we will be able to exclude it, or start to see the Higgs. And we are working for exclusion or discovery."
Even if all the work chipping away at the Higgs territory only ends up providing an easier cherry for the LHC to pick, it still amounts to an important scientific contribution. But as Denisov explains this, the look in his eyes reveals how he really feels: The Tevatron has got this one the bag.
"We know how to make discoveries," he said.
It is easy to root for the Tevatron, the former-champ-turned-underdog, and believe it can succeed. But at the same time, it's hard not to imagine its failure. And the thought of the Tevatron stumbling just inches away from the finish line is all the more heartbreaking in light of America's long history in particle physics, which was a painful struggle at times.
Europe and the United States have been vying to make discoveries since the birth of high-energy particle physics in 1930, when E.O. Lawrence of the University of California, Berkeley built the first cyclotron. That was a 4-inch circular device that used a magnetic field to accelerate protons to 80,000 electron-volts. Soon the American physicist was building bigger and bigger cyclotrons discovering many isotopes and winning a Nobel Prize along the way.
But the Europeans began building their own accelerators, and the race was on to split open the nucleus of an atom. It was close, but the University of Cambridge’s Cavendish Labs under Ernest Rutherford won.
At this point the United States veered away from theoretical pursuits toward more practical applications, guided by Lawrence's adept salesmanship.
"Lawrence was the first to see that cyclotrons could be used in medicine," said physicist Paul Halpern, author of the book Collider. "That was brilliant because then he began receiving grants to explore medical uses of the cyclotron, and that gave him a lot of money to build new equipment."
And when the Manhattan Project came along, Lawrence jumped on that train as well. His 184-inch cyclotron, which could push various particles to more than 100 million electron-volts, aided in the separation of uranium isotopes for use in the atomic bomb.
Soon the United States overtook Europe at the leading edge of high-energy physics, and big machines began to dominate the scene. In the 1950s and 1960s accelerators that could top a billion electron-volts dominated the scene: Lawrence Berkeley National Laboratory’s Bevatron, which discovered the antiproton, and Brookhaven National Laboratory’s Cosmotron.
"At Brookhaven, researchers developed ways of focusing beams very tightly and being able to improve what's called the luminosity, which is the chance of collisions," Halpern said. "And that was a great innovation."
The next big step was colliders: accelerators that, instead of aiming a particle beam at a fixed target, would smash opposing beams of particles into each other. In the 1970s, small colliders were built at CERN and Stanford Linear Accelerator Center, which detected mesons and leptons.
Bigger colliders were needed for the next discoveries. But Fermilab was in no rush to turn the newly minted Tevatron, the world's first superconducting accelerator, into a collider. Instead they focused on bringing it up to its goal of 1 TeV. Along the way, the Tevatron dealt a blow to CERN by exceeding 300 BeV, the target energy of the Super Proton Synchrotron, which was still being built.
But Europe would soon return the favor, and then some.
In 1978, Brookhaven began building ISABELLE, a synchrotron collider designed to detect new particles including the W and Z bosons. But by 1981, CERN had converted the SPS into a proton-antiproton collider and discovered both bosons within two years.
Even though ISABELLE’s four-mile tunnel had been dug, construction had begun and $200 million had been spent, the project was deemed obsolete and canceled in 1983.
The United States turned its attention back to the Tevatron, and had converted it to a collider by 1985. Europe soon built the 17-mile-long Large Electron-Positron Collider, but the Tevatron's main competition was internal, between the teams of scientists working on its two detectors. Discoveries began flowing from Illinois, including the top quark.
But American physicists were still feeling the burn of ISABELLE's defeat, and never stopped looking over their shoulder at CERN. They began plotting in 1983 to build a $5 billion machine with a 54-mile long track that could attain 20 trillion electron-volts and answer all those nagging questions about the universe.
They called it the Superconducting Super Collider.
"The Super Collider was born out of the failure of ISABELLE," said physicist Roy Schwitters, who was the director of the SSC project.
By 1986 the colossal machine had been designed, and Congress allocated $200 million toward planning. Twenty-five states offered up 43 sites for the SSC. Building at Fermilab made sense because the project could capitalize on existing infrastructure, and the Tevatron could be used to feed particles to the new collider. But Texas pledged $1 billion of its own money and won the collider, while Fermilab watched its future evaporate.
"Basically what they did is they thought big, and they went with Texas and went with a place where there was absolutely no connection to particle physics before," Halpern said. "They just started from scratch and really built a whole city, in a sense, to support this new collider."
With the support of President Reagan and the first President Bush, the SSC moved forward despite numerous technical challenges and internal disagreements among U.S. physicists. Ground was broken and the SSC was on target to begin working in 1999. Scientists hoped the Higgs might even show itself before the century was spent.
But in the meantime, Europe had decided to add the Large Hadron Collider to the existing 17-mile ring at CERN. European money that Congress had counted on began flowing toward the LHC instead. At the same time, the SSC budget grew to more than $10 billion, and the American collider began accumulating critics.
President Bill Clinton appealed to Congress to continue supporting the SSC, arguing that "abandoning the SSC at this point would signal that the United States is compromising its position of leadership in basic science — a position unquestioned for generations."
But in 1993, even though $2 billion had already been spent, more than 14 miles of tunnel had been dug and a quarter of the project was completed, Congress voted to kill the giant atom smasher.
The only things the SSC would ever smash were the careers of scientists who had bet everything on the new machine, and the hopes of the town of Waxahachie, Texas, which had completely poured itself into the project and was left with nothing but abandoned buildings.
The U.S. physics community would never quite recover from the blow.
"Ironically, if that had been built, all the discoveries we're talking about for CERN would have already been made," said Stu Loken, a Berkeley Lab physicist who worked on the Bevatron.
At this point, yielding the energy frontier to Europe is a done deal. And the United States is not likely to get it back. Like the LHC, should the next big machine be built, it will undoubtedly be an international project. Though it may never come to fruition, early planning is already underway for a mammoth machine called the International Linear Collider. The United States will most likely be involved, but the glory days of an American machine dominating the physics landscape are gone … almost.
The Tevatron is still king. Its celebrated detection of the top quark in 1995 was the last major discovery in high-energy physics. The Higgs boson has been a long time coming. Finally catching it at Fermilab wouldn't undo the heartbreak of the past, but it would certainly make it easier to switch off the lights and watch the world turn away to focus on the new machine.
Images: 1) Aerial view of the Tevatron ring / Fermilab. 2) Fermilab's Wilson Hall administrative building / Fermilab. 3) Dmitri Denisov / Betsy Mason, Wired.com. 4) Lawrence's original 4-inch cyclotron / Lawrence Berkeley National Laboratory. 5) ISABELLE's ring, now used for the RHIC / Brookhaven National Laboratory. 6) SSC / Jim Merithew, Wired.com.
See Also:
- For Sale: $20 Million Particle Accelerator, Never Used
- The Large Hadron Collider Demystified
- An Excerpt From the New Book, Collider
- Large Hadron Collider: Best- and Worst-Case Scenarios
- Video: Large Hadron Collider Fires Up Partying Physicists
- $8 Billion LHC Particle Smasher Gets New Start-Up Date
- Large Hadron Collider Down Until 2009
- LHC Suffers More Leaks, and Delays
- LHC to Begin Collisions in Fall… Right?
- Historic Atom Smasher Reduced to Rubble and Revelry
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