January 31, 2012 | 5
Fermilab is dead. Long live Fermilab!
The Tevatron at the Fermi National Accelerator Laboratory in Batavia, Ill., which had been the top U.S. particle collider—and for many years the most powerful such machine in the world—shut down last September. The collider’s physics breakthroughs, including the 1995 discovery of the top quark, were so eminent that it was easy to think of the Tevatron and its host institution as one and the same.
But even though protons and antiprotons no longer course through the six-kilometer loop of the Tevatron, life at Fermilab goes on. Physics World editor Margaret Harris reports on a recent lab visit (registration required):
The end of the Tevatron does not, however, mean the end of Fermilab. “We have 10 accelerators here on site,” says Fermilab physicist Steve Holmes, with the merest hint of irritation. “We turned one of them off, okay?” Like several scientists I spoke to, Holmes was keen to point out that colliding high-energy beams of particles is not the only way of discovering new physics with accelerators.
The U.S. has surrendered the “energy frontier” to Europe, Harris notes: the Large Hadron Collider at CERN, outside Geneva, is designed to accelerate particle beams to seven times the energies achievable in the Tevatron. New and ongoing projects at Fermilab, Harris writes, are focused on physics questions that do not require a gigantic, world-beating collider. Many of these projects depend less on energy and more on intensity—producing beams with copious amounts of particles to look for rare decays or interactions.
Take neutrino physics, for instance. Neutrinos are slippery subatomic particles that can only be seriously investigated with an intense particle beam. They interact so rarely with ordinary matter that for every 1,500 or so neutrinos registered by a massive, specially designed detector, billions more will pass right through. So you need to create a lot of them. Neutrinos, already mysterious, became even more so last fall when a European experiment called OPERA (Oscillation Project with Emulsion-Tracking Apparatus) found that neutrino pulses appeared to make the journey from CERN to an underground lab in Italy a bit faster than the speed of light, in violation of one of the central tenets of modern physics.
Fermilab has its own cutting-edge neutrino experiment that should be able to confirm or (as most suspect) refute the OPERA claim—as well as probe other puzzles of these particles. MINOS (Main Injector Neutrino Oscillation Search) shoots a beam of neutrinos through two detectors, one at Fermilab and one in a Minnesota mine some 735 kilometers away. In addition to clocking the neutrinos to determine their speed, MINOS is investigating an odd phenomenon called neutrino oscillation. Occasionally one of the particles oscillates between “flavors” on its journey across the Midwest, so that a muon neutrino becomes a tau neutrino. A planned project called NOvA will succeed MINOS, extending the baseline of the neutrino experiment to about 800 kilometers and adding a much larger detector on the Minnesota end.
Then there’s the proposed Long Baseline Neutrino Experiment, or LBNE, which would send neutrinos on an even longer interstate journey of 1,300 kilometers from Fermilab to a subterranean detector in South Dakota. LBNE, Harris reports, would be able to compare the flavor oscillations of neutrinos to those of their antiparticles. A major question about neutrinos is whether they are their own antiparticles. And a proposed multibillion-dollar lab upgrade called Project X would add new proton accelerators to increase the intensity of the beams feeding LBNE and other Fermilab projects.
As the memory of the Tevatron fades, all eyes are on the high-energy pursuits of the Large Hadron Collider, which has a good shot of finally discovering the long-sought Higgs particle this year. But no one lab, however powerful, can do it all. Older particle labs remain vibrant centers of discovery—places such as Brookhaven National Laboratory and the SLAC National Accelerator Laboratory were also once known primarily for their particle colliders but have since developed diverse research campaigns. If Fermilab can convince Congressional funders that the intensity frontier is worth exploring, this new direction may yield U.S. physicists a few surprises.
“This is an opportunity for the U.S. to establish a leadership position in this very important area of physics that will last for decades,” Fermilab’s Holmes told Physics World. “If we do it right, we’ll just blow away the competition.”