Tevatron Racing LHC to the Finish
Can the Biggest US Particle Collider Cash In on Delays in Europe?
Nov 10, 2008
For more than 25 years, the Tevatron particle collider at Fermi National Accelerator Laboratory has ruled the field of international particle physics. Now the end of its reign is near.
With seven times the Tevatron’s energy, Europe’s Large Hadron Collider will claim the “energy frontier” in Spring 2009. And Tevatron funding ends in 2010, under budget plans in the US Department of Energy, the lab's funding agency.
Scientists at Fermilab, about 30 miles west of Chicago, are resigned to the inevitable.
“Most of us agree that unless the LHC is delayed by more than three years, the most natural time to end Tevatron operations is late 2010,” says Dmitri Denisov, cospokesman for the 600-member collaboration at the DZero particle detector.
Strong Link To The Higgs
There’s still that six-month window of opportunity for a discovery while the LHC is down.
“There are many exciting hints in our data,” Denisov says. “We are optimistic that at least some of them will convert into major scientific results.”
DZero recently uncovered one such gem. The gold prize in particle physics is the first observation of the Higgs boson. This predicted force-carrier particle holds the key to the phenomenon of mass: why each fundamental particle has a different level of mass, and why the property of mass exists at all.
Discovering the Higgs is most likely destined for the more powerful LHC. But in July 2008, DZero scientists found another intriguing clue. Scientists produced a rare pairing of the Z boson, one of the carrier particles involved with the weak nuclear force (along with the W boson). This uncommon ZZ pairing has a strong connection with the Higgs. Its physical properties resemble the Higgs, and experimental techniques for finding the ZZ would be the same for the Higgs.
The Higgs Is Hiding
The ZZ result also meant that the Higgs would not have a mass of 170 GeV (giga electron volts), the mass of the ZZ pair. If the Higgs had a mass of 170, the experimenters would have seen it. Mass limits for the Higgs have been set by several experiments at 115 GeV (low end) and around 185 GeV (high end). The masses of fundamental particles are described by their energy.
“The Higgs is still hiding between 115 and 185 GeV,” says Denisov. “But we are definitely saying [the Higgs] is not at 170 GeV.”
Even after the shutdown, and after the final stream of data dries up, Denisov says the lab expects another two to four years of data analysis. He also expects that within a year or so of the shutdown, scientists at the two Fermilab detectors (the other is called CDF) would complete their studies related to the Higgs.
Quark Discoveries, Top And Bottom
The underground Tevatron accelerator, four miles in circumference, produces billions of collisions each second between protons and their antimatter counterparts, antiprotons, coursing through the accelerator’s single beam tube at nearly the speed of light.
In July 1995, the lab announced the Tevatron’s discovery of the biggest fundamental particle of matter: the top quark, smaller than a proton but with as much mass as an atom of gold. In 1977, the Tevatron’s predecessor accelerator uncovered the bottom quark, ranking second in mass among the six quarks in the Standard Model.
When the big machines shut down, Fermilab will maintain a research program focused on the puzzling neutrinos, which have virtually no mass and rarely interact with other particles. But there will be no big, high-energy accelerator to compete with the LHC. In particle physics, second place feels like no place.
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