It's official: Fermilab's Tevatron accelerator has a new lease on life, thanks to the decision of a group of experts — the High Energy Physics Advisory Panel (HEPAP) that reports to the US Department of Energy — to extend its operation for another three years, through 2014.
That puts the aging Tevatron, in Illinois, back in the game for being the first to spot the elusive Higgs boson. Its main competitor? That shiny new accelerator in Switzerland called the Large Hadron Collider.
Reports earlier this summer that the D-Zero collaboration at Fermilab may have glimpsed the elusive Higgs proved to be a bit premature. It was a so-called "three-sigma" event, which refers to the statistical certainty of a given result. Such events show up from time to time in accelerator data; usually they are inconclusive, or are later determined to be noise in the signal.
Ideally, scientists consider a five-sigma event to be the "gold standard" for discovery. But while this summer's result might not constitute a bona fide discovery of the Higgs, it's strong evidence of the particle's existence — and that scientists are honing in on the boson.
Fermilab's D-Zero and CDF collaborations have also helped narrow the focus of the search for the Higgs, with results announced at July at the International Conference on High Energy Physics in Paris. Essentially they've narrowed the range of what the Higgs' mass is likely to be.
This, in turn, helps them focus their future searches by excluding the most unlikely possible masses as they sift through the huge amounts of data from collisions.
And the Tevatron isn't just hunting for the Higgs. Back in May, the D-Zero collaboration announced that it had analyzed data from a bunch of proton-anti-proton collisions and found a slight asymmetry in the number of muons produced compared to anti-muons: about 1 percent more. The most likely culprit for this strange asymmetry is a new particle not predicted by the Standard Model. It's important because it could provide a possible explanation for the slight asymmetry between matter and antimatter in the earliest phases of our universe.
It just goes to show that even an old accelerator everyone thinks is past its prime can still find itself doing exciting, relevant science in its later years. And it puts pressure on the LHC scientists: that machine is still ramping-up to full power, and isn't expected to find any sign of the Higgs for at least the next two to three years. In fact, the LHC will shut down in 2011 for up to a year of planned maintenance work, giving the Tevatron an opening in the race.
Competition can be good in such a situation, and apparently the extension for the Tevatron has broad support in the particle physics community — including scientists who work at the LHC. The two machines have different strengths: the LHC will reach higher energies, but the Tevatron is capable of greater luminosities (the intensity of the beams). In fact, they could even prove complementary, each measuring different properties of the Higgs particle.
In the meantime, the race continues to heat up. Back in June, the LHC smashed the record for most particle collisions, doubling the previous rate to reach about 10,000 particle collisions per second. More collisions means that many more opportunities to observe interesting new physics. (Fermilab still holds the record for highest beam intensity.) For its part, Tevatron scientists announced that same month that there may be not just one Higgs boson, but five different versions, with similar masses but different electric charges.
We say, let the games begin! May the best atom-smasher win.