Science's summer blockbuster
Posted: Monday, August 04, 2008 6:45 PM by Alan Boyle
Maximilien Brice / CERN
Components of the ALICE detector spread out like sunbeams during the
integration of the device's inner tracker in March 2007. ALICE is one of
the four main detectors at the Large Hadron Collider.
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The advance buzz over the world's largest atom-smasher is reaching a steady hum, and the date for the Large Hadron Collider's official premiere in Europe is due to be announced as early as this week.
The first all-around injection of proton beams is expected in September - at just about the time that a federal judge in Hawaii considers a case claiming that the darn thing could destroy the world.
Meanwhile, the LHC's older, less powerful rival - the Tevatron at Fermilab near Chicago - has announced discoveries that suggest the Americans could yet steal some of the Europeans' thunder.
Eventually, the 17-mile-round (27-kilometer-round) Large Hadron Collider will smash opposing beams of protons with the energy of two bullet trains traveling at 100 mph. At those energies, previously undetected physical phenomena could pop out - ranging from the Higgs boson (which is thought to give subatomic particles mass) to microscopic black holes (which scientist have repeatedly said pose no danger) to supersymmetric particles (which could point the way to invisible dimensions of space and/or explain dark matter).
The project was conceived decades ago and has been under construction for five years. The startup schedule has been repeatedly delayed - from last November, to this spring, to this summer. But now Europe's CERN particle-physics center is focusing down on the final stage of preparations, and the superconducting collider magnets have been cooled down nearly to their target temperature, just 1.9 degrees Kelvin. That's colder than the background temperature of outer space.
Last week, CERN spokesman James Gillies told Physics World that he expected to announce the timing for the first beam injection - also known as "Red Button Day" - sometime this week. The current best guess is that Red Button Day will come during the second week of September, but we'll have to stay tuned for the official word.
Doomsday lawsuit due for hearing
By that time, a lawsuit filed against CERN as well as the U.S. Department of Energy may well get its day in court. The suit, filed in March by two critics of the LHC, contends that the collider could destroy the world if it creates micro black holes, strangelets or other weird phenomena. The critics want the court to block LHC operations, while federal lawyers want the suit dismissed.
Both sides are supposed to file additional briefs in the case over the next couple of weeks. A court hearing is scheduled Sept. 2, and the judge could conceivably render a ruling by Red Button Day.
Red Button Day will be the big day for news coverage but only one step in the startup process. It may well take until next year for the proton collisions to reach full power.
The race to find the Higgs boson (or not)
A little conflict adds spice to any blockbuster, and the court battle between the LHC's critics and its defenders isn't the only source of drama: Rival researchers at Fermilab are hoping to achieve a breakthrough before the European collider overtakes them.
Back in 1995, Fermilab's scientists announced that they had detected the last undiscovered quark, the top quark. Now the biggest quarry in particle physics is the Higgs boson, the last undiscovered fundamental particle whose existence has been predicted by the grand theory known as the Standard Model. The Higgs boson is thought to give rise to a field that selectively endows some particles (like protons) with mass, while letting other particles (like photons) go massless.
Physicists believe the Higgs boson may or may not be detectable at Fermilab's Tevatron collider, depending on how heavy it is. The latest word from the lab is that they're pretty sure how heavy it isn't. An analysis of collisions shows (to a 95 percent confidence level) that the Higgs boson can't have a mass around 170 GeV/c2, a measurement unit that reflects Einstein's E=mc2 formula for energy-mass conversion.
Fermilab |
The DZero experiment is one of the
detectors at Fermilab's Tevatron collider.
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"We're pretty energized about this," said Darien Wood, spokesperson for Fermilab's DZero experiment, who seemed hardly aware of the pun as he spoke it.
Fermilab's scientists soon expect to widen the no-Higgs zone, going down to 165 GeV/c2 and up to 175 GeV/c2. That would eliminate additional hiding places where the Higgs might lurk.
"These results mean that the Tevatron experiments are very much in the game for finding the Higgs," Pier Oddone, Fermilab's director, said in a news release issued today.
The strategy is to eliminate so many potential mass ranges that you can't help but find the Higgs by focusing on the ranges that are still open. It's like finishing up a jigsaw puzzle by trying all the leftover pieces until you come across the ones that fit.
"You're setting these limits, and at some point you don't get limits. You don't move," Wood explained. "That's one of the first indications of the signal. ... Ideally, we would hit one of these masses where the Higgs exists."
Previous experiments have indicated that the Higgs mass should be between 114 and around 200 (maybe even less) on the particle-mass scale. Other findings, announced just last week, indirectly suggest a much narrower range of 115 to 135.
All this assumes that the Higgs actually exists, of course. If it doesn't, then the Standard Model might turn out to be somehow substandard. Theorists would have to go back to the drawing board. And that could be the most exciting outcome of all.
Update for 8 p.m. ET Aug. 4: Do references to GeV/c2 make your eyes cross? Are you looking for something fun? Last week I linked to Kate McAlpine's "Large Hadron Rap," and the online exhibit at The Big Picture is also worth checking out. If you like your LHC images unfiltered, click on over to the collection at the CERN Document Server.
Update for noon ET Aug. 5: CERN spokesman James Gillies confirmed that the first beam injection is due to come sometime in the first two weeks of September, and he hoped to be able to announce the exact date this week. Although some of the temperature readings from the collider ring's sectors are bumping around above 1.9 degrees Kelvin, "the machine is basically cold now," he said.
The next big step in the testing is to check the injection kickers, part of the magnet system that feeds proton beams into the collider. This weekend, engineers will check the final magnet that "sends particles into the LHC vacuum pipe" for the clockwise proton beam, Gillies said. Some consider that to be a notable step because protons will be zipping into the LHC itself, though just in one sector.
Later this month, the injection kicker for the counterclockwise beam will be tested. The big day comes when protons first make the entire 17-mile route around the ring.
