large hadron collider
A portion of the Large Hadron Collider stretches along a tunnel at CERN'S accelerator complex, outside of Geneva. The LHC was due to start up again in March 2015, but a short circuit discovered March 21 in one of its magnets may delay its particle-hunting efforts by days to weeks.
(CERN)
Update: More information about the origin of the metal fragment that appears to have caused the short has been added to this story.
There's some kind of irony in this scenario: You're about to fire up the world's most powerful particle accelerator to do experiments aimed at tackling some of physics' biggest questions, but your plans are thwarted by an electrical short in a magnet that's supposed to help particles race around in your machine.
That's exactly the scenario that just happened at the Large Hadron Collider in Switzerland, where a short circuit was discovered on Saturday (March 21).
And here's why it seems ironic: A short circuit involves an electrical current flowing somewhere it's not supposed to go, and electrical currents involve electrons -- which are subatomic particles -- moving along a wire or other conductive material.
In other words, the LHC is a particle accelerator that's just been undermined by errant particles.
As for what caused the short, it appears to have been a metal fragment introduced into one of the LHC's magnets by upgrade work that involved cutting and welding. Scientists plan to remove it by burning it off or blowing it away with a puff of helium.
It's an easy enough fix, but it could take anywhere from a few days to a few weeks to remedy, depending on whether the collider, which had been cooled to its low operating temperature, needs to be warmed back up.
The LHC, which is coming off of a two-year break, was at its operating temperature in preparation for test runs this week that would have sent proton beams lapping around the device -- a safety protocol that must be completed before teams get to the business of smashing subatomic particles at new, higher energies.
Scientists are doubling the LHC's collision energies to conduct experiments that search for evidence of supersymmetry, an extension of physics' Standard Model theory, which describes the fundamental particles, or building blocks, of matter in the universe and how they interact. Supersymmetry predicts that particles (e.g. photons and quarks) are not solo operators in the universe but exist with partners (e.g. photinos and squarks).
One of the partners that researchers will be looking for is a gluino. It pairs with gluons, which are the stuff that "glues" quarks together inside protons and neutrons (the latter two particles are the inhabitants of an atom's nucleus that you may first hear about in general chemistry).
Finding a gluino could be exciting -- even more so than the Higgs boson -- because such a discovery could put scientists on a path to understanding the universe's elusive dark matter, which cannot be seen by telescopes but appears to exist based on the motions of galaxies and other astronomical objects. The connection between gluinos and dark matter is that the LHC's detectors won't be trying to capture gluinos directly but rather infer their presence by observing their decay products, namely neutralinos, which are the particles thought to make up dark matter.
And while a delay of possibly several weeks may seem frustrating to outsiders waiting impatiently for news of discoveries involving supersymmetry and dark matter, the director general of CERN, which runs the LHC, told BBC News, basically: A few weeks? Eh, that's just a blink of the eye when you're trying to expand humankind's understanding of the universe. (Not to mention, there are some folks who think the LHC could help sort out a new quantum mechanics theory about the existence of parallel universes ...)
-- Susannah L. Bodman, [email protected], www.facebook.com/Sciwhat.Science, Twitter: @Sciwhat