The search for dark matter on Earth has failed to reveal what it is made of, but the LHC may be able to make the substance. There is so much dark matter, it outweighs by five times the normal matter in the observable universe. Studies of spinning galaxies show they rotate with such speed that they would tear themselves apart were there not some invisible form of matter holding them together through gravity. The only way dark matter has revealed itself so far is through the pull it exerts on galaxies. The label "dark" refers to the fact that the substance neither emits nor reflects light. "We need to make more precise measurements, to refine the particle's mass and understand better how it is produced, and the ways it decays into other particles." Scientists at Cern expect to have a more complete identikit of the new particle by March, when repair work on the LHC begins in earnest.īy its very nature, dark matter will be tough to find, even when the LHC switches back on at higher energy. "The headline discovery was just the start," says Wells. The lab fast-tracked the search for the particle, but cannot say for sure whether it has found it, or some more exotic entity. The hunt for the Higgs boson, which helps explain the masses of other particles, dominated the publicity around the LHC for the simple reason that it was almost certainly there to be found. What is the dark matter that clumps invisibly around galaxies? Why are we made of matter, and not antimatter? And why is gravity such a weak force in nature? "We're only a tiny way into the LHC programme," says Pippa Wells, a physicist who works on the LHC's 7,000-tonne Atlas detector. There are other mysteries of the universe that it may shed light on. There is far more to know about the new Higgs-like particle, and clues to its identity are probably hidden in the piles of raw data the scientists have already gathered, but have had too little time to analyse.īut the LHC was always more than a Higgs hunting machine. Physicists will not sit around idle while the collider is down. The particle accelerator, which reveals new physics at work by crashing together the innards of atoms at close to the speed of light, fills a circular, subterranean tunnel a staggering eight kilometres in diameter. Since then, the machine has been forced to run at near half its design energy to avoid another disaster. The accident happened days after the LHC was first switched on in September 2008, when a short circuit blew a hole in the machine and sprayed six tonnes of helium into the tunnel that houses the collider. The work will beef up electrical connections in the machine that were identified as weak spots after an incident four years ago that knocked the collider out for more than a year. The machine that last year helped scientists snare the elusive Higgs boson – or a convincing subatomic impostor – faces a two-year shutdown while engineers perform repairs that are needed for the collider to ramp up to its maximum energy in 2015 and beyond.
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