Higgs boson was just a start – other mysteries await
Mark Thiessen/National Geographic Society
When it comes to shutting down the most powerful atom smasher ever built, it’s not simply a question of pressing the off switch.
In the French-Swiss countryside on the far side of Geneva, staff at the Cern particle physics laboratory are taking steps to wind down the Large Hadron Collider. After the latest run of experiments ends next month, the huge superconducting magnets that line the LHC’s 27km-long tunnel must be warmed up, slowly and gently, from -271 Celsius to room temperature. Only then can engineers descend into the tunnel to begin their work.
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. 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 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. Physicists will not sit around idle while the collider is down. 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.
But the LHC was always more than a Higgs hunting machine. There are other mysteries of the universe that it may shed light on. 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’s a long way to go yet…”
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. If the particles that constitute it are light enough, they could be thrown out from the collisions inside the LHC. While they would zip through the collider’s detectors unseen, they would carry energy and momentum with them. Scientists could then infer their creation by totting up the energy and momentum of all the particles produced in a collision, and looking for signs of the missing energy and momentum.
One theory, called supersymmetry, proposes that the universe is made from twice as many varieties of particles as we now understand. The lightest of these particles is a candidate for dark matter…
Another big mystery the Large Hadron Collider may help crack is why we are made of matter instead of antimatter. The big bang should have flung equal amounts of matter and antimatter into the early universe, but today almost all we see is made of matter. What happened at the dawn of time to give matter the upper hand?
The question is central to the work of scientists on the LHCb detector. Collisions inside LHCb produce vast numbers of particles called beauty quarks, and their antimatter counterparts, both of which were common in the aftermath of the big bang. Through studying their behaviour, scientists hope to understand why nature seems to prefer matter over antimatter…
Extra dimensions may separate us from realms of space we are completely oblivious to. “There could be a whole universe full of galaxies and stars and civilisations and newspapers that we didn’t know about,” says Parker. “That would be a big deal.”
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