LHC restart: ‘We want to break physics’-
As the Large Hadron Collider (LHC) gears up for its revamped second run, hurling particles together with more energy than ever before, physicists there are impatient. They want this next round of collisions to shake their discipline to its core. “I can’t wait for the switch-on. We’ve been waiting since January 2013 to have our proton beams back,” says Tara Shears, a particle physics professor from the University of Liverpool. Prof Shears is raising her voice over the occasional noise of fork-lift trucks and tools, as well as the constant hum of the huge experimental apparatus behind her: LHCb, one of four collision points spaced around the LHC’s 27km circumference. All this noise reverberates because we are perched at the side of an imposing cavern, 30 storeys beneath the French-Swiss border. The other three experiments - Atlas, CMS and Alice - occupy similar halls, buried elsewhere on this famous circular pipeline. ‘Everything unravels’ In mid-March two beams of protons, driven and steered by super-cooled electromagnets, will do full circuits of the LHC in both directions - for the first time in two years. When that happens, there will be nobody between here and ground level.Then in May, if the protons’ practice laps proceed without a hitch, each of the four separate experiments will recommence its work: funnelling those tightly focussed, parallel beams into a head-on collision and measuring the results. For us, now, the other stations on the ring are a 10-20 minute drive away; for the protons, a lap will take less than one ten-thousandth of a second. They have the advantage of travelling a whisker under the speed of light. They are moving with so much energy that when they collide, things get hot. Historically hot. “We’re recreating temperatures that were last seen billionths of a second after the Big Bang,” Prof Shears explains. “When you get to this hot temperature, matter dissociates into atoms, and atoms into nuclei and electrons. “Everything unravels to its constituents. And those constituents are what we study in particle physics.”
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