After a two-year-long overhaul, thousands of researchers are getting ready to restart the $10 billion Large Hadron Collider — and this time, they’re going to turn the world’s most powerful particle-smasher up to the max.
“It’s a new machine,” Fermilab physicist Don Lincoln, a member of the science team behind the LHC’s Compact Muon Solenoid detector, told NBC News.
Engineers have beefed up the interconnections between the supercooled magnets in the collider’s 17-mile-round (27-kilometer-round) underground ring, built at the CERN particle physics center at the French-Swiss border. Meanwhile, the detectors have been upgraded to accommodate bigger, brighter bangs. The proton collisions will reproduce the conditions that existed in the universe just a tiny fraction after the Big Bang.
The LHC’s fresh start comes after a years-long campaign that led to the discovery of the long-sought Higgs boson (a.k.a. “God Particle”) in 2012. That find capped a 40-year quest to fill in the last big gap in the Standard Model of particle physics, one of the most successful theories of the scientific world.
The Higgs boson is part of the mechanism that imparts mass to other subatomic particles. Lincoln and other physicists hope that studying the Higgs in detail will point the way to weird phenomena, such as supersymmetry — the idea that every particle we know (such as the neutrino) has an as-yet-undetected partner with complementary characteristics.
One such particle, dubbed the neutralino, may be the stuff that dark matter is made of. Dark matter accounts for more than 80 percent of the universe’s mass, but the only way it’s been detected so far is through its galactic-scale gravitational pull.
So far,the LHC has found no evidence of supersymmetry, neutralinos or other exotic phenomena such as mini-black holes and extra dimensions of space. For some physicists, that’s a bit of a disappointment — but not for Lincoln.
“I see that as an affirmation that we’ve done an incredible job of understanding the universe,” he said.
Turning up the dials
New physics could emerge when the dials on the LHC are turned up beyond the levels that were reached before the overhaul. Back then, the beams of protons that circulated through the ring smashed together with a peak energy of 8 trillion electron volts, or 8 TeV. In the next few months, that energy will rise by more than 60 percent, to 13 TeV. What’s more, the luminosity of the beam will eventually triple.
The schedule for “Run 2” calls for proton beams to start circulating through the LHC once more at low energies next month, with science observations resuming in May. The dials are due to be turned up to 13 TeV by the end of this year.
Seven years ago, soon after the LHC was started up for the first time, a helium leak set off an underground explosion that required more than a year of repairs. Lincoln said the team learned valuable lessons from that episode.
“It turns out that there were some engineering oversights,” he said. “The magnets were instrumented incredibly well, but the connections between the magnets were not instrumented as well as they should have been. … Those dangers are now past.”
Before the initial startup, CERN’s scientists had to address a string of doomsday worries — including claims that the collider would create globe-gobbling black holes or cosmos-wrecking strangelets. A legal challenge that sought to stop the LHC wound its way through federal courts for more than two years. Even though the claims have been countered repeatedly, Lincoln acknowledged that the doomsday questions could resurface as the machine ramps up again.
“I have no problem with people asking these questions,” he said. “Luckily, there is a compelling answer. The answer is that the Earth, the sun and other celestial bodies have been constantly bombarded with particles at energies that are higher than we could possibly create. If it were dangerous, the Earth wouldn’t be here. The sun wouldn’t be here. … People can rest assured that, whatever we discover, it must be safe.”