The world's largest particle accelerator restarted last Friday after a hiatus lasting more than three years (brief test last October aside) and almost immediately broke a world record. The collaboration announced that two proton beams had been accelerated to a record energy of 6.8 tera-electron volts (TeV) per beam.
The Large Hadron Collider (LHC) is now more powerful than ever, and its operators hope the upgrades performed in the downtime will enable the Standard Model of Particle Physics to be put to its most strenuous tests yet. The upgrades may also allow the LHC to produce some of the particles theorized to make up dark matter and to pursue the search for extra dimensions.
On its first day back the LHC's operators at CERN in Switzerland started things moving by slamming two beams of protons into each other to meet with an energy level of 6.8 TeV, a new world record. That's not far off the machine's goal over the next two years to achieve energies of 7 TeV.
“It’s only the start of a very long commissioning period, which would bring us to actually collide the two beams for the experiments, and provide the highest-energy collisions, which should happen six to eight weeks from now,” said Jörg Wenninger, head of the LHC beam operation section, in a CERN video.
Operations starting from last week are known as Run 3 and are expected to continue to at least 2026 following the initial runs of 2009-13 and 2015-18, Runs 1 and 2 respectively. In other circumstances, a piece of scientific equipment that spent almost as much time in maintenance and upgrades as operating might be considered a failure, but this is the machine that found the Higgs Boson, and 59 hadrons. It's credit is good, give or take an embarrassing typo or two.
“The LHC itself has undergone an extensive consolidation programme and will now operate at an even higher energy and, thanks to major improvements in the injector complex, it will deliver significantly more data to the upgraded LHC experiments,” said CERN's Dr Mike Lamont.
The LHC consists of a 27-kilometer ring of superconducting magnets that accelerate and focus beams of particles to close to the speed of light and then focus them onto collision points. During the long shutdown, 22 magnets were replaced, and extra refrigeration systems were added, among other changes to the LHC itself. Meanwhile, the various detectors, including the ATLAS and CMS, which independently verified the Higgs Boson discovery, have each had upgrades of their own
More collisions are anticipated in Run 3 than the previous two combined, and A Large Ion Collider Experiment (ALICE) is expected to record 50 times as many of the heavy-ion collisions in which it specializes as it did before.
Dark matter is thought to make up six times as much of the universe as the ordinary baryonic matter we can see, but its nature is still unknown. Most theories propose it is made from particles too heavy to have been created by previous equipment. The LHC's upgrades may allow it to produce at least some of these missing particles. It not expected any of the detectors will be able to capture the particles. However, the hope is scientists will be able to deduce their existence, and their mass, from the differences between the energy that goes into the collisions that create them, and the combined energy of those we can witness afterwards.
Even more ambitiously, Run 3 may help us test theories of the universe that propose extra dimensions beyond the four we experience – the three directions and time.
Just look out for weasels.