The world's largest particle accelerator, which famously discovered the long-sought Higgs boson in 2012, will soon start up again at almost double the energy of its first run.
After a two-year hiatus for upgrades, the Large Hadron Collider (LHC), at the European Organization for Nuclear Research (CERN) in Switzerland, will be able to produce particle collisions at an energy of 13 teraelectron volts (TeV) by May, compared to the 8-TeV collisions during previous operations, CERN officials said at a news conference today (March 12).
By looking at these higher-energy collisions, researchers hope to see beyond the Standard Model of particle physics, the reigning theory that describes the fundamental particles and how they interact. This could include finding other Higgs bosons, or producing dark matter, the mysterious substance that makes up about 85 percent of the total matter in the universe, researchers said. [Beyond Higgs: 5 Elusive Particles That May Lurk in the Universe]
"We're headed again into unexplored territory," said David Charlton, a spokesman for ATLAS, one of two LHC experiments that found evidence in July 2012 of a particle bearing the characteristics of the Higgs boson, a particle thought to give all other particles their mass.
The LHC consists of a 17-mile-long (27 kilometers) ring of superconducting magnets that accelerates particles to near the speed of light. The LHC produces two beams of protons, and collides them at four locations inside the machine. To make the magnets superconductive, they are chilled using liquid helium to minus 456.3 degrees Fahrenheit (minus 271.3 degrees Celsius), a temperature colder than outer space.
In its first season of operation, which lasted from 2009 to 2012, the LHC was able to produce collisions at energies of up to 8 TeV. The discovery of a Higgs-like particle — whose existence scientists had long theorized — helped confirm the Standard Model, the theory that has successfully explained nearly all of experimental particle physics. But in order to look beyond this model and discover new physics, higher-energy collisions are needed.
During its two-year shutdown, the LHC underwent substantial maintenance and upgrades, Frederick Bordry, CERN's director of accelerators and technology, said at the news conference. These included strengthening the connection between the magnets, improving the protection against a superconductive breakdown (or quenching) of the magnets, improving the radiation protection and cooling systems, and doubling the number of "bunches" of protons injected into the collider to produce more collisions, Bordry said.
Over the weekend, technicians performed the first test to inject particle beams into the LHC. The collider will be up and running within two weeks, but it will take about two months before the LHC will achieve the first collisions for physics, said Ralph Heuer, CERN's director general. [Wacky Physics: The Coolest Little Particles in Nature]
Meanwhile, researchers can't wait to look for new physics.
One of their prime focuses will be the Higgs boson. For example, scientists want to see if the particle decays in unexpected ways, and whether there might be other Higgs bosons.
"In families with only one child, the child behaves completely different from if it were in a family with 10 children," Heuer said. If the Higgs turns out to be one of many, it will have different properties from the Standard Model, and "we will have a clue where to go," Heuer added.
Another area the upgraded LHC will be able to probe is dark matter, which has not yet been directly detected. That will be one of the focuses of CMS, the other experiment that found evidence of the Higgs, said CMS spokesman Tiziano Camporesi. Einstein's famous equation E = mc^2 says that mass is equivalent to energy. "So, if we want to produce a new state of matter, we need to have the energy to produce it," Camporesi said.
In addition to the Higgs and dark matter, the LHC could give scientists a glimpse of the conditions present immediately after the Big Bang. ALICE, another LHC experiment, will now be able to study conditions that are "even hotter, even longer-lived and even more violent" than before, ALICE spokesman Johannes Wessels said today.
Throughout the news conference, scientists kept repeating the phrase, "if nature is kind to us." But what happens if the researchers don't find anything?
Even if the LHC doesn't find any new particles, it could still accumulate data that will improve the precision of its measurements, the researchers said.
"If we don't find something directly, we might well find something indirectly," Heuer said.