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Canadian scientists among those intensifying search for new particles


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What do you do if 10 quadrillion high-energy collisions in the world’s largest particle accelerator fail to reveal any new truths about the nature of reality? The answer: Revamp your machine and go for 10 times that number.

In a nutshell, that explains the groundbreaking ceremony that took place on Friday at the Large Hadron Collider, or LHC, near Geneva, Switzerland.

Canada is one of dozens of countries participating in the project, which will eventually see the collider’s performance increase tenfold by the middle of the next decade. Researchers hope the higher number of collisions that result will increase the likelihood that they will spot some extremely rare clues to a more fundamental theory of matter than the current standard model of particle physics.

“It’s the next step in the development of the LHC,” said Oliver Kester, an associate director at the TRIUMF accelerator in Vancouver, which co-ordinates Canada’s participation in the international experiment.

The $11-billion LHC made headlines in 2012, when it verified the existence of the Higgs boson, a long predicted particle that was seen as a crucial signpost on the way to a deeper understanding of the laws that govern the universe’s basic constituents. However, in the nearly six years since the Higgs showed up, the journey for LHC has been like a long, featureless drive with no indication of anything more to see.

The situation has perplexed physicists who are looking to replace the standard model with a new theory that can encompass dark matter, a substance whose existence has been inferred by astronomers through its gravitational influence on stars and galaxies, but that has never been directly detected.

The LHC’s operators say they want to pin down the properties of the Higgs boson with as much precision as possible to see if there are any small divergences from expected values that current theory can’t explain.

“We are looking for the tiniest possible deviations,” said Fabiola Gianotti, director-general of CERN, the sprawling European research facility where the LHC is based.

The LHC works by accelerating protons in two opposing beams around a 27-kilometre-long circular tunnel. The beams cross at only four points where protons that are travelling at nearly the speed of light can collide and release enough energy to spontaneously form new particles, such as the Higgs. These decay in an instant, but they leave their traces in the building-size detectors built around the collision points. Canada supplied hardware for one of those detectors, called ATLAS, and is currently developing new components for an intermediate upgrade that will begin after the beams are shut down for two years starting in November.

After another round of data-gathering that will last from 2021 to 2023, the experiment is set to undergo a far more ambitious overhaul, which was set in motion by Friday’s groundbreaking. The overhaul will ultimately require replacement of the collider’s superconducting magnets, a change aimed at increasing the amount of data coming from the experiment by adding more protons to the beams and boosting the rate at which they collide.

About 150 Canadian researchers are working with the LHC, including planning for its future improvement.

Jens Dilling, a research scientist at TRIUMF, said that the souped up collider will need more robust detectors and sensors that can withstand the high radiation environment. He added that Canada could have additional opportunities to contribute expertise in machine learning, because the sheer amount of data the collider is expected to produce after the overhaul is completed around 2025 would overwhelm scientists working with conventional computer systems.

“We will need artificial-intelligence-driven analysis tools to tease out new physics,” he said.

Yet, in spite of such frontier-pushing improvements, it is also possible the Large Hadron Collider will have nothing more to find, leaving physicists to try other approaches.

“At the end, the answer is in nature’s hands,” Mr. Gianotti said. “And nature is always more elegant and more simple than all our theories.”

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