Massive proton collider is a great big hit after all

In 2008, when faulty wiring closed down the $10-billion Large Hadron Collider for more than a year, many wondered whether physicists at the European Organization for Nuclear Research had a white elephant on their hands.

But the revelation Wednesday that the collider’s ATLAS and CMS detectors had found a new particle that could well be the long-searched-for Higgs boson would seem to put any lingering worries to rest.

The LHC, as the collider near Geneva is known, has been amassing data at a rate no one thought possible even as recently as February, said Vivek Sharma, a UC San Diego physicist and member of the CMS research group. Just since June, the LHC has tracked as many proton-proton collisions as it recorded in all of 2011: 400 trillion.

“The fact that we could accomplish this is a big surprise,” he said.


Robert Cousins, a UCLA physicist who’s also affiliated with the CMS team, attributed the collider’s success to several factors.

Technicians managed to squeeze more protons into the beams that the physicists smash together to spawn subatomic particles to study. That’s not easy, since protons have a positive charge and they tend to repel each other when they get too close, disrupting their intended path.

“It’s a huge technical challenge” involving enormous amounts of energy, Cousins said.

The LHC has run dependably, remaining in operation about 50% of the time instead of a more typical 25%. And the ATLAS and CMS experiments were able to get useful data from 85% to 95% of the collisions, Cousins said, noting that the scientists had expected to get good data from only about half of collisions.

Packing in all those extra protons and running the machine twice as much as expected led to another problem: figuring out how to crunch all the data.

The experiments were designed to handle a case in which 20 protons would hit one another, Cousins said, but the scientists were getting collisions involving 40 or 50 protons. They had to write new algorithms so that their computers could sift through the data and spot potential Higgs candidates.

John Gunion, a UC Davis physicist who is not on either Higgs-hunting team, called the collider’s performance and the scientists’ discovery “a tribute to the progress of civilization.”

“We’ve reached the mountaintop, or something like that, by virtue of huge collaborations and huge technical groups that only an organized society could allow,” he said. “You couldn’t imagine getting to this fundamental level of understanding the universe without everyone involved.”