Some particles are easy to spot
Alastair Philip Wiper/Corbis/Getty
LAST week, physicists from CERN announced disappointing news: a potential new particle, set to shake up modern physics, doesn’t exist. So what will they do now?
The dream had lasted almost eight months, since the ATLAS and CMS collaborations found an unexpected bump in their data last year. The detectors at the Large Hadron Collider (LHC) had measured more proton pairs with a shared energy of 750 gigaelectronvolts (GeV), than is predicted by the standard model of particle physics.
If the detection had turned out to be genuine, this could have pointed to a new particle. Theorists produced more than 500 papers on how such a find would affect our understanding of particles and forces. But data gathered this year and presented at the International Conference on High Energy Physics in Chicago on 5 August confirmed that the excess was a statistical fluke, the equivalent of getting a surprise run of heads when flipping an ultimately fair coin.
“Our job is to kill the standard model, it’s what we do. But it might take 20 years“
All is not lost for those theories, though, says CMS researcher Freya Blekman at the Free University of Brussels, Belgium. “These fluctuations really drive the creativity in the theoretical section of our field,” she says, and a breakthrough may change everything. “It could still be that one of those 500 papers is totally true.”
But proving that will take a while. The LHC is now functioning close to its highest possible energy levels, meaning there aren’t likely to be any more sudden surprises. “There are a few chances in the life of a collider where it feels like there is a big opportunity, where you take a big step in energy,” says former ATLAS researcher Adam Gibson, now at Valparaiso University, Indiana. “All of a sudden there’s the chance that there was something just around the corner.” This time, that didn’t check out.
CMS spokesperson Tiziano Camporesi remains confident. “I have no doubt that the accelerator is going to deliver, and it’s up to the experiments now to take the challenge,” he says. There’s certainly plenty to look for. Gaps in the standard model leave much potential for the existence of new physics: it fails to account for the mass of neutrinos, the behaviour of gravity or the existence of dark matter and dark energy.
“Nature is screaming at us from the sky that there is dark matter, lots of it, there is dark energy,” says Gibson. “We would sure like to have some hints of that in our colliders.”
There is an air of inevitability about the search, even as this particular blip fades into memory. “Our job is to kill the standard model: it’s what we do,” says Blekman. “There are many ways to do that, and we are still discovering more and more ways, but it might take 20 years.”
Experimenters will continue to pick at the edges of the standard model, scrutinising the behaviour of the heaviest and lightest particles. They will keep looking for new particles that could point to exotic physics like supersymmetry, in which every particle in the universe has a near-identical partner particle.
Bumps like the one at 750 GeV crop up all the time; mostly they fade away with more data, but once in a while, as with the Higgs boson in 2012, they stick around to provide enormous insights into the deeper workings of nature.
More results from the LHC’s most recent run will be released in coming months, but the most complicated analyses of data could take years. On top of that, it will be decades before the next generation of planned particle accelerators comes online to continue the search for exotic physics. It looks as if the universe is going to make us wait.
This article appeared in print under the headline “What next after mooted new particle vanishes?”
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