The big story ended up a sort of non-story. In 2012, scientists working at the LHC were surprised to see the same statistical anomaly in two separate experiments: a fluctuation in the data implied a new particle whose energy level, some 750 GeV, would have meant it was six times heavier than the Higgs boson. ATLAS and the CMS experiment both reported the same anomaly, leaving physicists alternately puzzled and excited. “Every explanation of the 750 GeV excess needs a new particle,” commented Kansas University physicist Kyoungchul Kong, and a new particle in that range would require a departure from the Standard Model.
But, after a year of inspection, CERN is ready to put the kibosh on that idea. As they announced at the International Conference on High Energy Physics, “The intriguing hint of a possible resonance at 750 GeV decaying into photon pairs, which caused considerable interest from the 2015 data, has not reappeared in the much larger 2016 data set and thus appears to be a statistical fluctuation.”
“No new particle announced at #ICHEP2016 today but that’s how science works,” tweeted Fermilab.
When news of the blip first broke, mountains of papers were submitted to the various peer-reviewed particle physics journals, including Physical Review Letters, the leader in the field. Some thought the readings could mean the teams had found WIMPs; others thought the discovery could shed light on the balance of matter and antimatter. Kong coauthored one of the four papers that PRL ultimately published, and his proposed explanation for the anomaly was a leap. Most models straightforwardly assumed a new particle at 750 GeV, Kong explains, but his explanation is a “sequential cascade decay” of a heavier particle into photons that can “fake the resonance signal” at 750 GeV.
Pauline Gagnon, who has retired from CERN, commented that while “major leaps” are rare, blips in the data are “not uncommon in particle physics given the statistical nature of all phenomena we observe.” In plain language, the LHC produces such a stupefying amount of data that it should be no surprise to find some outliers.
“Had the bump been real, it would have without a doubt been the most important discovery in particle physics in the past half century,” said cosmologist Lawrence Krauss. “Which is why the odds were that it probably wasn’t.”
Dr. Tiziano Camporesi, spokesperson for the CMS detector team, said, “It’s disappointing because so much hype has been made about it.” But, because the experimenters had known from the beginning that the blip was probably just a blip, “we have always been very cool about it.”
In the end, it’s not like we’re going to retire the atom smashers for not finding a particle that breaks out of the Standard Model. The LHC should be running for decades yet. “Theorists propose ideas,” said Kong, “and experimentalists perform experiments to test the ideas, then publish their results – and we try to understand.”
Now read: How does the Large Hadron Collider work? and What is the Higgs Boson, and why is it so important?