CERN anomaly hints at new particle physics Standard Model can't explain
CERN’s Large Hadron Collider (LHC) is designed to probe the fringes of known physics, and now the facility has found particles not behaving as predicted. While it’s still early days, the discovery hints at the existence of new particles or forces beyond the Standard Model.
The discovery was made in one particular experiment called the LHCb, which studies particles called “beauty quarks.” These exotic fundamental particles are produced in high numbers in the LHC collisions, but they don’t last long – beauty quarks quickly decay into electrons and muons.
According to the Standard Model of particle physics, beauty quarks are expected to decay into electrons and muons at equal rates. But the new data from LHCb suggests that’s not the case – rather than flipping a coin, beauty quarks tend to favor decaying into electrons more than muons. In five years’ worth of data, the team found that for every 100 electron decays, there were only about 85 muon decays.
Why exactly that’s happening remains a mystery, and can’t be explained by the Standard Model. The team says that the only reason there should be any preference towards one or the other is that some hidden particle is influencing the outcome.
Intriguingly, the new find is the culmination of several years’ worth of other studies that also hinted at unknown particles at play in this process. While those earlier results weren’t concrete enough individually, the team says they’re all pointing in the same direction, building a larger body of evidence.
“This new result offers tantalizing hints of the presence of a new fundamental particle or force that interacts differently with these different types of particles,” says Paula Alvarez Cartelle, a lead researcher on the study. “The more data we have, the stronger this result has become. This measurement is the most significant in a series of LHCb results from the past decade that all seem to line up – and could all point towards a common explanation. The results have not changed, but their uncertainties have shrunk, increasing our ability to see possible differences with the Standard Model.”
That said, there are still uncertainties involved, as the study is yet to be peer-reviewed, and the find has not yet been “confirmed.” Normally a statistical significance of five standard definitions – equivalent to around a 1 in 3.5 million chance of being a coincidence – is required to declare something a “discovery.” The new result, meanwhile, only registers three standard deviations, or about 1 in 1,000 chance of being an anomaly.
Still, the researchers are cautiously optimistic that they’re on the trail of new physics. After all, there are questions that the Standard Model can’t answer, such as dark matter or what happened to all the antimatter. Even gravity doesn’t fit in.
“The discovery of a new force in nature is the holy grail of particle physics,” says Konstantinos Petridis, an author of the study. “Our current understanding of the constituents of the universe falls remarkably short – we do not know what 95 percent of the universe is made of or why there is such a large imbalance between matter and antimatter. The discovery of a new fundamental force or particle, as hinted at by the evidence of differences in these measurements could provide the breakthrough required to start to answer these fundamental questions.”