Researchers working at CERN in Switzerland have detected a never-before-seen subatomic process that was “harder to find than the famous Higgs particle”, and it could make or break our understanding of the Universe.
By combining the results of two separate experiments at the Large Hadron Collider (LHC), the researchers were able to detect the extremely rare decay of a particle called the strange B (Bs) meson into two muons, something that the Standard Model of particle physics predicts will only occur about four times out of a billion – which is pretty much what the experiments found.
“It’s amazing that this theoretical prediction is so accurate and even more amazing that we can actually observe it at all,” one of the team, Sheldon Stone from Syracuse University in the US, said in a press release. “This is a great triumph for the LHC and both experiments.”
The findings, which have been published in Nature, came from the analysis of 2011 and 2012 data collected by the collider’s Compact Muon Solenoid (CMS) and Large Hadron Collider beauty (LHCb) experiments. Both of these study the properties of particles in order to poke holes in the Standard Model – the set of equations that we rely on to explain the behaviour and interactions of the particles in the Universe.
Although the Standard Model has dominated particle physics since the ’70s, it still doesn’t explain gravity, dark matter, or the behaviours of particles at the very beginning of the Universe, so scientists are always trying to find ways to test the limits of these equations and expand upon them.
To do this, they watch the decay of subatomic particles and compare the results with predictions from the Standard Model – any deviation could be evidence of new physics at play, such as new particles or forces that could help us understand some of the outstanding mysteries of the Universe. But so far, the predictions of the Standard Model have held up, with the discovery of the Higgs Boson being the most famous demonstration of this.
“Many theories that propose to extend the Standard Model also predict an increase in this Bs decay rate,” said Joel Butler Joel Butler, a physicist from the US’s Fermilab, who was involved in the CMS experiment. “This new result allows us to discount or severely limit the parameters of most of these theories. Any viable theory must predict a change small enough to be accommodated by the remaining uncertainty.”
However, while the Bs meson result “mostly matches” the Standard Model prediction, it deviated just enough to suggest that there may be something interesting going on that could be amplified by more data.
“It’s not way off the Standard Model prediction, but it’s low enough to keep us questioning,” said Butler. “We’ve been taking more data this spring and hope to eventually nail down the value. When we have two to four times more data from the next run of the LHC, things will start to get really interesting.”
Even more interesting is the fact that the researchers also detected evidence of the decay of another, even rarer type of B meson, known as the non-strange B meson, into two muons – something that’s predicted to occur only once out of every 10 billion decays. Again, the initial data mostly matches the predictions of the Standard Model, but with a lower confidence level.
The B mesons are fascinating to scientists because they could help explain why matter exists in the Universe at all. In theory, the Big Bang should have resulted in equal amounts of antimatter and matter, which should have annihilated each other on contact.
“Bs mesons oscillate between their matter and their antimatter counterparts, a process first discovered at Fermilab in 2006,” said Stone. “Studying the properties of B mesons will help us understand the imbalance of matter and antimatter in the Universe.”
With the LHC finally switching back on earlier this year, we’re excited to see what happens next.