Unexpected Particle Decay Could Suggest New Fundamental Force
By Mike Howie
In March of 2021, a team of researchers colliding particles in the Large Hadron Collider at CERN under the border between France and Switzerland witnessed an event that could change physics as we know it.
The researchers were studying particles known as bottom or beauty quarks, one of the fundamental building blocks of matter according to the Standard Model of particle physics. They should decay into muons and electrons at the same rate after collision. Instead, something strange happened: the particles decayed into about 85 muons for every 100 electrons.
This suggests that there could be a fundamental force in physics that has yet to be identified.
The Standard Model
The Standard Model of particle physics is our best understanding of just about everything in the universe. It posits that all matter — stars, planets, people, even the paper or device you’re reading this on — is made of two fundamental particles governed by four fundamental forces.
The two fundamental particles are quarks and leptons, both of which are divided into three pairs of particles. Quarks have the up quark and down quark, charm quark and strange quark, and the top quark and bottom (or beauty) quark. Leptons have the electron and electron neutrino, muon and muon neutrino, and tau and tau neutrino.
The four forces are known as the strong force, the weak force, the electromagnetic force, and the gravitational force. Gravity is the weakest of these forces, and while it’s identified by the Standard Model, it’s not accounted for. So far, physicists have been unable to make it fit comfortably within the model.
While the Standard Model is indeed remarkable, it’s not perfect. There are still facets of the universe that it fails to explain, like what dark matter really is and what happened to antimatter after the big bang.
However, the mysterious force witnessed at CERN could be one small step toward a more complete understanding of what makes the universe tick.
Measured Excitement
The researchers involved in the study hesitate to say that they’ve made a discovery. There’s about a one in 1,000 chance that their results could be a statistical fluke, which is far from the one in 3.5 million chance that’s the conventional threshold in physics for a discovery. But they’re still celebrating.
“That’s a small enough number to get us usually hyper-skeptical physicists at least cautiously excited,” said Dr. Mitesh Patel of Imperial College London in England. “I wouldn’t say effusive but as excited as us physicists get.”
According to CERN, there’s about a 0.1 percent probability that the findings are compatible with what the Standard Model predicts. That means that if the findings are accurate — if particles really do behave in the way they appeared to in the experiment — then there must be some as yet unknown particle or force involved.
However, the findings are consistent with some other experiments conducted over the past decade, and there are related studies underway that could help verify the results.
The detector is scheduled for an upgrade in 2022, and then Dr. Patel and his team will be back to work, potentially uncovering the mysteries of the universe.