Scientists at CERN have found evidence of an extremely rare particle decay that occurs approximately once in every 10 billion relevant decays, marking a significant development in a research effort spanning more than four decades.
The finding comes from the Large Hadron Collider’s LHCb experiment, where researchers observed evidence of a B-d meson transforming into two particles: a muon and an antimuon.
The team identified the signal by combining data collected in 2024 and 2025 with measurements from earlier experiments conducted between 2011 and 2018.
The analysis reached a statistical significance of 3.2 sigma. Although this provides evidence that the decay occurs, it remains below the five-sigma threshold generally required to confirm a discovery in particle physics.
The result is particularly important because extremely rare particle decays offer scientists a way to test the Standard Model, the framework describing fundamental particles and their interactions.
If further measurements show that the decay behaves differently from the model’s predictions, it could point towards previously unknown particles or interactions.
Researchers expect the upgraded LHCb detector to generate more data, helping them determine whether the initial evidence can be strengthened into a confirmed observation.
The finding does not directly explain how the universe originated, but further research into rare particle processes could help scientists establish whether existing theories fully describe the fundamental laws of nature.
