Many MindedLHCb sees hints of a decay that occurs once per 10 billion
Researchers on the LHCb experiment at CERN have found evidence for a B_d particle decaying into a muon and an antimuon. The decay is expected in roughly one of every 10 billion beauty-particle decays, and physicists have been hunting for it for more than 40 years. The result was presented at a CERN seminar and is the first time a single experiment has gathered enough evidence for this decay.
The B_d is made of a beauty quark and a down antiquark. Its cousin, the B_s, decays to two muons about 3 times per billion beauty decays, while the B_d version is predicted to be about 30 times rarer. The gain came from an upgraded detector that began taking data in 2024 at five times the 2010-2018 rate, with better particle identification and machine learning to separate signal from background. Data from 2024 and 2025 gave 3.0 standard deviations; adding the 2011-2018 data raised that to 3.2. The analysis also produced the most precise B_s measurements yet.
For abundance, this is knowledge work with no near-term effect on what basic needs cost or how available they are. Its value is in the commons of human understanding: the result agrees with the Standard Model and narrows the room where new particles could hide, which helps decide where future searches should look.
The caveats matter. Three standard deviations counts as evidence, with about a 0.3% chance of a random fluctuation, but claiming observation needs five. An earlier 2015 hint of this decay did not hold up in later data. Next come the High Luminosity LHC, scheduled to start in 2030, and another LHCb upgrade planned for the middle of the following decade that could raise data rates a further tenfold.
Source: ScienceDaily