Overview
- LHCb announced on Thursday, November 5, 2026 that combined data yield a 3.2 standard‑deviation signal for the neutral B‑meson decay Bd→μμ, the first time one experiment has produced such evidence.
- The decay produces two muons and is expected by the Standard Model to occur about once in ten billion B‑meson decays, and the measured rate so far matches that prediction.
- The signal was extracted thanks to a 2024 LHCb detector upgrade that increased data capture roughly fivefold and to machine‑learning methods that better separate signal from background.
- Scientists caution that 3.2σ is evidence rather than a confirmed discovery because particle physics requires a 5σ threshold to rule out a chance fluctuation.
- Planned steps to reach 5σ include continued data taking, further LHCb improvements and the High‑Luminosity LHC expected to raise collision rates from about 2030, which would give teams the larger datasets needed to confirm or refute subtle deviations from the Standard Model.