After 42 Years of Searching, Physicists Find Evidence of a One-in-10-Billion Particle Decay

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1. 32m ago

   CERN's LHCb finds first single-experiment evidence of ultra-rare beauty meson decay

   The LHCb Collaboration at CERN announced evidence of a beauty meson decaying into two muons, a process predicted to occur roughly once in 10 billion decays. The result was presented in a seminar on November 3, 2026, and posted as a preprint on arXiv that has not yet been peer-reviewed. This marks the first single-experiment evidence for this decay channel after a search spanning more than 40 years. The upgraded LHCb detector, including UK-built components, enabled the sensitivity required to isolate the signal.

   Why it matters

   The decay of a beauty meson into two muons is a precision probe of the Standard Model because its rate is tightly predicted and highly sensitive to new particles or forces at extremely short distances, often called the zeptoverse. Previous experiments had only set upper limits or combined results to reach significance. A confirmed measurement allows physicists to test for deviations that could explain dark matter, the matter-antimatter asymmetry, or other gaps in current theory.

   What is confirmed

   • The LHCb Collaboration announced evidence of a beauty meson decaying into two muons.
   • The decay is predicted to occur roughly once in 10 billion decays.
   • The result was presented in a seminar on November 3, 2026.
   • A preprint paper has been posted on arXiv and has not yet been peer-reviewed.
   • This is the first single-experiment evidence for this decay channel.
   • The search for this decay has spanned more than 40 years.
   • The upgraded LHCb detector, including UK-built components, enabled the measurement.

   Still unconfirmed

   • The finding may offer a portal to the zeptoverse and undiscovered particles or forces.
   • The result could help explain dark matter and the matter-antimatter asymmetry.

   What to watch next

   • Peer review and publication of the arXiv preprint
   • Independent confirmation from other LHC experiments such as ATLAS or CMS
   • Updated branching ratio measurement with full Run 3 dataset
   Sources used for this update (14)

   1. Yahoo — After 42 Years of Searching, Physicists Find Evidence of a One-in-10-Billion Particle Decay
   2. BBC — The zeptoverse: what is it and how will it transform physics?
   3. New Scientist — Physicists get first glimpse of the zeptoverse from LHC experiment
   4. Phys.org — After 40 years of searching, physicists find evidence for an ultrarare particle decay
   5. University of Cambridge — Physicists knock at the door of the zeptoverse
   6. www.sciencealert.com — After 42 Years of Searching, Physicists Find Evidence of a ...
   7. theconversation.com — A chemical fingerprint in ancient rocks suggests plate tectonics began 2.5 billion years ago
   8. www.sciencedaily.com — After 40 years, CERN finds evidence of a one-in-10-billion ...
   9. www.yahoo.com — CERN’s upgraded detector finds evidence of a one-in-10 ...
   10. knowridge.com — Scientists find evidence of a one in ten billion particle decay
   11. www.euronews.com — Video. ‘Zeptoverse’: CERN scientists uncover evidence of ...
   12. www.azoquantum.com — Scientists Find Evidence of Rarest Particle Decay After 42-Years
   confidence 92%