🚀 Science
LHCb at CERN finds first single-experiment evidence of a decay that happens about once in ten billion
In 60 seconds: Physicists at the LHCb experiment at CERN's Large Hadron Collider have found the first evidence from a single experiment of a very rare decay in which a neutral B meson turns into two muons. The Standard Model predicts this should happen to about one in every ten billion such particles. So far the result agrees with the theory. The team used new 2024 and 2025 data with older runs from 2011 to 2018.
Why it matters
Very rare decays are a sensitive test of physics. If the rate ever differs from the Standard Model, it could point to new particles or forces that no one has seen yet.
Explain it simply
Imagine listening for one particular raindrop landing on a tin roof in a storm of ten billion drops. The detector found that one.
The 3-minute read
What happened
LHCb reported the first evidence from one experiment of a neutral B meson decaying into two muons, the rarest decay of a short-lived beauty-quark particle ever seen at the LHC, the university said.
Background
The Standard Model is physicists' best account of known particles and forces. LHCb is built to study particles with a beauty quark, hunting for tiny departures from the model. The work was funded by the UK's Science and Technology Facilities Council.
How it works
The team combined data from 2011 to 2018 with new 2024 and 2025 data, and used machine learning and particle-identification methods to pick the faint signal out of a huge background.
What's next
The upgraded detector keeps collecting data, so the measurement will sharpen. Researchers want to explore the tiny-distance 'Zeptoverse' and test whether undiscovered particles or forces exist beyond the Standard Model.
What it means for you
Remember the difference: 'evidence' is a weaker claim than 'observation' or 'discovery' in particle physics. CERN, the LHC and the Standard Model are common general-science questions.
Key numbers
- 1 in 10 billion: How often the Standard Model predicts this decay
- 5x: Data rate of the upgraded detector, at most, versus before 2024
- 2011–2018 + 2024–25: Data periods combined in the analysis
Both sides
- LHCb physicists: This is a powerful new test of the Standard Model and a window into possible new physics.
- Sceptics: The result matches the Standard Model so far, so no new physics has been shown; it is still only evidence.
Key terms explained
- Muon
- A heavier cousin of the electron: a tiny charged particle that lives for only a few millionths of a second.
- Standard Model
- Physicists' tested theory of the known building blocks of matter and the forces between them, apart from gravity.
The story so far
- 2011–2018: LHCb collects the first big batch of proton collision data at the Large Hadron Collider. The new analysis combines this earlier data with newer runs, so that a decay seen only about once in ten billion can be spotted.
- 2024–2025: The upgraded LHCb detector records data at up to five times its earlier rate. Newly recorded 2024 and 2025 data, together with machine-learning methods to identify particles, made the signal stand out.
- 3 Nov 2026: Physicists announce first evidence from a single experiment of a neutral B meson decaying into two muons. The result matches the Standard Model's prediction so far, but it tests the theory more precisely than before.
- Today: CERN's LHCb finds evidence of a one-in-ten-billion particle decay
Exam notes (UPSC, SSC, Banking, PSC)
- LHCb (Large Hadron Collider beauty) is one of the main experiments at CERN's Large Hadron Collider near Geneva.
- A muon is a heavier cousin of the electron; a B meson is a short-lived particle containing a beauty quark.
- The Standard Model describes known elementary particles and three of the four forces; it does not include gravity.
- India is an associate member of CERN (since January 2017) and Indian institutes take part in LHC experiments.
Likely exam question: What is the Standard Model of particle physics, and why do physicists study very rare decays to look beyond it?