CERN finds evidence of one-in-10-billion particle decay after 40 years

CERN reports evidence of rare particle decay

Physicists working with the LHCb experiment at CERN have found evidence of a particle decay predicted to occur only once in approximately 10 billion beauty particle decays, ending a search spanning more than 40 years. The result was announced during a seminar at CERN.

The decay involves a particle called Bd, which contains a beauty quark and a down antiquark, decaying into a pair of muons. Muons are similar to electrons but have greater mass. The results agree with predictions from the Standard Model, the leading theory describing fundamental particles and their interactions.

Statistical significance and what it means

In particle physics, a result must reach three standard deviations to qualify as evidence of a new phenomenon. At that level, the probability of random fluctuations producing a signal at least as statistically extreme is approximately 0.3%.

Using data collected during 2024 and 2025, the LHCb researchers identified evidence of Bd → μ+μ- at a significance of 3.0 standard deviations. When combined with earlier data gathered between 2011 and 2018, the statistical significance increased to 3.2 standard deviations, exceeding the widely accepted threshold for evidence.

The findings do not yet constitute a confirmed observation. That milestone requires a significance of five standard deviations.

"Physicists have been chasing this decay for more than forty years," said Marco Santimaria, who co-led the international analysis team of 19 scientists. "Extreme precision is required to pick the muons out of the overwhelming background."

Upgraded detector and future plans

Following a major upgrade, the LHCb experiment began collecting data in 2024 at five times the rate achieved between 2010 and 2018. The upgraded detector also became better at identifying different kinds of particles. The team combined these improvements with machine learning techniques to distinguish the exceptionally rare signals from the vast number of other particle processes.

The same investigation also produced the most precise measurements ever obtained for the related Bs → μ+μ- decay.

The High Luminosity LHC, also known as the HiLumi LHC, is scheduled to begin operating in 2030. Another major upgrade to the LHCb experiment is planned for the middle of the following decade. Together, these developments could eventually increase the experiment's data collection rate by another factor of ten.

"Seeing evidence of this rare decay is incredibly exciting, opening up new possibilities to probe beyond the direct reach of the LHC," explained Harry Cliff, LHCb's Rare Decays Convener and Analysis Co-lead.

Why it matters

• The Bd → μ+μ- decay is considered a 'golden channel' for investigating physics beyond the Standard Model.
• Rare decays can be influenced by particles too heavy to be produced directly in the Large Hadron Collider, offering indirect evidence of unknown particles.
• If future measurements reach five standard deviations, Bd → μ+μ- would become the rarest beauty particle decay ever observed.

Sources

• sciencedaily.com: After 40 years, CERN finds evidence of a one-in-10-billion particle decay | ScienceDaily
• tech.news.am: CERN obtains first compelling evidence of a particle decay that occurs once in 10 billion cases | NEWS.am TECH - Innovations and science
• yahoo.com: After 40 years, CERN finds evidence of an extraordinarily rare particle decay
• news.ssbcrack.com: CERN Physicists Achieve Major Milestone in Hunt for Rare Particle Decay - SSBCrack News

This article was drafted with AI assistance and checked against the sources above. Company claims are reported as claims. Cover image is AI-generated.