Detecting an Extremely Rare Particle Decay
Physicists at CERN have found evidence of a particle decay expected to occur only once in approximately 10 billion beauty particle decays, a result 40 years in the making, Science Daily reported.
The discovery focuses on a particle known as Bd, which contains a beauty quark and a down antiquark. Researchers working with the LHCb experiment detected evidence that this particle can decay into a pair of muons, which are heavier relatives of the electron.
ScienceAlert noted that the finding was announced in a seminar held on November 3rd and detailed in a preprint paper on arXiv. The odds of this decay occurring are substantially less likely than winning the lottery.
The Debrief reported that Professor Chris Parkes of the University of Manchester called the upgraded LHCb a 15-year design and construction project involving a 1,900-member international collaboration. The international analysis team was co-led by Marco Santimaria.
Upgraded Detectors and Machine Learning Increase Data Collection Rates
A major upgrade to the LHCb experiment allowed researchers to begin collecting data in 2024 at five times the rate achieved between 2010 and 2018, according to Science Daily. The upgraded detector also improved in identifying different kinds of particles.
ScienceAlert reported that the experiment used machine learning techniques to increase the signal-to-noise ratio. Without these advances, the rare signals would have been overwhelmed by background particle processes.
Marco Santimaria stated that extreme precision is required to pick the muons out of the overwhelming background, as reported by Science Daily. Researchers combined new data collected in 2024 and 2025 with data from earlier runs between 2011 and 2018.
LHCb Researchers Identify Evidence of Bd Decay at 3.2 Sigma
To claim evidence of a new phenomenon, a result must reach three standard deviations, or sigma, corresponding to a 0.3 percent chance that the signal occurred randomly, CERN reported. The LHCb researchers identified evidence of the Bd decay at 3.0 standard deviations using 2024 and 2025 data.
When combined with earlier data gathered between 2011 and 2018, the statistical significance increased to 3.2 standard deviations, exceeding the threshold for evidence, Science Daily reported. UKRI noted that this remains below the five-sigma level, which is the gold standard for claiming a formal discovery in particle physics.
The investigation also produced precise measurements for a related decay involving a beauty quark, known as Bs to mu. Back in 2015, the CMS and LHCb collaborations published a joint analysis showing the first definitive detection of Bs to mu alongside initial hints of the much scarcer Bd decay, though later evaluations taking in records up through 2018 failed to validate those initial signs.
Probing the Zeptoverse for New Physics
The results agree with predictions from the Standard Model of particle physics while narrowing the possibilities for new particles beyond it, Science Daily reported. UKRI added that the findings provide clues about what new forces or particles might be hiding in the zeptoverse, a realm of extremely small distances around a billionth of a trillionth of a meter.
After 40 Years of Searching, CERN Finds Evidence of a Particle Decay That Happens Just Once in 10 Billion Times! Imagine searching for something so rare that it happens only once in 10 billion particle decays. Now, scientists at CERN have finally found evidence of it. Using the… pic.twitter.com/qDB5KLwtQB
Harry Cliff, LHCb’s Rare Decays Convener and Analysis Co-lead, stated that seeing evidence of this rare decay opens up new possibilities to probe beyond the direct reach of the LHC, as reported by Science Daily. ScienceAlert quoted Cliff stating that researchers are knocking on the door of the zeptoverse.
“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.
Professor Brian Cox, who was not involved in the CERN experiment, told The Debrief that equipment upgrades allow researchers to see the world in far greater detail. Cox noted that progress can be incremental or genuinely world-changing.
Future Large Hadron Collider Upgrades
The High Luminosity LHC, also known as the HiLumi LHC, is scheduled to begin operating in 2030, according to Science Daily. According to CERN statements, this launch, paired with a scheduled overhaul of the LHCb instrument slated for the mid-2030s, holds the potential to boost data collection speeds by another decimal factor.
[Press Update]: LHCb finds evidence of one-in-ten-billion particle decay Find out more: https://t.co/5lsVESALnG pic.twitter.com/8Zwfu2qVrW
Collecting larger datasets will allow physicists to detect more of these rare decays and measure their properties with greater precision. Harry Cliff explained that future upgrades will provide even greater sensitivity to undiscovered particles.
