# CERN Physicists Detect Rare Particle Decay Predicted by Standard Model LHCb collaboration confirms ultra-rare B0 meson decay after four decades of scientific research. - **Source:** [Sci.News: Breaking Science News](https://www.sci.news/) - **Published:** 2026-11-03 - **Topic:** [Business](https://brifing.si/c/business) - **Original article:** - **On Brifing:** https://brifing.si/s/282f55f4-220a-40c5-a0b8-d0b9af84ae0e ## Historic Particle Decay Discovery Physicists at the LHCb Collaboration have finally observed the extremely rare decay of the B0 meson into two muons. This specific process, pursued by researchers for over four decades, aligns with the theoretical predictions of the Standard Model. The discovery marks a significant milestone in fundamental physics research conducted at CERN. ## Statistical Significance and Data The team reported an excess of events with a statistical significance of 3.0 standard deviations in their latest paper. When combined with previous LHCb experiment data, the significance increases to 3.2 standard deviations. This rigorous analysis confirms the occurrence of a process that happens only once in every ten billion particles. ## Measuring the Branching Fraction Researchers measured the branching fraction of the B0 meson decay at approximately 1.26 in 10 billion using new data. The Standard Model prediction stands at 1.03 in 10 billion, while the combined result reaches 1.14 in 10 billion. These precise measurements highlight the extreme difficulty of isolating muons from overwhelming background noise. ## Sibling Process Analysis The team also analyzed the decay of the heavier B0s meson into two muons, a more frequent but still rare event. They determined a branching fraction of 3.31 in a billion, compared to the Standard Model prediction of 3.66 in a billion. This represents the most precise determination of this process to date. ## Effective Lifetime Measurements Beyond branching fractions, the researchers measured the B0s meson’s effective lifetime during this decay process. The result is 1.42 picoseconds with a statistical uncertainty of 0.18, rising to 1.60 picoseconds when combined with earlier data. Such measurements are critical for revealing potential contributions from new physics beyond our current fundamental understanding. ## Evolution of LHCb Experiment The LHCb project, which began in 1995, continues to demonstrate increased sensitivity in probing nature at the most fundamental level. Professor Guy Wilkinson noted that this announcement ushers in a new era of discovery. The collaboration remains focused on exploring the Zeptoverse to identify potential deviations from established physical laws. ## Technical Challenges in Detection Identifying these decays requires extreme precision to distinguish muons from the massive background generated within the collider. Dr. Marco Santimaria emphasized that the forty-year pursuit was driven by the need for such high-resolution capabilities. The current success showcases the extraordinary technical evolution of the LHCb experiment since its inception decades ago. ## Implications for Future Physics This result validates the Standard Model while providing a platform for future investigations into unknown phenomena. By successfully measuring these rare decays, the team has proven the capability of the LHCb to probe nature at deeper levels. Researchers now look forward to exploring further, seeking insights that lie beyond current scientific frameworks. ## Sources covering this story - https://www.sci.news/physics/cern-ultra-rare-particle-decay-15171.html — --- _Summary written by Brifing from the original reporting. Copyright in the original article belongs to its publisher; read the full piece at the link above._