Discovery could reveal secrets of the ‘Zeptoverse’ - a world of extremely small distances where new particles and fundamental forces of nature may be hiding.
Large Hadron Collider - image © 2018-2026 CERN
Physicists have helped find the first evidence of an extremely rare transformation of subatomic particles at CERN’s Large Hadron Collider (LHC), in Geneva, marking a major milestone in a 42-year search.
Their breakthrough, announced by the Science and Technology Facilities Council (STFC), which funded the research, provides evidence for the rarest decay ever observed at the LHC of a short-lived subatomic particle containing a ‘beauty quark’, one of the fundamental building blocks of matter.
These particles exist for only a tiny fraction of a second before decaying into lighter particles, making them powerful tools for testing the laws of physics.
Researchers at the University of Birmingham play leading roles in the Large Hadron Collider beauty experiment (LHCb) collaboration, developing key detector technologies used by the experiment, and in the collection of the data used for this discovery.
This stunning new result is the latest of many exciting measurements at LHCb that are only possible through the exceptional commitment and talent of a large international collaboration of scientists and engineers, who designed, built and now operate the experiment and analyse the data. It is a privilege that our group in Birmingham has key roles in this scientific adventure of discovery.
The LHCb results could help physicists probe the so-called ‘Zeptoverse’ - a realm of extraordinarily small distances where undiscovered particles and forces of nature may be hiding.
The Large Hadron Collider beauty experiment (LHCb) studies particles containing beauty quarks, heavier relatives of the quarks that make up much of the visible matter in the Universe. Although produced in large numbers during high-energy collisions at the LHC, beauty particles exist for only around one and a half trillionths of a second before decaying into lighter particles.
The new measurement provides evidence for an exceptionally rare process in which a neutral beauty particle decays into two muons, heavier cousins of the electron. According to the Standard Model of particle physics - often described as the ‘rulebook’ of particle physics - this decay is expected to occur only once in every ten billion such particles.
The analysis provides researchers with powerful new ways to test the Standard Model, which explains the particles that make up matter and how they interact.
The measurements agree with the Standard Model’s predictions but push those tests to new levels of precision and into previously unexplored territory. Physicists hope that future studies of these rare decays may reveal hints of new particles or forces beyond our current understanding of nature.
Dr Niladri Sahoo, Research Fellow at the University of Birmingham and convener of the LHCb Very Rare Decays working group, said: "Reporting the first evidence from a single experiment for the extremely rare decay of a neutral B meson into two muons, while achieving the world's most precise measurements of the corresponding Bs-meson decay probability and lifetime, provides a powerful new test of the Standard Model and a window into potential new physics."
Dr Dan Johnson, Assistant Professor at the University of Birmingham and Physics Coordinator for the LHCb-UK teams, added "UK leadership has been critical to this remarkable feat, from the data analysis to construction of the ultra-precise silicon detectors upon which it relied.”
Scientists combined newly recorded data from 2024 and 2025, with data collected during earlier running periods between 2011 and 2018. Advanced machine-learning techniques and sophisticated particle-identification methods enabled researchers to isolate the rare signal from billions of particle collisions.
Professor Nigel Watson, former principal investigator for the LHCb-UK teams, said: "This stunning new result is the latest of many exciting measurements at LHCb that are only possible through the exceptional commitment and talent of a large international collaboration of scientists and engineers, who designed, built and now operate the experiment and analyse the data. It is a privilege that our group in Birmingham has key roles in this scientific adventure of discovery."
The findings come from the upgraded LHCb detector, one of the four major experiments at the LHC. Since 2024, the experiment has been collecting data at up to five times its previous rate, enabling scientists to investigate rare particle processes with unprecedented precision.
Scientists combined newly recorded data from 2024 and 2025 with data collected during earlier running periods between 2011 and 2018. Advanced machine-learning techniques and sophisticated particle-identification methods enabled researchers to isolate the rare signal from billions of particle collisions.
As the upgraded LHCb experiment continues to collect vast amounts of data, researchers plan to explore the ‘Zeptoverse’ in even greater detail - searching for clues that could help answer some of the biggest questions in modern physics, including whether undiscovered particles or forces exist beyond the Standard Model.
The experiment brought together several UK research institutions including the Universities of Birmingham, Bristol, Cambridge, Edinburgh, Glasgow, Liverpool, Manchester, Oxford, and Warwick, plus Imperial College London, and STFC Rutherford Appleton Laboratory.
For more information, please contact: Tony Moran, International Communications Manager at the University of Birmingham or +44 (0)7827 832312
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Professor of Particle Physics
Profile page for Nigel Watson, Particle Physicist and member of academic staff at the University of Birmingham.
Assistant Professor of Particle Physics
Staff profile for Dr Daniel Johnson.
