Rare B-meson decay opens a window on the zeptouniverse
Tuesday 3rd November 2026 on 14:31 in
Estonia
Physicists have observed a neutral B meson, which contains a bottom quark, decay into two muons for the first time, ERR reports. The rare process offers a new way to test the Standard Model of particle physics and search for unknown forces of nature.
An international team analysed billions of particle collisions recorded by the LHCb experiment at the Large Hadron Collider in Switzerland. B mesons are short-lived particles made of a quark and an antiquark. They exist for about 1.5 millionths of a billionth of a second before decaying into lighter particles.
The finding follows a search that began 42 years ago. According to the Standard Model, the decay occurs only once in every 10 billion particles containing a bottom, or beauty, quark. No experiment had previously produced clear evidence of the process.
The researchers combined new data collected in 2024 and 2025 with collision records from 2011 to 2018. They used machine learning and new algorithms to isolate the signal from billions of events.
Upgrades to the LHCb detector helped it record particle collisions five times more frequently than before. A silicon pixel detector, positioned five millimetres from the beams, allows researchers to pinpoint where particles form and decay into muons with sub-millimetre precision.
The result could help researchers investigate the zeptouniverse, a scale with dimensions around a billionth of a millionth of a millimetre. Physicists hope to find previously unknown particles and forces at such distances. Rare processes are especially sensitive to the effects of undiscovered physical laws.
LHCb team leader Chris Parkes said the result would help researchers gather more precise data at even smaller scales. Niladri Sahoo, a researcher at the University of Birmingham and convener of the LHCb group studying very rare processes, said the team had achieved the most precise measurements of a B meson’s lifetime and its probability of decaying into lighter particles. He said the evidence provides a strong test of the Standard Model and a basis for searching for new physical laws.