LHCb experiment reports first evidence of ultra-rare beauty-quark decay
Scientists at CERN's LHCb collaboration have observed evidence for the decay of a beauty meson into two muons, a process predicted to occur once in about 10 billion cases, marking a step toward more precise tests of the Standard Model.
The upgraded LHCb detector at CERN's Large Hadron Collider has recorded evidence of the extremely rare decay of a beauty meson into two muons, a process expected to happen roughly once in every 10 billion beauty particles. The measurement reached a statistical significance of 3.2 sigma, which physicists consider the first evidence, though additional data will be needed to achieve the five-sigma level required for a formal discovery.
The result follows more than four decades of searches for this decay, known as \"Bd → μμ\", and aligns with predictions of the Standard Model. By studying such rare decays, researchers aim to detect subtle influences of yet-unknown particles or forces that could appear at distances on the order of a zeptometer (10⁻²¹ m).
Professor Chris Parkes, head of the Department of Physics and Astronomy at The University of Manchester and leader of the LHCb collaboration, highlighted the scale of the upgrade, noting that the project involved a 15-year design and construction effort by a 1,900-member international team. He said the United Kingdom made the largest national contribution, developing new silicon-pixel detector technology that enabled the new measurement.
Dr. Stefano De Capua, who oversaw the construction of the detector components at Manchester, added that nearly 90 UK companies participated in building the Vertex Locator, a silicon pixel detector positioned just five millimetres from the LHC beams to track particle trajectories with high precision.
Professor Conor Fitzpatrick, deputy physics coordinator for LHCb, described the observation as a "golden channel" for probing physics beyond the current model and expressed optimism about future discoveries as larger data sets are collected in the early 2030s.
The collaboration plans further upgrades that could increase data-collection rates by up to tenfold, enhancing sensitivity to potential new phenomena at even smaller scales.
Professor Brian Cox, a particle physicist at the University of Manchester not involved in the study, called the result an important example of scientific progress, emphasizing that improved instrumentation allows nature to be examined in greater detail.