CERN LHCb Finds First Evidence After 40-Year Search for Rare Decay Occurring Once in About 10 Billion Beauty Particles, at 3.2 Sigma
Physicists at CERN have detected the first evidence, after more than 40 years of searching, of an extraordinarily rare particle decay predicted to occur only about once in every 10 billion beauty particles. The signal was recorded by the upgraded LHCb experiment at CERN's Large Hadron Collider.
In the decay, known as Bd to mu mu, a particle containing a beauty quark transforms into two muons, particles similar to electrons but heavier. The signal has a statistical significance of 3.2 sigma, strong enough to qualify as evidence of the decay, although more data will be needed to reach the five-sigma threshold required to claim a discovery in particle physics. Professor Chris Parkes, head of the Department of Physics and Astronomy at the University of Manchester, led the international LHCb collaboration through construction of the upgrade and led approval of the new result.
The new measurement matches the predictions of the Standard Model, the researchers said. The upgraded LHCb Vertex Locator, a silicon pixel detector built with leading UK involvement, sits just five millimetres, or about 0.2 inches, from the LHC beams. By collecting data at up to five times its previous rate, the upgraded experiment is expected to build a much larger dataset into the early 2030s, and a further planned upgrade could increase that rate by another factor of ten.
Source: CERN
Published by GSM · USA (original Chinese edition)
Photo: 图中是 CERN LHCb 实验的外径迹探测器部件，该实验记录了此次罕见衰变信号。来源：Wikimedia Commons, File:LHCb's outer tracker goes to GSI's PANDA experiment 02.jpg, Traczyk, Piotr, CC BY 4.0。
