Researchers at the Large Hadron Collider beauty (LHCb) experiment at the CERN laboratory near Geneva, Switzerland, have found the first evidence of a rare decay involving the “beauty quark” particle. This discovery opens a new realm of study known as the "zeptoverse," which consists of scales as small as sextillionths of a metre.
Paula Collins and her colleagues at the LHCb experiment identified a specific process where a beauty quark is annihilated by an antiquark. This annihilation produces a pair of particles: an electron-like muon and an antimuon, which the team was able to detect. This specific process is described as exceedingly rare and has eluded experiments for decades.
“People have been searching for it for more than 40 years,” Collins said, adding that “everyone’s just over the moon.”
Team member Harry Cliff at the University of Cambridge noted that these decays are “almost impossible according to the current laws of physics,” stating that the event happens only for 1 in 10 billion beauty particles. While the finding is currently preliminary with a significance level of 3.2 sigma, Cliff noted that the chance of the signal occurring randomly is about 0.3 per cent. The gold standard for a discovery is 5 sigma.
The ability to see this event was made possible by technical upgrades to the LHCb team in recent years. Jure Zupan at the University of Cincinnati described the upgrades as a "very powerful microscope" that allows researchers to see shorter distances without "a fog in front of your eyes." Zoltan Ligeti at the Lawrence Berkeley National Laboratory called the achievement "absolutely exciting."
The measurement serves as an important test of the standard model of particle physics, which currently cannot explain dark matter or dark energy. Cristina Lazzeroni at the University of Birmingham noted that because the process is so rare, researchers would immediately spot any influence from undiscovered denizens of the zeptoverse on the decay process.
While the new measurement is consistent with the standard model, Ligeti stated this does not mean all possible new particles have been ruled out. He suggested the effects of such particles must be small but not necessarily negligible, and that the LHCb could quantify this further. Zupan added that the "promise [of future experiments]" is even more interesting than the current measurement.
However, Cliff expressed concern regarding the future of the research. He stated that the UK government withdrew funding from a planned LHCb upgrade last year, leaving the team "scrambling to figure out will we be able to continue doing this sort of research."
