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Physicists at CERN's LHCb experiment announced evidence at a seminar of a rare particle decay expected once in about 10 billion beauty particle decays, ending a search of more than 40 years. The decay concerns the B d particle, which contains a beauty quark and a down antiquark, turning into a pair of muons, particles similar to electrons but heavier. Using data from 2024 and 2025, the team measured a significance of 3.0 standard deviations, rising to 3.2 when combined with data from 2011 to 2018. That passes the threshold for evidence but not the five standard deviations needed to confirm an observation. The results agree with Standard Model predictions. An earlier hint from a 2015 joint LHCb and CMS analysis was not confirmed by later analyses that included data through 2018. An upgraded detector collecting data at five times its earlier rate, along with machine learning, helped separate the signal from background. The 19-scientist team was co-led by Marco Santimaria. ScienceDaily reported that such decays could help reveal particles too massive to be produced directly at the Large Hadron Collider, and that future upgrades, including the High Luminosity LHC scheduled for 2030, could raise data collection tenfold.