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The LHCb Four-Sigma Holds As The 8.4-fb Paper Anchors The Anomaly Through Run Three

LHCb-PAPER-2025-041 — the comprehensive analysis of the B⁰ → K*⁰μ⁺μ⁻ decay at 8.4 inverse femtobarns of integrated luminosity, posted to the CERN Document Server in January and on arXiv as 2512.18053 — continues to anchor the four-sigma anomaly against Standard-Model predictions through the May 8 reading. [1] The CP-averaged angular observables and the branching fraction "continue to exhibit the pattern of tensions" seen in earlier subsets; the CP-asymmetry observables show no significant deviation from zero. [1] Yesterday's paper read the 8.4-fb paper as the field marking its institutional clock against the political one and the discovery threshold sitting in the mid-2030s under HL-LHC and LHCb Upgrade II. Run 3, scheduled through end-2026, has now cleared roughly three times the 2018 dataset; the next analysis to update the result will require both the Run 3 statistics and improved lattice-QCD calculations of the charming-penguin contribution that has bottlenecked the field for a decade. [2] The five-sigma threshold the field treats as discovery has not been crossed; the apparatus required to cross it is still being built.

-- KENJI NAKAMURA, Tokyo

Sources & X Posts

News Sources
[1] https://cds.cern.ch/record/2951844
[2] https://eprints.gla.ac.uk/309224/1/309224.pdf
X Posts
[3] Test of lepton universality in beauty quark decays. The Standard Model predicts identical electroweak interaction strengths for electron, muon and tau. https://x.com/LHCbPhysics/status/1374271744136118273

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