{"schema":"pubphys.bundle/1","record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"acc5088fa3612d01709c9bb60ccf73473250770cdf7a494cac047253cac608e3","created":"2026-10-03T07:18:07Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"0ab634168d44a648e32939d1cabfa2edf00eacc112717c4b2d4a46c665f33839","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"identification","assisted_by":[],"external_id":"nuc.precision-anomalies.beam-bottle-discrepancy","kind":"phenomenon","literature_status":"open","n":"1","parents":[],"plain":"Trapping ultracold neutrons in a bottle and counting survivors gives 877.8 seconds; counting decay protons from a neutron beam gives 887.7 seconds. The gap of about 4 standard deviations has no accepted explanation.","posed_since":"2005","precise":"Bottle (storage) measurements give $\\tau_n = 877.82 \\pm 0.22\\,(\\mathrm{stat}) +0.20/-0.17\\,(\\mathrm{sys})\\,\\mathrm{s}$ (UCNtau, arXiv 2409.05560, 2024); proton-counting beam measurements give $887.7 \\pm 1.2\\,(\\mathrm{stat}) \\pm 1.9\\,(\\mathrm{sys})\\,\\mathrm{s}$ (NIST, 2013). Identify the cause: an unaccounted systematic in either method (proton detection or neutron-flux calibration in beams, unrecognized loss channels in bottles) or a non-standard decay channel. Answer: the identified effect, demonstrated by measurements that bring the methods into agreement or confirm the gap at higher precision.","problem_ref":null,"references":"","settled_by":"A next-generation proton-counting beam measurement (BL3) with sub-second uncertainty, plus independent electron-counting and space-based measurements.","status_note":"A J-PARC beam measurement counting decay electrons gave 877.2 +/- 1.7 (stat) +4.0/-3.6 (sys) s (arXiv 2412.19519, 2024), consistent with bottles and 2.3 standard deviations from the proton-counting beam average.","title":"Why beam and bottle neutron lifetimes 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