{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"d88ade190a78b0fe73d084f0252e42f9e5ec09dfb91bebb0380e5bf41b324a0b","created":"2026-10-03T07:18:07Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011","84ce1c7bc46a6b9febd203bba7fde4af888b1a1871f94c4879fdfe4060d3970b"],"salt":"8dc46b4c96f40aa3267c35240bae00428ba42a2ae51ac3a25182370c99ff0894","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"yes-no","assisted_by":[],"external_id":"nuc.precision-anomalies.x17-boson-search","kind":"well-posed","literature_status":"contested","n":"1","parents":[{"note":"","parent_revision":"84ce1c7bc46a6b9febd203bba7fde4af888b1a1871f94c4879fdfe4060d3970b","relation":"special_case"}],"plain":"If the X17 particle exists, it should also appear when positrons hit electrons at just the right energy. Dedicated experiments are scanning this energy.","posed_since":"2016","precise":"Test for a vector or axial-vector boson with $m_X = 16.5 \\text{ to } 17.2\\,\\mathrm{MeV}$ and electron coupling $\\epsilon$ of roughly $2e-4 \\text{ to } 1.4e-3$ through resonant $e+ e- \\to X \\to e+ e-$ production (PADME), electron beam-dump and pair-spectrometer experiments. Answer: discovery, or exclusion at 90 percent confidence of the full coupling range implied by the ATOMKI 8Be and 4He rates.","problem_ref":null,"references":"","settled_by":"A further PADME run at higher statistics and an independent resonant-production or beam-dump experiment covering the full coupling range.","status_note":"PADME (arXiv 2505.24797, 2025) found an excess near 16.90 MeV with a global significance of about 2 standard deviations; no follow-up result had been published, to our knowledge, as of mid-2026.","title":"Existence of a 17 MeV boson coupled to electrons","topic_ref":"68930a0e96cfb6023c51ad2da3d1ea500482dc0e5e690cd3ea4398d0ad9ecbec"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"054b71499eff153a847d31139e97bb5a0e4e13efb05917c9e497d675261ebd38","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"d390b34924fe47c4eaa201518404ed5129468e12e58303087a9a726635962dde","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"Z6fpQhASOtT9Vh-4Kuer_VFDUaKhuvYmXlEdOF2kOlXQBPofVPtPpRqrQUyu0mjdxrFKZez0jiUaPvAMMb-BDQ"},"schema":"pubphys.envelope/1"},"record_hash":"054b71499eff153a847d31139e97bb5a0e4e13efb05917c9e497d675261ebd38","leaf_index":1789}