{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"fe1d34e681d68ce67c22d84590e684ecb74c0cb2dea37f9b8276d12a8ddb4afe","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["054b71499eff153a847d31139e97bb5a0e4e13efb05917c9e497d675261ebd38","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"66cb1a9fcc0f73308eee86d7383a5bfe2f20ade0c6b80109263ef331f1c58882","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":"2","parents":[],"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 $2 \\times 10^{-4} \\text{ to } 1.4 \\times 10^{-3}$ 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":"054b71499eff153a847d31139e97bb5a0e4e13efb05917c9e497d675261ebd38","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":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"a47721ac1939d18a1c07883a61dd8ad9f7a6907da6397913bbab804f011ea5a5","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"099affbf2f80c98b278bc1db71f061e1ca40af91aea636f3d332e00f8ef74ed4","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"GwGRdqJ0pnQ5JWhLagwlbDxuwWF7pqRqorPhIH3s_GPAN4KnBhQaM40u45X3WV8u6kAF6G4aOHQbrGG37eroAQ"},"schema":"pubphys.envelope/1"},"record_hash":"a47721ac1939d18a1c07883a61dd8ad9f7a6907da6397913bbab804f011ea5a5","leaf_index":3518}