{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"dd25d33b3f0f9f7016bed5a9ae78af0cae4f3ab0cbe1097ec493627296a7c812","created":"2026-10-03T07:17:53Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011","c8fb1852ecb4a0cd3bd5349236cf4d3c9cecb666980f4c0ebefc81995860a8f7"],"salt":"d3c412d894aa52c03877884547d89b0f2a536e329dc16ec2e986fd4783f9737f","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"identification","assisted_by":[],"external_id":"amo.bound-state-qed.lkb-1s3s-outlier","kind":"well-posed","literature_status":"open","n":"1","parents":[{"note":"","parent_revision":"c8fb1852ecb4a0cd3bd5349236cf4d3c9cecb666980f4c0ebefc81995860a8f7","relation":"special_case"}],"plain":"Two labs measured the same hydrogen line and extracted proton sizes that disagree by more than two standard errors. Finding why would tell which systematic effects affect such experiments.","posed_since":"2020","precise":"The LKB Paris 1S-3S measurement (Fleurbaey et al 2018) gives $r_p = 0.877(13)\\,\\mathrm{fm}$, while the MPQ Garching 1S-3S measurement (Grinin et al 2020) gives $r_p = 0.8482(38)\\,\\mathrm{fm}$. Identify the systematic shift (second-order Doppler, quantum interference of neighboring lines, light shift, pressure shift) responsible for the difference of about 6 kHz (2.1 combined sigma) in the 1S-3S transition frequency.","problem_ref":null,"references":"","settled_by":"A remeasurement of 1S-3S in the LKB apparatus with a revised line-shape model that agrees with the Garching value, or a third 1S-3S measurement.","status_note":"","title":"Why two 1S-3S hydrogen measurements give different proton radii","topic_ref":"49408e9491357ca694b4e9c3017e230cf2b78342f17900bd6e9221b8961376f4"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"8967342943b1c4065d7adb4e4446d808a72b1060ceb1b4c9e565fb7e38537a93","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"a379ee7e50006487c5350bec2752b62302e4090561798ed07853a606cfc118ae","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"RgBCeInNSVAuWvD3z1LMdQyOFTqZOzH-XrH9yBBAJ2Z3_I2KYL6557J1CYDncYkAHh1WvsXMAOw8jqhLy8OGAg"},"schema":"pubphys.envelope/1"},"record_hash":"8967342943b1c4065d7adb4e4446d808a72b1060ceb1b4c9e565fb7e38537a93","leaf_index":377}