{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"337eb8760185e7ec3d6fc210380d819080178d0ce31b7187063b31104bb66188","created":"2026-10-03T07:18:05Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011","7bf08dc0cbbc6d712f88659419fa7f025240cebcdba676af431a6ddfada7c88e"],"salt":"5b4843f85b0a83fdc75d0564843786808e60cb4b7abff723f4487e8770cda9e1","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"identification","assisted_by":[],"external_id":"hep.electroweak-anomalies.hvp-ee-tension","kind":"well-posed","literature_status":"open","n":"1","parents":[{"note":"","parent_revision":"7bf08dc0cbbc6d712f88659419fa7f025240cebcdba676af431a6ddfada7c88e","relation":"special_case"}],"plain":"Measurements of how often electron-positron collisions make two pions disagree between experiments, and with supercomputer calculations. This number feeds the muon magnet prediction.","posed_since":"2023","precise":"Identify the cause of the disagreement among $\\sigma(e+e- \\to \\pi+ \\pi-)$ measurements near the $\\rho$ peak (CMD-3 2023 versus KLOE, BaBar, SND) and between data-driven and lattice a_mu^HVP,LO (difference $\\sim 2\\ \\text{to}\\ 3\\ \\text{percent}$ of HVP). An answer locates the systematic error, the radiative-correction issue, or a physical effect responsible.","problem_ref":null,"references":"","settled_by":"New $\\pi\\,\\pi$ measurements (BaBar reanalysis, Belle II, BESIII, KLOE reanalysis, CMD-3 crosscheck) together with lattice windows and $\\tau$-decay data with isospin-breaking corrections.","status_note":"Unresolved as of 2025; the 2025 White Paper did not use data-driven HVP for its central value.","title":"Why do e+e- to pi+ pi- cross-section measurements disagree?","topic_ref":"5f9fc18424455249bb593d2fc721c3bb60bebc1408b04e516877a25482ca82d2"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"be76ede68a3c85b032fb07d9c72ee16d12f04b07e28ff0c7d35c0b0a431114c5","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"ccfd7b5206b4a263078d5ad5bb020a2d3d29a640bd916a15529a6c8d9d4e7e73","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"7Omr6qTd43HJAGuKM3XxUUAC0m3nvirZlqwRhjPUuvrq_BjiSf8KGLHJI63Hcqq4vdxOPbo8wukX7kwpVTS4DA"},"schema":"pubphys.envelope/1"},"record_hash":"be76ede68a3c85b032fb07d9c72ee16d12f04b07e28ff0c7d35c0b0a431114c5","leaf_index":1534}